Given that (i) IDO1 expression is elevated in RCC (Figure 1), (ii) kynurenine pathway metabolites are increased in RCC [7], and (iii) the immunomodulatory agent IFNα can induce IDO1 expression in RCC cells (Figure 5), we conducted an in vivo study using RENCA cells in syngeneic Balb/c mice treated with IFNα and MTH-trp. Here, IDO1 is linked to renal cell carcinoma.