Introduction. The avB3 integrin (cell adhesion molecule) plays the role of the receptor, including, metalloproteinase matrix 2, involved in melanoma metastasis. We have been characterized as an antimelanoma original anti-integrin agent SAV-RGD (lyo-SAV-RGD), specifically binding to melanoma cells by means of the Arg-Gly-Asp tripeptide. More significant inhibited effect was obtained on amelanotic human skin melanoma MeWo. Accordingly, the experimental evaluation of the effectiveness of lyo-SAV-RGD in combination with the «gold» standard of antimelanoma chemotherapy dacarbazine (DTIC) is relevant.
Objective: a comparative study of the combination of DTIC+lyo-SAV-RGD on the model of pigmented melanoma of human skin MeWo.
Material and methods. The model of human skin melanoma MeWo in vivo/in vitro: s.c. xenografts in Balb/c nude mice, sensitive to DTIC cell line MeWo and obtained prospectively stable subline MeWo/DTIC was used. In vitro experiments the time of cell doubling in both models was determined and the individual range of agent concentrations was studied. Therapy with DTIC+lyo-SAV-RGD were administered in simultaneously sequentially, first the single 150 mg/kg DTIC, then lyo-SAV-RGD 9-fold course in the total dose of 900 mg/kg (the first dose is doubled). To control of the group with single dose 250 mg/kg of DTIC close to the maximum tolerated dose (MTD). All experiments were performed by standard methods using significant evaluation criteria and adequate statistical processing of the results (p<0.05).
Results. For MeWo and MeWo/DTIC cells with a certain prospectively identical doubling time of the doubling time of tumor cells (Tpot) at the level of 23.0±2.3 h and 23.1±1.8 h, DTIC was practically non-cytotoxic, IC50=410±4 g/ml and IC50=860±27 g/ml (IC50<1o0 g/ml). However, the absolute value of the active concentrations of DTIC was significantly less known for murine pigmented melanoma, 1200-1400 g/ ml. Lyo-SAV-RGD, on the contrary, was cytotoxic for both melanoma variants at the same level, IC50=100±3.1 g/ml, and in the range from 1,0 to 100 g/kg caused cell death in direct dependence on the concentration. On s.c. MeWo xenografts DTIC at the dose of 250 mg/kg was effective at T/ C<30% (criterion T/C<42%) with partial death of mice from toxicity. The combination of DTIC+lyo-SAV-RGD showed an identical effect regardless of dose reduction by 40%, T/C=38% (p=0.001).
Conclusion. A comparative study on the model of human skin melanoma MeWo revealed in vitro the absence of significant cytotoxicity of DTIC and at the same time cytotoxicity of anti-integrin avB3 lyo-SAV-RGD for MeWo and MeWo/DTIC cells. On xenografts MeWo combined therapy DTIC+lyo-SAV-RGD with dose reduction cytostatic 40% made it possible to obtain the maximum antitumor effect (T/C=38% vs 30%) with improved tolerability. The obtained data suggest that the introduction of anti-integrin avB3 into the scheme with DTIC is advisable to increase the selectivity of cytotoxic action of cytostatics.
Inhibition of lipid synthesis by clofibrate: comparative study of human skin, rat skin, and rat liver in vitro
