Ganglioside GM3:GD3 ratio as an index for the management of melanoma

This report evaluates the relevance of the ratio of the melanoma-associated ganglioside, GD3, and its precursor, GM3, to prognosis and management of Stage II disease. Tumor biopsy specimens from 42 melanoma patients were examined for the ratio and found that GD3 and GM3 constitute 80% of the total lipid bound sialic acids (LBSA) of melanoma. Although the ratio of GM3:GD3 in melanocytes, the progenitors of melanoma, is 19:1 (based on %LBSA), it ranged from 15:1 to 1:5 in tumor biopsy specimens. Patients are categorized into three groups based on their GM3:GD3 ratio (%LBSA) of tumor tissues as Group I (ratio ranged from 15:1 to 1.5:1) (10 of 42), Group II (1.4:1 to 1:1.4) (13 of 42), and Group III (1:1.5 to 1:5) (19 of 42). When the overall survival of patients from the onset of Stage II disease was evaluated among different groups, patients belonging to Group I survived significantly longer than patients of Group II (P = 0.02) and Group III (P = 0.01). Interestingly, Group III expressed immunogenic gangliosides (GD2, GM2, and O-AcGD3) better than the other groups and may benefit more from therapies targeted against these gangliosides antigens. The results of this study indicate that GM3:GD3 ratio is an unusual but well-defined biochemical criteria that may be useful for prognosis and therapeutic management of the disease. Therefore, we propose a routine analysis of the GM3:GD3 ratio of tumors excised after surgery. Screening the ratio is feasible since melanoma expresses a simple profile of gangliosides unlike other forms of cancer.