Using these measurements to extrapolate a 10-fold reduction of System L substrate amino acids and a 10-fold increase in kynurenine levels in IDO-expressing tumour environments at the same time, could create an environment whereby kynurenine levels would be significantly high enough to drive AHR activation as well as apply competitive pressure upon SLC7A5-mediated transport of essential amino acids. The gene discussed is AHR; the disease is neoplasm.