Identification of the genes for kidney cancer: opportunity for disease-specific targeted therapeutics

Familial renal cancer: molecular genetics and surgical management

Familial renal cancer (FRC) is a heterogeneous disorder comprised of a variety of subtypes. Each subtype is known to have unique histologic features, genetic alterations, and response to therapy. Through the study of families affected by hereditary forms of kidney cancer, insights into the genetic basis of this disease have been identified. This has resulted in the elucidation of a number of kidney cancer gene pathways. Study of these pathways has led to the development of novel targeted molecular treatments for patients affected by systemic disease. As a result, the treatments for families affected by von Hippel-Lindau (VHL), hereditary papillary renal carcinoma (HPRC), hereditary leiomyomatosis renal cell carcinoma (HLRCC), and Birt-Hogg-Dubé (BHD) are rapidly changing. We review the genetics and contemporary surgical management of familial forms of kidney cancer.

Molecular diagnostics in urologic malignancies: a work in progress

CONTEXT

Molecular diagnostic applications are now an integral part of the management algorithms of several solid tumors, such as breast, colon, and lung. In stark contrast, the current clinical management of urologic malignancies is lagging behind. Clinically robust molecular tests that can identify patients who are more likely to respond to a given targeted agent or even those in need of a more aggressive treatment based on well-validated molecular prognosticators are still lacking. Several promising biomarkers for detection, prognosis, and targeted therapeutics are being evaluated.

OBJECTIVE

To discuss candidate biomarkers that may soon make the transition to clinical assay for patients in urologic oncology.

DATA SOURCES

Selected original articles published in the PubMed service of the US National Library of Medicine.

CONCLUSIONS

Recent understanding of the complex molecular alterations involved in the development and progression of urologic malignancies is yielding novel diagnostic and prognostic molecular tools and opening the doors for experimental targeted therapies in these prevalent, frequently lethal solid tumors.

Biology of metastatic renal cell carcinoma

In the past ten years we have made exceptional progresses in the understanding of RCC biology, particularly by recognizing the crucial pathogenetic role of activation of the HIF/VEGF and mTOR pathways. This has resulted in the successful clinical development of anti-angiogenic and mTOR-targeted drugs, which have profoundly impacted on the natural history of the disease and have improved the duration and quality of RCC patient lives. However, further improvements are still greatly needed: 1) even in patients who obtain striking clinical responses early in the course of treatment, disease will ultimately escape control and progress to a treatment-resistant state, leading to therapeutic failure; 2) prolonged disease control usually requires 'continuous' treatment, even across different treatment lines, making the impact of chronic, low-grade, toxicities on quality of life greater and precluding, for most patients, the possibility of experiencing 'drug-free holidays'; 3) although we have successfully identified classes of drugs (or molecular mechanisms of action) that are effective in a substantial proportion of patients, we still fall short of molecular predictive factors that identify individual patients who will (or will not) benefit from a specific intervention and still proceed on a trial-and-error basis, far from a truly 'personalized' therapeutic approach; 4) finally (and perhaps most importantly), even in the best case scenario, currently available treatments inevitably fail to definitively 'cure' metastatic RCC patients. In this review we briefly summarize recent developments in the understanding of the molecular pathogenesis of RCC, the development of resistance/escape mechanisms, the rationale for sequencing agents with different mechanisms of action, and the importance of host-related factors. Unraveling the complex mechanisms by which RCC shapes host microenvironment and immune response and therapeutic treatments, in turn, shape both cancer cell biology and tumor-host interactions may hold the key to future advances in such a complex and challenging disease.

Diagnosis and treatment of cutaneous paraneoplastic disorders

The skin plays a critical role in the detection of internal malignances. Cutaneous signs of these disorders afford clinicians opportunities for early diagnosis and treatment. We aim to succinctly review the recognition, diagnosis, and treatment of selected cutaneous paraneoplastic diseases. Skin disorders that may be associated with paraneoplastic syndromes include: cutaneous metastases, tripe palms, Sweet's syndrome, glucagonoma, Paget's disease and extramammary Paget's disease, acanthosis nigricans, Birt-Hogg-Dube syndrome, basal cell nevus syndrome, Bazex syndrome (acrokeratosis paraneoplastica), carcinoid syndrome, Cowden's disease(multiple hamartoma syndrome), dermatomyositis, erythema gyratum repens, ichthyosis aquisita, von Recklinghausen's disease, pityriasis rotunda, pyoderma gangrenosum, Quincke's edema (angioedema and paraneoplastic uricaria), paraneoplastic pemphigus, Degos' disease, superior vena cava syndrome, Werner's syndrome, diffuse normolipemic plane xanthomas, and yellow nail syndrome. Treatment for these disorders depends on the nature and anatomic distribution of the primary neoplastic process.

Impact of genetics on the diagnosis and treatment of renal cancer

Kidney cancer is a heterogeneous disease comprised of a number of histologic subtypes, each associated with unique genetic mutations, clinical features, and sensitivity to treatment. By examining families affected with the hereditary kidney cancer syndromes von Hippel-Lindau, hereditary papillary renal cell carcinoma, hereditary leiomyomatosis and renal cell carcinoma, and Birt-Hogg-Dubé, researchers have been able to identify the genes responsible for these syndromes. This work has revealed that kidney cancer is fundamentally a metabolic disorder, and as such, novel targeted therapies specific to their molecular biology have been developed and employed in both the hereditary and sporadic forms of renal cell carcinoma.

Germline mutations in cancer susceptibility genes: an overview for nurses

OBJECTIVE

To provide an overview of hereditary cancer susceptibility genes and associated cancer risks.

DATA SOURCES

Peer reviewed published research studies and review articles.

CONCLUSIONS

Identifying deleterious mutations in cancer susceptibility genes allows for clarification of cancer risk in individual family members and risk-level appropriate screening, and risk management recommendations. Evolving knowledge of the role of germline mutations provides an unprecedented opportunity to reduce cancer incidence, morbidity, and morality.

IMPLICATIONS FOR NURSING PRACTICE

To provide individuals/families with accurate cancer risk management information and guidance, oncology nurses must be familiar with scientific discoveries related to cancer susceptibility genes.

A new hypoxia inducible factor-2 inhibitory pyrrolinone alkaloid from roots and stems of Piper sarmentosum

A new trimethoxycinnamoyl-2-pyrrolinone alkaloid, langkamide (1), along with the known compounds piplartine (2) and 3,4,5-trimethoxycinnamic acid (3) were isolated from the roots and stems of the shrub Piper sarmentosum ROXB. The structures were established by spectroscopic analyses and comparison of their spectral data with values reported in the literature. The compounds were tested for their ability to modulate hypoxia inducible factor-2 (HIF-2) transcription activity and all three showed HIF-2 inhibitory activity with EC₅₀ values of 14.0, 4.8, and 60.6 μM, respectively, for compounds 1, 2, and 3.

Birt-Hogg-Dubé renal tumors are genetically distinct from other renal neoplasias and are associated with up-regulation of mitochondrial gene expression

Background

Germline mutations in the folliculin (FLCN) gene are associated with the development of Birt-Hogg-Dubé syndrome (BHDS), a disease characterized by papular skin lesions, a high occurrence of spontaneous pneumothorax, and the development of renal neoplasias. The majority of renal tumors that arise in BHDS-affected individuals are histologically similar to sporadic chromophobe renal cell carcinoma (RCC) and sporadic renal oncocytoma. However, most sporadic tumors lack FLCN mutations and the extent to which the BHDS-derived renal tumors share genetic defects associated with the sporadic tumors has not been well studied.

Methods

BHDS individuals were identified symptomatically and FLCN mutations were confirmed by DNA sequencing. Comparative gene expression profiling analyses were carried out on renal tumors isolated from individuals afflicted with BHDS and a panel of sporadic renal tumors of different subtypes using discriminate and clustering approaches. qRT-PCR was used to confirm selected results of the gene expression analyses. We further analyzed differentially expressed genes using gene set enrichment analysis and pathway analysis approaches. Pathway analysis results were confirmed by generation of independent pathway signatures and application to additional datasets.

Results

Renal tumors isolated from individuals with BHDS showed distinct gene expression and cytogenetic characteristics from sporadic renal oncocytoma and chromophobe RCC. The most prominent molecular feature of BHDS-derived kidney tumors was high expression of mitochondria-and oxidative phosphorylation (OXPHOS)-associated genes. This mitochondria expression phenotype was associated with deregulation of the PGC-1α-TFAM signaling axis. Loss of FLCN expression across various tumor types is also associated with increased nuclear mitochondrial gene expression.

Conclusions

Our results support a genetic distinction between BHDS-associated tumors and other renal neoplasias. In addition, deregulation of the PGC-1α-TFAM signaling axis is most pronounced in renal tumors that harbor FLCN mutations and in tumors from other organs that have relatively low expression of FLCN. These results are consistent with the recently discovered interaction between FLCN and AMPK and support a model in which FLCN is a regulator of mitochondrial function.

Hereditary renal cancer syndromes: an update of a systematic review

CONTEXT

Hereditary renal cancers (HRCs) comprise approximately 3-5% of renal cell carcinomas (RCCs).

OBJECTIVE

Our aim was to provide an overview of the currently known HRC syndromes in adults.

EVIDENCE ACQUISITION

Data on HRC syndromes were analysed using PubMed and Online Mendelian Inheritance in Man with an emphasis on kidney cancer, clinical criteria, management, treatment, and genetic counselling and screening.

EVIDENCE SYNTHESIS

Ten HRC syndromes have been described that are inherited with an autosomal dominant trait. Eight genes have already been identified (VHL, MET, FH, FLCN, TSC1, TSC2, CDC73, and SDHB). These HRC syndromes involve one or more RCC histologic subtypes and are generally bilateral and multiple. Computed tomography and magnetic resonance imaging are the best imaging techniques for surveillance and assessment of renal lesions, but there are no established guidelines for follow-up after imaging. Except for hereditary leiomyomatosis RCC tumours, conservative treatments favour both an oncologically effective therapeutic procedure and a better preservation of renal function.

CONCLUSIONS

HRC involves multiple clinical manifestations, histologic subtypes, genetic alterations, and molecular pathways. Urologists should know about HRC syndromes in the interest of their patients and families.

Rationale for targeted therapies and potential role of pazopanib in advanced renal cell carcinoma

Advanced renal cell carcinoma (RCC) remains a challenging, major health problem. Recent advances in understanding the fundamental biology underlying one form of RCC, ie, clear cell (or conventional) RCC, have opened the door to a series of targeted agents, such as the tyrosine kinase inhibitors (TKIs), which have become the standard of care in managing advanced clear cell RCC. Among the newest of these agents to receive Food and Drug Administration approval in this disease is pazopanib. This review will summarize what is known about the fundamental biology that underlies clear cell RCC, the data surrounding the previously approved targeted agents for this disease, including not only the TKIs but also the mTOR inhibitors and the vascular endothelial growth factor-specific agent, bevacizumab, and the newest TKI, pazopanib. It will also explore the potential role for pazopanib relative to the other available agents and where it may fit into the armamentarium for treatment of advanced/metastatic RCC.

Targeted therapies for non-clear renal cell carcinoma

The treatment of advanced and metastatic kidney cancer has been revolutionized by the development of targeted systemic therapies. Despite the growing number of available agents approved for use against clear cell renal cell carcinoma, patients with non-clear histologies, constituting approximately 1 in 4 cases of kidney cancer, have not received the same attention. The majority of clinical trials testing novel targeted therapies have excluded non-clear subtypes, providing limited therapeutic options for patients with these diagnoses and their oncologists. This review will focus on the use of targeted therapies against the non-clear histologic subtypes of renal cell carcinoma: papillary I and II, chromophobe, and collecting duct. The unique genetic and molecular profiles of each distinct non-clear kidney cancer subtype will be described, as these differences are integral to the development and effectiveness of the novel agents used to treat them. Trials focusing on non-clear kidney cancer, or those that treated clear cell tumors along with significant numbers of non-clear subtypes, will be discussed. The role of cytoreductive nephrectomy and the use of neoadjuvant and adjuvant targeted therapy will be reviewed. Lastly, areas of future research will be highlighted.

Patient responses to genetic information: studies of patients with hereditary cancer syndromes identify issues for use of genetic testing in nephrology practice

Advances in the genetic basis of kidney disease may mean that genetic testing is increasingly important in reducing disease morbidity and mortality among patients. However, there is little research examining patient responses to genetic information for Mendelian and common kidney diseases. Existing research on kidney and other hereditary cancer syndromes can inform three major issues relevant to the nephrology context as follows: (1) how patients understand their risk of disease after genetic counseling and testing, (2) their emotional responses to the information, and (3) their uptake of recommended risk-reducing strategies. Prior research suggests that genetic counseling and testing may improve patient understanding of genetics, but patients still might not fully understand the meaning of their results for disease risk. Genetic counseling and testing does not appear to result in long-term negative emotional effects among patients who carry mutations or those who do not. Finally, although genetic counseling and testing may improve adherence to recommended screening strategies, adherence varies substantially across different risk-reduction options. Previous research also suggests that computer-based interventions might be a useful adjunct to genetic counseling approaches. Examining whether and how these prior findings relate to the context of hereditary kidney disease is an important area for future research.

VHL and HIF signalling in renal cell carcinogenesis

Hypoxia-inducible factor (HIF) plays an important role in renal tumourigenesis. In the majority of clear cell RCC (ccRCC), the most frequent and highly vascularized RCC subtype, HIF is constitutively activated by inactivation of the von Hippel-Lindau gene. Of the HIF subunits, HIF-2alpha appears to be more oncogenic than HIF-1alpha, in that HIF-2alpha activates pro-tumourigenic target genes. In addition, recent studies indicate that HIF-1alpha, more than HIF-2alpha, can undergo proteasomal degradation in VHL - /- RCC cells. A more detailed understanding of the molecular basis of hypoxia and angiogenesis in renal carcinogenesis has set the stage for the development of targeted therapies, inhibiting multiple HIF-related pathways, such as the phosphatidylinositol 3-kinase-AKT-mTOR, RAS/RAF/MAP, and VEGF signalling routes. However, despite the positive results of these targeting agents in progression-free survival, clinical resistance remains an issue. Recent pre-clinical studies have suggested new targeting approaches such as inhibition of HIF-driven key metabolic enzymes and have introduced new HIF targeting agents, such as histone deacetylase inhibitors, with successful anti-neoplastic effects. In this review, we discuss existing and novel findings about RCC carcinogenesis, with subsequent clinical implications.

Theranostic and prognostic biomarkers: genomic applications in urological malignancies

Compared to other solid tumours such as breast, colon, and lung, the current clinical management of urological malignancies is lagging behind in terms of utilisation of clinically robust molecular tests that can identify patients that are more likely to respond to a given targeted agent, or even those in need of a more aggressive treatment approach based on well-validated molecular prognosticators. Several promising biomarkers for detection, prognosis, and targeted therapeutics are now under evaluation. The following review discusses some of the candidate biomarkers that may soon make their transition into clinically applicable assays in urological oncology patients.

Kinase targets in renal-cell carcinomas: reassessing the old and discovering the new

Renal-cell carcinoma is a heterogeneous group of tumours that arise in the adult kidneys. Irrespective of the type of renal tumour, traditional chemotherapeutic and radiation-based therapies have been largely ineffective at treating advanced tumours, with long-term survival being very low. Molecularly-targeted inhibitors of protein kinases are effective in delaying progression of advanced renal tumours. These therapies revolve around inhibition of the vascular endothelial growth factor receptor tyrosine kinase and the mammalian target of rapamycin serine or threonine kinase signalling pathways. The genetic complexity of renal tumours revealed by gene-expression profiling and other molecular-genetic technologies indicate that inhibition of additional kinase-associated pathways could also prevent renal tumour growth. In this review, we discuss the use of molecularly-targeted kinase inhibitors in the treatment of renal-cell carcinoma and identify the next generation of kinase inhibitors that show promise for treatment.

A pilot clinical trial testing mutant von Hippel-Lindau peptide as a novel immune therapy in metastatic renal cell carcinoma

Background

Due to the lack of specific tumor antigens, the majority of tested cancer vaccines for renal cell carcinoma (RCC) are based on tumor cell lysate. The identification of the von Hippel-Lindau (VHL) gene mutations in RCC patients provided the potential for developing a novel targeted vaccine for RCC. In this pilot study, we tested the feasibility of vaccinating advanced RCC patients with the corresponding mutant VHL peptides.

Methods

Six patients with advanced RCC and mutated VHL genes were vaccinated with the relevant VHL peptides. Patients were injected with the peptide mixed with Montanide subcutaneously (SQ) every 4 weeks until disease progression or until the utilization of all available peptide stock.

Results

Four out of five evaluable patients (80%) generated specific immune responses against the corresponding mutant VHL peptides. The vaccine was well tolerated. No grade III or IV toxicities occurred. The median overall survival (OS) and median progression-free survival (PFS) were 30.5 and 6.5 months, respectively.

Conclusions

The vaccine demonstrated safety and proved efficacy in generating specific immune response to the mutant VHL peptide. Despite the fact that the preparation of these custom-made vaccines is time consuming, the utilization of VHL as a vaccine target presents a promising approach because of the lack of other specific targets for RCC. Accordingly, developing mutant VHL peptides as vaccines for RCC warrants further investigation in larger trials. Trial registration: 98C0139

Molecular diagnosis and therapy of kidney cancer

Kidney cancer is not a single disease; it is made up of a number of cancers that occur in the kidney, each having a different histology, following a different clinical course, responding differently to therapy, and caused by a different gene. Study of the genes underlying kidney cancer has revealed that it is fundamentally a metabolic disorder. Understanding the genetic basis of cancer of the kidney has significant implications for diagnosis and management of this disease. VHL is the gene for clear cell kidney cancer. The VHL protein forms a complex that targets the hypoxia-inducible factors for ubiquitin-mediated degradation. Knowledge of this pathway provided the foundation for the development of novel therapeutic approaches now approved for treatment of this disease. MET is the gene for the hereditary form of type 1 papillary renal carcinoma and is mutated in a subset of sporadic type 1 papillary kidney cancers. Clinical trials are currently ongoing with agents targeting the tyrosine kinase domain of MET in sporadic and hereditary forms of papillary kidney cancer. BHD is the gene for the hereditary type of chromophobe kidney cancer. It is thought to be involved in energy and/or nutrient sensing through the AMPK and mTOR signaling pathways. Hereditary leiomyomatosis renal cell carcinoma, a hereditary form of type 2 papillary renal carcinoma, is caused by inactivation of a Krebs cycle enzyme due to mutation. Knowledge of these kidney cancer gene pathways has enabled new approaches in the management of this disease and has provided the foundation for the development of targeted therapeutics.

New treatment approaches in renal cell carcinoma

Metastatic renal cell carcinoma (RCC) is notoriously chemoresistant; up until recently, immunotherapy (in particular interferon-alpha) has represented the treatment of choice. The understanding of the biology of RCC has resulted in the development of targeted therapies. In particular, multikinase inhibitors (sunitinib, sorafenib, axitinib, pazopanib), antivascular endothelial growth factor agents (bevacizumab), and mammalian target of rapamycin inhibitors (temsirolimus, everolimus) now have a role in the approach to different subsets of RCC. Sunitinib is indicated for the first-line therapy of metastatic RCC as a consequence of a positive phase III trial versus interferon-alpha; sorafenib is now registered for the second-line treatment of RCC, which was earlier treated with cytokine as a consequence of a positive phase III trial versus placebo. Bevacizumab is also indicated in the first-line treatment of metastatic RCC given in combination with interferon-alpha as a consequence of two positive phase III trials. Temsirolimus, unlike the other agents, has also shown activity in poor-prognosis patients, and is now the treatment of choice in previously untreated poor-prognosis RCC as a single agent. Everolimus can be considered as the best therapeutic option in patients with RCC pretreated with targeted agents as a consequence of a positive phase III study versus best supportive care. Markers for appropriate treatment selection, combined use of targeted agents, treatment of special histologies, and adjuvant and neoadjuvant setting represent important special issues to be dealt with in future studies.

Potential use of circulating endothelial cells as a biomarker of renal cell carcinoma

Each year, renal cell carcinoma (RCC) accounts for significant mortality in the population. Whilst the disease is now being diagnosed earlier, determining patient prognosis remains a challenge. Current prognostic indicators, such as TNM stage, Fuhrman grade, and RCC subtype, are inadequate. Unlike several other malignancies, RCC lacks a biomarker that can stratify patients into high, intermediate, or low risk for developing metastases. Additionally, antiangiogenic therapy is currently offered to patients with metastatic disease, however, a biomarker to monitor treatment efficacy is lacking. Recent attention has focused on surrogate markers of tumor vascularization as a source of prognostic biomarkers, as tumor growth is ultimately dependent on neovascularization. Two cell populations of interest, circulating endothelial cells (CECs) and circulating endothelial progenitors (CEPs), have been demonstrated across several studies to contribute to tumor vascularization. Given these findings, studies have examined their utility as biomarkers of prognosis by correlating their levels with progression-free survival and prognostic determinants such as tumor volume and weight. However, their role in predicting prognosis in RCC, as well as their potential to act as markers of treatment efficacy in metastatic RCC, remains to be established. Previous studies on CECs and CEPs in the context of cancer will be outlined in this review.

Targeting the Met signaling pathway in renal cancer

Renal cell carcinoma (RCC), the most common form of kidney cancer, accounts for 3% of all adult malignancies and its incidence has significantly increased over the last 20 years. RCC claims 13,000 lives annually in the USA and more than 100,000 worldwide. A better understanding of the molecular basis of RCC has facilitated the development of novel and more selective therapeutic approaches. An important role in RCC oncogenesis is played by the receptor for HGF, Met, which has attracted considerable attention, more recently as a molecular target for cancer therapy, and several drugs selectively targeting this pathway are now in clinical trials. This review will focus on efforts to understand the role of the Met signaling pathway in renal cancer and how this has contributed to the development of potent and selective drug candidates.

Risk of bilateral renal cell cancer

PURPOSE

The risk of developing bilateral kidney cancer has not been adequately defined in any large, population-based study with long-term follow-up to our knowledge.

PATIENTS AND METHODS

We estimated the risk of metachronous bilateral renal cell cancer in patients diagnosed with unilateral kidney cancer, as recorded in the nationwide cancer registries of Norway and Sweden. Altogether 28,642 patients were followed for an average of 4.4 years. The standardized incidence ratio--the ratio of the observed number of bilateral cancers to the number expected on the basis of the incidence in the Norwegian and Swedish population at large--was used as a measure of relative risk. We used multivariate Poisson regression to separate the effects of the explanatory variables.

RESULTS

A synchronous bilateral renal cell cancer was reported in 86 patients. A total of 112 metachronous bilateral cancers were recorded during 126,493 person-years of follow-up compared with 35.8 expected, yielding an overall relative risk (RR) of 3.1 (95% CI, 2.6 to 3.8) and a cumulative incidence of 0.8% after 20 or more years of follow-up. In the multivariate analyses, risk increased monotonically with younger age at first diagnosis (P for trend < .001); compared with patients who were 60 years or older, those younger than 40 years were at a 17-fold higher risk (RR = 17.4; 95% CI, 10.1 to 29.8). We also found a modest but statistically significant decreasing trend with increasing duration of follow-up.

CONCLUSION

The risk of metachronous bilateral renal cell cancer is drastically higher among patients first affected at a young age, suggesting a subset of early onset renal cell cancer with a strong genetic component.

Tissue biomarkers in renal cell carcinoma: issues and solutions

Renal cell carcinoma (RCC) is an aggressive malignancy that is associated with a high rate of metastasis. Although several promising therapeutic strategies are now available for the treatment of patients with metastatic kidney cancer, the prognosis of these patients remains poor. Research is ongoing to identify RCC-specific biomarkers that can improve early diagnosis, surveillance of tumor progression, and prediction of patient prognosis. The identification of biomarkers that may predict response to specific therapies also will be useful in stratifying patients with RCC for treatment selection. Unfortunately, biomarker detection and measurement in kidney tumor tissues can be biased significantly by the lack of standardization in tissue sample acquisition, storage, and analysis. Consequently, the establishment of standardized operating procedures is necessary to maximize the accuracy of tissue-based biomarker assays. Herein, the authors discuss current issues in tissue-based translational research aimed at identifying clinically useful biomarkers for kidney cancer.

Innovations and challenges in renal cancer: summary statement from the Third Cambridge Conference

The Third Cambridge Conference on Innovations and Challenges in Renal Cancer, a symposium held in Cambridge, Massachusetts, June 27-28, 2008, and chaired by Michael B. Atkins, was convened to discuss the current state of knowledge in the field, critique new data, stimulate communication among those involved in basic and clinical research, and offer recommendations for further study. Four main topics were discussed: genetics and molecular biology of renal cell cancer, staging and prognosis, systemic therapy, and correlative science and biomarkers in stage IV disease. The conference format combined brief presentations with extended periods of discussion. The conclusions and recommendations are summarized in this paper and presented in more detail in the individual papers that follow.

Sequencing of the von Hippel-Lindau gene in canine renal carcinoma

BACKGROUND

Similarities in human and canine renal cell carcinoma (RCC) epidemiology and biologic behavior suggest that molecular mechanisms of tumorigenesis may be similar in both species. Approximately 75% of RCC in people are of the clear cell subtype, up to 85% of which are associated with mutation of the von Hippel-Lindau (VHL) gene. The canine VHL coding deoxyribonucleic acid (DNA) shares 90% identity with the human VHL gene.

OBJECTIVE

To determine whether or not RCC in dogs are associated with VHL mutations, and if so determine the prevalence, type, and location of these mutations.

ANIMALS

Thirteen dogs with RCC, 2 dogs with primary renal sarcomas, and 10 dogs without neoplastic kidney disease.

METHODS

DNA was extracted from paraffin-embedded RCC tissue; DNA extracts from paraffin-embedded and snap-frozen nonneoplastic canine kidneys and canine whole blood were used as negative controls. Polymerase chain reaction and sequencing of the 3 VHL exons was performed, and results compared with the accessioned canine sequence.

RESULTS

All VHL exons were amplified from 9 of 13 canine RCC samples, both renal sarcomas, 8 of 10 nonneoplastic kidney samples, and canine whole blood; only exon 2 could be amplified from 2 RCC samples. Mutations were not identified in any exons. A maximal prevalence of 33.6% for VHL mutations in canine RCC was determined.

CONCLUSION AND CLINICAL IMPORTANCE

Although similarities between canine and human RCC merit further investigation of the dog as a model for some subtypes of renal tumors, the lower prevalence of VHL mutations suggests that oncogenesis in these 2 species differs.

Cytogenetic and molecular tumor profiling for type 1 and type 2 papillary renal cell carcinoma

PURPOSE

The goal of this study was to evaluate immunohistochemical and cytogenetic features and their prognostic value in papillary renal cell carcinoma (PRCC) subtypes.

EXPERIMENTAL DESIGN

One hundred fifty-eight cases of PRCC were identified and reclassified by subtype. Tumoral expression of 29 molecular markers was determined by immunohistochemistry. Cytogenetic analyses were done on a prospective series of 65 patients. Associations with clinicopathologic information and disease-specific survival were assessed.

RESULTS

Fifty-one patients (32%) had type 1 and 107 (68%) type 2 PRCC. Type 2 patients had worse Eastern Cooperative Oncology Group performance status, higher T stages, nodal and distant metastases, higher grades, and a higher frequency of necrosis, collecting system invasion and sarcomatoid features. Type 2 showed greater expression of vascular endothelial growth factor (VEGF)-R2 in the tumor epithelium, and of VEGF-R3 in both tumor epithelium and endothelium. Loss of chromosome 1p, loss of 3p, and gain of 5q were exclusively observed in type 2, whereas type 1 more frequently had trisomy 17. Type 2 PRCC was associated with worse survival than type 1, but type was not retained as an independent prognostic factor. Lower PTEN, lower EpCAM, lower gelsolin, higher CAIX, and higher VEGF-R2 and VEGF-R3 expression, loss of 1p, 3p, or 9p, and absence trisomy 17 were all associated with poorer prognosis.

CONCLUSIONS

Type 2 PRCC is associated with more aggressive clinicopathologic features and worse outcome. Molecular and chromosomal alterations can distinguish between PRCC subtypes and influence their prognosis. The effect of 3p loss on survival in PRCC is opposite to the relationship seen in clear cell RCC.

Epithelioid angiomyolipoma of the kidney

Epithelioid angiomyolipoma (eAMLoma) is an uncommon renal mesenchymal tumor with malignant potential and is frequently associated with tuberous sclerosis (TSC). It is composed of polygonal large-sized tumor cells arranged in an epithelioid manner. Differential diagnosis from renal cell carcinoma (RCC) is often challenging because of its epithelioid morphology. Herein is reported three cases of eAMLoma, involving one in a 28-year-old man with TSC and two in women without TSC (34 and 62 years of age, respectively). The male TSC patient had microscopic conventional AMLomas in the same kidney. All patients were positive for melanoma (reactive with HMB45 antibody, and positive for melan A, tyrosinase and microphthalmia transcription factor) and smooth muscle markers (positive for alpha-smooth muscle-specific actin), but not for epithelial markers (cytokeratin, epithelial membrane antigen). In particular, the translocation RCC is an important differential diagnostic candidate, in terms of the positive reaction with HMB45 and morphological similarity. The present tumor samples did not show any reactivity for transcription factor binding to IGHM enhancer 3 or transcription factor EB, which excluded the possibility of translocation RCC. The possibility of eAMLoma should be evaluated as a diagnostic candidate, especially in cases of renal tumors (i) in young patients; (ii) associated with TSC; or (iii) with an epithelioid morphology and a high nuclear grade.

Systemic therapy for metastatic renal cell carcinoma

Renal cell cancer (RCC) is the most common form of cancer of the kidney and accounts for approximately 44,000 cases per year in the United States. Historically, only immunotherapy showed activity in metastatic RCC. The improved survival and quality of life for patients with metastatic RCC over the last several years are direct results of advances made in understanding the development of RCC. Three targeted therapies-sunitinib, sorafenib, and temsirolimus-have been approved for use in the United States recently. Current research is aimed at developing new drugs and combining available drugs to improve upon the responses and survival seen with approved single agents.

Prognostic models and algorithms in renal cell carcinoma

Although surgical treatment is curative for localized renal cell carcinoma (RCC), 25% of patients present with locally advanced or disseminated disease, and disease will recur systemically in another 20% to 30% of those who have localized disease at presentation. Many clinical, histologic, and molecular factors have been identified that place patients who have localized RCC at greater risk for recurrence and those who have metastatic disease at risk for progression or death. This article reviews the major prognostic factors for RCC and the most commonly used algorithms developed for use before or after nephrectomy and before initiation of systemic therapy. These RCC nomograms allow more accurate counseling of patients regarding their likely clinical course and facilitate treatment planning.

Identification of molecular targets in urologic oncology

OBJECTIVES

Molecular targets in cancer diagnosis and therapy have come to the fore of the oncology field in the last decade. Their identification is rooted in basic science investigation and enhanced knowledge in the fields of genetics, biochemistry, molecular and tumor biology, and pathology among others.

METHODS

A medical literature search in English using MEDLINE/PUBMed was performed on the topics of molecular targets, targeted therapy, and biomarkers in the areas of bladder, prostate, and renal cancers. This information was analyzed and combined with the author's personal knowledge in the identification and development of molecular targets. Data is included from the author's laboratory regarding examples of target development and clinical translation.

RESULTS

Molecular targets are often biomarkers; either prognostic ones that reflect the natural history of the cancer or predictive ones that reflect the impact of a therapy. Molecular targets in urologic cancer may arise from four sources: the host, the tumor, as a result of a treatment, or associated with a specific disease stage. Understanding the continuum of targets through the progression of a urologic cancer is central to the translational applications of diagnostics, individualized medicine and targeted therapeutics. Urologists are most familiar with targeted therapy in renal cancer with the introduction of tyrosine kinase inhibitors. Yet, herein are examples of biomarkers and targets across the spectrum of urologic tumors, stages and treatments.

CONCLUSIONS

Identification of events, signals, and pathways in urologic cancer are opportunities to develop biomarkers and targets for diagnosis and treatment.

Chromosome 1 analysis in chromophobe renal cell carcinomas with tissue microarray (TMA)-facilitated fluorescence in situ hybridization (FISH) demonstrates loss of 1p/1 which is also present in renal oncocytomas

Morphologic overlap between chromophobe renal cell carcinoma (ChRCC) and renal oncocytomas (RO) has been widely recognized. Whether these tumors are genetically related and represent a spectrum of benign to malignant tumor progression remains an open question. We previously showed by conventional cytogenetics and fluorescent in situ hybridization (FISH) that the most common chromosomal abnormality in RO is loss of chromosome 1 or 1p. In this study, we evaluated chromosome 1 in ChRCC using the same set of FISH probes. Twenty-one ChRCCs from 13 men and 8 women were studied. Formalin-fixed, paraffin-embedded tissue blocks were used to construct tissue microarrays. A subtelomeric 1p36.3 probe was used in tandem with 1q25 probes for FISH studies. The patients ranged in age from 34 to 82 years (mean 62.8 y, median 61 y). FISH analysis showed an abnormal chromosome 1 in 20/21 (95%) ChRCCs as follows: 18 tumors (85%) had loss of entire chromosome 1, 2 tumors (10%) had loss of 1p36.3 only, and 1 tumor (5%) was apparently diploid for chromosome 1. In this study, 95% of ChRCCs showed abnormality of chromosome 1 by FISH. The progression of chromosome 1 abnormalities, from diploid to loss of 1p to loss of entire chromosome, is also present in oncocytomas. These results provide further evidence to support a genetic similarity between chromophobe carcinoma and oncocytoma. Whether abnormalities of chromosome 1 are associated with RO tumorigenesis or its progression to carcinoma requires further studies.

VHL loss of function and its impact on oncogenic signaling networks in clear cell renal cell carcinoma

Loss of von Hippel-Lindau tumor suppressor gene function occurs in familial and most sporadic clear cell renal cell carcinoma, resulting in the aberrant expression of genes that control cell proliferation, metabolism, invasion and angiogenesis. The molecular mechanisms by which loss of function leads to tumorigenesis are not yet fully defined. The von Hippel-Lindau gene product is part of an ubiquitin ligase complex that targets hypoxia inducible factors for polyubiquitination and proteasomal degradation, linking hypoxia response genes to renal cell carcinoma oncogenesis. Loss von Hippel-Lindau gene function also promotes cell invasiveness in response to hepatocyte growth factor, an important regulator of kidney development and renal homeostasis. Increased cell invasiveness is mediated by another ubiquitin ligase target with relevance to the molecular pathogenesis of renal cell carcinoma: beta-catenin. This discovery and other recent insights into kidney cancer oncogenesis implicate convergent developmental and homeostatic signaling pathways in tumorigenesis, tumor invasiveness and metastasis.

Identifying fragilities in biochemical networks: robust performance analysis of Fas signaling-induced apoptosis

Proper control of apoptotic signaling is critical to immune response and development in multicellular organisms. Two tools from control engineering are applied to a mathematical model of Fas ligand signaling-induced apoptosis. Structured singular value analysis determines the volume in parameter space within which the system parameters may exist and still maintain efficacious signaling, but is limited to linear behaviors. Sensitivity analysis can be applied to nonlinear systems but is difficult to relate to performance criteria. Thus, structured singular value analysis is used to quantify performance during apoptosis rejection, ensuring that the system remains sensitive but not overly so to apoptotic stimuli. Sensitivity analysis is applied when the system has switched to the death-inducing, apoptotic steady state to determine parameters significant to maintaining the bistability. The analyses reveal that the magnitude of the death signal is fragile to perturbations in degradation parameters (failures in the ubiquitin/proteasome mechanism) while the timing of signal expression can be tuned by manipulating local parameters. Simultaneous parameter uncertainty highlights apoptotic fragility to disturbances in the ubiquitin/proteasome system. Sensitivity analysis reveals that the robust signaling characteristics of the apoptotic network is due to network architecture, and the apoptotic signaling threshold is best manipulated by interactions upstream of the apoptosome.

Showering c-MET-dependent cancers with drugs

The receptor tyrosine kinase, c-MET and its ligand hepatocyte growth factor/scatter factor (HGF/SF) have become leading candidates for targeted cancer therapies. Inappropriate c-MET signaling through autocrine, paracrine, amplification, and mutational activation occurs in virtually all types of solid tumors (http://www.vai.org/met), contributing to one or a combination of proliferative, invasive, survival, or angiogenic cancer phenotypes. c-MET and HGF/SF participate in all stages of malignant progression and represent promising drug targets in a variety of cancer types, including carcinomas, sarcomas, and brain tumors. While many are in pre-clinical testing, a few inhibitors have entered clinical trials. With hundreds of thousands of potential responding cancers that express c-MET, the interest in this molecule as a drug target is not surprising. However, the cognate c-MET diagnostic tests lag behind. In addition, despite the great enthusiasm based on response rates in phase I trials, there is a need for caution. It is almost without question that combination therapies with c-MET-HGF/SF inhibitors will be required for most cancers to achieve a cytotoxic tumor response.