Modulation of autophagy by sorafenib: effects on treatment response

REVIEW published: 08 June 2016 doi: 10.3389/ pha .2016.00151 F on ie s in Pha macology | www. on ie sin.o g 1June 2016 | Volume 7 | A icle 151 Edi ed by: F ancois X. Cla e , The Uni e si y o Texas MD Ande son Cance Cen e , USA Re iewed by: Amedeo Columbano, Uni e si y o Caglia i, I aly Nelson Shu-Sang Yee, Penn S a e Mil on S. He shey Medical Cen e , USA Jae-Sung Kim, Uni e si y o Flo ida, USA *Co espondence: José L. Mau iz [email p o ec ed] Special y sec ion: This a icle was submi ed o Cance Molecula Ta ge s and The apeu ics, a sec ion o he jou nal F on ie s in Pha macology Recei ed: 14 Ma ch 2016 Accep ed: 26 May 2016 Published: 08 June 2016 Ci a ion: P ie o-Domínguez N, O dóñez R, Fe nández A, Ga cía-Palomo A, Mun ané J, González-Gallego J and Mau iz JL (2016) Modula ion o Au ophagy by So a enib: E ec s on T ea men Response. F on . Pha macol. 7:151. doi: 10.3389/ pha .2016.00151 Modula ion o Au ophagy by So a enib: E ec s on T ea men Response Nes o P ie o-Domínguez1, 2, Raquel O dóñez1, 2, Anna Fe nández1, 2, And es Ga cía-Palomo3, Jo di Mun ané1, 4, Ja ie González-Gallego1, 2 and José L. Mau iz1, 2* 1Cen o de In es igación Biomédica en Red de En e medades Hepá icas y Diges i as (CIBERehd), León, Spain, 2Ins i u e o Biomedicine (IBIOMED), Uni e si y o León, León, Spain, 3Se ice o Clinical Oncology, Complejo Asis encial Uni e si a io de León (Hospi al o León), León, Spain, 4Depa men o Gene al Su ge y, “Vi gen del Rocío”-“Vi gen Maca ena” Uni e si y Hospi al/IBiS/CSIC/Uni e sidad de Se illa, Spain The mul ikinase inhibi o so a enib is, a p esen , he only d ug app o ed o he ea men o hepa ocellula ca cinoma (HCC), one o he mos le hal ypes o cance wo ldwide. Howe e , he inc ease in he numbe o so a enib umo esis an cells educes e iciency. A be e knowledge o he in acellula mechanism o he d ug leading o educed cell su i al could help o imp o e he bene i s o so a enib he apy. Au ophagy is a bulk cellula deg ada ion p ocess ac i a ed in a b oad ange o s ess si ua ions, which allows cells o deg ade mis olded p o eins o dys unc ional o ganelles. This cellula ou e can induce su i al o dea h, depending on cell s a us and media signals. So a enib, alone o in combina ion wi h o he d ugs is able o induce au ophagy, bu cell esponse o he d ug depends on he complex in eg a i e c oss alk o di e en in acellula signals. In cance ous cells, au ophagy can be egula ed by di e en cellula pa hways (Ak - ela ed mammalian a ge o apamycin (mTOR) inhibi ion, 5′AMP-ac i a ed p o ein kinase (AMPK) induc ion, dissocia ion o B-cell lymphoma 2 (Bcl-2) amily p o eins om Beclin- 1), o e ec s o some miRNAs. Inhibi ion o mTOR signaling by so a enib and diminished in e ac ion be ween Beclin-1 and myeloid cell leukemia 1 (Mcl-1) ha e been ela ed o induc ion o au ophagy in HCC. Fu he mo e, changes in some miRNAs, such as miR-30α, a e able o modula e au ophagy and modi y sensi i i y in so a enib- esis an cells. Howe e , al hough AMPK phospho yla ion by so a enib seems o play a ole in he an ip oli e a i e ac ion o he d ug, i does no ela e wi h modula ion o au ophagy. In his e iew, we p esen an upda ed o e iew o he e ec s o so a enib on au ophagy and i s ela ed ac i a ion pa hways, analyzing in de ail he in ol emen o au ophagy on so a enib sensi i i y and esis ance. Keywo ds: so a enib, au ophagy, hepa ocellula ca cinoma, cance he apeu ic, dug esis ance INTRODUCTION Hepa ocellula ca cinoma (HCC) is he mos common ype o li e cance and he second mos equen cause o cance - ela ed dea h wo ldwide (Fe lay e al., 2015; To e e al., 2015). The s aging and ecommended ea men o pa ien s wi h HCC is ela ed o he li e unc ion, size and numbe o nodules, gene al s a us o he pa ien , ascula in asion, and he p esence o ex ahepa ic P ie o-Domínguez e al. So a enib and Au ophagy me as asis. Cu a i e ea men s such as su gical esec ion, li e ansplan a ion, and adio equency abla ion may be use ul in he ea ly s ages o he disease. Howe e , only pallia i e ea men s a e a ailable in ad anced s ages, in which di e en chemo he apeu ics ha e been assayed wi h a iable e ec i eness (Rossi e al., 2010; Fo ne e al., 2012). The de elopmen o new diagnos ic me hods which can de ec small li e umo s is essen ial o allow mo e agg essi e in e en ions and o imp o e pa ien su i al a es (Gonzalez, 2014). So a enib (BAY 43-9006, Nexa a R ), which was de eloped in 1995 (Gau hie and Ho, 2013), is he only chemo he apeu ic d ug which has demons a ed o imp o e su i al a e in pa ien s wi h HCC (Llo e e al., 2008; Abdel-Rahman and Fouad, 2014). Recen s udies ha e also p o en ha so a enib has he apeu ic e ec s in o he cance ypes, such as hy oid cance , acu e myeloid leukemia, ad anced enal cell ca cinoma o p os a e cance (Escudie e al., 2007; Gollob e al., 2007; Chi e al., 2008; An a e al., 2014; Luo e al., 2014; Alonso- Go doa e al., 2015; Yamamo o e al., 2015). So a enib a ge s he RAF se ine/ h eonine kinases, a amily o h ee membe s (A-RAF, B-RAF, and C-RAF/Ra -1) ha play a key ole in he ansduc ion o mi ogenic and oncogenic signals h ough he Ra /Mi ogen-ac i a ed p o ein (MAP)/ex acellula signal- egula ed kinase (ERK) kinase (MEK)/ERK signaling pa hway, esul ing in a lowe cyclin D1 exp ession and in cell cycle a es (Wellb ock e al., 2004; Adnane e al., 2006; Liu e al., 2006). So a enib also po en ly inhibi s y osine kinase ecep o s such as ascula endo helial g ow h ac o ecep o (VEGFR) 2, VEGFR 3, pla ele -de i ed g ow h ac o ecep o -β(PDGFR- β), Fl 3, and c-Ki , which p omo e angiogenesis (Wilhelm e al., 2004, 2008; Ce ello e al., 2012). The ep ession blocks a b oad spec um o di e en p ocesses in ol ed in p oli e a ion, angiogenesis o apop osis, causing a educ ion in blood essel a ea in he umo and s a ing cance ous cells (E be e al., 2004; Gau hie and Ho, 2013). Fu he mo e, so a enib enhances TRAIL-induced cell dea h h ough SH2 domain- con aining y osine phospha ase (SHP-1)-dependen educ ion o signal ansduce s and ac i a o s o ansc ip ion ype 3 (STAT3) phospho yla ion (Ty 705STAT3) and ela ed p o eins Mcl-1 (myeloid cell leukemia 1), su i in, and cyclin D1 in hepa oma cells (Chen e al., 2010). So a enib is also able o ep ess Mcl-1 ac i i y h ough a MAPK-independen mechanism, which inc eases he apop osis in insic pa hway in umo cells (Yu e al., 2005; Uli i e al., 2009). Mo eo e , ecen s udies ha e claimed ha eIF4E (euka yo ic ansla ion ini ia ion ac o 4E) migh be implica ed in so a enib-dependen Mcl-1 inhibi ion (Rahmani e al., 2005). Nowadays, so a enib is he only Food and D ug Adminis a ion (FDA)-app o ed HCC sys emic he apy, expanding pa ien mean su i al om 7.9 o 10.7 mon hs (Llo e e al., 2008; Guan and He, 2011). Despi e ini ial esponse, mos pa ien s de elop disease p og ession p obably as a consequence o umo esis an cells which do no espond o his molecule, mainly due o up egula ion o some su i al pa hways which may co e up he dea h signals induced by so a enib. The e o e, a be e knowledge o hose cellula ou es is equi ed o o e come unwan ed umo esis ance and consequen ly imp o e he bene icial e ec s o so a enib he apy (Knie el e al., 2014; Sakai e al., 2015; Togashi and Nishio, 2015). Mac oau ophagy (he ea e e e ed o as au ophagy) is a bulk deg ada ion sys em which ecycles un olded, damaged, o useless cellula componen s, like p o eins o o ganelles, o he main enance o cellula homeos asis in o de o p omo e adap a ion and cell su i al (San-Miguel e al., 2014, 2015; Vallejo e al., 2014). Howe e , excessi ely s imula ion may lead o p og ammed cell dea h ins ead o su i al (Tsujimo o and Shimizu, 2005). In ac , i s de egula ion has been associa ed wi h some diseases such as neu odegene a i e diso de s, diabe es, cys ic ib osis, C ohn’s disease, di e se myopa hies, hepa i is, α-1 ypsin de iciency, ca diac hype ophy, and umo igenesis (Mizushima and Koma su, 2011). Au ophagy is ini ia ed wi h he o ma ion o a small memb anous esicle named phagopho e ha elonga es and engul s a speci ic o unspeci ic po ion o he cy oplasm, o ming a doubled-memb anous s uc u e named au ophagosome. A e wa ds, his o ganelle uses wi h a lysosome and o ms a combined esicle o au ophagolysosome, leading o he deg ada ion o he inne ma e ial by lysosomal enzymes, eleasing subs ances ha become a disposal o he syn hesis o newly mac omolecules o ma ion o ene gy p oduc ion (Tanida, 2011). Au ophagic p ocess in ol es a highly conse ed g oup o mac omolecules which we e disco e ed in yeas s and named as au ophagy- ela ed genes (A g) (Tanida, 2011). In mammals, i e g oups o p o eins a e in ol e in au ophagosome o ma ion (Tanida, 2011). The i s is ULK1 (unc-51-like kinase) complex, whose unc ions a e he ec ui men o dis inc A g componen s and he main enance o phagopho e in eg i y (Mizushima, 2010). Nex , Beclin1-Vps34 ( acuola p o ein so ing 34) complex allows memb ane nuclea ion wi h o ma ion o PI3P (phospha idylinosi ol 3-phospha e) (Yuan e al., 2013). A e wa ds, A g9 and WIPI-1 (WD- epea p o ein in e ac ing wi h phosphoinosi ides) sys em b ings o phagopho e some lipids and p o eins which a e necessa y o i s elonga ion (O si e al., 2010). Finally, wo ubiqui in-like sys ems, A g5- A g12-A g16L and LC3 (mic o ubule-associa ed p o ein 1 ligh chain 3), ha conjuga ing wi h PE (phospha idyle hanolamine) cons i u es LC3-II ( an de Veen and Ploegh, 2012), a e bo h equi ed o au ophagosome o ma ion. The i s sys em plays an impo an ole in he ac i a ion o he second one, and LC3 p o ein is implica ed in he elonga ion o au ophagosome memb ane and in i s closu e (Sou e al., 2008). The e a e a ious ex acellula s imuli, such as nu ien dep i a ion, g ow h ac o wi hd awal o hypoxia, which ha e he abili y o induce au ophagy (He and Klionsky, 2009). S ess si ua ions, such as eac i e oxygen species (ROS) accumula ion o endoplasmic e iculum (ER) s ess can also modi y his cellula p ocess (He and Klionsky, 2009). The mos impo an pa hways in ol ed in au ophagy modula ion a e mTORC1 (mammalian a ge o apamycin complex 1) and AMPK (5′ AMP-ac i a ed p o ein kinase). The i s one abolishes au ophagy in p esence o nu ien s o g ow h ac o s, h ough ULK1 complex inhibi ion, while he second one p omo es au ophagy when cellula ene ge ic s a us is low (Sengup a e al., 2010; Manwani and McCullough, 2013). On he o he hand, some F on ie s in Pha macology | www. on ie sin.o g 2June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy sphingolipids a e also able o igge au ophagy (Li e al., 2014; O doñez e al., 2015). Speci ically, ce amide induces au ophagy- associa ed cell dea h, whe eas sphingosine-1-phospha e induces au ophagy-associa ed su i al (Li e al., 2014). The in e ac ion be ween Beclin-1 and Bcl-2 p o ein amily, as well as he pos - ansc ip ional egula ion by miRNAs ha e been ela ed o egula ion o au ophagy (Zhou e al., 2011; Sui e al., 2015). Au ophagy ac s as a double-edged swo d in cance cells because emo es newly mu a ed cells and damaged mi ochond ia in he ea ly s age o he disease, bu induces su i al in hypoxia and ischemia condi ions, as well as p omo es esis ance agains some chemo he apeu ic d ugs and umo p og ession a he la e phases (Eskelinen, 2011; Choi, 2012). In animal models o hepa oca cinogenesis i has been desc ibed ha au ophagy could play a p o ec ing ole du ing dysplas ic phase in no mal hepa ocy es, bu p omo es umo cells g ow h du ing he umo - o ming s age (Sun e al., 2013). Those appa en ly con o e sial esul s can be ela ed wi h he abili y o au ophagy o educe oxida i e s ess and main ain heal hy mi ochond ia p e en ing he ini ia ion o hepa oca cinogenesis, while i blocks he exp ession o p53 and o he umo supp esso s du ing la e phases o p omo e he de elopmen o HCC (Tian e al., 2015). Fu he mo e, some d ugs used in cance ea men induce au ophagy- ela ed cell dea h in cance cells (Sca la i e al., 2004). Thus, i is in e es ing o e iew he e ec s o his an i umo agen on he au ophagy p ocess in HCC cells, and he in luence o au ophagy on so a enib- ela ed cell esis ance gene a ion (Liu e al., 2016). A be e knowledge o he so a enib au ophagy- ela ed mechanisms could con ibu e o imp o e i s he apeu ic e iciency, inc easing cance pa ien su i al a es. AUTOPHAGY INDUCTION BY SORAFENIB Au ophagy is usually de egula ed in umo cells whe eas has been ela ed o cell su i al and d ug esis ance. So a enib and o he chemo he apeu ic d ugs ha e been shown o modula e au ophagy in di e en in i o and in i o expe imen al models (Gau hie and Ho, 2013). So a enib egula es au ophagy in a ious hepa ocellula cell lines (Table 1). In pa icula , di e en s udies ha e shown he p esence o acid esicles which a e ypical ea u es o au ophagosomes in so a enib- ea ed cells (Table 1; Pa k e al., 2008; Chiou e al., 2010; Shi e al., 2011; Shimizu e al., 2012; Eum e al., 2013; Honma and Ha ada, 2013; Tai e al., 2013; Fische e al., 2014; S iuso e al., 2015). Mo eo e , so a enib can also p omo e LC3 lipida ion, an ob ious sign o au ophagy induc ion (Tai e al., 2013; Yuan e al., 2014; Zhai e al., 2014). Fo example, i has been obse ed ha LC3-II o ma ion by so a enib is dose-dependen and ime-dependen in HepG2, MHCC97-L, Huh7, HLF, and PLC/PRF/5 HCC cells (Shi e al., 2011; Shimizu e al., 2012). In addi ion, so a enib modula es he exp ession o mul iple au ophagy ma ke s. Thus, he d ug s imula es Beclin1, A g5, and A g12 exp ession in HCC cells in i o (Yuan e al., 2014), Beclin-1 exp ession is inc eased by so a enib in a ime-dependen ashion in Hep3B cells (Ca e al., 2013), so a enib can mildly induce Beclin1 and A g-5 exp ession whe eas dec eases p62 exp ession in a signi ican manne in PLC-5 cells (Tai e al., 2013), o inc eases A g5, Vps34 and Beclin-1, dec eases p62 and does no a ec UVRAG exp ession in Huh7 and HepG2 cells (Zhai e al., 2014). Mo eo e , au ophagy induced by so a enib eaches he lysosome deg ada o y phase, as demons a ed by using a mRFP-GFP- LC3 combined luo escen - ag (Shimizu e al., 2012). Se e al disc epancies in au ophagy induc ion ha e been also obse ed in so a enib- ea ed HCC cells (Chiou e al., 2010; Fische e al., 2014). This appa en ly pa adoxical disc epancy and o he s, abou he e ec s o so a enib in he au ophagic mechanisms, a e included in he Table 2. So a enib also egula ed au ophagy in non HCC cance cells (Table 3) such as mac ophages, os eosa coma, mul iple myeloma, colo ec al ca cinoma cells, p os a e, mamma y, hy oid, and enal cance cells, (Walke e al., 2009; Ullen e al., 2010; Ba e o d e al., 2011a,b; P is e e e al., 2011; Kha aziha e al., 2012, 2013; Lin e al., 2013; Zheng e al., 2015) h ough di e en pa hways which a e summa ized in he Table 3. Some s udies connec so a enib adminis a ion and au ophagy modula ion in expe imen al HCC models in i o (Tables 1, 3). In all esea ch done un il now, so a enib can inc ease au ophagosome o ma ion and modi y au ophagy ma ke s exp ession in a simila way o models in i o (Shi e al., 2011; Shimizu e al., 2012; Tai e al., 2013). The only s udy analyzing he po en ial link be ween so a enib and au ophagy in pa ien s has been pe o med in e ac o y o elapsed lymphop oli e a i e disease, demons a ing ha LC3-II base le els a e lowe in non- esponsible pa ien s compa ed o esponde s, and ha pa ien s who espond o so a enib show a highe educ ion o LC3 exp ession a e 1 mon h o ea men (Guide i e al., 2012). Rego a enib, a s uc u al analog o so a enib, induces au ophagosome o ma ion in HCC cells simila ly han so a enib (Ca e al., 2013; Ta allai e al., 2015). In ano he s udy, wo di e en so a enib analogs, -MTUCB and AUCMB, caused au ophagosome o ma ion and LC3 lipida ion in a ious HCC cell lines (Wecksle e al., 2014). Finally, sc-59, a kinase- independen de i a e o so a enib showed a highe au ophagy induc ion cha ac e ized by an inc eased abili y o induce LC3- lipida ion and acid esicles o ma ion (Tai e al., 2013). Some wo ks ha e es ablished ha so a enib induces au ophagy as a cellula su i al mechanism in HCC because when his pa hway is ep essed by a chemical d ug (like chlo oquine o ba ilomycin A1) o by a small in e e ing RNA (siRNA) agains Beclin-1 o A g5, so a enib kills mo e cance ous cells and i s an ip oli e a i e abili y imp o es, which means ha au ophagy induced by ha an i umo agen wo ks as a p o ec i e pa hway (Pa k e al., 2010; Yuan e al., 2014). Mo eo e , simila e ec s ha e been also desc ibed in o he non HCC cance cells (Tables 1, 3;Ma in e al., 2009; Walke e al., 2009; Kha aziha e al., 2012; Zheng e al., 2015). Howe e , o he s udies ha e obse ed opposi e esul s in HCC (Tables 1, 3;Eum e al., 2013; Tai e al., 2013; Ta allai e al., 2015) and non-HCC cells (Lian e al., 2012; Lin e al., 2012). Tumo cell esis ance o so a enib can also be ela ed o swi ch om au ophagy- ela ed dea h o au ophagy- ela ed HCC cell su i al (Zhai e al., 2014). Mo eo e , ano he di e en way o gene a e so a enib esis ance consis s in he abolishmen o au ophagy induc ion. In ac , F on ie s in Pha macology | www. on ie sin.o g 3June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy TABLE 1 | E ec o so a enib on au ophagy ma ke s in HCC in i o o in i o models. Re e ences Model E ec s on au ophagy ma ke s Global e ec s Role o au ophagy Ca e al., 2013 Rego a enib in Hep3B, PLC/PRF/5, HepG2 ↑LC3-II ↑Beclin-1 Inc ease apop osis on umo cells (i inc eases caspase 3, 8, and 9 ac i i y, Bax exp ession, and dec eases Bcl-2 p o ein le els) No assessed Eum e al., 2013 Mul id ug- esis an Ras-NIH 3T3/Md cells ↑LC3-posi i e esicles So a enib aises HCC cell dea h h ough he ac i a ion o au ophagy pa hway and he inhibi ion o mTOR ac i i y Cell dea h Fische e al., 2014 Hep3B, HuH7 ↑LC3 lipida ion only in HuH7, bu wi h no e ec s in Hep3B cells Those cell lines ha e di e en au ophagy esponsi eness o so a enib and ha migh be linked o gene a ion o so a enib esis an cells No assessed Shi e al., 2011 MHCC97-L, PLC/PRF/5, HepG2 ↑Au ophagosome o ma ion ↑LC3 lipida ion ↑A g5 IRE-1αsignaling pa hway o ER s ess is necessa y o au ophagy induc ion by so a enib Cell su i al Shi e al., 2011 Nude mice o o hopically implan ed wi h MHCC97-L ↑CHOP Au ophagy inhibi ion dec ease umo olume in so a enib and so a enib + clo oquine ea ed mice Cell su i al Shimizu e al., 2012 HuH7, HLF, PLC/PRF/5 ↑LC3 lipida ion ↓p62 ↑Au ophagosome o ma ion =A g5 and Beclin-1 Inhibi ion o au ophagy inc eases cell sensi i i y o so a enib Cell su i al Shimizu e al., 2012 Xenog a umo s o HuH7 cells in nude mice ↑LC3 lipida ion Au ophagy inhibi ion dec ease umo olume in So a enib ea ed mice Cell su i al Tai e al., 2013 PLC/PRF/5, Hep3B, Sk-Hep-1, HepG2 ↑LC3 lipida ion ↓p62 ↑Beclin-1 and A g5 So a enib induces au ophagy h ough he dis up ion o Beclin-1-Mcl-1 complex Cell dea h Tai e al., 2013 Nude mice injec ed wi h PLC-5 Au ophagy induc ion So a enib induces au ophagy in i o h ough p-STAT inhibi ion and abolishes cance p oli e a ion Cell dea h Zhai e al., 2014 So a enib- esis an and sensi i e HepG2 and HuH7 cells. ↑LC3-II. A g5, Vps34, Beclin1 ↓p62 in bo h, esis an and sensi i e cells al hough esis an cells show lowe le els o ha ma ke s Lack o so a enib-induced au ophagy in HCC cells leads o gene a ion o so a enib- esis an cells P o ec ion in pa en al cells, bu p omo ion o cell dea h in esis an cell lines Zhai e al., 2014 Mice injec ed wi h HuH7 esis an cells Resul s in acco dance o in i o assay Au ophagy beha io swi ch is able o modi y cell sensi i eness o so a enib. Resul s in acco dance o in i o assay i has been demons a ed ha so a enib esis an cells show lowe le els o au ophagy ma ke s such as LC3, A g5, Vps34, o Beclin1 (Zhai e al., 2014). Fo all hese easons, no maliza ion o au ophagy may be one o he key mechanisms o a oid cellula esis ance o ha an ineoplas ic agen (Zhai e al., 2014; Liu e al., 2016). EFFECTS ON AUTOPHAGY OF SORAFENIB COMBINATION WITH OTHER DRUGS Some s udies ha e analyzed changes in au ophagy modula ion in HCC cells ea ed wi h di e en so a enib-based d ug combina ions (Table 4). The adminis a ion o an inhibi o o his one deace ylases (HDAC), enzyme implica ed in he egula ion o gene ansc ip ion ela ed o p omo ion o p og ession o cance (Dokmano ic e al., 2007; Giannini e al., 2012), has been shown o supp ess umo cell p oli e a ion. The mos impo an membe o ha g oup is o inos a , he i s HDACi o be app o ed o human clinical use (Giannini e al., 2012). When o inos a is combined wi h so a enib in HCC cul u ed cells, cell iabili y dec eases mo e han in cells ea ed wi h so a enib o , o inos a alone (Pa k e al., 2008, 2010). Fu he mo e, d ug combina ion can induce a highe Beclin-1, A g5, o A g12 exp ession and LC3 lipida ion han ea men wi h only one chemo he apeu ic agen (Pa k e al., 2008; Yuan e al., 2014). When A g5 o Beclin-1 we e silenced wi h siRNA in hose s udies, iabili y dec eased mo e in cance cells han in con ol cells, being he d op highe in he d ug combina ion ea ed g oup (Pa k e al., 2008; Yuan e al., 2014). This esul is compa ible wi h he p osu i al p ope ies o au ophagy du ing he an ip oli e a i e syne gis ic e ec o hose d ugs (Table 4; Pa k e al., 2008; Ma in e al., 2009; Yuan e al., 2014). The low e icacy o doxo ubicin, as a single agen in HCC, has led o e alua e i s ac i i y in combined ea men wi h so a enib (Mano e al., 2011). Doxo ubicin belongs o an h acyclines g oup, a ype o an ibio ic which we e i s isola ed om soil bac e ia (Yang e al., 2014), ha can gene a e simul aneously F on ie s in Pha macology | www. on ie sin.o g 4June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy TABLE 2 | Disc epancies exis en be ween di e en so a enib ei he in i o o in i o s udies. Condi ion Fi s si ua ion Second si ua ion LC3 ↑Le els in Huh7 cells, inducing mo e d ug esponse (Fische e al., 2014) Mode a e ↑le els in Hep3B cells, inducing less d ug esponse (Fische e al., 2014). Au ophagy ↑Le els, p o ec ing cance ous cells om cell dea h bo h in i o an in i o models (Shimizu e al., 2012) ↑Le els, p omo ing p og ammed cellula dea h in cance ous cells bo h in i o an in i o models (Tai e al., 2013) Au ophagy ↓Le els in d ug combina ion, educing side e ec s o bo h d ugs (Mano e al., 2011) ↑Le els in d ug combina ion, leading o enhance d ug syne gism (Yuan e al., 2014) mTORC1 ↓Phospho yla ion, leading o au ophagy induc ion and cell dea h (Zhai e al., 2014; Zhang e al., 2015) No changes in phospho yla ion associa ed wi h so a enib cell esis ance (Ramak ishnan e al., 2012) mTORC1 ↓Phospho yla ion by some o he analogs o so a enib associa ed wi h au ophagy (Ta allai e al., 2015) No changes in phospho yla ion by some o he analogs o so a enib, no being au ophagy induc ion dependen on ha pa hway (Wecksle e al., 2014) Ak ↓Exp ession associa ed wi h inc emen s in cellula dea h bo h in i o and in i o expe imen s (Euli e al., 2010) ↑Le els bo h in i o and in i o models, leading o induc ion o su i al au ophagy, su i al pa hways, and inc easing so a enib cell esis ance (Zhai e al., 2014) AMPK ↑Phospho yla ion due o he gene a ion o a educ ion o ATP cellula le els (Teso i e al., 2015) ↑Phospho yla ion due o he elease o ROS om mi ochond ia (Pignochino e al., 2015) AMPK ↑Phospho yla ion wi hou au ophagy associa ed (Teso i e al., 2015) No changes in AMPK ac i a ion and no au ophagy associa ed (S i ipa e al., 2013) ER s ess ↑IRE-1αexp ession, leading o au ophagy induc ion (Shi e al., 2011)↑PERK exp ession, bu non-au ophagy induc ion associa ed (Shi e al., 2011) Sphingolipids ↑Ce amide o ma ion a in i o models, leading o induc ion o au ophagy and p og ammed cell dea h (Pa k e al., 2010) ↓Sligh ly S1P le els a in i o models (Beljanski e al., 2011) TABLE 3 | E ec o so a enib on au ophagy ma ke s in o he in i o o in i o cance ous models dis inc o HCC. Re e ences Model E ec s on au ophagy ma ke s Global e ec s Role o au ophagy Lin e al., 2013 Human mac ophages ↑Au ophagic acuoles ↑LC3 lipida ion So a enib s imula es au ophagy bu i inhibi s phagocy osis and sec e ion o IL-10 No assessed Kha aziha e al., 2012 Myeloma cell lines LP1, RPMI-8226 ↑LC3 lipida ion ↓p62 ↑LC3-posi i e esicles So a enib induces au ophagy which p o ec agains caspase-dependen and independen cell dea h Cell su i al Kha aziha e al., 2012 Myeloma pa ien samples ↑LC3 lipida ion I induces cell dea h and au ophagy Cell dea h Kha aziha e al., 2012 Myeloma mice models ↑LC3 lipida ion So a enib inc eases mice su i al, educes umo de elopmen and induces au ophagy pa hway Cell dea h Walke e al., 2009 So a enib plus o inos a ea men in a colo ec al cance cell line, HCT116 ↑LC3 lipida ion ↑A g5 So a enib ea men induces a sligh ly amoun o au ophagy which is cy op o ec i e and is s imula ed by o inos a co ea men Cell su i al Ullen e al., 2010 P os a e ca cinoma cell lines DU145 and PC3 ↑Au ophagosome o ma ion So a enib al e s mi ochond ial po en ial and induces apop osis and au ophagy No assessed Ba e o d e al., 2011b Ful es an - esis an and sensi i e MCF7 cell line (o igina ing om b eas adenoca cinoma) ↑Au ophagosome o ma ion, ↑Beclin-1 ↑A g5-A g12 ↑LC3-II ↓p62 So a enib induces au ophagy pa hway alone o in combina ion wi h pe me exed, and ha induc ion sensi izes ha cells o cell dea h Cell dea h P is e e e al., 2011 Human os eosa coma cell line U2OS ↑WIPI ↑Au ophagosome o ma ion So a enib induces au ophagy in no mal and s a ed cells and ha is induced by calcium ion elease o cy oplasm No assessed Lin e al., 2012 Medulla y hy oid cance cell lines MTG-1 and TT ↑LC3-II ↑A g5 So a enib induces bo h au ophagy and apop osis in ha in i o model Cell dea h Zheng e al., 2015 Di e se enal ca cinoma cell lines like 786-0, A498 and SK-RC-44 ↑Beclin-1 ↑A g5 ↓p62 ↑LC3-II and LC3-II/I a io So a enib induces a cy op o ec i e o m o au ophagy in enal ca cinoma cells Cell su i al F on ie s in Pha macology | www. on ie sin.o g 5June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy TABLE 4 | E ec o so a enib combined ea men wi h ano he d ug on au ophagy in HCC and o he cance ypes. Re e ence Pa hophysiological condi ion Model D ug combined wi h so a enib So a enib alone e ec s D ug combina ion e ec s Global e ec o bo h d ugs ea men Yuan e al., 2014 Hepa ocellula ca cinoma In i o Vo inos a ↑Beclin-1 ↑A g5 ↑A g7 ↑LC3-II ↑↑Beclin-1 ↑↑A g5 ↑↑A g7 ↑↑LC3-II D ug combina ion enhances Beclin-1-dependan p o ec i e o m o au ophagy Mano e al., 2011 Hepa ocellula ca cinoma In i o Doxo ubicin ↑LC3-II ↓LC3-II So a enib ac s as an an agonis o doxo ubicin Ta allai e al., 2015 Hepa ocellula ca cinoma In i o Sildena il ↑Au ophagic acuoles =LC3 =p62 ↑↑Au ophagic acuoles ↑LC3 ↓p62 Sidena il p omo es so a enib e ec s on au ophagy and s imula e au ophagic cell dea h Lam e al., 2015 Hepa ocellula ca cinoma In i o PHY906 ↑LC3 ↓ULK1 ↑↑LC3 ↑ULK1 PHY906 s imula e so a enib- ela ed au ophagy Ba e o d e al., 2011b B eas adenoca cinoma In i o Peme exed ↑Beclin-1 ↑A g5-A g12 ↑LC3-II ↓p62 ↑↑Beclin-1 ↑↑A g5-A g12 ↓sligh ly LC3-II ↓p62 Pe me exed p omo es so a enib- ela ed au ophagy induc ion Hamed e al., 2015 Glioblas oma In i o Lapa inib ↑Au ophagic acuoles =p62 ↑Beclin-1 ↑LC3-II/I ↓LAMP2 ↑↑au ophagic acuoles ↓p62 =Beclin-1 ↓LC3-II/I ↓LAMP2 Lapa inib p omo es so a enib cellula dea h h ough au ophagy pa hway Jakubowicz-Gil e al., 2014 Glioblas oma mul i o me and anaplas ic as ocy oma In i o Que ce in ↑Au ophagic esicles, Beclin-1 and LC3-I/II only in glioblas omamul i o me cell line. ↑↑Au ophagic esicles, Beclin-1 and LC3-I/II only in he same cell line as so a enib alone Que ce in p omo es so a enib cell dea h in bo h cell lines bu only induces au ophagy in one o hem Lian e al., 2012 And ogen-independen p os a e cance In i o and in i o (–) gossypol ↑Au ophagic esicles ↑LC3-I/II ↓p62 ↑↑Au ophagic esicles ↑↑LC3-I/II ↓↓p62 P e e en ially in one o he cell lines es ed (–) gossypol agonis s so a enib au ophagy and induces cellula dea h opoisome ase II poisoning, DNA adduc o ma ion, ce amide o e p oduc ion and oxida i e s ess (Yang e al., 2014). One o he main p oblems o he use o doxo ubicin alone in he apy is he high numbe o side e ec s (Yang e al., 2014). In e es ingly, so a enib dec eases doxo ubicin- ela ed au ophagy, wi h a educ ion o he exp ession o LC3 and i s lipida ion (Table 4;Mano e al., 2011). Sildena il is ano he agen which has been combined wi h so a enib in HCC (Table 4;Ta allai e al., 2015). This d ug is able o inhibi phosphodies e ase 5, an enzyme which ans o ms cyclic GMP (cGMP) in o his inac i e o m (Das e al., 2015). Sildena il is used mainly in he ea men o e ec ile dys unc ion and o some ca dio ascula diseases because i p oduces asodila a ion (Das e al., 2015). I has also been pos ula ed ha sildena il is able o induce he in insic pa hway o apop osis in colo ec al ca cinoma cells and lympha ic leukemia cells (Boo h e al., 2014; Das e al., 2015). Sildena il inc eases he an ip oli e a i e p ope ies o so a enib and ego a enib (Table 4;Ta allai e al., 2015). The combined ea men inc eases au ophagosome o ma ion ollowed by he accumula ion o ed luo escence a 24 h in o GFP-RFP-LC3- ans ec ed HCC cells. Mo eo e , he educ ion o cell dea h by ego a enib and sildena il in cells ea ed wi h A g5, Beclin-1, o ULK1 siRNA sugges s ha au ophagy may ac as a p o-dea h mechanism in his se ing (Ta allai e al., 2015). So a enib has also been combined wi h PHY906, an he bal mix u e which consis s o ou dis inc componen s: Glycy hiza u alensis,Paeonia lac i lo a,Scu ella ia baicalensis oo s, and Ziziphus jujuba ui . This plan mix u e is based on an old Chinese o mula ion used o he ea men o a ious gas oin es inal diseases, like dia hea, e e , o omi ing (Liu and Cheng, 2012; Rockwell e al., 2013). Recen s udies ha e shown he e icacy o PHY906 as a chemo he apeu ical adju an (Kumma e al., 2011). When his he bal mix u e is combined wi h so a enib, exp ession o au ophagy ma ke s inc eases. Paeonia lac i lo a and Scu ella ia baicalensis a e he c i ical componen s o ha mix u e in ela ion o au ophagy induc ion, because ollowing supp ession o hose plan s om he he bal blend, LC3 is no lipida ed (Table 4; Lam e al., 2015). Simila ly, di e en combina ions o so a enib wi h o he d ugs and an ioxidan s o he bal mix u es seem o be able o modula e au ophagy in non-li e cance cells (see Table 4). F on ie s in Pha macology | www. on ie sin.o g 6June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy AUTOPHAGY-RELATED CELLULAR PATHWAYS AND SORAFENIB TREATMENT The e a e some p o eins and cellula pa hways in umo cells ha can be in ol ed in he egula ion o au ophagy by so a enib. Those egula o y ou es ha e a changing e ec , because hey a e dependen on he cell s a e, i s o igin o some medium ea u es. The mos impo an a e desc ibed in de ail in he ollowing sec ions (Figu e 1). mTOR Pa hway The mTOR pa hway is one o he main egula o s o cellula me abolism in esponse o oxida i e s ess, un olded p o ein esponse, hypoxia, nu ien s dep i a ion o g ow h ac o de iciency (Neu eld, 2010; Yang and Ming, 2012; Sa ka , 2013). The inhibi ion o mTOR signaling by so a enib is ela ed o induc ion o au ophagy (Table 5,Figu e 1). Mos s udies ha e shown ha so a enib is able o dec ease mTORC1 phospho yla ion, exp ession, and ac i i y bo h in cul u ed cells in i o and in xenog a umo implan a ion in mice (Liu e al., 2012; Zhai e al., 2014). In HCC in i o models, i has been desc ibed ha so a enib inhibi s mTORC1 phospho yla ion du ing pe iods om 24 o 48 h (Zhai e al., 2014; Zhang e al., 2015). Fu he mo e, so a enib is able o dephospho yla e p70S6K and 4E-BP1, which a e wo ob ious e idences o mTORC1 ac i i y inhibi ion in HCC cells (Liu e al., 2012) and o he cance s (Euli e al., 2010; Gulha i e al., 2012; Kha aziha e al., 2012; Tang e al., 2012; Eum e al., 2013; Hamed e al., 2015). Howe e , i has been shown ha so a enib is no able o al e phospho yla ion s a us o mTORC1 bu educes p70S6K and 4EBP1 phospho yla ion in cul u ed non-Hodgkin lymphoma cell lines (Ramak ishnan e al., 2012). O he in i o s udies also sugges ha so a enib is able o educe mTORC1 ac i i y in HCC xenog a models ollowed by a dec eased phospho yla ion o i s downs eam p o eins, p70S6K, 4E-BP1, and eIF-4E (Liu e al., 2012; Zhai e al., 2014). I has been shown ha so a enib educes in i o and in i o mTORC1 signaling and p70S6K phospho yla ion, bu inc eases mTORC2 h ough inc easing Se 2481mTOR, being his la e e ec abolished by e e olimus co- ea men in os e osa coma p eclinical models (Figu e 1; Pignochino e al., 2013). Some esea che s ha e assessed i he induc ion o au ophagy by so a enib is due o ep ession o mTOR signaling pa hway in HCC (Shimizu e al., 2012; Zhai e al., 2015) and o he cance s (Ba e o d e al., 2011a,b; Kha aziha e al., 2012; Eum e al., 2013). Due o dual ole o au ophagy in cellula dea h, mTOR inhibi ion migh lead o dea h o su i al o cance cells, depending on whe he au ophagy ep essed by his p o ein wo ks, espec i ely, as a cell dea h induce , o as a su i al mechanism in bo h HCC and non-HCC cells (Kha aziha e al., 2012; Shimizu e al., 2012; Ta allai e al., 2015). So a enib analogs ha e a di e en abili y o abolish mTOR in cul u ed cell lines in i o. Some o hem, such as ego a enib o SK-01105, a e able o induce mTOR dephospho yla ion simila ly o so a enib, whe eas o he compounds, like -AUCMB o -MTUCB, canno inhibi mTOR ac i i y, so au ophagy induc ion media ed by hose so a enib analogs is no modula ed by mTORC1 ac i i y (Wecksle e al., 2014; Ta allai e al., 2015). The majo ups eam induce o mTORC1 pa hways is PI3K/Ak signaling (Sa ka , 2013). In so a enib- esis an cells, Ak exp ession is usually o e -s imula ed, and ea men wi h some speci ic ep esso s is able o inc ease so a enib- ela ed cell dea h, which means ha combined ea men wi h so a enib and an Ak inhibi o may be use ul because i migh imp o e so a enib sensi i i y (Zhai e al., 2015). Di e en epo s ha e shown ha so a enib inhibi s Ak ac i i y and i s phospho yla ion in HCC and enal ca cinoma cells (RCC) (Table 5;Euli e al., 2010; Gulha i e al., 2012; Se o a e al., 2013; Hamed e al., 2015; Zhang e al., 2015). Howe e , o he s udies ound ha so a enib induces Ak phospho yla ion, which will TABLE 5 | E ec o so a enib on mTOR/Ak pa hway in umo cells. Re e ences Cell lines Pa hophysiological condi ion E ec on ma ke s o mTOR/Ak pa hway Global e ec Hamed e al., 2015 GBM12 Glioblas oma mul i o me ↓p-Ak ↓p-mTOR ↓p-p70 So a enib induces Ak /mTOR pa hway inhibi ion when ha e passed only 6 h o ea men Liu e al., 2012 PLC/PRF/5, HepG2 and Hep3B Hepa ocellula ca cinoma ↓p-mTOR ↓p-p70S6K ↓p-4E-BP1 ↑p-Ak Two hou s o ea men wi h so a enib is able o down egula e mTOR and all i s ela ed pa hways Ramak ishnan e al., 2012 Dohh2 Non-Hodgkin lymphoma ↓p-p70 ↓p-4E-BP1 =p-mTOR So a enib ails in inac i a e mTOR phospho yla ion a 8 h o ea men Tang e al., 2012 GBM15 Glioblas oma mul i o me ↓p-p70 =p-mTOR Twen y-Fou hou s o ea men wi h so a enib educes sligh ly mTOR pa hway induc ion Zhai e al., 2014 Huh7 and HepG2 Hepa ocellula ca cinoma ↓p-mTOR ↓p-p70S6K ↓p-4E-BP1 ↑p-Ak So a enib inhibi s mTOR pa hway ac i i y and ha inac i a ion s imula es au ophagy esponse Zhang e al., 2015 SMMC-772l Hepa ocellula ca cinoma ↓Ak , PI3K and mTOR a 8 h o ea men , a e wa ds hei le els inc eases So a enib induces a ansi o y inac i a ion o Ak /mTOR pa hway F on ie s in Pha macology | www. on ie sin.o g 7June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy FIGURE 1 | So a enib induces au ophagy esponse h ough modula ion o he main downs eam ac o s and pa hways. In his scheme, some o he media o s o au ophagy induc ion by so a enib in umo cells a e ep esen ed. So a enib may induce AMPK pa hway because i educes ATP le els and inc eases ROS, which leads o inhibi ion o mTORC1 signaling pa hway. So a enib can also s imula e ER s ess, speci ically IRE-1αb anch and all i s downs eam genes, and elease calcium ion o cy osol, which induces au ophagosome o ma ion. I may also dis up Beclin-1 and Bcl-2 complex, wi h Beclin-1 elease. O he non-p o ein media o s which may be in ol ed in so a enib e ec s a e miRNA30αand sphingolipids, because he d ug can educe miRNA30αsignaling, which is a Beclin-1 ep esso , induce ce amide o ma ion, and educe S1P le els, leading o au ophagosome o ma ion. lead o gene a e esis ance agains ha chemo he apeu ic agen (Table 5;Liu e al., 2012; Zhai e al., 2015). Finally, a hi d g oup o wo ks ha e epo ed ha so a enib has no in luence in he phospho yla ion s a us o Ak (Gedaly e al., 2010). In summa y, so a enib appea s o inac i a e mTORC1 ac i i y, which would con ibu e o au ophagy induc ion. The mechanism esponsible o hose e ec s emains unclea , bu , in some cases, could in ol e he PI3K/Ak pa hway. AMPK Pa hway AMPK is a he e o ime ic complex ac ing as a senso o ene gy s a us in euka yo ic cells (G ahame Ha die, 2014; No iko a e al., 2015). AMPK ac i a o s may be used as adju an s in a ious cance he apies, because i s s imula ion can induce au ophagy o cell cycle s op in umo cell (Mo oshima e al., 2006; Donadon e al., 2010; Rehman e al., 2014). So a enib ac i a es AMPK being his e ec po en ially ele an du ing induc ion o au ophagy in cance cells (Figu e 1;Eum e al., 2013; Fische e al., 2014; Teso i e al., 2015). So a enib is able o induce AMPK phospho yla ion in a ime-dependen ashion and in a dose-dependen manne in expe imen al models in i o, speci ically in cul u ed cells coming om di e en ypes o human umo s (Eum e al., 2013; Fuma ola e al., 2013; Pignochino e al., 2013, 2015; Fische e al., 2014; G oenendijk e al., 2015; Teso i e al., 2015). I has been demons a ed ha he incuba ion wi h 5 µM o so a enib in mul id ug esis an cells cul u ed in i o can s imula e AMPK phospho yla ion in a ime- dependen manne , s a ing a 0.5 h a e ea men (Eum e al., 2013). So a enib also induces AMPK phospho yla ion (48 h) in lung adenoca cinoma o non-small cell lung cance (G oenendijk e al., 2015). The d ug is also able o induce AMPK ac i a ion in a ious b eas cance cell lines (Fuma ola e al., 2013). On he o he hand, he e a e some expe imen al models in which so a enib is no able o induce AMPK phospho yla ion due o he use o low concen a ions o he an i umo agen (S i ipa e al., 2013). Cu iously, some di e ences in AMPK modula ion by so a enib ha e been desc ibed be ween Huh7 and Hep3B HCC cell lines, showing inc eases only in Huh7 cells bu wi hou changes in Hep3B (Fische e al., 2014). The e a e wo p incipal hypo heses which explain he mechanism by which so a enib induces AMPK phospho yla ion (Figu e 1). The i s one is ha so a enib gene a es a educ ion F on ie s in Pha macology | www. on ie sin.o g 8June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy in cellula ATP le els ha inc ease AMP/ATP a io and AMPK ac i a ion (Fuma ola e al., 2013; Teso i e al., 2015). An expe imen al s udy which co obo a es ha hypo hesis demons a ed ha ATP le el in so a enib- ea ed lung adenoca cinoma cells dec eases mo e han 50% compa ed o he con ol g oup (Teso i e al., 2015). On he o he hand, he con i ma ion o he ole o ROS bu s du ing so a enib-induced AMP ac i a ion comes om a s udy in which AMPK- ela ed apop osis was p e en ed by he ea men wi h a ROS sca enge (Pignochino e al., 2013, 2015). The ac i a ion o ups eam kinases, LKB1 and CAMKKβ, is in ol ed on so a enib- ela ed AMPK ac i a ion in NSCLC cells in i o and in i o (G oenendijk e al., 2015). Ne e heless, i seems ha he AMPK pa hway could be no in ol ed in au ophagy-induc ion by so a enib, because LC3II exp ession inc eases sha ply when AMPK is inhibi ed in HCC cul u ed cells ea ed wi h so a enib. Whe eby, i is possible ha AMPK modula ion by so a enib pa icipa es in o he cellula p ocesses, di e en o au ophagy, which can also ake pa in o i s an ip oli e a i e ac ion, such as apop osis o glucose me abolism de egula ion (Pignochino e al., 2013; Teso i e al., 2015). Endoplasmic Re iculum S ess Endoplasmic e iculum is he main cellula o ganelle whe e p o ein syn hesis, modi ica ion, and olding a e ca ied ou and whe e calcium is s o ed. In he p esence o di e en s esses caused by physiological o pa hological changes, non- olding o un olding p o eins accumula e in o he o ganelle, gene a ing a new condi ion inside he cell called ER s ess. ER s ess is nega i ely in e e ing wi h p o ein syn hesis and a ec s o he unc ions o ha o ganelle, such as calcium homeos asis, which inally may cause p og ammed cell dea h (Tuñón e al., 2013; Kania e al., 2015). This si ua ion leads o he ac i a ion o he un olded p o ein esponse (UPR), which ies o eco e he ini ial si ua ion (Jheng e al., 2014). Some o he s a egies ha his esponse uses o alle ia e ER s ess a e educ ion o p o ein ansla ion, exp ession o di e se chape ones, induc ion o p o ein deg ada ion p ocesses, such as ubiqui in-p o easome sys em, and deg ada ion o po ions o he endoplasmic e iculum h ough he au ophagy pa hway (Ve aillie e al., 2010). The h ee essen ial p o eins in UPR induc ion a e inosi ol equi ing enzyme 1α(IRE1α), p o ein kinase R-like ER kinase (PERK) and ac i a ing ansc ip ion ac o (ATF6) (C espo e al., 2012). These mac omolecules a e loca ed in basal condi ions in o he ER memb ane and hey a e inhibi ed by he chape one binding immunoglobulin p o ein (BiP). In s ess si ua ions, BiP disassembles o hese molecules, causing hei ac i a ion and he s imula ion o h ee di e en p o ein cascades which p omo e he UPR (Malhi and Kau man, 2011). So a enib igge s he UPR esponse in di e en expe imen al in i o models, which may con ibu e o he so a enib- ela ed induc ion o au ophagy and o i s an ip oli e a i e e ec s (Table 6,Figu e 1). So a enib-induced UPR is un ela ed o MAPK inhibi ion because ERK ep ession canno s imula e ER s ess (Rahmani e al., 2007; Shi e al., 2011). Mo e in de ail, so a enib is able o ac i a e wo o he h ee b anches implica ed in he esponse agains ER s ess (Rahmani e al., 2007; Yi e al., 2012). Speci ically, his d ug induces he exp ession o IRE1α and PERK, whe eas ATF6 exp ession emains cons an wi hou changes in he exp ession on downs eam p o eins such as BiP (Table 6;Rahmani e al., 2007; Yi e al., 2012). In ac , i has been pos ula ed ha he e ec i eness o ATF6 is consequence o he p o ound al e a ion o he sec e o y pa hway induced by so a enib (Yi e al., 2012). O he expe imen s ha e claimed ha so a enib educes di ec ly BiP exp ession, chape one ela ed wi h he induc ion o UPR media ed by his chemo he apeu ic agen (Table 6;Rahmani e al., 2007; Jiang e al., 2014). Di e en esea ch has demons a ed ha so a enib induces a p onounced inc ease in he exp ession o PERK (Table 6), which modi ies he ac i i y o all i s downs eam p o eins (Rahmani e al., 2007; Pa k e al., 2008; Shi e al., 2011; Yi e al., 2012; Holz e al., 2013). One o he mos impo an is eIF2α(euka yo ic ansla ion ini ia ion ac o 2α), is a ipa i e p o ein complex ha binds and hyd olyzes GTP du ing i s ole in ec ui ing he ini ia o me hionyl- RNA o he 40S ibosome o begin mRNA ansla ion in euka yo ic cells (Ve aillie e al., 2010). Some s udies ha e shown ha so a enib is able o induce eIF2α phospho yla ion on Se 51 when i has passed 2 h since he s a o he ea men (Rahmani e al., 2007; Yi e al., 2012; Dixon e al., 2014). The phospho yla ion o eIF2αp e en s binding o GTP and consequen ly educes p o ein ansla ion in cance cells (Rahmani e al., 2007; Yi e al., 2012). The las o he UPR b anches which is modi ied by so a enib is he IRE1αpa hway. Some s udies ha e sugges ed ha his an i umo al agen is able o s imula e IRE1αexp ession, inducing i s ac i a ion and changing he exp ession o di e en downs eam ac o s (Table 6,Figu e 1;Rahmani e al., 2007; Shi e al., 2011; Yi e al., 2012). In his way, IRE1αhas a key ole in he splicing and subsequen ly ansla ion o xbp1 (Malhi and Kau man, 2011), and so a enib s imula es he splicing o his gene simila ly o he incuba ion wi h di e se ER s ess induc o s, such as unicamycin o hapsiga gin (Yi e al., 2012). Cu iously, when IRE1αo xbp1 a e knocked down, cell sensibili y o so a enib inc eases (Rahmani e al., 2007). The endoplasmic e iculum is he main ese oi o calcium ion (Ca2+) (Kania e al., 2015). So a enib is able o dis up e iculum homeos asis because i discha ges all he Ca2+ ion p esen in ha o ganelle and induces i s accumula ion in o he cy osol (Rahmani e al., 2007). This educ ion o Ca2+endoplasmic e iculum s o ages inc eases ROS p oduc ion, inducing oxida i e s ess, and may con ibu e o he cance ous cell dea h induced by so a enib (Figu e 1;Rahmani e al., 2007). I ER s ess is p olonged o e ime, UPR migh be o e whelmed because ha o ganelle may be ull o un olded and useless p o eins, and ha si ua ion would gene a e p og ammed cell dea h h ough CHOP (C/EBP homologous p o ein) media o , which is a ansc ip ion ac o in ol ed in he inc ease o he exp ession o a lo o genes ela ed wi h apop osis pa hway (Ve aillie e al., 2010; Malhi and Kau man, 2011). So a enib is able o induce he exp ession o CHOP and o some p o eases ela ed wi h ER s ess p og ammed cell dea h, such as caspase-2 o -4 (Table 6). IRE1αhas also been shown o induce caspase-12 oligome iza ion h ough associa ion wi h F on ie s in Pha macology | www. on ie sin.o g 9June 2016 | Volume 7 | A icle 151 P ie o-Domínguez e al. So a enib and Au ophagy HDAC inhibi o s o human hepa oma cells. Wo ld J. Gas oen e ol. 20, 4953–4962. doi: 10.3748/wjg. 20.i17.4953 Yuan, H. X., Russell, R. C., and Guan, K. L. (2013). Regula ion o PIK3C3/VPS34 complexes by MTOR in nu ien s ess-induced au ophagy. Au ophagy 9, 1983–1995. doi: 10.4161/au o.26058 Zhai, B., Hu, F., Jiang, X., Xu, J., Zhao, D., Liu, B., e al. (2014). Inhibi ion o Ak e e ses he acqui ed esis ance o so a enib by swi ching p o ec i e au ophagy o au ophagic cell dea h in hepa ocellula ca cinoma. Mol. Cance The . 13, 1589–1598. doi: 10.1158/1535-7163.MCT-13-1043 Zhai, B., Jiang, X., He, C., Zhao, D., Ma, L., Xu, L., e al. (2015). A senic ioxide po en ia es he an i-cance ac i i ies o so a enib agains hepa ocellula ca cinoma by inhibi ing Ak ac i a ion. 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This is an open-access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion License (CC BY). The use, dis ibu ion o ep oduc ion in o he o ums is pe mi ed, p o ided he o iginal au ho (s) o licenso a e c edi ed and ha he o iginal publica ion in his jou nal is ci ed, in acco dance wi h accep ed academic p ac ice. No use, dis ibu ion o ep oduc ion is pe mi ed which does no comply wi h hese e ms. F on ie s in Pha macology | www. on ie sin.o g 16 June 2016 | Volume 7 | A icle 151