ANTIINTEGRIN AVG3 SAV-RGD AS COMBINANT FOR DTIC WITH HUMAN AMELANOTIC SKIN MELANOMA

Abstract

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.