Background: Anthracycline-containing regimens have given controversial clinical results in CLL. Therefore, we explored the in vitro behavior of CLL B-cells after exposure to the compounds included in the most frequently used combination therapy regimen (CEOP).
Methods: A 4-day MTT colorimetric assay was used in vitro to test the effect of CEOP regimen drugs, either alone or in combination, on CLL B-cells. All drugs but mafosfamide, tested in place of cyclophosphamide, were used at concentrations corresponding to the in vivo dosage employed in the CEOP regimen. Chlorambucil was also studied since it represents the standard treatment for this disease.
Results: Epirubicin, prednisone and vincristine displayed a cytotoxic effect in 15, 13 and 4 out of 30 samples, respectively. Combinations of the same drugs showed a synergistic effect in 6 out of 13 assays. A cytotoxic effect of chlorambucil was detected in 2 out of 5 responders to the combination of CEOP regimen drugs, and in 3 out of 7 non responders. Mafosfamide induced a reduction in cell survival in 60-80% of the samples, depending on its concentration.
Conclusions: The MTT assay is suitable for evaluating the in vitro chemosensitivity of CLL B-cells to multidrug regimen compounds. In the present study 40% of samples were resistant to CEOP regimen components in vitro. The possible role of MTT in predicting the clinical response to the CEOP regimen should still be established by prospective in vitro and in vivo studies.