Differential involvement of glutathione S-transferase mu 1 and multidrug resistance protein 1 in melanoma acquired resistance to vinca alkaloids.

On account of its extreme intrinsic resistance to apoptosis and of its strong ability to become chemoresistant after a primary response to drugs, malignant melanoma (MM) is still a therapeutic challenge. We previously showed that glutathione S-transferase mu 1 (GSTM1) acts in synergy with multidrug resistance protein 1 (MRP1) to protect GSTM1-transfected human CAL1 melanoma cells from toxic effects of vincristine (VCR). Herein, we investigated the role of these proteins in the acquired resistance of CAL1 cells to vinca alkaloids (VAs). Resistant lines were established by continuous exposure (>1 year) of parental CAL1-wt cells to VCR, vindesine (VDS), or vinorelbine (VRB): CAL1R-VCR, CAL1R-VDS, CAL1R-VRB, respectively. All resistant lines displayed more than 10-fold increase in resistance to their selection VA, and specifically expressed GSTM1. Suggesting a direct interaction between this protein and VAs, each VA specifically decreased the GSTM1-mediated glutathione conjugation activity in cell lysates. Curcumin (GSTM1 inhibitor), BSO (glutathione synthesis inhibitor), and MK571 (MRP1 inhibitor) considerably reversed the acquired resistance to VCR and VDS, but not to VRB. Microarray data analysis revealed similar gene expression patterns of CAL1R-VCR and CAL1R-VDS, and a distinct one for CAL1R-VRB. These data suggest a differential involvement of GSTM1 and MRP1 in acquired resistance to VAs. A coordinated expression and activity of GSTM1 and MRP1 is required to protect CAL1 cells from VCR and VDS, while the simple expression of GSTM1 is sufficient, possibly by a direct drug/protein interaction, to confer resistance against VRB.

Irradiation of skin and contrasting effects on absorption of hydrophilic and lipophilic compounds.

Increasing legal requirements for risk assessment and efficacy testing in the dermo-cosmetic field have led to the development of alternative test methods. In this study, the porcine skin model was chosen to test the effect of irradiation on the penetration habits of UV filters and caffeine. For decades, the pig has been recognized as an experimental animal in biomedical research thanks to its morphological and physiological similarities to humans. In this study, we wanted to investigate the effect of UV irradiation on the absorption of octocrylene (OC) and benzophenone-3 (B3) sunscreens used under those circumstances and a model hydrophilic molecule, caffeine (Caf). These particular compounds were chosen due to their different lipophilic profiles. The percutaneous penetration of the two UV filters and Caf was studied after two simulated solar radiation doses of 61.4 kJ m(-2). After irradiation simulation, the total absorbed dose was increased for OC while for B3 and Caf it was lower. Thus, modifications in percutaneous absorption have been observed, and it appears that UV could play a crucial role in this process. Moreover, it has been observed that the lipophilic profile of the studied compounds affects percutaneous penetration when irradiated.