A possible role for microRNA-141 down-regulation in sunitinib resistant metastatic clear cell renal cell carcinoma through induction of epithelial-to-mesenchymal transition and hypoxia resistance

Diagnostic, predictive and prognostic molecular biomarkers in clear cell renal cell carcinoma: A retrospective study

Clear cell renal cell carcinoma (ccRCC) is a common and aggressive subtype of kidney cancer. Many patients are diagnosed at advanced stages, making early detection crucial. Unfortunately, there are currently no noninvasive tests for ccRCC, emphasizing the need for new biomarkers. Additionally, ccRCC often develops resistance to treatments like radiotherapy and chemotherapy. Identifying biomarkers that predict treatment outcomes is vital for personalized care. The integration of artificial intelligence (AI), multi-omics analysis, and computational biology holds promise in bolstering detection precision and resilience, opening avenues for future investigations. The amalgamation of radiogenomics and biomaterial-basedimmunomodulation signifies a revolutionary breakthrough in diagnostic medicine. This review summarizes existing literature and highlights emerging biomarkers that enhance diagnostic, predictive, and prognostic capabilities for ccRCC, setting the stage for future clinical research.

Inhibiting stanniocalcin 2 reduces sunitinib resistance of Caki-1 renal cancer cells under hypoxia condition

Background

Our previous study has suggested that blocking stanniocalcin 2 (STC2) could reduce sunitinib resistance in clear cell renal cell carcinoma (ccRCC) under normoxia. The hypoxia is a particularly important environment for RCC occurrence and development, as well as sunitinib resistance. The authors proposed that STC2 also plays important roles in RCC sunitinib resistance under hypoxia conditions.

Methods

The ccRCC Caki-1 cells were treated within the hypoxia conditions. Real-time quantitative PCR and Western blotting were applied to detect the STC2 expression in ccRCC Caki-1 cells. STC2-neutralizing antibodies, STC2 siRNA, and the recombinant human STC2 (rhSTC2) were used to identify targeting regulation on STC2 in modulating sunitinib resistance, proliferation, epithelial-mesenchymal transition (EMT), migration, and invasion. In addition, autophagy flux and the lysosomal acidic environment were investigated by Western blotting and fluorescence staining, and the accumulation of sunitinib in cells was observed with the addition of STC2-neutralizing antibodies and autophagy modulators.

Results

Under hypoxia conditions, sunitinib disrupted the lysosomal acidic environment and accumulated in Caki-1 cells. Hypoxia-induced the STC2 mRNA and protein levels in Caki-1 cells. STC2-neutralizing antibodies and STC2 siRNA effectively aggravated sunitinib-reduced cell viability and proliferation, which were reversed by rhSTC2. In addition, sunitinib promoted EMT, migration, and invasion, which were reduced by STC2-neutralizing antibodies.

Conclusion

Inhibiting STC2 could reduce the sunitinib resistance of ccRCC cells under hypoxia conditions.

miRNAs as potential game-changers in renal cell carcinoma: Future clinical and medicinal uses

Renal cell carcinoma (RCC) has the highest mortality rate of all genitourinary cancers, and its prevalence has grown over time. While RCC can be surgically treated and recurrence is only probable in a tiny proportion of patients, early diagnosis is crucial. Mutations in a large number of oncogenes and tumor suppressor genes contribute to pathway dysregulation in RCC. MicroRNAs (miRNAs) have considerable promise as biomarkers for detecting cancer due to their special combination of properties. Several miRNAs have been proposed as a diagnostic or monitoring tool for RCC based on their presence in the blood or urine. Moreover, the expression profile of particular miRNAs has been associated with the response to chemotherapy, immunotherapy, or targeted therapeutic options like sunitinib. The goal of this review is to go over the development, spread, and evolution of RCC. Also, we emphasize the outcomes of studies that examined the use of miRNAs in RCC patients as biomarkers, therapeutic targets, or modulators of responsiveness to treatment modalities.

Advances in Renal Cell Carcinoma Drug Resistance Models

Renal cell carcinoma (RCC) is the most common form of kidney cancer. Systemic therapy is the preferred method to eliminate residual cancer cells after surgery and prolong the survival of patients with inoperable RCC. A variety of molecular targeted and immunological therapies have been developed to improve the survival rate and prognosis of RCC patients based on their chemotherapy-resistant properties. However, owing to tumor heterogeneity and drug resistance, targeted and immunological therapies lack complete and durable anti-tumor responses; therefore, understanding the mechanisms of systemic therapy resistance and improving clinical curative effects in the treatment of RCC remain challenging. In vitro models with traditional RCC cell lines or primary cell culture, as well as in vivo models with cell or patient-derived xenografts, are used to explore the drug resistance mechanisms of RCC and screen new targeted therapeutic drugs. Here, we review the established methods and applications of in vivo and in vitro RCC drug resistance models, with the aim of improving our understanding of its resistance mechanisms, increasing the efficacy of combination medications, and providing a theoretical foundation for the development and application of new drugs, drug screening, and treatment guidelines for RCC patients.

miR-96-5p targets PTEN to mediate sunitinib resistance in clear cell renal cell carcinoma

A multiple receptor tyrosine kinase inhibitor, sunitinib, is a first-line therapy for clear cell renal cell carcinoma (CCRCC). Unfortunately, it has the major challenges of low initial response rate and resistance after about one year of treatment. Here we evaluated a microRNA (miRNA) and its target responsible for sunitinib resistance. Using miRNA profiling, we identified miR-96-5p upregulation in tumors from sunitinib-resistant CCRCC patients. By bioinformatic analysis, PTEN was selected as a potential target of miR-96-5p, which showed low levels in tumors from sunitinib-resistant CCRCC patients. Furthermore, PTEN and miR-96-5p levels were negatively correlated in a large The Cancer Genome Atlas kidney renal clear cell carcinoma cohort and high miR-96 and low PTEN represented poor prognosis in this cohort. Additionally, four-week sunitinib treatment increased miR-96-5p and decreased PTEN only in tumors from a sunitinib-resistant patient-derived xenograft model. We found a novel miR-96-5p binding site in the PTEN 3′ UTR and confirmed direct repression by luciferase reporter assay. Furthermore, we demonstrated that repression of PTEN by miR-96-5p increased cell proliferation and migration in sunitinib-treated cell lines. These results highlight the direct suppression of PTEN by miR-96-5p and that high miR-96-5p and low PTEN are partially responsible for sunitinib resistance and poor prognosis in CCRCC.

Integrated mRNA and miRNA Transcriptomic Analyses Reveals Divergent Mechanisms of Sunitinib Resistance in Clear Cell Renal Cell Carcinoma (ccRCC)

Simple Summary

Clear cell renal cell carcinoma (ccRCC) is a frequent cancer that causes more than 100,000 deaths every year. Treatment with drugs that target enzymes that help tumours grow such as sunitinib have greatly improved the prospects for ccRCC patients, however a large proportion of patients become resistant. We created sunitinib resistant cell lines and identified consequent changes in gene (and miRNA) expression by microarray analyses. Using this approach, we identified different pathways of resistance suggesting that tumour cells have many ways to overcome sunitinib treatment. We were able to overcome resistance in cells by inhibiting a protein, PD-L1, that is targeted by many immunotherapeutics currently in use for ccRCC patients suggesting a combination of immunotherapy and sunitinib may benefit patients. In addition, we identified miRNAs that are common to multiple resistance mechanisms suggesting they may be useful targets for future studies.

Abstract

The anti-angiogenic therapy sunitinib remains the standard first-line treatment for meta static clear cell renal cell carcinoma (ccRCC). However, acquired resistance develops in nearly all responsive patients and represents a major source of treatment failure. We used an integrated miRNA and mRNA transcriptomic approach to identify miRNA:target gene interactions involved in sunitinib resistance. Through the generation of stably resistant clones in three ccRCC cell lines (786-O, A498 and Caki-1), we identified non-overlapping miRNA:target gene networks, suggesting divergent mechanisms of sunitinib resistance. Surprisingly, even though the genes involved in these networks were different, they shared targeting by multiple members of the miR-17~92 cluster. In 786-O cells, targeted genes were related to hypoxia/angiogenic pathways, whereas, in Caki-1 cells, they were related to inflammatory/proliferation pathways. The immunotherapy target PD-L1 was consistently up-regulated in resistant cells, and we demonstrated that the silencing of this gene resulted in an increase in sensitivity to sunitinib treatment only in 786-O-resistant cells, suggesting that some ccRCC patients might benefit from combination therapy with PD-L1 checkpoint inhibitors. In summary, we demonstrate that, although there are clearly divergent mechanisms of sunitinib resistance in ccRCC subtypes, the commonality of miRNAs in multiple pathways could be targeted to overcome sunitinib resistance.

Determination of the key ccRCC-related molecules from monolayer network to three-layer network

Clear cell renal cell carcinoma (ccRCC), with an increasing incidence rate, is one of the ubiquitous cancers. Its pathogenic factors are complicated and the molecular mechanism is not clear. It is essential to analyze the potential key genes related to ccRCC carcinogenesis. In this study, the differentially expressed mRNAs, miRNAs and lncRNAs (DEmRNAs, DEmiRNAs and DElncRNAs) of ccRCC were screened from TCGA database. Then the miRNA-mRNA network, lncRNA-miRNA network and lncRNA-mRNA network were constructed by online database or WGCNA algorithm. Topology attributes of these monolayer networks showed that hsa-mir-155, hsa-mir-200c, hsa-mir-122, hsa-mir-506, hsa-mir-216b, hsa-mir-141, lncRNA AC137723.1 and AC021074.3 are the crucial genes related with the regulatory effects on the proliferation, metastasis and invasion of ccRCC cells. Subsequently, these three monolayer networks were integrated into a lncRNA-miRNA-mRNA multilayer network. Considering node degree, closeness centrality and betweenness centrality, we found hsa-mir-122 is screened out as the only crucial gene in three-layer network. In order to better illustrate the effect of hsa-mir-122 on ccRCC, the lncRNA-hsa-mir-122-mRNA network was constructed with hsa-mir-122 as the center. Pathway analysis of the unique target gene GALNT3 linked to hsa-mir-122 showed that GALNT3 influenced the metabolic process of mucin type O-Glycan biosynthesis. LncRNA AC090377.1 is the unique gene that has target genes among lncRNAs with clinical significance that linked to hsa-mir-122 in the lncRNA-hsa-mir-122-mRNA network. Pathway analysis of AC090377.1 suggested that GUCY2F enriched in phototransduction pathway associated with retina. From monolayer network to three-layer network, hsa-mir-122 is identified as an important molecule in the oncogenesis and progression of ccRCC, offering new strategies to further study of the carcinogenic mechanism of ccRCC.

Epigenetic Alterations in Renal Cell Cancer With TKIs Resistance: From Mechanisms to Clinical Applications

The appearance of tyrosine kinase inhibitors (TKIs) has been a major breakthrough in renal cell carcinoma (RCC) therapy. Unfortunately, a portion of patients with TKIs resistance experience disease progression after TKIs therapy. Epigenetic alterations play an important role in the development of TKIs resistance. Current evidence suggests that epigenetic alterations occur frequently in RCC patients with poor response to TKIs therapy, and modulation of them could enhance the cytotoxic effect of antitumor therapy. In this review, we summarize the currently known epigenetic alterations relating to TKIs resistance in RCC, focusing on DNA methylation, non-coding RNAs (ncRNAs), histone modifications, and their interactions with TKIs treatment. In addition, we discuss application of epigenetic alteration analyses in the clinical setting to predict prognosis of patients with TKIs treatment, and the potential use of epigenetics-based therapies to surmount TKIs resistance.

The emerging role of small non-coding RNA in renal cell carcinoma

•

SncRNAs contribute to the progress of renal cell carcinoma.

•

SncRNAs are promising biomarkers for diagnosis and prognosis of renal cell carcinoma.

•

Despite the potential of sncRNA-based cancer therapy, some obstacles remain, including several severe adverse effect.

Noncoding RNAs are transcribed in the most regions of the human genome, divided into small noncoding RNAs (less than 200 nt) and long noncoding RNAs (more than 200 nt) according to their size. Compelling evidences suggest that small noncoding RNAs play critical roles in tumorigenesis and tumor progression, especially in renal cell carcinoma. MiRNA, the most famous small noncoding RNA, has been comprehensively explored for its fundamental role in cancer. And several miRNA-based therapeutic strategies have been applied to several ongoing clinical trials. However, piRNAs and tsRNAs, have not received as much research attention, because of several technological limitations. Nevertheless, some studies have revealed the presence of aberration of piRNAs and tsRNAs in renal cell carcinoma, highlighting a potentially novel mechanism for tumor onset and progression. In this review, we provide an overview of three classes of small noncoding RNA: miRNAs, piRNAs and tsRNAs, that have been reported dysregulation in renal cell carcinoma and have the potential for advancing diagnosis, prognosis and therapeutic applications of this disease.

MicroRNA Signature in Renal Cell Carcinoma

Renal cell carcinoma (RCC) includes 2.2% of all diagnosed cancers and 1.8% of cancer-related mortalities. The available biomarkers or screening methods for RCC suffer from lack of sensitivity or high cost, necessitating identification of novel biomarkers that facilitate early diagnosis of this cancer especially in the susceptible individuals. MicroRNAs (miRNAs) have several advantageous properties that potentiate them as biomarkers for cancer detection. Expression profile of miRNAs has been assessed in biological samples from RCC patients. Circulatory or urinary levels of certain miRNAs have been proposed as markers for RCC diagnosis or follow-up. Moreover, expression profile of some miRNAs has been correlated with response to chemotherapy, immunotherapy or targeted therapeutic options such as sunitinib. In the current study, we summarize the results of studies that assessed the application of miRNAs as biomarkers, therapeutic targets or modulators of response to treatment modalities in RCC patients.

Renal Cell Tumors: Uncovering the Biomarker Potential of ncRNAs

Renal cell tumors (RCT) remain as one of the most common and lethal urological tumors worldwide. Discrimination between (1) benign and malignant disease, (2) indolent and aggressive tumors, and (3) patient responsiveness to a specific therapy is of major clinical importance, allowing for a more efficient patient management. Nonetheless, currently available tools provide limited information and novel strategies are needed. Over the years, a putative role of non-coding RNAs (ncRNAs) as disease biomarkers has gained relevance and is now one of the most prolific fields in biological sciences. Herein, we extensively sought the most significant reports on ncRNAs as potential RCTs' diagnostic, prognostic, predictive, and monitoring biomarkers. We could conclude that ncRNAs, either alone or in combination with currently used clinical and pathological parameters, might represent key elements to improve patient management, potentiating the implementation of precision medicine. Nevertheless, most ncRNA biomarkers require large-scale validation studies, prior to clinical implementation.

Lentiviral-Mediated Overexpression of MicroRNA-141 Promotes Cell Proliferation and Inhibits Apoptosis in Human Esophageal Squamous Cell Carcinoma

BACKGROUND

Esophageal Carcinoma (EC) is the eighth most common cancer worldwide. Numerous studies have highlighted a vital role of microRNAs (miRNAs) in the development of EC. However, the mechanism of microRNA (miRNA)-141 in Esophageal Squamous Cell Carcinoma (ESCC) remains unknown.

OBJECTIVE

In this study, we explored the effects of miRNA-141 on EC cell proliferation, apoptosis, xenograft tumour growth and their possible mechanisms.

METHODS

A lentivirus-vector-expressing miRNA-141 was constructed, and a TE-1 cell line of ESCC with a stable expression of miRNA-141 was transfected and screened. The miRNA-141 expression level was detected using qRT-PCR. Effects of miRNA-141 overexpression on cell proliferation and apoptosis were detected using MTT and flow cytometry, respectively. Using a dual-luciferase reporter assay, a direct interaction between miRNA-141 and the 3'-Untranslated Region (UTR) of YAP1 and SOX17 was confirmed. Tumour xenograft experiment in nude mice was used to detect the tumour growth, and the effects of miRNA-141 overexpression on YAP1 and SOX17 were analysed using Western blot.

RESULTS

We found that miRNA-141 was highly expressed in TE-1 cells, and miRNA-141 overexpression promoted cell proliferation and inhibited apoptosis. Moreover, the miRNA-141 group showed significantly increased tumour growth ability, luciferase activities and expression levels of YAP1 and SOX17 in the miRNA-141group were significantly down-regulated.

CONCLUSION

miRNA-141 promotes cell proliferation and inhibits apoptosis in ESCC by downregulating the expression level of YAP1 and SOX17, indicating that miRNA-141 may be a potential molecular target for the treatment of ESCC.

MiR-376b-3p Is Associated With Long-term Response to Sunitinib in Metastatic Renal Cell Carcinoma Patients

BACKGROUND/AIM

Sunitinib is a tyrosine kinase inhibitor routinely used as first-line therapy in metastatic renal cell carcinoma (mRCC). Emerging evidence suggests that microRNAs (miRNAs) could be suitable biomarkers with predictive potential in mRCC. The aim of this study was to identify miRNA-based predictive biomarkers of therapy response to avoid unnecessary therapy to non-responding patients.

PATIENTS AND METHODS

High-throughput miRNA microarray profiling was performed on a cohort of 47 patients treated with sunitinib. Validation of candidate miRNAs was carried out on an independent cohort of 132 mRCC patients using qRT-PCR.

RESULTS

Out of 158 miRNAs (65 down-regulated, 93 up-regulated), six miRNAs were chosen for independent validation and miR-376b-3p was confirmed to be differentially expressed in tumors of patients with primary resistance versus long-term response (p<0.0002).

CONCLUSION

A predictive miRNA associated with progression-free survival in metastatic renal cell carcinoma patients treated with sunitinib was identified.

Biomarkers of Prognosis and Efficacy of Anti-angiogenic Therapy in Metastatic Clear Cell Renal Cancer

In the last decades, the prognosis of metastatic renal cell carcinoma (mRCC) has remarkably improved following the advent of the "targeted therapy" era. The expanding knowledge on the prominent role played by angiogenesis in RCC pathogenesis has led to approval of multiple anti-angiogenic agents such as sunitinib, pazopanib, axitinib, cabozantinib, sorafenib, and bevacizumab. These agents can induce radiological responses and delay cancer progression for months or years before onset of resistance, with a clinically meaningful activity. The need for markers of prognosis and efficacy of anti-angiogenic agents has become more compelling as novel systemic immunotherapy agents have also been approved in RCC and can be administered as an alternative to angiogenesis inhibitors. Anti PD-1 monoclonal antibody nivolumab has been approved in the second-line setting after tyrosine kinase inhibitors failure, while combination of nivolumab plus anti CTLA-4 monoclonal antibody ipilimumab has been approved as first-line therapy of RCC patients at intermediate or poor prognosis. In this review article, biomarkers of prognosis and efficacy of antiangiogenic therapies are summarized with a focus on those that have the potential to affect treatment decision-making in RCC. Biomarkers predictive of toxicity of anti-angiogenic agents have also been discussed.

miR-130b Promotes Sunitinib Resistance through Regulation of PTEN in Renal Cell Carcinoma

BACKGROUND

MicroRNAs are a class of small noncoding RNAs that play an important role in progression and drug resistance in cancer. Several reports have shown that miR-130b modulates cell growth and drug resistance in some cancers. However, the expression and biological role of miR-130b in renal cell carcinoma (RCC) remain poorly understood. This study aimed to examine the expression and functional role of miR-130b and to analyze the association between miR-130b and sunitinib resistance in RCC.

METHODS

The expression of miR-130b in 32 RCC tissues and their corresponding normal kidney tissues was determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR). We performed a 4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay in RCC cell lines transfected with miR-130b inhibitor or miR-130b mimics. We evaluated the relationship between miR-130b and PTEN and also analyzed the effect of miR-130b on sunitinib resistance.

RESULTS

qRT-PCR analysis showed that the expression of miR-130b was higher in RCC tissues than in corresponding normal kidney tissues. The MTT assay revealed that miR-130b modulated cell growth. qRT-PCR revealed an inverse correlation between miR-130b and PTEN in RCC. Western blotting demonstrated that miR-130b regulated the expression of PTEN in the RCC cell line. Additionally, miR-130b was associated with sunitinib resistance through regulation of PTEN. We established the sunitinib-resistant Caki-1 (Caki-1-SR) cells and observed that the expression of miR-130b was elevated in Caki-1-SR cells compared with parental Caki-1 cells. Knockdown of miR-130b improved sunitinib resistance in Caki-1-SR cells.

CONCLUSION

The expression of miR-130b was upregulated in RCC. miR-130b promoted cell growth and was associated with sunitinib resistance through regulating PTEN expression. Collectively, these results suggest that miR-130b may play an oncogenic role and be a promising therapeutic target.

Molecular Mechanisms in Clear Cell Renal Cell Carcinoma: Role of miRNAs and Hypermethylated miRNA Genes in Crucial Oncogenic Pathways and Processes

Clear cell renal cell carcinoma (ccRCC) is the third most common urological cancer, and it has the highest mortality rate. The increasing drug resistance of metastatic ccRCC has resulted in the search for new biomarkers. Epigenetic regulatory mechanisms, such as genome-wide DNA methylation and inhibition of protein translation by interaction of microRNA (miRNA) with its target messenger RNA (mRNA), are deeply involved in the pathogenesis of human cancers, including ccRCC, and may be used in its diagnosis and prognosis. Here, we review oncogenic and oncosuppressive miRNAs, their putative target genes, and the crucial pathways they are involved in. The contradictory behavior of a number of miRNAs, such as suppressive and anti-metastatic miRNAs with oncogenic potential (for example, miR-99a, miR-106a, miR-125b, miR-144, miR-203, miR-378), is examined. miRNAs that contribute mostly to important pathways and processes in ccRCC, for instance, PI3K/AKT/mTOR, Wnt-β, histone modification, and chromatin remodeling, are discussed in detail. We also separately consider their participation in crucial oncogenic processes, such as hypoxia and angiogenesis, metastasis, and epithelial-mesenchymal transition (EMT). The review also considers the interactions of long non-coding RNAs (lncRNAs) and miRNAs of significance in ccRCC. Recent advances in the understanding of the role of hypermethylated miRNA genes in ccRCC and their usefulness as biomarkers are reviewed based on our own data and those available in the literature. Finally, new data and perspectives concerning the clinical applications of miRNAs in the diagnosis, prognosis, and treatment of ccRCC are discussed.

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-9-5p in Nephrectomy Specimens is a Potential Predictor of Primary Resistance to First-Line Treatment with Tyrosine Kinase Inhibitors in Patients with Metastatic Renal Cell Carcinoma

Approximately 20–30% of patients with metastatic renal cell carcinoma (mRCC) in first-line treatment with tyrosine kinase inhibitors (TKIs) do not respond due to primary resistance to this drug. At present, suitable robust biomarkers for prediction of a response are not available. Therefore, the aim of this study was to evaluate a panel of microRNAs (miRNAs) in nephrectomy specimens for use as predictive biomarkers for TKI resistance. Archived formalin-fixed, paraffin embedded nephrectomy samples from 60 mRCC patients treated with first-line TKIs (sunitinib, n = 51; pazopanib, n = 6; sorafenib, n = 3) were categorized into responders and non-responders. Using the standard Response Evaluation Criteria in Solid Tumors, patients with progressive disease within 3 months after the start of treatment with TKI were considered as non-responders and those patients with stable disease and complete or partial response under the TKI treatment for at least 6 months as responders. Based on a miRNA microarray expression profile in the two stratified groups of patients, seven differentially expressed miRNAs were validated using droplet digital reverse-transcription quantitative real-time polymerase chain reaction (RT-qPCR) assays in the two groups. Receiver operating characteristic curve analysis and binary logistic regression of response prediction were performed. MiR-9-5p and miR-489-3p were able to discriminate between the two groups. MiR-9-5p, as the most significant miRNA, improved the correct prediction of primary resistance against TKIs in comparison to that of conventional clinicopathological variables. The results of the decision curve analyses, Kaplan-Meier analyses and Cox regression analyses confirmed the potential of miR-9-5p in the prediction of response to TKIs and the prediction of progression-free survival after the initiation of TKI treatment.

Sunitinib induces early histomolecular changes in a subset of renal cancer cells that contribute to resistance

Sunitinib is the standard-of-care, first-line treatment for advanced renal cell carcinoma (RCC). Characteristics of treatment-resistant RCC have been described; however, complex tumor adaptation mechanisms obstruct the identification of significant operators in resistance. We hypothesized that resistance is a late manifestation of early, treatment-induced histomolecular alterations; therefore, studying early drug response may identify drivers of resistance. We describe an epithelioid RCC growth pattern in RCC xenografts, which emerges in sunitinib-sensitive tumors and is augmented during resistance. This growth modality is molecularly and morphologically related to the RCC spheroids that advance during in vitro treatment. Based on time-lapse microscopy, mRNA and microRNA screening, and tumor behavior-related characteristics, we propose that the spheroid and adherent RCC growth patterns differentially respond to sunitinib. Gene expression analysis indicated that sunitinib promoted spheroid formation, which provided a selective survival advantage under treatment. Functional studies confirm that E-cadherin is a key contributor to the survival of RCC cells under sunitinib treatment. In summary, we suggest that sunitinib-resistant RCC cells exist in treatment-sensitive tumors and are histologically identifiable.-Lichner, Z., Saleeb, R., Butz, H., Ding, Q., Nofech-Mozes, R., Riad, S., Farag, M., Varkouhi, A. K., dos Santos, C. C., Kapus, A., Yousef, G. M. Sunitinib induces early histomolecular changes in a subset of renal cancer cells that contribute to resistance.

MicroRNAs as Mediators of Resistance Mechanisms to Small-Molecule Tyrosine Kinase Inhibitors in Solid Tumours

Receptor tyrosine kinases (RTKs) are widely expressed transmembrane proteins that act as receptors for growth factors and other extracellular signalling molecules. Upon ligand binding, RTKs activate intracellular signalling cascades, and as such are involved in a broad variety of cellular functions including differentiation, proliferation, migration, invasion, angiogenesis, and survival under physiological as well as pathological conditions. Aberrant RTK activation can lead to benign proliferative conditions as well as to various forms of cancer. Indeed, more than 70% of the known oncogene and proto-oncogene transcripts involved in cancer code for RTKs. Consequently, these receptors are broadly studied as targets in the treatment of different tumours, and a large variety of small-molecule tyrosine kinase inhibitors (TKIs) are approved for therapy. In most cases, patients develop resistance to the TKIs within a short time. MicroRNAs are short (18-22 nucleotides) non-protein-coding RNAs that fine-tune cell homeostasis by controlling gene expression at the post-transcriptional level. Deregulation of microRNAs is common in many cancers, and increasing evidence exists for an important role of microRNAs in the development of resistance to therapies, including TKIs. In this review we focus on the role of microRNAs in mediating resistance to small-molecule TKIs in solid tumours.

Potential clinical applications of microRNAs as biomarkers for renal cell carcinoma

Introduction

Renal cell carcinoma (RCC) accounts for 3% of adult malignancies and more than 90% of kidney neoplasms. High rates of undiagnostic percutaneous kidney biopsies and difficulties in reliable pre-operative differentiation between malignant and benign renal tumors using contemporary imaging techniques result in large numbers of redundant surgeries. Absence of specific biomarkers for early detection and monitoring complicates on-time diagnosis of the disease and relapse. For the patients followed up after having a nephrectomy, a noninvasive and sensitive biomarker enabling early detection of disease relapse would be extremely useful.

Material and methods

The study is a review of recent knowledge regarding potential clinical applications of microRNAs (miRNAs) as biomarkers of RCC.

Results

MicroRNAs are essential regulators of various processes such as cell proliferation, differentiation, development and death; they have been implicated in diverse biological and pathological processes in RCC. There is a class of miRNAs that promote RCC development (oncomirs) and a class of miRNAs that negatively regulate oncogenes, suppress tumor growth and invasion, and thus could be considered treatment agents (anti-oncomirs). Separate miRNAs and specific miRNAs expression profiles have been identified, enabling early detection of the disease, prediction of response to systemic therapy, or prognostication of biological behavior of the disease.

Conclusions

The miRNA network analysis and gene profiling may help to identify the most sensible molecular signatures of RCC that can be used for diagnostic purposes, as well as poor prognosis signatures and poor therapeutic response signatures in patients who undergo systemic therapy.

MicroRNAs as predictive biomarkers of response to tyrosine kinase inhibitor therapy in metastatic renal cell carcinoma

Renal cell carcinoma (RCC) accounts for 2%–3% of all malignant tumours. The first-choice treatment in metastatic RCC (mRCC) patients is tyrosine kinase inhibitors (TKIs). Although TKIs may prolong survival of the treated patients who are not primary resistant, almost all of them will eventually develop secondary resistance to the treatment after a progression-free period. To predict treatment response, thus, we need efficient biomarkers for rational indication of TKIs in mRCC. MicroRNAs (miRNAs) not only play important roles in the pathogenesis of many cancers, including RCC but also have been shown to serve as promising diagnostic, prognostic and predictive biomarkers in various cancers. However, the potential of miRNAs to predict response to therapy with TKIs in mRCC has not yet gained sufficient attention. Because personalisation of the TKIs indication in mRCC presents an important unmet medical need, we summarise research on this topic and give an overall insight on the current knowledge in this field.

The biological roles and clinical implications of microRNAs in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) accounts for about 3% of tumors in adults as well as 85% of all primary renal carcinoma. And it is the third most predominant urological carcinoma, but it has the maximum mortality rate. Early diagnosis and proper follow-up of ccRCC patients may improve the prognosis of the illness. Thus, it is imperative to understand the new biomarkers of ccRCC and study new method for the modern therapy of this deadly disease. Furthermore, a large number of microRNAs (miRNAs), small non-coding RNAs, have been relevant to tumor type, stage, or survival and miRNAs might be progressed as the markers of diagnosis or prognosis in ccRCC. A growing body of data also advised the rationality of regarding miRNAs as therapeutic targets for ccRCC treatment. In this review, we tried to summarize biogenesis of miRNAs and their expression profiles, biological roles, and clinical implications in ccRCC.

Lysosome-associated membrane protein 2 (LAMP-2) expression induced by miR-194-5p downregulation contributes to sunitinib resistance in human renal cell carcinoma cells

Sunitinib is a tyrosine kinase inhibitor that is used as the primary treatment in metastatic renal cell carcinoma (RCC). The main difficulty associated with its use is the development of drug resistance. In the present study, ACHN cells, a human renal cell carcinoma cell line, were used to establish sunitinib-resistant (SR) cells. Microarray analysis and reverse transcription-quantitative polymerase chain reaction revealed that miR-194-5p expression was significantly decreased in SR-ACHN cells when compared with that observed in ACHN cells (P<0.05). Transfection of miR-194-5p, though not with negative control miR, in SR-ACHN cells could significantly inhibit cell proliferation following sunitinib treatment (2.5–40 µM; P<0.05). Western blotting demonstrated that the expression of lysosome-associated membrane protein-2 (LAMP-2), which attenuates the anti-proliferative effect of sunitinib, was significantly higher in SR-ACHN than in ACHN cells (P<0.01). In addition, LAMP-2 expression was suppressed by miR-194-5p transfection in SR-ACHN cells. These data suggested that miR-194-5p downregulation may be associated with sunitinib resistance via the induction of LAMP-2 expression in human RCC.

Novel potential predictive markers of sunitinib outcomes in long-term responders versus primary refractory patients with metastatic clear-cell renal cell carcinoma

BACKGROUND

Several potential predictive markers of efficacy of targeted agents in patients with metastatic renal cell carcinoma (mRCC) have been identified. Interindividual heterogeneity warrants further investigation.

PATIENTS AND METHODS

Multicenter, observational, retrospective study in patients with clear-cell mRCC treated with sunitinib. Patients were classified in two groups: long-term responders (LR) (progression-free survival (PFS)≥22 months and at least stable disease), and primary refractory (PR) (progressive disease within 3-months of sunitinib onset). Objectives were to compare baseline clinical factors in both populations and to correlate tumor expression of selected signaling pathways components with sunitinib PFS.

RESULTS

123 patients were analyzed (97 LR, 26 PR). In the LR cohort, overall response rate was 79% and median duration of best response was 30 months. Median PFS and overall survival were 43.2 (95% confidence intervals[CI]:37.2-49.3) and 63.5 months (95%CI:55.1-71.9), respectively. At baseline PR patients had a significantly lower proportion of nephrectomies, higher lactate dehydrogenase and platelets levels, lower hemoglobin, shorter time to and higher presence of metastases, and increased Fuhrman grade. Higher levels of HEYL, HEY and HES1 were observed in LR, although only HEYL discriminated populations significantly (AUC[ROC]=0.704; cut-off=34.85). Increased levels of hsa-miR-27b, hsa-miR-23b and hsa-miR-628-5p were also associated with prolonged survival. No statistical significant associations between hsa-miR-23b or hsa-miR-27b and the expression of c-Met were found.

CONCLUSIONS

Certain mRCC patients treated with sunitinib achieve extremely long-term responses. Favorable baseline hematology values and longer time to metastasis may predict longer PFS. HEYL, hsa-miR-27b, hsa-miR-23b and hsa-miR-628-5p could be potentially used as biomarkers of sunitinib response.

miRNAs: micro-managers of anticancer combination therapies

Angiogenesis is one of the hallmarks of cancer progression and as such has been considered a target of therapeutic interest. However, single targeted agents have not fully lived up to the initial promise of anti-angiogenic therapy. Therefore, it has been suggested that combining therapies and agents will be the way forward in the oncology field. In recent years, microRNAs (miRNAs) have received considerable attention as drivers of tumor development and progression, either acting as tumor suppressors or as oncogenes (so-called oncomiRs), as well as in the process of tumor angiogenesis (angiomiRs). Not only from a functional, but also from a therapeutic view, miRNAs are attractive tools. Thus far, several mimics and antagonists of miRNAs have entered clinical development. Here, we review the provenance and promise of miRNAs as targets as well as therapeutics to contribute to anti-angiogenesis-based (combination) treatment of cancer.

Deep sequencing reveals microRNAs predictive of antiangiogenic drug response

The majority of metastatic renal cell carcinoma (RCC) patients are treated with tyrosine kinase inhibitors (TKI) in first-line treatment; however, a fraction are refractory to these antiangiogenic drugs. MicroRNAs (miRNAs) are regulatory molecules proven to be accurate biomarkers in cancer. Here, we identified miRNAs predictive of progressive disease under TKI treatment through deep sequencing of 74 metastatic clear cell RCC cases uniformly treated with these drugs. Twenty-nine miRNAs were differentially expressed in the tumors of patients who progressed under TKI therapy (P values from 6 × 10^-9 to 3 × 10^-3). Among 6 miRNAs selected for validation in an independent series, the most relevant associations corresponded to miR-1307-3p, miR-155-5p, and miR-221-3p (P = 4.6 × 10^-3, 6.5 × 10^-3, and 3.4 × 10^-2, respectively). Furthermore, a 2 miRNA-based classifier discriminated individuals with progressive disease upon TKI treatment (AUC = 0.75, 95% CI, 0.64-0.85; P = 1.3 × 10^-4) with better predictive value than clinicopathological risk factors commonly used. We also identified miRNAs significantly associated with progression-free survival and overall survival (P = 6.8 × 10^-8 and 7.8 × 10^-7 for top hits, respectively), and 7 overlapped with early progressive disease. In conclusion, this is the first miRNome comprehensive study, to our knowledge, that demonstrates a predictive value of miRNAs for TKI response and provides a new set of relevant markers that can help rationalize metastatic RCC treatment.

MicroRNAs in the Pathogenesis of Renal Cell Carcinoma and Their Diagnostic and Prognostic Utility as Cancer Biomarkers

Purpose

To provide information about the role of microRNAs in the pathogenesis of renal cell carcinoma (RCC) and their diagnostic and prognostic utility as cancer biomarkers.

Methods

A literature search was performed in the PubMed and Web of Science databases using the keywords “renal cancer/renal cell carcinoma/kidney cancer” and “miR*/miRNA*/microRNA*”. Articles dealing with the role of miRNAs in the pathogenesis of RCC, diagnostic miRNAs and prognostic miRNAs were separated.

Results

MiRNAs act both as oncogenes and tumor suppressors. They regulate apoptosis, cell growth, migration, invasion, proliferation, colony formation and angiogenesis through target proteins involved in several signaling pathways, and they are involved in key pathogenetic mechanisms such as hypoxia (HIF/VHL dependent) and epithelial-to-mesenchymal transition. Differentially expressed miRNAs can discriminate either tumor tissue from healthy renal tissue or different RCC subtypes. Circulating miRNAs are promissing as diagnostic biomarkers of RCC. Information about urinary miRNAs associated with RCC is sparse. Detection of a relapse is another implication of diagnostic miRNAs. The expression profiles of several miRNAs correlate with the prognosis of RCC patients. Comparison between primary tumor tissue and metastasis may help identify high-risk primary tumors. Finally, response to target therapy can be estimated thanks to differences in miRNA expression in tissue and serum of therapy-resistant versus therapy-sensitive patients.

Conclusions

Our understanding of the role of microRNAs in RCC pathogenesis has been increasing dramatically. Identification and validation of their gene targets may have direct impact on developing microRNA-based anticancer therapy. Several microRNAs can serve as diagnostic and prognostic biomarkers.

A decade of pharmacogenomics research on tyrosine kinase inhibitors in metastatic renal cell cancer: a systematic review

OBJECTIVE

The individual response to targeted tyrosine kinase inhibitors (TKIs) in the treatment of metastatic renal cell cancer (mRCC) is highly variable. Outlined in this article are findings on potential biomarkers for TKI treatment outcome in mRCC and an evaluation of the status of clinical implementation.

METHODS

Articles were selected by two independent reviewers using a systematic search in five medical databases on renal cell carcinoma, TKIs, and pharmacogenetics.

RESULTS

Many researchers have focused on predictive biomarkers for treatment outcome of targeted therapies in mRCC patients. Attempts to explain differences in efficacy and toxicity of TKIs by use of genetic variants in genes related to the pharmacokinetics and pharmacodynamics of the drug have been successful.

CONCLUSION

Most findings on potential biomarkers have not been validated and therefore biomarker testing to guide choice of therapy and dose in mRCC is not yet feasible.

microRNAs as pharmacogenomic biomarkers for drug efficacy and drug safety assessment

Much evidence has documented that microRNAs (miRNAs) play an important role in the modulation of interindividual variability in the production of drug metabolizing enzymes and transporters (DMETs) and nuclear receptors (NRs) through multidirectional interactions involving environmental stimuli/stressors, the expression of miRNA molecules and genetic polymorphisms. MiRNA expression has been reported to be affected by drugs and miRNAs themselves may affect drug metabolism and toxicity. In cancer research, miRNA biomarkers have been identified to mediate intrinsic and acquired resistance to cancer therapies. In drug safety assessment, miRNAs have been found associated with cardiotoxicity, hepatotoxicity and nephrotoxicity. This review article summarizes published studies to show that miRNAs can serve as early biomarkers for the evaluation of drug efficacy and drug safety.

MicroRNAs in clear cell renal cell carcinoma: biological functions and applications

MicroRNAs (miRs) are small noncoding RNAs that govern many biological processes. They frequently acquire a gain or a loss of function in cancer and hence play a causative role in the development and progression of neoplasms. They could be used as biomarkers to improve our knowledge on diagnosis, prognosis and drug resistance, and to attempt therapeutic approaches in several types of cancer including clear cell renal cell carcinoma (ccRCC). ccRCC is the most predominant subtype of RCC that accounts for about 90% of all renal cancers. Since ccRCC is generally asymptomatic until very late, it is difficult to diagnose early. Moreover, in the absence of preventive treatments for metastatic ccRCC after surgical resection of the primary cancer, predictive prognostic biomarkers are needed in order to achieve appropriate therapies. Herein the role of miRs in the biology of ccRCC and the potential applications of these molecules are discussed. Moreover, future applications in the diagnostic and prognostic field, as well as their impact on drug response and therapeutic targets are also explored. Their use in clinical practice as molecular biomarkers alone, or in combination with other biological markers could accelerate progress, help design personalized therapies, limit side effects, and improve quality of life of ccRCC patients.

miR-221/222 Are Involved in Response to Sunitinib Treatment in Metastatic Renal Cell Carcinoma

Sunitinib is a multitargeting tyrosine kinase inhibitor used for metastatic renal cancer. There are no biomarkers that can predict sunitinib response. Such markers are needed to avoid administration of costly medication with side effects to patients who would not benefit from it. We compared global miRNA expression between patients with a short (≤12 months) versus prolonged (>12 months) progression-free survival (PFS) under sunitinib as first-line therapy for metastatic renal cell carcinoma. We identified a number of differentially expressed miRNAs and developed miRNA statistical models that can accurately distinguish between the two groups. We validated our models in the discovery set and an independent set of 57 patients. Target prediction and pathway analysis showed that these miRNAs are involved in vascular endothelial growth factor (VEGF), TGFβ, and mammalian target of rapamycin (mTOR)-mediated signaling and cell-cell communication. We tested the effect of these miRNAs on cellular proliferation and angiogenesis. We validated the negative correlation between miR-221 and its target, VEGFR2.miR-221 overexpression was associated with a poor PFS while its target, VEGFR2 was associated with longer survival. Gain of function experiments showed that miR-221 and miR-222 decreased angiogenesis and cellular proliferation in human umbilical vein endothelial cells (HUVEC) while increasing cellular proliferation in ACHN cells. miRNAs represent potential predictive markers for sunitinib response.

Predictive molecular biomarkers to guide clinical decision making in kidney cancer: current progress and future challenges

Although the past decade has seen a surfeit of new targeted therapies for renal cell carcinoma (RCC), no predictive molecular biomarker is currently used in routine clinical practice to guide personalized therapy as a companion diagnostic. Many putative biomarkers have been suggested, but none have undergone rigorous validation. There have been considerable advances in the biological understanding of RCC in recent years, with the development of accompanying molecular diagnostics that with additional validation, may be helpful for routine clinical decision making. In this review, we summarize the current understanding of predictive biomarkers in RCC management and also highlight upcoming developments of interest in biomarker research for personalizing RCC diagnostics and therapeutics.

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

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

Resistance to sunitinib in renal cell carcinoma: From molecular mechanisms to predictive markers and future perspectives

The introduction of agents that inhibit tumor angiogenesis by targeting vascular endothelial growth factor (VEGF) signaling has made a significant impact on the survival of patients with metastasized renal cell carcinoma (RCC). Sunitinib, a tyrosine kinase inhibitor of the VEGF receptor, has become the mainstay of treatment for these patients. Although treatment with sunitinib substantially improved patient outcome, the initial success is overshadowed by the occurrence of resistance. The mechanisms of resistance are poorly understood. Insight into the molecular mechanisms of resistance will help to better understand the biology of RCC and can ultimately aid the development of more effective therapies for patients with this infaust disease. In this review we comprehensively discuss molecular mechanisms of resistance to sunitinib and the involved biological processes, summarize potential biomarkers that predict response and resistance to treatment with sunitinib, and elaborate on future perspectives in the treatment of metastasized RCC.

Expression of the tumor suppressive miRNA-23b/27b cluster is a good prognostic marker in clear cell renal cell carcinoma

PURPOSE

We observed abnormal expression of the microRNA-23b/27b (miR-23b/27b) cluster in our previous study of miRNA expression signatures. However, the relationship between aberrant miRNA expression and clear cell renal cell carcinoma is not well established. We investigated the functional significance of the miR-23b/27b cluster in clear cell renal cell carcinoma cells and evaluated these miRNAs as biomarkers to predict the risk of clear cell renal cell carcinoma.

MATERIALS AND METHODS

Expression levels of miR-23b and miR-27b were determined by quantitative real-time reverse transcriptase-polymerase chain reaction. The association between miRNA expression and overall survival was estimated by the Kaplan-Meier method. Gain of function assays were performed using mature miR-23b and miR-27b in the 786-O and A498 renal cell carcinoma cell lines. Targets regulated by these miRNAs were predicted by in silico analysis.

RESULTS

Expression of the miR-23b/27b cluster was significantly decreased in clear cell renal cell carcinoma tissue specimens and associated with pathological grade and stage. Significantly shorter overall survival was observed in patients with lower expression of the miR-23b/27b cluster. Restoration of miR-23b and miR-27b significantly inhibited cancer cell proliferation, migration and invasion.

CONCLUSIONS

Expression of the miR-23b/27b cluster was frequently decreased in clear cell renal cell carcinoma tissue. Reduced expression of these miRNAs increased the risk of disease progression and predicted poor survival. Thus, miR-23b and miR-27b function as tumor suppressors, targeting several oncogenic genes in clear cell renal cell carcinoma cells.

miR-129-3p, as a diagnostic and prognostic biomarker for renal cell carcinoma, attenuates cell migration and invasion via downregulating multiple metastasis-related genes

PURPOSE

Downregulation of miRNA expression has been identified as a novel feature of renal cell carcinoma (RCC). Recently, miR-129-2 is well known to be frequently reduced by DNA methylation and has anti-tumor effects in various tumors but so far not in RCC. The aim of this study was to investigate the clinical significance and the role of it in RCC.

METHODS

The expression levels of miR-129-3p and miR-129-5p, two mature products of miR-129-2, were determined by real-time quantitative reverse transcription PCR in 69 cases of paired different kidney tumors and normal tissues and clear cell RCC (ccRCC) cell lines. The roles of them in RCC cells were assessed by functional analyses. Protein expression was detected by Western blot.

RESULTS

miR-129-3p, but not miR-129-5p, was widely attenuated in human ccRCC, and chromophobe RCC. miR-129-3p could yield 73.5 % accuracy in discriminating ccRCCs from normal tissues. The relative miR-129-3p expression significantly differed between malignant and benign kidney tumors. Importantly, low miR-129-3p levels were associated with short disease-free and overall survival. Ectopic expression of miR-129-3p robustly impaired RCC cell migratory and invasive properties, but had no impact on cell viability and cell cycle distribution. Finally, miR-129-3p decreased multiple metastasis-related genes in RCC cells, including SOX4, phosphorylation of focal adhesion kinase and MMP-2/9 expression.

CONCLUSIONS

miR-129-3p may act as a promising diagnostic biomarker for discriminating ccRCC from benign tumors and normal tissues and an independent prognostic biomarker in ccRCC. miR-129-3p may exert its anti-metastatic function through modulating multiple targets.

Sunitinib resistance in renal cell carcinoma

Of the many targeted therapies introduced since 2006, sunitinib has carved its way to become the most commonly used first-line therapy for the treatment of metastatic renal cell carcinoma (RCC). Despite significant improvements in progression-free survival, 30% of the patients are intrinsically resistant to sunitinib and the remaining 70% who respond initially will eventually become resistant in 6-15 months. While the molecular mechanisms of acquired resistance to sunitinib have been unravelling at a rapid rate, the mechanisms of intrinsic resistance remain elusive. Combination therapy, sunitinib rechallenge and sequential therapy have been investigated as means to overcome resistance to sunitinib. Of these, sequential therapy appears to be the most promising strategy. This mini review summarises our emerging understanding of the molecular mechanisms, and the strategies employed to overcome sunitinib resistance.

miR-141 is a key regulator of renal cell carcinoma proliferation and metastasis by controlling EphA2 expression

PURPOSE

Although microRNAs (miRNA) have been revealed as crucial modulators of tumorigenesis, our understanding of their roles in renal cell carcinoma (RCC) is limited. Here we sought to identify human miRNAs that act as key regulators of renal carcinogenesis.

EXPERIMENTAL DESIGN

We performed microarray-based miRNA profiling of clear cell RCC (ccRCC) and adjacent normal tissues and then explored the roles of miR-141 both in vitro and in vivo, which was the most significantly downregulated in ccRCC tissues.

RESULTS

A total of 74 miRNAs were dysregulated in ccRCC compared with normal tissues. miR-141 was remarkably downregulated in 92.6% (63/68) ccRCC tissues and would serve as a promising biomarker for discriminating ccRCC from normal tissues with an area under the receiver operating characteristics curve of 0.93. Overexpression of miR-141 robustly impaired ccRCC cell migratory and invasive properties and suppressed cell proliferation by arresting cells at G0-G1 phase in vitro and in human RCC orthotopic xenografts. Significantly, the antitumor activities of miR-141 were mediated by its reversal regulation of erythropoietin-producing hepatocellular (Eph) A2 (EphA2), which then relayed a signaling transduction cascade to attenuate the functions of focal adhesion kinase (FAK), AKT, and MMP2/9. In addition, a specific and inverse correlation between miR-141 and EphA2 expression was obtained in human ccRCC samples. Finally, miR-141 could be secreted from the ccRCC donor cells, and be taken up and function moderately in the ccRCC recipient cells.

CONCLUSION

miR-141 serves as a potential biomarker for discriminating ccRCC from normal tissues and a crucial suppressor of ccRCC cell proliferation and metastasis by modulating the EphA2/p-FAK/p-AKT/MMPs signaling cascade.

MicroRNAs: master regulators of drug resistance, stemness, and metastasis

MicroRNAs (miRNAs) are 20-22 nucleotides long small non-coding RNAs that regulate gene expression post-transcriptionally. Last decade has witnessed emerging evidences of active roles of miRNAs in tumor development, progression, metastasis, and drug resistance. Many factors contribute to their dysregulation in cancer, such as chromosomal aberrations, differential methylation of their own or host genes' promoters and alterations in miRNA biogenesis pathways. miRNAs have been shown to act as tumor suppressors or oncogenes depending on the targets they regulate and the tissue where they are expressed. Because miRNAs can regulate dozens of genes simultaneously and they can function as tumor suppressors or oncogenes, they have been proposed as promising targets for cancer therapy. In this review, we focus on the role of miRNAs in driving drug resistance and metastasis which are associated with stem cell properties of cancer cells. Furthermore, we discuss systems biology approaches to combine experimental and computational methods to study effects of miRNAs on gene or protein networks regulating these processes. Finally, we describe methods to target oncogenic or replace tumor suppressor miRNAs and current delivery strategies to sensitize refractory cells and to prevent metastasis. A holistic understanding of miRNAs' functions in drug resistance and metastasis, which are major causes of cancer-related deaths, and the development of novel strategies to target them efficiently will pave the way towards better translation of miRNAs into clinics and management of cancer therapy.

Renal carcinoma pharmacogenomics and predictors of response: Steps toward treatment individualization

Molecular knowledge has deeply affected the treatment and outcome of kidney cancer in recent years, and several therapeutic options have become available. However, there are no validated biomarkers to select the best drug for each patient. Already published studies and ongoing investigations could change this scenario in the near future. Regarding antiangiogenic drugs, several works on single nucleotide polymorphisms have achieved promising results, with some SNPs predicting resistance to sunitinib and pazopanib being validated. If more evidence is gained, it could prompt prospective studies exploring a molecularly driven selection of treatment. Another relevant line of investigation for antiangiogenic drugs is the cytokines and antiangiogenic factors. Different studies have found that cytokines and antiangiogenic factors are able to predict the outcome of patients treated with sunitinib, pazopanib, or sorafenib. Issues regarding the thresholds of normality and the best time for assessment are pending, but the communicated results are encouraging. Less evidence is available for mammalian target of rapamycin inhibitors but recent data support a key role of the phosphoinositide 3-kinase/Akt pathway in clear cell renal cell carcinoma and points toward poor response to angiogenic drugs when the pathway is activated. Whether modern phosphoinositide 3-kinase inhibitors could be the best option for these patients is a question that should be addressed. Additionally, a new class of immunomodulators, like anti-programmed death 1 drugs, has demonstrated to achieve long-lasting stabilizations even in some patients with no radiological response or early progression. This is a singular situation where the identification of reliable predictors of efficacy will be key in the development of these drugs in renal cell carcinoma. Finally, germline mutations of the c-Met gene have been proposed as the first predictor of response to targeted therapies in papillary renal cell carcinoma. As a conclusion, translational research will be a cornerstone to move a next step forward in kidney cancer.

Prognostic significance of microRNA-141 expression and its tumor suppressor function in human pancreatic ductal adenocarcinoma

Increasing evidence shows that dysregulation of microRNAs is correlated with tumor development. This study was performed to determine the expression of miR-141 and investigate its clinical significance in pancreatic ductal adenocarcinoma (PDAC). Taqman quantitative RT-PCR was used to detect miR-141 expressions in 94 PDAC tissues and 16 nontumorous pancreatic tissues. Correlations between miR-141 expression and clinicopathologic features and prognosis of patients were statistically analyzed. The effects of miR-141 expression on growth and apoptosis of PDAC cell line (PANC-1) were determined by MTT, colony formation, and flow cytometry assays. Potential target genes were identified by luciferase reporter and Western blot assays. The expression level of miR-141 in PDAC tissues was significantly lower than that in corresponding nontumorous tissues. Downregulation of miR-141 correlated with poorer pT and pN status, advanced clinical stage, and lymphatic invasion. Also, low miR-141 expression in PDAC tissues was significantly correlated with shorter overall survival, and multivariate analysis showed that miR-141 was an independent prognostic factor for PDAC patients. Further, functional researches suggested that miR-141 inhibits growth and colony formation, and enhances caspase-3-dependent apoptosis in PANC-1 cells by targeting Yes-associated protein-1 (YAP1). Therefore, miR-141 is an independent prognostic factor for PDAC patients, and functions as a tumor suppressor gene by targeting YAP1.

Clear cell renal cell carcinoma associated microRNA expression signatures identified by an integrated bioinformatics analysis

Background

Clear cell renal cell carcinoma (ccRCC) represents the most invasive and common adult kidney neoplasm. Mounting evidence suggests that microRNAs (miRNAs) are important regulators of gene expression. But their function in tumourigenesis in this tumour type remains elusive. With the development of high throughput technologies such as microarrays and NGS, aberrant miRNA expression has been widely observed in ccRCC. Systematic and integrative analysis of multiple microRNA expression datasets may reveal potential mechanisms by which microRNAs contribute to ccRCC pathogenesis.

Methods

We collected 5 public microRNA expression datasets in ccRCC versus non-matching normal renal tissues from GEO database and published literatures. We analyzed these data sets with an integrated bioinformatics framework to identify expression signatures. The framework incorporates a novel statistic method for abnormal gene expression detection and an in-house developed predictor to assess the regulatory activity of microRNAs. We then mapped target genes of DE-miRNAs to different databases, such as GO, KEGG, GeneGo etc, for functional enrichment analysis.

Results

Using this framework we identified a consistent panel of eleven deregulated miRNAs shared by five independent datasets that can distinguish normal kidney tissues from ccRCC. After comparison with 3 RNA-seq based microRNA profiling studies, we found that our data correlated well with the results of next generation sequencing. We also discovered 14 novel molecular pathways that are likely to play a role in the tumourigenesis of ccRCC.

Conclusions

The integrative framework described in this paper greatly improves the inter-dataset consistency of microRNA expression signatures. Consensus expression profile should be identified at pathway or network level to address the heterogeneity of cancer. The DE-miRNA signature and novel pathways identified herein could provide potential biomarkers for ccRCC that await further validation.