Drug sensitivity of ten human tumor cell lines compared to mouse leukemia (L1210) cells

L1210 leukemia cells, because of their rapid growth rate in suspension culture and high growth fraction, are ideally suited to screen in vitro for cytotoxic compounds. Although L1210 cells may mimic rapidly growing tumors, they have not been effective in selecting agents active against slow growing solid tumors. We expected that cell lines originating from human solid tumors, because of their slower growth rate and lower S phase fraction, would be more drug resistant than L1210. Therefore, we compared ten human tumor cell lines (5 melanomas, 4 colon carcinomas and 1 small cell lung carcinoma) to L1210 growth inhibition by 9 antitumor drugs. Not one human tumor cell line was consistently more resistant to all nine drugs than L1210 when the cells were exposed to drugs for about 2 doubling times. The drug sensitivity of 2 cell lines (L1210 and SK MEL 28) was again determined after a short term (2 hr) exposure and using growth inhibition and cell survival as end points. For both end points these two cell lines exhibited a random pattern of sensitivity to the drugs tested. Cell kill showed an order of sensitivity different than growth inhibition. The implication of these findings for drug-screening is discussed.