P-glycoprotein expression and modulation of cell-membrane morphology in adriamycin-resistant P388 leukemia cells

Label-Free Assessment of the Drug Resistance of Epithelial Ovarian Cancer Cells in a Microfluidic Holographic Flow Cytometer Boosted through Machine Learning

About 75% of epithelial ovarian cancer (EOC) patients suffer from relapsing and develop drug resistance after primary chemotherapy. The commonly used clinical examinations and biological tumor tissue models for chemotherapeutic sensitivity are time-consuming and expensive. Research studies showed that the cell morphology-based method is promising to be a new route for chemotherapeutic sensitivity evaluation. Here, we offer how the drug resistance of EOC cells can be assessed through a label-free and high-throughput microfluidic flow cytometer equipped with a digital holographic microscope reinforced by machine learning. It is the first time that such type of assessment is performed to the best of our knowledge. Several morphologic and texture features at a single-cell level have been extracted from the quantitative phase images. In addition, we compared four common machine learning algorithms, including naive Bayes, decision tree, K-nearest neighbors, support vector machine (SVM), and fully connected network. The result shows that the SVM classifier achieves the optimal performance with an accuracy of 92.2% and an area under the curve of 0.96. This study demonstrates that the proposed method achieves high-accuracy, high-throughput, and label-free assessment of the drug resistance of EOC cells. Furthermore, it reflects strong potentialities to develop data-driven individualized chemotherapy treatments in the future.

Overexpression of CD133 promotes drug resistance in C6 glioma cells

Glioblastoma multiforme is an extremely aggressive and clinically unresponsive form of cancer. Transformed neoplastic neural stem cells, resistant to chemotherapy and radiation therapy, are thought to be responsible for the initial tumor formation and the recurrence of disease following surgical resection. These stem cells express multidrug resistance markers along with CD133. We show that ectopic overexpression of CD133 in rat C6 glioma cells leads to significant reluctance to undergo apoptosis from camptothecin and doxorubicin. Although p53 was upregulated in CD133-overexpressing glioma cells treated with DNA-damaging agents, apoptosis seems to be p53 independent. At least one ABC transporter, rat P-glycoprotein/ABCB1, was upregulated by 62% in CD133(+) cells with a corresponding increase in activity. Thus, the combination of higher P-glycoprotein mRNA transcription and elevated transporter activity seems to contribute to the protection from cytotoxic reagents. In conclusion, previous investigators have reported that resilient cancer stem cells coexpress CD133 and ABC transporters with increased reluctance toward apoptosis. Our data suggest that CD133 may contribute to the observed resistance to apoptosis of CD133(+) cancer stem cells.

Amonafide, a topoisomerase II inhibitor, is unaffected by P-glycoprotein-mediated efflux

Over-expression of P-glycoprotein (Pgp+) has been related to resistance to classical Topo II inhibitors used in the treatment of AML and is common in patients with poor-prognosis, such as those with secondary AML (sAML). Since clinical trials with amonafide, a unique ATP-independent Topo II inhibitor, in combination with cytarabine, have shown significant efficacy for remission induction in patients with sAML, we compared the cytotoxic effect of amonafide (amonafide l-malate, Xanafide) to the classical Topo II inhibitors (daunorubicin, doxorubicin, idarubicin, etoposide, and mitoxantrone) in K562 leukemia cells and in the MDR subline, K562/DOX. Pgp expression was found to be approximately 6.5-fold greater in K562/DOX and causes the rapid efflux of these drugs from the leukemia cell. As a consequence, the LC(50) values for the classical Topo II inhibitor drugs tested were each increased up to 3 log units. A similar result was also observed in murine P388 and P388/ADR leukemia cells. Addition of cyclosporin A reversed K562/DOX resistance for the classical Topo II inhibitors, decreasing their LC(50) values to the levels observed with wild type cells but had no effect on amonafide potency in Pgp+ or wild type cells. Further examination of amonafide in bidirectional Caco-2 and MDR1-MDCK models confirmed that amonafide is neither a substrate nor inhibitor of Pgp. These observations suggest that amonafide is a promising therapeutic candidate directed toward bypassing this common mechanism of drug resistance encountered in the treatment of patients with AML, and possibly in other resistant hematological malignancies as well.

Partial circumvention of P-glycoprotein-mediated multidrug resistance by doxorubicin-14-O-hemiadipate

Previously, we have reported partial circumvention of P-glycoprotein (Pgp)-associated resistance to doxorubicin (Dox) in MCF7/R human breast carcinoma and P388/R murine leukemia cell lines by doxorubicin-14-O-hemiadipate (H-Dox) [Povarov L.S. et al. (1995) Russian J. Bioorganic Chemistry 21: 797-803]. We felt that these changes were due to alterations in the cellular pharmacokinetics of the analog in multidrug (MDR) resistant cells, as compared to that of Dox. To address this hypothesis, we performed comparative studies of the accumulation, retention and intracellular localization of H-Dox and Dox in Dox-sensitive murine leukemia cell line P388/S and its Dox-selected. Pgp-positive drug resistant P388/R subline. These studies were performed in the presence or absence of cyclosporin A (CsA), a competitive inhibitor of Pgp. Flow cytometric analysis revealed significant differences in Dox and H-Dox accumulation in P388/R cells when compared to P388/S cells. In P388/R versus P388/S cells, there was a 38-fold decrease in Dox accumulation, but only a 5-fold decrease in H-Dox accumulation, indicating over a 7-fold increase in H-Dox buildup in resistant cells. CsA did not affect uptake or retention of either drug by sensitive cells. However, coincubation with CsA resulted in a 54-fold increase in Dox accumulation and only a 5-fold increase in H-Dox uptake in P388/R cells, restoring anthracycline levels in P388/R to 100% of that found in P388/S cells. Once internalized by the resistant cells, H-Dox was retained better than Dox regardless of presence or absence of CsA. Confocal microscopic analysis revealed the presence of H-Dox but no Dox in cellular nuclei of P388/R cells. Thus, increased activity of H-Dox toward P388/R cells was correlated with its enhanced ability to enter and be retained in these cells, and also with redistribution of H-Dox into the nuclei of the resistant cells as compared to Dox. Overall, our findings support our initial hypothesis and provide evidence that H-Dox, a 14-O-hemiadipate of doxorubicin, is affected by Pgp-mediated MDR to a lesser extent than parental Dox due to changes iin the cellular pharmacokinetics of the analog.

In vivo model systems in P-glycoprotein-mediated multidrug resistance

In this article we review the in vivo model systems that have been developed for studying P-glycoprotein-mediated multidrug resistance (MDR) in the preclinical setting. Rodents have two mdr genes, both of which confer the MDR phenotype: mdr 1a and mdr 1b. At gene level they show strong homology to the human MDR1 gene and the tissue distribution of their gene product is very similar to P-glycoprotein expression in humans. In vivo studies have shown the physiological roles of P-glycoprotein, including protection of the organism from damage by xenobiotics. Tumors with intrinsic P-glycoprotein expression, induced MDR or transfected with an mdr gene, can be used as syngeneic or xenogenic tumor models. Ascites, leukemia, and solid MDR tumor models have been developed. Molecular engineering has resulted in transgenic mice that express the human MDR1 gene in their bone marrow and in knockout mice missing a murine mdr gene. The data on pharmacokinetics, efficacy, and toxicity of chemosensitizers of P-glycoprotein in vivo are described. Results from studies using monoclonal antibodies directed against P-glycoprotein and other miscellaneous approaches for modulation of MDR are mentioned. The importance of in vivo studies prior to clinical trials is being stressed and potential pitfalls due to differences between species are discussed.

Tyrosine and phenylalanine restriction sensitizes adriamycin-resistant P388 leukemia cells to adriamycin

Cancer chemotherapy frequently fails, because tumors develop multiple drug resistance (MDR). Pharmacological efforts to reverse this MDR phenotype and sensitize resistant tumor cells have utilized verapamil (VER) to inhibit p-glycoprotein function and buthionine sulfoximine (BSO) to inhibit glutathione synthesis. Our previous results indicate that restriction of two amino acids, tyrosine (Tyr) and phenylalanine (Phe), may potentially suppress the MDR phenotype. These results show that in vivo Tyr and Phe restriction improves the therapeutic response of a metastatic variant of B16-BL6 (BL6) murine melanoma to adriamycin (ADR) and B16 melanoma to levodopa methyl ester. We examine whether in vitro limitation of Tyr and Phe suppresses ADR resistance of BL6 cells and whether Tyr-Phe modulation of the MDR phenotype is applicable to other tumor types, particularly P388 murine leukemia. Mechanisms underlying Tyr-Phe modulation of ADR resistance are examined in the presence of VER and BSO, singly and in combination. Our results indicate that in vitro Tyr and Phe restriction has no effect on BL6 resistance to ADR. However, Tyr and Phe restriction does increase the sensitivity of ADR-resistant P388 cells to ADR without affecting drug efflux, ADR uptake, or glutathione levels. In addition, this enhanced ADR sensitivity of P388 cells is even more pronounced in the presence of BSO. Suppression of ADR resistance in P388-resistant cells by Tyr and Phe restriction indicates that Tyr- and Phe-mediated modulation of the MDR phenotype is possible and that Tyr and Phe restriction may be useful as a potential adjuvant to effective cancer chemotherapy.

Characterization of the P-glycoprotein over-expressing drug resistance phenotype exhibited by Chinese hamster ovary cells following their in-vitro exposure to fractionated X-irradiation

Exposure of the Chinese hamster ovarian AuxB1 cell line in vitro to fractionated X-irradiation generated sublines designated DXR-10, which proved resistant to multiple drugs and overexpressed P-glycoprotein (Pgp), as judged by Western blotting using the C219 monoclonal antibody. Further characterization of these irradiated DXR-10 sublines has provided evidence for: (i) the expression of cross-resistance to gramacidin D, taxol, puromycin and Navelbine, but not to daunomycin or mitoxantrone; (ii) overexpression of the class I Pgp, as judged by Western blotting using the C494 monoclonal antibody; (iii) decreased accumulation of 3H-vincristine, which could be enhanced by verapamil addition; (iv) unaltered accumulation and subcellular distribution of adriamycin; (v) significantly increased rhodamine 123 accumulation in the presence of verapamil; (vi) plasma-membrane ultrastructural modifications resulting in a significantly increased surface area; (vii) numerous clonal karyotypic alterations, with abnormalities involving the long arm of chromosome 1 being consistently identified; (viii) a lack of overexpression of sorcin; (ix) increased total glutathione levels and overexpression of glutathione S-transferase pi. The fact that only certain of these features are considered characteristic of the 'classic' multidrug-resistant CHRC5 cell line supports our earlier proposal that exposure to fractionated X-irradiation results in the expression of a unique drug-resistance phenotype.

Therapeutic efficacy of combination of antitumor agent with AHC-52 against multidrug-resistant cells in the intravenously inoculated P388 leukemia model

To predict the clinical effect on leukemic disease of a combination regimen developed to circumvent multidrug resistance (MDR), we tested various antitumor agents in the presence and absence of AHC-52, a sensitizing agent for multidrug-resistant cells, in the i.v.-i.v. model of murine leukemia. In this model system, sensitive and resistant P388 murine leukemia cells are inoculated i.v. into mice, and each antitumor agent is injected via the i.v. route. Vincristine (VCR) had no effect on the survival of mice bearing VCR-resistant P388, a relatively poorly resistant subline, when given either as a single agent or in combination with AHC-52. In contrast, adriamycin (ADR) alone had no effect on these mice, but its combination with AHC-52 resulted in significant survival, the maximal value achieved being 196% (treated mice/control animals, T/C). Etoposide (VP-16) strongly enhanced survival, even when used alone, and this effect was markedly potentiated by AHC-52. Combination of any antitumor drug with AHC-52 was ineffective in mice bearing ADR-resistant P388, a highly resistant subline. On the other hand, AHC-52 strongly augmented the therapeutic efficacy of these antitumor agents in mice bearing the sensitive parent P388 leukemia, producing some curative effects. On the basis of these results, the feasibility of this type of combination therapy is discussed.