(A) An immunoblot showing different expression levels of ASS1 and CAD in two different cancer cell lines of melanoma. (B) Melanoma cells with ASS1 downregulation have a significant increase in pyrimidine levels as measured by LC/MS, n≥3. (C) Melanoma cells with ASS1 downregulation have a significant increase in total Uracil, n=4. (D) Melanoma cells with ASS1 downregulation have a significant increase in proliferation as measured by MTT assay, n=2. (E) Immunoblots of melanoma cells for ASS1 levels following transduction with either ASS1 over expression construct or with shASS1. (F) Proliferation assays showing a significant decrease in proliferation following ASS1 overexpression in melanoma using MTT, n=3. (G) Crystal violet quantification for melanoma cells following transduction with shASS1 demonstrating increase in proliferation, n=3. (H) LC/MS measurements of pyrimidine levels showing a significant increase following the use of shASS1 in melanoma cells, n≥3. (I) Left panel- Total uracil levels are decreased significantly in melanoma cells with ASS1 over expression and increased in melanoma cells with shASS1- Right panel, n≥2. (J) Significant increase in proliferation of melanoma cells by dNTP’s after ASS1 overexpression, n=3. In all panels, error bars represent SER.