Apoptosis and its role in the mechanisms of growth regulation of tumor cells with multiple drug resistance

: Development of apoptosis was followed up in the cell line LIM-1863 of human colon carcinoma and in the same cell line with multiple drug resistance (MDR) related to the expression of gene mdr I and hyperproduction of protein P-glycoprotein 170 encoded by this gene. The number of cells with histological and ultrastructural features of apoptosis increased with acquirement by tumor cells of typical MDR. The enhancement of apoptosis in tumor cells with MDR results probably from the increase of cells with signs of terminal differentiation which is one of apoptosis inducers. Mitotic activity in both lines did not change essentially, but the original line had a more rapid growth than its analogue with MDR. Elimination of cells through apoptosis may be the cause of slower growth of the cell line with apoptosis. The rate of tumor growth depends on the balance between proliferative activity and apoptosis.