CHFR silencing or microsatellite instability is associated with increased antitumor activity of docetaxel or gemcitabine in colorectal cancer

Phenotypic differences among cancers with the same origin may be associated with chemotherapy response. CHFR silencing associated with DNA methylation has been suggested to be predictive of taxane sensitivity in diverse tumor types. However, the use of microsatellite instability (MSI:unstable-MSS:stable) as a predictive marker for therapeutic effect has had conflicting results. We examined these molecular alterations as predictors of chemotherapy sensitivity in colorectal cancer (CRC). Differential sensitivity to docetaxel and gemcitabine was compared to potential predictive biomarkers CHFR methylation and MSI status. Cell lines that were MSI-H/CHFR-methylated, MSS/CHFR-methylated and MSS/CHFR-unmethylated were assessed for in vivo sensitivity of CRC cell line xenografts to docetaxel and/or gemcitabine. We observed increased sensitivity in vitro to gemcitabine in cell lines with MSI and docetaxel in cell lines with CHFR inactivation via DNA methylation. In vivo treatment of human xenografts confirmed differential sensitivity, with the MSI-H/CHFR-methylated line RKO having tumor growth inhibition to each agent, and at least additive tumor growth inhibition with combination therapy. The MSS-CHFR-unmethylated line, CACO ₂, was resistant to single and combination therapy, while COLO205, the MSS/CHFR-methylated line, showed tumor growth inhibition with docetaxel, but not gemcitabine, therapy. CHFR methylation in CRC cell lines predicted for sensitivity in vitro and in vivo to docetaxel, while MSI-H cell lines were more sensitive to gemcitabine. These data suggest that a subset of CRC patients would be selectively sensitive to a novel combination of gemcitabine and docetaxel, and are the basis for an ongoing clinical trial of this combination in a biomarker-selected patient population.