Expression of asparagine synthetase and glutamine synthetase genes in human skin melanoma cells and their sensitivity to L-asparaginase

Background. L-asparaginase is an enzyme used in clinical practice for the treatment of hematological malignancies, it’s antiproliferative effect has been reported against certain solid tumors. To improve the effectiveness of L-asparaginase, there is a need to search for biochemical markers that can be used to predict the sensitivity of tumors to the enzyme. The level of ASNS or GLUL gene expression in tumor cells has been reported as such predictive marker, but for some tumors, including melanoma, there is limited data on the relationship between the expression levels of these genes and sensitivity to L-asparaginase.

Aim. To determine the relationship between the sensitivity of melanoma cells to L-asparaginase and the expression levels of the ASNS and GLUL genes.

Methods. Cytotoxicity of 35 melanoma cell lines was evaluated using the MTT test. Gene expression levels were studied using real-time RT-PCR. The relationship between expression and sensitivity was determined using the Spearman correlation coefficient.

Results. The IC₅₀ values of L-asparaginase for melanoma lines ranged from 0.01 to 199.91 IU/ml, with a median of 2.96 IU/ml and a sample mean of 16.95 IU/ml. The expression level of the ASNS gene ranged from 0.02 to 7.38 (median — 0.4, arithmetic mean — 0.98), and the GLUL gene ranges from 0.06 to 14.78 (median — 0.64, arithmetic mean — 1.41). The correlation between IC₅₀ and the expression level of the ASNS gene was confirmed by the Spearman correlation coefficient, which was 0.751. No correlation was found between IC₅₀ and the expression level of the GLUL gene (Spearman correlation coefficient was 0.077).

Conclusions. A direct relationship was found between the resistance of melanoma cells to L-asparaginase and the level of ASNS gene expression in them. A similar relationship for the GLUL gene has not been confirmed.