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P-glycoprotein-mediated multidrug resistance and lymphokine-activated killer cell susceptibility in ovarian carcinoma
1Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada.
Abstract:
The sensitivity of tumor cells to lysis by natural killer (NK) and interleukin-2 (IL-2)-activated killer (LAK) cells was studied in three ovarian carcinoma cell lines (2780.9S, SKOV-3, and CHOAUXB1), four multidrug-resistant (MDR) variants, and a melphalan-resistant line. The antitumor activity of LAK cells was evaluated both by 51Cr release and by conjugate formation assays. Four of four P-glycoprotein-positive (P-gp+) MDR ovarian carcinoma cell line variants were lysed by human LAK cells to a greater extent than were their drug-sensitive counterparts. In contrast, a melphalan-resistant ovarian carcinoma cell line that does not overexpress P-gp (P-gp-) did not exhibit an increased susceptibility to LAK cells relative to its parental cell line. Two of the four P-gp+ MDR ovarian carcinoma cell line variants were tested for human NK cell susceptibility and this was found to be unchanged or decreased. The P-gp+ MDR ovarian carcinoma cell line 2780.AD645 showed a higher frequency of tumor cell binding to LAK cells than did the drug-sensitive parental line. A monoclonal antibody (mAb) against a cell surface epitope of P-gp, MRK16, used at 1 microgram/ml, enhanced the LAK susceptibility of P-gp+ MDR ovarian carcinoma cell lines. However, when incubation with 10 micrograms/ml MRK-16 antibody (Ab) was followed by 12.5 micrograms/ml F(ab')2 goat anti-mouse (GAM) immunoglobulin (Ig), the increased LAK susceptibility of P-gp+ MDR cell lines was inhibited. These data strongly suggest that P-glycoprotein-positive MDR ovarian carcinoma cells not only are targets for LAK cells, but are more sensitive than their drug-sensitive parental lines. This is in contrast to their susceptibility to NK cells, which is low to start with and remains unchanged or even decreased in MDR cells. It is postulated here that P-gp or associated changes result in a greater frequency of effector-target cell binding, leading to increased LAK cell cytotoxicity.
Insights
Multidrug-resistant ovarian cancer cells expressing P-glycoprotein show increased sensitivity to killer (LAK) cells. This enhanced LAK cell targeting contrasts with natural killer (NK) cell activity, suggesting P-glycoprotein influences immune cell interactions.
Area of Science:
- Immunology
- Cancer Biology
- Molecular Biology
Background:
- Multidrug resistance (MDR) is a significant challenge in ovarian carcinoma treatment.
- P-glycoprotein (P-gp) is a key efflux pump implicated in MDR.
- The interaction between immune effector cells and MDR tumor cells requires further elucidation.
Purpose of the Study:
- To investigate the susceptibility of P-gp-positive multidrug-resistant (MDR) ovarian carcinoma cell lines to lysis by natural killer (NK) and interleukin-2 (IL-2)-activated killer (LAK) cells.
- To determine the role of P-gp in modulating the sensitivity of ovarian cancer cells to immune-mediated cytotoxicity.
- To explore the effect of a P-gp specific monoclonal antibody on LAK cell-mediated killing.
Main Methods:
- Culturing of ovarian carcinoma cell lines, including drug-sensitive and MDR variants.
- Evaluation of LAK and NK cell antitumor activity using 51Cr release and conjugate formation assays.
- Treatment with P-gp specific monoclonal antibody (MRK16) and its F(ab')2 fragment.
Main Results:
- P-gp-positive MDR ovarian carcinoma cell lines exhibited significantly greater lysis by LAK cells compared to their drug-sensitive counterparts.
- Melphalan-resistant, P-gp-negative cells did not show increased susceptibility to LAK cells.
- NK cell susceptibility was unchanged or decreased in P-gp-positive MDR cells.
- The MRK16 antibody enhanced LAK cell susceptibility of P-gp+ MDR cells, an effect inhibited by subsequent goat anti-mouse immunoglobulin.
Conclusions:
- P-glycoprotein expression in ovarian carcinoma cells enhances their susceptibility to LAK cell-mediated lysis.
- Increased effector-target cell binding, potentially mediated by P-gp, contributes to augmented LAK cell cytotoxicity.
- These findings highlight a differential impact of P-gp on LAK versus NK cell activity against ovarian cancer, suggesting therapeutic potential for targeting P-gp in immunotherapy.