PO-285 Role of tumour associated macrophages (TAMs) in regulation of cancer stem cell (CSCs) enrichment in breast cancer

Abstract

IntroductionStromal cells present in the tumour microenvironment play an important role in tumour growth and progression. Studies have shown increased infiltration of tumour associated macrophages (TAMs) correlated with increased malignancy of cancer. In our study, we have explored the macrophage and cancer cell interaction, in polarisation of macrophages and their effect on cancer stem cell (CSC) enrichment in breast cancer.Material and methodsWe treated macrophages (Raw 264.7) with conditioned medium (CM) of mice breast cancer cells (4 T1) and observed for the polarisation by analysing M2 macrophage marker CD206 through flow cytometry and immunofluorescence. Further, we studied the enrichment of breast CSCs in response to activated/polarised macrophage CM by analysing CSC specific markers ALDH1 activity and Sca-1 expression by flow cytometry and expression of CSC specific transcription factors sox-2, oct-3/4 and nanog using immunoblotting as well as immunofluorescence. Moreover, breast tumour growth in response to activated macrophage CM was assessed by developing orthotopic breast cancer models in Balb/c mice.Results and discussionsWe have shown that treatment with CM of breast cancer cells polarises macrophages into M2 type which is a prevalent phenotype in TAM population. Interestingly, treatment with CM of tumour cell activated macrophages in breast cancer cells has shown increased ALDH1 activity and Sca-1 expression along with CSC associated transcription factors Sox-2, Oct3/4 and Nanog, indicating the role of TAMs in CSC enrichment. Jak-Stat pathway has also been upregulated in TAM CM treated breast cancer cells and inhibition of Stat-3 by its specific inhibitor resulted in abrogation of CSC enrichment. Further, intra-tumoral injection of activated macrophage CM enhanced the breast tumour growth in Balb/c mice depicting the role of tumour activated macrophage in breast tumour promotion.ConclusionWe observed that breast cancer cells polarise macrophages towards TAM phenotype that further promotes breast tumour progression by enhancing CSC phenotype.