title: Expression and regulation of prostate apoptosis response-4 (Par-4) in human glioma stem cells in drug-induced apoptosis.
abstract: Gliomas are the most common and aggressive of brain tumors in adults. Cancer stem cells (CSC) contribute to chemoresistance in many solid tumors including gliomas. The function of prostate apoptosis response-4 (Par-4) as a pro-apoptotic protein is well documented in many cancers; however, its role in CSC remains obscure. In this study, we aimed to explore the role of Par-4 in drug-induced cytotoxicity using human glioma stem cell line--HNGC-2 and primary culture (G1) derived from high grade glioma. We show that among the panel of drugs- lomustine, carmustine, UCN-01, oxaliplatin, temozolomide and tamoxifen (TAM) screened, only TAM induced cell death and up-regulated Par-4 levels significantly. TAM-induced apoptosis was confirmed by PARP cleavage, Annexin V and propidium iodide staining and caspase-3 activity. Knock down of Par-4 by siRNA inhibited cell death by TAM, suggesting the role of Par-4 in induction of apoptosis. We also demonstrate that the mechanism involves break down of mitochondrial membrane potential, down regulation of Bcl-2 and reduced activation of Akt and ERK 42/44. Secretory Par-4 and GRP-78 were significantly expressed in HNGC-2 cells on exposure to TAM and specific antibodies to these molecules inhibited cell death suggesting that extrinsic Par-4 is important in TAM-induced apoptosis. Interestingly, TAM decreased the expression of neural stem cell markers--Nestin, Bmi1, Vimentin, Sox2, and Musashi in HNGC-2 cell line and G1 cells implicating its potential as a stemness inhibiting drug. Based on these data and our findings that enhanced levels of Par-4 sensitize the resistant glioma stem cells to drug-induced apoptosis, we propose that Par-4 may be explored for evaluating anti-tumor agents in CSC.
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Jayashree C
authors: JC
authors: Jagtap
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Parveen
authors: P
authors: Dawood
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Reecha D
authors: RD
authors: Shah
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Goparaju
authors: G
authors: Chandrika
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Kumar
authors: K
authors: Natesh
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Anjali
authors: A
authors: Shiras
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Amba S
authors: AS
authors: Hegde
authors: Department of Neurosurgery, D. Y. Patil Medical College, Pune, India.
authors: Deepak
authors: D
authors: Ranade
authors: National Centre for Cell Science (NCCS), Pune, India.
authors: Padma
authors: P
authors: Shastry
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D051336:Mitochondrial Membranes / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000166:cytology* / Q000187:drug effects; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C101296:prostate apoptosis response-4 protein; D013629:Tamoxifen; D048049:Extracellular Signal-Regulated MAP Kinases; C505407:CASP3 protein, human; D053148:Caspase 3