Regulation of FGF-2 by an endogenous antisense RNA: effects on cell adhesion and cell-cycle progression

Fibroblast growth factor (FGF-2) and its endogenous antisense RNA FGF antisense (FGF-AS) have been implicated in cancer progression and correlated with clinical outcomes of cancer patients. We previously reported that elevated FGF-AS expression is associated with reduced tumor recurrence and improved survival rates in patients with FGF-2-dependent esophageal adenocarcinoma. In the present study we examined the effect of siRNA knockdown of each transcript on the expression of its complementary partner RNA, and consequent changes in cellular phenotype and behavior. FGF-AS and FGF-2 were inversely expressed in a cell-cycle-dependent manner and siRNA-mediated knockdown of either FGF-AS or FGF-2 resulted in upregulation of the complementary transcript and protein. siRNA-mediated knockdown of FGF-AS was associated with a dramatic increase in cell-substratum adhesion and marked changes in the expression of a number of genes encoding adhesion molecules. Microarray analysis and RT-PCR analysis also revealed antithetical effects of FGF-2 and FGF-AS siRNA knockdown on the expression of a number of cell-cycle-related genes, including SKP2, SESTRIN-3, EIF4BP2, CDC27, and P190RhoGAP (P190). Cell-cycle analysis following siRNA-mediated knockdown of FGF-AS or FGF-2 indicate that both factors are involved in control of transition through the G₁ and G₂ boundaries, affecting cell-cycle progression, proliferation, and apoptosis. Finally, siRNA knockdown of FGF-AS resulted in a significant increase in invasion activity. These data indicate that regulatory interactions between FGF-AS and FGF-2 are involved in control of cell adhesion, cell-cycle progression, and invasion, providing a possible explanation for the protective effects of FGF-AS expression observed in FGF-2-dependent cancers.