Effect of diverse categories of drugs on human colon tumour cell proliferation.

The effect of a number of drugs belonging to different therapeutic categories on cell proliferation in a human colon cancer cell line (HT 29) was studied. Generally, drugs classified as calcium antagonists had a moderate to strong inhibitory effect on cell growth. The EC50 value for prenylamine, perhexiline and bepridil was 10 microM. The so-called calcium channel blockers (verapamil, nifedipine, diltiazem) were less effective. With the exception of the sodium selective ionophore, monensin, which was extremely potent (EC50 less than 0.1 microM), calmodulin antagonism appeared to be a common feature of compounds inhibiting cell proliferation of human colon tumour cells.