Ganglioside GM2 levels in human melanoma cells: inverse correlation with lysosomal beta-hexosaminidase A activity.

GM2 is usually significantly elevated in human melanoma cells. The lysosomal hydrolase beta-hexosaminidase A (Hex A), is an isoenzyme required for terminal GalNAc hydrolysis from intact GM2 to GM3. The objective of the present studies is to determine if the elevated levels of gangliosides, particularly GM2, correlate with the activity of Hex A in cultured melanoma cells. The Hex A activity in 13 melanoma cell lines ranged from 26%-88.3% There was a inverse correlation between GM2 nmole/g and Hex A activity (r = -0.48; p less than 0.003). An inverse correlation (p less than 0.03) occurred between GD2 nmole/g and Hex A activity. There was an inverse correlation (r = -0.53; p less than 0.05 and r = -0.51; p less than 0.05, respectively) between the ratio of substrate/product (GM2/GM3) and (GD2/GD3) and Hex A activity. These results indicate that the level of GM2 in melanoma is inversely correlated with the level of activity of Hex A.