Loss of Both CDKN2A and CDKN2B Allows for Centrosome Overduplication in Melanoma

Shyamal Patel,Christopher J Wilkinson,Elena V Sviderskaya

doi:10.1016/j.jid.2020.01.024

Abstract

Centrosomes duplicate only once in coordination with the DNA replication cycle and have an important role in segregating genetic material. In contrast, most cancer cells have centrosome aberrations, including supernumerary centrosomes, and this correlates with aneuploidy and genetic instability. The tumor suppressors p16 (CDKN2A) and p15 (CDKN2B) (encoded by the familial melanoma CDKN2 locus) inhibit CDK4/6 activity and have important roles in cellular senescence. p16 is also associated with suppressing centrosomal aberrations in breast cancer; however, the role of p15 in centrosome amplification is unknown. Here, we investigated the relationship between p15 and p16 expression, centrosome number abnormalities, and melanoma progression in cell lines derived from various stages of melanoma progression. We found that normal human melanocyte lines did not exhibit centrosome number abnormalities, whereas those from later stages of melanoma did. Additionally, under conditions of S-phase block, p15 and p16 status determined whether centrosome overduplication would occur. Indeed, removal of p15 from p16-negative cell lines derived from various stages of melanoma progression changed cells that previously would not overduplicate their centrosomes into cells that did. Although this study used cell lines in vitro, it suggests that, during clinical melanoma progression, sequential loss of p15 and p16 provides conditions for centrosome duplication to become deregulated with consequences for genome instability.

Highlights

Extra centrosomes are frequently observed in solid tumors including melanomas, and this centrosome amplification correlates with aneuploidy and genetic instability (Brinkley, 2001; Charters et al, 2011; Lingle et al, 2002; Pihan et al, 1998)
Centrosome numbers at different stages of tumorigenesis To find out if cells from later stages of melanoma would display increased centrosome numbers, cells were stained with an antieg-tubulin antibody that binds to the material around each centriole, each centrosome showing as two punctae of staining
Centrosome amplification was observed in several cell lines, notably radial growth phase (RGP) lines SGM2 and SGM4 (Figure 1b), nearly a quarter of whose cells had three or more centrosomes

Summary

Introduction

Extra centrosomes are frequently observed in solid tumors including melanomas, and this centrosome amplification correlates with aneuploidy and genetic instability (Brinkley, 2001; Charters et al, 2011; Lingle et al, 2002; Pihan et al, 1998). The abnormal spindle structures he predicted have been observed in clinical samples. They are eventually resolved into bipolar spindles, but the delay leads to lagging chromosomes that are damaged (Ganem et al, 2009). The centrosome is normally duplicated in Sphase and separated into two centrosomes in G2, with each centrosome contributing to one of the two spindle poles in M phase. A normal cell contains a maximum of two centrosomes; any more are supernumerary

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