L-type calcium channel blockers reverse docetaxel and vincristine-induced multidrug resistance independent of ABCB1 expression in human lung cancer cell lines
ABSTRACT Multidrug resistance (MDR) of cancer cells to cytotoxic drugs significantly impedes chemotherapeutic treatment. The purpose of this study is to characterize docetaxel (DOC) or vincristine (VCR) selected A549 and H1299 non-small cell lung cancer (NSCLC) sublines that exhibit MDR phenotypes and followed by re-sensitization study. Although all drug resistant sublines showed cross-resistance to DOC, VCR, and doxorubicin (DXR), the expression of ATP-binding cassette (ABC) transporter B1 (ABCB1) gene was found to be strongly induced in DOC but not in VCR resistant A549 sublines by quantitative reverse transcription real-time polymerase chain reaction (qRT-PCR). In DOC and VCR resistant H1299 sublines, moderate expression of ABCB1 was detected. The levels of ABCB1 protein and efflux activities were further examined by immunoblotting and rhodamin-123 staining assay. The results showed that both ABC and non-ABC mediated MDR are existed. Furthermore, verapamil (VER), an inhibitor of ABCB1 and an L-type calcium channel blocker, is capable of reversing the resistance in all drug-resistant sublines independent of ABCB1 expression. Importantly, VER only sensitizes resistant sublines but has no effect on parental cancer cells. Other L-type calcium channel blockers, such as diltiazem (DIL) and nifedipine (NIF), also sensitize MDR sublines without interfering with ABCB1 activity but with lower efficacy than VER. Our data showed that in addition to ABCB1, calcium channel activity may play a crucial role in DOC- and VCR-acquired MDR. Therefore, inhibition of calcium influx may provide a new target to modulate MDR in chemotherapy.
- [show abstract] [hide abstract]
ABSTRACT: Docetaxel (DOC), a member of the taxane family of anticancer drugs, binds to tubulin and produces unnaturally stable microtubules that induce cell death. DOC is used clinically alone or in combination with other compounds to treat advanced stages of cancer. We have treated the human lung cancer cell lines A549 and H1299 and human cervical cancer HeLa cells with low concentrations of DOC to characterize the response of beta-tubulin isotypes and p53 genes. The relationship between p53 function and DOC, acting through a microtubule-based mechanism, was examined. We found that after 18-hr treatment with DOC, beta-tubulin gene transcription was enhanced in p53-null H1299 cells but not in A549 cells. Also, p53 RNA was strongly induced in the A549 cells. In addition, beta-tubulin levels also increased in the H1299 cells after the DOC treatment. Further demonstrating an association of DOC treatment with p53 and beta-tubulin, inhibition of p53 expression by interference RNA in A549 cells showed increasing beta-tubulin gene expression with DOC treatment. We also selected a clone from the H1299 cells that stably expressed p53, examined the beta-tubulin expression after DOC treatment and found an inhibition of beta-tubulin induction in these p53-expressing cells. Our data suggest that the initial response of cells to DOC treatment involves p53; alternatively, in the absence of p53, tubulins may be transactivated. Selection of the DOC-resistant A549 cells showed beta-tubulin expression was increased, in contrast to the initial response to the DOC treatment. From the initial and selection responses of beta-tubulin in cancer cells, it appears that there is a p53-associated beta-tubulin expression as a result of the DOC treatment.International Journal of Cancer 02/2006; 118(2):317-25. · 6.20 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: We optimized the modulation of drug resistance by the irreversible augmentation of cytotoxicity of coincubating vinblastine (VNB) with VP-16 and the reversible increase in cytotoxicity of coincubation of verapamil (VPL) with VNB and VP-16. VPL was administered as a loading dose (i.v.) (0.15 mg/kg) and then administered as a constant infusion (0.005 mg/kg) over 6 days. 24 h after verapamil, VNB 2 mg/m2 IVP was administered and followed 1 h later by a 5-day simultaneous continuous infusion of VP-16 (200 mg/m2/day) to seven pediatric patients (11 courses) with refractory malignancies. The mean age at treatment was 7.5 +/- 5.3 years, mean prior anthracycline dose (303 +/- 210 mg/m2) with a range of 0-606 mg/m2. Toxicity was limited to cardiac and hematological. The median nadir of the WBC was 900 at 14.5 +/- 0.5 days and platelet count 32,000 at 15.5 +/- 0.8 days. There were two episodes of bacterial sepsis both of which responded to i.v. antibiotics. Five of 11 courses resulted in first-degree block and one course in second-degree block. At Hour 120 of the VPL infusion the PR interval was 0.18 +/- 0.01 versus 0.13 +/- 0.01 at Hour 0 (P less than 0.0004). The ejection fraction by two-dimensional echocardiogram was not significantly different at Hour 0, 24, or 120 of the infusion (60.6 +/- 2.7 versus 52.7 +/- 5.1 versus 51.8 +/- 5.0%). The cardiac index was also not significantly different at Hour 0, 24, or 120 (4.39 +/- 0.2 versus 4.21 +/- 0.6 versus 3.91 +/- 0.5 liters/min/m2). The 15-min VPL level was 1954.5 +/- 391/ng/ml and steady state levels at Hour 24 and 120 of the infusion were 468.1 +/- 59 and 422.8 +/- 52 ng/ml, respectively. Two of 11 treatment courses resulted in hypotension secondary to inordinately high 24-h levels of VPL (1233 and 1263 ng/ml). These two episodes required inotropic support but did not require the discontinuation of VPL. There were 8 of 11 partial responses, the majority of which consisted of peripheral cytoreduction of leukemic blasts and one M-2A response in AML. The levels of VPL achieved in this study have been shown to augment the in vitro cytotoxicity of vinblastine and VP-16 to resistant cell lines. Further clinical studies are needed to determined the maximal-tolerated dose of VPL in a Phase I study and to examine its efficacy in selected relapsed pediatric patients.Cancer Research 03/1989; 49(4):1063-6. · 8.65 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Fifty-nine consecutive patients with clinical stage (cStage) I-III resectable small-cell lung cancer (SCLC) underwent surgery with adjuvant chemotherapy based on an in vitro sensitivity assay between April 1982 and March 1992. In 42 (71%) of these patients, a stable passage of cancer cells from resected specimens was possible and the sensitivity of these cultured SCLC cells to anticancer drugs was examined by the MTT method. In the sensitivity assay, vincristine (VCR) showed the most intense specific efficacy for SCLC, followed by cyclophosphamide (CPM) and cisplatin (CDDP). The 5-year survival rates for pathological stage (pStage) I, pStage II, and pStage III were 55%, 33%, and 23%, respectively. The 5-year survival of the patients with pStage III operated on in the first 5 years was 7% (1/14). On the other hand, 6 of the 16 pStage III patients (38%) operated on during the second 5-year period, who were generally treated with pre- and postoperative adjuvant chemotherapy combined with three drugs, survived over 5 years. In conclusion, these results suggest that combined modality therapy including surgery is necessary, and adjuvant chemotherapy combined with VCR, CPM, and CDDP may be useful in the treatment of Stage III SCLC disease, for the purpose of achieving a long-term survival with both a good performance status and quality of life for the patients.Surgery Today 02/2000; 30(2):127-33. · 0.96 Impact Factor