miRNAs modulate the drug response of tumor cells

Role of microRNAs in Predicting the Prognosis of Cervical Cancer Cases: A Systematic Review and Meta-Analysis

Aim:

There is growing evidence for the possible use of microRNAs (miRNAs) in cancers as diagnostic as well as prognostic biomarkers in the present era of Personalized Medicine. The objective of the present systematic review and meta-analysis was to assess the prognostic role of microRNAs in uterine cervical cancers.

Methods:

A systematic review and meta-analysis was carried out searching electronic databases for published articles between January 2009 and August 2020 based on standard systematic review guidelines. Meta-analysis was performed by pooling the hazard ratio (HR) with 95% confidence interval (CI) to assess the prognostic value of deregulated miRNAs by the random-effects model.

Results:

In the present meta-analysis, the aberrant expression of 14 microRNAs in 1,526 uterine cervical cancer cases before definitive therapy from 14 case-control studies were assessed. The pooled HR of two miRNAs, miRNA-155 and miRNA-224 which were upregulated in cervical cancer tissues was 1.76 (95% CI 1.27-2.45) revealing significant association with overall poor survival. Meanwhile, the pooled HR was 1.53 (95% CI 0.94-2.94) when all the deregulated miRNAs in cervical cancer tissues were evaluated. The pooled HR of downregulated miRNAs was 1.46 (95% CI 0.81, 2.64). Meanwhile, the pooled HR of three upregulated miRNAs-425-5p, 196a, 205 in the serum sample was 1.37 (95% CI 0.45 -4.20).

Conclusion:

The downregulation of aberrant miRNAs was not associated with poor overall survival rates.

The Role of miRNAs, miRNA Clusters, and isomiRs in Development of Cancer Stem Cell Populations in Colorectal Cancer

MicroRNAs (miRNAs or miRs) have a critical role in regulating stem cells (SCs) during development and altered expression can cause developmental defects and/or disease. Indeed, aberrant miRNA expression leads to wide-spread transcriptional dysregulation which has been linked to many cancers. Mounting evidence also indicates a role for miRNAs in the development of the cancer SC (CSC) phenotype. Our goal herein is to provide a review of: (i) current research on miRNAs and their targets in colorectal cancer (CRC), and (ii) miRNAs that are differentially expressed in colon CSCs. MicroRNAs can work in clusters or alone when targeting different SC genes to influence CSC phenotype. Accordingly, we discuss the specific miRNA cluster classifications and isomiRs that are predicted to target the ALDH1, CD166, BMI1, LRIG1, and LGR5 SC genes. miR-23b and miR-92A are of particular interest because our previously reported studies on miRNA expression in isolated normal versus malignant human colonic SCs showed that miR-23b and miR-92a are regulators of the LGR5 and LRIG1 SC genes, respectively. We also identify additional miRNAs whose expression inversely correlated with mRNA levels of their target genes and associated with CRC patient survival. Altogether, our deliberation on miRNAs, their clusters, and isomiRs in regulation of SC genes could provide insight into how dysregulation of miRNAs leads to the emergence of different CSC populations and SC overpopulation in CRC.

Upregulation of let-7f-5p promotes chemotherapeutic resistance in colorectal cancer by directly repressing several pro-apoptotic proteins

Colorectal cancer (CRC) is one of the most frequently occurring primary malignant tumors worldwide. Chemotherapeutic resistance is a major clinical problem in the treatment of CRC. Therefore, it is of great importance to investigate novel biomarkers that may predict chemoresistance and facilitate the development of individualized treatment for patients with CRC. The present study reported that let-7f-5p expression was elevated in chemotherapy-resistant CRC tissues compared with chemotherapy-sensitive tissues. Furthermore, upregulating let-7f-5p increased the expression levels of the anti-apoptotic proteins, B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xL), and decreased the activity of caspase-3 and caspase-9 in CRC cells. By contrast, downregulating let-7f-5p yielded the opposite effect. Notably, the results indicated that let-7f-5p promoted chemotherapeutic resistance by directly repressing the expression of several pro-apoptotic proteins, including tumor protein p53, tumor protein p53-inducible nuclear protein 1, tumor protein p53-inducible nuclear protein 2 and caspase-3. Therefore, a novel mechanism by which let-7f-5p enhances the resistance of CRC cells to chemotherapeutics has been revealed, indicating that silencing let-7f-5p may become an effective therapeutic strategy against CRC.

A double-negative feedback loop between E2F3b and miR- 200b regulates docetaxel chemosensitivity of human lung adenocarcinoma cells

MicroRNAs (miRNAs) are non-coding small RNAs which negatively regulate gene expressions mainly through 3'-untranslated region (3'-UTR) binding of target mRNAs. Recent studies have highlighted the feedback loops between miRNAs and their target genes in physiological and pathological processes including chemoresistance of cancers. Our previous study identified miR-200b/E2F3 axis as a chemosensitivity restorer of human lung adenocarcinoma (LAD) cells. Moreover, E2F3b was bioinformatically proved to be a potential transcriptional regulator of pre-miR-200b gene promoter. The existance of this double-negative feedback minicircuitry comprising E2F3b and miR-200b was confirmed by chromatin immunoprecipitation (ChIP) assay, site-specific mutation and luciferase reporter assay. And the underlying regulatory mechanisms of this feedback loop on docetaxel resistance of LAD cells were further investigated by applying in vitro chemosensitivity assay, colony formation assay, flow cytometric analysis of cell cycle and apoptosis, as well as mice xenograft model. In conclusion, our results suggest that the double-negative feedback loop between E2F3b and miR-200b regulates docetaxel chemosensitivity of human LAD cells mainly through cell proliferation, cell cycle distribution and apoptosis.

The applications of liquid biopsy in resistance surveillance of anaplastic lymphoma kinase inhibitor

With the clinical promotion of precision medicine and individualized medical care, molecular targeted medicine has been used to treat non-small cell lung cancer (NSCLC) patients and proved to be significantly effective. Anaplastic lymphoma kinase (ALK) inhibitor is one of the most important specific therapeutic agents for patients with ALK-positive NSCLC. It can extend the survival of patients. However, resistance to the ALK inhibitor inevitably develops in the application process. So, the real-time resistance surveillance is particularly important, and liquid biopsy is one of the most potential inspection methods. Circulating tumor cells, circulating free tumor DNA and exosome in body fluid are used as the main detection biomarkers to reflect the occurrence of resistance in real time through sequencing or counting and then to guide the follow-up treatment.

MiR-1244 sensitizes the resistance of non-small cell lung cancer A549 cell to cisplatin

BACKGROUND

Cisplatin (DDP)-based chemotherapy is the mainstay of first-line therapy for lung cancer. However, their efficacy is often limited by the existence or development of chemoresistance. The aim of this study was to find and investigate the function of miRNAs in cisplatin (DDP)-resistant non-small cell lung cancer (NSCLC) A549 cell.

METHODS

Quantitative real-time PCR assay was employed to compare the differences of miRNA expression in both cisplatin-resistant A549 (A549/DDP) cell and the parental A549 cell. The dysregulated miRNAs were then corrected by transfecting oligonucleotides into A549/DDP cells. The cellular sensitivity to cisplatin, cell apoptosis and migration were conducted by MTT, flow cytometry and cell wound healing assay, respectively.

RESULTS

Both miR-589 and miR-1244 were significantly down-regulated in A549/DDP cell compared to the parental A549, while the expression of miR-182 and miR-224 were increased in A549/DDP cell (P < 0.05). Importantly, transfection of the cisplatin-resistant cells with either miR-589 or miR-1244 resulted in an increased sensitivity to cisplatin, indicating that the dysregulated miRNA may play an important role in chemotherapy resistance in cancer cell. The rescued expression of miRNA also reduced cell invasion and increased apoptosis of A549/DDP cell.

CONCLUSION

The study indicates a crucial role of miR-1244 in the progress of cisplatin resistance of A549. Further understanding of miR-1244-mediated signaling pathways may promote the clinical use of miR-1244 in lung cancer therapy.

MicroRNA-related single-nucleotide polymorphism of XPO5 is strongly correlated with the prognosis and chemotherapy response in advanced non-small-cell lung cancer patients

This study was performed to investigate if the microRNA-related single-nucleotide polymorphisms (miR-SNPs) of XPO5 gene predicted the prognosis and pathological features of advanced non-small-cell lung cancer patients receiving chemotherapy. A total of 131 advanced non-small-cell lung cancer (NSCLC) patients were recruited. MicroRNA (miRNA) binding site prediction software was adopted for the prediction and screening of SNPs in XPO5 and miRNA binding regions. Polymerase chain reaction (PCR) amplification was further performed. Time-dependent survival-free curves were constructed using the Kaplan-Meier technique. Univariate and the multivariate survival analyses were conducted for confirmation of prognostic factor for advanced NSCLC patients receiving chemotherapy. There were no significant differences of SNP distribution frequencies between groups, without statistical significance (P > 0.05). Included clinical pathological features and chemotherapy regimens showed no apparent statistical significance in influencing the curative effect of chemotherapy in advanced NSCLC patients (all P > 0.05). While the objective response rate (ORR) in patients who carried AA and AC genotype was 35.48 and 51.22 %, respectively, with statistically significant difference (P < 0.05). Univariate survival analysis indicated that patients who carried AA genotype showed a significantly lower 5-year survival rate to those who carried AC genotype (P < 0.05). And, considering pathological features, statistical significance was found in patients with different pathological types, lymph node metastasis, differentiation degree, T staging, and pathological staging (all P < 0.05). Multivariate analysis results indicated that the SNP sites of rs11077 might be an independent prognostic factor of advanced NSCLC patients receiving chemotherapy (risk ratio [RR] = 0.346; 95 % confidence interval [95 % CI] = 0.174-0.685, P = 0.002). Other clinical features were all considered to have no apparent effect in influencing the prognostic outcomes of advanced NSCLC patients receiving chemotherapy except lymph node metastasis (P < 0.05). miR-SNP rs11077 of XPO5 may be independently connected with the prognosis and chemotherapy response of advanced NSCLC patients, and patients with AC genotype have relatively improved prognostic outcomes and better curative effect of chemotherapy than those with AA allele of XPO5. Further, lymph node metastasis may be also involved in influencing the prognosis of advanced NSCLC patients.

Low miR-145 expression level is associated with poor pathological differentiation and poor prognosis in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the first cause of cancer related death in the world. Biomarkers to predict the relapse and drug resistance could be extremely useful for a clinical doctor to monitor high risk patients and select rational regimen. miRNAs play an important role in lung cancer and detection samples are relatively easy to be obtained, miRNAs could become a promising means of comprehending the oncogenesis and pathogenesis of lung cancer. This study aimed to investigate the function of miR-145 to work as a biomarker in NSCLC. miR-145 expression level in 48 NSCLC tumor tissues and their matched normal tissues were detected by qRT-PCR. miR-145 in 18 paraffin-embedded samples underwent chemotherapy and were assessed by in situ hybridization (ISH). Here we show that miR-145 was down-regulated in NSCLC tissues; down-regulation of miR-145 was correlated with late clinical stage and poorly differentiated carcinoma, and, low expression level of miR-145 could also predict chemotherapy resistance and shorter disease-free survival (DFS). These findings indicated that miR-145 expression may be a useful prognostic marker that could be used for predicting poor differentiation, chemo-resistance and shore DFS.

A Comprehensive Review of Dysregulated miRNAs Involved in Cervical Cancer

MicroRNAs(miRNAs) have become the center of interest in oncology. In recent years, various studies have demonstrated that miRNAs regulate gene expression by influencing important regulatory genes and thus are responsible for causing cervical cancer. Cervical cancer being the third most diagnosed cancer among the females worldwide, is the fourth leading cause of cancer related mortality. Prophylactic human papillomavirus (HPV) vaccines and new HPV screening tests, combined with traditional Pap test screening have greatly reduced cervical cancer. Yet, thousands of women continue to be diagnosed with and die of this preventable disease annually. This has necessitated the scientists to ponder over ways of evolving new methods and chalk out novel treatment protocols/strategies. As miRNA deregulation plays a key role in malignant transformation of cervical cancer along with its targets that can be exploited for both prognostic and therapeutic strategies, we have collected and reviewed the role of miRNA in cervical cancer. A systematic search was performed using PubMed for articles that report aberrant expression of miRNA in cervical cancer. The present review provides comprehensive information for 246 differentially expressed miRNAs gathered from 51 published articles that have been implicated in cervical cancer progression. Of these, more than 40 miRNAs have been reported in the literature in several instances signifying their role in the regulation of cancer. We also identified 40 experimentally validated targets, studied the cause of miRNAs dysregulation along with its mechanism and role in different stages of cervical cancer. We also identified and analysed miRNA clusters and their expression pattern in cervical cancer. This review is expected to further enhance our understanding in this field and serve as a valuable reference resource.

MiR-224 promotes the chemoresistance of human lung adenocarcinoma cells to cisplatin via regulating G₁/S transition and apoptosis by targeting p21(WAF1/CIP1)

BACKGROUND

Increasing evidence has shown that microRNAs (miRNAs) can serve as oncogenes and tumour suppressors to participate in tumour development. However, the roles of miRNAs in chemoresistance of human lung adenocarcinoma (LA) remain largely undefined.

METHODS

On the basis of miRNA microarray data, miR-224 was identified as the most upregulated miRNA in cisplatin (DDP; cis-diamminedichloroplatinum II)-resistant A549 cells compared with parental A549 cells. The aim of our study was to investigate the roles of miR-224 in the formation of DDP-resistant phenotype of LA cells and its possible molecular mechanisms.

RESULTS

Here we showed that miR-224 could promote the in vitro and in vivo DDP resistance of LA cells via regulating G1/S cell cycle transition and apoptosis. p21(WAF1/CIP1), a potent cyclin-dependent kinase inhibitor, was identified as the direct and functional target gene of miR-224. Overexpression of p21(WAF1/CIP1) could phenocopy the effect of miR-224 downregulation and silencing of p21(WAF1/CIP1) could partially reverse the effect of miR-224 downregulation on DDP resistance of DDP-resistant LA cells. In addition, miR-224 could affect the G1/S transition of cell cycle and apoptosis in LA cells through the p21(WAF1/CIP1)-pRb pathway and the intrinsic mitochondrial death pathway. Furthermore, miR-224 was found to be downregulated in DDP-responding LA tissues, and its expression was inversely correlated with p21(WAF1/CIP1). Multivariate analyses indicated that the status of miR-224 might be an independent prognostic factor for predicting the survival of LA patients.

CONCLUSIONS

Our findings shed novel light on the roles of miR-224/p21(WAF1/CIP1) signalling in the DDP resistance of LA cells, and targeting it will be a potential strategic approach for reversing the DDP resistance in human LAs.

The potential clinical applications and prospects of microRNAs in lung cancer

Lung cancer is the major cause of cancer deaths worldwide due to its late diagnosis and poor outcome. Understanding genomic medicine may widen our vision into the oncogenesis of lung cancer and may open the door to improvements in the clinical management of lung cancer. It is well known that almost half of all genes are regulated by microRNAs (miRNAs). This review focuses on the role of miRNAs in lung cancer and also touches on the value of miRNA-based novel therapies for lung cancers.

Drug resistance-related miRNAs in hepatocellular cancer

Hepatocellular cancer is a hypervascular cancer characterized by rapid progression as well as resistance to chemotherapy. Drug resistance arises from the alteration of many molecules, including oncogenes, tumor suppressor genes and miRNAs. This review evaluates the advances of drug resistance-related miRNAs in hepatocellular cancer, and analyzes the value of them as prognostic biomarkers and therapeutic targets. This review also discusses the limitations of miRNA-based therapy, and envisages future developments toward the clinical applications of drug resistance-related miRNAs.

MicroRNA Profile to Predict Gemcitabine Resistance in Bladder Carcinoma Cell Lines

MicroRNAs (miRNA) are small, noncoding RNAs with important regulatory roles in development, differentiation, cell proliferation, and death as well as the complex process of acquired drug resistance. The goal of this study was to identify specific miRNAs and their potential protein targets that confer acquired resistance to gemcitabine in urothelial carcinoma of the bladder (UCB) cell lines. Gemcitabine-resistant cells were established from 6 cell lines following exposure to escalating concentrations of the drug and by passaging cells in the presence of the drug over a 2- to 3-month period. Differential miRNA expression was identified in a microarray format comparing untreated controls with resistant cell lines, representing the maximum tolerated concentration, and results were validated via qRT-PCR. The involvement of specific miRNAs in chemoresistance was confirmed with transfection experiments, followed by clonogenic assays and Western blot analysis. Gemcitabine resistance was generated in 6 UCB cell lines. Microarray analysis comparing miRNA expression between gemcitabine-resistant and parental cells identified the differential expression of 66 miRNAs. Confirmation of differential expression was recorded via qRT-PCR in a subset of these miRNAs. Within this group, let-7b and let-7i exhibited decreased expression, while miR-1290 and miR-138 displayed increased expression levels in gemcitabine-resistant cells. Transfection of pre-miR-138 and pre-miR-1290 into parental cells attenuated cell death after exposure to gemcitabine, while transfection of pre-miR-let-7b and pre-miR-let-7i into the resistant cells augmented cell death. Mucin-4 was up-regulated in gemcitabine-resistant cells. Ectopic expression of let-7i and let-7b in the resistant cells resulted in the down-regulation of mucin-4. These results suggest a role for miRNAs 1290, 138, let-7i, and let-7b in imparting resistance to gemcitabine in UCB cell lines in part through the modulation of mucin-4. Alterations in these miRNAs and/or mucin-4 may constitute a potential therapeutic strategy for improving the efficacy of gemcitabine in UCB.

miR-375 is upregulated in acquired paclitaxel resistance in cervical cancer

Background:

Chemo-resistance is one of the key causal factors in cancer death and emerging evidences suggest that microRNAs (miRNAs) have critical roles in the regulation of chemo-sensitivity in cancers. Cervical cancer is one of the most common malignancies in women and insensitive to chemotherapy clinically.

Methods:

The differentially expressed miRNAs in cervical squamous cell carcinoma tissues were screened by using a microarray platform (μParaflo Sanger miRBase release 13.0). The expression of miR-375 was determined by stem-loop RT–PCR using 23 clinical cervical cancer samples and 2 cervical cancer cell lines. We exogenously upregulated miR-375 expression in SiHa and Caski cells using a pre-miRNA lentiviral vector transfection and observed its impact on paclitaxel sensitivity using MTS. The cells that stably overexpressed miR-375 were subcutaneously injected into mice to determine tumour growth and chemo-sensitivity in vivo.

Results:

Twenty-one differentially expressed miRNAs were found by miRNA microarray between pro- and post-paclitaxel cervical cancer tissues. Of those, miR-375 showed consistent high expression levels across paclitaxel-treated cervical cells and tissues. Paclitaxel induced upregulated miR-375 expression in a clear dose-dependent manner. Forced overexpression of miR-375 in cervical cancer cells decreased paclitaxel sensitivity in vitro and in vivo.

Conclusion:

Collectively, our results suggest that miR-375 might be a therapeutic target in paclitaxel-resistant cervical cancer.

Hedgehog signaling regulates drug sensitivity by targeting ABC transporters ABCB1 and ABCG2 in epithelial ovarian cancer

A major challenge of successful chemotherapy in ovarian cancer is overcoming intrinsic or acquired multi-drug resistance caused by active drug efflux mediated by ATP-binding cassette (ABC) transporters. Regulation of these transporters in ovarian cancer is poorly understood. We have found that abnormal expression of the hedgehog (Hh) signaling pathway transcription factor Gli1 is involved in the regulation of ABC transporters ABCB1 and ABCG2 in ovarian cancer. Hh is a known regulator of cancer cell proliferation and differentiation in several other types of invasive and metastatic malignancies. Our work has demonstrated that Gli1 is abnormally activated in a portion of ovarian cancers. Inhibition of Gli1 expression decreases ABCB1 and ABCG2 gene expression levels and enhances the response of ovarian cancer cells to certain chemotherapeutic drugs. The underlying mechanism is a direct association of Gli1 with a specific consensus sequence located in the promoter region of ABCB1 and ABCG2 genes. This study provides new understanding of ABC gene regulation by Hh signaling pathway, which may lead to the identification of new markers to detect and to anticipate ovarian cancer chemotherapy drug sensitivity.

Non-coding RNAs as theranostics in human cancers

Theranostics was coined originally as a term used to describe a system that combines diagnosis and therapy, aiming to provide the tools for personalized medicine. This review reasserts the grounds for regarding non-coding RNAs (ncRNA) as theranostics in human cancers. The microRNAs (miRNAs) are the most well studied ncRNAs in recent years; their pivotal role in orchestrating tumor initiation and progression has been confirmed in all types of cancers. Hence, these small ncRNAs have emerged as attractive therapeutic targets and diagnostic tool. Various approaches to use their therapeutic potential have been taken, here we summarize the most important ones. In the near future, the focus of theranostics will be shifted towards longer and mechanistically more versatile ncRNAs, and we included some recent advances supporting this view.

Increased expression of microRNA-21and its association with chemotherapeutic response in human colorectal cancer

The expression of microRNA-21 (miR-21) was determined in 42 patients with colorectal cancer (CRC) using real-time reverse transcription-polymerase chain reaction. The level of miR-21 in CRC tumour tissue was compared with paired normal adjacent tissue (NAT) and the relationships of miR-21 levels to clinicopathological characteristics and pathological tumour response to neoadjuvant chemotherapy were investigated. There was a significantly higher level of miR-21 in CRC tumour tissue than in NAT and high expression of miR-21 was significantly correlated with advanced clinical stage and poor cell differentiation. Receiver operating characteristic curve analysis indicated a maximum optimal cut-off cycle threshold value of 10.32 for differentiating pathological responders from non-responders, with a sensitivity of 80.0% and specificity of 88.2%. These data showed that miR-21 was significantly overexpressed in CRC tumour tissue and was associated with advanced CRC, and that miR-21 may be a potential candidate biomarker for predicting pathological tumour response to chemotherapy.

microRNAs as tumor inhibitors, oncogenes, biomarkers for drug efficacy and outcome predictors in lung cancer (review)

Lung cancer remains the leading cause of cancer-related death worldwide for both men and women, and non-small cell lung cancer (NSCLC) accounts for approximately 80% of all cases. Despite improvements in early diagnosis and newly developed therapies, the 5-year survival rate for NSCLC patients remains low (15%). Therapy in NSCLC has reached a plateau. Understanding genomic medicine may provide insight into the oncogenesis of lung cancer and open the door to molecular diagnosis, new biomarkers and a more accurate prognosis of lung cancer. It is well known that almost half of the genes regulated by microRNAs (miRNAs) are located in cancer-associated genomic regions. In the present study, we discuss the potential of miRNAs to function as suppressors and biomarkers for chemoresistance and prognosis of lung cancer.

The emerging important role of microRNAs in the pathogenesis, diagnosis and treatment of human cancers

MicroRNAs are small non-protein-coding RNAs which repress gene expression, through base pair matching with messenger RNA (mRNA). A single microRNA is capable of regulating hundreds of mRNA sequences. Only a small fraction of the over 1000 discovered microRNAs have currently known functions; many are crucial in the regulation of genetic signalling, including cellular processes such as cellular differentiation, growth, proliferation and death. Dysfunction in microRNA signalling is present in all cancers studied thus far, leading to overactive oncogenic and underactive tumour suppressor gene signalling. Current research is actively pursuing the potential to use microRNAs as diagnostic tools and novel therapies in a variety of diseases. This review summarises normal and abnormal maturation and function of microRNAs and their role in the pathogenesis of various human tumours and highlights how microRNAs may be used as diagnostic and treatment tools in human cancers in the future.

MicroRNA gene dosage alterations and drug response in lung cancer

Chemotherapy resistance is a key contributor to the dismal prognoses for lung cancer patients. While the majority of studies have focused on sequence mutations and expression changes in protein-coding genes, recent reports have suggested that microRNA (miRNA) expression changes also play an influential role in chemotherapy response. However, the role of genetic alterations at miRNA loci in the context of chemotherapy response has yet to be investigated. In this study, we demonstrate the application of an integrative, multidimensional approach in order to identify miRNAs that are associated with chemotherapeutic resistance and sensitivity utilizing publicly available drug response, miRNA loci copy number, miRNA expression, and mRNA expression data from independent resources. By instigating a logical stepwise strategy, we have identified specific miRNAs that are associated with resistance to several chemotherapeutic agents and provide a proof of principle demonstration of how these various databases may be exploited to derive relevant pharmacogenomic results.

Genome-wide analysis of microRNA and mRNA expression signatures in hydroxycamptothecin-resistant gastric cancer cells

AIM

To investigate the involvement of microRNAs (miRNAs) in intrinsic drug resistance to hydroxycamptothecin (HCPT) of six gastric cancer cell lines (BGC-823, SGC-7901, MGC-803, HGC-27, NCI-N87, and AGS).

METHODS

A sulforhodamine B (SRB) assay was used to analyze the sensitivity to HCPT of six gastric cancer cell lines. The miRNA and mRNA expression signatures in HCPT-resistant cell lines were then identified using DNA microarrays. Gene ontology and pathway analysis was conducted using GenMAPP2. A combined analysis was used to explore the relationship between the miRNAs and mRNAs.

RESULTS

The sensitivity to HCPT was significantly different among the six cell lines. In the HCPT-resistant gastric cancer cells, the levels of 25 miRNAs were deregulated, including miR-196a, miR-200 family, miR-338, miR-126, miR-31, miR-98, let-7g, and miR-7. Their target genes were related to cancer development, progression and chemosensitivity. Moreover, 307 genes were differentially expressed in HCPT-resistant cell lines, including apoptosis-related genes (BAX, TIAL1), cell division-related genes (MCM2), cell adhesion- or migration-related genes (TIMP2, VSNL1) and checkpoint genes (RAD1). The combined analysis revealed 78 relation pairs between the miRNAs and mRNAs.

CONCLUSION

Hierarchical clustering showed that the miRNA and mRNA signatures in our results were informative for discriminating cell lines with different sensitivities to HCPT. However, there was slightly lower correlation between the expression patterns of the miRNA and those of the predicted target transcripts.

MicroRNA regulation of core apoptosis pathways in cancer

Recent research has demonstrated that microRNAs (miRNAs) are key regulators of many cell processes often deregulated in cancer, including apoptosis. Indeed, it is becoming clear that many miRNAs are anti-apoptotic and mediate this effect by targeting pro-apoptotic mRNAs or positive regulators of pro-apoptotic mRNAs. Conversely, many pro-apoptotic miRNAs target anti-apoptotic mRNAs or their positive regulators. We have reviewed the current knowledge in this area including evidence of miRNA involvement in cancer drug resistance.

Resistance may not be futile: microRNA biomarkers for chemoresistance and potential therapeutics

Chemoresistance to many commercially available cancer therapeutic drugs is a common occurrence and contributes to cancer mortality as it often leads to disease progression. There have been a number of studies evaluating the mechanisms of resistance and the biological factors involved. microRNAs have recently been identified as playing a role in the regulation of key genes implicated as cancer therapeutic targets or in mechanisms of chemoresistance including EGFR, MDR1, PTEN, Bak1, and PDCD4 among others. This article briefly reviews chemoresistance mechanisms, discusses how microRNAs can play a role in those mechanisms, and summarizes current research involving microRNAs as both regulators of key target genes for chemoresistance and biomarkers for treatment response. It is clear from the accumulating literature that microRNAs can play an important role in chemoresistance and hold much promise for the development of targeted therapies and personalized medicine. This review brings together much of this new research as a starting point for identifying key areas of interest and potentials for future study.