Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Results concerning a possible link between susceptibility to natural-cell-mediated immune cytolysis and the multi-drug resistance (MDR) phenotype are conflicting. We evaluated in human acute lymphocytic leukemia the relationship between acquired drug resistance and susceptibility to cytolysis mediated by endogenous, interferon-activated, and interleukin-2-activated natural cytotoxic cells. Eight human leukemia drug-resistant/sensitive cell line pairs were evaluated; drug-resistant sub-lines included those selected for primary resistance to adriamycin, etoposide, teniposide, vincristine, and vinblastine. A majority of P-glycoprotein-positive MDR sub-lines displayed slight but statistically significant resistance to endogenous and/or interferon-activated natural-killer(NK)-cell-mediated lysis, as compared with the drug-sensitive parental type. P-glycoprotein-negative sub-lines displayed variable NK susceptibility; within this group, the variants selected for primary etoposide resistance were more susceptible to NK cytolysis than parental cells. Results of cold-target-inhibition experiments suggest that altered NK susceptibility does not arise solely from modulation of NK target recognition and adherence structures. IL2-activated killer (LAK) cells lysed both drug-sensitive and drug-resistant lines. Two MDR lines selected for primary etoposide resistance displayed enhanced LAK susceptibility. In contrast, the 2 variants selected for resistance to adriamycin exhibited partial resistance to LAK-mediated killing, which could be overcome at high effector-to-target ratios. Our results support the development of interleukin-2/LAK immunotherapy for the treatment of leukemias with acquired drug resistance.
 ...
PMID:The relationship between multi-drug resistance and resistance to natural-killer-cell and lymphokine-activated killer-cell lysis in human leukemic cell lines. 137 Apr 37

Drug resistance has been associated with resistance to NK- and LAK-cell-mediated cytotoxicity. We evaluated this issue in human cell lines, using multiple myeloma cells (8226) and 2 multi-drug-resistant (MDR) sublines selected using doxorubicin (8226/Dox40) and mitoxantrone (8226/MR40). In parallel, we studied the human breast carcinoma cell line series MCF7, MCF7/D40 and MCF7/Mitox. Unlike the sensitive parental cell lines, all 4 sublines display MDR-patterns of resistance, with the P-glycoprotein pump (P-170) detected only in the doxorubicin-selected sublines. Flow cytometric and immunocytochemical analyses showed expression of cellular adhesion molecules ICAM-I and LFA-3, and MHC-Class-I (MCF7/D40 only), to be decreased in the doxorubicin-selected MDR-sublines, whereas expression of CD56 (Leu 19) was strongly up-regulated in 8226/Dox40. Lysis of P-170-positive MDR tumor cells by NK or LAK cells was, however, unaffected by these alterations, suggesting redundancy in effector:target-cell adhesion pathways. Mitoxantrone-selected tumor cells did not display P-170, nor did they show altered expression of cellular adhesion molecules. Their susceptibility to NK or LAK cytolysis was also unimpaired as compared to the parental cell lines. Clinically, these results imply that immunotherapeutic modalities aiming at increased natural killer functions deserve full consideration even in patients who have become refractory to further cytostatic drug treatment.
 ...
PMID:Altered expression of P-glycoprotein and cellular adhesion molecules on human multi-drug-resistant tumor cells does not affect their susceptibility to NK- and LAK-mediated cytotoxicity. 171 Jun 9

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.
 ...
PMID:P-glycoprotein-mediated multidrug resistance and lymphokine-activated killer cell susceptibility in ovarian carcinoma. 894 80