TGF-beta promotes the establishment of renal cell carcinoma bone metastasis

New players in the landscape of renal cell carcinoma bone metastasis and therapeutic opportunities

Approximately one-third of advanced renal cell carcinoma (RCC) patients develop osteolytic bone metastases, leading to skeletal complications. In this review, we first provide a comprehensive perspective of seminal studies on bone metastasis of RCC describing the main molecular modulators and growth factor signaling pathways most important for the RCC-stimulated osteoclast-mediated bone destruction. We next focus on newer developments revealing with in-depth details, the bidirectional interplay between renal cancer cells and the immune and stromal microenvironment that can through epigenetic reprogramming, profoundly affect the behaviors of transformed cells. Understanding their mechanistic interactions is of paramount importance for advancing both fundamental and translational research. These new investigations into the landscape of RCC-bone metastasis offer novel insights and identify potential avenues for future therapeutic interventions.

Antiangiogenic Tyrosine Kinase Inhibitors have Differential Efficacy in Clear Cell Renal Cell Carcinoma in Bone

Clear cell renal cell carcinoma (ccRCC) is the most prevalent kidney neoplasm; bone metastasis (BM) develops in 35% to 40% of metastatic patients and results in substantial morbidity and mortality, as well as medical costs. A key feature of ccRCC is the loss of function of the von Hippel-Lindau protein, which enhances angiogenesis via vascular endothelial growth factor release. Consequently, antiangiogenic tyrosine kinase inhibitors (TKI) emerged as a treatment for ccRCC. However, limited data about their efficacy in BM is available, and no systematic comparisons have been performed. We developed mouse models of bone and lung ccRCC tumors and compared their anticancer efficacy, impact on mouse survival, and mechanisms of action, including effects on tumor cells and both immune and nonimmune (blood vessels and osteoclasts) bone stromal components. This approach elucidates the efficacy of TKIs in ccRCC bone tumors to support rational interrogation and development of therapies.

SIGNIFICANCE

TKIs showed different efficacy in synchronous bone and lung metastases and did not eradicate tumors as single agents but induced extensive reprogramming of the BM microenvironment. This resulted in a significant decrease in neoangiogenic blood vessels, bone remodeling, and immune cell infiltration (including CD8 T cells) with altered spatial distribution.

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.

The Role of Cytokines in the Metastasis of Solid Tumors to the Spine: Systematic Review

Although many studies have investigated the role of cytokines in bone metastases, our knowledge of their function in spine metastasis is limited. Therefore, we performed a systematic review to map the available evidence on the involvement of cytokines in spine metastasis in solid tumors. A PubMed search identified 211 articles demonstrating a functional link between cytokines/cytokine receptors and bone metastases, including six articles confirming the role of cytokines/cytokine receptors in spine metastases. A total of 68 cytokines/cytokine receptors were identified to mediate bone metastases; 9 (mostly chemokines) played a role in spine metastases: CXC motif chemokine ligand (CXCL) 5, CXCL12, CXC motif chemokine receptor (CXCR) 4, CXCR6, interleukin (IL) 10 in prostate cancer, CX3C motif chemokine ligand (CX3CL) 1 and CX3C motif chemokine receptor (CX3CR) 1 in liver cancer, CC motif chemokine ligand (CCL) 2 in breast cancer, and transforming growth factor (TGF) β in skin cancer. Except for CXCR6, all cytokines/cytokine receptors were shown to operate in the spine, with CX3CL1, CX3CR1, IL10, CCL2, CXCL12, and CXCR4 mediating bone marrow colonization, CXCL5 and TGFβ promoting tumor cell proliferation, and TGFβ additionally driving bone remodeling. The number of cytokines/cytokine receptors confirmed to mediate spinal metastasis is low compared with the vast spectrum of cytokines/cytokine receptors participating in other parts of the skeleton. Therefore, further research is needed, including validation of the role of cytokines mediating metastases to other bones, to precisely address the unmet clinical need associated with spine metastases.

Analysis of genomes and transcriptomes of clear cell renal cell carcinomas identifies mutations and gene expression changes in the TGF-beta pathway

The occurrence of clear cell renal cell carcinoma (ccRCC) is related to changes in the transforming growth factor-β (TGF-β) signaling pathway. In this study, we adopted an integrated approach to identify and verify the effects of changes in this pathway on ccRCC and provide a guide for identifying new therapeutic targets. We performed transcriptome analysis of 539 ccRCC cases from The Cancer Genome Atlas (TCGA) and divided the samples into different TGF-β clusters according to unsupervised hierarchical clustering. We found that 76 of the 85 TGF-β pathway genes were dysregulated, and 55 genes were either protective or risk factors affecting the prognosis of ccRCC. The survival time of patients with tumors with low TGF-β scores was shorter than that of patients with tumors with high TGF-β scores. The overall survival (OS) of patients with ccRCC with high TGF-β scores was better than that of patients with low TGF-β scores. The TGF-β score correlated with the expression of key ccRCC and deacetylation genes. The sensitivity of tumor patients to targeted drugs differed between the high and low TGF-β score groups. Therefore, a prognostic model based on the TGF-β gene pathway can predict the prognosis of ccRCC patients. Grouping patients with ccRCC according to their TGF-β score is of great significance for evaluating the prognosis of patients, selecting targeted drugs, and identifying new therapeutic targets.

Jagged-1 is induced by mTOR inhibitors in renal cancer cells through an Akt/ALK5/Smad4-dependent mechanism

The mammalian target of rapamycin (mTOR) plays an important role in the aggressiveness and therapeutic resistance of many cancers. Targeting mTOR continues to be under clinical investigation for cancer therapy. Despite the notable clinical success of mTOR inhibitors in extending the overall survival of patients with certain malignancies including metastatic renal cell carcinomas (RCCs), the overall impact of mTOR inhibitors on cancers has been generally disappointing and attributed to various compensatory responses. Here we provide the first report that expression of the Notch ligand Jagged-1 (JAG1), which is associated with aggressiveness of RCCs, is induced by several inhibitors of mTOR (rapamycin (Rap), BEZ235, KU-0063794) in human clear cell RCC (ccRCC) cells. Using both molecular and chemical inhibitors of PI3K, Akt, and TGF-β signaling, we provide evidence that the induction of JAG1 expression by mTOR inhibitors in ccRCC cells depends on the activation of Akt and occurs through an ALK5 kinase/Smad4-dependent mechanism. Furthermore, we show that mTOR inhibitors activate Notch1 and induce the expression of drivers of epithelial-mesenchymal transition, notably Hic-5 and Slug. Silencing JAG1 with selective shRNAs blocked the ability of KU-0063794 and Rap to induce Hic-5 in ccRCC cells. Moreover, Rap enhanced TGF-β-induced expression of Hic-5 and Slug, both of which were repressed in JAG1-silenced ccRCC cells. Silencing JAG1 selectively decreased the motility of ccRCC cells treated with Rap or TGF-β1. Moreover, inhibition of Notch signaling with γ-secretase inhibitors enhanced or permitted mTOR inhibitors to suppress the motility of ccRCC cells. We suggest targeting JAG1 may enhance therapeutic responses to mTOR inhibitors in ccRCCs.

Kidney Cancer Models for Pre-Clinical Drug Discovery: Challenges and Opportunities

Renal cell carcinoma (RCC) is among the most lethal urological malignancies once metastatic. The introduction of immune checkpoint inhibitors has revolutionized the therapeutic landscape of metastatic RCC, nevertheless, a significant proportion of patients will experience disease progression. Novel treatment options are therefore still needed and in vitro and in vivo model systems are crucial to ultimately improve disease control. At the same time, RCC is characterized by a number of molecular and functional peculiarities that have the potential to limit the utility of pre-clinical model systems. This includes not only the well-known genomic intratumoral heterogeneity (ITH) of RCC but also a remarkable functional ITH that can be shaped by influences of the tumor microenvironment. Importantly, RCC is among the tumor entities, in which a high number of intratumoral cytotoxic T cells is associated with a poor prognosis. In fact, many of these T cells are exhausted, which represents a major challenge for modeling tumor-immune cell interactions. Lastly, pre-clinical drug development commonly relies on using phenotypic screening of 2D or 3D RCC cell culture models, however, the problem of “reverse engineering” can prevent the identification of the precise mode of action of drug candidates thus impeding their translation to the clinic. In conclusion, a holistic approach to model the complex “ecosystem RCC” will likely require not only a combination of model systems but also an integration of concepts and methods using artificial intelligence to further improve pre-clinical drug discovery.

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.

SPARC is a key mediator of TGF-β-induced renal cancer metastasis

Aberrant expression of transforming growth factor-β1 (TGF-β1) is associated with renal cell carcinoma (RCC) progression by inducing cancer metastasis. However, the downstream effector(s) in TGF-β signaling pathway is not fully characterized. In the present study, the elevation of secreted protein acidic and rich in cysteine (SPARC) as a TGF-β regulated gene in RCC was identified by applying differentially expressed gene analysis and microarray analysis, we further confirmed this result in several RCC cell lines. Clinically, the expression of these two genes is positively correlated in RCC patient specimens. Furthermore, elevated SPARC expression is found in all the subtypes of RCC and positively correlated with the RCC stage and grade. In contrast, SPARC expression is inversely correlated with overall and disease-free survival of patients with RCC, suggesting SPARC as a potent prognostic marker of RCC patient survival. Knocking down SPARC significantly inhibits RCC cell invasion and metastasis both in vitro and in vivo. Similarly, in vitro cell invasion can be diminished by using a specific monoclonal antibody. Mechanistically, SPARC activates protein kinase B (AKT) pathway leading to elevated expression of matrix metalloproteinase-2 that can facilitate RCC invasion. Altogether, our data support that SPARC is a critical role of TGF-β signaling network underlying RCC progression and a potential therapeutic target as well as a prognostic marker.

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.

Calcitriol inhibits migration and invasion of renal cell carcinoma cells by suppressing Smad2/3-, STAT3- and β-catenin-mediated epithelial-mesenchymal transition

Low vitamin D status is associated with progression in patients with renal cell carcinoma (RCC). The present study found that vimentin, a mesenchymal marker, was accordingly upregulated, and E-cadherin, an epithelial marker, was downregulated in RCC patients with low vitamin D status. Thus, we investigated the effects of calcitriol or vitamin D3, an active form of vitamin D, on epithelial-mesenchymal transition (EMT) in RCC cells. RCC cells were treated by two models. In model 1, three RCC cell lines, ACHN, 786-O and CAKI-2, were incubated with either LPS (2.0 μg/mL) or transforming growth factor (TGF)-β1 (10 ng/mL) in the presence or absence of calcitriol (200 nmol/L). In model 2, two RCC cell lines, ACHN and CAKI-2, were incubated with calcitriol (200 nmol/L) only. Calcitriol inhibited migration and invasion not only in TGF-β1-stimulated but also in TGF-β1-unstimulated RCC cells. Moreover, calcitriol suppressed E-cadherin downregulation and vimentin upregulation not only in TGF-β1-stimulated but also in TGF-β1-unstimulated ACHN and CAKI-2 cells. Calcitriol attenuated LPS-induced upregulation of MMP-2, MMP-7, MMP-9, MMP-26 and urokinase-type plasminogen activator (u-PA) in ACHN cells. In addition, calcitriol blocked TGF-β1-induced nuclear translocation of ZEB1, Snail and Twist1 in ACHN and CAKI-2 cells. Mechanistically, calcitriol suppressed EMT through different signaling pathways: (i) calcitriol suppressed Smad2/3 phosphorylation by reinforcing physical interaction between vitamin D receptor (VDR) and Smad3 in TGF-β1-stimulated RCC cells; (ii) calcitriol inhibited signal transducer and activator of transcription (STAT)3 activation in LPS-stimulated RCC cells; (iii) calcitriol inhibited β-catenin/TCF-4 activation by promoting integration of VDR with β-catenin in TGF-β1-unstimulated RCC cells. Taken together, calcitriol inhibits migration and invasion of RCC cells partially by suppressing Smad2/3-, STAT3- and β-catenin-mediated EMT.

TGF-β and microRNA Interplay in Genitourinary Cancers

Genitourinary cancers (GCs) include a large group of different types of tumors localizing to the kidney, bladder, prostate, testis, and penis. Despite highly divergent molecular patterns, most GCs share commonly disturbed signaling pathways that involve the activity of TGF-β (transforming growth factor beta). TGF-β is a pleiotropic cytokine that regulates key cancer-related molecular and cellular processes, including proliferation, migration, invasion, apoptosis, and chemoresistance. The understanding of the mechanisms of TGF-β actions in cancer is hindered by the "TGF-β paradox" in which early stages of cancerogenic process are suppressed by TGF-β while advanced stages are stimulated by its activity. A growing body of evidence suggests that these paradoxical TGF-β actions could result from the interplay with microRNAs: Short, non-coding RNAs that regulate gene expression by binding to target transcripts and inducing mRNA degradation or inhibition of translation. Here, we discuss the current knowledge of TGF-β signaling in GCs. Importantly, TGF-β signaling and microRNA-mediated regulation of gene expression often act in complicated feedback circuits that involve other crucial regulators of cancer progression (e.g., androgen receptor). Furthermore, recently published in vitro and in vivo studies clearly indicate that the interplay between microRNAs and the TGF-β signaling pathway offers new potential treatment options for GC patients.

Meta-analysis of gene expression and integrin-associated signaling pathways in papillary renal cell carcinoma subtypes

Papillary renal cell carcinoma (PRCC) is the second most common renal cell carcinoma (RCC) that can be further subdivided into type 1 (PRCC1) and type 2 (PRCC2) RCCs based on histological and genetic features. PRCC2 is often more aggressive than PRCC1. While integrin-associated protein complexes mediate tumorigenesis and metastases in many types of cancers it is not known whether integrin-mediated signaling impacts PRCC and differs between PRCC1 and PRCC2. In this study, we combined the analysis of five PRCC gene expression datasets derived from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) by using integrative bioinformatics pipelines. We found 1475 differentially expressed genes among which 37 genes were associated with integrin pathways. In comparison with PRCC1, PRCC2 cases showed upregulated expression of α5-integrin (ITGA5) whereas the expression of α6- (ITGA6) and β8-integrins (ITGB8) was downregulated. Because PRCC2 occurs more frequently in men, the meta-analysis was extended to explore the gender effects. This analysis revealed 8 genes but none of them was related to integrin pathways suggesting that other mechanisms than integrin-mediated signaling underlie the observed gender differences in the pathogenicity of PRCC2.

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.

[Bone metastasis by renal cell carcinoma. Importance of calcium and calcium-sensing receptor]

Bone tissue is one of the main locations of metastases in renal cell carcinoma (RCC). In bone tissue the concentration of calcium ions is very high. Cells recognize extracellular calcium by the calcium-sensing receptor (CaSR). To investigate the role of calcium in bone metastases, the CaSR was quantified in tumor tissue and primary tumor cells of patients who were free of metastases or developed bone or lung metastases during a time period of 5 years after nephrectomy. In tissue specimens and primary cells of patients developing bone metastases, CaSR expression was clearly enhanced. Functionally, analyses showed a higher sensitivity in bone metastasizing cells concerning proliferation and chemotactical migration. These effects were caused by enhanced activity of the downstream targets of CaSR, namely AKT, PLCg, JNK and p38, analyzed in a phospho-kinase array and western blot analysis. The extent to which CaSR is suitable as a new marker for bone-specific metastases from renal cancer must be examined further.

Expression of Genes Involved in Cellular Adhesion and Extracellular Matrix Remodeling Correlates with Poor Survival of Patients with Renal Cancer

PURPOSE

Renal cell carcinoma is the most common highly metastatic kidney malignancy. Adhesion has a crucial role in the metastatic process. TGF (transforming growth factor)-β1 is a pleiotropic cytokine that influences cancerous transformation. We hypothesized that 1) changes in the expression of adhesion related genes may influence survival rate of patients with renal cell carcinoma and 2) TGF-β1 may contribute to changed expression of adhesion related genes.

MATERIALS AND METHODS

Two-step quantitative real-time polymerase chain reaction arrays were used to analyze the expression of adhesion related genes in 77 tumors and matched pair controls. The prognostic significance of genes was evaluated in TCGA (The Cancer Genome Atlas) data on 468 patients with renal cell carcinoma. Quantitative real-time polymerase chain reaction and Western blot were applied for TGF-β1 analysis. TGF-β1 mediated regulation of gene expression was analyzed by TGF-β1 supplementation of Caki-2 cells and quantitative real-time polymerase chain reaction.

RESULTS

The expression of 19 genes related to adhesion and extracellular matrix remodeling was statistically significantly disturbed in renal cell carcinoma compared with controls. The 10-gene expression signature (COL1A1, COL5A1, COL11A1, FN1, ICAM1, ITGAL, ITGAM, ITGB2, THBS2 and TIMP1) correlated with poor survival (HR 2.85, p = 5.7e-10). TGF-β1 expression was 22 times higher in renal cell carcinoma than in controls (p <0.0001). TGF-β1 induced expression of TGFBI, COL1A1, COL5A1, COL8A1, FN1, ITGA5, ITGAM and TIMP1 in a renal cell carcinoma derived cell line.

CONCLUSIONS

Disturbed expression of genes involved in adhesion and extracellular matrix remodeling develops early during renal cell carcinoma carcinogenesis and correlates with poor survival. TGF-β1 contributes to changed expression of extracellular matrix and adhesion related genes. Bioinformatic analysis performed on a broad panel of cancers of nonkidney origin suggests that disturbed expression of genes related to extracellular matrix and adhesion may be a universal feature of cancerous progression.

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.

Hyaluronan and its function as an unspecific regulator of cell-bound receptors

In a former study on primary mesangial cells a regulatory function of hyaluronan (HA) was shown. HA is the backbone of a cell-bound jelly-barrier. The thickness of that cell-bound jelly-barrier regulates the access of ligands to their cellular receptors in an unspecific way. The thickness of that barrier is reduced by degradation of HA. The hypothesis was that this regulatory mechanism is not restricted to mesangial cells, but applies for other cell types as well. A selective and topic oriented review of the literature was performed to collect references, which support the impression, that this unspecific mechanism of receptor-regulation by HA is not restricted to primary mesangial cells. On the basis of the data from the review of the literature it was concluded that the regulatory mechanism of HA also applies for other than mesangial cells. On the basis of the said mechanism it was concluded that a tissue-specific regulation of HA on the cell surface might be relevant in therapy, especially in chronic diseases.

Combined Influence of EGF+61G>A and TGFB+869T>C Functional Polymorphisms in Renal Cell Carcinoma Progression and Overall Survival: The Link to Plasma Circulating MiR-7 and MiR-221/222 Expression

The epidermal growth factor (EGF) is responsible for the activation of intracellular signal transducers that act on cell-cycle progression, cell motility, angiogenesis and inhibition of apoptosis. However, cells can block these effects activating opposite signaling pathways, such as the transforming growth factor beta 1 (TGFβ1) pathway. Thus changes in expression levels of EGF and TGFB1 in renal cells might modulate the renal cell carcinoma (RCC) development, in consequence of changes in regulatory elements of signaling networks such as the microRNAs (miRNAs). Our purpose was to investigate the synergic role of EGF+61G>A and TGFB1+869T>C polymorphisms in RCC development. Genetic polymorphisms were studied by allelic discrimination using real-time PCR in 133 RCC patients vs. 443 healthy individuals. The circulating EGF/EGFR-MAPK-related miR-7, miR-221 and miR-222 expression was analyzed by a quantitative real-time PCR in plasma from 22 RCC patients vs. 27 healthy individuals. The intermediate/high genetic proliferation profile patients carriers present a significantly reduced time-to-progression and a higher risk of an early relapse compared with the low genetic proliferation profile carriers (HR = 8.8, P = 0.038) with impact in a lower overall survival (Log rank test, P = 0.047). The RCC patients presented higher circulating expression levels of miR-7 than healthy individuals (6.1-fold increase, P<0.001). Moreover, the intermediate/high genetic proliferation profile carriers present an increase in expression levels of miR-7, miR-221 and miR-222 during the RCC development and this increase is not observed in low genetic proliferation profile (P<0.001, P = 0.004, P<0.001, respectively). The stimulus to angiogenesis, cell-cycle progression and tumoral cells invasion, through activation of EGFR/MAPK signaling pathway in intermediate/high proliferation profile carriers is associated with an early disease progression, resulting in a poor overall survival. We also demonstrated that the intermediate/high proliferation profile is an unfavorable prognostic factor of RCC and miR-7, miR-221 and miR-222 expressions may be useful phenotype biomarkers of EGFR/MAPK activation.

LOXL2 status correlates with tumor stage and regulates integrin levels to promote tumor progression in ccRCC

Clear cell renal cell carcinoma (ccRCC) is the most common histologically defined subtype of renal cell carcinoma (RCC). To define the molecular mechanism in the progression of ccRCC, we focused on LOX-like protein 2 (LOXL2), which is critical for the first step in collagen and elastin cross-linking. Using exon array analysis and quantitative validation, LOXL2 was shown to be significantly upregulated in clinical specimens of human ccRCC tumor tissues, compared with adjacent noncancerous renal tissues, and this elevated expression correlated with the pathologic stages of ccRCC. RNAi-mediated knockdown of LOXL2 resulted in marked suppression of stress-fiber and focal adhesion formation in ccRCC cells. Moreover, LOXL2 siRNA knockdown significantly inhibited cell growth, migration, and invasion. Mechanistically, LOXL2 regulated the degradation of both integrins α5 (ITGAV5) and β1 (ITGB1) via protease- and proteasome-dependent systems. In clinical ccRCC specimens, the expression levels of LOXL2 and integrin α5 correlated with the pathologic tumor grades. In conclusion, LOXL2 is a potent regulator of integrin α5 and integrin β1 protein levels and functions in a tumor-promoting capacity in ccRCC.

IMPLICATIONS

This is the first report demonstrating that LOXL2 is highly expressed and involved in ccRCC progression by regulating the levels of integrins α5 and β1.

Ki-67, TGF-β1, and elastin content are significantly altered in lip carcinogenesis

Epithelial changes observed in actinic cheilitis (AC) and lower lip squamous cell carcinoma (LLSCC) have been studied using different markers in order to observe diagnostic and prognostic factors for both lesions. The aim of the present study was to analyze Ki-67, TGF-β1, and elastin content in AC and LLSCC to determine the possible role of these proteins in lip carcinogenesis. Medical records of 29 cases of AC and 53 cases of LLSCC were analyzed. Lesions were classified according histological pattern and submitted to immunostaining for Ki-67, TGF-β1, and elastin. Different percentages of Ki-67-positive cells were found in AC depending on the degree of epithelial dysplasia (p < 0.01). An association was also found between the percentage of Ki-67-positive cells and tumor grade in LLSCC (p < 0.01). An inverse correlation was found between Ki-67 and TGF-β1 in AC and LLSCC (p < 0.01). Elastosis was thinner and more discontinuous in LLSCC in comparison to AC, and this difference in the elastin immunolabeling pattern was statistically significant between groups (p < 0.01). The present findings indicate that changes in Ki-67 and TGF-β1 content contribute to lip carcinogenesis. Furthermore, elastin content reflects changes in the extracellular matrix in both AC and LLSCC.

Emerging role of tumor-associated macrophages as therapeutic targets in patients with metastatic renal cell carcinoma

Tumor-associated macrophages (TAMs) derived from peripheral blood monocytes recruited into the renal cell carcinoma (RCC) microenvironment. In response to inflammatory stimuli, macrophages undergo M1 (classical) or M2 (alternative) activation. M1 cells produce high levels of inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-12, IL-23 and IL-6, while M2 cells produce anti-inflammatory cytokines, such as IL-10, thus contributing to RCC-related immune dysfunction. The presence of extensive TAM infiltration in RCC microenvironment contributes to cancer progression and metastasis by stimulating angiogenesis, tumor growth, and cellular migration and invasion. Moreover, TAMs are involved in epithelial-mesenchymal transition of RCC cancer cells and in the development of tumor resistance to targeted agents. Interestingly, macrophage autophagy seems to play an important role in RCC. Based on this scenario, TAMs represent a promising and effective target for cancer therapy in RCC. Several strategies have been proposed to suppress TAM recruitment, to deplete their number, to switch M2 TAMs into antitumor M1 phenotype and to inhibit TAM-associated molecules. In this review, we summarize current data on the essential role of TAMs in RCC angiogenesis, invasion, impaired anti-tumor immune response and development of drug resistance, thus describing the emerging TAM-centered therapies for RCC patients.

The Dual Role of TGFβ in Human Cancer: From Tumor Suppression to Cancer Metastasis

The transforming growth factor-beta (TGFβ) superfamily encompasses widespread and evolutionarily conserved polypeptide growth factors that regulate and orchestrate growth and differentiation in all cell types and tissues. While they regulate asymmetric cell division and cell fate determination during early development and embryogenesis, TGFβ family members play a major regulatory role in hormonal and immune responses, cell growth, cell death and cell immortalization, bone formation, tissue remodeling and repair, and erythropoiesis throughout adult life. The biological and physiological functions of TGFβ, the founding member of this family, and its receptors are of central importance to human diseases, particularly cancer. By regulating cell growth, death, and immortalization, TGFβ signaling pathways exert tumor suppressor effects in normal cells and early carcinomas. Thus, it is not surprising that a high number of human tumors arise due to mutations or deletions in the genes coding for the various TGFβ signaling components. As tumors develop and progress, these protective and cytostatic effects of TGFβ are often lost. TGFβ signaling then switches to promote cancer progression, invasion, and tumor metastasis. The molecular mechanisms underlying this dual role of TGFβ in human cancer will be discussed in depth in this paper, and it will highlight the challenge and importance of developing novel therapeutic strategies specifically aimed at blocking the prometastatic arm of the TGFβ signaling pathway without affecting its tumor suppressive effects.

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.

The notch and TGF-β signaling pathways contribute to the aggressiveness of clear cell renal cell carcinoma

Background

Despite recent progress, therapy for metastatic clear cell renal cell carcinoma (CCRCC) is still inadequate. Dysregulated Notch signaling in CCRCC contributes to tumor growth, but the full spectrum of downstream processes regulated by Notch in this tumor form is unknown.

Methodology/Principal Findings

We show that inhibition of endogenous Notch signaling modulates TGF-β dependent gene regulation in CCRCC cells. Analysis of gene expression data representing 176 CCRCCs showed that elevated TGF-β pathway activity correlated significantly with shortened disease specific survival (log-rank test, p = 0.006) and patients with metastatic disease showed a significantly elevated TGF-β signaling activity (two-sided Student's t-test, p = 0.044). Inhibition of Notch signaling led to attenuation of both basal and TGF-β1 induced TGF-β signaling in CCRCC cells, including an extensive set of genes known to be involved in migration and invasion. Functional analyses revealed that Notch inhibition decreased the migratory and invasive capacity of CCRCC cells.

Conclusion

An extensive cross-talk between the Notch and TGF-β signaling cascades is present in CCRCC and the functional properties of these two pathways are associated with the aggressiveness of this disease.

Potential prognostic biomarkers for bone metastasis from hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) most commonly develops in patients who have a viral infection, especially in the case of hepatitis B virus (HBV), and in patients with a chronic liver disease. HCC patients with bone metastasis (BM) suffer from pain and other symptoms that significantly reduce their quality of life. Identification of patients who are at high risk for BM after undergoing potentially curative treatment for HCC remains challenging. Here, we aimed to identify HCC BM-related genes and proteins to establish prediction biomarkers.

METHODS

RNA was extracted from 48 pairs of intratumoral and peritumoral formalin-fixed, paraffin-embedded tissue from HCC patients with and without BM. A cDNA-mediated annealing, selection, extension and ligation assay containing 502 cancer-related genes was used to identify novel BM-associated genes. An additional independent study with 350 HCC patients who had undergone hepatectomy was conducted to evaluate the expression of candidate genes at the protein level using immunohistochemistry on tissue microarrays (TMAs). Of the 350 patients, 273 (78.0%) were infected with HBV.

RESULTS

Seven intratumoral genes and 17 peritumoral genes were overexpressed in patients with BM, whereas 15 intratumoral genes and 28 peritumoral genes were underexpressed in patients with BM. We selected the following four genes for further analysis because they were differentially expressed in the cancer gene-specific microarray and were previously reported to be associated with BM: connective tissue growth factor (CTGF), matrix metalloproteinase-1 (MMP-1), transforming growth factor β1 (TGF-β1), and interleukin-11 (IL-11). We assessed the protein expression of these selected genes using immunohistochemistry on TMAs including 350 HCC patient specimens. We determined that expression of intratumoral CTGF, intratumoral IL-11, and peritumoral MMP-1 were independent prognostic factors for developing BM in HCC patients. Combining intratumoral CTGF and IL-11 expression was also an independent risk factor for BM development.

CONCLUSIONS

Sixty-seven genes were differentially expressed in HCC patients with and without BM. High intratumoral CTGF, positive IL-11, and high peritumoral MMP-1 expression were associated with BM after hepatectomy. Intratumoral CTGF expression combined with IL-11 expression may serve as a useful predictive biomarker for HCC BM.

Maintenance of phenotype and function of cryopreserved bone-derived cells

The emerging fields of tissue engineering and regenerative medicine require large numbers of cells for therapy. Although the properties of cells obtained from a variety of fresh tissues have been delineated, the knowledge regarding cryopreserved grafts-derived cells remains elusive. Previous studies have shown that living cells could be isolated from cryopreserved bone grafts. However, whether cryopreserved bone-derived cells can be applied in regenerative medicine is largely unknown. The present study was to evaluate the potential application of cryopreserved grafts-derived cells for tissue regeneration. We showed that cells derived from cryopreserved bone grafts could maintain good proliferation activity and osteogenic phenotype. The biological phenotype of these cells could be well preserved. The transplantation of cryopreserved bone-derived cells on scaffold could promote new bone formation in nude mice and enhance the osteointegration for dental implants in canine, which confirmed their osteogenic capacity, and showed that cells derived from cryopreserved bone were comparable to that of fresh bone in terms of the ability to promote osteogenesis in vivo. This work demonstrates that cryopreserved bone grafts may represent a novel, accessible source of cells for tissue regeneration therapy, and the results of our study may also stimulate the development of other cryopreservation techniques in basic and clinical studies.

Matrix metalloproteinases as master regulators of the vicious cycle of bone metastasis

Bone remodeling is a delicate balancing act between the bone matrix synthesizing osteoblasts and bone resorbing osteoclasts. Active bone metastases typically subvert this process to generate lesions that are comprised of extensive areas of pathological osteogenesis and osteolysis. The resultant increase in bone matrix remodeling enhances cytokine/growth factor bioavailability thus creating a vicious cycle that stimulates tumor progression. Given the extent of matrix remodeling occurring in the tumor-bone microenvironment, the expression of matrix metalloproteinases (MMPs) would be expected, since collectively they have the ability to degrade all components of the extracellular matrix (ECM). However, in addition to being "matrix bulldozers", MMPs control the bioavailability and bioactivity of factors such as RANKL and TGFβ that have been described as crucial for tumor-bone interaction, thus implicating MMPs as key regulators of the vicious cycle of bone metastases.

RNA interference-directed caveolin-1 knockdown sensitizes SN12CPM6 cells to doxorubicin-induced apoptosis and reduces lung metastasis

Human renal cell carcinoma (HRCC) is characterized by a high level of resistance to all treatment modalities. Therefore, the investigation of global gene expression in HRCC might help understand its biologic behavior and develop treatment strategies. Using cDNA microarray analysis, we initially compared gene expression profiles between HRCCs and adjacent normal tissues, and found that 87 were up-regulated and 127 genes were down-regulated. Next, a subset of genes, twofold differentially expressed, were validated by Northern blotting. Unexpectedly, caveolin-1, a gene reported to be a tumor suppressor gene, was found to be up-regulated in HRCC tissues. Expression level of caveolin-1 in SN12CPM6 (high metastatic clone) was higher than in SN12C (low metastatic clone), and SN12CPM6 was more resistant to doxorubicin (DXR) than SN12C. Caveolin-1 gene was slightly induced in surviving SN12C cells after DXR treatment. Furthermore, SN12CPM6-siCav1 cells, which were transfected with siRNA of cavelon-1 gene, were more sensitive to DXR, compared to SN12CPM6, but reduction of caveolin-1 gene expression did not affect tumor formation in subcapsule of kidney and lung metastasis. On the other hand, induction of caveolin-1 gene affected the production of lung metastasis under anti-cancer drug treatment: the incidence of pulmonary metastasis was significantly lower in SCID mice injected with SN12CPM6-siCav1 cells, and the number of pulmonary nodules decreased significantly (p = 0.0004). The above results together suggest that caveolin-1 may confer a growth advantage to cancer cells during DXR chemotherapy and surviving HRCC cells eventually might develop lung metastasis.

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.

Activin A promotes multiple myeloma-induced osteolysis and is a promising target for myeloma bone disease

Understanding the pathogenesis of cancer-related bone disease is crucial to the discovery of new therapies. Here we identify activin A, a TGF-beta family member, as a therapeutically amenable target exploited by multiple myeloma (MM) to alter its microenvironmental niche favoring osteolysis. Increased bone marrow plasma activin A levels were found in MM patients with osteolytic disease. MM cell engagement of marrow stromal cells enhanced activin A secretion via adhesion-mediated JNK activation. Activin A, in turn, inhibited osteoblast differentiation via SMAD2-dependent distal-less homeobox-5 down-regulation. Targeting activin A by a soluble decoy receptor reversed osteoblast inhibition, ameliorated MM bone disease, and inhibited tumor growth in an in vivo humanized MM model, setting the stage for testing in human clinical trials.

Efficacy of targeted therapy in patients with renal cell carcinoma with pre-existing or new bone metastases

INTRODUCTION

This single-centre retrospective analysis of data from three randomised studies and two expanded-access studies compared the effect of interferon (IFN)-alfa, sunitinib, and sorafenib on the occurrence and progression of metastatic bone lesions in patients with renal cell carcinoma (RCC).

METHODS

The analysis included 292 patients: 107 received sunitinib 50 mg/day in 6-week cycles (Schedule 4/2), 147 received sorafenib 800 mg/day, and 38 received placebo or IFN-alfa 9 MU t.i.w.

RESULTS

Pre-existing metastatic bone lesions were reported in 82 patients, of which 30 experienced progression. Twenty-three of 210 patients developed new bone lesions. Overall, sunitinib appeared slightly more effective than sorafenib or IFN-alfa at extending mean time to progression of pre-existing bone lesions (P = 0.057). Compared with sorafenib, sunitinib significantly decreased formation (P = 0.034) and prolonged time to occurrence of new bone lesions (P = 0.047).

CONCLUSION

Further evaluation of the effect of these therapies on bone metastases in RCC is warranted.

Identification of prospective factors promoting osteotropism in breast cancer: a potential role for CITED2

Breast cancer metastases develop in the bone more frequently than any other site and are a common cause of morbidity in the form of bone pain, pathological fractures, nerve compression and life-threatening hypercalcemia. Despite ongoing research efforts, the molecular and cellular mechanisms that regulate breast cancer cell homing to and colonization of the bone as well as resultant pathological bone alteration remain poorly understood. To identify key mediators promoting breast cancer metastasis to bone, we utilized an immunocompetent, syngeneic murine model of breast cancer metastasis employing the mammary tumor cell line NT2.5. Following intracardiac injection of NT2.5 cells in neu-N mice, metastases developed in the bone, liver and lung, closely mimicking the anatomical distribution of metastases in patients with breast cancer. Using an in vivo selection process, we established NT2.5 sublines demonstrating an enhanced ability to colonize the bone and liver. Genome-wide cDNA microarray analysis comparing gene expression between parental NT2.5 cells and established sublines revealed both known and novel mediators of bone metastasis and osteolysis, including the transcriptional co-activator CITED2. In further studies, we found that expression of CITED2 was elevated in human primary breast tumors and bone metastasis compared to normal mammary epithelium and was highest in breast cancer cell lines that cause osteolytic bone metastasis in animal models. In addition, reducing CITED2 expression in NT2.5 cells inhibited the establishment of bone metastasis and osteolysis in vivo, suggesting a potential role for CITED2 in promoting breast cancer bone metastasis.

Immunotherapy for human renal cell carcinoma by adoptive transfer of autologous transforming growth factor beta-insensitive CD8+ T cells

PURPOSE

Transforming growth factor-beta (TGF-beta) is a potent immunosuppressor that has been associated with tumor evasion from the host immune surveillance and, thus, tumor progression. We tested a novel immunotherapy for human renal cell cancer (RCC) using a technique that involves the adoptive transfer of autologous tumor-reactive, TGF-beta-insensitive CD8(+) T cells into human RCC-challenged immunodeficient mice to identify its potent antitumor responses.

EXPERIMENTAL DESIGN

The present study was conducted using a one-to-one adoptive transfer strategy to treat tumor-bearing severe combined immunodeficient (SCID/beige) mouse. The SCID/beige mice were humanized with peripheral blood mononuclear cells from patients with RCC (Hu-PBMC-SCID) before adoptive transfer. Autologous CD8(+) T cells were expanded ex vivo using autologous patient's dendritic cells pulsed with the tumor lysate and rendered TGF-beta insensitive by dominant-negative TGF-beta type II receptor. In addition, human RCC cell lines were generated using patients' tumor cells injected into SCID/beige mice.

RESULTS

Using flow cytometry analysis, we confirmed the expression of the tumor-reactive, TGF-beta-insensitive CD8(+) T cells were the effector CD8(+) cells (CD27(-)CDRA(+)). Adoptive transfer of autologous TGF-beta-insensitive CD8(+) T cells into tumor-bearing Hu-PBMC-SCID mice induced robust tumor-specific CTL responses in vitro, were associated with tumor apoptosis, suppressed lung metastasis, and prolonged survival times in vivo.

CONCLUSION

The one-to-one adoptive transfer strategy is an ideal in vivo murine model for studying the relationship between TGF-beta and immunosurveillance in RCC in vivo. Furthermore, this technique may offer the promise of a novel therapeutic option for the treatment of human patients with RCC.

Systemic IGF-I administration stimulates the in vivo growth of early, but not advanced, renal cell carcinoma

Insulin-like growth factor I (IGF-I) is a potent mitogen and antiapoptotic factor. Although elevated serum IGF-I levels have been associated with increased cancer risk, it is not yet clear whether IGF-I sensitivity is sustained throughout tumor progression. To evaluate the biological effects of IGF-I during renal cell carcinoma (RCC) establishment and progression, we administered recombinant human IGF-I to severe combined immuno-deficient mice bearing early or more established Caki-2 human RCC tumors. IGF-I significantly enhanced the tumor growth 2.4-fold when administered early after tumor inoculation. This IGF-I-induced growth was accompanied with enhanced tumor cell proliferation, tumor vascularization, as well as increased intratumoral insulin-like growth factor binding protein 3 (IGFBP-3) and pSmad2 levels. In contrast, IGF-I administrated to more established RCC tumors showed no effect on tumor growth, with subsequently much lower Ki-67, IGFBP-3 and pSmad2 levels. Taken together, these data suggest that systemic IGF-I has potent actions during early RCC tumor development with a sustained long-term effect on proliferation and neovascularization although with progression, later tumors appear to become desensitized to systemic IGF-I effects.

MMP-13 is over-expressed in renal cell carcinoma bone metastasis and is induced by TGF-beta1

Bone metastasis occurs frequently in renal cell carcinoma (RCC) patients causing significant morbidity by stimulating excessive osteolysis, yet the mechanisms responsible have been little studied. Matrix metalloproteinases (MMPs) are over-expressed in many cancer types and are believed to play a role in bone metastasis, however, the expression of MMPs in RCC bone metastasis (RBM) has not been investigated. Due to their ability to degrade the main component of organic bone matrix, type I collagen, we investigated the expression of MMP-1, -2, -8, -9, and -13 in RBM. By quantitative (q)RT-PCR, expression of MMP-13 was significantly increased in RBM tissues relative to that in RCC and adjacent normal kidney while no differences in the expression of MMP-1, -2, -8, or -9 mRNA were observed. Correspondingly, increased expression of MMP-13 protein was also observed in RBM relative to RCC by immunohistochemical analysis. Intriguingly, the expression of MMP-13 in the human RBM cell line RBM1-IT4 was stimulated by TGF-beta1, a growth factor abundant in the bone microenvironment and known to promote RBM-induced osteolysis in animals. Exposure of RBM1-IT4 cells to TGF-beta1 increased MMP-13 mRNA levels as well as the latent and active forms of MMP-13 protein. Further, stable expression of a dominant-negative TGF-beta type II receptor in RBM1-IT4 cells inhibited MMP-13 expression following TGF-beta1 exposure. These data suggest that MMP-13 expression is elevated in RBM relative to primary RCC and adjacent normal kidney, and is regulated at the cellular level by TGF-beta1.

TGFbeta in Cancer

The transforming growth factor beta (TGFbeta) signaling pathway is a key player in metazoan biology, and its misregulation can result in tumor development. The regulatory cytokine TGFbeta exerts tumor-suppressive effects that cancer cells must elude for malignant evolution. Yet, paradoxically, TGFbeta also modulates processes such as cell invasion, immune regulation, and microenvironment modification that cancer cells may exploit to their advantage. Consequently, the output of a TGFbeta response is highly contextual throughout development, across different tissues, and also in cancer. The mechanistic basis and clinical relevance of TGFbeta's role in cancer is becoming increasingly clear, paving the way for a better understanding of the complexity and therapeutic potential of this pathway.

Distribution of murine adipose-derived mesenchymal stem cells in vivo following transplantation in developing mice

Systemic delivery of mesenchymal stem cells (MSCs) or stromal cells in vivo is attractive because it offers means of disseminating therapeutic cells to various tissues and organs in vivo. In the present study, we investigated the distribution and engraftment of the murine adipose-derived mesenchymal stem cells (ADSCs) without exposure to or exposed to bone microenvironment or transforming growth factor-beta1 (TGF-beta1) prior to transplantation into developing mice. The ADSCs harvested from the murine inguinal fat pad exhibited potential for differentiation toward osteogenic and adipogenic cell lineages in vitro. Fourteen days after systemic transplantation of the ADSCs marked with enhanced green fluorescent protein (EGFP) into developing mice, minimal donor GFP(+) cells were detected in the skeletal tissues in a limited number of the recipient mice. Exposure of the ADSCs to bone microenvironment for 7 or 14 days prior to transplantation into developing mice enhanced their migration and survival in the bones of the recipient mice. Exposure of ADSCs to TGF-beta1 prior to systemic transplantation exerted similar effects on cell migration and engraftment in various tissues, including the bones of the recipient developing mice. At 28 days following systemic transplantation, the ADSCs exposed to bone microenvironment were restricted mostly to the skeletal tissues of the recipient mice. Donor cells retrieved from the bones of the recipient mice at 28 days following cell transplantation expressed the differentiation markers Runx2 and Osterix (Osx). These data suggest that exposure of ADSCs to bone microenvironment or to TGF-beta1 prior to transplantation enhances their survival in the skeletal tissues following transplantation.

Sorafenib for metastatic renal cancer: the Princess Margaret experience

OBJECTIVE

Sorafenib, an oral multikinase inhibitor, prolonged progression-free survival when compared with placebo, as second-line therapy for patients with metastatic renal carcinoma (MRC). Grade 3/4 adverse events were reported in 12% of patients. This study presents sorafenib's efficacy and safety in a less selected cohort of patients enrolled in an expanded access program.

METHODS

Patients with MRC received sorafenib 400 mg twice daily until disease progression. Tumor response was evaluated by RECIST criteria. Adverse events were graded by NCI common toxicity criteria.

RESULTS

From November 2005 to August 2006, 58 patients were enrolled. The median progression-free survival was 7.5 months (95% CI: 5.4-11.3), and the best responses among 54 patients were 11 (20%) confirmed partial responses, 15 (28%) stable diseases for > or =6 months; 10 patients (18%) had early progression at 8 weeks. Grade 3/4 adverse events occurred in 37 patients (64%; 95% CI: 50%-76%), the most frequent being skin rash in 17 patients (29%), and hand-foot syndrome in 9 patients (15%). Thirty-six (62%) patients required dose reductions and/or treatment interruptions.

CONCLUSIONS

Sorafenib is effective in a less selected patient population with MRC but leads to more toxicity than described previously.