Differential anthracycline sensitivity in two related human colon carcinoma cell lines expressing similar levels of P-glycoprotein

Chemosensitivity of the human colon carcinoma HCT-15 cell line to 4′-epidoxorubicin proved to be 100-fold higher than that of its variant HCT-15 EDR. Confocal scanning microscopy showed significant less drug accumulation in HCT-15 EDR. A 2-fold increase in hsp27 expression was found in HCT-15 EDR, with no alteration in hsp70. The expression of the drug exporter Pgp was similar in both cell lines, despite the lower drug accumulation shown by HCT-15 EDR in respect to HCT-15. Other molecules implicated in the acquisition of enhanced chemoresistance or a more active Pgp variant present in HCT-15 EDR, could explain the phenomenon.