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Characterization of a new drug-resistant human myeloma cell line that expresses P-glycoprotein
Abstract:
Multiple myeloma is a disease with a high initial chemotherapeutic response but virtually no cures due to emergence of drug resistance. A doxorubicin-resistant human myeloma cell line (8226/Dox) has been selected from the myeloma cell line RPMI8226 by continuously exposing cells to gradually increasing doses of doxorubicin. The resistant phenotype has been retained for over 2 months despite growth in drug-free medium. The resistant subline was cross-resistant to mitoxantrone, acronycine, etoposide, and vincristine. The 8226/Dox cell line remained sensitive to melphalan but acquired collateral sensitivity to dexamethasone. Intracellular doxorubicin accumulation, as measured by [14C]doxorubicin and high-performance liquid chromatography, was decreased by 54% at 1 h for 8226/Dox compared to the sensitive line. Efflux of doxorubicin was significantly greater in the resistant subline as compared to the sensitive parent cell line. Membrane analysis using immunoblotting techniques detected increased expression of the integral membrane protein P-glycoprotein (Mr 170,000) in the resistant subline. Cytogenetic analysis of 8226/Dox revealed a 7q-anomaly not seen in the parent cell line. No double minutes or homogeneously staining regions were observed. The drug sensitivity/resistance pattern of the resistant cell line correlates well with clinical observations indicating the potential of this cell line as a model for resistance in multiple myeloma.
Insights
A new multiple myeloma cell line (8226/Dox) exhibits resistance to doxorubicin and cross-resistance to several chemotherapy drugs. This model shows potential for studying drug resistance in multiple myeloma.
Area of Science:
- Oncology
- Pharmacology
- Cell Biology
Background:
- Multiple myeloma has a high initial response to chemotherapy but lacks cures due to drug resistance.
- Understanding the mechanisms of drug resistance is crucial for developing effective treatments.
Purpose of the Study:
- To develop and characterize a novel doxorubicin-resistant human myeloma cell line.
- To investigate the drug sensitivity profile and underlying mechanisms of resistance in this new cell line.
Main Methods:
- Selected a doxorubicin-resistant subline (8226/Dox) from RPMI8226 myeloma cells.
- Assessed cross-resistance and collateral sensitivity to various chemotherapeutic agents.
- Quantified intracellular doxorubicin accumulation and efflux using [14C]doxorubicin and HPLC.
- Analyzed P-glycoprotein expression via immunoblotting and performed cytogenetic analysis.
Main Results:
- The 8226/Dox cell line demonstrated resistance to doxorubicin and cross-resistance to mitoxantrone, acronycine, etoposide, and vincristine.
- The resistant subline showed retained sensitivity to melphalan and acquired collateral sensitivity to dexamethasone.
- Reduced intracellular doxorubicin accumulation and increased efflux were observed in 8226/Dox cells.
- Increased P-glycoprotein expression and a 7q-anomaly were detected in the resistant subline.
Conclusions:
- The 8226/Dox cell line serves as a valuable model for studying multidrug resistance in multiple myeloma.
- The observed drug resistance patterns correlate with clinical observations, highlighting the model's relevance.
- Further research using this model can elucidate resistance mechanisms and inform therapeutic strategies.