EphA6 promotes angiogenesis and prostate cancer metastasis and is associated with human prostate cancer progression

Metastasis is the primary cause of prostate cancer (CaP)-related death. We investigate the molecular, pathologic and clinical outcome associations of EphA6 expression and CaP metastasis. The expression profiling of Eph receptors (Ephs) and their ephrin ligands was performed in parental and metastatic CaP cell lines. Among Ephs and ephrins, only EphA6 is consistently overexpressed in metastatic CaP cells. Metastatic potential of EphA6 is assessed by RNAi in a CaP spontaneous metastasis mouse model. EphA6 knock-down in human PC-3M cells causes decreased invasion in vitro and reduced lung and lymph node metastasis in vivo. In addition, knock-down of EphA6 decreases tube formation in vitro and angiogenesis in vivo. EphA6 mRNA expression is higher in 112 CaP tumor samples compared with benign tissues from 58 benign prostate hyperplasia patients. Positive correlation was identified between EphA6 expression and vascular invasion, neural invasion, PSA level, and TNM staging in CaP cases. Further, genome-wide gene expression analysis in EphA6 knock-down cells identified a panel of differentially regulated genes including PIK3IPA, AKT1, and EIF5A2, which could contribute to EphA6-regulated cancer progression. These findings identify EphA6 as a potentially novel metastasis gene which positively correlates with CaP progression. EphA6 may be a therapeutic target in metastatic CaP.     

SPA-1 controls the invasion and metastasis of human prostate cancer

Recent studies suggest that SIPA1 encoding a Rap GTPase-activating protein SPA-1 is a candidate metastasis efficiency-modifying gene in human breast cancer. In this study, we investigated the expression and function of SPA-1 in human prostate cancer (CaP). Immunohistochemical studies of tumor specimens from CaP patients revealed a positive correlation of SPA-1 expression with disease progression and metastasis. The correlation was recapitulated in human CaP cell lines; LNCaP that rarely showed metastasis in SCID mice expressed an undetectable level of SPA-1, whereas highly metastatic PC3 showed abundant SPA-1 expression. Moreover, SIPA1 transduction in LNCaP caused prominent abdominal lymph node metastasis without affecting primary tumor size, whereas shRNA-mediated SIPA1 knockdown or expression of a dominant-active Rap1 mutant (Rap1V12) in PC3 suppressed metastasis. LNCaP transduced with SPA-1 (LNCaP/SPA-1) showed attenuated adhesion to the precoated extracellular matrices (ECM) including collagens and fibronectin, due to defective ECM-medicated Rap1 activation. In addition, LNCaP/SPA-1 showed a diminished level of nuclear Brd4, which is known to bind SPA-1, resulting in reduced expression of a series of ECM-related genes. These results suggest that SPA-1 plays an important role in controlling metastasis efficiency of human CaP by regulating the expression of and interaction with ECM in the primary sites.     

Snail is critical for tumor growth and metastasis of ovarian carcinoma

Snail, a key inducer of epithelial‐mesenchymal transition (EMT), plays an important role in cancer metastasis. To better understand the role of Snail in the metastasis of ovarian carcinoma, expression of Snail was knocked down by antisense‐Snail in the highly metastatic ovarian cancer cell line HO8910PM. Gene array analysis revealed that blocking Snail expression suppressed the activity of matrix metalloproteinases (MMPs) and upregulated TIMP3, an MMP inhibitor. These findings suggest that Snail interacts with MMP during tumor invasion and metastasis. In addition, we examined the role of Snail in an ovarian cancer orthotopic model by using the antisense‐Snail HO8910PM cell line. We found that the size of primary ovarian cancer tumor and the number of metastatic lesions were significantly reduced when Snail was knocked down. Confirming our initial findings, the activity of MMP2 was greatly inhibited in tumors from antisense‐Snail cells. Furthermore, immunohistochemical analysis on ovarian cancer progression tissue array demonstrated that the expression of Snail was significantly higher in metastatic lesions, and Snail expression correlated with the stage of ovarian cancer. Interestingly, in early‐stage tumors, Snail was localized in both the cytoplasm and nucleus. In late stage and metastatic lesions, the level of Snail was elevated, and Snail was localized to the nucleus. The expression level and nuclear localization of Snail were also inversely correlated with E‐cadherin expression. Overall, our study indicates that Snail plays a critical role in tumor growth and metastasis of ovarian carcinoma through regulation of MMP activity.     

RhoC GTPase is required for PC-3 prostate cancer cell invasion but not motility

It is projected that in 2005, approximately 220 900 men will be newly diagnosed with carcinoma of the prostate (CaP). Men who are diagnosed with locally advanced or metastatic disease undergo androgen ablation therapy and most will relapse and progress within 18 months. Metastasis to bone is the major clinical concern during CaP progression, as it is associated with intractable pain, bone fracture and paralysis resulting from spinal cord compression. Therefore, an understanding of the key mechanisms involved in CaP cell bone metastasis is vital to development of novel treatments. The Rho GTPases are molecular switches involved in cell survival, motility and invasion. Increased expression of RhoC GTPase is linked to enhanced metastatic potential in multiple cancers; however, the role of RhoC GTPase in CaP metastasis has not been addressed. In the current study, we demonstrate that RhoC GTPase is expressed and active in PC-3 CaP cells. RhoC inhibition, either pharmacologically with C3 exotransferase or molecularly through expression of a dominant-negative RhoC, promotes IGF-I stimulated random motility but decreases in vitro invasion and experimental metastases. Inhibition of RhoC activity results in drastic morphologic changes and alterations in the expression and distribution of focal adhesion-related proteins. These data suggest that RhoC inhibition leads to activation of other GTPases involved in nondirected motility and that expression of active RhoC is required for the invasive phenotype of PC-3 cells.     

Co-expression of CD147 (EMMPRIN), CD44v3-10, MDR1 and monocarboxylate transporters is associated with prostate cancer drug resistance and progression

Background:

The aim of this study is to seek an association between markers of metastatic potential, drug resistance-related protein and monocarboxylate transporters in prostate cancer (CaP).

Methods:

We evaluated the expression of invasive markers (CD147, CD44v3-10), drug-resistance protein (MDR1) and monocarboxylate transporters (MCT1 and MCT4) in CaP metastatic cell lines and CaP tissue microarrays (n=140) by immunostaining. The co-expression of CD147 and CD44v3-10 with that of MDR1, MCT1 and MCT4 in CaP cell lines was evaluated using confocal microscopy. The relationship between the expression of CD147 and CD44v3-10 and the sensitivity (IC₅₀) to docetaxel in CaP cell lines was assessed using MTT assay. The relationship between expression of CD44v3-10, MDR1 and MCT4 and various clinicopathological CaP progression parameters was examined.

Results:

CD147 and CD44v3-10 were co-expressed with MDR1, MCT1 and MCT4 in primary and metastatic CaP cells. Both CD147 and CD44v3-10 expression levels were inversely related to docetaxel sensitivity (IC₅₀) in metastatic CaP cell lines. Overexpression of CD44v3-10, MDR1 and MCT4 was found in most primary CaP tissues, and was significantly associated with CaP progression.

Conclusions:

Our results suggest that the overexpression of CD147, CD44v3-10, MDR1 and MCT4 is associated with CaP progression. Expression of both CD147 and CD44v3-10 is correlated with drug resistance during CaP metastasis and could be a useful potential therapeutic target in advanced disease.     

Association of susceptibility alleles in ELAC2/HPC2, RNASEL/HPC1, and MSR1 with prostate cancer severity in European American and African American men.

Reported associations of ELAC2/HPC2, RNASEL/HPC1, and MSR1 with prostate cancer have been inconsistent and understudied in African Americans. We evaluated the role of 16 sequence variants in these genes with prostate cancer using 888 European American and 131 African American cases, and 473 European American and 163 African American, controls. We observed significant differences in ELAC2, RNASEL, and MSR1 allele frequencies by race. However, we did not observe significant associations between prostate cancer and any variants examined for both races combined. Associations were observed when stratified by race, family history, or disease severity. European American men homozygous for MSR1 IVS7delTTA had an elevated risk for localized stage [odds ratio, (OR), 3.5; 95% confidence interval (95% CI), 1.4-6.9], low-grade (OR, 3.2; 95% CI, 1.4-7.3) disease overall, and with low-grade (OR, 2.9; 95% CI, 1.2-7.2) or late-stage disease (OR, 5.2; 95% CI, 1.1-25.7) in family history-negative African Americans. MSR1 Arg293X was associated with family history-negative high-grade disease (OR, 4.0; 95% CI, 1.1-14.1) in European Americans. RNASEL Arg462Gln was associated with low-grade (OR, 1.5; 95% CI, 1.04-2.2) and early-stage (OR, 1.5; 95% CI, 1.02-2.1) disease in family history-negative European Americans. In family history-positive individuals, Arg462Gln was inversely associated with low-grade (OR, 0.43; 95% CI, 0.21-0.88) and low-stage (OR, 0.46; 95% CI, 0.22-0.95) disease. In African Americans, Arg462Gln was associated with positive family history high-stage disease (OR, 14.8; 95% CI, 1.6-135.7). Meta-analyses revealed significant associations of prostate cancer with MSR1 IVS7delTTA, -14,742 A>G, and Arg293X in European Americans; Asp174Tyr in African Americans; RNASEL Arg462Gln in European American's overall and in family history-negative disease; and Glu265X in family history-positive European Americans. Therefore, MSR1 and RNASEL may play a role in prostate cancer progression and severity.     

Gene‐expression‐based analysis of local and metastatic neuroblastoma variants reveals a set of genes associated with tumor progression in neuroblastoma patients

Metastasis is the primary cause of mortality in Neuroblastoma (NB) patients, but the metastatic process in NB is poorly understood. Metastsis is a multistep process that requires the coordinated action of many genes. The identification of genes that promote or suppress tumor metastasis can advance our understanding of this process. In the present study, we utilized a human NB xenograft model comprising local and metastatic NB variants, which was recently developed in our laboratory. We set out to identify molecular correlates of NB metastasis and to determine the clinical relevance of these molecules. We first performed genome‐wide expression profiles of metastatic and nonmetastatic NB variants that have an identical genetic background. We found that some of the proteins highly expressed in the metastatic NB variants are localized in the cytoplasm and endoplasmic reticulum. Other proteins are linked to metabolic processes and signaling pathways, thereby supporting the invasive and metastatic state of the cells. Subsequently, we intersected the differentially expressed genes in the human xenografted variants with genes differentially expressed in Stage 1 and Stage 4 primary tumors of NB patients. By using the same gene‐expression platform, molecular correlates associated with metastatic progression in primary NB tumors were identified. The resulting smaller gene set was clinically relevant as it discriminated between high‐ and low‐risk NB patients.     

Tumor endothelial cells accelerate tumor metastasis

Tumor metastasis is the main cause of cancer‐related death. Understanding the molecular mechanisms underlying tumor metastasis is crucial to control this fatal disease. Several molecular pathways orchestrate the complex biological cell events during a metastatic cascade. It is now well known that bidirectional interaction between tumor cells and their microenvironment, including tumor stroma, is important for tumor progression and metastasis. Tumor stromal cells, which acquire their specific characteristics in the tumor microenvironment, accelerate tumor malignancy. The formation of new blood vessels, termed as tumor angiogenesis, is a requirement for tumor progression. Tumor blood vessels supply nutrients and oxygen and also provide the route for metastasis. Tumor endothelial cells, which line tumor blood vessels, also exhibit several altered phenotypes compared with those of their normal counterparts. Recent studies have emphasized “angiocrine factors” that are released from tumor endothelial cells and promote tumor progression. During intravasation, tumor cells physically contact tumor endothelial cells and interact with them by juxtacrine and paracrine signaling. Recently, we observed that in highly metastatic tumors, tumor endothelial cells interact with tumor cells by secretion of a small leucine‐rich repeat proteoglycan known as biglycan. Biglycan from tumor endothelial cells stimulates the tumor cells to metastasize. In the present review, we highlight the role of tumor stromal cells, particularly endothelial cells, in the initial steps of tumor metastasis.     

Expression of the human cachexia-associated protein (HCAP) in prostate cancer and in a prostate cancer animal model of cachexia

Prostate cancer (CaP) patients with disseminated disease often suffer from severe cachexia, which contributes to mortality in advanced cancer. Human cachexia-associated protein (HCAP) was recently identified from a breast cancer library based on the available 20-amino acid sequence of proteolysis-inducing factor (PIF), which is a highly active cachectic factor isolated from mouse colon adenocarcinoma MAC16. Herein, we investigated the expression of HCAP in CaP and its potential involvement in CaP-associated cachexia. HCAP mRNA was detected in CaP cell lines, in primary CaP tissues and in its osseous metastases. In situ hybridization showed HCAP mRNA to be localized only in the epithelial cells in CaP tissues, in the metastatic foci in bone, liver and lymph node, but not in the stromal cells or in normal prostate tissues. HCAP protein was detected in 9 of 14 CaP metastases but not in normal prostate tissues from cadaveric donors or patients with organ-confined tumors. Our Western blot analysis revealed that HCAP was present in 9 of 19 urine specimens from cachectic CaP patients but not in 19 urine samples of noncachectic patients. HCAP mRNA and protein were also detected in LuCaP 35 and PC-3M xenografts from our cachectic animal models. Our results demonstrated that human CaP cells express HCAP and the expression of HCAP is associated with the progression of CaP and the development of CaP cachexia.     

Genetic pattern of prostate cancer progression

Genetic alterations in primary prostate cancer (CaP) have been extensively studied, yet little is known about the genetic mechanisms underlying progression of primary CaP to metastatic prostate cancer. As a result, it is not possible to distinguish clinically indolent localized disease from potentially life-threatening tumors with high metastatic potential. To address this question, we collected tissue from 34 autopsy-derived metastases, samples rarely analyzed in previous studies. These were compared to a separate set of 17 prostatectomy specimens containing 22 foci of CaP associated with 49 examples of high-grade prostatic intraepithelial neoplasia (PIN), a histological precursor of CaP. We compared the loss of heterozygosity (LOH) profiles of high-grade PIN, primary CaP and metastases by analyzing 33 microsatellite markers previously found to have high frequencies of LOH in primary CaP. These markers were on chromosomes 5q, 6q, 7q, 8p, 9p, 10q, 11p, 13q, 16q, 17, 18q and 21q. In addition, markers on chromosomes 4p, 11q, 14q and 20q with no reported LOH in primary CaP were analyzed to determine the frequency of background LOH. In PIN lesions, the rate of LOH was significant only at D5S806 (20%) and D16S422 (29%). In addition, different PIN lesions within the same prostate gland were genetically diverse, indicating divergent evolution of synchronous neoplastic precursor lesions. LOH frequency was progressively higher in primary CaP and metastatic lesions. In primary CaP, significant losses occurred at the 8p, 10q, 11p, 16q, 17p, 18q and 21q loci (range 17-43%). Distinct patterns of LOH frequencies were observed in primary CaP compared with metastases. Although some loci (D16S422, D17S960, D21S156) showed similar frequencies of LOH in primary CaP and metastatic CaP, most other loci showed up to 7-fold metastasis-related increases. The metastatic samples revealed previously unrecognized prostate cancer LOH at D5S806, D6S262, D9S157, D13S133 and D13S227. These significant stage-specific differences in LOH frequency specify genetic loci that may play key roles in CaP progression and could represent clinically useful biomarkers for CaP aggressiveness.     

Exploring racial differences in outcome and treatment for metastatic colorectal cancer: results from a large prospective observational cohort study (BRiTE)

BACKGROUND:

African Americans are more likely to be diagnosed with metastatic colorectal cancer than whites and have shorter survival once they are diagnosed. In this analysis, the authors examined racial differences in clinical outcomes among patients with metastatic colorectal cancer (mCRC) who received bevacizumab.

METHODS:

The study cohort consisted of 1589 white patients (81.4%) and 227 African American patients (11.6%) with mCRC who received front‐line bevacizumab therapy and who were enrolled in a large, predominantly community‐based, prospective, observational cohort study. Differences in time‐to‐event endpoints and response rates were examined by race. Differences in the incidence of baseline and treatment‐related toxicities associated with bevacizumab also were examined. Finally, differences in patterns of care by race were explored.

RESULTS:

The median overall survival was 22.6 months for African Americans and 22.9 months for whites, and the median progression‐free survival was 9.5 months for African Americans and 9.8 months for whites. Response rates (complete responses plus partial responses) were 37.5% for African Americans and 46.3% for whites (adjusted odds ratio, 0.67; 95% confidence interval, 0.50‐0.90). African Americans had higher rates of baseline diabetes (18.9% vs 11%; P = .002), higher rates of hypertension (52.9% vs 41.4%; P = .001), and worsening hypertension while on therapy (13.7% vs 8.9%; P = .02), but no differences in on‐treatment arterial thromboembolic events were observed.

CONCLUSIONS:

This large observational cohort study of patients with mCRC demonstrated that, when treated in a similar fashion with modern chemotherapy, African Americans and whites had equivalent cancer outcomes. No significant differences in bevacizumab‐related toxicity or patterns of care were observed between African Americans and whites. The lower response rate among African Americans deserves further study. Cancer 2012;. © 2011 American Cancer Society.     

Down‐regulation of KIAA1199/CEMIP by miR‐216a suppresses tumor invasion and metastasis in colorectal cancer

Colorectal cancer is one of the major causes of death from cancer. Metastasis is the leading cause of treatment failure, in which cancer stem cells and circulating tumor cells play crucial roles. Identifying the involved metastatic biomarkers and clarifying the regulation mechanisms are of great importance for targeting tumor metastasis. In the current research, we discovered that KIAA1199, a cell‐migration inducing protein, showed higher expression in CD44+ cancer cells from metastatic compared with the paired primary tissues, and was upregulated in colorectal cancer and positively correlated with numbers and mesenchymal phenotype of circulating tumor cells, and predicted shorter progress‐free survival. Moreover, we indicated that down‐regulation of KIAA1199 suppressed migration and invasion of colorectal cancer cells in vitro, and inhibited metastasis in vivo. Furthermore, we demonstrated that KIAA1199 was one of the direct and functional targets of miR‐216a, and miR‐216a overexpression led to decreased migration and invasion of colorectal cancer cells in vitro, and inhibited metastasis in vivo. Collectively, KIAA1199 plays a critical role in maintaining an aggressive phenotype of tumor cells, and suppression of KIAA1199‐related motilities of tumor cells contributes to reduced tumor metastasis in colorectal cancer.     

Somatic LMCD1 mutations promoted cell migration and tumor metastasis in hepatocellular carcinoma

Common genetic alteration in cancer genomes is implicated for embracing an aberrant cancer gene participated in tumor progression. In this study, we identified a somatic mutated LIM and cysteine-rich domains-1 (LMCD1) as a putative metastatic oncogene in human hepatocellular carcinoma (HCC) using integrated genomic approaches. In addition to revealing genomic amplification and gene upregulation, we identified recurrent E135K (3/48 cases) mutations in HCC tissues and K237R mutation in the PLC/PRF/5 HCC cell line. Expression of mutant LMCD1 E135K or K237R reduced the stress fiber assembly, increased cortical actin accumulation and induced lamellipodial extension. Consistently, these mutations enhanced cell migration and showed activation of the Rac1-signaling pathway. Inhibition of the LMCD1/Rac1 pathway by an LMCD1 short-hairpin RNA (shLMCD1) or the Rac1 inhibitor NSC23766 suppressed the mutation-mediated lamellipodial protrusion and cell migration. In PLC/PRF/5 cells with endogenous K237R mutation, cell migration was enhanced by estrogen-induced LMCD1 expression but reversed by shLMCD1 treatment. Moreover, overexpression of LMCD1 E135K mutation significantly promoted systemic lung metastasis in a murine tail vein injection model. Together, our results suggest that LMCD1 mutations are potential oncogenic events in HCC metastasis to promote cell migration through the Rac1-signaling pathway.     

A role for bone morphogenetic protein-4 in lymph node vascular remodeling and primary tumor growth

Lymph node metastasis, an early and prognostically important event in the progression of many human cancers, is associated with expression of VEGF-D. Changes to lymph node vasculature that occur during malignant progression may create a metastatic niche capable of attracting and supporting tumor cells. In this study, we sought to characterize molecules expressed in lymph node endothelium that could represent therapeutic or prognostic targets. Differential mRNA expression profiling of endothelial cells from lymph nodes that drained metastatic or nonmetastatic primary tumors revealed genes associated with tumor progression, in particular bone morphogenetic protein-4 (BMP-4). Metastasis driven by VEGF-D was associated with reduced BMP-4 expression in high endothelial venules, where BMP-4 loss could remodel the typical high-walled phenotype to thin-walled vessels. VEGF-D expression was sufficient to suppress proliferation of the more typical BMP-4-expressing high endothelial venules in favor of remodeled vessels, and mechanistic studies indicated that VEGF receptor-2 contributed to high endothelial venule proliferation and remodeling. BMP-4 could regulate high endothelial venule phenotype and cellular function, thereby determining morphology and proliferation responses. Notably, therapeutic administration of BMP-4 suppressed primary tumor growth, acting both at the level of tumor cells and tumor stromal cells. Together, our results show that VEGF-D-driven metastasis induces vascular remodeling in lymph nodes. Furthermore, they implicate BMP-4 as a negative regulator of this process, suggesting its potential utility as a prognostic marker or antitumor agent.     

Targeting uPA/uPAR in prostate cancer

Prostate cancer (CaP) is one of the most common malignancies in men, with an increasing incidence. Despite significant advances in surgery, chemotherapy and radiotherapy to treat CaP, many patients unfortunately succumb to secondary disease (metastases). The invasive ability of tumour cells plays a key role in CaP metastasis and is a major cause of treatment failure. Urokinase plasminogen activator (uPA) and its receptor (uPAR)-mediated signalling have been implicated in tumour cell invasion, survival, and metastasis in a variety of cancers including CaP. Both uPA and uPAR are expressed at much higher levels in CaP tissues than in benign and normal prostate tissues. They are used as diagnostic markers as well as therapeutic targets due to their aberrant and unique expression pattern during cancer progression. Current therapeutic options for patients with metastatic hormone-refractory CaP (HRPC) are very limited. Therefore, much effort is currently being directed toward targeting aberrant uPA or uPAR activity in CaP. This review summarizes some important new findings supporting the role of uPA/uPAR in CaP progression and establishing the potential therapeutic efficacy of uPA/uPAR-targeted therapies in CaP.     

Repression of IFN regulatory factor 8 by DNA methylation is a molecular determinant of apoptotic resistance and metastatic phenotype in metastatic tumor cells

Apoptotic resistance is often associated with metastatic phenotype in tumor cells and is considered a hallmark of tumor progression. In this study, IFN regulatory factor 8 (IRF8) expression was found to be inversely correlated with an apoptotic-resistant and metastatic phenotype in human colon carcinoma cell lines in vitro. This inverse correlation was further extended to spontaneously arising primary mammary carcinoma and lung metastases in a mouse tumor model in vivo. Exogenous expression of IRF8 in the metastatic tumor cell line restored, at least partially, the sensitivity of the tumor cells to Fas-mediated apoptosis, and disruption of IRF8 function conferred the poorly metastatic tumors with enhanced apoptotic resistance and metastatic capability. DNA demethylation restored IRF8 expression and sensitized the metastatic tumor cells to Fas-mediated apoptosis. Analysis of genomic DNA isolated from both primary and metastatic tumor cells with methylation-sensitive PCR revealed hypermethylation of the IRF8 promoter in metastatic tumor cells but not in primary tumor cells. Taken together, our data suggest that IRF8 is both an essential regulator in Fas-mediated apoptosis pathway and a metastasis suppressor in solid tumors and that metastatic tumor cells use DNA hypermethylation to repress IRF8 expression to evade apoptotic cell death and to acquire a metastatic phenotype.     

Mouse model of postsurgical primary tumor recurrence and regional lymph node metastasis progression in HPV‐related head and neck cancer

HPV‐positive head and neck squamous cell carcinoma (HNSCC) is increasingly frequent. Management is particularly debated in the case of postsurgical high‐risk features, that is, positive surgical margins and extracapsular spread (ECS). In this increasingly complex emerging framework of HNSCC treatment, representative preclinical models are needed to support future clinical trials and advances in personalized medicine. Here, we present an immunocompetent mouse model based on the implantation of mouse tonsil epithelial HPV16‐E6/E7‐expressing cancer cells into the submental region of the floor‐of‐the‐mouth. Primary tumors were found to replicate the patterns of human HNSCC local invasion and lymphatic dissemination. To study disease progression after surgery, tumors were removed likely leaving behind residual disease. Surgical resection of tumors was followed by a high rate of local recurrences (>90%) within the first 2–3 weeks. While only 50% of mice had lymph node metastases (LNM) at time of primary tumor excision, all mice with recurrent tumors showed evidence of LNM. To study the consecutive steps of LNM progression and distant metastasis development, LNs from tumor‐bearing mice were transplanted into naïve recipient mice. Using this approach, transplanted LNs were found to recapitulate all stages and relevant histological features of regional metastasis progression, including ECS and metastatic spread to the lungs. Altogether, we have developed an immunocompetent HPV‐positive HNSCC mouse model of postsurgical local recurrence and regional and distant metastasis progression suitable for preclinical studies.     

miR‐122 promotes metastasis of clear‐cell renal cell carcinoma by downregulating Dicer

Although overall downregulation of microRNAs (miRNAs) is a general feature of clear‐cell renal cell carcinoma (ccRCC), several miRNAs are consistently upregulated, among which miR‐122 was markedly increased in ccRCC tissues. Our study aims to determine the functional importance and underlying mechanism of miR‐122 in ccRCC metastasis. Here, we demonstrate that the expression of miR‐122 increased in ccRCC tissues, and higher miR‐122 expression was found in ccRCC tissues with metastatic disease than in those without metastasis. The increased miR‐122 levels were associated with poor metastasis‐free survival in ccRCC patients with localized disease. Dicer was validated as a direct functional target of miR‐122. Overexpression of miR‐122 promoted migration and invasion of ccRCC cells in vitro and metastatic behavior of ccRCC cells in vivo. Inhibition of miR‐122 attenuated this metastatic phenotype in vitro. Importantly, miR‐122 exerted its pro‐metastatic properties in ccRCC cells by downregulating Dicer and its downstream effector, the miR‐200 family, thereby inducing epithelial–mesenchymal transition (EMT). Our results suggest an important role of the miR‐122/Dicer/miR‐200s/EMT pathway in ccRCC metastasis. Furthermore, miR‐122 may serve as a biomarker for discriminating ccRCC with metastatic potential.