MiR-138 indirectly regulates the MDR1 promoter by NF-κB/p65 silencing

MicroRNA-138: an emerging regulator of skeletal development, homeostasis, and disease

Noncoding microRNAs are powerful epigenetic regulators of cellular processes by their ability to target and suppress expression of numerous protein-coding mRNAs. This multitargeting function is a unique and complex feature of microRNAs. It is now well-described that microRNAs play important roles in regulating the development and homeostasis of many cell/tissue types, including those that make up the skeletal system. In this review, we focus on microRNA-138 (miR-138) and its effects on regulating bone and cartilage cell differentiation and function. In addition to its reported role as a tumor suppressor, miR-138 appears to function as an inhibitor of osteoblast differentiation. This review provides additional information on studies that have attempted to alter miR-138 expression in vivo as a means to dampen ectopic calcification or alter bone mass. However, a review of the published literature on miR-138 in cartilage reveals a number of contradictory and inconclusive findings with respect to regulating chondrogenesis and chondrocyte catabolism. This highlights the need for more research in understanding the role of miR-138 in cartilage biology and disease. Interestingly, a number of studies in other systems have reported miR-138-mediated effects in dampening inflammation and pain responses. Future studies will reveal if a multifunctional role of miR-138 involving suppression of ectopic bone, inflammation, and pain will be beneficial in skeletal conditions such as osteoarthritis and heterotopic ossification.

Regulation of P-Glycoprotein in the Brain

Maintenance of the tightly regulated homeostatic environment of the brain is facilitated by the blood-brain barrier (BBB). P-glycoprotein (P-gp), an ATP-binding cassette transporter, is expressed on the luminal surface of the endothelial cells in the BBB, and actively exports a wide variety of substrates to limit exposure of the vulnerable brain environment to waste buildup and neurotoxic compounds. Downregulation of P-gp expression and activity at the BBB have been reported with ageing and in neurodegenerative diseases. Upregulation of P-gp at the BBB contributes to poor therapeutic outcomes due to altered pharmacokinetics of CNS-acting drugs. The regulation of P-gp is highly complex, but unravelling the mechanisms involved may help the development of novel and nuanced strategies to modulate P-gp expression for therapeutic benefit. This review summarises the current understanding of P-gp regulation in the brain, encompassing the transcriptional, post-transcriptional and post-translational mechanisms that have been identified to affect P-gp expression and transport activity.

An engineered abcb4 expression model reveals the central role of NF-κB in the regulation of drug resistance in zebrafish

Multi-drug resistance (MDR) is a phenomenon that tumor cells are exposed to a chemotherapeutic drug for a long time and then develop resistance to a variety of other anticancer drugs with different structures and different mechanisms. The in vitro studies of tumor cell lines cannot systematically reflect the role of MDR gene in vivo, and the cost of in vivo studies of transgenic mice as animal models is high. Given the myriad merits of zebrafish relative to other animal models, we aimed to establish a screening system using zebrafish stably expressing ATP-binding cassette (ATP-cassette) superfamily transporters and unveil the potential regulatory mechanism. We first used the Tol2-mediated approach to construct a Tg (abcb4:EGFP) transgenic zebrafish line with ATP-binding cassette (ABC) subfamily B member 4 (abcb4) gene promoter to drive EGFP expression. The expression levels of abcb4 and EGFP were significantly increased when Tg(abcb4:EGFP) transgenic zebrafish embryos were exposed to doxorubicin (DOX) or vincristine (VCR), and the increases were accompanied by a marked decreased accumulation of rhodamine B (RhB) in embryos, indicating a remarkable increase in DOX or VCR efflux. Mechanistically, Akt and Erk signalings were activated upon the treatment with DOX or VCR. With the application of Akt and Erk inhibitors, drug resistance was reversed with differing responsive effects. Notably, downstream NF-κB played a central role in the regulation of abcb4-mediated drug resistance. Taken together, the data indicate that the engineered Tg(abcb4:EGFP) transgenic zebrafish model is a new platform for screening drug resistance in vivo, which may facilitate and accelerate the process of drug development.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Delivery of novel coumarin-dihydropyrimidinone conjugates through mixed polymeric nanoparticles to potentiate therapeutic efficacy against triple-negative breast cancer

To date, most of the accessible therapeutic options are virtually non-responsive towards triple-negative breast cancer (TNBC) due to its highly aggressive and metastatic nature. Interestingly, chemotherapy reacts soundly in many TNBC cases compared to other types of breast cancer. However, the side effects of many chemotherapeutic agents are still under cross-examination, and thus prohibit their extensive uses. In this present study, we have developed a series of coumarin-dihydropyrimidinone conjugates (CDHPs) and subsequently their poly(lactic-co-glycolic acid) (PLGA)-PEG₄₀₀₀ mixed copolymer nanoparticles as excellent chemotherapeutic nanomedicine to control TNBC. Among all the synthesized CDHPs, CDHP-4 (prepared by the combination of EDCO with 3,4-difluorobenzaldehyde) showed excellent therapeutic effect on a wide variety of cancer cell lines, including TNBC. Besides, it can control the metastasis and stemness property of TNBC. Furthermore, the nano-encapsulation of CDHP-4 in a mixed polymer nanoparticle system (CDHP-4@PP-NPs) and simultaneous delivery showed much improved therapeutic efficacy at a much lower dose, and almost negligible side effects in normal healthy cells or organs. The effectiveness of the present therapeutic agent was observed both in intravenous and oral mode of administration in in vivo experiments. Moreover, on elucidating the molecular mechanism, we found that CDHP-4@PP-NPs could exhibit apoptotic, anti-migratory, as well as anti-stemness activity against TNBC cell lines through the downregulation of miR-138. We validated our findings in MDA-MB-231 xenograft chick embryos, as well as in 4T1-induced mammary tumor-bearing BALB/c mice models, and studied the bio-distribution of CDHP-4@PP-NPs on the basis of the photoluminescence property of nanoparticles. Our recent study, hence for the first time, unravels the synthesis of CDHP-4@PP-NPs and the molecular mechanism behind the anti-migration, anti-stemness and anti-tumor efficacy of the nanoparticles against the TNBC cells through the miR-138/p65/TUSC2 axis.

Nodal is involved in chemoresistance of renal cell carcinoma cells via regulation of ABCB1

Renal cell carcinoma (RCC) is the third most frequent malignancy within urological oncology. Understanding mechanisms of chemoresistance in RCC cell is important for therapy and drug development. We established cisplatin (CDDP) resistant RCC cells by treating cells with increasing concentrations of CDDP. Nodal, an important embryonic morphogen, was increased in RCC/CDDP cells. Targeted inhibition of Nodal via its siRNA or neutralization antibody restored sensitivity of RCC resistant cells to CDDP treatment. It was due to that si-Nodal can decrease expression of P-glycoprotein (P-gp, encoded by ABCB1), one important ATP-binding cassette (ABC) membrane transporter for drug efflux. si-Nodal can decrease the transcription and promoter activity of ABCB1. Mechanistically, si-Nodal can decrease the phosphorylation of p65, which can bind to the promoter of ABCB1 and then trigger its transcription. Further, CDDP treatment decreased the expression of Nodal in culture medium of RCC cells. Collectively, we found that Nodal can regulate chemoresistance of RCC cells via regulating transcription of ABCB1.

Evaluation of miRNAs Related with Nuclear Factor Kappa B Pathway in Lipopolysaccharide Induced Acute Respiratory Distress Syndrome

This study aimed to determine the expression of nuclear factor kappa B (NF-κB) pathway related miRNAs in experimental acute respiratory distress syndrome (ARDS) induced by lipopolysaccharide (LPS) in rats, and to elucidate the underlying molecular mechanism. Twenty four sprague dawley rats were randomly divided into two groups; LPS (n = 12) and control (n = 12). Experimental ARDS was induced by intraperitoneal injection of E. coli LPS in LPS group. Intraperitoneal saline was administered in control group. Serum and lung samples were collected from both groups. Immunohistochemistry staining was performed for interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), CD 68, and caspase-3 in lung samples. Intensity of staining was scored as strong, moderate, weak, and no for evaluation of IL-1β and TNF-α. In addition, caspase-3 and CD68-positive stained cells were counted in sections. Expressions of 9 miRNAs were determined by quantitative real-time PCR in serum samples. IL-1β and TNF-α staining scores were significantly higher in the LPS group in comparison with the control group (P = 0.04 and P = 0.02, respectively). In addition, caspase-3 and CD68-positive stained cells were significantly higher in the LPS group (P = 0.02). Expressions of seven miRNAs were significantly changed in the LPS group in comparison with the control group. While six miRNAs (miR-7a-5p, miR-7b, miR-9a-5p, miR-21-5p, miR-29a-3p, and miR-138-5p) were up regulated, only miR-124-3p was down regulated. This study suggests that these miRNAs may have a role in the pathogenesis of ARDS related to NF-κB. However, this relationship needs to be examined in new studies by evaluation of pathways and target genes.

HMGB1 Inhibits HNF1A to Modulate Liver Fibrogenesis via p65/miR-146b Signaling

High mobility group box 1 (HMGB1) is essential for the pathogenesis of liver injury and liver fibrosis. We previously revealed that miR-146b promotes hepatic stellate cells (HSCs) activation and proliferation. Nevertheless, the potential mechanisms are still unknown. Herein, HMGB1 increased HSCs proliferation and COL1A1 and α-SMA protein levels. However, the knockdown of miR-146b inhibited HSCs proliferation and COL1A1 and α-SMA protein levels induced via HMGB1 treatment. miR-146b was upregulated by HMGB1 and miR-146b targeted hepatocyte nuclear factor 1A (HNF1A) 3'-untranslated region (3'UTR) to modulate its expression negatively. Further, we confirmed that HMGB1 might elicit miR-146b expression via p65 within HSCs. Knockdown or block of HMGB1 relieved the CCl₄-induced liver fibrosis. In fibrotic liver tissues, miR-146b expression was positively correlated with p65 mRNA, but HNF1A mRNA was inversely correlated with p65, and miR-146b expression. In summary, our findings suggest that HMGB1/p65/miR-146b/HNF1A signaling exerts a crucial effect on liver fibrogenesis via the regulation of HSC function.

miRNA-based biomarkers, therapies, and resistance in Cancer

MicroRNAs (miRNAs), small non-coding RNAs (ncRNAs) of about 22 nucleotides in size, play important roles in gene regulation, and their dysregulation is implicated in human diseases including cancer. A variety of miRNAs could take roles in the cancer progression, participate in the process of tumor immune, and function with miRNA sponges. During the last two decades, the connection between miRNAs and various cancers has been widely researched. Based on evidence about miRNA, numerous potential cancer biomarkers for the diagnosis and prognosis have been put forward, providing a new perspective on cancer screening. Besides, there are several miRNA-based therapies among different cancers being conducted, advanced treatments such as the combination of synergistic strategies and the use of complementary miRNAs provide significant clinical benefits to cancer patients potentially. Furthermore, it is demonstrated that many miRNAs are engaged in the resistance of cancer therapies with their complex underlying regulatory mechanisms, whose comprehensive cognition can help clinicians and improve patient prognosis. With the belief that studies about miRNAs in human cancer would have great clinical implications, we attempt to summarize the current situation and potential development prospects in this review.

Citrus auraptene induces drug efflux transporter P-glycoprotein expression in human intestinal cells

P-glycoprotein (encoded by MDR1) is a membrane transport protein expressed in the intestine, liver, kidney, placenta, and blood-brain barrier. It excludes various clinically important drugs from cells, such as verapamil, digoxin, tacrolimus, and vinblastine. Therefore, human P-glycoprotein plays important roles in drug absorption, distribution, and excretion. We reported previously that auraptene, a natural compound occurring widely in citrus fruit (e.g., grapefruit), inhibited P-glycoprotein-mediated drug transport. In this study, we investigated the effects of auraptene and other phenylpropanoids on P-glycoprotein expression using human intestinal epithelial LS174T cells and a reporter plasmid expressing 10.2 kbp of the upstream regulatory region of MDR1. Auraptene (7-geranyloxycoumarin), a prenylated coumarin, and several phenylpropanoids, such as 3-(4'-geranyloxy-3'-methoxyphenyl)-2-trans propenoic acid, derricidin [2'-hydroxy-4'-(prenyloxy)chalcone], and 3-(4'-geranyloxyphenyl)-propanoic acid, induced MDR1 promoter activity in LS174T cells. Overexpression of the nuclear receptor human pregnane X receptor gene (NR1I2) enhanced auraptene-induced MDR1 activation. Nuclear factor-kappaB inhibitors, Bay11-7082 and JSH-23, repressed MDR1 activation by auraptene. Western blot analyses showed the induction of P-glycoprotein expression in the auraptene-treated LS174T cells. The citrus phytochemical auraptene can induce the drug efflux transporter P-glycoprotein in human intestinal cells, and thus has the potential to cause food-drug interactions.

N6-methyladenosine-induced ERRγ triggers chemoresistance of cancer cells through upregulation of ABCB1 and metabolic reprogramming

Background: Drug resistance severely reduces treatment efficiency of chemotherapy and leads to poor prognosis. However, regulatory factors of chemoresistant cancer cells are largely unknown. Methods: The expression of estrogen receptor related receptors (ERRs) in chemoresistant cancer cells are checked. The roles of ERRγ in chemoresistance are confirmed by in vitro and in vivo studies. The mechanisms responsible for ERRγ-regulated expression of ABCB1 and CPT1B are investigated. Results: The expression of ERRγ is upregulated in chemoresistant cancer cells. Targeted inhibition of ERRγ restores the chemosensitivity. ERRγ can directly bind to the promoter of ABCB1 to increase its transcription. An elevated interaction between ERRγ and p65 in chemoresistant cells further strengthens transcription of ABCB1. Further, ERRγ can increase the fatty acid oxidation (FAO) in chemoresistant cells via regulation of CPT1B, the rate-limiting enzyme of FAO. The upregulated ERRγ in chemoresistant cancer cells might be due to increased levels of N6-methyladenosine (m6A) can trigger the splicing of precursor ESRRG mRNA. Conclusions: m6A induced ERRγ confers chemoresistance of cancer cells through upregulation of ABCB1 and CPT1B.

ABC Transporters: Regulation and Association with Multidrug Resistance in Hepatocellular Carcinoma and Colorectal Carcinoma

For most cancers, the treatment of choice is still chemotherapy despite its severe adverse effects, systemic toxicity and limited efficacy due to the development of multidrug resistance (MDR). MDR leads to chemotherapy failure generally associated with a decrease in drug concentration inside cancer cells, frequently due to the overexpression of ABC transporters such as P-glycoprotein (P-gp/MDR1/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2), which limits the efficacy of chemotherapeutic drugs. The aim of this review is to compile information about transcriptional and post-transcriptional regulation of ABC transporters and discuss their role in mediating MDR in cancer cells. This review also focuses on drug resistance by ABC efflux transporters in cancer cells, particularly hepatocellular carcinoma (HCC) and colorectal carcinoma (CRC) cells. Some aspects of the chemotherapy failure and future directions to overcome this problem are also discussed.

Ferulic acid reverses P-glycoprotein-mediated multidrug resistance via inhibition of PI3K/Akt/NF-κB signaling pathway

In this study, the modulatory effect of ferulic acid on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) was examined in KB Ch^R8-5 resistant cells and drug-resistant tumor xenografts. We observed that ferulic acid enhanced the cytotoxicity of doxorubicin and vincristine in the P-gp overexpressing KB Ch^R8-5 cells. Further, ferulic acid enhances the doxorubicin induced γH2AX foci formation and synergistically augmented doxorubicin-induced apoptotic signaling in the drug-resistant cells. It has also been noticed that NF-κB nuclear translocation was suppressed by ferulic acid and that this response might be associated with the modulation of phosphatidyinositol 3-kinase (PI3K)/Akt/signaling pathway. We also found that ferulic acid and doxorubicin combination reduced the size of KB Ch^R8-5 tumor xenograft by threefold as compared to doxorubicin-alone treated group. Thus, ferulic acid contributes to the reversal of the MDR through suppression of P-gp expression via the inhibition of PI3K/Akt/NF-κB signaling pathway.

MicroRNA-298 Reverses Multidrug Resistance to Antiepileptic Drugs by Suppressing MDR1/P-gp Expression in vitro

P-glycoprotein (P-gp), a critical multidrug transporter, recognizes and transports various antiepileptic drugs (AEDs) through the blood-brain barrier (BBB). This may decrease the concentrations of AEDs in brain tissues and cause multidrug resistance (MDR) in patients with refractory epilepsy. Compelling evidence indicates that microRNAs (miRNAs) modulate MDR in various cancers by regulating P-gp expression. Furthermore, a previous study showed that miR-298 mediates MDR in breast cancer cells by downregulating P-gp expression. Based on the therapeutic results obtained from tumor cells, we aimed to determine whether miR-298 reverses MDR to AEDs by regulating P-gp expression in the BBB. We first established different drug-resistant cell lines, including PHT-resistant HBMECs (human brain microvascular endothelial cells) and doxorubicin (DOX)-resistant U87-MG (human malignant glioma) cells, by inducing P-gp overexpression. Quantitative real-time PCR (qRT-PCR) analysis revealed reduced expression of miR-298 in both HBMEC/PHT and U87-MG/DOX cells, and the luciferase reporter assay identified the direct binding of miR-298 to the 3′-untranslated region (3′-UTR) of P-gp. Moreover, ectopic expression of miR-298 downregulated P-gp expression at the mRNA and protein levels, thereby increasing the intracellular accumulation of AEDs in drug-resistant HBMEC/PHT and U87-MG/DOX cells. Thus, our findings suggest that miR-298 reverses MDR to AEDs by inhibiting P-gp expression, suggesting a potential target for overcoming MDR in refractory epilepsy.

TIPE2 sensitizes osteosarcoma cells to cis-platin by down-regulating MDR1 via the TAK1- NF-κB and - AP-1 pathways

TIPE2 participates in multiple types of cancer development. However, its mechanism underlying chemoresistance in osteosarcoma has not been elucidated. Herein, we observed the expression of TIPE2 and MDR1 in cis-platin-resistant osteosarcoma tissues and cell lines. Compared to their matched sensitive cell lines and tissues, TIPE2 was downregulated while MDR1 expression was increased. Further investigation showed that overexpression of TIPE2 effectively inhibited MDR1 expression and greatly sensitized osteosarcoma cells to cis-platin, both in vivo and in vitro. Mechanistically, TIPE2 inhibited the transcription of the MDR1 promoter by interfering with the TAK1-NF-κB and -AP-1 pathways. Overall, our results elucidated for the first time that TIPE2 sensitizes osteosarcoma cells to cis-platin through downregulation of MDR1 and may be a novel target in osteosarcoma therapy.

Combination chemotherapy with Zyflamend reduced the acquired resistance of bladder cancer cells to cisplatin through inhibiting NFκB signaling pathway

Background

Cisplatin-based chemotherapy is mainstay treatment in urinary bladder cancer (UBC). However, tumor recurrence frequently occurs with the acquisition of cisplatin resistance. We explored the potential effect of a polyherbal preparation, Zyflamend, on UBC cells resistant to cisplatin treatment.

Methods

To establish a cisplatin-resistant human bladder cancer cell line, T24 cells were cultured in increasing concentrations of cisplatin for more than 10 months. These cells (T24R) were then treated with different concentrations of Zyflamend, and both proliferation and activity of nuclear factor kappaB (NFκB) signaling pathway were examined. To test the synergistic effect between Zyflamend and cisplatin, we treated T24R cells either with Zyflamend or cisplatin alone, or in combination. Apoptotic effect was evaluated by Annexin V/propidium iodide double staining, and the levels of the proteins involved in cell cycle and anti-apoptosis were examined by Western blotting. Finally, mice with palpable xenograft were treated either with cisplatin and Zyflamend alone or in combination for 28 days before they were sacrificed for measuring the sizes and weights of the tumor tissues. In addition, proliferation and apoptosis markers were examined by immunohistochemistry.

Results

Comparing to that in the parental T24 cells, NFκB is constitutively active in cisplatin-resistant T24R cells. Zyflamend is capable of inhibiting the growth of T24, T24R, as well as another UBC cell line J82 in a concentration-dependent manner. Mechanistically, Zyflamend suppresses NFκB-mediated cell proliferation, survival, and invasion/angiogenesis and induces apoptosis. In addition, Zyflamend significantly increased the sensitivity of T24R and J82 cells to cisplatin treatment and these findings were confirmed in T24R xenograft model with reduced proliferation index and decreased expression of RelA and its downstream target MMP9.

Conclusion

Zyflamend is capable of counteracting bladder cancer resistance to cisplatin by repressing proliferation and inducing apoptosis through targeting NFκB signaling pathway.

Dexmedetomidine impairs P‑glycoprotein‑mediated efflux function in L02 cells via the adenosine 5'‑monophosphate‑activated protein kinase/nuclear factor‑κB pathway

Dexmedetomidine (DEX) a type of the anaesthetic that has been widely used in anaesthesia and intensive care. However, whether DEX affects the pharmacokinetics of drugs remains elusive. As hepatic P-glycoprotein (P-gp) serves a critical role in the disposition of drugs, the present study aimed to address whether P-gp function could be affected by DEX in vitro. In the present study, L02 cells (a normal human liver cell line) were exposed to DEX for 24 h and P-gp function was evaluated by the intracellular accumulation of Rhodamine 123. The results indicated that P-gp function was significantly impaired by DEX treatment and that the mRNA levels and protein levels of P-gp were downregulated in a dose- and time-dependent manner. Importantly, DEX-induced downregulation of P-gp was associated with adenosine 5′-monophosphate-activated protein kinase (AMPK) activation, as it was significantly attenuated by AMPK inhibition using dorsomorphin. Furthermore, the results revealed that changes in the subcellular localisation of nuclear factor (NF)-κB following AMPK activation were involved in the P-gp regulation in response to DEX treatment. Collectively, these results suggested that DEX impairs P-glycoprotein-mediated efflux function in L02 cells via the AMPK/NF-κB pathway, which provided direct evidence that the hepatic disposition of drugs may be affected by DEX through the downregulation of P-gp.

Fascin promotes migration and invasion and is a prognostic marker for oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) prognosis is related to clinical stage and histological grade. However, this stratification needs to be refined. We conducted a comparative proteome study in microdissected samples from normal oral mucosa and OSCC to identify biomarkers for malignancy. Fascin and plectin were identified as differently expressed and both are implicated in several malignancies, but the clinical impacts of aberrant fascin and plectin expression in OSCCs remains largely unknown. Immunohistochemistry and real-time quantitative PCR were carried out in ex vivo OSCC samples and cell lines. A loss-of-function strategy using shRNA targeting fascin was employed to investigate in vitro and in vivo the fascin role on oral tumorigenesis. Transfections of microRNA mimics were performed to determine whether the fascin overexpression is regulated by miR-138 and miR-145. We found that fascin and plectin are frequently upregulated in OSCC samples and cell lines, but only fascin overexpression is an independent unfavorable prognostic indicator of disease-specific survival. In combination with advanced T stage, high fascin level is also an independent factor of disease-free survival. Knockdown of fascin in OSCC cells promoted cell adhesion and inhibited migration, invasion and EMT, and forced expression of miR-138 in OSCC cells significantly decreased the expression of fascin. In addition, fascin downregulation leads to reduced filopodia formation and decrease on paxillin expression. The subcutaneous xenograft model showed that tumors formed in the presence of low levels of fascin were significantly smaller compared to those formed with high fascin levels. Collectively, our findings suggest that fascin expression correlates with disease progression and may serve as a prognostic marker and therapeutic target for patients with OSCC.

Induction of alpha-methylacyl-CoA racemase by miR-138 via up-regulation of β-catenin in prostate cancer cells

PURPOSE

Alpha-methylacyl-CoA racemase (AMACR) is highly overexpressed in prostate cancer (PCa) and its transcriptional regulators include various transcription factors and CTNNB1/β-catenin. Our previous findings suggested a post-transcriptional regulation by the tumor-suppressive microRNA miR-138 in PCa. Thus, the aim of this study was to demonstrate the direct interaction of miR-138 with the 3'-UTR of AMACR. Furthermore, the influence of miR-138 on the expression of AMACR and selected AMACR regulators was investigated in PCa cells.

METHODS

Using DU-145, PC-3, and LNCaP PCa cells, the effect of exogenous miR-138 on AMACR and selected AMACR regulators was determined by quantitative PCR and Western blot. Luciferase reporter assays were used to verify target and promoter interaction.

RESULTS

Using a luciferase reporter assay a direct interaction of miR-138 with the AMACR-3'-UTR was confirmed. Surprisingly, AMACR expression was up-regulated by up to 125% by exogenous miR-138 in PCa cells. The lack of any miR-138 binding sites within the AMACR promoter suggested an indirect mechanism of up-regulation. Therefore, the effect of miR-138 on selected AMACR regulators including CTNNB1/β-catenin, RELA, SMAD4, SP1, and TCF4 was evaluated. MiR-138 solely evoked an up-regulation of CTNNB1 mRNA expression and β-catenin protein levels by up to 75%. Further in silico analysis revealed a binding site for miR-138 within the CTNNB1 promoter. MiR-138 could enhance the activity of the CTNNB1 promoter, which in turn could contribute to the observed AMACR up-regulation.

CONCLUSIONS

The present findings suggest that miR-138 can indirectly up-regulate AMACR via transcriptional induction of CTNNB1, at least in vitro in PCa cells.