MiR-99a Enhances the Radiation Sensitivity of Non-Small Cell Lung Cancer by Targeting mTOR

Abstract

Background/Aims: Radiation therapy is an important and effective modality for the treatment of non-small cell lung cancer (NSCLC). MicroRNAs (miRNAs) are crucial post-transcriptional regulators that are involved in numerous important biologic processes. However, their potential involvement in radiation sensitivity remains unknown. Materials: We performed integrated analysis of miRNA expression in NSCLC using The Cancer Genome Atlas datasets. miR-99a was found to be significantly upregulated in cancer tissue and regulated cell survival. Cell culture was used to assess the role of miR-99a in radiation sensitivity. We then used flow cytometry to examine the effects of miR-99a on the cell cycle and apoptosis in cells exposed to radiation. To identify gene targets of miR-99a, a bioinformatics approach was adopted, and the findings of this analysis were verified using luciferase reporter assays. Finally, an in vivo study was conducted to examine the effect of miR-99a on tumor volume in an NSCLC mouse model undergoing radiation therapy. Results: miR-99a was significantly upregulated in radiation-sensitive A549 cells compared with radiation-resistant A549 cells. miR-99a overexpression was shown to enhance radiosensitivity, while inhibition of miR-99a resulted in radioresistance of NSCLC cell lines in vitro and in vivo. In addition, by bioinformatics software analysis and luciferase assays, mammalian target of rapamycin (mTOR) was identified as a direct target of miR-99a. Furthermore, AZD2014, an inhibitor of mTOR, enhanced radiosensitivity and apoptosis in NSCLC cell lines, while mTOR overexpression resulted in radioresistance and cell survival from miR-99a-induced cell apoptosis. Moreover, miR-99a overexpression further increased the efficacy of radiation therapy in an NSCLC xenograft mouse model, and miR-99a and mTOR expression was significantly inversely correlated. Conclusions: Altogether, these data suggested miR-99a functions as a tumor suppressor that has a critical role in regulating radiosensitivity of NSCLC by targeting the mTOR signaling pathway.

miR‑155, miR‑96 and miR‑99a as potential diagnostic and prognostic tools for the clinical management of hepatocellular carcinoma

“…Recent studies demonstrated that the miR-99 family had potential functions as tumor suppressors, which may affect tumor cell growth, invasion and migration (21). Dysregulation of the miR-99 family members has been reported to serve an important role in multiple types of cancer (22)(23)(24)(25). The expression levels of miR-99a, miR-99b and miR-100 were all significantly decreased in glioma tissues compared with non-neoplastic brain tissues.…”

Suppression of cyclooxygenase 2 increases chemosensitivity to sesamin through the Akt‑PI3K signaling pathway in lung cancer cells

“…In brief, treated lung cancer cells were resuspended in 500 µl 1X Binding Buffer and incubated with 10 µl propidium iodide (PI) and 5 µl Annexin V-fluorescein isothiocyanate (FITC). Following 5 min of incubation in the dark, flow cytometric analysis was conducted using a FACScan flow cytometer (BD Biosciences, Franklin Lakes, NJ, USA) and a FlowJo 7.6 software (1997-2008; FlowJo LLC, Ashland, OR, USA) (13).…”

Role of non-coding RNAs and RNA modifiers in cancer therapy resistance

“…Radiotherapy is an essential approach for locally advanced CC. However, around 30% of radiotherapy- Lung cancer miR -198 Inhibiting HGF/c-MET pathway [170] miR-99a Binding to mTOR [171] miR-558 Associating with AATK [172] miR-148b Modulating MutL homologue 1 [173] miR-335 Reducing the expression of PARP-1, downregulating NF-κB [ 174] miR-1246 Inhibiting DR5 [175] miR-21 Upregulating HIF-1α [176] miR-208a Targeting p21 with a corresponding activation of the Akt/mTOR pathway [177] Oral cancer stem cells miR-218 Activating miR-218/Bmi1 axis [178] Hepatocellular carcinoma miR-92b Reducing p57kip2 expression [179] Breast cancer miR-142-3p Attenuating CSCs characteristics and inhibiting β-catenin expression [180] miR-22 Negatively modulating Sirt1 [181] miR-668 Forming miR-668/ IκBα/NF-κB axis [182] Ovarian cancer miR-214 Depressing PETN and consequently activating PI3K/Akt pathway [183] treated patients have been found occurring recurrence or even metastasis, partially resulting from radioresistance. It has been reported that miRNAs participate in either radiation responsiveness or radioresistance.…”

“…Multiple miRNAs have been associated with radiation efficacy in NSCLC, including miR-198, miR-99a, miR-558 and miR-148b [170][171][172][173]. To be specific, overexpression of miR-198 is found to suppress cell proliferation, migration, invasion and promote apoptosis by inhibiting the hepatocyte growth factor (HGF)/c-MET pathway, which overcomes resistance to radiation in NSCLC cells and tissues [170].…”

“…To be specific, overexpression of miR-198 is found to suppress cell proliferation, migration, invasion and promote apoptosis by inhibiting the hepatocyte growth factor (HGF)/c-MET pathway, which overcomes resistance to radiation in NSCLC cells and tissues [170]. MiR-99a is identified to directly bind to mTOR and functions as a tumor suppressor, modulating radiosensitivity [171]. Similarly, it has been discovered that miR-558 is associated with apoptosis-associated tyrosine kinase (AATK), a radiosensitization-associated gene, and regulates the development of resistance to radiotherapy [172].…”