MicroRNA-552 deficiency mediates 5-fluorouracil resistance by targeting SMAD2 signaling in DNA-mismatch-repair-deficient colorectal cancer. Cancer Chemother Pharmacol. 2019;84:427-439. [PMID: 31087138 DOI: 10.1007/s00280-019-03866-7]

Thiostrepton suppresses triple-negative breast cancer through downregulating c-FLIP/SMAD2/3 signaling pathway

Triple-negative breast cancer (TNBC) is an aggressive subtype with poor prognosis of breast cancer. Thiostrepton exerts anti-tumor activities against several cancers including TNBC. Herein we discussed the new molecular mechanisms of thiostrepton in TNBC. Thiostrepton inhibited MDA-MB-231 cell viability, accompanied by a decrease of c-FLIP and p-SMAD2/3. c-FLIP overexpression reduced the sensitivity of MDA-MB-231 cells to thiostrepton, while SMAD2/3 knockdown increased the sensitivity of MDA-MB-231 cells to thiostrepton. Moreover, c-FLIP overexpression significantly increased the expression and phosphorylation of SMAD2/3 proteins and vice versa. In conclusion, our study reveals c-FLIP/SMAD2/3 signaling pathway as a novel mechanism of antitumor activity of thiostrepton.

RHBDF1 modulates cisplatin sensitivity of small cell lung cancer through YAP1/Smad2 signaling pathway

Small cell lung cancer (SCLC) is a fatal tumor type that is prone to drug resistance. In our previous study, we showed that human rhomboid-5 homolog-1 (RHBDF1) was differentially expressed in 5 intrinsic cisplatin-resistant SCLC tissues compared with 5 intrinsic cisplatin-sensitive SCLC tissues by RNA sequencing, which intrigued us. We performed gain- and loss-of-function experiments to investigate RHBDF1 function, bioinformatics analysis, qRT-PCR, western blotting, and immunoprecipitation to elucidate the molecular mechanisms as well as detect RHBDF1 expression in SCLC by immunohistochemistry. We found that RHBDF1 knockdown promoted cell proliferation and cisplatin chemoresistance and inhibited apoptosis in vitro and in vivo. These effects could be reversed by overexpressing RHBDF1 in vitro. Mechanistically, RHBDF1 interacted with YAP1, which increased the phosphorylation of Smad2 and transported Smad2 to the nucleus. Among clinical specimens, the RHBDF1 was a low expression in SCLC and was associated with clinicopathological features and prognosis. We are the first to reveal that RHBDF1 inhibited cell proliferation and promoted cisplatin sensitivity in SCLC and elucidate a novel mechanism through RHBDF1/YAP1/Smad2 signaling pathway which played a crucial role in cisplatin chemosensitivity. Targeting this pathway can be a promising therapeutic strategy for chemotherapy resistance in SCLC.

Deciphering the functional landscape and therapeutic implications of noncoding RNAs in the TGF-β signaling pathway in colorectal cancer: A comprehensive review

Colorectal cancer (CRC) remains a major global health concern, necessitating an in-depth exploration of the intricate molecular mechanisms underlying its progression and potential therapeutic interventions. Transforming Growth Factor-β (TGF-β) signaling, a pivotal pathway implicated in CRC plays a dual role as a tumor suppressor in the early stages and a promoter of tumor progression in later stages. Recent research has shed light on the critical involvement of noncoding RNAs (ncRNAs) in modulating the TGF-β signaling pathway, introducing a new layer of complexity to our understanding of CRC pathogenesis. This comprehensive review synthesizes the current state of knowledge regarding the function and therapeutic potential of various classes of ncRNAs, including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs), in the context of TGF-β signaling in CRC. The intricate interplay between these ncRNAs and key components of the TGF-β pathway is dissected, revealing regulatory networks that contribute to the dynamic balance between tumor suppression and promotion. Emphasis is placed on how dysregulation of specific ncRNAs can disrupt this delicate equilibrium, fostering CRC initiation, progression, and metastasis. Moreover, the review provides a critical appraisal of the emerging therapeutic strategies targeting ncRNAs associated with TGF-β signaling in CRC. The potential of these ncRNAs as diagnostic and prognostic biomarkers is discussed, highlighting their clinical relevance. Additionally, the challenges and prospects of developing RNA-based therapeutics, such as RNA interference and CRISPR/Cas-based approaches, are explored in the context of modulating TGF-β signaling for CRC treatment. In conclusion, this review offers a comprehensive overview of the intricate interplay between ncRNAs and the TGF-β signaling pathway in CRC. By unraveling the functional significance of these regulatory elements, we gain valuable insights into the molecular landscape of CRC, paving the way for the development of novel and targeted therapeutic interventions aimed at modulating the TGF-β signaling cascade through the manipulation of ncRNAs.

The Critical Function of microRNAs in Developing Resistance against 5- Fluorouracil in Cancer Cells

Although there have been significant advancements in cancer treatment, resistance and recurrence in patients make it one of the leading causes of death worldwide. 5-fluorouracil (5-FU), an antimetabolite agent, is widely used in treating a broad range of human malignancies. The cytotoxic effects of 5-FU are mediated by the inhibition of thymidylate synthase (TYMS/TS), resulting in the suppression of essential biosynthetic activity, as well as the misincorporation of its metabolites into RNA and DNA. Despite its huge benefits in cancer therapy, the application of 5-FU in the clinic is restricted due to the occurrence of drug resistance. MicroRNAs (miRNAs) are small, non-coding RNAs that act as negative regulators in many gene expression processes. Research has shown that changes in miRNA play a role in cancer progression and drug resistance. This review examines the role of miRNAs in 5-FU drug resistance in cancers.

The Role of the Transforming Growth Factor-β Signaling Pathway in Gastrointestinal Cancers

Transforming growth factor-β (TGF-β) has attracted attention as a tumor suppressor because of its potent growth-suppressive effect on epithelial cells. Dysregulation of the TGF-β signaling pathway is considered to be one of the key factors in carcinogenesis, and genetic alterations affecting TGF-β signaling are extraordinarily common in cancers of the gastrointestinal system, such as hereditary nonpolyposis colon cancer and pancreatic cancer. Accumulating evidence suggests that TGF-β is produced from various types of cells in the tumor microenvironment and mediates extracellular matrix deposition, tumor angiogenesis, the formation of CAFs, and suppression of the anti-tumor immune reaction. It is also being considered as a factor that promotes the malignant transformation of cancer, particularly the invasion and metastasis of cancer cells, including epithelial-mesenchymal transition. Therefore, elucidating the role of TGF-β signaling in carcinogenesis, cancer invasion, and metastasis will provide novel basic insight for diagnosis and prognosis and the development of new molecularly targeted therapies for gastrointestinal cancers. In this review, we outline an overview of the complex mechanisms and functions of TGF-β signaling. Furthermore, we discuss the therapeutic potentials of targeting the TGF-β signaling pathway for gastrointestinal cancer treatment and discuss the remaining challenges and future perspectives on targeting this pathway.

miR-552 promotes the proliferation and metastasis of intrahepatic cholangiocarcinoma by targeting FOXO1

Intrahepatic cholangiocarcinoma (ICC) is a relatively rare but highly malignant cancer. Few effective systemic targeted therapies are available for patients with unresectable ICC, but there exists an urgent need to explore mechanisms underlying the initiation and progression of ICC. MicroRNA (miRNA) plays vital roles in the initiation, progression, and drug resistance of different cancers. Recently, the biological function of a novel miRNA, miR-552, has been widely analyzed in hepatocellular carcinoma and colorectal, cervical, gastric, and other cancers. However, its role in ICC has not yet been elucidated. In this study, we found that miR-552 expression was upregulated in ICC and that miR-552 predicted poor prognosis. Using functional studies, we found that miR-552 enhanced the proliferation and invasion ability of ICC cells. Mechanistic research identified that forkhead box O1 (FOXO1) is the target of miR-552 in ICC. Moreover, the combined panels of miR-552 and FOXO1 exhibited a better prognostic value for ICC patients than did miR-552 alone. In conclusion, these findings demonstrated that the miR-552/FOXO1 axis drove ICC progression, further suggesting that targeting this axis could be a novel therapeutic strategy for ICC.

HMGA2 regulation by miRNAs in cancer: affecting cancer hallmarks and therapy response

High mobility group A 2 (HMGA2) is a protein that modulates the structure of chromatin in the nucleus. Importantly, aberrant expression of HMGA2 occurs during carcinogenesis, and this protein is an upstream mediator of cancer hallmarks including evasion of apoptosis, proliferation, invasion, metastasis, and therapy resistance. HMGA2 targets critical signaling pathways such as Wnt/β-catenin and mTOR in cancer cells. Therefore, suppression of HMGA2 function notably decreases cancer progression and improves outcome in patients. As HMGA2 is mainly oncogenic, targeting expression by non-coding RNAs (ncRNAs) is crucial to take into consideration since it affects HMGA2 function. MicroRNAs (miRNAs) belong to ncRNAs and are master regulators of vital cell processes, which affect all aspects of cancer hallmarks. Long ncRNAs (lncRNAs) and circular RNAs (circRNAs), other members of ncRNAs, are upstream mediators of miRNAs. The current review intends to discuss the importance of the miRNA/HMGA2 axis in modulation of various types of cancer, and mentions lncRNAs and circRNAs, which regulate this axis as upstream mediators. Finally, we discuss the effect of miRNAs and HMGA2 interactions on the response of cancer cells to therapy. Regarding the critical role of HMGA2 in regulation of critical signaling pathways in cancer cells, and considering the confirmed interaction between HMGA2 and one of the master regulators of cancer, miRNAs, targeting miRNA/HMGA2 axis in cancer therapy is promising and this could be the subject of future clinical trial experiments.

Clinical significance of neoadjuvant chemotherapy for locally advanced colorectal cancer patients with deficient mismatch repair: possibly residual value in the era of immunotherapy

Background

Deficient mismatch repair (dMMR) or microsatellite instability is one of the well-established molecular biomarkers in colorectal cancer (CRC). The efficiency of neoadjuvant chemotherapy (NAC) in locally advanced colorectal cancer (LACC) patients with dMMR is unclear.

Objectives

We assessed the tumor response and clinical outcome in LACC patients with dMMR received NAC.

Design

Retrospective, single-center analysis.

Methods

From 2013 to 2018, a total of 577 LACC patients with dMMR who underwent radical surgery were identified. Among them, 109 patients who received adjuvant chemotherapy were further screened out for analysis. According to whether receiving NAC or not, 109 patients were divided into two groups with the purpose of retrospectively analyzing their characteristics, treatment, and survival results, especially the 5-year disease-free survival (DFS) and 5-year overall survival.

Results

Baseline characteristics were matched between the two groups. One of 40 patients in NAC group recurred, while 13 of 69 patients in non-NAC group recurred. Univariate and multivariate analyses showed that NAC (hazard ratio: 0.115; 95% confidence interval: 0.015-0.897; p = 0.039) was independent influence factor for DFS. In NAC group, there were 13/40 (32.5%) patients for tumor regression grade 1 and 27/40 (67.5%) patients converted clinical positive N-stage into negative N-stage.

Conclusion

In this study, NAC was associated with better tumor downstaging and longer 5-year DFS in LACC patients with dMMR. Consequently, NAC might be an additional treatment choice when it comes to such patients in the future.

Bioinformatics analysis of downstream circRNAs and miRNAs regulated by Runt-related transcription factor 1 in papillary thyroid carcinoma

BACKGROUND

This study sought to clarify the role of Runt-related transcription factor 1's (RUNX1's) regulation of downstream circular ribonucleic acid (circRNA) in the occurrence and development of papillary thyroid carcinoma (PTC) and to explore its mechanism of action.

METHODS

The levels of RUNX1 were analyzed in PTC tumor tissues and adjacent non-tumor tissues in different types and at different stages via reverse-transcription quantitative polymerase chain reaction (RT-qPCR). The expression pattern and functional role of RUNX1 were analyzed in PTC cells via RT-qPCR, Western blotting, and Transwell assays. This study explored the differential expression of circRNA and microRNA (miRNA) in cells after knocking down RUNX1 through high-throughput sequencing and examined the changes in downstream signaling pathways through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses.

RESULTS

RUNX1 was upregulated in PTC tissues, and the expression levels of RUNX1 were related to PTC stage. The knockdown of RUNX1 inhibited the proliferation, migration, and invasion of cells. The high-throughput sequencing results showed that after RUNX1 knockdown, 29 circRNAs (11 upregulated and 18 downregulated) and 20 miRNAs (8 upregulated and 12 downregulated) had the most significant differential expression. The GO analysis of the differential circRNA downstream genes showed that the iron channel-related pathways, endosomal transport, learning, and memory pathways had the largest number of differential genes, and the most significant changes. The KEGG analysis showed that there were 2 pathways with P values <0.05; that is, the glycosaminoglycan synthesis and transcription dysregulation pathways. The GO analysis of the differential miRNA downstream genes showed that the protein binding and cytoplasmic pathways had the largest number of differential genes and the greatest level of difference. The KEGG analysis showed that the tumor-related pathways, phosphatidylinositol-3-kinase and protein kinase B, glycoprotein, cytoskeleton, Ras, and Rap1 pathways changed the most significantly.

CONCLUSIONS

RUNX1 is highly expressed in PTC. We conducted high-throughput sequencing to analyze the effect of knocking down RUNX1 on the levels of circRNA and miRNA in PTC. The GO and KEGG analyses revealed that the iron channel-related pathways, endosomal transport, learning and memory, glycosaminoglycan synthesis, and transcriptional disorder-related signaling pathways were enriched.

Linc00261 Inhibited High-Grade Serous Ovarian Cancer Progression through miR-552-ATG10-EMT Axis

In recent years, long non-coding RNAs (lncRNAs) play an important role in a multitude of pathways across species; however, their functions are still unknown. In this study, we demonstrate that Linc00261 is downregulation in high-grade serous ovarian cancer (HGSOC) and can inhibit cell proliferation and migration of high-grade serous ovarian cancer cells. We further validate the targeting interactions among Linc00261, miR-552, and ATG10. Interestingly, they all play important roles for regulating epithelial-mesenchymal transition (EMT) progression. Collectively, these findings suggest that Linc00261, a mediator of EMT progression, can target oncogenic miR-552, elevating ATG10 expression, to prevent high-grade serous ovarian cancer tumorigenesis and may serve as a potential novel therapeutic target.

TGF-β Signaling and Resistance to Cancer Therapy

The transforming growth factor β (TGF-β) pathway, which is well studied for its ability to inhibit cell proliferation in early stages of tumorigenesis while promoting epithelial-mesenchymal transition and invasion in advanced cancer, is considered to act as a double-edged sword in cancer. Multiple inhibitors have been developed to target TGF-β signaling, but results from clinical trials were inconsistent, suggesting that the functions of TGF-β in human cancers are not yet fully explored. Multiple drug resistance is a major challenge in cancer therapy; emerging evidence indicates that TGF-β signaling may be a key factor in cancer resistance to chemotherapy, targeted therapy and immunotherapy. Finally, combining anti-TGF-β therapy with other cancer therapy is an attractive venue to be explored for the treatment of therapy-resistant cancer.

The role of non-coding RNAs in chemotherapy for gastrointestinal cancers

Gastrointestinal (GI) cancers, including colorectal, gastric, hepatic, esophageal, and pancreatic tumors, are responsible for large numbers of deaths around the world. Chemotherapy is the most common approach used to treat advanced GI cancer. However, chemoresistance has emerged as a critical challenge that prevents successful tumor elimination, leading to metastasis and recurrence. Chemoresistance mechanisms are complex, and many factors and pathways are involved. Among these factors, non-coding RNAs (ncRNAs) are critical regulators of GI tumor development and subsequently can induce resistance to chemotherapy. This occurs because ncRNAs can target multiple signaling pathways, affect downstream genes, and modulate proliferation, apoptosis, tumor cell migration, and autophagy. ncRNAs can also induce cancer stem cell features and affect the epithelial-mesenchymal transition. Thus, ncRNAs could possibly act as new targets in chemotherapy combinations to treat GI cancer and to predict treatment response.

Regulatory role of the transforming growth factor-β signaling pathway in the drug resistance of gastrointestinal cancers

Gastrointestinal (GI) cancer, including esophageal, gastric, and colorectal cancer, is one of the most prevalent types of malignant carcinoma and the leading cause of cancer-related deaths. Despite significant advances in therapeutic strategies for GI cancers in recent decades, drug resistance with various mechanisms remains the prevailing cause of therapy failure in GI cancers. Accumulating evidence has demonstrated that the transforming growth factor (TGF)-β signaling pathway has crucial, complex roles in many cellular functions related to drug resistance. This review summarizes current knowledge regarding the role of the TGF-β signaling pathway in the resistance of GI cancers to conventional chemotherapy, targeted therapy, immunotherapy, and traditional medicine. Various processes, including epithelial-mesenchymal transition, cancer stem cell development, tumor microenvironment alteration, and microRNA biogenesis, are proposed as the main mechanisms of TGF-β-mediated drug resistance in GI cancers. Several studies have already indicated the benefit of combining antitumor drugs with agents that suppress the TGF-β signaling pathway, but this approach needs to be verified in additional clinical studies. Moreover, the identification of potential biological markers that can be used to predict the response to TGF-β signaling pathway inhibitors during anticancer treatments will have important clinical implications in the future.

Decreased expression of miR-3135b reduces sensitivity to 5-fluorouracil in colorectal cancer by direct repression of PIM1

5-Fluorouracil (5-FU)-based chemotherapy is the conventional treatment approach for patients with colorectal cancer (CRC). However, de novo and acquired resistance to 5-FU are frequently observed during treatment, which eventually lead to patients succumbing to the disease. Accumulating data have revealed an association of CRC resistance to 5-FU with aberrant expression of microRNAs (miRs). In the present study, Cell Counting Kit-8 was performed to measure cell viability, flow cytometry was performed to detect cell apoptosis, reverse transcription-quantitative PCR was conducted to measure proviral integration site for Moloney murine leukemia virus 1 (PIM1) and miR-3135b expression, western blotting was conducted to measure PIM1 expression. Microarray data analysis indicated that the level of miR-3135b expression was decreased in patients with recurrent CRC that were treated with 5-FU when compared with non-recurrent cases. Overexpression of miR-3135b increased the sensitivity of CRC cells to 5-FU treatment. Moreover, PIM1 was identified as a target gene of miR-3135b using bioinformatics analysis, reverse transcription-quantitative PCR and western blotting. The direct interaction between these two targets was confirmed by luciferase reporter assays. Notably, PIM1 overexpression compensated the effect of miR-3135b in CRC cells. Furthermore, an inverse correlation between PIM1 mRNA expression levels and miR-3135b expression was observed in clinical samples. Therefore, the present study identified miR-3135b as a novel regulator of 5-FU sensitivity in CRC.

5-Fluorouracil: A Narrative Review on the Role of Regulatory Mechanisms in Driving Resistance to This Chemotherapeutic Agent

5-fluorouracil (5-FU) is among the mostly administrated chemotherapeutic agents for a wide variety of neoplasms. Non-coding RNAs have a central impact on the determination of the response of patients to 5-FU. These transcripts via modulation of cancer-related pathways, cell apoptosis, autophagy, epithelial-mesenchymal transition, and other aspects of cell behavior can affect cell response to 5-FU. Modulation of expression levels of microRNAs or long non-coding RNAs may be a suitable approach to sensitize tumor cells to 5-FU treatment via modulating multiple biological signaling pathways such as Hippo/YAP, Wnt/β-catenin, Hedgehog, NF-kB, and Notch cascades. Moreover, there is an increasing interest in targeting these transcripts in various kinds of cancers that are treated by 5-FU. In the present article, we provide a review of the function of non-coding transcripts in the modulation of response of neoplastic cells to 5-FU.

FOXM1-induced miR-552 expression contributes to pancreatic cancer progression by targeting multiple tumor suppressor genes

Dysregulation of microRNAs (miRNAs) plays important roles during carcinogenesis. Forkhead box M1 (FOXM1), a well-known oncogenic transcription factor, has been implicated in the progression of multiple cancer types. To find out FOXM1-induced abnormal miRNAs in pancreatic cancer, we analyzed TCGA database and figured out miR-552 as the most relevant miRNA with FOXM1. Molecular experimental results demonstrated that FOXM1 transcriptionally activated miR-552 expression by directly binding to the promoter region of miR-552. In a pancreatic cancer tissue microarray, miR-552 expression was positively correlated with FOXM1 and high expression of miR-552 could predict poor patient outcome. Functionally, overexpression of miR-552 promoted pancreatic cancer cell migration and inhibition of miR-552 attenuated this phenotype. The inhibitory effect on cell migration caused by FOXM1 knockdown could be restored by exogenous expression of miR-552. By informatics analysis, we identified three tumor suppressor genes: DACH1, PCDH10 and SMAD4, all of which were negatively associated with FOXM1 and validated as functionally relevant targets of miR-552. Taken together, our findings provide a new FOXM1-miR-552-DACH1/PCDH10/SMAD4 axis to regulate pancreatic cancer cell progression and new opportunities for therapeutic intervention against this disease.

MicroRNA-Based Therapeutics for Drug-Resistant Colorectal Cancer

Although therapeutic approaches for patients with colorectal cancer (CRC) have improved in the past decades, the problem of drug resistance still persists and acts as a major obstacle for effective therapy. Many studies have shown that drug resistance is related to reduced drug uptake, modification of drug targets, and/or transformation of cell cycle checkpoints. A growing body of evidence indicates that several microRNAs (miRNAs) may contribute to the drug resistance to chemotherapy, targeted therapy, and immunotherapy by regulating the drug resistance-related target genes in CRC. These drug resistance-related miRNAs may be used as promising biomarkers for predicting drug response or as potential therapeutic targets for treating patients with CRC. In this review, we summarized the recent discoveries regarding anti-cancer drug-related miRNAs and their molecular mechanisms in CRC. Furthermore, we discussed the challenges associated with the clinical application of miRNAs as biomarkers for the diagnosis of drug-resistant patients and as therapeutic targets for CRC treatment.

Molecular determinants of response to 5-fluorouracil-based chemotherapy in colorectal cancer: The undisputable role of micro-ribonucleic acids

5-flurouracil (5-FU)-based chemotherapy is the main pharmacological therapy for advanced colorectal cancer (CRC). Despite significant progress in the treatment of CRC during the last decades, 5-FU drug resistance remains the most important cause of failure in CRC therapy. Resistance to 5-FU is a complex and multistep process. Different mechanisms including microsatellite instability, increased expression level of key enzyme thymidylate synthase and its polymorphism, increased level of 5-FU-activating enzymes and mutation of TP53 are proposed as the main determinants of resistance to 5-FU in CRC cells. Recently, micro-ribonucleic acids (miRNA) and their alterations were found to have a crucial role in 5-FU resistance. In this regard, the miRNA-mediated mechanisms of 5-FU drug resistance reside among the new fields of pharmacogenetics of CRC drug response that has not been completely discovered. Identification of the biological markers that are related to response to 5-FU-based chemotherapy is an emerging field of precision medicine. This approach will have an important role in defining those patients who are most likely to benefit from 5-FU-based chemotherapy in the future. Thereby, the identification of 5-FU drug resistance mechanisms is an essential step to predict and eventually overcome resistance. In the present comprehensive review, we will summarize the latest knowledge regarding the molecular determinants of response to 5-FU-based chemotherapy in CRC by emphasizing the role of miRNAs.

miR-552: an important post-transcriptional regulator that affects human cancer

MiR-552 is a small non-coding RNA located on chromosome 1p34.3, and its expression level is significantly up-regulated in tissues or cells of various tumors. miR-552 can target multiple genes. These targeted genes play important regulatory roles in biological processes such as gene transcription and translation, cell cycle progression, cell proliferation, apoptosis, cell migration, and invasion. Besides, miR-552 may affect the efficacy of various anticancer drugs by targeting genes such as TP53 and RUNX3. This review summarizes the biological functions and clinical expressions of miR-552 in human cancer. Our goal is to explore the potential value of miR-552 in the diagnosis, prognosis, and treatment of human cancer.

MicroRNAs and Their Influence on the ZEB Family: Mechanistic Aspects and Therapeutic Applications in Cancer Therapy

Molecular signaling pathways involved in cancer have been intensively studied due to their crucial role in cancer cell growth and dissemination. Among them, zinc finger E-box binding homeobox-1 (ZEB1) and -2 (ZEB2) are molecules that play vital roles in signaling pathways to ensure the survival of tumor cells, particularly through enhancing cell proliferation, promoting cell migration and invasion, and triggering drug resistance. Importantly, ZEB proteins are regulated by microRNAs (miRs). In this review, we demonstrate the impact that miRs have on cancer therapy, through their targeting of ZEB proteins. MiRs are able to act as onco-suppressor factors and inhibit the malignancy of tumor cells through ZEB1/2 down-regulation. This can lead to an inhibition of epithelial-mesenchymal transition (EMT) mechanism, therefore reducing metastasis. Additionally, miRs are able to inhibit ZEB1/2-mediated drug resistance and immunosuppression. Additionally, we explore the upstream modulators of miRs such as long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), as these regulators can influence the inhibitory effect of miRs on ZEB proteins and cancer progression.

MiR-185-3p mimic promotes the chemosensitivity of CRC cells via AQP5

BACKGROUND

Studies showed that microRNAs (miRNAs) are important regulators in drug resistance. The current study investigated the role of miR-185-3p and its predicted target gene AQP5 in 5-FU-insensitive colorectal cancer (CRC) cells.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) and Spearman's correlation analysis were conducted to determine the correlation of expression levels of miR-185-3p and AQP5 from CRC tissues. HCT-116 and HCT-8 cells were treated by gradient concentration of 5-FU to construct 5-FU-resistant CRC model. The inhibition and viability of 5-FU-resistant cells were detected by MTT assay, and cell migration and invasion ability were determined by wound healing and transwell assay. The expressions of miR-185-3p and AQP5 were measured by qRT-PCR. StarBase and dual-luciferase reporter assay were used to predict and confirm the interaction between miR-185-3p and AQP5. Further experiments were performed to explore the function of miR-185-3p in 5-FU-resistant cells through regulating aquaporin-5 (AQP5). The levels of EMT-associated markers and AQP5 were determined by conducting Western Blot and qRT-PCR.

RESULTS

We found that 5-FU-resistant CRC cells showed a lower inhibition rate, and higher migration and invasion abilities. MiR-185-3p was low-expressed in CRC tissues and 5-FU-resistance cells, and it targeted and regulated the expression of AQP5, which was found up-regulated in CRC and 5-FU-resistance CRC cells (r = -0.29, P < .05). Furthermore, miR-185-3p mimic enhanced the chemo-sensitivity of 5-FU-resistant cells, while overexpressed AQP5 reversed such an effect produced by miR-185-3p mimic.

CONCLUSION

MiR-185-3p mimic enhances the chemosensitivity of CRC cells via AQP5. Our research provides a potential therapeutic target for 5-FU-resistant CRC cells.

Upregulation of miR-552 Predicts Unfavorable Prognosis of Gastric Cancer and Promotes the Proliferation, Migration, and Invasion of Gastric Cancer Cells

BACKGROUND

Accumulating evidence indicates that micro-RNAs play a key role in tumor progression and prognosis. However, the overall biological role and clinical significance of microRNA-552 (miR-552) in the pathogenesis of gastric cancer (GC) remain unclear.

METHODS

miR-552 expression was measured in 122 pairs of cancerous and noncancerous tissues and cell lines by quantitative real-time polymerase chain reaction. The relationship between miR-552 and the clinical parameters of patients was analyzed by the χ2 test; Kaplan-Meier analysis and multivariate Cox regression analysis were used to predict the overall survival time and prognosis of patients with different expression of miR-552. Finally, CCK-8 and Transwell were used to detect the changes in cell proliferation, migration, and invasion ability.

RESULTS

miR-552 was expressed at markedly high levels in GC tissues compared to normal tissues and in some GC cell lines (p < 0.001). The upregulation of miR-552 was significantly associated with tumors with advanced TNM stage (p = 0.026), lymph node metastasis (p = 0.018), intestinal metaplasia (p = 0.044), and genomically stable subtype (p = 0.035). Moreover, GC patients with high miR-552 expression showed shorter overall survival (log-rank test, p = 0.011) than those with low expression. Meanwhile, miR-552 was an independent prognostic factor for GC patients (HR 5.657, 95% CI 1.619-19.761, p = 0.007). Finally, miR-552 overexpression promoted the proliferation, migration, and invasion of GC cells (p < 0.01).

CONCLUSION

Taken together, our results indicate that miR-552, as an oncogene of GC, can promote cell proliferation, migration, and invasion, and miR-552 may be a novel prognostic biomarker for GC.