title: S100A4 contributes to the suppression of BNIP3 expression, chemoresistance, and inhibition of apoptosis in pancreatic cancer.
abstract: Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease that is characterized by a particularly marked resistance to chemotherapy. We previously showed an association between decreased expression of BNIP3 and chemoresistance in PDAC cell lines. To further explore the molecular basis of chemoresistance in PDAC, we analyzed microarray data obtained from normal pancreas and PDAC tumor samples to identify genes exhibiting a negative correlation with the expression profile of BNIP3. This analysis identified several S100 family proteins, of which two, S100A2 and S100A4, showed in vitro the ability to repress exogenous BNIP3 promoter activity. We subsequently showed that RNA interference-mediated S100A4 knockdown resulted in an elevated expression of BNIP3 in PDAC cell lines that possess an unmethylated BNIP3 promoter, suggesting that, in addition to hypermethylation, S100A4 overexpression may represent an alternative mechanism for inhibiting BNIP3 function in PDAC. S100A4 knockdown also resulted in an increased sensitivity of PDAC cell lines to gemcitabine treatment, which was coupled with an increase in apoptosis and cell cycle arrest. To investigate the underlying mechanisms mediating these effects, we studied the effect of silencing the expression of S100A4 on the induction of apoptosis, cell cycle arrest, and the activation of apoptotic mediators. Knockdown of S100A4 clearly induced apoptosis with increased fragmentation of DNA and phosphatidyl serine externalization; activation of caspase-3, caspase-9, and poly(ADP-ribose) polymerase; and release of cytochrome c into the cytosol. These findings provide evidence that supports a novel role for S100A4 as a prosurvival factor in pancreatic cancer.
authors.affiliation: Centre for Molecular Oncology, Institute of Cancer and the Cancer Research UK Clinical Centre, Barts and The London School of Medicine, London, United Kingdom.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Mahon
authors.forename: Patrick
authors.initials: P
authors.lastname: Baril
authors.forename: Vipul
authors.initials: V
authors.lastname: Bhakta
authors.forename: Claude
authors.initials: C
authors.lastname: Chelala
authors.forename: Krishna
authors.initials: K
authors.lastname: Caulee
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Harada
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Lemoine
mesh_terms: D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D014162:Transfection; D000093542:Gemcitabine
chemical_list: C090121:BNIP3 protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; D003841:Deoxycytidine; C077591:S100A4 protein, human; D020169:Caspases; D000093542:Gemcitabine