PO-292 Breast cancer stem cell reprogramming: deciphering the impact of glucose and the contribute of tumour microenvironment

Introduction Diabetes-associated hyperglycemia is linked to poorer prognosis and survival in breast cancer (BC). Indeed, glucose can affect both tumour and tumour-surrounding cells. BC cells are embedded in an adipocyte-rich microenvironment, which, beside adipocytes, contains Stromal-Vascular Fraction Cells (SVFCs). In this scenario , epithelial and stromal compartments communicate through the release of soluble factors and establish an intricate crosstalk. Here, we analysed whether glucose could directly affect the phenotype of ER + MCF7 BC cells and interfere with their interaction with adipose-derived SVFCs, thereby promoting tumour progression. Material and methods MCF7 cell stemness markers were measured by qReal-Time PCR. Adipose-derived (Ad-)SVFCs were obtained by mammary adipose tissue specimens of women undergoing plastic surgery. The trascriptome of MCF7 exposed to either low (LG-5.5 mM) or high glucose concentration (HG-25 mM) was obtained by RNA-Sequencing (Illumina HiSeq3000). Results and discussions HG exposure of MCF7 determined a significant increase of SOX2 mRNA levels as compared to LG, suggesting the induction of stemness programming. Co-culture with Ad-SVFCs in HG increased SOX2, NANOG and OCT4 mRNA levels in MCF7, as compared to isolated culture, indicating the involvement of SVF-produced soluble factors in BC stem cell reprogramming. Moreover, in presence of Ad-SVFCs and HG, MCF7 produced a higher number of mammospheres, which also displayed larger size. However, both in LG and in HG, conditioned media (CM) obtained from Ad-SVFCs produced no relevant effect on MCF7 stemness. Nevertheless, when Ad-SVFCs were pre-incubated with CM obtained from HG-treated MCF7, their CM very effectively increased OCT4, NANOG and SOX2 mRNA levels in MCF7. Thus, HG likely perturbs MCF7, which produce soluble factors leading Ad-SVFCs to release, in turn, reprogramming factors for BC cell stemness. In this regard, we have observed that HG modification of MCF7 transcriptome includes deregulation of 17 genes (pval=0.05) encoding for secreted proteins involved in cancer progression-related pathways, which may potentially play a role in tumour-stroma interactions. Conclusion Glucose affects BC stem cell reprogramming both directly and through Ad-SVFCs. Deciphering the mechanisms that govern this intricate crosstalk will pave the way to new targeted strategies to improve BC control in conditions of metabolic derangement.