Adipocytes in the breast cancer microenvironment: different tumor cells, different ways to respond

Abstract

Adipocytes are considered to be critical in the tumoral microenvironment of breast cancer. However, most studies have focused on linking obesity and cancer, ignoring changes on normal adipocytes. Therefore, we retrieved microarray data from a GEO dataset (GSE95827) to analyse transcriptional changes in 3T3-L1 adipocytes after 3 days of co-culture with MCF7 (Ad+MCF) or MDAMB-231 breast cancer cell (Ad+MDA).By GEO2R tool, we determined 245 up-regulated genes in Ad+MCF7 and 215 in Ad+MDA compared to adipocytes alone (p<0.01), but only 68 of them overlapped between conditions. Gene OntologyAnalysis was performed and showed that the biological process enrichment is completely different between MDA-MB-231 and MCF7-co-cultured adipocytes. Even more, co-culture with MDA-MB-231cells enriched adipocytes with genes involved in Cellular response to interleukin-6 (GO:0071354) and Positive regulation of NIK/NF-kB signaling (GO:1901224), both related to inflammation. Transcription factors (TF) analysis by ISMARA platform predicted that NF-kB family members had the highest activity in Ad+MDA. To verify this result, we performed immunofluorescence assays detecting the presence of phosphorylated NF-kB subunit p65. MDA-MB-231 cells significantly led to a higher fluorescence intensity in adipocyte nuclei than MCF7 did when compared to basal condition. Moreover, mRNA levels of NF-kB targets as cxcl1, cxcl5, il6 obtained from the analyseddataset were found up-regulated in Ad+MDA respect to adipocytes alone (p<0.05). Interestingly, expression levels of Il6 family members (Il6 and Il11) were up-regulated in MDA-MB-231 cell line compared to MCF7 cells in three different public datasets, which could explain NF-kB activation only in Ad+MDA.These results suggest that breast cancer cells stimulate adjacent adipocytes in different ways leading or not to inflammation in adipocytes.