MicroRNA and cancer chemoprevention

Exosomal MiR-4261 mediates calcium overload in RBCs by downregulating the expression of ATP2B4 in multiple myeloma

Background

Hypercalcemia induced by multiple myeloma (MM) affects the biological functions of excitable and non-excitable cells. However, red blood cells (RBCs) regulatory effect on calcium in hypercalcemia is still not fully understood.

Methods

A total of 113 patients with MM osteolytic lesions were studied retrospectively. Flow cytometry and atomic absorption spectroscopy were used to detect calcium content. Immunofluorescence and Western blotting were used to investigate protein expression. GEO and miRNA databases were used to screen miRNAs. Exosomal miR-4261 migration was investigated by Transwell assay. Dual-luciferase assays confirmed the targeting relationship between miR-4261 and ATP2B4. An RBC oxidative stress model was constructed, and Omega-Agatoxin IVA was used to study the role of plasma membrane Ca²⁺-ATPase 4 (PMCA4) in RBCs.

Results

The results showed that MM RBCs had calcium overload, and serum calcium levels increased as the number of RBCs decreased. The expression of PMCA4 in MM RBCs was significantly lower than in normal RBCs. The exosomal miR-4261 produced by MM cells could be transferred to RBCs to downregulate the expression of ATP2B4.

Conclusions

Studies have confirmed that RBCs experience calcium overload in MM with osteolytic lesions, which is related to the downregulation of ATP2B4 by MM exosomal miR-4261.

Sulindac Modulates the Response of Proficient MMR Colorectal Cancer to Anti-PD-L1 Immunotherapy

Immune-checkpoint inhibitor (ICI) therapy has been widely used to treat different human cancers, particularly advanced solid tumors. However, clinical studies have reported that ICI immunotherapy benefits only ∼15% of patients with colorectal cancer, specifically those with tumors characterized by microsatellite instability (MSI), a molecular marker of defective DNA mismatch repair (dMMR). For the majority of patients with colorectal cancer who carry proficient MMR (pMMR), ICIs have shown little clinical benefit. In this study, we examined the efficacy of sulindac to enhance the response of pMMR colorectal cancer to anti-PD-L1 immunotherapy. We utilized a CT26 syngeneic mouse tumor model to compare the inhibitory effects of PD-L1 antibody (Ab), sulindac, and their combination on pMMR colorectal cancer tumor growth. We found that mice treated with combination therapy showed a significant reduction in tumor volume, along with increased infiltration of CD8+ T lymphocytes in the tumor tissues. We also demonstrated that sulindac could downregulate PD-L1 by blocking NF-κB signaling, which in turn led to a decrease in exosomal PD-L1. Notably, PD-L1 Ab can be bound and consumed by exosomal PD-L1 in the blood circulation. Therefore, in combination therapy, sulindac downregulating PD-L1 leads to increased availability of PD-L1 Ab, which potentially improves the overall efficacy of anti-PD-L1 therapy. We also show that low-dose sulindac does not appear to have a systemic inhibitory effect on prostaglandin E2 (PGE2). In conclusion, our findings provide unique insights into the mechanism of action and efficacy for sulindac as an immunomodulatory agent in combination with anti-PD-L1 therapy for the treatment of pMMR colorectal cancer.

MicroRNAs are involved in the development and progression of gastric cancer

MicroRNAs (miRNAs) are recognized as an essential component of the RNA family, exerting multiple and intricate biological functions, particularly in the process of tumorigenesis, proliferation, and metastatic progression. MiRNAs are altered in gastric cancer (GC), showing activity as both tumor suppressors and oncogenes, although their true roles have not been fully understood. This review will focus upon the recent advances of miRNA studies related to the regulatory mechanisms of gastric tumor cell proliferation, apoptosis, and cell cycle. We hope to provide an in-depth insight into the mechanistic role of miRNAs in GC development and progression. In particular, we summarize the latest studies relevant to miRNAs' impact upon the epithelial-mesenchymal transition, tumor microenvironment, and chemoresistance in GC cells. We expect to elucidate the molecular mechanisms involving miRNAs for better understanding the etiology of GC, and facilitating the development of new treatment regimens for the treatment of GC.

MicroRNA-486-3p functions as a tumor suppressor in oral cancer by targeting DDR1

BACKGROUND

Discoidin domain receptor-1 (DDR1) tyrosine kinase is highly expressed in a variety of human cancers and involved in various steps of tumorigenesis. However, the precise mechanisms underlying the abnormal expression of DDR1 in oral squamous cell carcinoma (OSCC) has not been well investigated.

METHODS

The expression of DDR1 on OSCC patients was determine by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. Specific targeting by miRNAs was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-486-3p and DDR1 were accessed by MTT and Annexin V analyses using gain- and loss-of-function approaches. Chromatin immunoprecipitation (ChIP) and methylation specific PCR (MSP) were performed to explore the molecular mechanisms by arecoline treatment.

RESULTS

Here, we reported that DDR1 was significantly upregulated in OSCC tissues and its levels were inversely correlated with miR-486-3p expression. The experimental results in vitro confirmed that miR-486-3p decreased DDR1 expression by targeting the 3'-UTR of DDR1 mRNA. Overexpression of miR-486-3p led to growth inhibition and apoptosis induction with a similar function by knockdown of DDR1. Aberrant methylation of ANK1 promoter was a highly prevalent in OSCC and contributes to oral carcinogenesis by epigenetic silencing of ANK1 and miR-486-3p. We found that miR-486-3p can be transcriptionally co-regulated with its host gene ANK1 through epigenetic repression. DNA methylation inhibitor treatment re-expressed ANK1 and miR-486-3p. Importantly, arecoline, a major betel nut alkaloid, recruited DNMT3B binding to ANK1 promoter for DNA methylation and then attenuated the expression of miR-486-3p in OSCC.

CONCLUSION

This study was the first to demonstrate that betel nut alkaloid may recruit DNMT3B to regulate miR-486-3p/DDR1 axis in oral cancer andmiR-486-3p and DDR1 may serve as potential therapeutic targets of oral cancer.

Potential tumor‑suppressive role of microRNA‑99a‑3p in sunitinib‑resistant renal cell carcinoma cells through the regulation of RRM2

Sunitinib is the most common primary molecular‑targeted agent for metastatic clear cell renal cell carcinoma (ccRCC); however, intrinsic or acquired sunitinib resistance has become a significant problem in medical practice. The present study focused on microRNA (miR)‑99a‑3p, which was significantly downregulated in clinical sunitinib‑resistant ccRCC tissues in previous screening analyses, and investigated the molecular network associated with it. The expression levels of miR‑99a‑3p and its candidate target genes were evaluated in RCC cells, including previously established sunitinib‑resistant 786‑o (SU‑R‑786‑o) cells, and clinical ccRCC tissues, using reverse transcription‑quantitative polymerase chain reaction. Gain‑of‑function studies demonstrated that miR‑99a‑3p significantly suppressed cell proliferation and colony formation in RCC cells, including the SU‑R‑786‑o cells, by inducing apoptosis. Based on in silico analyses and RNA sequencing data, followed by luciferase reporter assays, ribonucleotide reductase regulatory subunit‑M2 (RRM2) was identified as a direct target of miR‑99a‑3p in the SU‑R‑786‑o cells. Loss‑of‑function studies using small interfering RNA against RRM2 revealed that cell proliferation and colony growth were significantly inhibited via induction of apoptosis, particularly in the SU‑R‑786‑o cells. Furthermore, the RRM2 inhibitor Didox (3,4‑dihydroxybenzohydroxamic acid) exhibited anticancer effects in the SU‑R‑786‑o cells and other RCC cells. To the best of our knowledge, this is the first report demonstrating that miR‑99a‑3p directly regulates RRM2. Identifying novel genes targeted by tumor‑suppressive miR‑99a‑3p in sunitinib‑resistant RCC cells may improve our understanding of intrinsic or acquired resistance and facilitate the development of novel therapeutic strategies.

miR-223 increases gallbladder cancer cell sensitivity to docetaxel by downregulating STMN1

Background

MicroRNAs (miRs) are involved in cancer carcinogenesis, and certain regulatory miRs could provide promising therapeutic methods for refractory malignancies, such as gallbladder cancer (GBC). miR-223 was found to play a pivotal role in enhancing chemotherapeutic effects, therefore evoking interest in the role of miR-223 in GBC.

Results

miR-223 was decreased in GBC tissues and cell lines, and ectopic miR- 223 expression exhibited multiple anti-tumorigenic effects in GBC cells, including decreased proliferation, migration and invasion in vitro. However, treatment with a miR-223 inhibitor increased cell viability. We determined that STMN1 was negatively correlated with and regulated by miR-223 in GBC. miR-223 increased GBC sensitivity to docetaxel in vitro and in vivo, and the induced sensitivity to docetaxel was suppressed by the restoration of STMN1 expression.

Methods

We examined miR-223 expression in GBC tissue and GBC cell lines using qRT-PCR. The effects of modulated miR-223 expression in GBC cells were assayed using Cell Counting Kit-8 (CCK8), flow cytometry, and wound-healing and invasion assays. Susceptibility to docetaxel was evaluated in miR-223/STMN1-modulated GBC cells and xenograft tumor models. The protein expression of relevant genes was examined by Western blotting.

Conclusions

These findings indicated that miR-223 might serve as an onco-suppressor that enhances susceptibility to docetaxel by downregulating STMN1 in GBC, highlighting its promising therapeutic value.

RUNX3 regulates renal cell carcinoma metastasis via targeting miR-6780a-5p/E-cadherin/EMT signaling axis

Runt-related transcription factor 3 (RUNX3) is a tumor suppressor in many human solid tumors. In this study, renal cell carcinoma (RCC) microarray analysis showed that the level of RUNX3 expression was lower in RCC tissue than in adjacent normal renal tissues, and was correlated with depth of invasion (pT stage) (P<0.001) and Tumor Node Metastasis (TNM) stage (P<0.001). RUNX3 expression was negatively correlated with poor 5-year overall and disease-free patient survival. RUNX3 suppressed RCC metastasis and invasion and increased levels of E-cadherin, an important marker of epithelial-mesenchymal transition, in vitro and in vivo. RUNX3 also inhibited microRNA-6780a-5p, which directly targeted the E-cadherin 3'untranslated region and decreased its expression. We confirmed that miR-6780a-5p mimics abrogated RUNX3-mediated E-cadherin upregulation and RCC metastasis/invasion inhibition. Thus, RUNX3 targeted the miR-6780a-5p/E-cadherin/EMT signaling axis to suppress renal carcinoma cell migration and invasion. This pathway illustrates a new RUNX3 function and provides potential targets for the treatment of RUNX3 mutant and loss-of-function RCC tumors. RUNX3 may also act as an effective prognostic indicator in RCC.

RUNX3 regulates hepatocellular carcinoma cell metastasis via targeting miR-186/E-cadherin/EMT pathway

Runt-related transcription factor 3 (RUNX3) has been reported as a tumor suppressor in some kinds of cancers. In the present study, hepatocellular carcinoma (HCC) microarray analysis showed that RUNX3 expression was significantly lower in HCC tissues compared with that in adjacent non-tumor tissues, and was negatively associated with metastasis and TNM stage. RUNX3 was an independently prognostic factor for 5-year overall and disease-free patient survival. Mechanically, RUNX3 repressed metastasis and invasion of HCC, and increased E-cadherin expression. RUNX3 also repressed microRNA-186 to increase E-cadherin expression. We demonstrated that miR-186 mimics attenuated RUNX3-induced increase of E-cadherin and inhibition of metastasis and invasion. In conclusion, RUNX3 suppressed HCC cell migration and invasion by targeting the miR-186/E-cadherin/EMT pathway. RUNX3 may be recommended as an effective prognostic indicator and therapeutic target for patients with HCC.

Inhibition of breast cancer cell motility with a non-cyclooxygenase inhibitory derivative of sulindac by suppressing TGFβ/miR-21 signaling

Compelling efficacy on intervention of tumorigenesis by nonsteroidal anti-inflammatory drugs (NSAIDs) has been documented intensively. However, the toxicities related to cyclooxygenase (COX) inhibition resulting in suppression of physiologically important prostaglandins limit their clinical use for human cancer chemoprevention. A novel derivative of the NSAID sulindac sulfide (SS), referred as sulindac sulfide amide (SSA), was recently developed, which lacks COX inhibitory activity, yet shows greater suppressive effect than SS on growth of various cancer cells. In this study, we focus on the inhibitory activity of SSA on breast tumor cell motility, which has not been studied previously. Our results show that SSA treatment at non-cytotoxic concentrations can specifically reduce breast tumor cell motility without influencing tumor cell growth, and the mechanism of action involves the suppression of TGFβ signaling by directly blocking Smad2/3 phosphorylation. Moreover, miR-21, a well-documented oncogenic miRNA for promoting tumor cell metastasis, was also found to be involved in inhibitory activity of SSA in breast tumor cell motility through the modulation of TGFβ pathway. In conclusion, we demonstrate that a non-COX inhibitory derivative of sulindac can inhibit breast tumor metastasis by a mechanism involving the TGFβ/miR-21 signaling axis.

miR-196b/miR-1290 participate in the antitumor effect of resveratrol via regulation of IGFBP3 expression in acute lymphoblastic leukemia

MicroRNAs play critical roles in the progression of acute lymphoblastic leukemia (ALL). Previous studies have indicated that miR-196b and miR-1290 play critical roles in T-cell ALL (T-ALL) and B-cell ALL (B-ALL), respectively. Resveratrol, a natural edible polyphenolic phytoalexin, possesses certain anticancer activities. Nevertheless, the mechanism involved in the regulation of ALL by resveratrol is still poorly understood. The present study aimed to reveal the potential mechanism underlying the antitumor effect of resveratrol in ALL focusing on miRNAs. Research indicates that insulin-like growth factor binding protein 3 (IGFBP3) plays a critical role in the aetiology of ALL. In the present study, we first demonstrated that the expression of IGFBP3 was decreased in ALL patients. We further identified that miR-196b and miR-1290 were overexpressed in T-ALL TALL-104 and B-ALL SUP-B15 cell lines, respectively. Moreover, resveratrol markedly decreased the overexpression of miR-196b/miR-1290 and elevated IGFBP3 expression in the ALL cell lines. As an miR-196b/miR-1290 inhibitor, resveratrol was further demonstrated to exert antitumor effects on ALL cells including antiproliferation, cell cycle arrest, apoptosis and inhibition of migration. Dual-luciferase reporter assay revealed that miR-196b/miR-1290 directly bound to the 3'-untranslated (3'-UTR) region of IGFBP3 mRNA. Moreover, we observed that IGFBP3 short interfering RNA reversed the antitumor activity of resveratrol against ALL cells. Taken together, the present study provides evidence that resveratrol targets miR-196b and miR-1290 for its antitumor activity in T-ALL and B-ALL, respectively. The present study also confirms that both miR‑196b and miR-1290 target the IGFBP3 3'-UTR and are potential therapeutic targets for ALL.

miRNA-411 acts as a potential tumor suppressor miRNA via the downregulation of specificity protein 1 in breast cancer

The expression and functions of microRNA (miR)-411 have been investigated in several types of cancer. However, until now, miR-411 in human breast cancer has not been examined. The present study investigated the expression, biological functions and molecular mechanisms of miR‑411 in human breast cancer, discussing whether it offers potential as a therapeutic biomarker for breast cancer in the future. The expression levels of miR‑411 in human breast cancer tissues and cells were measured using reverse transcription‑quantitative polymerase chain reaction analysis. Following transfection with miR‑411 mimics, an MTT assay, cell migration and invasion assay, western blot analysis and luciferase assay were performed in human breast cancer cell lines. According to the results, it was found that miR‑411 was significantly downregulated in breast cancer, and associated with lymph node metastasis and histological grade. Additionally, it was observed that miR‑411 suppressed cell growth, migration and invasion in the breast cancer cells. The present study also provided the first evidence, to the best of our knowledge, that miR‑411 was likely to directly target specificity protein 1 in breast cancer. These findings indicated that miR‑411 may be used a therapeutic biomarker for the treatment of breast cancer in the future.

miR-375 exhibits a more effective tumor-suppressor function in laryngeal squamous carcinoma cells by regulating KLF4 expression compared with simple co-transfection of miR-375 and miR-206

MicroRNAs (miRNAs) are reported to be important regulators of cancer-related processes, and function either as oncogenes or as tumor-suppressor genes. It was found that miR-375 was downregulated in samples of laryngeal squamous cell carcinomas (LSCCs) as compared to the level noted in adjacent non-tumor tissues, and it was inversely correlated with T grade, lymph node metastases and clinical tumor stage. Overexpression of miR-375 led to a decreased protein level of Krüppel-like factor 4 (KLF4) and marked suppression of the proliferation and invasion, and induced apoptosis of LSCC cell line Hep-2 using Cell Counting Kit-8, Transwell chamber and cell cycle assays. In addition, we examined the influence of the upregulation of miR-206 alone and upregulation of both miR-375 and miR-206 on the expression of KLF4 and Hep-2 cell behavior. The results showed that compared with the function of miR-375 in tumor suppression by regulating KLF4, co-transfection of miR-375 and miR-206 exhibited a less effective inhibitory effect not only on tumor cell proliferation and invasion, but also on tumor cell apoptosis. Taken together, miR-375 is possibly a tumor suppressor in LSCC by regulating KLF4. In addition, simple overexpression of several miRNAs did not entail higher efficacy than a single miRNA, similar to co-transfecions of miR-375 and miR-206.

Hepatic Premalignant Alterations Triggered by Human Nephrotoxin Aristolochic Acid I in Canines

Aristolochic acid I (AAI) existing in plant drugs from Aristolochia species is an environmental human carcinogen associated with urothelial cancer. Although gene association network analysis demonstrated gene expression profile changes in the liver of human TP53 knock-in mice after acute AAI exposure, to date, whether AAI causes hepatic tumorigenesis is still not confirmed. Here, we show that hepatic premalignant alterations appeared in canines after a 10-day AAI oral administration (3 mg/kg/day). We observed c-Myc oncoprotein and oncofetal RNA-binding protein Lin28B overexpressions accompanied by cancer progenitor-like cell formation in the liver by AAI exposure. Meanwhile, we found that forkhead box O1 (FOXO1) was robustly phosphorylated, thereby shuttling into the cytoplasm of hepatocytes. Furthermore, utilizing microarray and qRT-PCR analysis, we confirmed that microRNA expression significantly dysregulated in the liver treated with AAI. Among them, we particularly focused on the members in let-7 miRNAs and miR-23a clusters, the downstream of c-Myc and IL6 receptor (IL6R) signaling pathway linking the premalignant alteration. Strikingly, when IL6 was added in vitro, IL6R/NF-κB signaling activation contributed to the increase of FOXO1 phosphorylation by the let-7b inhibitor. Therefore, it highlights the new insight into the interplay of the network in hepatic tumorigenesis by AAI exposure, and also suggests that anti-premalignant therapy may be crucial for preventing AAI-induced hepatocarcinogenesis.

New concepts and challenges in the clinical translation of cancer preventive therapies: the role of pharmacodynamic biomarkers

Implementation of therapeutic cancer prevention strategies has enormous potential for reducing cancer incidence and related mortality. Trials of drugs including tamoxifen and aspirin have led the way in demonstrating proof-of-principle that prevention of breast and colorectal cancer is feasible. Many other compounds ranging from drugs in widespread use for various indications, including metformin, bisphosphonates, and vitamin D, to dietary agents such as the phytochemicals resveratrol and curcumin, show preventive activity against several cancers in preclinical models. Notwithstanding the wealth of opportunities, major challenges have hindered the development process and only a handful of therapies are currently approved for cancer risk reduction. One of the major obstacles to successful clinical translation of promising preventive agents is a lack of pharmacodynamic biomarkers to provide an early read out of biological activity in humans and for optimising doses to take into large scale randomised clinical trials. A further confounding factor is a lack of consideration of clinical pharmacokinetics in the design of preclinical experiments, meaning results are frequently reported from studies that use irrelevant or unachievable concentrations. This article focuses on recent findings from investigations with dietary-derived agents to illustrate how a thorough understanding of the mechanisms of action, using models that mimic the clinical scenario, together with the development of compound-specific accompanying pharmacodynamic biomarkers could accelerate the developmental pipeline for preventive agents and maximise the chances of success in future clinical trials. Moreover, the concept of a bell-shaped dose-response curve for therapeutic cancer prevention is discussed, along with the need to rethink the traditional ‘more is better’ approach for dose selection.

miR-122 inhibits cancer cell malignancy by targeting PKM2 in gallbladder carcinoma

Gallbladder cancer (GBC) is one of the lethal diseases of digestive system. Increasing evidence prompt that microRNAs (miRs) might provide a novel therapeutical target for malignant disease. The antitumor effect of miR-122 to GBC is worth to be investigated. miR-122 expression level in GBC tissue sample and cell lines were assayed by qRT-PCR. miR-122 mimics were transfected for upregulation of miR-122 expression. Cell function was assayed by CCK8, flow cytometry, wound healing assay, migration assay, and invasion assay. The target genes of miR-122 were predicated by TargetScan online program and verified by western blot and luciferase report gene assay. miR-122 was decreased in GBC tissue and cell lines. The exogenous introduction of miR-122 exhibits multiple antitumor effect in GBC cell proliferation, invasion, and metastasis. Further studies revealed that the PKM2 was a regulative target of miR-122 in GBC cell. miR-122 also inhibits TGF-β-induced epithelium mesenchymal transformation of GBC cell by downregulating PKM2 expression. These findings suggest that miR-122 plays an important role in tumorigenesis of GBC through interfering PKM2, highlighting its usefulness as a potential therapeutic agent in GBC.

MicroRNA-338-3p functions as tumor suppressor in breast cancer by targeting SOX4

MicroRNA-338-3p (miR‑338-3p), a recently discovered miRNA, has been reported to be downregulated and play tumor suppressor roles in gastric cancer, ovarian cancer, colorectal carcinoma and lung cancer by targeting several genes. However, the role and potential mechanism of miR‑338-3p in breast cancer (BC) is still unclear. In the present study, we investigated the roles and mechanisms of miR‑338-3p in human breast cancer. miR‑338-3p expression was determined by qRT-PCR in human BC cell lines, and clinical significantly of miR‑338-3p expression was further evaluated. Furthermore, the function of miR‑338-3p in breast cancer also was investigated by several in vitro approaches and in nude mouse models. Luciferase assay and western blot analysis were performed to validate the potential targets of miR‑338-3p after the preliminary screening by employing open access software. It was found that miR‑338-3p was significantly downregulated in both BC tissues and cell lines and the low expression of miR‑338-3p was inversely correlated with lymph node metastatic and TNM stage status (P<0.01). Function assay showed that the overexpression of miR‑338-3p in BC cells significantly inhibited cell proliferation, colony formation, migration and invasion, and induced cell apoptosis and cell cycle arrest at G1/G0 stage, as well as suppressed tumor growth in the nude mouse model. Luciferase assay and western blot analysis identified sex-determining region Y-box 4 (SOX4) as a direct and functional target of miR‑338-3p. These findings revealed that miR‑338-3p may act as a tumor suppressor in breast cancer by targeting SOX4, suggesting miR‑338-3p as a novel strategy for breast cancer treatment.

Silencing of miRNA-148a by hypermethylation activates the integrin-mediated signaling pathway in nasopharyngeal carcinoma

MicroRNAs (miRNAs) play a pivotal role in carcinogenesis by suppressing oncogenes or tumor suppressor genes. Various studies have identified numerous miRNAs and their diverse targets; however, the consequences of dysregulated miRNAs in nasopharyngeal carcinoma (NPC) remain unclear. For this study, we found that miR-148a is downregulated through hypermethylation in NPC biopsies and NPC cell lines compared with adjacent normal and NP cells respectively. Promoter assays demonstrated that upstream stimulatory factor 1 (USF1) is a crucial transcription factor that activates miR-148a promoter activity. EMSA assays confirmed that purified USF1 binds better toward the unmethylated than the methylated CG-containing USF1 consensus probe. The ectopic expression of miR-148a inhibits cell migration in NPC cells through the suppression of integrin-mediated signaling by targeting VAV2, WASL and ROCK1. Biochemical and functional assays provided supporting evidence that these 3 genes are the downstream targets of miR-148a in NPC cells. Furthermore, immunohistochemical staining and Western blotting analysis revealed that the 3 oncogenic targets of miR-148a were overexpressed in NPC biopsies, suggesting that the inactivation of miR-148a caused by DNA methylation promotes NPC progression. Overall, our findings revealed that miR-148a can act as tumor suppressor miRNA and serve as a biomarker as well as a therapeutic target for NPC.

MiR-375 targets KLF4 and impacts the proliferation of colorectal carcinoma

MiR-375 has been identified as oncogenes or tumor suppressor genes which has the potential to the development and growth of cancers. However, the limited information concerning the expression and role of miR-375 in colorectal cancer (CRC) is available. In this work, we provide evidence for a function of miR-375 in the inhibition of CRC proliferation. Here, we showed that miR-375, down-modulated in human colorectal cancer tissues compared with normal human colon tissues, including several colorectal cancer cell lines. Subsequently, using the luciferase reporter assays, we found that the KLF4 untranslated region (3'UTR) carries the direct binding site of miR-375. In terms of function in vitro, CCK-8 assay, colony formation assay, and cell cycle assay demonstrated that the overexpression of miR-375 suppressed CRC cell proliferation. Inhibition of KLF4 performed similar effects with miR-375 overexpression on CRC cells, and overexpression of KLF4 could significantly reverse the tumor suppressive effects of miR-375 on CRC cells. Furthermore, we found overexpressed miR-375 effectively repressed tumor growth via KLF4 in xenograft animal experiment. Taken together, these results illustrated that miR-375 depresses proliferation of CRC through regulating 3'UTR of KLF4 mRNA, which might be a promising therapeutic target for treating colorectal cancers.

MiR-200b expression in breast cancer: a prognostic marker and act on cell proliferation and apoptosis by targeting Sp1

MicroRNAs (miRNAs) have been identified as important post-transcriptional regulators involved in various biological and pathological processes of cells. In the present study, we investigated the roles and mechanisms of miR-200b in human breast cancer (BC). MiR-200b expression was carried out by qRT-PCR in human BC cell lines and clinical samples and the prognostic potential of miR-200b expression was further evaluated. In vitro, effects of miR-200b on BC cell proliferation, apoptosis and cell cycle distribution were tested by CCK-8 kit, flow cytometric analysis respectively. Luciferase assay and Western blot analysis were performed to validate the potential targets of miR-200b after the preliminary screening by employing open access software. We found that miR-200b was significantly down-regulated in both BC tissues and cell lines. The low expression of miR-200b was correlated with late TNM stage, negative oestrogen receptor and positive HER-2 status. Multivariate analysis showed that miR-200b expression was an independent prognostic predictor for BC patients. Integrated analysis identified Sp1 as a direct and functional target of miR-200b. Knockdown of Sp1 inhibited cell proliferation, induce apoptosis and act on cell cycle resembling that of miR-200b high expression. Our data demonstrates that miR-200b has potential to serve as prognostic biomarker and tumour suppressor for BC patients. As a direct and functional target of miR-200b, Sp1 and miR-200b both could be an exciting target for BC treatment strategy.

MicroRNAs: New players in cancer prevention targeting Nrf2, oxidative stress and inflammatory pathways

miRNAs are endogenous small non-coding RNAs of 20-22 nucleotides that repress gene expression at the post-transcriptional level. There is growing interest in the role of miRNAs in cancer chemoprevention, and several naturally occurring chemopreventive agents have been found to be modulators of miRNA expression both in vitro and in vivo. Moreover, these chemopreventive phytochemicals commonly possess anti-oxidative and/or anti-inflammatory properties, and Nrf2 has been extensively studied as a molecular target in cancer prevention. The crosstalk between miRNAs and the traditional cellular signaling pathways of chemoprevention remain to be fully elucidated. This review summarizes the data regarding the potential interactions between miRNAs and anti-oxidative and anti-inflammatory pathways. Cellular redox homeostasis can affect the biogenesis and processing of miRNAs, which in turn regulate the Nrf2 pathway of detoxifying/anti-oxidative genes. We also discuss the miRNA regulatory mechanisms in relation to inflammation-related cancer signaling pathways.

MicroRNA expression profile of bromocriptine-resistant prolactinomas

MicroRNAs (miRNA) have been implicated in the resistance of tumors to chemotherapy. However, little is known about miRNA expression in bromocriptine-resistant prolactinomas. In this study, 23 prolactinoma samples were classified as bromocriptine-sensitive or -resistant according to the clinical definition of bromocriptine resistance, and their miRNA expression profiles were determined using Solexa sequencing. We found 41 miRNAs that were differentially expressed between the two groups, and 12 of these were validated by stem-loop qRT-PCR. Hsa-mir-93, hsa-mir-17, hsa-mir-22*, hsa-mir-126*, hsa-mir-142-3p, hsa-mir-144*, hsa-mir-486-5p, hsa-mir-451, and hsa-mir-92a were up-regulated and hsa-mir-30a, hsa-mir-382, and hsa-mir-136 were down-regulated in bromocriptine-resistant prolactinomas in comparison with bromocriptine-sensitive prolactinomas. Furthermore, silencing of mir-93 significantly increased the sensitivity of MMQ cells to dopamine agonist treatment. Mir-93 directly affected p21 expression in MMQ cells by targeting the 3'-UTR. Our study is the first to identify a miRNA expression profile associated with bromocriptine-resistant prolactinoma.

A miR-30d antisense oligonucleotide inhibits proliferation and promotes apoptosis of colon cancer cells

AIM: To investigate the expression of miR-30d in colon cancer tissues and the effect of a miR-30d antisense oligonucleotide (ASO) on the proliferation and apoptosis of colon cancer cells.

METHODS: The expression of miR-30d in 102 colon cancer tissues and matched tumor-adjacent tissues was detected by real-time quantitative PCR. After colon cancer cells were transfected with a miR-30d ASO, cell proliferation and apoptosis were measured by MTT assay, colony formation assay and flow cytometry.

RESULTS: miR-30d was overexpressed in 52.94% (54/102) of colon cancer tissues, and the positive rate of miR-30d overexpression was significantly higher in colon cancer tissues than in tumor-adjacent colon tissues (P < 0.05). Transfection of miR-30d ASO significantly reduced the expression of miR-30d (P < 0.05), decreased cell survival at 24, 48 and 96 h (all P < 0.05), inhibited colony formation (P < 0.05), and increased apoptosis (P < 0.05) compared with control cells. In addition, the expression of Bcl-2 mRNA and protein was significantly decreased after the expression of miR-30d was down-regulated.

CONCLUSION: MiR-30d is overexpressed in human colon cancer. Inhibition of the expression of miR-30d can effectively inhibit growth and promotes apoptosis of colon cancer cells. MiR-30d may become a new target for the regulation of gene expression in colon cancer.