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.