Abstract 3559: The rare BCL-2 isoform BCL-2β is associated with melanoma survival and the apoptotic response to UV and cisplatin

• Published in: Cancer research (Chicago, Ill.) Ill.), 2016-07, Vol.76 (14_Supplement), p.3559-3559
• Main Authors: Warren, Chloe, Vilain, Ricardo E., Ashton, Katie A., Almazi, Juhura G., Braye, Stephen, Moscato, Pablo, Bowden, Nikola A.
• Format: Article
• Language: English
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/1538-7445.AM2016-3559

There are two isoforms of the anti-apoptotic protein BCL-2. BCL-2α (wild-type) is well characterised and is known predominantly for its role in apoptosis, BCL-2β lacks the C-terminal transmembrane (TM) domain and its function has not yet been characterised. The aim of this study was to quantify and determine the biological role of the BCL-2β isoform in melanoma. BCL-2α and BCL-2β isoforms were quantified at the mRNA and protein level in a cohort of 141 FFPE melanoma tumours using qPCR and multiple reaction monitoring (MRM) tandem mass spectrometry and compared to clinical parameters including age at diagnosis, gender, solar elastosis, BRAF/NRAS mutation, Breslow thickness, disease free survival and overall survival. The role of the BCL-2α and BCL-2β isoforms in apoptosis were investigated by quantifying transcript expression and apoptosis before and up to 72 hours after UVB irradiation (650J/m2) and cisplatin treatment (10ug/mL). siRNA knockdown targeted to each individual isoform transcript was used to verify the apoptotic response. Expression of the BCL-2β isoform in tumours was significantly associated with increased overall survival (686.4 weeks, 95% CI 462.5-910.3). BCL-2α response to UVB and cisplatin (i.e. downregulation prior to apoptosis) was the same in melanocyte and melanoma cell lines. However, BCL-2β response was varied across the melanoma cell lines, but was similar to that of BCL-2α in melanocytes. siRNA knock-down of BCL-2α resulted in increased apoptosis and cell death in melanoma cell lines, but knock-down of BCL-2β delayed onset of apoptosis, suggesting the BCL-2β is pro-apoptotic. Our current understanding of the role of BCL-2β is based on the concept that it lack the C-terminal transmembrane domain, and is incapable of localising to target organelles. It is currently thought that the isoform is of null function. However, these observations are based on studies of non-representative synthetic versions of BCL-2β. This is the first time the naturally transcribed version of the rare isoform has been studied. We have demonstrated herein that BCL-2β performs an apoptotic role, and that its regulation in melanoma may be a biomarker of better overall survival. Citation Format: Chloe Warren, Ricardo E. Vilain, Katie A. Ashton, Juhura G. Almazi, Stephen Braye, Pablo Moscato, Nikola A. Bowden. The rare BCL-2 isoform BCL-2β is associated with melanoma survival and the apoptotic response to UV and cisplatin. [abstract]. In: Proceedings of the 107t