Mei Qi

Metformin inhibits epithelial–mesenchymal transition in prostate cancer cells: Involvement of the tumor suppressor miR30a and its target gene SOX4

Tumor metastasis is the leading cause of mortality and morbidity of prostate cancer (PCa) patients. Epithelial-mesenchymal transition (EMT) plays a critical role in cancer progression and metastasis. Recent evidence suggested that diabetic patients treated with metformin have lower PCa risk and better prognosis. This study was aimed to investigate the effects of metformin on EMT in PCa cells and the possible microRNA (miRNA)-based mechanisms. MiRNAs have been shown to regulate various processes of cancer metastasis. We herein showed that metformin significantly inhibits proliferation of Vcap and PC-3 cells, induces G0/G1 cell cycle arrest and inhibits invasiveness and motility capacity of Vcap cells. Metformin could inhibit TGF-β-induced EMT in Vcap cells, as manifested by inhibition of the increase of N-cadherin (p=0.013), Vimentin (p=0.002) and the decrease of E-cadherin (p=0.0023) and β-catenin (p=0.034) at mRNA and protein levels. Notably, we demonstrated significant upregulation of miR30a levels by metformin (P<0.05) and further experiments indicated that miR30a significantly inhibits proliferation and EMT process of Vcap cells. Interestingly, we identified that SOX4, a previously reported oncogenic transcriptional factor and modulator of EMT, is a direct target gene of miR30a. Finally, we screened the expression of miR30a and SOX4 in 84 PCa cases with radical prostatectomy. Of note, SOX4 overexpression is significantly associated with decreased levels of miR30a in PCa cases. In all, our study suggested that inhibition of EMT by metformin in PCa cells may involve upregulation of miR30a and downregulation of SOX4.

ERG–SOX4 interaction promotes epithelial–mesenchymal transition in prostate cancer cells

Approximately 50% of prostate cancer (PCa) patients in Western countries harbor ERG rearrangement with concurrent ERG overexpression. Overexpression of SOX4 has been shown to play important roles in multiple cancers including PCa. However, the link between these two critical genetic aberrations was unclear.

Association of SOX4 regulated by tumor suppressor miR-30a with poor prognosis in low-grade chondrosarcoma

The sex-determining region Y-box 4 (SOX4), a transcription factor, is involved in various developmental processes. It has been reported in multiple human cancers. However, the prognostic value and its exact role in chondrosarcoma remain poorly understood. In the current study, SOX4 was overexpressed in 28 of 92 (30.4xa0%) interpretable chondrosarcoma patients compared with 3 of 43 (6.9xa0%) interpretable chondroma cases (Pu2009=u20090.003). Its overexpression in chondrosarcoma was significantly associated with histological grade (Pu2009<u20090.001) and the presence of tumor recurrence (Pu2009=u20090.041). In addition, SOX4 overexpression was notably correlated with c-MYC (Pu2009=u20090.011) and P53 (Pu2009=u20090.029) expression as well as high Ki67 labeling index (LI) (Pu2009<u20090.001) in our cohort. More importantly, we found that SOX4 was an unfavorable independent prognostic factor for chondrosarcoma patients with low histological grade. Functionally, SOX4 silencing significantly suppressed the proliferation, migratory, and invasive capacity of SW1353 cells, suggesting an oncogenic role of SOX4 in chondrosarcoma in vitro. In an attempt of characterizing SOX4 overexpression mechanism, we identified miR-30a as a tumor suppressor that directly targets SOX4 in chondrosarcoma cells. Clinically, miR-30a expression was negatively correlated with SOX4 expression in chondrosarcoma cases. In all, we identified that SOX4 was oncogenic in chondrosarcoma and negatively regulated by miR-30a in vitro. Importantly, SOX4 overexpression may serve as a prognostic marker for patients with low-histological-grade chondrosarcoma.

MiR-573 inhibits prostate cancer metastasis by regulating epithelial-mesenchymal transition.

The metastastic cascade is a complex process that is regulated at multiple levels in prostate cancer (PCa). Recent evidence suggests that microRNAs (miRNAs) are involved in PCa metastasis and hold great promise as therapeutic targets. In this study, we found that miR-573 expression is significantly lower in metastatic tissues than matched primary PCa. Its downregulation is correlated with high Gleason score and cancer-related mortality of PCa patients (P = 0.041, Kaplan-Meier analysis). Through gain- and loss-of function experiments, we demonstrated that miR-573 inhibits PCa cell migration, invasion and TGF-β1-induced epithelial-mesenchymal transition (EMT) in vitro and lung metastasis in vivo. Mechanistically, miR573 directly targets the fibroblast growth factor receptor 1 (FGFR1) gene. Knockdown of FGFR1 phenocopies the effects of miR-573 expression on PCa cell invasion, whereas overexpression of FGFR1 partially attenuates the functions of miR-573. Consequently, miR-573 modulates the activation of FGFR1-downstream signaling in response to fibroblast growth factor 2 (FGF2). Importantly, we showed that GATA3 directly increases miR-573 expression, and thus down-regulates FGFR1 expression, EMT and invasion of PCa cells in a miR-573-dependent manner, supporting the involvement of GATA3, miR-573 and FGFR1 in controlling the EMT process during PCa metastasis. Altogether, our findings demonstrate a novel mechanism by which miR-573 modulates EMT and metastasis of PCa cells, and suggest miR-573 as a potential biomarker and/or therapeutic target for PCa management.

Characterization of EGFR family gene aberrations in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly lethal malignancy of the biliary tract with very few treatment options. Epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor (HER2) have been considered as potential therapeutic targets in CCA. In the present study, we attempted to clarify the clinicopathological significance of all EGFR family members, EGFR, HER2, HER3 and HER4, across the full spectrum of CCAs. Immunohistochemistry and FISH were performed to validate expressions and genetic aberrations of these molecules retrospectively in 175 CCA patients. EGFR, HER3 and HER4 were overexpressed in 20 (30.8%), 8 (12.3%) and 41 (63.1%) of the 65 intrahepatic cholangiocarcinomas (IHCCs), and in 23 (20.9%), 13 (11.8%) and 62 (56.4%) of the 110 extrahepatic cholangiocarcinomas (EHCCs), respectively. Overexpression of HER2 was exclusively identified in EHCCs, among which the rate was 4.5% (5/110). A significant association was identified between EGFR amplification and EGFR overexpression (P=0.002). Similarly, HER2 amplification was strongly associated with HER2 overexpression (P<0.001). Multivariate analysis suggested that EGFR overexpression is an independent prognostic factor in IHCC, but not in EHCC cases [HR (95% CI): 3.689 (1.253-10.587), P=0.018]. Notably, for the first time, we demonstrated HER4 expression is a prognostic factor in EGFR-negative IHCC patients. In vitro data further suggested a tumor-suppressor role of HER4 in CCA. siRNA knockdown of HER4 significantly increased RBE cell migration and invasion. By contrast, HER4 overexpression decreased proliferation of HuCCT-1 cells and their migratory and invasive capacity. In summary, our results revealed expression of the EGFR family members in CCA development and progression. CCAs differentially express HER2 protein based on tumor location. HER4 expression status allows stratification of CCA patients into different survival categories.

MicroRNA-132/212 Upregulation Inhibits TGF-β-Mediated Epithelial–Mesenchymal Transition of Prostate Cancer Cells by Targeting SOX4

MicroRNAs (miRNAs) are noncoding RNAs that are important for embryonic stem cell development and epithelial to mesenchymal transition (EMT). Accumulating evidence indicates that miRNAs play critical roles in prostate cancer (PCa) metastasis and have potential use as therapeutic targets. Although dysregulated miR‐132/212 have been suggested to be directly involved in the proliferation and invasion of multiple malignancies, the exact role of miR‐132/212 in PCa has not yet been fully understood.

The role of TXNDC5 in castration-resistant prostate cancer-involvement of androgen receptor signaling pathway.

Castration-resistant prostate cancer (CRPC) continues to be a major clinical problem and the mechanisms behind it remain unclear. Thioredoxin domain-containing protein 5 (TXNDC5) is involved in protein folding and chaperone activity, and its overexpression has been reported in multiple malignancies. In the current study, we demonstrated that TXNDC5 is up-regulated following long-term androgen-deprivation treatment (ADT) and is highly overexpressed in CRPC tumors compared with hormone-naive prostate cancer (PCa) cases. Functionally, in vitro and in vivo studies demonstrated that TXNDC5 overexpression promotes the growth of both androgen-dependent and castration-resistant PCa xenografts. Mechanistically, TXNDC5 directly interacts with the AR protein to increase its stability and thus enhances its transcriptional activity. TXDNC5-mediated CRPC growth can be fully abolished by AR inhibition, suggesting TXDNC5 up-regulation as an escape pathway for aberrant AR re-activation and CRPC growth in the milieu of low androgen. Indeed, we found that TXNDC5 is increased by ADT-induced hypoxia through HIF-1α in an miR-200b-dependent manner. Overall, we defined an important role of TXNDC5 in CRPC and further investigations are needed to screen TXNDC5 antagonists as a novel therapeutic approaches to treat PCa patients with CRPC.

Morphologic features of carcinomas with recurrent gene fusions.

Recurrent gene fusions have been thought to play a central role in leukemias, lymphomas, and sarcomas, but they have been neglected in carcinomas, largely because of technical limitations of cytogenetics. In the past few years, an increasing number of recurrent gene fusions have been recognized in epithelial cancers. The majority of prostate cancers, for example, have an androgen-regulated fusion of one of the ETS transcription factor gene family. Notably, the fusion genes can often serve as specific diagnostic markers, criteria of molecular classification and therefore potential therapeutic targets. Recent studies have focused on investigations of morphologic features (phenotype) of recurrent gene fusions (genotype) in malignancies. In this review, we will summarize the histologic features of known recurrent genomic rearrangements in carcinomas, especially focusing on TMPRSS2-ERG fusion in prostate cancer, EML4-ALK in lung cancer, ETV6-NTRK3 in secretory breast cancer, RET/PTC and PAX8/PPAR&ggr;1 rearrangements in thyroid cancer. In addition, we will describe how these features could potentially be used to alert the pathologists of the diagnosis of fusion-positive tumor. A combination of histologic validation with other screening strategies (eg, immunohistochemistry) for recognition of recurrent gene fusions is also highlighted.

Adiponectin as a potential tumor suppressor inhibiting epithelial-to-mesenchymal transition but frequently silenced in prostate cancer by promoter methylation.

Recent evidence suggests a particular role for obesity in prostate cancer (PCa) progression. Adiponectin (ADN) is a hormone secreted by adipose tissue and has a variety of functions including the inhibition of PCa cell proliferation. Although serum ADN levels have been identified to be related with carcinogenesis in a tissue‐specific context, the exact role of endogenous ADN in PCa cells remains largely unknown.

Overexpression of ETV4 is associated with poor prognosis in prostate cancer: involvement of uPA/uPAR and MMPs

ETS gene fusions involving ERG, ETV1, ETV4, ETV5, and FLI1 define a distinct class of prostate cancer (PCa), and this might have a bearing on diagnosis, prognosis, and rational therapeutic targeting. In the current study, we focused on the clinicopathological significance of ETV4 in Chinese PCa patients and the mechanisms whereby ETV4 overexpression mediates tumor invasion in the prostate. Overall, ETV4 overexpression was identified in 30.4xa0% (45/148) of PCa cases by immunohistochemistry. Accordingly, ETV4 was rearranged in only 1.6xa0% (2/128) of PCa patients. Clinically, ETV4 overexpression was significantly correlated with Gleason score (Pu2009=u20090.045) and pathological tumor stage (Pu2009=u20090.041). Multivariate Cox regression analysis indicated that ETV4 is an unfavorable independent prognostic factor (Pu2009=u20090.040). Functional studies further showed that small interfering RNA (siRNA) knockdown of ETV4 significantly decreases proliferation and invasion of PC-3 cell and partially reverses epithelial-mesenchymal transition in vitro. Notably, ETV4 knockdown significantly downregulated expression of urokinase plasminogen activator (uPA) and its receptor (uPAR) at messenger RNA (mRNA) and protein levels. Chromatin immunoprecipitation assay demonstrated that ETV4 regulates uPA expression through direct binding to its promoter region. Additionally, ETV4 knockdown was also observed to significantly inhibit expression of matrix metalloproteinase (MMP)-2 and MMP-9. In conclusion, for the first time, our study suggested that ETV4 is an independent poor prognostic factor in Chinese PCa patients. Silencing of ETV4 suppresses invasion of PCa cells by inhibiting the expression of uPA/uPAR as well as MMPs. Further studies will be needed to determine whether ETV4 could be regarded as a potential target for the management and prevention of PCa.