Figure 1.

Cultured cancer cell lines lack de novo cysteine synthesis capacity. A-C, Analysis of de novo cysteine synthesis in cultured NSCLC, SCLC, PDAC, and HCC cell lines with ¹³C₃-serine tracing. Cell lines were incubated with ¹³C₃-serine containing media for 4 hours, followed by analysis of the fraction labeling in A serine, B cystathionine and C cysteine. Data are presented as mean ± SD and N=3 biological replicates for each cell line. D, Immunoblotting for the transsulfuration enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). HSP90 was used for the loading control and HepG2 was used for relative comparison between different membranes. Ser, serine; Cth, cystathionine; Cys, cysteine.