Renal cell carcinoma bone metastasis--elucidating the molecular targets

Skeletal-Related Events in Renal Cell Carcinoma: Prediction With Alkaline Phosphatase (ALP), C-reactive Protein (CRP), Haemoglobin (Hb) and Erythrocyte Sedimentation Rate (ESR) (A.C.H.E.) Score for Risk Stratification

Introduction  Skeletal metastasis is catastrophic in patients with renal cell carcinoma (RCC), leading to skeletal-related events (SRE) such as nerve entrapment, hypercalcemia and even pathological fractures, which may require surgical intervention. The nature of the bone metastasis in advanced RCC is large, destructive, hyper-vascular and mostly lytic. The present retrospective analysis aims to identify potential risk factors for predicting SREs in advanced RCC with bone metastasis. Methods The clinical data of 42 patients with RCC and bone metastasis and at least one episode of SRE were reviewed, and the correlations between erythrocyte sedimentation rate (ESR), alkaline phosphatase (ALP), C-reactive protein (CRP), haemoglobin (Hb), carcinoembryonic antigen (CEA) and bone metastases were analysed. Risk factors were identified by multivariate logistic regression analysis. Bone metastasis was diagnosed on a bone scan. The receiver operating characteristic (ROC) curve calculated the cut-off value of the independent correlation factors. Results The areas under the ROC curve for ALP, Hb, CRP, and ESR were 0.84, 0.76, 0.86 and 0.88, respectively, suggesting excellent discriminatory capability of ALP, CRP, ESR and sufficient discriminative ability of Hb in predicting bone metastasis. Multivariate logistic regression analysis showed ALP, CRP, Hb and ESR associated with SRE and skeletal metastasis. Conclusion We propose that an A.C.H.E. score encompassing ALP, CRP, Hb, and ESR are potential risk factors for developing SRE and concomitant bone metastasis in advanced RCC patients. For new RCC patients, if values of ALP >128 U/L, CRP ≥74 mg/L, Hb <11.5 g/L, and ESR ≥55 mm/hr are detected, intensive monitoring and bone scanning are warranted as these cases are at a higher risk of skeletal events.

All bone metastases are not created equal: Revisiting treatment resistance in renal cell carcinoma

Renal cell carcinoma (RCC) is the most common malignancy of the kidney, representing 80-90% of renal neoplasms, and is associated with a five-year overall survival rate of approximately 74%. The second most common site of metastasis is bone. As patients are living longer due to new RCC targeting agents and immunotherapy, RCC bone metastases (RCCBM) treatment failure is more prevalent. Bone metastasis formation in RCC is indicative of a more aggressive disease and worse prognosis. Osteolysis is a prominent feature and causes SRE, including pathologic fractures. Bone metastasis from other tumors such as lung, breast, and prostate cancer, are more effectively treated with bisphosphonates and denosumab, thereby decreasing the need for palliative surgical intervention. Resistance to these antiresportives in RCCBM reflects unique cellular and molecular mechanisms in the bone microenvironment that promote progression via inhibition of the anabolic reparative response. Identification of critical mechanisms underlying RCCBM induced anabolic impairment could provide needed insight into how to improve treatment outcomes for patients with RCCBM, with the goals of minimizing progression that necessitates palliative surgery and improving survival.

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

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

c-Met expression in renal cell carcinoma with bone metastases

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Bone is a common metastatic site in renal cell carcinoma (RCC).

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HGF/c-Met pathway is particularly relevant in tumors with bone metastases.

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c-Met/HGF pathway is involved in RCC progression, conferring poor prognosis.

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Several c-Met targeting therapies are currently in clinical development.

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c-Met expression is an important therapeutic target in RCC with bone metastases.

Hepatocyte growth factor (HGF)/c-Met pathway is implicated in embryogenesis and organ development and differentiation. Germline or somatic mutations, chromosomal rearrangements, gene amplification, and transcriptional upregulation in MET or alterations in autocrine or paracrine c-Met signalling have been associated with cancer cell proliferation and survival, including in renal cell carcinoma (RCC), and associated with disease progression. HGF/c-Met pathway has been shown to be particularly relevant in tumors with bone metastases (BMs). However, the efficacy of targeting c-Met in bone metastatic disease, including in RCC, has not been proven. Therefore, further investigation is required focusing the particular role of HGF/c-Met pathway in bone microenvironment (BME) and how to effectively target this pathway in the context of bone metastatic disease.

Dysregulation of Type II Transmembrane Serine Proteases and Ligand-Dependent Activation of MET in Urological Cancers

Unlike in normal epithelium, dysregulated overactivation of various proteases have been reported in cancers. Degradation of pericancerous extracellular matrix leading to cancer cell invasion by matrix metalloproteases is well known evidence. On the other hand, several cell-surface proteases, including type II transmembrane serine proteases (TTSPs), also induce progression through activation of growth factors, protease activating receptors and other proteases. Hepatocyte growth factor (HGF) known as a multifunctional growth factor that upregulates cancer cell motility, invasiveness, proliferative, and anti-apoptotic activities through phosphorylation of MET (a specific receptor of HGF). HGF secreted as inactive zymogen (pro-HGF) from cancer associated stromal fibroblasts, and the proteolytic activation by several TTSPs including matriptase and hepsin is required. The activation is strictly regulated by HGF activator inhibitors (HAIs) in physiological condition. However, downregulation is frequently observed in cancers. Indeed, overactivation of MET by upregulation of matriptase and hepsin accompanied by the downregulation of HAIs in urological cancers (prostate cancer, renal cell carcinoma, and bladder cancer) are also reported, a phenomenon observed in cancer cells with malignant phenotype, and correlated with poor prognosis. In this review, we summarized current reports focusing on TTSPs, HAIs, and MET signaling axis in urological cancers.

An interdisciplinary consensus on the management of bone metastases from renal cell carcinoma

Bone is a major site of haematogenous tumour cell spread in renal cell carcinoma (RCC), and most patients with RCC will develop painful and functionally disabling bone metastases at advanced disease stages. The prognosis of these patients is generally poor and the treatment is, therefore, aimed at palliation. However, RCC-associated bone metastases can be curable in select patients. Current data support a multimodal management strategy that includes wide resection of lesions, radiotherapy, systemic therapy, and other local treatment options, which can improve quality of life and survival. Nevertheless, the optimal approach for metastatic bone disease in RCC has not yet been defined and practical recommendations are rare. To improve the management and outcomes of patients with RCC and bone metastases, the International Kidney Cancer Coalition and the interdisciplinary working group on renal tumours of the German Cancer Society convened a meeting of experts with a global perspective to perform an unstructured review and elaborate on current treatment strategies on the basis of published data and expertise. The panel formulated recommendations for the diagnosis and treatment of patients with RCC and metastasis to the bone. Furthermore, the experts summarized current challenges and unmet patient needs that should be addressed in the future.

In this Expert Consensus, Grünwald et al. summarize their recommendations for the diagnosis and treatment of patients with renal cell carcinoma and metastasis to the bone. They also outline current challenges and unmet patient needs that should be addressed in the future.

Dysregulated HAI-2 Plays an Important Role in Renal Cell Carcinoma Bone Metastasis through Ligand-Dependent MET Phosphorylation

MET, a c-met proto-oncogene product and hepatocyte growth factor (HGF) receptor, is known to play an important role in cancer progression, including bone metastasis. In a previous study, we reported increased expression of MET and matriptase, a novel activator of HGF, in bone metastasis. In this study, we employed a mouse model of renal cell carcinoma (RCC) bone metastasis to clarify the significance of the HGF/MET signaling axis and the regulator of HGF activator inhibitor type-2 (HAI-2). Luciferase-transfected 786-O cells were injected into the left cardiac ventricle of mice to prepare the mouse model of bone metastasis. The formation of bone metastasis was confirmed by whole-body bioluminescent imaging, and specimens were extracted. Expression of HGF/MET-related molecules was analyzed. Based on the results, we produced HAI-2 stable knockdown 786-O cells, and analyzed invasiveness and motility. Expression of HGF and matriptase was increased in bone metastasis compared with the control, while that of HAI-2 was decreased. Furthermore, we confirmed increased phosphorylation of MET in bone metastasis. The expression of matriptase was upregulated, and both invasiveness and motility were increased significantly by knockdown of HAI-2. The significance of ligand-dependent MET activation in RCC bone metastasis is considered, and HAI-2 may be an important regulator in this system.

Skeletal metastasis in renal cell carcinoma: A review

Background

Renal cell carcinoma account for 3% of all cancers, with peak incidence between 60 and 70 years of age predominantly affecting male population. Renal carcinoma is the most common malignancy of kidney constitutes for 80–90% of renal neoplasm with an overall 45% five years survival rate. Majority are diagnosed incidentally during investigation for other disease process of abdomen. Classical triad of gross hematuria, pain and palpable mass in abdomen is rare accounting to only 6–10%. Treatment of early stages of disease i.e. localized disease is partial or radical nephrectomy. Most common metastasis in RCC occurs to lung, followed by bone involvement in 20–35%, lymph nodes, liver, adrenal gland and brain. In metastatic disease median survival rate of patient is about eight months with 50% mortality rate within first year of life, five years survival rate is 10%. Skeletal metastasis are very destructive in patients with renal cell carcinoma compromising bone integrity leading to skeletal related events including pains, impending fractures, nerve compressions, hypercalcemia and even pathological fractures which may require surgical interventions and other therapy. In addition to skeletal complications, presence of bone metastases in RCC has negative impact on progression free survival and overall survival of patients treated with systemic therapies.

Objective

In this review we discuss pathophysiology of tumor metastasis, diagnosis, management and Case examples of metastatic renal cell carcinoma.

Conclusion

Incidence of metastatic renal carcinoma is increasing. Overall prognosis of patient with advanced RCC is poor, emphasizing the importance of early detection and prompt treatment of primary lesion in its early stage. Advancement in targeted therapy in recent decades had made some improvement in treatment of SREs and has helped in improving patent's quality of life but still we are in need of further improvement in treatment modalities to cure disease thereby decreasing morbidity and mortality.

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Renal cell carcinoma account for 3% of all cancers.

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It is a very destructive that may compromise bone integrity.

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Most common metastasis in renal cell carcinoma occurs to lung, followed by bone , lymph nodes, liver, adrenal gland and brain.

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Most common metastasis in renal cell carcinoma occurs to lung, followed by bone involvement in 20–35%, lymph nodes, liver, adrenal gland and brain.

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In metastatic disease median survival rate of patient is about eight months with 50% mortality rate within first year of life, five years survival rate is 10.

Bone Metastasis from Renal Cell Carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastasis that are often osteolytic and cause substantial morbidity, such as pain, pathologic fracture, spinal cord compression and hypercalcemia. The presence of bone metastasis in RCC is also associated with poor prognosis. Bone-targeted treatment using bisphosphonate and denosumab can reduce skeletal complications in RCC, but does not cure the disease or improve survival. Elucidating the molecular mechanisms of tumor-induced changes in the bone microenvironment is needed to develop effective treatment. The “vicious cycle” hypothesis has been used to describe how tumor cells interact with the bone microenvironment to drive bone destruction and tumor growth. Tumor cells secrete factors like parathyroid hormone-related peptide, transforming growth factor-β and vascular endothelial growth factor, which stimulate osteoblasts and increase the production of the receptor activator of nuclear factor κB ligand (RANKL). In turn, the overexpression of RANKL leads to increased osteoclast formation, activation and survival, thereby enhancing bone resorption. This review presents a general survey on bone metastasis in RCC by natural history, interaction among the immune system, bone and tumor, molecular mechanisms, bone turnover markers, therapies and healthcare burden.

Heterogeneous drug target expression as possible basis for different clinical and radiological response to the treatment of primary and metastatic renal cell carcinoma: suggestions from bench to bedside

Metastatic disease occurs in a significant percentage of patients with renal cell carcinoma (RCC) and is usually associated with an overall poor prognosis. However, not all of the sites of metastases seem to have the same prognostic significance in patients receiving targeted agents. Indeed, patients with lung-only metastases seem to present a better survival than patients with other sites, whereas liver and bone metastases are associated with a worst prognosis. Some clinical studies suggest that metastatic sites are more responsive than primary tumors. This event may be due to intratumor heterogeneity in terms of somatic mutations, chromosome aberrations, and tumor gene expression, primarily centered around Von Hippel-Lindau (VHL) pathway, such as VHL mutations, HIF levels, vascular endothelial growth factor (VEGF) isoforms, and VEGF receptor levels. Nevertheless, these data do not completely explain the discordant biological behavior between primary tumor and metastatic sites. Understanding the causes of this discordance will have profound consequences on translational research and clinical trials in RCC. In this review, we overview current data on the differences between primary RCC and metastases in terms of drug target expression and clinical/radiological response to targeted agents, thus describing the prognostic role of different metastatic sites in RCC patients.

Factors affecting survival in 37 consecutive patients undergoing de novo stereotactic radiosurgery for contiguous sites of vertebral body metastasis from renal cell carcinoma

OBJECT

Palliative resection of renal cell carcinoma (RCC) spinal metastasis is indicated in cases of neurological compromise or mechanical instability, whereas conventional external beam radiotherapy (EBRT) is commonly used for pain control. Recently, spinal stereotactic radiosurgery (SRS) has emerged as a safe alternative, delivering higher therapeutic doses of radiation to spinal metastases. To better understand factors affecting survival in patients undergoing spinal SRS for metastatic RCC, the authors performed a retrospective analysis of a consecutive series of cases at a tertiary cancer center.

METHODS

Patients harboring contiguous sites of vertebral body involvement from metastatic RCC who received upfront spinal SRS treatment at The University of Texas MD Anderson Cancer Center between 2005 and 2012 were identified. Demographic data, pain scores, radiographic data, overall survival, complications, status of systemic disease, neurological and functional status, and time between primary diagnosis and diagnosis of metastasis (systemic and spinal) were analyzed to determine their influence on survival.

RESULTS

Thirty-seven patients receiving treatment for 40 distinct, contiguous sites of disease were included. The median overall survival after spinal SRS was 16.3 months (range 7.4–25.3 months). Univariate analysis revealed several factors significantly associated with improved overall survival. Local progression after spinal SRS was associated with worse overall survival compared with sustained local control (HR 3.4, 95% CI 1.6–7.4, p = 0.002). Median survival in patients with a Karnofsky Performance Scale (KPS) score ≥ 70 was longer than in patients with a KPS score < 70 (HR 4.7, 95% CI 2.1–10.7, p < 0.001). Patients with neurological deficits at the time of spinal SRS had a shorter median survival than those without (HR 4.2, 95% CI 1.4–12.0, p = 0.008). Individuals with nonprogressive systemic disease at the time of spinal SRS had a longer median survival than those with systemic progression at the time of treatment (HR 8.3, 95% CI 3.3–20.7, p < 0.001). Median survival in patients experiencing any metastasis < 12 months after primary RCC diagnosis was shorter than in patients experiencing any metastasis > 12 months after primary diagnosis, a difference that approached but did not attain significance (HR 1.9, 95% CI 0.90–4.1, p = 0.09). On multivariate analysis, local progression of disease after spinal SRS, metastasis < 12 months after primary, KPS score ≤ 70, and progression of systemic disease at time of spinal SRS all remained significant factors influencing survival (respectively, HR 3.7, p = 0.002; HR 2.6, p = 0.026; HR 4.0, p = 0.002; and HR 13.2, p < 0.001).

CONCLUSIONS

We identified several factors associated with survival after spinal SRS for RCC metastases, including local progression, time between first metastasis and primary RCC diagnosis, KPS score, presence of neurological deficits, and progressive metastatic disease. These factors should be taken into consideration when considering a patient for spinal SRS for RCC metastases.

Metastatic renal cell carcinoma to the jaws: report of cases

Renal cell carcinoma (RCC) is one of the most frequent urological malignancies in adults. RCC often metastasizes to other organs, but rarely to the oromaxillofacial region. Metastatic tumors to the jaws are also unusual. In this report, we present two cases of RCC metastasis to the jaws. Metastatic RCC is resistant to radiotherapy and chemotherapy, so surgery is the primary therapeutic choice. This report describes the diagnostic procedures utilized and the therapeutic process in the two cases. The differential diagnosis and treatment methods are discussed.

Development of a realistic in vivo bone metastasis model of human renal cell carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastases. The incidence of RCC is increasing and bone metastatic RCC merits greater focus. Realistic preclinical bone metastasis models of RCC are lacking, hampering the development of effective therapies. We developed a realistic in vivo bone metastasis model of human RCC by implanting precision-cut tissue slices under the renal capsule of immunodeficient mice. The presence of disseminated cells in bone marrow of tissue slice graft (TSG)-bearing mice was screened by human-specific polymerase chain reaction and confirmed by immunohistology using human-specific antibody. Disseminated tumor cells in bone marrow of TSG-bearing mice derived from three of seven RCC patients were detected as early as 1 month after tissue implantation at a high frequency with close resemblance to parent tumors (e.g., CAIX expression and high vascularity). The metastatic patterns of TSGs correlated with disease progression in patients. In addition, TSGs retained capacity to metastasize to bone at high frequency after serial passaging and cryopreservation. Moreover, bone metastases in mice responded to Temsirolimus treatment. Intratibial injections of single cells generated from TSGs showed 100 % engraftment and produced X-ray-visible tumors as early as 3 weeks after cancer cell inoculation. Micro-computed tomography (μCT) and histological analysis revealed osteolytic characteristics of these lesions. Our results demonstrated that orthotopic RCC TSGs have potential to develop bone metastases that respond to standard therapy. This first reported primary RCC bone metastasis model provides a realistic setting to test therapeutics to prevent or treat bone metastases in RCC.

Cadherin-11 in renal cell carcinoma bone metastasis

Bone is one of the common sites of metastases from renal cell carcinoma (RCC), however the mechanism by which RCC preferentially metastasize to bone is poorly understood. Homing/retention of RCC cells to bone and subsequent proliferation are necessary steps for RCC cells to colonize bone. To explore possible mechanisms by which these processes occur, we used an in vivo metastasis model in which 786-O RCC cells were injected into SCID mice intracardially, and organotropic cell lines from bone, liver, and lymph node were selected. The expression of molecules affecting cell adhesion, angiogenesis, and osteolysis were then examined in these selected cells. Cadherin-11, a mesenchymal cadherin mainly expressed in osteoblasts, was significantly increased on the cell surface in bone metastasis-derived 786-O cells (Bo-786-O) compared to parental, liver, or lymph node-derived cells. In contrast, the homing receptor CXCR4 was equivalently expressed in cells derived from all organs. No significant difference was observed in the expression of angiogenic factors, including HIF-1α, VEGF, angiopoeitin-1, Tie2, c-MET, and osteolytic factors, including PTHrP, IL-6 and RANKL. While the parental and Bo-786-O cells have similar proliferation rates, Bo-786-O cells showed an increase in migration compared to the parental 786-O cells. Knockdown of Cadherin-11 using shRNA reduced the rate of migration in Bo-786-O cells, suggesting that Cadherin-11 contributes to the increased migration observed in bone-derived cells. Immunohistochemical analysis of cadherin-11 expression in a human renal carcinoma tissue array showed that the number of human specimens with positive cadherin-11 activity was significantly higher in tumors that metastasized to bone than that in primary tumors. Together, these results suggest that Cadherin-11 may play a role in RCC bone metastasis.

Analysis of molecular cytogenetic changes in metastatic renal cell carcinoma in the setting of everolimus treatment: a pilot project

BACKGROUND

The mTOR inhibitors have improved outcomes for patients with metastatic renal cell carcinoma (mRCC) but the duration of benefit is variable. Currently there are no predictive biomarkers for preselecting patients who are more likely to benefit from these agents. We undertook an exploratory translational study evaluating molecular cytogenetic changes in the context of outcomes from treatment with everolimus.

PATIENTS AND METHODS

Ten patients with clear cell mRCC treated with everolimus were enrolled. Pretreatment tissue specimens were analyzed for molecular cytogenetic changes using fluorescence in situ hybridization and progression-free survival (PFS) data were obtained. Gene probes chosen for this analysis were: Von Hippel Lindau, fragile histidine triad, fibroblast growth factor receptor (FGFR) 1, FGFR3, PDGFβ, PDGFRβ, epidermal growth factor receptor, and myelocytomatosis viral oncogene.

RESULTS

Median PFS was 8.75 months. Two patients with the longest PFS (28 months and 23 months) had gain of PDGFβ and PDGFRβ. This was also observed in 3 other patients who had a PFS of 11.5 months, 8 months, and 5.5 months, respectively. Cytogenetic evolution was observed between primary and metastatic specimens.

CONCLUSION

PDGFβ and PDGFRβ gene status might be of relevance to everolimus therapy. Further research evaluating the utility of these potential biomarkers is required.

Single-fraction stereotactic body radiotherapy for spinal metastases from renal cell carcinoma

Object

Stereotactic body radiotherapy (SBRT) has emerged as an important treatment option for spinal metastases from renal cell carcinoma (RCC) as a means to overcome RCC's inherent radioresistance. The authors reviewed the outcomes of SBRT for the treatment of RCC metastases to the spine at their institution, and they identified factors associated with treatment failure.

Methods

Fifty-seven patients (88 treatment sites) with RCC metastases to the spine received single-fraction SBRT. Pain relief was based on the Brief Pain Inventory and was adjusted for narcotic use according to the Radiation Therapy Oncology Group protocol 0631. Toxicity was scored according to Common Toxicity Criteria for Adverse Events version 4.0. Radiographic failure was defined as infield or adjacent (within 1 vertebral body [VB]) failure on follow-up MRI. Multivariate analyses were performed to correlate outcomes with the following variables: epidural, paraspinal, single-level, or multilevel disease (2–5 sites); neural foramen involvement; and VB fracture prior to SBRT. Kaplan-Meier analysis and Cox proportional hazards modeling were used for statistical analysis.

Results

The median follow-up and survival periods were 5.4 months (range 0.3–38 months) and 8.3 months (range 1.5–38 months), respectively. The median time to radiographic failure and unadjusted pain progression were 26.5 and 26.0 months, respectively. The median time to pain relief (from date of simulation) and duration of pain relief (from date of treatment) were 0.9 months (range 0.1–4.4 months) and 5.4 months (range 0.1–37.4 months), respectively. Multivariate analyses demonstrated that multilevel disease (hazard ratio [HR] 3.5, p = 0.02) and neural foramen involvement (HR 3.4, p = 0.02) were correlated with radiographic failure; multilevel disease (HR 2.3, p = 0.056) and VB fracture (HR 2.4, p = 0.046) were correlated with unadjusted pain progression. One patient experienced Grade 3 nausea and vomiting; no other Grade 3 or 4 toxicities were observed. Twelve treatment sites (14%) were complicated by subsequent vertebral fractures.

Conclusions

Stereotactic body radiotherapy for RCC metastases to the spine offers fast and durable pain relief with minimal toxicity. Stereotactic body radiotherapy seems optimal for patients who have solitary or few spinal metastases. Patients with neural foramen involvement are at an increased risk for failure.

Mapping of carboxypeptidase m in normal human kidney and renal cell carcinoma: expression in tumor-associated neovasculature and macrophages

Although the kidney generally has been regarded as an excellent source of carboxypeptidase M (CPM), little is known about its renal-specific expression level and distribution. This study provides a detailed localization of CPM in healthy and diseased human kidneys. The results indicate a broad distribution of CPM along the renal tubular structures in the healthy kidney. CPM was identified at the parietal epithelium beneath the Bowman's basement membrane and in glomerular mesangial cells. Capillaries, podocytes, and most interstitial cells were CPM negative. Tumor cells of renal cell carcinoma subtypes lose CPM expression upon dedifferentiation. Tissue microarray analysis demonstrated a correlation between low CPM expression and tumor cell type. CPM staining was intense on phagocytotic tumor-associated macrophages. Immunoreactive CPM was also detected in the tumor-associated vasculature. The absence of CPM in normal renal blood vessels points toward a role for CPM in angiogenesis. Coexistence of CPM and the epidermal growth factor receptor (EGFR) was detected in papillary renal cell carcinoma. However, the different subcellular localization of CPM and EGFR argues against an interaction between these h proteins. The description of the distribution of CPM in human kidney forms the foundation for further study of the (patho)physiological activities of CPM in the kidney.

microRNA-21 governs TORC1 activation in renal cancer cell proliferation and invasion

Metastatic renal cancer manifests multiple signatures of gene expression. Deviation in expression of mature miRNAs has been linked to human cancers. Importance of miR-21 in renal cell carcinomas is proposed from profiling studies using tumor tissue samples. However, the role of miR-21 function in causing renal cancer cell proliferation and invasion has not yet been shown. Using cultured renal carcinoma cells, we demonstrate enhanced expression of mature miR-21 along with pre-and pri-miR-21 by increased transcription compared to normal proximal tubular epithelial cells. Overexpression of miR-21 Sponge to quench endogenous miR-21 levels inhibited proliferation, migration and invasion of renal cancer cells. In the absence of mutation in the PTEN tumor suppressor gene, PTEN protein levels are frequently downregulated in renal cancer. We show that miR-21 targets PTEN mRNA 3'untranslated region to decrease PTEN protein expression and augments Akt phosphorylation in renal cancer cells. Downregulation of PTEN as well as overexpression of constitutively active Akt kinase prevented miR-21 Sponge-induced inhibition of renal cancer cell proliferation and migration. Moreover, we show that miR-21 Sponge inhibited the inactivating phosphorylation of the tumor suppressor protein tuberin and attenuated TORC1 activation. Finally, we demonstrate that expression of constitutively active TORC1 attenuated miR-21 Sponge-mediated suppression of proliferation and migration of renal cancer cells. Our results uncover a layer of post-transcriptional regulation of PTEN by transcriptional activation of miR-21 to force the canonical oncogenic Akt/TORC1 signaling conduit to drive renal cancer cell proliferation and invasion.

Exosomes and immune surveillance of neoplastic lesions: a review

The immune system has been reported to suppress the development and progression of neoplastic lesions; however, the exact mechanisms by which neoplastic lesions and the immune system interact are not well understood. Within the last decade, tiny membrane bound particles, approximately 30-100 nm in diameter, have been observed in the blood and other body fluids. These particles, currently called exosomes, are released from many types of tissues including tumors, and they contain and carry many proteins, and mRNAs and microRNA species. We review here how tumors suppress the immune system, especially by the formation of exosomes. Exosomes released from tumors are carried in part by the vascular system to distant cells, which phagocytose them. Depending on the proteins, mRNAs or microRNAs in the exosomes and the cell type, phagocytosis of exosomes may provide a modulating signal to the cell. In the case of exosomes from tumors, uptake of the exosomes by cells of the immune system has been reported to have three main effects: 1) suppression of the number and activity of natural killer cells, 2) suppression of the activity of T cells and 3) suppression of the number and maturation of mature dendritic cells.

A bone-seeking clone exhibits different biological properties from the ACHN parental human renal cell carcinoma in vivo and in vitro

Metastatic bone disease caused by renal cell carcinoma (RCC) occurs frequently. Very little is currently known about the mechanism of preferential metastasis of RCC to bone. We hypothesize that RCCs that develop bone metastases have the capacity to facilitate their colonization in bone. To examine this hypothesis, we established bone-seeking (ACHN-BO) clones of the human RCC cell line ACHN by repeated four passages in nude mice and in vitro of metastatic cells obtained from bone. These clones were examined for distinguishing biological characteristics and compared with the ACHN parental cells (ACHN-P) in vivo and in vitro. Our results showed that the ACHN-BO cell line could be successfully obtained by in vivo selection through the lateral tail vein. This approach results in the development of multiple osteolytic lesions in the distal femora and proximal tibiae within four weeks after inoculation, with a success rate of 85-100% and no additional comorbidity. ACHN-P cells developed metastases in lung, bone, brain, ovary and adrenal glands. Conversely, ACHN-BO cells exclusively metastasized to bones with larger osteolytic lesions. Compared with the ACHN-P cell line, the proliferation ability in ACHN-BO6 was increased by 9.68 and 6.42%, respectively (P<0.05), while the apoptotic ratio decreased significantly (P<0.05) and cells were blocked in the S phase with suppressed migration and invasion capacities. The ACHN-BO₆ cell line produced greater amounts of the pro-angiogenic factors VEGF and TGF-β than ACHN-P. Our data suggest that these phenotypic changes allow RCC cells to promote osteoclastic bone resorption, survive and proliferate in bone, which consequently leads to the establishment of bone metastases. This model provides a reliable reproduction of the clinical situation and, therefore, is suitable for designing and evaluating more effective treatments for RCC bone metastasis.

Solitary phalangeal metastasis of renal cell carcinoma on bone scintigram

Renal cell carcinoma is known to cause lytic metastasis at various sites including axial and appendicular skeleton. However, it is unusual to find an isolated metastasis of renal cell carcinoma in the distal extremity on bone scintigraphy. A 70-year-old woman with renal cell carcinoma was referred to the Nuclear Medicine Department for a bone scintigram to exclude metastasis. The whole-body planar images were unremarkable, but the local views of the hands demonstrated a solitary metastasis in the middle phalanx of the finger. This rare experience illustrates the need for including local views of extremities in a standard whole-body study.

Signaling pathways in renal cell carcinoma

Renal cell carcinoma (RCC), the most lethal type of genitourinary cancer, is generally resistant to chemotherapy and radiation therapy. Surgical excision of the tumor at a localized stage remains the mainstay for curative therapy. A number of drugs developed in recent years have shown limited to significant efficacy in treating RCC. These drugs act by blocking critical signaling pathways associated with RCC tumor growth and survival, and angiogenesis. Beyond well-validated signaling targets such as VHL, VEGFR and mTOR, additional pathways including HGF/c-MET and Wnt/β-catenin have emerged as important to RCC pathogenesis. Mutations in one or more components of these signaling networks may affect tumor response to therapy. This review summarizes the state of knowledge about signaling pathways in RCC and discusses the known genetic and epigenetic alterations that underlie dysregulation of these pathways.

Characterization of a new renal cell carcinoma bone metastasis mouse model

Metastatic bone disease caused by renal cell carcinoma (RCC) occurs frequently and becomes more and more prevalent presumably because survival times among patients with disseminated cancers are increasing. Patients with bone metastases from renal cell carcinoma suffer from severe pain, nerve compression syndromes and pathologic fractures. Very little is known about the mechanisms of skeletal metastases of RCC. Thus, to better understand the molecular mechanism of renal cell cancer (RCC) bone metastasis, it is crucial to develop new animal models. We have established a new animal model of RCC metastasis to bone by inoculation of human 786-O/luciferase cells into the left cardiac ventricle of athymic nude mice. The animals developed aggressive osteolytic bone destruction as monitored by radiography and micro-CT-scans with the mean endpoint at 62 +/- 8 days. The extensive bone destruction observed was comparable to the clinical setting and mainly occurred in hind limbs, forelimbs and the spine. The tumors were primarily located within the bone and resulted in destruction of cortical bone. No soft tissue metastases were detected by BLI or histomorphometry. To increase the bone-metastatic potential of the 786-O cell line, an in vivo selection was done yielding a subpopulation causing osteolytic lesions with the mean endpoint of 47 +/- 3 days. The selected subline secreted more proangiogenic factors VEGF and bFGF in vitro compared to the parental cell line suggesting that these tumors are highly vascular. This model provides a reliable reproduction of the clinical situation and therefore, is suitable for designing and evaluating more effective treatments for RCC bone metastasis.

Renal cell carcinoma bone metastases: clinical advances

Bone is a common site of metastatic spread in patients with advanced renal cell carcinoma (RCC) occurring in around one-third of patients enrolled in clinical trials evaluating modern systemic therapies for this disease. Until recently, limited systemic therapeutic options were available for advanced RCC. Nowadays, a quiver of agents have demonstrated activity, including compounds targeting the vascular endothelial growth factor (VEGF) axis and those targeting the mammalian target of rapamycin (mTOR). Despite a detailed biological understanding of how these drugs work, their effect on bony metastases is less clear. Data suggesting that bisphosphonates (namely zoledronic acid) benefit patients with bone metastases from advanced RCC was gathered prior to the targeted therapy era; therefore, there is some uncertainty about their role in patients on modern RCC therapies. This review summarizes the current targeted therapies registered for use in advanced RCC and postulates how some of them might affect the behavior of bone metastases. It also explores the data available on the role of bisphosphonates for bone metastases from RCC, describes methods of assessing response to therapy for bone metastases and delineates future expectations for the treatment of bone metastases from advanced RCC.

Influence of osteopontin short hairpin RNA on the proliferation and invasion of human renal cancer cells

The influence of short hairpin RNA (shRNA)-mediated osteopontin (OPN) gene silencing on the proliferation and invasion of human renal cancer ACHN cells was investigated. Four types of OPN shRNA recombinant plasmids were constructed and RT-PCR assays were used to screen the most highly functional shRNA recombinant plasmids, which were transferred into the cultured ACHN cells by Lipofectamine 2000. The cells transfected by shRNA expression vectors (ACHN/OPN) were visualized under an inverted microscope and screened by G418. Untreated cells (ACHN) and cells transfected by mock vectors (ACHN/Vect) were used as control groups. The expression levels of OPN mRNA and protein were detected by real-time PCR and Western blot respectively. The cell cycle and ratios of apoptotic cells were assessed by flow cytometry. MTT method was used for drawing the growth curve and observing cell proliferation in vitro. The abilities of migration and invasion in three groups were measured by Transwell chamber test. The expression levels of matrix metalloproteinase (MMP)-2 and MMP-9 in three groups were examined by Western blot. Our results showed that the recombinant plasmid could be successfully transferred into ACHN cells by Lipofectamine 2000. Compared with untreated cells, the expression levels of OPN mRNA and protein in ACHN/OPN cells were decreased by 59.68% and 76.42%, respectively (P<0.05), ACHN/OPN cells were blocked in S phase and apoptotic ratio increased significantly (P<0.05), however, no significant differences were found between ACHN/Vect and ACHN. Recombinant plasmid significantly attenuated expression levels of MMP-2 and MMP-9 proteins and suppressed the proliferation, migration, and invasion of ACHN cells. This study suggested that OPN may play an important role in the growth and invasion of human renal cancer ACHN cells, and these processes are correlated with the activations of MMP-2 and MMP-9. Our data provided preliminary experimental evidence for the feasibility of RNA interference technology in gene therapy of human renal cancer.