Repression of ATR pathway by miR-185 enhances radiation-induced apoptosis and proliferation inhibition

Knockdown of microRNA-1323 restores sensitivity to radiation by suppression of PRKDC activity in radiation-resistant lung cancer cells

Resistance to radiation is a major problem in cancer treatment. The mechanisms of radioresistance remain poorly understood; however, mounting evidence supports a role for microRNAs (miRNAs) in the modulation of key cellular pathways mediating the response to radiation. The present study aimed to identify specific miRNAs and their effect on radioresistant cells. The global miRNA profile of an established radioresistant lung cancer cell line and the corresponding control cells was determined. Differential expression of the miRNAs was confirmed by quantitative real-time PCR (qRT-PCR). The binding effect of identical novel miRNAs and target mRNAs was determined by luciferase assay. Lung cancer cells were transfected with miRNA-specific mimics or inhibitors. The DNA-dependent protein kinase (DNA-PKcs) protein level was tested by western blot analysis. Radiosensitivity of cancer cells was determined using colony formation assay. Among the differentially expressed miRNAs, 25 miRNAs were overexpressed while 18 were suppressed in the radioresistant cells, both basally and in response to radiation compared to their control. An miRNA signature miR-1323 exhibited a >5-fold increase in the radioresistant cells. miR-1323 was demonstrated to bind to PRKDC 3'UTR, which is involved in DNA repair. Ectopic expression of miR-1323 significantly increased the survival fraction of irradiated cancer cells. Inhibition of miR-1323 reversed the radioresistance of cancer cells and subsequently suppressed the expression of miR-1323-regulated DNA-PKcs protein. The present study indicated that miRNAs are involved in the radioresistance of human lung cancer cells. A possible mechanism for resistance to radiation was via enhanced DNA repair. The present study demonstrated a role for miR-1323 in modulating radioresistance and highlights the need for further study investigating the potential role of miR-1323 as both a predictive marker of response and a novel therapeutic agent with which to enhance the efficacy of radiotherapy.

MicroRNA-185 inhibits cell proliferation and induces cell apoptosis by targeting VEGFA directly in von Hippel-Lindau-inactivated clear cell renal cell carcinoma

OBJECTIVES

The von Hippel-Lindau (VHL) gene acts as a tumor suppressor in most clear cell renal cell carcinomas (ccRCCs). Tumor growth in ccRCCs relies on many factors that result from the loss of VHL. This study aims to identify new microRNAs with therapeutic potential for VHL-inactivated ccRCCs.

MATERIALS AND METHODS

We used 786O, A498 (VHL inactivated), and Caki-1 (VHL intact) ccRCC cell lines and 40 ccRCC samples and their adjacent nontumor tissues to measure the expression of microRNA-185 (miR-185) by real-time quantitative polymerase chain reaction. Overexpression or knockdown of VEGFA expression in renal cancer cells was fulfilled by transfecting expression plasmids or small interfering RNAs. Overexpression of miR-185 in ccRCC cell lines was fulfilled by transfecting chemically synthesized miR-185 mimics. The effects of miR-185 on ccRCC cell lines were detected by MTS assay, colony formation assay, and flow cytometric analysis.

RESULTS

Compared with adjacent nontumor renal tissues, miR-185 expression levels decreased significantly in ccRCC tissues. The expression of miR-185 had a negative correlation with tumor size, Fuhrman grade, and TNM staging. Luciferase assay showed that VEGFA was a direct target gene of miR-185. The overexpression of miR-185 significantly inhibited cell proliferation and induced cell apoptosis by down-regulating VEGFA expression in VHL-inactivated ccRCC cells.

CONCLUSIONS

Our results suggest that the miR-185, as a tumor suppressor, plays a pivotal role by inhibiting VEGFA in VHL-inactivated ccRCC.

MicroRNAs in renal cell carcinoma: a systematic review of clinical implications (Review)

Despite recent advances in the understanding of the biology of renal cell carcinoma (RCC), successful surgical treatment and implementation of novel-targeted therapies, the prognosis for RCC patients remains poor. Late presentation, tumor heterogeneity and in particular the lack of molecular biomarkers for early detection, classification and the surveillance of RCC treatments are major obstacles. The increasing knowledge regarding the functional role of microRNAs (miRNAs) in pathophysiological processes may provide an important link to the identification of suitable therapeutic targets and diagnostic/prognostic biomarkers for RCC. The aim of this review was to provide new insight into the function of miRNAs in the pathogenesis of RCC and to emphasize their potential as diagnostic and prognostic markers, as well as therapeutic targets.

Over-expression of cofilin-1 suppressed growth and invasion of cancer cells is associated with up-regulation of let-7 microRNA

Cofilin-1, a non-muscle isoform of actin regulatory protein that belongs to the actin-depolymerizing factor (ADF)/cofilin family is known to affect cancer development. Previously, we found that over-expression of cofilin-1 suppressed the growth and invasion of human non-small cell lung cancer (NSCLC) cells in vitro. In this study, we further investigated whether over-expression of cofilin-1 can suppress tumor growth in vivo, and performed a microRNA array analysis to better understand whether specific microRNA would be involved in this event. The results showed that over-expression of cofilin-1 suppressed NSCLC tumor growth using the xenograft tumor model with the non-invasive reporter gene imaging modalities. Additionally, cell motility and invasion were significantly suppressed by over-expressed cofilin-1, and down-regulation of matrix metalloproteinase (MMPs) -1 and -3 was concomitantly detected. According to the microRNA array analysis, the let-7 family, particularly let-7b and let-7e, were apparently up-regulated among 248 microRNAs that were affected after over-expression of cofilin-1 up to 7 days. Knockdown of let-7b or let-7e using chemical locked nucleic acid (LNA) could recover the growth rate and the invasion of cofilin-1 over-expressing cells. Next, the expression of c-myc, LIN28 and Twist-1 proteins known to regulate let-7 were analyzed in cofilin-1 over-expressing cells, and Twist-1 was significantly suppressed under this condition. Up-regulation of let-7 microRNA by over-expressed cofilin-1 could be eliminated by co-transfected Twist-1 cDNA. Taken together, current data suggest that let-7 microRNA would be involved in over-expression of cofilin-1 mediated tumor suppression in vitro and in vivo.

Role of miR-100 in the radioresistance of colorectal cancer cells

The prognosis of radioresistant colorectal cancer (CRC) is generally poor. Abnormal expression of microRNAs (miRNAs) is involved in the radiosensitivity of various tumor cells as these RNAs regulate biological signaling pathways. However, radioresistance-associated miRNAs in CRC have not yet been identified. In this study, we filtered out HCT116 and CCL-244 from seven CRC cell lines that showed the highest difference in radiosensitivity in a clonogenic assay. MiRNA sequencing identified 33 differentially expressed miRNAs (13 up-regulated and 20 down-regulated) in CCL-244 and 37 in HCT116 (20 up-regulated and 17 down-regulated) cells. MiR-100 was significantly down-regulated in CCL-244 cells after X-ray irradiation but not in HCT116 cells. Quantitative real-time PCR showed that the expression of miR-100 in CRC tissues was significantly lower than that in normal tissues. Thus, miR-100 seems to be involved in the radioresistance of CCL-244 cells. MiR-100 up-regulation sensitized CCL-244 cells to X-ray irradiation, which probably led to apoptosis and DNA double-strand breaks in these. In conclusion, to our knowledge, this is the first study to show that miR-100 may play an important role in regulating the radiosensitivity of CRC, and it may act as a new clinical target for CRC radiotherapy.

miR-185-3p regulates nasopharyngeal carcinoma radioresistance by targeting WNT2B in vitro

Aberrant microRNA (miRNA) expression contributes to a series of malignant cancer behaviors, including radioresistance. Our previous study showed differential expression of miR-185-3p in post-radiation nasopharyngeal carcinoma (NPC) cells. To investigate the role of miR-185-3p in NPC radioresistance, CNE-2 and 5-8F cells were transfected with miR-185-3p mimic and miR-185-3p inhibitor, respectively. CCK-8 assay and colony formation experiment confirmed that the expression of miR-185-3p affected the radioresistance of NPC cells. A negative correlation between miR-185-3p and WNT2B expression was observed in NPC cells and tissues. Luciferase reporter assays confirmed that miR-185-3p directly targeted the coding region of WNT2B. Furthermore, we found radioresistance decreased in WNT2B-silenced NPC cells. Activation of the WNT2B/β-catenin pathway was accompanied by epithelial-mesenchymal transition biomarker changes in NPC. We concluded that miR-185-3p contributed to the radioresistance of NPC via modulation of WNT2B expression in vitro.

Crosstalk between kinases, phosphatases and miRNAs in cancer

Reversible phosphorylation of proteins, performed by kinases and phosphatases, is the major post translational protein modification in eukaryotic cells. This intracellular event represents a critical regulatory mechanism of several signaling pathways and can be related to a vast array of diseases, including cancer. Cancer research has produced increasing evidence that kinase and phosphatase activity can be compromised by mutations and also by miRNA silencing, performed by small non-coding and endogenously produced RNA molecules that lead to translational repression. miRNAs are believed to target about one-third of human mRNAs while a single miRNA may target about 200 transcripts simultaneously. Regulation of the phosphorylation balance by miRNAs has been a topic of intense research over the last years, spanning topics going as far as cancer aggressiveness and chemotherapy resistance. By addressing recent studies that have shown miRNA expression patterns as phenotypic signatures of cancers and how miRNA influence cellular processes such as apoptosis, cell cycle control, angiogenesis, inflammation and DNA repair, we discuss how kinases, phosphatases and miRNAs cooperatively act in cancer biology.

miRNAs in tumor radiation response: bystanders or participants?

There is increasing interest in defining a functional association between miRNAs and tumor radiation response, with the double aim of rationally designing miRNA-based strategies to increase patient radiosensitivity and identifying novel biomarkers of treatment response. Although it has been demonstrated that several miRNAs directly regulate the expression of components of cell pathways relevant to radiosensitivity, and miRNA expression profiles change upon irradiation, understanding the causal role exerted by individual miRNAs in determining tumor radiation response is still at an early stage. Based on available experimental and clinical evidence, we discuss here the potential of miRNAs as targets and/or tools for modulating radioresponsivity at the clinical level, as well as possible predictive biomarkers, underlining present limits and future perspectives.

Correlation between gene expression and mutator phenotype predicts homologous recombination deficiency and outcome in ovarian cancer

New strategies are needed to predict response to platinum-based chemotherapy and outcome of ovarian cancers. We hypothesized that the mutator phenotype in the cancer genome represents the overuse of alternative DNA repair mechanisms, which might be a sign of homologous recombination (HR) deficiency and can be captured by gene expression. Multidimensional data of ovarian cancer patients and breast cancer patients from The Cancer Genome Atlas (TCGA) database were used for the development and validation of a potential clinical information-independent score that correlates with HR deficiency and predicts outcome. Correlation of the score with platinum response, outcome, and BRCA mutations was assessed. The score correlated with increased genomic mutation rate in both ovarian cancer and breast cancer cases that harbored a substantial subset of HR-deficient samples. Significantly improved outcomes were observed in the high-scoring group versus the low-scoring group in the TCGA dataset and in three large gene expression microarray datasets. A strong correlation was found between the score and the likelihood of achieving complete response to chemotherapy. The score was also found to be highly robust to noises in genomic mutations. Sixty-four patients harboring BRCA mutations were successfully divided into two groups based on scores, with the high-scoring group showing significantly improved outcomes compared with wild-type cases and the low-scoring group showing no significance in all the same analyses. The score was significantly correlated with the response to platinum therapy and outcome. Evaluation of the score as a prognostic tool in ovarian cancer patients is warranted.

KEY MESSAGE

We develop a diagnostic signature for the HR-deficiency based on a novel hypothesis. HR-deficiency score is significantly correlated to platinum therapy and outcomes. HRDS was validated by its association with OS, PFS, DFS and CR in validation datasets. Evaluation of the score as a prognostic tool in ovarian cancer patients is warranted.

Modulation of microRNAs by ionizing radiation in human gastric cancer

Gastric cancer is one of the most common cancers in China. Although surgery is the primary therapeutic method, radiotherapy has become an integral part, particularly in the early and intermediate stages of gastric cancer. microRNAs (miRNAs) are involved in the regulation of diverse cellular processes in response to intrinsic and extrinsic stress. A change in miRNA expression profile has been identified in various types of tumor cells in response to radiation; however, there is no relevant information concerning gastric cancer. In the present study, we investigated the miRNA profiles of two clinical gastric cancer samples exposed to X‑rays using miRNA microarray. We found that 16 miRNAs were downregulated and 2 miRNAs were upregulated significantly in both irradiated samples when compared with the unirradiated samples. Decreases in the levels of miR‑300 and miR‑642 expression were confirmed by qRT‑PCR in more clinical samples and in cultured cell lines. We predicted the targets of the two miRNAs with TargetScan and classified all the candidate targets with Gene Ontology, which indicated that both miR‑300 and miR‑642 potentially regulate cellular radiation response by modulating apoptosis, cell cycle regulation and DNA damage and repair pathway-related genes. Cell cycle assay and immunofluorescence assay demonstrated that miR‑300 regulates radiation‑induced G2 cell cycle arrest and DNA damage repair. In conclusion, our findings indicate that ionizing radiation modulates the miRNA expression profile, and the changes in several specific miRNAs such as miR‑300 have the potential to be used in the treatment, diagnosis and prognosis of gastric cancer.

microRNA expression and biogenesis in cellular response to ionizing radiation

Increasing evidence demonstrates that the expression levels of microRNAs (miRNAs) significantly change upon ionizing radiation (IR) and play a critical role in cellular response to IR. Although several radiation responsive miRNAs and their targets have been identified, little is known about how miRNAs expression and biogenesis is regulated by IR-caused DNA damage response (DDR). Hence, in this review, we summarize miRNA expression and biogenesis in cellular response to IR and mainly elucidate the regulatory mechanisms of miRNA expression and biogenesis from different aspects including ataxia-telangiectasia mutated (ATM) kinase, p53/p63/p73 family and other potential factors. Furthermore, we focus on ΔNp73, which might be a potential regulator of miRNA expression and biogenesis in cellular response to IR. miRNAs could effectively activate the IR-induced DDR and modulate the radiation response and cellular radiosensitivity, which have an important potential clinical application. Therefore, thoroughly understanding the regulatory mechanisms of miRNAs expression and biogenesis in radiation response will provide new insights for clinical cancer radiotherapy.

Selective targeting of the G2/M cell cycle checkpoint to improve the therapeutic index of radiotherapy

Despite tremendous advances in radiotherapy techniques, allowing dose escalation to tumour tissues and sparing of organs at risk, cure rates from radiotherapy or chemoradiotherapy remain suboptimal for most cancers. In tandem with our growing understanding of tumour biology, we are beginning to appreciate that targeting the molecular response to radiation-induced DNA damage holds great promise for selective tumour radiosensitisation. In particular, approaches that inhibit cell cycle checkpoint controls offer a means of exploiting molecular differences between tumour and normal cells, thereby inducing so-called cancer-specific synthetic lethality. In this overview, we discuss cellular responses to radiation-induced damage and discuss the potential of using G2/M cell cycle checkpoint inhibitors as a means of enhancing tumour control rates.

MicroRNAs in IgA nephropathy

IgA nephropathy is globally the most common primary glomerulonephritis, but the pathogenesis of this condition is still only partially understood. MicroRNAs (miRNAs) are short, noncoding RNA molecules that regulate gene expression. Genome-wide analysis of renal miRNA expression has identified a number of novel miRNAs related to immunological and pathological changes. Specifically, overexpression of miR-148b might explain the aberrant glycosylation of IgA1, which has a central pathogenetic role in the early phase of IgA nephropathy. By contrast, miR-29c is an antifibrotic miRNA that is probably important in the late stages of disease progression. In addition, urinary levels of several miRNAs are significantly changed in patients with IgA nephropathy compared with healthy individuals; some alterations seem to be disease-specific, whereas others are apparently damage-related. As miRNAs in urinary sediment are relatively stable and easily quantified, they have the potential to be used as biomarkers for the diagnosis and monitoring of disease. However, to date, limited data are available on the role of miRNAs in the pathogenesis of IgA nephropathy and their potential application as biomarkers. Consequently, further studies are urgently needed to address this shortfall. Here, we review the available literature on miRNAs in relation to IgA nephropathy.

MicroRNAs in the DNA Damage/Repair Network and Cancer

Cancer is a multistep process characterized by various and different genetic lesions which cause the transformation of normal cells into tumor cells. To preserve the genomic integrity, eukaryotic cells need a complex DNA damage/repair response network of signaling pathways, involving many proteins, able to induce cell cycle arrest, apoptosis, or DNA repair. Chemotherapy and/or radiation therapy are the most commonly used therapeutic approaches to manage cancer and act mainly through the induction of DNA damage. Impairment in the DNA repair proteins, which physiologically protect cells from persistent DNA injury, can affect the efficacy of cancer therapies. Recently, increasing evidence has suggested that microRNAs take actively part in the regulation of the DNA damage/repair network. MicroRNAs are endogenous short noncoding molecules able to regulate gene expression at the post-transcriptional level. Due to their activity, microRNAs play a role in many fundamental physiological and pathological processes. In this review we report and discuss the role of microRNAs in the DNA damage/repair and cancer.

The advance of application for microRNAs in cancer gene therapy

MicroRNAs (miRNAs, miRs) are closely associated with biological processes of tumor cells as the key regulators by recognizing specific mRNA targets, and further mediating post-transcriptional inhibition of tumor related genes. Therefore, miRNAs may be used as optional therapeutic targets in tumors resulting from accumulation of multiple gene mutations and their interactions. Currently, there are many researches for making miRNAs safely and efficiently be applied in cancer gene therapy (CGT). This review summarizes miRNA anomalous biogenesis pathway, different roles in disease processes of tumors, by which it further clarifies miRNA implemented methods including the combined treatment related with miRNA in CGT; simultaneously, briefly illustrates the delivery systems of miRNA.