Immunotherapy is revolutionizing the field of oncology and specifically Breast Cancer (BC). Immune exclusion phenomenon that is orchestrated by immune-suppressive cytokines acts as a formidable barrier towards efficient harnessing of tumor cells. Interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) play a pivotal role in shaping the tumor microenvironment and the magnitude of immune resistance. Finding molecular weapons to efficiently harness BC progression, enhance immune cells cytotoxicity and most importantly alleviates the tumor-induced immune suppressive microenvironment was our main goal. microRNA-4317 is a novel miRNA that was reported to have an alerted expression pattern in several malignancies. Thus our aim was to unravel the mechanistic role of miR-4317 in BC patients and to investigate its impact on the tumor microenvironment.
Breast tissues were collected from 40 BC patients. MDA-MB-231 and MCF7 cells were cultured and transfected with miR-4317 oligonucleotides. Total RNA was extracted and quantified by qRT-PCR. Cellular proliferation and anchorage independent growth were measured using BrdU and colony forming assays respectively. Cell culture supernatants were screened for IFN-γ and TNF-α using Human IFN-γ and TNF-α Elisa kits, respectively.
miR-4317 was found to be specifically down-regulated in BC tissues compared to its normal counterparts. TNBC patients showed the lowest levels of miR-4317. In parallel, the aggressive TNBC cells, MDA-MB-231 showed more reduced expression levels of miR-4317 compared to hormone receptor positive BC cells, MCF7. Mechanistically, ectopic expression of miR-4317 resulted in a significant decrease in cellular proliferation rate and anchorage independent ability of BC cell lines. Additionally, a potent repression of TNF-α release in cellular supernatant was observed together with an increase in IFN-γ levels thus restoring the immune-stimulating conditions at the tumor microenvironment.
miR-4317 acts as a novel tumor suppressor miRNA. Moreover, it has a potent impact in alleviating the tumor induced immune-suppressive microenviroment. Thus suggesting miR-4317 as a novel therapeutic agent in BC.
German University in Cairo
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All authors have declared no conflicts of interest.