BRAFV600E induces reversible mitotic arrest in human melanocytes via microrna-mediated suppression of AURKB.

Andrew S Mcneal,Timothy H Mccalmont,Hanlin Zeng,David H Lum,Kendra Barker,Douglas Grossman,A Hunter Shain,Ursula E Lang,Matt W Vanbrocklin,Robert Hi Andtbacka,Robert L Judson-Torres,Sheri Holmen,Maria L Wei,Meghan Curtin,Rachel L Belote,Marcus Urquijo,Rodrigo Torres

doi:10.7554/elife.70385

Andrew S Mcneal, Timothy H Mccalmont + Show 15 more

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https://doi.org/10.7554/elife.70385

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Abstract

Benign melanocytic nevi frequently emerge when an acquired BRAFV600E mutation triggers unchecked proliferation and subsequent arrest in melanocytes. Recent observations have challenged the role of oncogene-induced senescence in melanocytic nevus formation, necessitating investigations into alternative mechanisms for the establishment and maintenance of proliferation arrest in nevi. We compared the transcriptomes of melanocytes from healthy human skin, nevi, and melanomas arising from nevi and identified a set of microRNAs as highly expressed nevus-enriched transcripts. Two of these microRNAs-MIR211-5p and MIR328-3p-induced mitotic failure, genome duplication, and proliferation arrest in human melanocytes through convergent targeting of AURKB. We demonstrate that BRAFV600E induces a similar proliferation arrest in primary human melanocytes that is both reversible and conditional. Specifically, BRAFV600E expression stimulates either arrest or proliferation depending on the differentiation state of the melanocyte. We report genome duplication in human melanocytic nevi, reciprocal expression of AURKB and microRNAs in nevi and melanomas, and rescue of arrested human nevus cells with AURKB expression. Taken together, our data describe an alternative molecular mechanism for melanocytic nevus formation that is congruent with both experimental and clinical observations.

Highlights

Cutaneous melanoma is a potentially deadly skin cancer arising from the pigment-producing melanocytes of the human epidermis
Each clinical specimen contained matched RNA samples derived from melanocytic nevi and melanomas that arose from those nevi
The vast majority of melanocytic nevi are stably arrested and harbor BRAFV600E, an oncogenic mutation that induces cellular senescence when expressed in a variety of mammalian cells (Michaloglou et al, 2005; Serrano et al, 1997; Zhu et al, 1998)

Summary

Introduction

Cutaneous melanoma is a potentially deadly skin cancer arising from the pigment-producing melanocytes of the human epidermis. An activating mutation in the BRAF proto-o ncogene (BRAFV600E) drives over half of all cutaneous melanomas (Garnett and Marais, 2004; Davies et al, 2002; Pollock et al, 2003). When a melanocyte acquires a BRAFV600E mutation, the cell does not immediately transform to cancer. Instead, it usually undergoes clonal proliferation followed by stable arrest resulting in a benign skin lesion known as a melanocytic nevus or ‘mole’ (Pollock et al, 2003; Shain et al, 2015; Bastian, 2014; Dankort et al, 2009).

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