Collagen Prolyl Hydroxylases Are Bifunctional Growth Regulators in Melanoma

Appropriate post-translational processing of collagen requires prolyl hydroxylation, catalyzed by collagen prolyl 3-hydroxylaseand collagen prolyl 4-hydroxylase, and is essential for normal cell function. Here we have investigated the expression, transcriptional regulation, and function of the collagen prolyl 3-hydroxylaseand collagen prolyl 4-hydroxylase families in melanoma. We show that the collagen prolyl 3-hydroxylasefamily exemplified by Leprel1 and Leprel2 is subject to methylation-dependent transcriptional silencing in primary and metastatic melanomaconsistent with a tumor suppressor function. In contrast, although there is transcriptional silencing of P4HA3 in a subset of melanomas, the collagen prolyl 4-hydroxylase family members P4HA1 , P4HA2 , and P4HA3 are often overexpressed in melanoma, expression being prognostic of worse clinical outcomes. Consistent with tumor suppressor function, ectopic expressionof Leprel1 and Leprel2 inhibits melanomaproliferation, whereas P4HA2 and P4HA3 increase proliferation, and particularly invasiveness, of melanomacells. Pharmacological inhibition with multiple selective collagen prolyl 4-hydroxylase inhibitors reduces proliferation and inhibits invasiveness of melanomacells. Together, our data identify the collagen prolyl 3-hydroxylaseand collagen prolyl 4-hydroxylase families as potentially important regulators of melanomagrowth and invasiveness and suggest that selective inhibition of collagen prolyl 4-hydroxylase is an attractive strategy to reduce the invasive properties of melanomacells.