Long non-coding RNAs (lncRNAs), a group of non-protein-coding RNAs longer than 200 nucleotides, are involved in multiple biological and pathological processes, such as proliferation, apoptosis, migration, invasion, angiogenesis, and immune escape. Many studies have shown that lncRNAs participate in the complex network of cancer and play vital roles as oncogenes or tumor-suppressor genes in a variety of cancers. Moreover, recent research has shown that abnormal expression of lncRNAs in malignant tumor cells before and after radiotherapy may participate in the progression of cancers and affect the radiation sensitivity of malignant tumor cells mediated by specific signaling pathways or cell cycle regulation. In this review, we summarize the published studies on lncRNAs in radiotherapy regarding the biological function and mechanism of human cancers, including esophageal cancer, pancreatic cancers, nasopharyngeal carcinoma, hepatocellular carcinoma, cervical cancer, colorectal cancer, and gastric cancer.

Long non-coding RNAs (lncRNAs) have appeared as vital regulatory factors in different pathological processes, particularly in tumorigenesis. Increasing number of evidence has demonstrated that long intergenic non-coding RNA 00662 (LINC00662) is overexpressed in several types of cancers and promotes cancer initiation and development. However, whether LINC00662 participates in colorectal cancer (CRC) remains unclear. This study was aimed to explore the expression, biological function and regulatory mechanism of LINC00662 in CRC. Here, we found that LINC00662 expression was obviously upregulated in CRC tissues and cell lines. Down-regulation of LINC00662 dramatically inhibited the growth of CRC cells and increased CRC cell apoptosis.MicroRNA-145 (miR-145) was speculated as a target miRNA of LINC00662 by bioinformatics analysis. Luciferase reporter assays and RNA pull-down assays verified that LINC00662 directly interacted with miR-145. Expression of miR-145 was downregulated in CRC tissues and cell lines. Up-regulation of miR-145suppressed cell growth and promoted apoptosis in CRC cells. Suppression of miR-145markedly reversed the suppressive function of LINC00662 knockdown on CRC cell growth. In addition, c-myc was confirmed as a target gene of miR-145 in CRC cells.  Recover of c-myc expression partially reversed suppression effect mediated by LINC00662 downexpression or miR-145overexpressionon CRC cell growth. Taken together, our results indicate that LINC00662lead to the malignant behavior of CRC cells by upregulating c-myc via sponging miR-145, underlining the essential role of the LINC00662/miR-145/c-myc axis in regulating the growth of CRC cells.

Objective: This study was undertaken to investigate the effect of C225 on the radio-sensitivity of MDA-MB-231 cells line and to disclosure underlying mechanism. Methods: CCK8 assay was used to measure the proliferation inhibition of C225 on MDA-MB-231 cells. The combined effects of C225 plus radiation on the proliferation of MDA-MB-231 cells were also evaluated by CCK-8 assay. The clonogenic assay was performed to evaluate the cell surviving fractions and to determine the radio-sensitizing effect of C225 on MDA-MB-231 cells. The apoptosis and cell cycle distribution were analyzed by flow cytometry. Western blot analysis was used to detect the expression of p-EGFR, p-Akt, p-P38, and caspase-3. Results: C225 had an inhibiting effect on the proliferation of cells in a concentration-dependent manner. The cloning formation capacity was decreased in C225 plus radiation group. C225 increased radio-sensitivity of cells and led to cell cycle arrest in G0/G1 phase markedly. Cells treated with C225 and radiation predominantly exhibited G0/G1 phase arrest and significant decreased in the fraction of cells in the S phase. Moreover, C225 and radiation significantly increased the apoptosis rate of cells. Decreased cell proliferation was further supported by the down-regulation of p-EGFR and its downstream singling pathway proteins such as p-Akt and p-P38. The up-regulation of the Caspase-3 expression in C225 plus radiation group revealed that C225 could increase radiation-inducing cell apoptosis. Conclusion: C225 could increase the radio-sensitivity of cells, which may be due to the anti-proliferative synergistic effect between C225 and radiation as well as the down-regulation of the PI3K/Akt signaling pathway.

Objective: The study was undertaken to investigate the effects of polyethyleneimine (PEI)-mediated adenovirus 5 early region 1A (E1A) on radiosensitivity of human hepatic carcinoma cell in vitro and to disclosure the underlying mechanism. Materials and Methods: Human hepatic carcinoma SMMC-7721 cell line was transfected with E1A gene using PEI vector. Untransfected cells (SMMC-7721 group), cells transfected with blank-vector (SMMC-7721-vect group), and cells transfected with E1A gene (SMMC-7721-E1A group) were treated with 6 MV X-ray irradiation at doses of 0, 1, 2, 4, 8 and Gy, respectively. Radiosensitivity was determined by MTT assay and quantified by calculating the cell survival rate. Cell-cycle distribution and apotosis rate were monitored by flow cytometry. Results: The survival rate of SMMC-7721-E1A was significantly lower than that of SMMC-7721 cell. Apoptosis rate of SMMC-7721-E1A group was significantly higher than that of SMMC-7721group (P<0.01).The ratio of S stage in cell cycle of SMMC-7721-E1A was significantly lower than that in SMMC-7721 cell. The ratio of G2/M stage in cell cycle of SMMC-7721-E1A was significantly higher than that in SMMC-7721 cell (P<0.01). Conclusion: PEI could transfect E1A gene into hepatic carcinoma cells PEI-mediated E1A could effectively enhance radiosensitivity of hepatic carcinoma cells which may be related to its effects on apoptosis promoting leading to S phase suppression and G2/M phase arrest.