The impact of p53 status on cellular sensitivity to antifolate drugs

The impact of p53 status on cellular sensitivity to antifolate drugs has be en examined in seven human cell lines (A549, MCF7, T-47D, CCRF-CEM, COR-L23 , A2780, and HCT-116) and p53 nonfunctional counterparts of two of the cell lines (HCT-116/N7 and A2780/CP70), p53 status was determined by sequencing and functional assays, The sensitivities of the cell lines to growth inhib ition (sulphorhodamine B assay) produced by four antifolate drugs (Alimta, methotrexate, raltitrexed, and lometrexol) were studied. There was no clear relationship between functional p53 status and sensitivity to methotrexate or lometrexol, whereas a functional p53 status was possibly associated wit h resistance to Alimta- and raltitrexed-induced growth inhibition. In contr ast, in the two pairs of related human tumor cell lines (HCT-116 and HCT-11 6/N7 and A2780 and A2780/CP70) cells with functional p53 were more sensitiv e to Alimta- and raltitrexed-induced growth inhibition (P = 0.002). Detaile d studies were performed with the A2780 cell lines, and in the parental cel ls sensitivity to Alimta- and raltitrexed-induced cytotoxicity (clonogenic assay) was similar to the sensitivity determined in the sulphorhodamine B a ssay, However, in A2780/CP70 cells, 1 muM of drug resulted in only 40-60% g rowth inhibition yet greater than or equal to 85% cytotoxicity. After Alimt a and raltitrexed exposure for less than or equal to 72 h, there were no di fferences between the A2780 and A278/CP70 cell lines in cell cycle phase di stribution, absolute cell number, or the induction of apoptosis, However, t he cellular protein content of the A2780/CP70 cells was 3-6-fold higher tha n in A2780 cells after Alimta and raltitrexed treatment, suggesting that ce lls without functional p53 can maintain protein synthesis in the absence of cell division (unbalanced cell growth). In conclusion, the apparent impact of functional p53 status on sensitivity to antifolate drugs may depend upo n the phenotypic/genotypic background as well as the assay used to measure cellular sensitivity.