40P MALAT-1/miR-30a-5p competing endogenous (ceRNA) network releases the brakes of immune surveillance in breast cancer through its quadruple targets: PD-L1, MIF, IL-10 and TNF-α

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The tumor immune escape phenomenon is a vicious cycle of smart tactics orchestrated by cancer cells to evade immune recognition. Induction of co-inhibitor molecules such as macrophage migration inhibitory factor (MIF), immune checkpoints such as PD-L1and immunoinhibitory cytokines such as IL-10 and TNF-α in the tumor microenvironment are the most effective strategies cancer cells follow to holds the brakes of the immune surveillance phenomena. Immune evasion tactics in breast cancer (BC) patients are still poorly understood. Yet, strong evidence supports the involvement of immune inhibitory cytokines and upregulation of PD-L1 and MIF in BC patients. Non-coding RNAs (ncRNAs) are endogenous molecules that have the ability to form a signaling network modulating multiple targets simultaneously. Our group has recently reported the involvement of MALAT-1 in tuning the immuno-oncogenic profile of BC. Yet, microRNA-30a-5p is a novel miRNA in terms of immunoncology and its involvement in MALAT-1 modulatory network is yet to be explored. The aim of this study was to investigate the involvement of miR-30a-5p in MALAT-1circuit and its impact of PD-L1, MIF, IL-10 and TNF-α in BC. BC patients (n=24) were recruited. Bioinformatics analysis was performed. MDA-MB-231 cells were cultured transfected by miR-30a-5p oligonucleotides and MALAT-1 siRNAs using Hiperfect Transfection protocol. RNA was extracted using biazol, reverse transcribed and quantified using q-RTPCR. MALAT-1 and miR-30a-5p are paradoxically acting ncRNAs in BC patients. MALAT-1 is an upregulated oncogenic lncRNA while miR-30a-5p is a downregulated tumor suppressor miRNA in BC patients. In-silico analysis showed a strong binding of miR-30a-5p to MALAT-1. Experimentally, ectopic expression of miR-30a-5p represses MALAT-1 levels while MALAT-1 siRNAs induced miR-30a-5p levels in MDA-MB-231 cells. miR-30a-5p mimics and/or MALAT-1 siRNAs resulted in a marked repression of PD-L1, MIF, IL-10 and TNF-α. MALAT-1/miR-30a-5p are vital players releasing the immune surveillance brakes supported by BC cells. Dual targeting of MALAT-1 and miR-30a-5p is novel immune-oncological therapeutic approach in BC.