Effects of paclitaxel on the growth of normal, polyposis, and cancerous human colonic epithelial cells

BACKGROUND. The specific paclitaxel dose or time course in the treatment of colon carcinoma without the disruption of normal colonic cell proliferation is currently not known. The aim of this study was to determine the effects of paclitaxel on the growth of human colonic epithelial cells using cultures of normal, polyposis, and cancerous cells. METHODS. Normal, polyposis, and cancerous human colonic cells (Caco-2, T-84, and LoVo cell lines) were cultured, then treated with paclitaxel (10^-9-10^-5 M) for 0-7 days. {AU: Please verify all dosages throughout.} Cell proliferation was assayed using either a Coulter-Counter or MTT-growth assay. Immunofluorescence and Western immunoblotting measured P-glycoprotein. RESULTS. Low paclitaxel doses (1 x 10^-9-10^-8 M) were more effective than higher paclitaxel doses (>1 x 10^-8 M) in the growth inhibition of polyposis, Caco-2, and LoVo cancer (but not T-84) cell lines. Low paclitaxel doses had little effect on normal colonic cell growth over 7 days. Higher paclitaxel doses (> 1 x 10^-8-10^-5 M) produced a dose-dependent inhibitory effect on the growth of normal human colonic epithelial cells over 7 days but had no effect on the growth of polyposis, Caco-2, and LoVo cells over 3-7 days of treatment. Immunofluorescence and Western immunoblotting of cultures showed that 1 x 10^-6 M paclitaxel increased P-glycoprotein expression in Caco-2 and LoVo cells. There was no effect of paclitaxel on P-glycoprotein expression in T-84 cancer cells, which were found to have high endogenous basal levels of P-glycoprotein. P-glycoprotein expression in Caco-2 cells was found on plasma membranes and in perinuclear areas. CONCLUSIONS. Lower paclitaxel doses are more effective over time for the growth inhibition of polyposis and cancerous colonic cells, with minimal effects on the growth of normal colonic epithelial cells. Increased P-glycoprotein expression appears to be correlated with paclitaxel resistance in polyposis and cancerous colonic cells.