黒住 顕

OBJECTIVES: To determine candidates for extended pelvic lymph node dissection using a novel nomogram to assess the risk of lymph node invasion in Japanese prostate cancer patients in the robotic era. METHODS: A total of 538 patients who underwent robot-assisted radical prostatectomy with extended pelvic lymph node dissection in three hospitals were retrospectively analyzed. Medical records were reviewed uniformly and the following data collected: prostate-specific antigen, age, clinical T stage, primary and secondary Gleason score at prostate biopsy, and percentage of positive core numbers. Finally, data from 434 patients were used for developing the nomogram and data from 104 patients were used for external validation. RESULTS: Lymph node invasion was detected in 47 (11%) and 16 (15%) patients in the development and validation set, respectively. Based on multivariate analysis, prostate-specific antigen, clinical T stage ≥3, primary Gleason score, grade group 5, and percentage of positive cores were selected as variables to incorporate into the nomogram. The area under the curve values were 0.781 for the internal and 0.908 for the external validation, respectively. CONCLUSIONS: The present nomogram can help urologists identify candidates for extended pelvic lymph node dissection concomitant with robot-assisted radical prostatectomy among patients with prostate cancer.

Androgen receptor (AR) transcriptional activity contributes to prostate cancer development and castration resistance. The growth and survival pathways driven by AR remain incompletely defined. Here, we found PDCD4 to be a new target of AR signaling and a potent regulator of prostate cancer cell growth, survival, and castration resistance. The 3' untranslated region of PDCD4 is directly targeted by the androgen-induced miRNA, miR-21. Androgen treatment suppressed PDCD4 expression in a dose responsive and miR-21-dependent manner. Correspondingly, AR inhibition dose-responsively induced PDCD4 expression. Using data from prostate cancer tissue samples in The Cancer Genome Atlas (TCGA), we found a significant and inverse correlation between miR-21 and PDCD4 mRNA and protein levels. Higher Gleason grade tumors exhibited significantly higher levels of miR-21 and significantly lower levels of PDCD4 mRNA and protein. PDCD4 knockdown enhanced androgen-dependent cell proliferation and cell-cycle progression, inhibited apoptosis, and was sufficient to drive androgen-independent growth. On the other hand, PDCD4 overexpression inhibited miR-21-mediated growth and androgen independence. The stable knockdown of PDCD4 in androgen-dependent prostate cancer cells enhanced subcutaneous tumor take rate in vivo, accelerated tumor growth, and was sufficient for castration-resistant tumor growth. IMPLICATIONS: This study provides the first evidence that PDCD4 is an androgen-suppressed protein capable of regulating prostate cancer cell proliferation, apoptosis, and castration resistance. These results uncover miR-21 and PDCD4-regulated pathways as potential new targets for castration-resistant prostate cancer.

Interstitial cystitis (IC), also known as bladder pain syndrome, is a chronic inflammatory disease that affects the bladder. The symptoms of IC vary, including feeling an urgent need for immediate urination and of needing to urinate often, as well as bladder or pelvic pain. Despite its high incidence, no molecular diagnostic methods are available for IC, and the molecular pathogenesis is unknown. microRNAs (miRNA) can regulate expression of RNA transcripts in cells and aberrant expression of miRNAs is associated with several human diseases. Here, we investigated the molecular pathogenesis of IC based on miRNA expression signatures. RNA sequencing of miRNA levels in IC tissues and comparison with levels in normal bladder tissue and bladder cancer revealed dysregulated expression of 366 miRNAs (203 and 163 down- and upregulated miRNAs, respectively). In particular, miR-320 family miRNAs(miR-320a, miR-320b, miR-320c, miR-320d and miR-320e) had downregulated expression in IC tissues. Genome-wide gene expression analyses and in silico database analyses showed that three transcription factors, E2F-1, E2F-2 and TUB, are regulated by miR-320 family miRNAs. Immunostaining of IC tissues confirmed that these transcription factors are overexpressed in IC tissues. Novel approaches that identify aberrantly expressed miRNA regulatory networks in IC could provide new prognostic markers and therapeutic targets for this disease.

Effective treatments for patients with castration-resistant prostate cancer (CRPC) have not yet been established. Novel approaches for identification of putative therapeutic targets for CRPC are needed. Analyses of RNA sequencing of microRNA (miRNA) expression revealed that miR-99a-3p (passenger strand) is significantly downregulated in several types of cancers. Here, we aimed to identify novel miR-99a-3p regulatory networks and therapeutic targets for CRPC. Ectopic expression of miR-99a-3p significantly inhibited cancer cell proliferation, migration, and invasion in PCa cells. Non-SMC condensin I complex subunit G (NCAPG) was a direct target of miR-99a-3p in PCa cells. Overexpression of NCAPG was detected in CRPC clinical specimens and was significantly associated with shorter disease-free survival and advanced clinical stage. Knockdown of NCAPG inhibited cancer cell aggressiveness. The passenger strand miR-99a-3p acted as an antitumor miRNA in naïve PCa and CRPC. NCAPG was regulated by miR-99a-3p, and its overexpression was involved in CRPC pathogenesis. Involvement of passenger strand of miRNA in cancer pathogenesis is novel concept, and identification of antitumor miRNA regulatory networks in CRPC might be provided novel prognostic markers and therapeutic targets for this disease.

Analysis of our original microRNA (miRNA) expression signature of patients with advanced renal cell carcinoma (RCC) showed that microRNA-10a-5p (miR-10a-5p) was significantly downregulated in RCC specimens. The aims of the present study were to investigate the antitumor roles of miR-10a-5p and the novel cancer networks regulated by this miRNA in RCC cells. Downregulation of miR-10a-5p was confirmed in RCC tissues and RCC tissues from patients treated with tyrosine kinase inhibitors (TKI). Ectopic expression of miR-10a-5p in RCC cell lines (786-O and A498 cells) inhibited cancer cell migration and invasion. Spindle and kinetochore-associated protein 1 (SKA1) was identified as an antitumor miR-10a-5p target by genome-based approaches, and direct regulation was validated by luciferase reporter assays. Knockdown of SKA1 inhibited cancer cell migration and invasion in RCC cells. Overexpression of SKA1 was observed in RCC tissues and TKI-treated RCC tissues. Moreover, analysis of The Cancer Genome Atlas database demonstrated that low expression of miR-10a-5p and high expression of SKA1 were significantly associated with overall survival in patients with RCC. These findings showed that downregulation of miR-10a-5p and overexpression of the SKA1 axis were highly involved in RCC pathogenesis and resistance to TKI treatment in RCC.

Our recent studies revealed that dual strands of certain pre-microRNAs, e.g., pre-miR-144, pre-miR-145, and pre-miR-150, act as antitumor microRNAs (miRNAs) in several cancers. The involvement of passenger strands of miRNAs in cancer pathogenesis is a novel concept in miRNA research. The analysis of a miRNA expression signature in clear cell renal cell carcinoma (ccRCC) has revealed that the guide strand of pre-miR-149 is significantly downregulated in cancer tissues. The aims of this study were to investigate the functional significance of miR-149's guide strand (miR-149-5p) and passenger strand (miR-149-3p), and to identify the oncogenic genes regulated by these miRNAs in ccRCC cells. The ectopic expression of these miRNAs significantly inhibited cancer cell migration and invasion in ccRCC cells. Forkhead box protein M1 (FOXM1) was directly regulated by miR-149-5p and miR-149-3p in ccRCC cells. Knockdown studies using si-FOXM1 showed that the expression of FOXM1 enhanced RCC cell aggressiveness. Interestingly, the analysis of a large number of patients in the The Cancer Genome Atlas (TCGA) database (n = 260) demonstrated that patients with high FOXM1 expression had significantly shorter survival than did those with low FOXM1 expression (p = 1.5 × 10⁻⁶). Taken together, dual strands of pre-miR-149 (miR-149-5p and miR-149-3p) acted as antitumor miRNAs through the targeting of FOXM1 in ccRCC cells.

For patients with head and neck squamous cell carcinoma (HNSCC), survival rates have not improved due to local recurrence and distant metastasis. Current targeted molecular therapies do not substantially benefit HNSCC patients. Therefore, it is necessary to use advanced genomic approaches to elucidate the molecular mechanisms underlying the aggressiveness of HNSCC cells. Analysis of our microRNA (miRNA) expression signature by RNA sequencing showed that the miR-199 family (miR-199a-5p, miR-199a-3p, miR-199b-5p and miR-199b-3p) was significantly reduced in cancer tissues. Ectopic expression of mature miRNA demonstrated that all members of the miR-199 family inhibited cancer cell migration and invasion by HNSCC cell lines (SAS and HSC3). These findings suggested that both passenger strands and guide strands of miRNA are involved in cancer pathogenesis. In silico database and genome-wide gene expression analyses revealed that the gene coding for integrin α3 (ITGA3) was regulated by all members of the miR-199 family in HNSCC cells. Knockdown of ITGA3 significantly inhibited cancer cell migration and invasion by HNSCC cells. Moreover, overexpression of ITGA3 was confirmed in HNSCC specimens, and high expression of ITGA3 predicted poorer survival of the patients (P = 0.0048). Our data revealed that both strands of pre-miR-199a (miR-199a-5p and miR-199a-3p) and pre-miR-199b (miR-199b-5p and miR-199b-3p) acted as anti-tumor miRNA in HNSCC cells. Importantly, the involvement of passenger strand miRNA in the regulation of cellular processes is a novel concept in RNA research. Novel miRNA-based approaches for HNSCC can be used to identify potential targets for the development of new therapeutic strategies.

BACKGROUND: Despite recent advancements, metastatic castration-resistant prostate cancer (CRPC) is not considered curative. Novel approaches for identification of therapeutic targets of CRPC are needed. METHODS: Next-generation sequencing revealed 945-1248 miRNAs from each lethal mCRPC sample. We constructed miRNA expression signatures of CRPC by comparing the expression of miRNAs between CRPC and normal prostate tissue or hormone-sensitive prostate cancer (HSPC). Genome-wide gene expression studies and in silico analyses were carried out to predict miRNA regulation and investigate the functional significance and clinical utility of the novel oncogenic pathways regulated by these miRNAs in prostate cancer (PCa). RESULTS: Based on the novel miRNA expression signature of CRPC, miR-145-5p and miR-145-3p were downregulated in CRPC. By focusing on miR-145-3p, which is a passenger strand and has not been well studied in previous reports, we showed that miR-145-3p targeted 4 key molecules, i.e., MELK, NCAPG, BUB1, and CDK1, in CPRC. These 4 genes significantly predicted survival in patients with PCa. CONCLUSIONS: Small RNA sequencing for lethal CRPC and in silico analyses provided novel therapeutic targets for CRPC.

Analysis of our microRNA (miRNA) expression signature in human cancers has shown that guide and passenger strands of pre-miR‑150, i.e., miR‑150‑5p and miR‑150‑3p, are significantly downregulated in cancer tissues. In miRNA biogenesis, the passenger strand of miRNA is degraded and is thought to have no functions. Thus, the aim of this study was to investigate the functional significance of miR‑150‑5p and miR‑150‑3p in naïve prostate cancer (PCa) and castration-resistant prostate cancer (CRPC). Ectopic expression assays showed that both strands of miRNAs significantly suppressed cancer cell migration and invasion. Our strategies of miRNA target searching demonstrated that SPOCK1 (SPARC/osteonectin, cwcv and kazal like domains proteoglycan 1) was directly regulated by miR‑150‑5p and miR‑150‑3p. Knockdown of SPOCK1 by siRNA inhibited cancer cell aggressiveness. Moreover, overexpression of SPOCK1 was observed in naïve PCa and CRPC tissues. Taken together, dual strands of pre-miR‑150 (miR‑150‑5p and miR‑150‑3p) acted as antitumor miRNAs in naïve PCa and CRPC cells. Expression of oncogenic SPOCK1 was involved in naïve PCa and CRPC pathogenesis. Novel approaches to analysis of antitumor miRNA-regulated RNA networks in cancer cells may provide new insights into the pathogenic mechanisms of naïve PCa and CRPC.

The discovery of microRNAs (miRNAs) has resulted in major advancements in cancer research. miRNAs are small noncoding RNAs that function to fine tune the expression of protein coding/noncoding RNAs by repressing translation or cleaving RNA transcripts in a sequence-depending manner. The unique characteristic function of miRNAs is to regulate RNA transcripts in human cells. Therefore, dysregulated expression of miRNAs can disrupt tightly regulated RNA networks in cancer cells. miRNAs play critical roles in various biological processes, and their dysregulation has been observed in several human diseases, including cancers. Recent studies of cancer epigenome analysis have demonstrated that epigenetic mechanisms, including DNA methylation and histone modification, regulate the expression of a number of miRNAs, and conversely, these miRNAs control the expression of various epigenetic modulators, including DNA methyltransferases (DNMTs), histone deacetylases (HDACs), and polycomb group genes. When this complicated feedback loop between miRNAs and epigenetics is dysregulated by aberrant expression of miRNAs, normal physiological functions are disrupted, and as a result, several diseases occur, including cancer. That is, dysregulation of miRNAs can affect epigenetic alterations in cancer. The present review focuses on some tumor-suppressive miRNAs that have been shown to regulate epigenetic modulators in cancer the functional roles of these miRNAs in epigenetics are described. Elucidation of the relationship between miRNA dysregulation and epigenetic alterations will lead to the discovery of new therapeutic strategies for cancer.

Our recent studies of microRNA (miRNA) expression signatures of prostate cancer (PCa) showed that six miRNAs (specifically, miR-26a, miR-26b, miR-29a, miR-29b, miR-29c and miR-218) were markedly reduced in cancer tissues. Moreover, ectopic expression of these miRNAs suppressed PCa cell aggressiveness, indicating that these miRNAs acted in concert to regulate genes that promoted metastasis. Genome-wide gene expression analysis and in silico database analysis identified a total of 35 candidate genes that promoted metastasis and were targeted by these 6 miRNAs. Using luciferase reporter assays, we showed that the lysyl oxidase-like 2 (LOXL2) gene was directly controlled by these tumor-suppressive miRNAs in PCa cells. Overexpression of LOXL2 was confirmed in PCa tissues and knockdown of the LOXL2 gene markedly inhibited the migration and invasion of PCa cells. Aberrant expression of LOXL2 enhanced migration and invasion of PCa cells. Downregulation of antitumor miRNAs might disrupt the tightly controlled RNA networks found in normal cells. New insights into the novel molecular mechanisms of PCa pathogenesis was revealed by antitumor miRNA-regulated RNA networks.

Bladder cancer (BC) and renal cell carcinoma (RCC) are frequently diagnosed urinary tract cancers. Recently developed molecular-targeted therapies for RCC have shown remarkable therapeutic efficacy; however, no targeted therapeutics are currently approved for the treatment of BC, and few effective treatment options exist. Current studies have shown that small noncoding RNA molecules have major roles in cancer cells. MicroRNAs (miRNAs) are endogenous small noncoding RNA molecules that regulate protein-/nonprotein-coding RNAs in human cells. A large body of evidence suggests that aberrantly expressed miRNAs are deeply involved in the pathogenesis of human cancers. In this paper, we review recently published miRNA expression signatures of BC and RCC. We focus on downregulated or upregulated miRNAs in multiple signatures and discuss putative target genes of miRNAs. Comparisons of RCC and BC expression signatures revealed that the two types of cancer showed opposite expression patterns for miR-200 family miRNAs (i.e., miR-141/200c and miR-200a/200b/429). We discuss in silico analysis of genes targeted by miR-200 family miRNAs and the molecular mechanisms underlying BC and RCC.

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive malignancies. Recently developed molecular targeted therapies are not available for patients with ESCC. After curative surgical resection, patients frequently suffer distant metastasis and recurrence. Exploration of novel ESCC metastatic pathways may lead to the development of new treatment protocols for this disease. Accordingly, we have sequentially identified microRNA (miRNA)-mediated metastatic pathways in several cancers. Our past studies of miRNA expression signatures have shown that microRNA-375 (miR-375) is frequently reduced in several types of cancers, including ESCC. In the present study, we aimed to investigate novel miR-375-mediated metastatic pathways in ESCC cells. The expression of miR-375 was downregulated in ESCC tissues, and ectopic expression of this miRNA markedly inhibited cancer cell migration and invasion, suggesting that miR-375 acted as an antimetastatic miRNA in ESCC cells. Our strategies for miRNA target searching demonstrated that matrix metalloproteinase 13 (MMP13) was directly regulated by miR-375 in ESCC cells. Overexpression of MMP13 was observed in ESCC clinical tissues, and the expression of MMP13 promoted cancer cell aggressiveness. Moreover, oncogenic genes, including CENPF, KIF14 and TOP2A, were shown to be regulated downstream of MMP13. Taken together, these findings demonstrated that the antitumor miR-375/oncogenic MMP13 axis had a pivotal role in ESCC aggressiveness. These results provide novel insights into the potential mechanisms of ESCC pathogenesis.

Molecular targeted therapy is a standard treatment for patients with advanced renal cell carcinoma (RCC). Sunitinib is one of the most common molecular-targeted drugs for metastatic RCC. Molecular mechanisms of sunitinib resistance in RCC cells is still ambiguous. The microRNA (miRNA) expression signature of patients with sunitinib failure in RCC was constructed using a polymerase chain reaction (PCR)-based array. Several miRNAs that were aberrantly expressed in RCC tissues from patients treated with sunitinib were identified in this analysis. MicroRNA-101 (miR- 101) was markedly suppressed in sunitinib treated RCC tissues. Restoration of miR-101 significantly inhibited cell migration and invasion in Caki-1 and 786-O cells. Ubiquitin-like with PHD and ring finger domains 1 (UHRF1) was directly suppressed by miR-101 in RCC cells, and overexpression of UHRF1 was confirmed in sunitinib-treated RCC tissues. The pathways of nucleotide excision repair and mismatch repair were significantly suppressed by knockdown of UHRF1. Our findings showed that antitumor miR-101- mediated UHRF1 pathways may be suppressed by sunitinib treatment.

Our recent studies of microRNA (miRNA) expression signatures in human cancers revealed that two clustered miRNAs, microRNA-23b (miR-23b) and microRNA-27b (miR‑27b), were significantly reduced in cancer tissues. Few reports have provided functional analyses of these clustered miRNAs in oral squamous cell carcinoma (OSCC). The aim of this study was to investigate the functional significance of miR-23b and miR-27b in OSCC and to identify novel miR-23b/27b-mediated cancer pathways and target genes involved in OSCC oncogenesis and metastasis. Expression levels of miR-23b and miR-27b were significantly reduced in OSCC specimens. Restoration of miR-23b or miR-27b in cancer cells revealed that both miRNAs significantly inhibited cancer cell migration and invasion. Our in silico analyses and luciferase reporter assays showed that the receptor tyrosine kinase MET, was directly regulated by these miRNAs. Moreover, downregulating the MET gene by use of siRNA significantly inhibited cell migration and invasion by OSCC cells. The identification of novel molecular pathways regulated by miR-23b and miR-27b may lead to a better understanding of the oncogenesis and metastasis of this disease.

Advanced prostate cancer (PCa) metastasizes to bone and lymph nodes, and currently available treatments cannot prevent the progression and metastasis of the disease. Therefore, an improved understanding of the molecular mechanisms of the progression and metastasis of advanced PCa using current genomic approaches is needed. Our miRNA expression signature in castration-resistant prostate cancer (CRPC) revealed that microRNA-320a (miR‑320a) was significantly reduced in cancer tissues, suggesting that miR‑320a may be a promising anticancer miRNA. The aim of this study was to investigate the functional roles of miR‑320a in naïve PCa and CRPC cells and to identify miR‑320a-regulated genes involved in PCa metastasis. The expression levels of miR‑320a were significantly reduced in naïve PCa, CRPC specimens, and PCa cell lines. Restoration of mature miR‑320a in PCa cell lines showed that miR‑320a significantly inhibited cancer cell migration and invasion. Moreover, we found that lysosomal-associated membrane protein 1 (LAMP1) was a direct target of miR‑320a in PCa cells. Silencing of LAMP1 using siRNA significantly inhibited cell proliferation, migration, and invasion in PCa cells. Overexpression of LAMP1 was observed in PCa and CRPC clinical specimens. Moreover, downstream pathways were identified using si-LAMP1-transfected cells. The discovery of tumor-suppressive miR‑320a-mediated pathways may provide important insights into the potential mechanisms of PCa metastasis.

BACKGROUND: MicroRNA-224 (miR-224) and microRNA-452 (miR-452) are closely located on the human chromosome Xq28 region. miR-224 functions as a tumour suppressor by targeting tumour protein D52 (TPD52) in prostate cancer (PCa). Here, we aimed to investigate the functional significance of miR-452 in PCa cells. METHODS: Functional studies of PCa cells were performed using transfection with mature miRNAs or siRNAs. Genome-wide gene expression analysis, in silico analysis, and dual-luciferase reporter assays were applied to identify miRNA targets. The association between miR-452 levels and overall patient survival was estimated by the Kaplan-Meier method. RESULTS: Expression of miR-452 was significantly downregulated in PCa tissues. Transfection with mature miR-452 inhibited the migration and invasion of PCa cells. Kaplan-Meier survival curves showed that low expression of miR-452 predicted a short duration of progression to castration-resistant PCa. WW domain-containing E3 ubiquitin protein ligase-1 (WWP1) was a direct target of miR-452, and knockdown of WWP1 inhibited the migration and invasion of PCa cells. WWP1 was upregulated in PCa clinical specimens. CONCLUSIONS: Regulation of the miR-452-WWP1 axis contributed to PCa cell migration and invasion, and elucidation of downstream signalling of this axis will provide new insights into the mechanisms of PCa oncogenesis and metastasis.

Our recent studies of microRNA (miRNA) expression signatures in human cancers revealed that microRNA-26a (miRNA-26a) and microRNA-26b (miRNA-26b) were significantly reduced in cancer tissues. To date, few reports have provided functional analyses of miR-26a or miR-26b in renal cell carcinoma (RCC). The aim of the present study was to investigate the functional significance of miR-26a and miR-26b in RCC and to identify novel miR-26a/b-mediated cancer pathways and target genes involved in RCC oncogenesis and metastasis. Downregulation of miR-26a or miR-26b was confirmed in RCC clinical specimens. Restoration of miR-26a or miR-26b in RCC cell lines (786-O and A498) revealed that these miRNAs significantly inhibited cancer cell migration and invasion. Our in silico analysis and luciferase reporter assays showed that lysyl oxidase-like 2 (LOXL2) and procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2) were directly regulated by these miRNAs. Moreover, downregulating the PLOD2 gene significantly inhibited cell migration and invasion in RCC cells. Thus, our data showed that two genes promoting metastasis, LOXL2 and PLOD2, were epigenetically regulated by tumor-suppressive microRNAs, miR-26a and miR-26b, providing important insights into the molecular mechanisms of RCC metastasis.

In spite of considerable advances in multimodality therapy, including surgery, radiotherapy and chemotherapy, the overall survival rate for patients with head and neck squamous cell carcinoma (HNSCC) is very poor (only 15-45%). Understanding the molecular mechanisms of metastatic pathways underlying HNSCC using currently available genomic approaches might improve therapies for and prevention of the disease. Our previous studies showed that three tumor-suppressive microRNAs (miRNAs), miR-26a/b, miR-29a/b/c and miR-218, significantly inhibited cancer cell migration and invasion. Therefore, we hypothesized that these miRNAs-regulated target genes deeply contributed to cancer metastasis. These tumor-suppressive miRNAs directly regulate LOXL2 expression in HNSCC cells by using in silico analysis and luciferase reporter assays. Overexpressed LOXL2 was confirmed in HNSCC clinical specimens, and silencing of LOXL2 inhibited cancer cell migration and invasion in HNSCC cell lines. Our present data showed that tumor-suppressive miRNAs regulation of LOXL2 will provide new insights into the novel molecular mechanisms of HNSCC metastasis.

Analysis of microRNA (miRNA) expression signatures in prostate cancer (PCa) and castration-resistant PCa has revealed that miRNA-223 is significantly downregulated in cancer tissues, suggesting that miR-223 acts as a tumor-suppressive miRNA by targeting oncogenes. The aim of this study was to investigate the functional roles of miR-223 and identify downstream oncogenic targets regulated by miR-223 in PCa cells. Functional studies of miR-223 were carried out to investigate cell proliferation, migration, and invasion using PC3 and PC3M PCa cell lines. Restoration of miR-223 significantly inhibited cancer cell migration and invasion in PCa cells. In silico database and genome-wide gene expression analyses revealed that ITGA3 and ITGB1 were direct targets of miR-223 regulation. Knockdown of ITGA3 and ITGB1 significantly inhibited cancer cell migration and invasion in PCa cells by regulating downstream signaling. Moreover, overexpression of ITGA3 and ITGB1 was observed in PCa clinical specimens. Thus, our data indicated that downregulation of miR-223 enhanced ITGA3/ITGB1 signaling and contributed to cancer cell migration and invasion in PCa cells. Elucidation of the molecular pathways modulated by tumor-suppressive miRNAs provides insights into the mechanisms of PCa progression and metastasis.

BACKGROUND: Our present study of the microRNA (miRNA) expression signature in castration-resistant prostate cancer (CRPC) revealed that the clustered miRNAs microRNA-221 (miR-221) and microRNA-222 (miR-222) are significantly downregulated in cancer tissues. The aim of this study was to investigate the functional roles of miR-221 and miR-222 in prostate cancer (PCa) cells. METHODS: A CRPC miRNA signature was constructed by PCR-based array methods. Functional studies of differentially expressed miRNAs were analysed using PCa cells. The association between miRNA expression and overall survival was estimated by the Kaplan-Meier method. In silico database and genome-wide gene expression analyses were performed to identify molecular targets regulated by the miR-221/222 cluster. RESULTS: miR-221 and miR-222 were significantly downregulated in PCa and CRPC specimens. Kaplan-Meier survival curves showed that low expression of miR-222 predicted a short duration of progression to CRPC. Restoration of miR-221 or miR-222 in cancer cells revealed that both miRNAs significantly inhibited cancer cell migration and invasion. Ecm29 was directly regulated by the miR-221/222 cluster in PCa cells. CONCLUSIONS: Loss of the tumour-suppressive miR-221/222 cluster enhanced migration and invasion in PCa cells. Our data describing targets regulated by the tumour-suppressive miR-221/222 cluster provide insights into the mechanisms of PCa and CRPC progression.

OBJECTIVES: To investigate the functional roles of microRNA-205 in the modulation of novel cancer pathways in prostate cancer cells. METHODS: Functional studies of microRNA-205 were carried out to investigate cell proliferation, migration and invasion in prostate cancer cell lines (PC3 and DU145) by restoration of mature microRNA. In silico database and genome-wide gene expression analyses were carried out to identify molecular targets and pathways mediated by microRNA-205. Loss-of-function studies were applied to microRNA-205 target genes. RESULTS: Restoration of microRNA-205 in cancer cell lines significantly inhibited cancer cell migration and invasion. Our data showed that the centromere protein F gene was overexpressed in prostate cancer clinical specimens and was a direct target of microRNA-205 regulation. Silencing of centromere protein F significantly inhibited cancer cell migration and invasion. Furthermore, MCM7, an oncogenic gene functioning downstream of centromere protein F, was identified by si-centromere protein F transfectants in prostate cancer cells. CONCLUSIONS: Loss of tumor-suppressive microRNA-205 seems to enhance cancer cell migration and invasion in prostate cancer through direct regulation of centromere protein F. Our data describing pathways regulated by tumor-suppressive microRNA-205 provide new insights into the potential mechanisms of prostate cancer oncogenesis and metastasis.

Our past studies of microRNA (miRNA) expression signatures of cancers including prostate cancer (PCa) revealed that microRNA-26a and microRNA-26b (miR-26a and miR-26b) were significantly downregulated in cancer tissues. In the present study, we found that restoration of miR-26a or miR-26b significantly inhibited PCa cell invasion. Gene expression data and in silico analysis showed that the gene encoding La-related protein 1 (LARP1) was a putative candidate of miR-26a and miR-26b regulation. Moreover, luciferase reporter assays revealed that LARP1 was a direct target of both miR-26a and miR-26b. Overexpression of LARP1 was observed in PCa clinical specimens and knockdown of LARP1 inhibited cancer cell migration. Therefore, LARP1 acted as an oncogene in PCa cells. Moreover, 'ribosome', 'RNA transport' and 'mTOR signaling pathway' were identified as LARP1-regulated pathways. Our present data suggested that loss of tumor-suppressive miR-26a and miR-26b enhanced cancer cell invasion in PCa through direct regulation of oncogenic LARP1. Elucidation of the molecular networks regulated by tumor-suppressive miRNAs will provide insights into the molecular mechanisms of PCa oncogenesis and metastasis.

microRNAs, a class of small non-coding RNAs, regulate protein-coding gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. A growing body of evidence suggests that microRNAs contribute to prostate cancer development, progression and metastasis. Based on reports describing microRNA expression signatures, several differentially expressed microRNAs have been discovered. In the present review, eight genome-wide microRNA expression signatures were used to select aberrantly expressed microRNAs (i.e. upregulated and downregulated microRNAs) in prostate cancer clinical specimens. Also, we mapped these selected microRNAs in the human genome. Interestingly, some clustered microRNAs, such as miR-221/222, miR-143/145, miR-23b/27b/24-1 and miR-1/133a, are frequently downregulated in cancer tissues, and recent studies have shown that these clustered microRNAs function as tumor suppressors. We also discuss the functional significance of the differentially expressed microRNAs and the molecular pathways/targets regulated by these microRNAs. These recent findings of microRNAs in prostate cancer will facilitate the development of effective strategies for microRNA-based therapeutics for the treatment of prostate cancer.