Fragmented hyaluronan is an autocrine chemokinetic motility factor supported by the HAS2-HYAL2/CD44 system on the plasma membrane

Hyaluronan (HA) is synthesized by HA synthase (HAS) 1, HAS2 and HAS3, and degraded by hyaluronidase (HYAL) 1 and HYAL2 in a CD44-dependent manner. HA and HYALs are intricately involved in tumor growth and metastasis. Random cell movement is generally described as chemokinesis, and represents an important step at the beginning of tumor cell liberation from the primary site. To investigate the roles of HAS2 and HYAL2/CD44 in cell motility, we examined HeLa-S3 cells showing spontaneous chemokinesis. HeLa-S3 cells expressed HAS2 and HAS3. siRNA-mediated knockdown of HAS2 decreased spontaneous chemokinesis of HeLa-S3 cells. Although HeLa-S3 cells secreted 50 ng/ml of high molecular weight (HMW)-HA (peak: 990 kDa) into the culture supernatant after 6 h of culture, exogenously added HMW-HA did not enhance spontaneous chemokinesis of the cells. These observations suggested that HeLa-S3 cells may have a self-degrading system for HA to regulate their spontaneous chemokinesis. To examine this possibility, we investigated the effects of siRNA-mediated knockdown of HYAL2 or CD44 on the spontaneous chemokinesis of HeLa-S3 cells. Knockdown of either molecule decreased the spontaneous chemokinesis of the cells. Low molecular weight (LMW)-HA (23 kDa) reversed the HYAL2 siRNA-mediated reduction in spontaneous chemokinesis of HeLa-S3 cells to the level in control cells stimulated with the same HA. These findings indicate that the HAS2-HYAL2/CD44 system may support spontaneous chemokinesis of human cancer cells through self-degradation of HMW-HA to produce LMW-HA by an autocrine mechanism. Consequently, our study may further expand our understanding of HA functions in cancer.     

Hyaluronic acid synthase-1 expression regulates bladder cancer growth, invasion, and angiogenesis through CD44

Hyaluronic acid (HA) promotes tumor metastasis and is an accurate diagnostic marker for bladder cancer. HA is synthesized by HA synthases HAS1, HAS2, or HAS3. We have previously shown that HAS1 expression in tumor tissues is a predictor of bladder cancer recurrence and treatment failure. In this study, we stably transfected HT1376 bladder cancer cells with HAS1-sense (HAS1-S), HAS1-antisense (HAS1-AS), or vector cDNA constructs. Whereas HAS1-S transfectants produced approximately 1.7-fold more HA than vector transfectants, HA production was reduced by approximately 70% in HAS1-AS transfectants. HAS1-AS transfectants grew 5-fold slower and were approximately 60% less invasive than vector and HAS1-S transfectants. HAS1-AS transfectants were blocked in G(2)-M phase of the cell cycle due to down-regulation of cyclin B1, cdc25c, and cyclin-dependent kinase 1 levels. These transfectants were also 5- to 10-fold more apoptotic due to the activation of the Fas-Fas ligand-mediated extrinsic pathway. HAS1-AS transfectants showed a approximately 4-fold decrease in ErbB2 phosphorylation and down-regulation of CD44 variant isoforms (CD44-v3, CD44-v6, and CD44-E) both at the protein and mRNA levels. However, no decrease in RHAMM levels was observed. The decrease in CD44-v mRNA levels was not due to increased mRNA degradation. Whereas CD44 small interfering RNA (siRNA) transfection decreased cell growth and induced apoptosis in HT1376 cells, HA addition modestly increased CD44 expression and cell growth in HAS1-AS transfectants, which could be blocked by CD44 siRNA. In xenograft studies, HAS1-AS tumors grew 3- to 5-fold slower and had approximately 4-fold lower microvessel density. These results show that HAS1 regulates bladder cancer growth and progression by modulating HA synthesis and HA receptor levels.     

Hyaluronan synthases (HAS1-3) and hyaluronidases (HYAL1-2) in the accumulation of hyaluronan in endometrioid endometrial carcinoma

Background  

Hyaluronan accumulation correlates with the degree of malignancy in many solid tumor types, including malignant endometrial carcinomas. To elucidate the mechanism of hyaluronan accumulation, we examined the expression levels of the hyaluronan synthases (HAS1, HAS2 and HAS3) and hyaluronidases (HYAL1 and HYAL2), and correlated them with hyaluronan content and HAS1-3 immunoreactivity.     

Expression of Hyaluronan Synthases (HAS1–3) and Hyaluronidases (HYAL1–2) in Serous Ovarian Carcinomas: Inverse Correlation between HYAL1 and Hyaluronan Content

Background  

Hyaluronan, a tumor promoting extracellular matrix polysaccharide, is elevated in malignant epithelial ovarian tumors, and associates with an unfavorable prognosis. To explore possible contributors to the accumulation of hyaluronan, we examined the expression of hyaluronan synthases (HAS1, HAS2 and HAS3) and hyaluronidases (HYAL1 and HYAL2), correlated with hyaluronidase enzyme activity hyaluronan content and HAS1–3 immunoreactivity.     

Hyaluronate Receptors Mediating Glioma Cell Migration and Proliferation

The extracellular matrix (ECM) of the central nervous system (CNS) is enriched in hyaluronate (HA). Ubiquitous receptors for HA are CD44 and the Receptor for HA-Mediated Motility known as RHAMM. In the present study, we have investigated the potential role of CD44 and RHAMM in the migration and proliferation of human astrocytoma cells. HA-receptor expression in brain tumor cell lines and surgical specimens was determined by immunocytochemistry and western blot analyses. The ability of RHAMM to bind ligand was determined through cetylpyridinium chloride (CPC) precipitations of brain tumor lysates in HA-binding assays. The effects of HA, CD44 blocking antibodies, and RHAMM soluble peptide on astrocytoma cell growth and migration was determined using MTT and migration assays. Our results show that the expression of the HA-receptors, CD44, and RHAMM, is virtually ubiquitous amongst glioma cell lines, and glioma tumor specimens. There was a gradient of expression amongst gliomas with high grade gliomas expressing more RHAMM and CD44 than did lower grade lesions or did normal human astrocytes or non-neoplastic specimens of human brain. Specific RHAMM variants of 85- and 58-kDa size were shown to bind avidly to HA following CPC precipitations. RHAMM soluble peptide inhibited glioma cell line proliferation in a dose-dependent fashion. Finally, while anti-CD44 antibodies did not inhibit the migration of human glioma cells, soluble peptides directed at the HA-binding domain of RHAMM inhibited glioma migration both on and off an HA-based ECM. These data support the notion that HA-receptors contribute to brain tumor adhesion, proliferation, and migration, biological features which must be better understood before more effective treatment strategies for these tumors can be found.     

Role of HYAL1 expression in primary breast cancer in the formation of brain metastases

Background

The incidence of brain metastases in breast cancer patients has increased in the last years. However, the knowledge about tumor cell invasion in the brain is still very limited. Based on our recent study on cDNA microarray data of breast cancer patients, we hypothesized that two enzymes involved in the hyaluronan metabolism, namely, hyaluronan synthase 2 (HAS2) and hyaluronidase 1 (HYAL1) are associated with brain metastases formation.

Methods

Protein expression levels of hyaluronan, HAS2, and HYAL1 were analyzed in primary breast cancer, and metastatic tissue samples from different localizations (brain, bone, skin, liver, and lung) were included in four different cohorts by immunohistochemistry. Correlations of expression levels with clinical and pathological parameters were performed within the individual cohorts.

Results

Higher HYAL1 expression was detected among primary tumors from patients with subsequent brain metastases compared with those without brain metastases (p = 0.011). Interestingly, brain metastatic tissue showed a significantly reduced HYAL1 expression compared with the corresponding primary tumor (p = 0.003). HYAL1 expression in brain metastases was also significantly lower than in skin, liver, and lung metastases. Further, hyaluronan staining in brain metastases was mainly located on the surface of the tumor cells, whereas in all other metastatic sites hyaluronan was only detected in the extracellular matrix. We could not show an association of HAS2 with the formation of brain metastases.

Conclusions

In conclusion, our results suggest that the enzyme HYAL1 plays a role in tumor dissemination and brain-specific colonization, rather than in subsequent metastatic out-growth.

     

Activated extracellular signal‐regulated kinase is an independent prognostic factor in clinically confined renal cell carcinoma

BACKGROUND:

Extracellular signal‐regulated kinase (ERK) promotes proliferation, metastasis, and poor survival in cancers of the breast, lung, and liver. Advanced localized renal cell carcinoma (RCC) is extraordinarily treatment resistant and has high recurrence rates despite surgery. Limited data exist regarding the prognostic significance of activated (phosphorylated) ERK in RCC. The authors hypothesized that activated ERK (pERK) promotes disease progression and metastasis in localized RCC and may be of value as a biomarker to predict disease recurrence.

METHODS:

The expression profile of pERK was examined by immunocytochemistry using a tissue microarray constructed from 174 drug treatment–naive patients who had undergone radical nephrectomy for localized RCC. Levels of tumor‐cell specific pERK were scored and correlated with clinicopathologic parameters of RCC and disease‐free survival.

RESULTS:

Immunostaining for pERK was present in 36% of all RCCs, with a predominance found in the clear cell histologic subtype. High expression was associated with increased tumor size, increased TNM stage, and vascular invasion. Patients with pERK‐positive tumors had a mean disease‐free survival of 4.19 years, compared with 6.38 years for patients with pERK‐negative tumors (P < .001). Cox regression models revealed pERK to be a significant independent predictor of disease‐free survival, with a hazards score of 2.9 (P < .001), a value similar to tumor grade (hazards ratio, 3.01; P < .001).

CONCLUSIONS:

Expression of pERK is an independent prognostic factor in RCC that is associated with advanced and aggressive pathologic features of renal tumors and predicts the onset of metastasis in patients with localized disease. Cancer 2009. © 2009 American Cancer Society.     

Immunohistochemical analyses of CD44 variant isoforms in invasive micropapillary carcinoma of the breast: comparison with a concurrent conventional invasive carcinoma of no special type component

Background

Invasive micropapillary carcinoma (IMPC) is a distinct histopathological variant of breast carcinoma and frequently develops lymph node metastases. CD44 is a family of transmembrane glycoprotein receptors with multiple variant isoforms (CD44v), which have tissue-specific expression. Previous studies have demonstrated a loss or gain of CD44v and CD44 standard form (CD44s) expression in breast carcinomas. In this study, we analyzed the immunoprofiles of CD44s, CD44v6, and CD44v9 in IMPC and compared them with those in a concurrent invasive carcinoma of no special type (ICNST) component, thus clarifying the significance of CD44 expression in IMPC.

Methods

Twenty-one consecutive cases of mixed IMPC were included in this study. The expression statuses of CD44s, CD44v6, and CD44v9 in both the IMPC and ICNST components were analyzed semiquantitatively by immunohistochemistry.

Results

The immunohistochemical scores of CD44s, CD44v6, and CD44v9 were significantly decreased in the IMPC component compared to the ICNST component (p = 0.00335 for CD44s, p = 0.000982 for CD44v6, and p = 0.00271 for CD44v9). Moreover, the immunohistochemical scores of CD44v6 in the IMPC component and CD44v9 in the ICNST component of lymph node metastasis cases were significantly lower compared to cases without lymph node metastasis (p < 0.01).

Conclusions

Decreased CD44 expression may play an important role in promoting lymph node metastasis in IMPC through an inability or decreased capacity to bind with the surrounding stroma. Moreover, high CD44s⁺ expression levels in the concurrent ICNST component may be related to the development of IMPC.

     

Antisense-mediated suppression of hyaluronan synthase 2 inhibits the tumorigenesis and progression of breast cancer

The progression of several cancers is correlated with the increased synthesis of the glycosaminoglycan, hyaluronan. Hyaluronan is synthesized at the plasma membrane by various isoforms of hyaluronan synthases (HAS). The importance of HAS2 expression in highly invasive breast cancer was characterized by the antisense inhibition of HAS2 (ASHAS2). The effect of HAS2 inhibition on cell proliferation, migration, hyaluronan metabolism, and receptor status was characterized in vitro, whereas the effect on tumorigenicity and metastasis was established in vivo. HAS2 inhibition resulted in a 24-hour lag in proliferation that was concomitant to transient arrest of 79% of the cell population in G0-G1. Inhibition of HAS2 did not alter the expression of the other HAS isoforms, whereas hyaluronidase (HYAL2) and the hyaluronan receptor, CD44, were significantly down-regulated. ASHAS2 cells accumulated greater amounts of high molecular weight hyaluronan (>10,000 kDa) in the culture medium, whereas mock and parental cells liberated less hyaluronan of three distinct molecular weights (100, 400, and 3,000 kDa). The inhibition of HAS2 in the highly invasive MDA-MB-231 breast cancer cell line inhibited the initiation and progression of primary and secondary tumor formation following s.c. and intracardiac inoculation into nude mice, whereas controls readily established both primary and secondary tumors. The lack of primary and secondary tumor formation was manifested by increased survival times where ASHAS2 animals survived 172% longer than the control animals. Collectively, these unique results strongly implicate the central role of HAS2 in the initiation and progression of breast cancer, potentially highlighting the co-dependency between HAS2, CD44, and HYAL2 expression.     

HYAL1 overexpression is correlated with the malignant behavior of human breast cancer

Extracellular matrix (ECM) is closely correlated with tumor cell growth, proliferation, metastasis and angiogenesis, etc. Hyaluronic acid (HA) is a component of the ECM, and hyaluronidase (HAase) is a HA‐degrading endoglycosidase. Levels of HAase are elevated in many cancers. Hyaluronidase‐1 (HYAL1) is the major tumor‐derived HAase. In this study, we detected HYAL1 expression levels in breast cancer cells and tissues, and measured the amount HAase activity in breast cancer cells. Compared with nonmalignant breast cell line HBL‐100 and normal breast tissues, HYAL1 were overexpressed in breast cancer cell lines MDA‐MB‐231, MCF‐7, invasive duct cancer tissues and metastatic lymph nodes, respectively. Accordingly, the amount HAase activity in MDA‐MB‐231 and MCF‐7 was higher than that in HBL‐100. In addition, knockdown of HYAL1 expression in MDA‐MB‐231 and MCF‐7 cells resulted in decreased cell growth, adhesion, invasion and angiogenesis potential. Meantime, the HYAL1 knockdown markedly inhibited breast cancer cell xenograft tumor growth and microvessel density. Further studies showed that the HYAL1, HYAL2 and HA were elevated in breast cancer, and HYAL1 could downregulate HA expression. In conclusion, HYAL1 may be a potential prognostic marker and therapeutic target in breast cancer.     

Hyaluronan facilitates invasion of colon carcinoma cells in vitro via interaction with CD44

Hyaluronan (HA) and its biosynthetic enzymes, HA synthases (HAS1, 2, and 3) are thought to participate in cancer progression. We have shown previously that HA production and HAS3 expression are increased in metastatic colon carcinoma cells (SW620) when compared with cells isolated from a primary tumor (SW480). Because invasion of the extracellular matrix is a fundamental event in tumor growth and metastasis, we hypothesized that SW620 cells would show greater invasive capability than SW480 cells, that invasion is HA dependent, and that HA mediates invasion via interaction with a cell-surface receptor. Invasion into artificial basement membrane (Matrigel) was assessed in vitro. To assess HA functionality, HAS expression was inhibited in SW620 cells by transfection with antisense HAS constructs. Decreased HA secretion and retention in the transfectants were confirmed using competitive binding and particle exclusion assays. SW620 cells demonstrated greater invasion through Matrigel than did SW480 cells. Antisense transfection decreased Matrigel invasion by SW620 cells by >60%; addition of exogenous HA restored invasion. Because the cell-surface HA receptor CD44 has been implicated in cancer progression, HA-CD44 interaction was then inhibited by incubation with an anti-CD44 antibody. Anti-CD44 antibody impaired invasion into Matrigel by 95%. Taken together, these data suggest that pericellular HA is critical for colon carcinoma cell invasion and that this invasive capability is dependent on interaction with CD44.     

Identification of anaplastic lymphoma kinase fusions in renal cancer: Large-scale immunohistochemical screening by the intercalated antibody-enhanced polymer method

BACKGROUND:

Several promising molecular‐targeted drugs are used for advanced renal cancers. However, complete remission is rarely achieved, because none of the drugs targets a key molecule that is specific to the cancer, or is associated with “oncogene addiction” (dependence on one or a few oncogenes for cell survival) of renal cancer. Recently, an anaplastic lymphoma kinase (ALK) fusion, vinculin‐ALK, has been reported in pediatric renal cell carcinoma (RCC) cases who have a history of sickle cell trait. In this context, ALK inhibitor therapy would constitute a therapeutic advance, as has previously been demonstrated with lung cancer, inflammatory myofibroblastic tumors, and anaplastic large cell lymphomas.

METHODS:

Anti‐ALK immunohistochemistry was used to screen 355 tumor tissues, using the intercalated antibody‐enhanced polymer (iAEP) method. The cohort consisted of 255 clear cell RCCs, 32 papillary RCCs, 34 chromophobe RCCs, 6 collecting duct carcinomas, 10 unclassified RCCs, 6 sarcomatoid RCCs, and 12 other tumors.

RESULTS:

Two patients (36‐ and 53‐year‐old females) were positive for ALK as determined by iAEP immunohistochemistry. Using 5′‐ rapid amplification of complementary DNA ends, we detected TPM3‐ALK and EML4‐ALK in these tumors. The results of this study were confirmed by fluorescence in situ hybridization assays. The 2 ALK‐positive RCCs were unclassified (mixed features of papillary, mucinous cribriform, and solid patterns with rhabdoid cells) and papillary subtype. They comprised 2.3% of non–clear cell RCCs (2 of 88) and 3.7% of non–clear cell and nonchromophobe RCCs (2 of 54).

CONCLUSIONS:

The results of this study indicate that ALK fusions also exist in adult RCC cases without uncommon backgrounds. These findings confirm the potential of ALK inhibitor therapy for selected cases of RCC. Cancer 2012. © 2012 American Cancer Society.     

HAS3-related hyaluronan enhances biological activities necessary for metastasis of osteosarcoma cells

Several studies have suggested that increased production of hyaluronan (HA) is associated with metastatic behavior in various malignant tumors. To our knowledge, HA molecular weights required for metastasis are still unsolved in osteosarcoma. We examined the size of HA and hyaluronan synthase (HAS) isoforms related to biological functions required for metastasis in the LM8 stably highly metastatic osteosarcoma cell line. We found that HA of molecular weight which HAS3 produces enhanced biological functions related to metastasis such as cell proliferation, invasion, and degradation of extracellular matrix. Moreover, cell proliferation and invasion were inhibited by suppressing the activity of HAS3 expressed in LM8 cells, using hyaluronan synthase suppressor, 4-methylumbelliferone (MU). HA with the molecular weight related to HAS2 was the most adherent to CD44 in LM8 cells, suggesting that HAS2 may play an important role in pericellular coat formation. These results suggest that HAS3-related HA enhances crucial biological activities necessary for metastasis and that HAS2-related HA offers an advantageous environment for osteosarcoma cells.     

Assessment of the pathologic inclusion criteria from contemporary adjuvant clinical trials for predicting disease progression after nephrectomy for renal cell carcinoma

BACKGROUND:

The objective of this study was to evaluate the accuracy of the pathologic inclusion criteria from all contemporary adjuvant trials in predicting disease progression (DP) for renal cell carcinoma (RCC).

METHODS:

A retrospective review was conducted on 1363 patients treated surgically for M0 RCC at the Mayo Clinic (Rochester, MN), from 1990 to 2001. Clinicopathologic features were reviewed to determine eligibility for the following trials: ARISER, ASSURE, EVEREST, PROTECT, SORCE, and S‐TRAC. DP was defined as local recurrence or distant metastasis after surgery. The ability of each trial's inclusion criteria to accurately predict DP was evaluated by the c (concordance) index.

RESULTS:

From the Mayo Clinic cohort, we determined that 41%, 45%, 45%, 33%, 47%, and 23% of the patients would have been eligible for the ARISER, ASSURE, EVEREST, PROTECT, SORCE, and S‐TRAC clinical trials, respectively. Overall, 23% of all patients experienced DP (n = 317). Among eligible patients, 53%, 44%, 44%, 57%, 43%, and 59% developed DP during follow‐up and 10%, 6%, 6%, 13%, 6%, and 18% went onto DP while not being eligible for the ARISER, ASSURE, EVEREST, PROTECT, SORCE, and S‐TRAC trials, respectively. The c index of each trial to accurately predict DP from the pathologic inclusion criteria of ARISER, ASSURE, EVEREST, PROTECT, SORCE, and S‐TRAC were 0.751, 0.751, 0.751, 0.742, 0.745, and 0.691, respectively.

CONCLUSIONS:

Although the pathologic inclusion criteria of contemporary adjuvant trials have notable differences, all 6 adjuvant trials demonstrated high predictive accuracy of DP. Overall, 43% to 59% of patients included for the adjuvant trials would develop DP, whereas 6% to 18% of patients excluded from the trials would develop DP during follow‐up. Cancer 2012. © 2012 American Cancer Society.     

Assessment of the American Joint Committee on Cancer Staging (sixth and seventh editions) for clinically localized prostate cancer treated with external beam radiotherapy and comparison with the National Comprehensive Cancer Network risk‐stratification method

BACKGROUND:

The objective of this study was to compare the prognostic value of the sixth and seventh editions of the American Joint Cancer Committee (AJCC) Cancer Staging Manual and the risk‐stratification model of the National Comprehensive Cancer Network (NCCN).

METHODS:

Two‐thousand four hundred twenty‐nine men who received definitive radiotherapy with or without androgen‐deprivation therapy (median follow‐up, 74 months) were analyzed.

RESULTS:

There was a migration of stage II patients to stage I with AJCC seventh edition (stage I increased from 1% to 38%, and stage II decreased from 91% to 55%). One pair‐wise comparison (4%) of Kaplan‐Meier estimates of biochemical failure, distant metastasis, prostate cancer‐specific survival, and overall survival between stages was statistically significant for the AJCC sixth edition. Conversely, 16 of 24 comparisons (67%) were significant for the AJCC seventh edition. With the NCCN risk‐stratification model, 9 of 12 comparisons (75%) were significant. Concordance probability estimate (CPE) and standard error (SE) analysis indicated uniform and significant improvement in the predictive power of the AJCC seventh edition versus the sixth edition for all outcomes. CPE ± SE values for the AJCC seventh edition versus the sixth edition were 0.51 ± 0.009 versus 0.59 ± 0.02, respectively, for biochemical failure; 0.54 ± 0.02 versus 0.70 ± 0.05, respectively, for distant metastasis; 0.57 ± 0.009 versus 0.76 ± 0.007, respectively, for prostate cancer‐specific survival; and 0.52 ± 0.006 versus 0.57 ± 0.01, respectively, for overall survival. CPE ± SE values for the NCCN model were 0.59 ± 0.02 for biochemical failure, 0.72 ± 0.05 for distant metastasis, 0.80 ± 0.01 for prostate cancer‐specific survival, and 0.57 ± 0.01 for overall survival.

CONCLUSIONS:

The current results indicated that the seventh edition of the AJCC Cancer Staging Manual is a major improvement over the sixth edition, because it distributes patients better among the stages and is more prognostic. However, the NCCN model was superior to the AJCC seventh edition and remains the preferred method for risk‐based clinical management of prostate cancer with radiotherapy. Cancer 2012. © 2012 American Cancer Society.     

Expression of CIP2A in renal cell carcinomas correlates with tumour invasion, metastasis and patients' survival

Background:

Cancerous inhibitor of protein phosphatase 2A (CIP2A) drives cellular transformation. The objective of this study was to detect the potential effects of CIP2A in renal cell carcinomas (RCCs).

Methods:

A total of 107 RCC patients were involved in the study. Cancerous inhibitor of protein phosphatase 2A expression was investigated by real-time PCR and immunohistochemistry. In vitro, we examined the expression of CIP2A and c-Myc and tested the migration and invasion capability of A498 and KRC/Y cells with scratch migration assay and Matrigel invasion assay after down-regulating CIP2A expression using siRNA.

Results:

Cancerous inhibitor of protein phosphatase 2A was over-expressed in RCC tissues. Clear cell RCC showed an even higher-CIP2A expression level than papillary or chromophobe RCC did. The CIP2A immunostaining level was positively correlated with primary tumour stage, lymph node metastasis, distant metastasis, TNM stage and histological grade (all P<0.05). High-CIP2A expression implied poor survival for patients (P<0.05). Cancerous inhibitor of protein phosphatase 2A depletion by siRNA down-regulated c-Myc expression and attenuated the migration and invasion of RCC cells.

Conclusion:

Higher-CIP2A expression positively correlates with the aggressive phenotype of RCCs, and predicts poor prognosis for patients. Cancerous inhibitor of protein phosphatase 2A may be a novel target for prevention and treatment of RCC metastasis and recurrence.