title: Manumycin A inhibits triple-negative breast cancer growth through LC3-mediated cytoplasmic vacuolation death.
abstract: Therapy resistance can be attributed to acquisition of anti-apoptotic mechanisms by the cancer cells. Therefore, developing approaches that trigger non-apoptotic cell death in cancer cells to compensate for apoptosis resistance will help to treat cancer effectively. Triple-negative breast cancers (TNBC) are among the most aggressive and therapy resistant to breast tumors. Here we report that manumycin A (Man A), an inhibitor of farnesyl protein transferase, reduces cancer cell viability through induction of non-apoptotic, non-autophagic cytoplasmic vacuolation death in TNBC cells. Man A persistently induced cytoplasmic vacuolation and cell death through the expression of microtubule-associated protein 1 light chain 3 (LC3) and p62 proteins along with endoplasmic reticulum (ER) stress markers, Bip and CHOP, and accumulation of ubiquitinated proteins. As inhibitors of apoptosis and autophagy failed to block cytoplasmic vacuolation and its associated protein expression or cell death, it appears that these processes are not involved in the death induced by Man A. Ability of thiol antioxidant, NAC in blocking Man A-induced vacuolation, death and its related protein expression suggests that sulfhydryl homeostasis may be the target of Man A. Surprisingly, normal human mammary epithelial cells failed to undergo cytoplasmic vacuolation and cell death, and grew normally in presence of Man A. In conjunction with its in vitro effects, Man A also reduced tumor burden in vivo in xenograft models that showed extensive cytoplasmic vacuoles and condensed nuclei with remarkable increase in the vacuolation-associated protein expression together with increase of p21, p27, PTEN and decrease of pAkt. Interestingly, Man A-mediated upregulation of p21, p27 and PTEN and downregulation of pAkt and tumor growth suppression were also mimicked by LC3 knockdown in MDA-MB-231 cells. Overall, these results suggest novel therapeutic actions by Man A through the induction of non-apoptotic and non-autophagic cytoplasmic vacuolation death by probably affecting ER stress, LC3 and p62 pathways in TNBC but not in normal mammary epithelial cells.
authors: Department of Pathology, UT Health Science Center at San Antonio, San Antonio, TX 78229, USA.
authors: P K
authors: PK
authors: Singha
authors: S
authors: S
authors: Pandeswara
authors: M A
authors: MA
authors: Venkatachalam
authors: P
authors: P
authors: Saikumar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000627:therapeutic use / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects; D051231:Farnesyltranstransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D005260:Female; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D011090:Polyenes / Q000737:chemistry / Q000627:therapeutic use / Q000633:toxicity*; D053284:Polyunsaturated Alkamides / Q000737:chemistry / Q000627:therapeutic use / Q000633:toxicity*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D051742:Transcription Factor CHOP / Q000378:metabolism; D014183:Transplantation, Heterologous; D054875:Ubiquitination
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000900:Anti-Bacterial Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; C497249:DDIT3 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D011090:Polyenes; D053284:Polyunsaturated Alkamides; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D051742:Transcription Factor CHOP; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051231:Farnesyltranstransferase; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C054474:manumycin