Large scale in vivo micro‐RNA loss of function screen identified miR‐29a, miR‐100 and miR‐155 as modulators of radioresistance and tumor‐stroma communication

Abstract

Micro RNAs (miR) are master regulators of cellular transcriptome. We aimed to investigate the role of miR regulation on tumor radiosensitivity and development of local tumor recurrence by a novel large‐scale in vivo loss of function screen. For stable miR silencing, human A431 tumor cells were transduced with lentiviral constructs against 170 validated human miR (miRzip library). Fractionated radiotherapy (5x6Gy) was applied to A431 miRzip library growing s.c. in NCr nude mice. Enrichment of miRZip and miR expression was assessed using multiplexed qRT‐PCR. The modulatory effect of miR on tumor and tumor microenvironment response to ionizing radiation was further evaluated by clonogenic survival, apoptosis (Caspase 3/7), DNA double‐strand breaks (DSB, nuclear γH2AX foci), tumor microvessel density (MVD), transcriptome and protein analysis. Fractionated irradiation of the A431 miRzip library led to regression of tumors. However, after a latency period, tumors ultimately progressed and formed local recurrences indicating the survival of a subpopulation of miRzip expressing tumor clones. Among the selected miR for subsequent validation studies, loss of miR‐29a, miR‐100 and miR‐155 was found to enhance clonogenic survival, reduce apoptosis and residual γH2AX foci of irradiated tumor cells. Moreover, knockdown of miR increased tumor angiogenesis correlating with elevated VEGF and TGFα expression levels. This phenomenon was most evident after tumor irradiation in vivo suggesting a critical role for tumor‐stroma communication in development of the radioresistant phenotype. Engineering radioresistant tumors in vivo by modulating miR expression may lead to identification of critical targets for conquering local therapy failure.

Targeting hydrogen sulphide signaling in breast cancer

“…Targeting NKG2D ligands and/or blocking PD-1/PD-L1 interactions (checkpoint inhibitors) have been the subject of clinical research and application [55] , [56] . Since alterations in the miR-155/NOS2/NO signaling pathway have been reported to attenuate the immune suppressive tumor microenvironment [31] , [57] , [58] , [59] , we hypothesized that endogenous H 2 S may modulate the immunogenic profile of BC cells. Tumor cells tend to down-regulate NKG2D ligands through intracellular retention and/or extracellular shedding to evade NKG2D receptor-mediated NK cell killing.…”

Improved Radiotherapy Sensitivity of Nasopharyngeal Carcinoma Cells by miR-29-3p Targeting COL1A1 3’-UTR

“…In colorectal cancer, miR-29a was verified to enhance radioresistance via activating the PI3K/Akt pathway [24]. However, another large-scale in vivo loss of function screen identified miR-29a as a modulator of radiosensitivity, since loss of miR-29a led to enhanced clonogenic survival and reduced apoptosis in irradiated tumor cells [25]. In the present study we established a radioresistant CNE-2R sub-cell line following standard procedures.…”

lncRNA CASC2 Enhances 131I Sensitivity in Papillary Thyroid Cancer by Sponging miR-155

“…Previous studies indicated that CASC2 could serve as a competing endogenous RNA (ceRNA) or miRNA sponge in the development of cancers [ 12 , 19 ]. Accruing reports demonstrated that miR-155 is an oncogenic miRNA involved in drug resistance and radioresistance in human cancers [ 20 – 22 ]. Furthermore, it is suggested that miR-155 expression was increased in papillary thyroid carcinoma and its overexpression promoted cell proliferation by regulating adenomatous polyposis coli and Wnt/ β -catenin signaling [ 23 – 25 ].…”