S100A4 contributes to the suppression of BNIP3 expression, chemoresistance, and inhibition of apoptosis in pancreatic cancer.

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.

Amplicon mapping and transcriptional analysis pinpoint cyclin L as a candidate oncogene in head and neck cancer.

DNA gains targeting the 3q chromosome are common in head and neck squamous cell carcinomas, as well as in lung, ovarian, and cervical cancer. Several candidate oncogenes located on 3q were proposed, i.e., PIK3CA, p63, and eIF-5A2. However, none of these genes was found included in a narrow high-level amplification. Recently, microarray-based comparative genomic hybridization (array CGH) was developed for high-resolution screening of deletions and amplifications in tumor genomes. In this study, by microarray-based comparative genomic hybridization, we found a narrow 3q25.3 high-level amplification in a head and neck cancer cell line. We precisely delimited the 3-Mb length-amplified segment by semiquantitative PCR and measured the transcriptional level of every gene (RefSeq full-length mRNA) located inside this segment by cDNA microarray and quantitative reverse transcription-PCR. Four genes were overexpressed in three head and neck cancer cell lines with increased DNA copy number, compared with a control tongue cell line. We extended the transcriptional analysis of these four genes to 20 head and neck squamous cell carcinomas. Only one gene, cyclin L (ania-6a), is commonly overexpressed in primary tumors compared with corresponding normal tissues. This cyclin was previously pinpointed as a candidate for a role in promoting cell cycle entry. Thus, we propose cyclin L as a candidate oncogene in head and neck cancer.