Correlations between natural resistance to doxorubicin, proliferative activity, and expression of P-glycoprotein 170 in human kidney tumor cell lines

Paclitaxel sensitivity in relation to ABCB1 expression, efflux and single nucleotide polymorphisms in ovarian cancer

ABCB1 (adenosine triphosphate-binding cassette transporter B1) mediates cellular elimination of many chemotherapeutic agents including paclitaxel, which is commonly used to treat ovarian cancer. A significant association between common single nucleotide polymorphisms (SNPs) in ABCB1 and progression-free survival has been reported in patients with ovarian cancer. Variable paclitaxel clearance due to genotype specific differences in ABCB1 activity in cancer cells and/or normal tissues may underlie the association. Using cell-based models, we evaluated the correlations between ABCB1 expression, polymorphisms, transporter activity and paclitaxel sensitivity in ovarian cancer (n = 10) and lymphoblastoid (n = 19) cell lines. Close associations between ABCB1 expression, transporter function and paclitaxel sensitivity were found in lymphoblastoid cell lines, although we could not demonstrate an association with common SNPs. In ovarian cancer cell lines, ABCB1 expression was low and the association between expression and function was lost. These results suggest that ABCB1 related survival difference in ovarian cancer patients is more likely to be due to differential whole body paclitaxel clearance mediated by normal cells rather than a direct effect on cancer cells.

Investigation of multidrug resistance in cultured human renal cell carcinoma cells by 31P-NMR spectroscopy and treatment survival assays

KTCTL-26 and KTCTL-2 are renal cell carcinoma (RCC) lines with high and low expression of P-170 glycoprotein, respectively. Inherent differences between the two cell lines in terms of phosphate metabolites and growth characteristics in culture were examined for possible association with multidrug resistance (MDR). Differences in response to drug treatment were investigated for 40 h incubations with various doses of vinblastine (VBL) alone or as cotreatments with various concentrations of the calcium antagonist diltiazem (DIL) and/or interferon-alpha (IFN-alpha). Treatment effects were quantitated using the MTT survival assay and 31P magnetic resonance spectroscopy (MRS) to determine phosphate metabolite profiles in intact cells. KTCTL-2 and KTCTL-26 cells exhibited significant inherent differences in phosphocholine, glycerophosphocholine, glycerophosphoethanolamine, and phosphocreatine levels. KTCTL-26 cells were more sensitive than KTCTL-2 to 0.011 mircroM VBL alone (87% vs. 102% survival) or to 0.011 microM BL + 10 microM DIL (55% vs. 80% survival). The latter treatment resulted in a significant decrease in the ratio of phosphocholine to glycerophosphocholine in KTCTL-26 cells but no significant changes in phosphate metabolites in KTCTL-2 cells. Metabolomic 31P MRS detects different metabolite profiles for RCC cell lines with different MDR phenotypes and may be useful for noninvasive characterization of tumors in a clinical setting.

Reverse correlation between P-glycoprotein expression and proliferative activity in endometrial adenocarcinoma

Immunohistochemical study was employed using a monoclonal antibody (C219) to investigate P-glycoprotein expression in 23 normal endometria and 40 endometrial adenocarcinomas. P-glycoprotein immunopositivity was observed in the mid- to late-proliferative phase and the whole secretory phase of normal endometrium. In contrast, no P-glycoprotein was detected in endometrium of early proliferative phase nor post-menopausal endometrium. We also investigated the expression of P-glycoprotein in endometrial cancers to find 16 out of the 40 endometrial adenocarcinomas (40%) expressed P-glycoprotein. P-glycoprotein immunopositivity was often observed in gland growing parts but not in solid growing parts in a given tumor specimen. Proliferative activity of the tumor, as measured by PCNA labeling, was significantly higher in the P-glycoprotein-negative group than that in P-glycoprotein-positive group (P < 0.005). Thus, there was a strong reverse relation between P-glycoprotein expression and proliferative activity in endometrial adenocarcinomas.

Relationship of inherent resistance to doxorubicin, proliferative activity and expression of P-glycoprotein 170, and glutathione S-transferase-pi in human lung tumors

BACKGROUND

This study analyzed whether proliferative activity and expression of P-glycoprotein 170 (P-170) or glutathione S-transferase-pi (GST-pi) in human non-small cell lung carcinomas (NSCLC) represent independent factors in resistance to doxorubicin or whether an association exists between these factors.

METHODS

Thirty-six patients with previously untreated NSCLC participated in the study. The thymidine labelling index (TLI) was measured for detection of proliferative activity, and immunohistochemistry was used for detection of P-170 and GST-pi. The resistance of tumors was determined in vitro by the nucleotide incorporation assay.

RESULTS

Negative correlations between TLI and P-170 (P = 0.0009) or GST-pi (P = 0.007) were found. Positive correlations existed between resistance to doxorubicin in vitro and P-170 (P = 0.005) or GST-pi (P less than 0.0001). Expression of P-170 and GST-pi showed highly significant (P less than 0.0001) positive correlation.

CONCLUSIONS

The results demonstrate that a significant positive relationship between P-170 and GST-pi in NSCLC exists and that the expression is increased in resistant tumors and in tumors with a low proliferative activity.

Antibody-directed therapy of multidrug-resistant tumor cells

The major obstacle to effective cancer chemotherapy is the resistance of tumor cells to cytostatic agents. Tumor cells frequently express a multidrug-resistance (MDR) phenotype. In an effort to devise new strategies to overcome MDR, antibody-directed approaches for the eradication of MDR cells have been developed. Experimental data have shown that multidrug-resistant tumor cells can be efficiently killed by monoclonal antibodies, immunotoxins, or bispecific antibodies. The current experimental results indicate that an antibody-directed therapeutic approach to eradication of MDR cells might be a promising adjunct to conventional chemotherapy of cancer patients.