UROC1 and skin neoplasm: Interestingly, this conversion does not occur in the skin, as UROC1 is highly expressed in the liver (median transcripts per million (TPM) = 75.6 in GTEx) but not in the skin (median TPM = 0.01) (The GTEx Consortium 2020) leading to trans-urocanate accumulation in the skin and thus to reduced vitamin D level but also protection from skin cancer (Fig. 3c).