Novel role of Fas-activated serine/threonine kinase (FASTK) in proliferation and survival of pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is the most aggressive pancreatic cancer with an overall 5-year survival rate of <5%. Despite significant advances in treatment of the disease during the past decade, the median survival rate (˜6 months) has hardly improved, warranting the need for novel diagnostic and therapeutic targets and approaches.

We performed highly parallelized functional assays to identify novel target genes having key pathophysiological roles in pancreatic cancer. Reverse transfection microarrays were used to examine the functional effects of overexpression and knockdown of 88 pre-selected candidate genes in cancer and control cells. 19 candidates producing significant and reproducible effects were selected for further in-depth characterization.

This project aims to functionally characterize one of the selected genes, Fas-activated serine/threonine kinase (FASTK). Although FASTK was first described in mid nineties and has been shown to be implicated in regulation of apoptosis in certain cancer types, still the exact physiological functions of this gene remain largely obscure, especially with respect to PDAC.

qRT-PCR data confirmed the overexpression of FASTK in pancreatic cancer tissues and further demonstrated that strong FASTK expression is also retained in the majority of pancreatic tumor cell lines in vitro. Functional effects of FASTK were investigated after transient knockdown in a variety of transformed and non-transformed cell lines. Proliferation (BrdU incorporation assay), viability (MTT assay) and clonogenic potential (Anchorage independent growth assay) of the cancer cells were significantly impaired by down-regulation of FASTK. Western blot analyses showed activation of apoptosis pathways (Caspase-3 and PARP cleavage). Further experiments involving generation of stable inducible (pTRIPZ shRNA) clones for further in vivo analyses as well as experiments for deciphering the pathways involved are currently in progress.

In conclusion, our experimental data show that knockdown of gene FASTK severely influences proliferation and viability of pancreatic cancer cells and results in significantly reduced resistance to apoptosis.