Increased sensitivity to gemcitabine of P-glycoprotein and multidrug resistance-associated protein-overexpressing human cancer cell lines

0.05), respectively. P-glycoprotein and MRP1 overexpression possibly caused a cellular stress resulting in increased gemcitabine metabolism and sensitivity, while reversal of collateral gemcitabine sensitivity by verapamil also suggests a direct relation between the presence of membrane efflux pumps and gemcitabine sensitivity

Docetaxel and gemcitabine activity in NSCLC cell lines and in primary cultures from human lung cancer

The activity of the following drugs was investigated in two established NSCLC cell lines: docetaxel, gemcitabine, vinorelbine, paclitaxel, doxorubicin (0.01, 0.1, 1 μg ml−1), cisplatin, ifosfamide (1, 2, 3 μg ml−1) and carboplatin (2, 4, 6 μg ml−1). The cytotoxic activity was evaluated by the sulphorhodamine B assay. The two most active drugs, docetaxel and gemcitabine, used singly and in association, were investigated as a function of treatment schedule. The sequence docetaxel→gemcitabine produced only a weak synergistic interaction in RAL but a strong synergism in CAEP cells. The synergistic interaction increased in both cell lines after a 48-h washout between the drug administrations. Flow cytometric analysis showed that in docetaxel→gemcitabine sequence, docetaxel produced a block in G2/M phase and, after 48 h, provided gemcitabine with a large fraction of recovered synchronized cells in the G1/S boundary, which is the specific target phase for gemcitabine. Conversely, simultaneous treatment induced an antagonistic effect in both cell lines, and the sequential scheme gemcitabine→docetaxel produced a weak synergistic effect only in RAL cells. Moreover, the synergistic interaction disappeared when washout periods of 24 or 48 h between two drug administrations were adopted. The synergistic activity of docetaxel→ 48-h washout→gemcitabine was confirmed in 11 of 14 primary cultures, which represents an important means of validating experimental results before translating them into clinical practice. © 1999 Cancer Research Campaig