Subject(s)
Rhytidoplasty , Salivary Ducts , Aged , Constriction, Pathologic , Dilatation, Pathologic , Female , Humans , Male , Middle AgedSubject(s)
Asthma/drug therapy , Glucocorticoids/therapeutic use , Administration, Inhalation , Adolescent , Albuterol/administration & dosage , Child , Dose-Response Relationship, Drug , Drug Resistance/immunology , Female , Forced Expiratory Volume , Glucocorticoids/administration & dosage , Humans , Male , Theophylline/administration & dosageABSTRACT
We selected two drug resistant variants of the MCF7 human breast cancer cell line by chronic in vitro exposure to doxorubicin (MCF7/D40 cell line) and mitoxantrone (MCF7/Mitox cell line), respectively. The cell lines are similar in growth characteristics including doubling time, DNA synthetic phase and cell size. Resistance to mitoxantrone conferred only partial resistance to doxorubicin; whereas resistance selected for doxorubicin appeared to confer complete resistance to mitoxantrone. Both agents selected for cross resistance to the Vinca alkaloids. MCF7/D40 cells display a classic-multi-drug resistance phenotype with expression of P-glycoprotein, decreased drug accumulation relative to the parental line and reversal of drug accumulation and drug resistance by verapamil. MCF7/Mitox cells likewise display resistance to multiple drugs, but in contrast to MCF7/D40 cells do not express P-glycoprotein by immunoblot or RNA blot analysis. Net drug accumulation in MCF7/Mitox cells was decreased relative to the parental cells but there was no selective modulation of drug accumulation or in vitro drug resistance by the addition of verapamil. Efflux of mitoxantrone was enhanced in both the MCF7/D40 and MCF7/Mitox cell lines relative to the MCF7/S cell line. We conclude that the two drug resistant cell lines have different mechanisms of decreased drug accumulation.
Subject(s)
Antineoplastic Agents/pharmacology , Doxorubicin/metabolism , Drug Resistance/physiology , Membrane Glycoproteins/analysis , Mitoxantrone/pharmacology , ATP Binding Cassette Transporter, Subfamily B, Member 1 , Biological Transport , Breast Neoplasms , Cell Division/drug effects , Cell Line , Dose-Response Relationship, Drug , Doxorubicin/pharmacology , Female , Humans , KineticsABSTRACT
We present data describing a human myeloma cell line (8226/LR-5) selected for resistance to melphalan which exhibits a 7-fold level of resistance to melphalan and is partially cross-resistant to other bifunctional alkylators and X-irradiation. Melphalan resistance is relatively unstable with a decrease in resistance observed within 17 weeks in the absence of drug. The resistance observed in this cell line is not mediated by reduced intracellular melphalan accumulation. DNA interstrand cross-linking at equivalent intracellular drug accumulation is significantly reduced in the resistant subline. Whether this reduction is the result of a decrease in the formation of this lesion or to an increased rate of removal of the lesion remains to be determined. Growth characteristics and cell cycle kinetics, including S phase, were similar between sensitive and resistant cell lines. Intracellular nonprotein thiols were found to be significantly elevated in the resistant 8226/LR-5 cells; as cells revert or lose resistance, intracellular nonprotein sulfhydryl levels decline. Prior treatment of the cells with buthionine sulfoximine significantly reduced nonprotein sulfhydryl levels and enhanced melphalan cytotoxicity in both the sensitive and resistant cell lines. Thiols appear to play a role in mediating melphalan resistance.
Subject(s)
Melphalan/metabolism , Multiple Myeloma/pathology , Alkylating Agents/metabolism , Buthionine Sulfoximine , Cell Survival , DNA, Neoplasm/analysis , Drug Resistance , Glutathione/metabolism , Humans , Karyotyping , Methionine Sulfoximine/analogs & derivatives , Methionine Sulfoximine/metabolism , Multiple Myeloma/genetics , Multiple Myeloma/metabolism , Myeloma Proteins/analysis , Tumor Cells, Cultured/metabolism , Tumor Cells, Cultured/pathology , Tumor Cells, Cultured/radiation effectsABSTRACT
Verapamil reversed resistance to doxorubicin in a human multiple myeloma cell line selected for multiple drug resistance. The drug-resistant cell line 8226/DOX40 is known to have reduced intracellular drug accumulation associated with the overexpression of P-glycoprotein when compared to the sensitive parent cell line 8226/S. Verapamil alone was minimally cytotoxic in both cell lines, but reversed doxorubicin resistance in a dose-related manner in 8226/DOX40. A similar dose-response relationship was observed for verapamil in increasing net intracellular doxorubicin accumulation. This increased net accumulation was secondary to block of enhanced doxorubicin efflux by verapamil from resistant cells. In contrast, verapamil did not alter initial doxorubicin accumulation over the first 60 s when incubated with resistant cells. Addition of verapamil to the 8226/DOX40 cells enhanced the formation of doxorubicin-induced DNA single strand breaks, double strand breaks, and DNA-protein cross-links. Verapamil had no effect on these lesions in the drug-sensitive cells. In addition, verapamil did not affect chemotherapeutic cytotoxicity or transport in the drug-sensitive cell line. Verapamil appears to reverse doxorubicin resistance in this human myeloma cell line by blocking enhanced drug efflux, leading to increased drug accumulation and enhanced DNA damage.