Long noncoding RNA lnc-RI regulates DNA damage repair and radiation sensitivity of CRC cells through NHEJ pathway.

A percentage of colorectal cancer (CRC) patients display low sensitivity to radiotherapy, which affects its therapeutic effect. Cancer cells DNA double-strand breaks (DSBs) repair capacity is crucial for radiosensitivity, but the roles of long noncoding RNAs (lncRNAs) in this process are largely uncharacterized. This study aims to explore whether lnc-RI regulates CRC cell growth and radiosensitivity by regulating the nonhomologous end-joining (NHEJ) repair pathway. CRC cells in which lnc-RI has been silenced showed lower cell growth and higher apoptosis rates due to increased DSBs and cell cycle arrest. We found that miR-4727-5p targets both lnc-RI and LIG4 mRNA and inhibit their expression. CRC cells showed increased radiosensitivity when lnc-RI was silenced. These results reveal novel roles for lnc-RI in both DNA damage repair and radiosensitivity regulation in CRC cells. Our study revealed that lnc-RI regulates LIG4 expression through lnc-RI/miR-4727-5p/LIG4 axis and regulates NHEJ repair efficiency to participate in DNA damage repair. The level of lnc-RI was negatively correlated with the radiosensitivity of CRC cells, indicates that lnc-RI may be a potential target for CRC therapy. We also present the first report of the function of miR-4727-5p.

MiR-34s negatively regulate homologous recombination through targeting RAD51.

Double-strand breaks (DSBs), the most serious lesions of DNA, often induce chromosomal aberrations and are intimately associated with oncogenesis. A normal DNA damage response (DDR) network contains two major repair pathways: homologous recombination (HR) and non-homologous end-joining (NHEJ). Studies of DSB repair-associated molecules have focused mainly on DNA repair proteins. However, non-coding RNAs also play important roles in the process of DSB repair. Over the past two decades, microRNAs (miRNAs) have been extensively investigated. Our previous work showed that miR-34c-5p overexpression results in suppression of RAD51 and upregulation of γH2AX. In accordance with this, we confirmed that miR-34s family overexpression increased endogenous DSB levels to different extents, an effect that was further confirmed to be associated with the decreased efficiency of HR repair. In addition, miR-34s overexpression also induced G1 arrest, inhibited proliferation and promoted apoptosis. As a central molecule in the process of HR pathway, RAD51 expression was strongly repressed in cells transfected with the miR-34a/b/c-5p mimic. Finally, we demonstrated that miR-34a/b/c-5p directly targets the RAD51 mRNA 3'-UTR or indirectly inhibits RAD51 expression via the p53 signaling pathway. Taken together, our results indicate that miR-34s overexpression depresses the efficiency of HR repair and induces DSBs by downregulating RAD51 expression. Our findings highlight a novel mechanism of HR pathway regulation via the miR-34s/p53/RAD51 axis.

Checkpoint inhibitor pneumonitis in Chinese lung cancer patients: clinical characteristics and risk factors.

BACKGROUND: Checkpoint inhibitor pneumonitis (CIP) may be accompanied by lung cancer in patients treated with immune checkpoint inhibitors (ICI). This study aimed to test the risk factors, genetic and clinical characteristics of CIP in a cohort of Chinese patients with lung cancer. METHODS: We retrospectively reviewed the medical records of eligible patients who received ICI treatment from December 2017 to September 2020 in our hospital. Patient characteristics, ICI protocols, and mutation frequencies of related genes are compared between the CIP group and the non-CIP group. RESULTS: A total of 94 patients were recruited. Of them, 16 (17.0%) patients developed CIP. Multivariate logistic regression analysis suggested Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≥2 [odds ratio (OR) =6.53; 95% confidence interval (CI), 1.74-24.46; P=0.005] and previous pulmonary fibrosis (OR =20.13; 95% CI, 3.64-111.44; P=0.001) were independently associated with a higher incidence of CIP. There was an increasing trend, although not statistically significant, in the risk of CIP in patients with TP53 mutation (P=0.280). Most CIP patients were managed successfully following the current guideline. However, serious events (including one death) were still observed. CONCLUSIONS: ECOG PS ≥2 and earlier pulmonary fibrosis were closely correlated to the occurrence of CIP in Chinese lung cancer patients after ICI treatment. Early screening and prompt intervention are necessary for the management of CIP.

Screening of Long Noncoding RNAs Induced by Radiation Using Microarray.

DNA damage repair and G2/M arrest are the key factors regulating the survival of cancer cells exposed to radiation. Recent studies have shown that long noncoding RNAs (lncRNAs) play important roles in a variety of biological processes, including DNA repair, cell cycle regulation, differentiation, and epigenetic regulation. However, the knowledge about the genome scale of lncRNAs and their potential biological functions in tumor cells exposed to radiation are still unclear. In this study, we used LncRNA + mRNA Human Gene Expression Microarray V4.0 to profile lncRNA and messenger RNA (mRNA) from HeLa, MCF-7, and A549 cells after irradiation with 4 Gy of γ-radiation. We identified 230, 227, and 274 differentially expressed lncRNAs and 150, 214, and 274 differentially expressed mRNAs in HeLa, MCF-7, and A549 cells, respectively, among which there are 14 common differentially expressed lncRNAs and 22 common differentially expressed mRNAs in all of the 3 cell lines. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that these differentially expressed mRNAs were mainly associated with cell cycle. Further, we also predicted the target genes and functions of these differentially expressed lncRNAs. Our study on lncRNAs has greatly expanded the field of gene research in the relationship of radiation, cell cycle, and DNA damage.