Increased co-expression of PSMA2 and GLP-1 receptor in cervical cancer models in type 2 diabetes attenuated by Exendin-4: A translational case-control study.

BACKGROUND Type 2 diabetes (T2D) increases the risk of many types of cancer. Dysregulation of proteasome-related protein degradation leads to tumorigenesis, while Exendin-4, a glucagon-like peptide 1 receptor (GLP-1R) agonist, possesses anti-cancer effects. METHODS We explored the co-expression of proteasome alpha 2 subunit (PSMA2) and GLP-1R in the Cancer Genome Atlas (TCGA) database and human cervical cancer specimens, supplemented by in vivo and in vitro studies using multiple cervical cancer cell lines. FINDINGS PSMA2 expression was increased in 12 cancer types in TCGA database and cervical cancer specimens from patients with T2D (T2D vs non-T2D: 3.22 (95% confidence interval CI: 1.38, 5.05) vs 1.00 (0.66, 1.34) fold change, P = 0.01). psma2-shRNA decreased cell proliferation in vitro, and tumour volume and Ki67 expression in vivo. Exendin-4 decreased psma2 expression, tumour volume and Ki67 expression in vivo. There was no change in GLP-1R expression in 12 cancer types in TCGA database. However, GLP-1R expression (T2D vs non-T2D: 5.49 (3.0, 8.1) vs 1.00 (0.5, 1.5) fold change, P < 0.001) was increased and positively correlated with PSMA2 expression in T2D-related (r = 0.68)  but not in non-T2D-related cervical cancer specimens. This correlation was corroborated by in vitro experiments where silencing glp-1r decreased psma2 expression. Exendin-4 attenuated phospho-p65 and -IκB expression in the NF-κB pathway. INTERPRETATION PSMA2 and GLP-1R expression in T2D-related cervical cancer specimens was increased and positively correlated, suggesting hyperglycaemia might promote cancer growth by increasing PSMA2 expression which could be attenuated by Exendin-4. FUNDING This project was supported by Postdoctoral Fellowship Scheme, Direct Grant, Diabetes Research and Education Fund from the Chinese University of Hong Kong (CUHK).