ABSTRACT
Appropriate post-translational processing of collagen requires prolyl hydroxylation, catalyzed by collagen prolyl 3-hydroxylase and 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-hydroxylase and collagen prolyl 4-hydroxylase families in melanoma. We show that the collagen prolyl 3-hydroxylase family exemplified by Leprel1 and Leprel2 is subject to methylation-dependent transcriptional silencing in primary and metastatic melanoma consistent 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 expression of Leprel1 and Leprel2 inhibits melanoma proliferation, whereas P4HA2 and P4HA3 increase proliferation, and particularly invasiveness, of melanoma cells. Pharmacological inhibition with multiple selective collagen prolyl 4-hydroxylase inhibitors reduces proliferation and inhibits invasiveness of melanoma cells. Together, our data identify the collagen prolyl 3-hydroxylase and collagen prolyl 4-hydroxylase families as potentially important regulators of melanoma growth and invasiveness and suggest that selective inhibition of collagen prolyl 4-hydroxylase is an attractive strategy to reduce the invasive properties of melanoma cells.
Subject(s)
Gene Expression Regulation, Neoplastic , Melanoma/genetics , Procollagen-Proline Dioxygenase/genetics , Prolyl Hydroxylases/genetics , Skin Neoplasms/genetics , Cell Line, Tumor , Cell Proliferation/genetics , Collagen/metabolism , DNA Methylation/genetics , Humans , Melanoma/pathology , Protein Processing, Post-Translational/genetics , Reference Values , Skin Neoplasms/pathologyABSTRACT
BACKGROUND: Isothiocyanates are constituents of cruciferous vegetables which have been associated with reduced cancer risk partially through their ability to induce apoptosis in malignant cells including melanoma. MATERIALS AND METHODS: We have utilized human malignant melanoma (A375), epidermoid carcinoma (A431) and immortalized keratinocyte (HaCaT) cells exposed to various isothiocyanates, under different experimental conditions. RESULTS: An experimental in vitro model utilizing low isothiocyanate concentrations (0.1-5 µM for 48 h with all treatments being refreshed after 24h) was shown to be (i) most efficient in exerting an anti-cancer effect when compared to higher concentrations (5-100 µM for 24 or 48 h added as a single bolus) and (ii) specific to A375 cells while A431 and HaCaT cells remained unaffected. Such effect involved the activation of several caspases including (iii) initiator caspases 8, 9, 4 (indicating the involvement of intrinsic, extrinsic and endoplasmic reticulum-based pathways) and (iv) effector caspases 3, 7 and 6. CONCLUSION: Utilization of low isothiocyanate concentrations (under the conditions described herein) exerts an anti-cancer effect specific to human malignant melanoma cells thus providing a therapeutic basis for their utilization in management of the disease.
