MiR-148a attenuates paclitaxel resistance of hormone-refractory, drug-resistant prostate cancer PC3 cells by regulating MSK1 expression

miR 488* inhibits androgen receptor expression in prostate carcinoma cells

Androgen receptor (AR) is a ligand-dependent transcription factor, which plays a significant role in prostate carcinogenesis. Blockade of AR and its ligand, androgen is the basis for the treatment of prostate cancer (PCa). Nevertheless, a modest increase in the critical levels of AR mRNA and corresponding protein is sufficient for the development of resistance to antiandrogen therapy. A strategy to further downregulate AR mRNA and protein expression in combination with antiandrogen therapy may prevent or delay the development of androgen-independent PCa. Recent studies show that microRNAs (miRNAs) perform tumor suppressor functions in various cancers. In this study, we demonstrate that the overexpression of miR 488* downregulates the transcriptional activity of AR and inhibits the endogenous AR protein production in both androgen-dependent and androgen-independent PCa cells. In addition, miR 488* blocks the proliferation and enhances the apoptosis of PCa cells. Our data indicate that miR 488* targets AR and is a potential modulator of AR mediated signaling. Our findings provide insight for utilizing miRNAs as novel therapeutics to target AR in PCa.

miR-135a contributes to paclitaxel resistance in tumor cells both in vitro and in vivo

Cancer cell resistance to paclitaxel continues to be a major clinical problem. In this study, we utilized microRNA (miRNA) arrays to screen for differentially expressed miRNAs in paclitaxel-resistant cell lines established in vitro. We observed concordant upregulation of miR-135a in paclitaxel-resistant cell lines representing three human malignancies. Subsequently, the role of miRNA-135a was evaluated in an in vivo model of paclitaxel resistance. In this model, mice were inoculated subcutaneously with a non-small cell lung carcinoma cell line and treated with paclitaxel for a prolonged period. In paclitaxel-resistant cell lines, established either in vitro or in vivo, blockage of miR-135a sensitized resistant cell lines to paclitaxel-induced cell death. We further demonstrated a correlation between paclitaxel response and miR-135a expression in paclitaxel-resistant subclones that were established in vivo. The paclitaxel-resistant phenotype of these subclones was maintained upon retransplantation in new mice, as shown by decreased tumor response upon paclitaxel treatment compared with controls. Upregulation of miR-135a was associated with reduced expression of the adenomatous polyposis coli gene (APC). APC knockdown increased paclitaxel resistance in parental cell lines. Our results indicate that paclitaxel resistance is associated with upregulation of miR-135a, both in vitro and in vivo, and is in part determined by miR-135a-mediated downregulation of APC.

miR-148a promoted cell proliferation by targeting p27 in gastric cancer cells

Accumulating evidence has shown that miRNAs are aberrantly expressed in human gastric cancer and crucial to tumorigenesis. Herein, we identified the role of miR-148a in gastric cell proliferation. miR-148a knockdown inhibited cell proliferation in gastric cancer cell lines. Conversely, miR-148a overexpression promoted cell proliferation and cell cycle progression. p27, a key inhibitor of cell cycle, was verified as the target of miR-148a, indicating miR-148a might downregulate p27 expression to promote gastric cell proliferation. Moreover, we confirmed that miR-148a expression was frequently and dramatically downregulated in human advanced gastric cancer tissues, and observed a good inverse correlation between miR-148a and p27 expression in tumor samples. Thus, our results demonstrated that miR-148a downregulation might exert some sort of antagonistic function in cell proliferation, rather than promote cell proliferation in gastric cancer.

Mir-148a improves response to chemotherapy in sensitive and resistant oesophageal adenocarcinoma and squamous cell carcinoma cells

BACKGROUND

Response to chemotherapy varies widely in patients with advanced oesophageal cancer. We investigated the impact of manipulating certain microRNAs on response to cisplatin and 5-fluorouracil (5-FU) in oesophageal cancer cells.

METHODS

Cisplatin-/5-fluorouracil-resistant oesophageal squamous cell carcinoma (SCC) and adenocarcinoma (EAC) cell lines were established, and the impact of ectopic upregulation of miR-106a and miR-148a on response to both drugs was assessed.

RESULTS

The impact of miR-106a-upregulation was inconsistent. Upregulation was followed by reduced sensitivity to cisplatin in chemotherapy-sensitive EAC cells (cell survival, +8.7 ± 0.8%; p = 0.003) and an improved response to 5-FU in cisplatin-resistant EAC cells (cell survival, -6.4 ± 2.5%; p = 0.011). MiR-148a upregulation significantly increased sensitivity to chemotherapy in seven out of ten cell lines, represented by a decrease in cell viability of 22.6 ± 7.9% to 50.5 ± 10.6% after cisplatin (p ≤ 0.014) and 6.0 ± 0.8% to 15.0 ± 4.1% after 5-FU treatment (p ≤ 0.012). The only cell lines in which miR-148a upregulation had no effect were cisplatin-resistant EAC exposed to cisplatin and 5-FU-sensitive and 5-FU-resistant SCC cells exposed to 5-FU.

CONCLUSION

MiR-148a sensitized chemotherapy-sensitive oesophageal cancer cell lines to cisplatin and, to a lesser extent, to 5-flurouracil and attenuated resistance in chemotherapy-resistant variants. Further experimental and clinical studies to investigate the exact mechanisms involved are warranted.

MicroRNA in prostate, bladder, and kidney cancer: a systematic review

CONTEXT

MicroRNAs (miRNA) are noncoding RNAs that post-transcriptionally regulate gene expression. Their altered expression and function have been observed in most urologic cancers. MiRNAs represent potential disease biomarkers and novel therapeutic targets.

OBJECTIVE

To review and evaluate the evidence implicating miRNAs in the pathogenesis of prostate cancer (PCa), bladder cancer (BCa), and renal cancer.

EVIDENCE ACQUISITION

A systematic review was performed using PubMed and Embase to search for reports using strings for microRNA, non-coding RNA, cancer, prostate, bladder, and renal cancer. Identified manuscripts were retrieved and references searched. Selected studies were required to concentrate on the role of miRNA in these urologic cancers.

EVIDENCE SYNTHESIS

We reviewed articles that focus on this topic. More than 40 miRNAs have been implicated in urologic cancer and many target common carcinogenic pathways. In particular, apoptosis avoidance, cell proliferation, epithelial-to-mesenchymal transition, angiogenic signalling, and the generation of androgen independence are targeted or facilitated by more than one miRNA. Little work has been done to evaluate the translational applications for this knowledge to date. Novel therapeutic strategies have been developed and are under investigation to selectively modulate miRNAs; such work would potentially enable personalised tumour therapy.

CONCLUSIONS

MiRNAs appear to be important modulators of urologic cancer. Their expression is frequently altered in these tumours, and many are functionally implicated in their pathogenesis. They require evaluation to determine the translational role and therapeutic potential for this knowledge.

MicroRNAs and Androgen Receptor 3' Untranslated Region: A Missing Link in Castration-resistant Prostate Cancer?

The ligand-activated transcription factor, androgen receptor (AR) plays a central role in the development and progression of prostate cancer. Prostate cancer initiates as an androgen-dependent disease and further accumulation of multiple sequential genetic and epigenetic alterations transform it into an aggressive, castration-resistant prostate cancer (CRPC). The molecular basis of the transition from androgen-dependent prostate cancer to CRPC remains unclear. However, it is apparent that AR plays a pivotal role in this alteration. The recent discovery that microRNAs (miRNAs) can target the function of AR suggests a functional role of these non-coding RNAs in the pathogenesis of prostate cancer. miRNAs usually function by targeting the 3' untranslated region (UTR) of a mRNA by base-pairing interactions and modulate translation either by destabilizing the message or by repression of protein synthesis in actively translating ribosomes. Here, we discuss the potential molecular pathways through which AR targeting miRNAs may promote CRPC. Modulation of AR expression by miRNAs presents a novel therapeutic option for prostate cancer, albeit it will likely be used in combination with the existing therapies.

MicroRNA-148/152 impair innate response and antigen presentation of TLR-triggered dendritic cells by targeting CaMKIIα

MicroRNAs (miRNAs) are involved in the regulation of immunity, including the lymphocyte development and differentiation, and inflammatory cytokine production. Dendritic cells (DCs) play important roles in linking innate and adaptive immune responses. However, few miRNAs have been found to regulate the innate response and APC function of DCs to date. Calcium/calmodulin-dependent protein kinase II (CaMKII), a major downstream effector of calcium (Ca(2+)), has been shown to be an important regulator of the maturation and function of DCs. Our previous study showed that CaMKIIα could promote TLR-triggered production of proinflammatory cytokines and type I IFN. Inspired by the observations that dicer mutant Drosophila display defect in endogenous miRNA generation and higher CaMKII expression, we wondered whether miRNAs can regulate the innate response and APC function of DCs by targeting CaMKIIα. By predicting with software and confirming with functional experiments, we demonstrate that three members of the miRNA (miR)-148 family, miR-148a, miR-148b, and miR-152, are negative regulators of the innate response and Ag-presenting capacity of DCs. miR-148/152 expression was upregulated, whereas CaMKIIα expression was downregulated in DCs on maturation and activation induced by TLR3, TLR4, and TLR9 agonists. We showed that miR-148/152 in turn inhibited the production of cytokines including IL-12, IL-6, TNF-α, and IFN-β upregulation of MHC class II expression and DC-initiated Ag-specific T cell proliferation by targeting CaMKIIα. Therefore, miRNA-148/152 can act as fine-tuner in regulating the innate response and Ag-presenting capacity of DCs, which may contribute to the immune homeostasis and immune regulation.

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.

Microtubule-binding agents: a dynamic field of cancer therapeutics

Microtubules are dynamic filamentous cytoskeletal proteins composed of tubulin and are an important therapeutic target in tumour cells. Agents that bind to microtubules have been part of the pharmacopoeia of anticancer therapy for decades and until the advent of targeted therapy, microtubules were the only alternative to DNA as a therapeutic target in cancer. The screening of a range of botanical species and marine organisms has yielded promising new antitubulin agents with novel properties. In the current search for novel microtubule-binding agents, enhanced tumour specificity, reduced neurotoxicity and insensitivity to chemoresistance mechanisms are the three main objectives.

miR-148a is an androgen-responsive microRNA that promotes LNCaP prostate cell growth by repressing its target CAND1 expression

Recent advances in cancer biology reveal that microRNAs (miRNAs) are involved in the regulation of cancer-related genes, or they function as tumor suppressors or oncogenes. In prostate cancer, evidence has accumulated for the contribution of the androgen-dependent gene network to tumor growth, although the precise functions of miRNAs in prostate cancer remain to be investigated. Here, we identified androgen-responsive miRNAs by the short RNA sequencing analysis in LNCaP prostate cancer cells. Among 10 miRNAs with known sequences, we have determined that miR-148a reduces the expression of cullin-associated and neddylation-dissociated 1 (CAND1), a negative regulator of SKP1-Cullin1-F-box (SCF) ubiquitin ligases, by binding to the 3'-untranslated region of CAND1 mRNA. CAND1 knockdown by small interfering RNA promoted the proliferation of LNCaP cells. Our study indicates the potential contribution of miR-148a to the growth of human prostate cancer.