GSE97647
Glucose impairs tamoxifen sensitivity modulating CTGF in breast cancer cells
Metabolic diseases, including type 2 diabetes and obesity are relevant negative prognostic factor in patients with breast cancer (BC). We have investigated the mechanisms through which elevated glucose levels affect tamoxifen sensitivity of estrogen receptor positive (ER+) BC cells. We found that MCF7 BC cell sensitivity to tamoxifen was 2-fold reduced in 25mM glucose (HG), a concentration mimicking hyperglycaemia, compared to 5.5 mM glucose (LG), resembling normal fasting glucose levels in humans. Shifting MCF7 cells from HG to LG ameliorated their responsiveness to tamoxifen. RNA-Sequencing revealed that glucose modified the transcriptome of MCF7 cells. In particular, cell cycle-related genes were affected by glucose. Combining gene specific knockdown and treatment with human recombinant proteins, we identified the Connective Tissue Growth Factor (CTGF) as glucose-induced factor able to reduce MCF7 cell sensitivity to tamoxifen. Moreover, we found that both CTGF expression levels and tamoxifen responsiveness were enhanced co-culturing MCF7 cells with human adipocytes through an Interleukin-8 (IL8)-mediated mechanism. Indeed, IL8 inhibition reduced CTGF levels and rescued tamoxifen sensitivity in MCF7 cells. Interestingly, CTGF immuno-detection in bioptic specimens obtained from women with ER+ BC correlated with distant metastases (P-value = 0.000), hormone therapy resistance (P-value = 0.000), reduced overall (P-value = 0.051) and disease free survival (P-value = 0.000). Thus, glucose affects tamoxifen responsiveness directly modulating CTGF in BC cells, and indirectly promoting the adipocytes’ release of IL8. Both CTGF and IL8 may represent potential targets in novel therapeutic strategies to increase tamoxifen sensitivity. Overall design: The gene expression profile of MCF7 cells grown in high glucose and then shifted in low glucose (HG?LG; n=1) were compared to MCF7 cells grown in high glucose (HG; n=1).