Introduction:
The role of fibroblast growth factor-2 (FGF-2) on colorectal cancer (CRC) cells
exposed to chemotherapy has not been studied extensively. This thesis investigated
whether FGF-2 mediates chemoresistance in primary (SW480) and metastatic
(SW620) colon adenocarcinoma cell lines.
Methods:
Proliferation assays were used to assess the response of SW480 and SW620 colon
cancer cell lines to varying concentrations of FGF-2 and to optimise the dose of 5-
FU at which 50% cell death was observed. Cell survival assays were performed
following 96 hours exposure to 5-FU ± FGF-2. Levels of chemotherapy induced
apoptosis were determined using Caspase-3/7 assay. Expression of anti-apoptotic
proteins (Bcl-2 and Bcl-XL) and FGFRs at both protein and gene level were
determined to see if these contributed to the difference in chemoprotection observed. Results:
At 0.25 ng/ml, FGF-2 did not affect proliferation in either cell lines. 25μM of 5-FU
resulted in 50% kill in both cell lines. Significant cell survival was observed when
FGF-2 (0.25 ng/ml) pre-treated SW620 cells were exposed to 5-FU (25 μM)
compared to cells exposed to 5-FU alone (81% vs 60%, p=0.015). This
chemoresistance was associated with attenuation of cellular apoptosis (p=0.04) with
no significant change in expression of Bcl-2 and Bcl-XL at gene or protein level. This
survival advantage was not seen in SW480 cells (59% vs 55%, p=0.35). There were
no observed differences in the expression of FGFR1-4 in either cell lines.
Conclusion:
FGF-2 offers chemoresistance to SW620 and not to SW480 cells exposed to 5-FU.
Both cell lines expressed fgf2 and fgfr1-4 genes, suggesting that fgfr expression does
not account for the difference in chemoresistance. FGF-2 offered protection by
causing significant reduction in chemotherapy induced apoptosis in SW620 colon
cancer cell line; however this was not due to increased expression of anti-apoptotic
proteins. The molecular mechanisms for this selective chemoprotection need to be
investigated further.