Effect of FHIT Gene Replacement on Growth, Cell Cycle and Apoptosis in Pancreatic Cancer Cells

The human FHIT gene is altered or lost in many cancers and FHIT has been shown to be a tumor suppressor. However, the mechanism of tumor suppression by the FHIT gene remains unclear. FHIT expression is lost in primary pancreatic cancer and human pancreatic cancer cell lines. To gain insight into the function of FHIT gene, we replaced the FHIT gene in a FHIT-null pancreatic cancer cell line, and established stable fhit-expressing clones. Expression of the exogenous fhit was at similar levels as in other cultured cell lines and fhit protein was found predominantly associated with perinuclear area. fhit replacement resulted in reduced cell proliferation in transfected Panc-1 cells. Cell cycle distribution analysis indicated increased accumulation of G(0)/G(1) phase cells in transfected clones indicating a retardation of cell cycle progression. We observed specific up-regulation of cdc2 and cyclin D3 upon fhit replacement. Furthermore, Bcl-2 family members Bad, Bak, and Bcl-xS protein levels were increased in FHIT transfected clones when compared with Panc-1 cells. Multiplex RT-PCR of apoptosis pathway related genes revealed that Bcl-2 is absent and Bcl- xS message increases in FHIT transfected clones. Our data suggested that exogenous expression of FHIT in Panc-1 cells affects genes regulating cell cycle arrest and apoptosis, and these molecular changes may contribute to the tumor suppressor activity of the FHIT gene.