P-glycoprotein expression and in vitro reversion of doxorubicin resistance by verapamil in clinical specimens from acute leukaemia and myeloma.

The expression of the P-glycoprotein which is associated with the development of multidrug resistance in various cell lines was investigated in 87 fresh acute leukaemia and multiple myeloma samples using the specific mouse monoclonal antibody MRK16 in an indirect immunofluorescence assay. Considering a 10% positive cell cut-off value, a heterogeneous expression of P-glycoprotein was observed in 5/22 (22.7%) de novo acute leukaemias, 7/22 (31.8%) relapse or secondary acute leukaemias, 14/27 (51.8%) acute transformation of myeloproliferative or myelodysplastic syndromes and 5/16 (31.2%) multiple myelomas. This expression was not associated with specific cytogenetic abnormalities, especially alterations of chromosome 7q. Verapamil, a calcium channel blocker, has been demonstrated to circumvent the multidrug resistance in cell lines, possibly by interfering with P-glycoprotein function. Using the microculture tetrazolium assay, verapamil was demonstrated to increase the sensitivity of fresh leukaemic or myeloma cells to doxorubicin in 19/43 (43.1%) samples. The doxorubicin IC50 level and the capacity of verapamil to increase the sensitivity of blast cells to doxorubicin in vitro did not correlate with the expression of P-glycoprotein. We conclude that high non-cytotoxic concentrations of verapamil were able to increase the in vitro doxorubicin sensitivity of fresh acute leukaemia and myeloma cells without detectable expression of the P-glycoprotein.

Diagnostic yield of a one sample immunochemical test at different cut-off values in an organised screening programme for colorectal cancer.

BACKGROUND: Quantitative immunochemical faecal occult blood tests have become the recommended tests for colorectal cancer screening. The aim of this study was to complete our knowledge on the performance of one of the quantitative immunochemical tests available, FOB-Gold, and to propose a possible strategy for an organised screening programme. PATIENTS AND METHODS: Within the French organised screening programme, 23,231 average-risk individuals, aged 50-74 performed both a 3-day Hemoccult test and a 1-day FOB-Gold test. Performances of the immunochemical test were evaluated at different cut-off levels. RESULTS: The positivity rate for the Hemoccult was 2.1% and for the FOB-Gold varied between 4.6% (cut-off value of 100 ng/mL, the lowest studied cut-off) and 2.1% (cut-off value of 352 ng/mL). The number of colonoscopies decreased with increasing cut-off values by 21.5% (150 ng/mL), 35.4% (200 ng/mL) and 53.3% (352 ng/mL). The corresponding miss rate for CRC was respectively 6.4%, 11.1% and 22.2%, and for advanced adenoma respectively 16.3%, 29.2% and 43.6%. Compared with the reference cut-off for the FOB-Gold (100 ng/mL) the miss rate for Hemoccult was 53% for CRC and 77% for advanced adenoma. CONCLUSION: The study suggests that in countries with colonoscopy facilities compatible with a screening test positivity rate of up to 5%, use of a 1-day test with a cut-off value between 100 and 150 ng/mL could be the recommended strategy. Further increasing the cut-off value up to the same positivity rate as Hemoccult could be used in areas with limited access to colonoscopy.

Comparison between a guaiac and three immunochemical faecal occult blood tests in screening for colorectal cancer.

BACKGROUND: The aim of this study was to compare the performance of the guaiac-based faecal occult blood test (G-FOBT), with that of three immunochemical faecal occult blood tests (I-FOBT) which allow automatic interpretation. PATIENTS AND METHODS: Under the French organised screening programme, 85,149 average-risk individuals aged 50-74 participating in the third screening round, performed both the G-FOBT (Hemoccult-II test) and one of the I-FOBTs: FOB-Gold, Magstream and OC-Sensor. RESULTS: Given the chosen threshold, the positivity ratio between the different I-FOBTs and the G-FOBT was 2.4 for FOB-Gold, 2.0 for Magstream and 2.2 for OC-Sensor (P=0.17). The three I-FOBTs were superior to the G-FOBT for colorectal cancer (CRC) detection. The ratios for detection rates were 1.6 (FOB-Gold), 1.7 (Magstream) and 2.1 (OC-Sensor) (P=0.74). For non-invasive CRC they were, respectively, 2.5, 3.0 and 4.0 (P=0.83) and for advanced adenomas 3.6, 3.1 and 4.0 (P=0.39). CONCLUSIONS: This study provides further evidence that I-FOBT is superior to G-FOBT. None of the three I-FOBTs studied appeared to be significantly better than the others.

Sufficient levels of quinine in the serum circumvent the multidrug resistance of the human leukemic cell line K562/ADM.

Reversal of multidrug drug resistance (MDR) has been achieved in vitro by a variety of agents including verapamil, quinidine, cyclosporine A, and amiodarone. The toxicity of these agents precludes the achievement of sufficient levels in the serum to circumvent efficiently the MDR in vivo. The authors previously demonstrated that quinine, the widely used antimalarial agent, is able to reverse primary resistance of rat colon cancer cells to anthracyclines. In this report, the efficiency of quinine formiate in reversing the doxorubicin (ADM) (Adriamycin, Adria Laboratories, Columbus, OH) resistance of the well-defined MDR human leukemic cell line K562/ADM was demonstrated. In culture medium, quinine is slightly less effective than verapamil in increasing the cytotoxicity and uptake of ADM when both drugs are used at the same concentration. A nontoxic dose of 5 micrograms/ml is necessary to reverse the MDR in K562/ADM cells. In patients receiving quinine formiate in a continuous intravenous infusion, a significant correlation (r = 0.84) was found between the serum levels of quinine and the ability of sera to increase ADM uptake in K562/ADM cells. When quinine is administered at a conventional dose (25 to 30 mg/kg/d), serum levels consistently reach more than 8 micrograms/ml without severe side effects; ear noises and vertigo are the dose-limiting side effects. At these concentrations, quinine induces a more than double increase in ADM uptake in K562/ADM cells. Pharmacokinetic data indicate that quinine should be administered 24 to 36 hours before anti-cancer drugs in clinical trials that test its efficiency as a modifier of MDR in human hematologic malignant neoplasms.

Quinine circumvents the doxorubicin resistance of a multidrug resistant human leukemic cell-line, K562/DXR.

Reversal of multidrug resistance (MDR) has been obtained in vitro by a variety of agents but clinical use of these resistance modifiers is hampered by their own toxicity. Quinine, the natural isomer of quinidine, is demonstrated to circumvent doxorubicin (DXR) resistance of an MDR human leukemic cell-line, K562/DXR. In culture medium, quinine (5 mu/ml or more) significantly increases cytotoxicity and accumulation of DXR in the resistant cells but not in the parental sensitive cells. When quinine is administered by continuous intravenous infusion in the doses conventionally used in chloroquino-resistant malaria (30 mg/kg/d), serum levels reach 8-11 micrograms/ml without prohibitive toxicity. Sera from quinine-treated patients enhance DXR uptake in K562/DXR cells in dose-dependent fashion. The conditions for the safe use of quinine as an MDR modifier in the treatment of refractory human hemopoietic malignancies are defined.