GCLC and neoplasm: Second, the SLC38A5-mediated delivery of Se-Met into tumor cells potentiates the activity of the transcription factor Nrf2, which not only increases the ability of the tumor cells to synthesize glutathione by upregulating the expression of GCLC and GCLM to promote the first step in the glutathione synthetic pathway, but also induces the expression of the transporter SLC7A11 which provides cysteine (in the form of cystine), the rate-limiting amino acid for glutathione synthesis in tumor cells.