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Characterization of four drug-resistant P388 sublines: resistance/sensitivity in vivo, resistance-and
I Fichtner1, U Stein, J Hoffmann
1Max-Delbrück-Center of Molecular Medicine, Berlin, Germany.
Abstract:
It was the aim of this study to compare drug-resistant sublines of the murine P388 in relation to resistance markers, the resistant phenotype and immunogenicity. Resistance to drugs either belonging to the MDR type (Doxorubicin, Vincristine, Mitoxantrone) or to the non-MDR type (Methotrexate) was generated in vivo in order to mimic the clinical situation. All resistant sublines expressed the mdr1 gene and the p-glycoprotein determined on m-RNA level or immunohistochemically, while no expression was registered in the parent P388. The rhodamine 123 fluorescence as marker for the energy dependent drug efflux pump was decreased only in the MDR-sublines, while the parent P388 and the Methotrexate-resistant line retained 100% or 90% of the dye, respectively. This indicates that the rhodamine efflux is a more function-related marker for MDR than the mdr1 gene and the pgp. The in vivo characterization of the sublines as regards their sensitivity to cytostatics revealed a clear-cut cross-resistance to MDR drugs in the MDR-lines, while the Methotrexate resistant subline was only cross-resistant to Cytarabine. In each resistant subline collateral sensitivity to certain but different cytostatics was observed. Experiments to overcome resistance by concomitant treatment with the modulators Nifedipine, Verapamil, Cyclosporin A and Chloroquin led to only limited success. The sublines P388/Mitox, P388/Vinc and P388/MTX developed immunogenicity which was never registered in the original P388. Vaccination with lethally irradiated drug-resistant cells resulted in a substantial rejection of viable tumor cells of the same line. With the P388/Mitox and P388/Vinc also an over-cross immunization was possible. This generation of immunogenicity as a concomitant characteristic of resistance should be considered as therapeutic potential also in the treatment of clinical cancer.
Insights
Drug-resistant P388 cancer cell lines showed altered drug efflux and developed immunogenicity. This resistance and induced immunity offer potential for novel cancer therapies.
Area of Science:
- Cancer research
- Drug resistance mechanisms
- Immunotherapy
Background:
- Murine P388 leukemia models are used to study drug resistance.
- Multidrug resistance (MDR) is a significant challenge in cancer chemotherapy.
- Understanding resistance markers and phenotypes is crucial for developing effective treatments.
Purpose of the Study:
- To compare drug-resistant P388 sublines regarding resistance markers, phenotype, and immunogenicity.
- To investigate in vivo generated drug resistance mimicking clinical scenarios.
- To explore the therapeutic potential of drug resistance-induced immunogenicity.
Main Methods:
- Generation of in vivo drug-resistant P388 sublines (MDR and non-MDR types).
- Analysis of mdr1 gene and p-glycoprotein expression (mRNA and immunohistochemistry).
- Assessment of rhodamine 123 efflux as a functional marker for drug resistance.
- Evaluation of cross-resistance and collateral sensitivity to various cytostatics.
- Testing modulators (Nifedipine, Verapamil, Cyclosporin A, Chloroquin) to overcome resistance.
- Induction and assessment of immunogenicity in resistant sublines through vaccination.
Main Results:
- Resistant sublines expressed mdr1 gene and p-glycoprotein; parent P388 did not.
- Rhodamine 123 efflux was reduced in MDR sublines, indicating functional drug efflux.
- MDR sublines showed cross-resistance to MDR drugs; Methotrexate-resistant subline showed cross-resistance to Cytarabine.
- Limited success was achieved using modulators to overcome resistance.
- Resistant sublines (P388/Mitox, P388/Vinc, P388/MTX) developed immunogenicity.
- Vaccination with irradiated resistant cells led to tumor cell rejection; cross-immunization was observed.
Conclusions:
- Rhodamine efflux is a more functional marker for MDR than mdr1 gene/p-glycoprotein expression.
- Drug resistance in P388 sublines is associated with specific cross-resistance and collateral sensitivity patterns.
- Induced immunogenicity in drug-resistant cancer cells presents a potential therapeutic strategy.
- This dual characteristic of resistance and immunogenicity warrants further investigation for clinical cancer treatment.
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