Biological Significance of C-met Over Expression in Papillary Renal Cell Carcinoma

Tumorigenesis Mechanisms Found in Hereditary Renal Cell Carcinoma: A Review

Renal cell carcinoma is a heterogenous cancer composed of an increasing number of unique subtypes each with their own cellular and tumor behavior. The study of hereditary renal cell carcinoma, which composes just 5% of all types of tumor cases, has allowed for the elucidation of subtype-specific tumorigenesis mechanisms that can also be applied to their sporadic counterparts. This review will focus on the major forms of hereditary renal cell carcinoma and the genetic alterations contributing to their tumorigenesis, including von Hippel Lindau syndrome, Hereditary Papillary Renal Cell Carcinoma, Succinate Dehydrogenase-Deficient Renal Cell Carcinoma, Hereditary Leiomyomatosis and Renal Cell Carcinoma, BRCA Associated Protein 1 Tumor Predisposition Syndrome, Tuberous Sclerosis, Birt-Hogg-Dubé Syndrome and Translocation RCC. The mechanisms for tumorigenesis described in this review are beginning to be exploited via the utilization of novel targets to treat renal cell carcinoma in a subtype-specific fashion.

Advanced papillary renal cell carcinoma: Epidemiology, genomic drivers, current therapies, and ongoing trials

Papillary renal cell carcinoma (PRCC) is the most common subtype of non-clear cell renal cell carcinoma. PRCC can be subdivided into types 1 and 2 based on histology, each associated with different genetic mutations. The MET gene is commonly altered in type 1 PRCC while multiple alterations are involved in type 2 PRCC. PRCC is an aggressive cancer with a predominance in male and black patients and poor prognosis. Due to its rarity, there was a lack of convincing prospective data to guide treatment; hence, therapies were previously extrapolated from clear cell renal cell carcinoma with mixed results. More recently, some phase 2 trials focused on PRCC have been promising. Tyrosine kinase inhibitor (TKI) monotherapy is considered the standard of care, and combination strategies with TKIs and immune checkpoint inhibitors are emerging. Genetic profiling and large-scale clinical trials are needed to inform targeted treatment of PRCC.

cMET - a prognostic marker in papillary renal cell carcinoma?

BACKGROUND

The tyrosine-protein kinase c-Met plays a decisive role in numerous cellular processes, as a proto-oncogene that supports aggressive tumor behavior. It is still unknown whether c-Met could be relevant for prognosis of papillary RCC (pRCC).

PATIENTS AND METHODS

Specimen collection were a collaboration of the PANZAR consortium. Patients' medical history and tumor specimens were collected from n=197 and n=110 patients with type 1 and 2 pRCC, respectively. Expression of cMET was determined by immunohistochemistry (IHC).

RESULTS

In total, cMET staining was evaluable in of 97/197 type 1 and 63/110 type 2 of pRCC cases. Five-years overall survival reviled no significant difference in dependence of cMET positivity (cMET^- vs. cMET⁺: pRCC type 1: 84.8 % vs. 80.3 %, respectively (p=0.303, log-rank); type 2: 71.4 % vs. 64.4 % respectively (p= 0.239, log-rank)). Interestingly, the subgroup analyses showed a significant difference for cMET expression in T stage and metastases of the pRCC type 2 (p=0.014, p=0.022, chi-square). The cMET positive type 2 collective developed more metastases compared to the cMET negative cohort (pRCC Typ 2 M+: cMET^-: 2 (4.3%) vs. cMET⁺: 12 (19%)).

CONCLUSION

CMET expression did not qualify as a prognostic marker in pRCC for overall survival.

Roles of MET in human cancer

The MET proto-oncogene was first identified in osteosarcoma cells exposed to carcinogens. Although expressed in many normal cells, MET is overexpressed in many human cancers. MET is involved in the initiation and development of various human cancers and mediates proliferation, migration and invasion. Accordingly, MET has been successfully used as a biomarker for diagnosis and prognosis, survival, post-operative recurrence, risk assessment and pathologic grading, as well as a therapeutic target. In addition, recent work indicates that inhibition of MET expression and function has potential clinical benefit. This review summarizes the role, mechanism, and clinical significance of MET in the formation and development of human cancer.

MET alterations and their impact on the future of non-small cell lung cancer (NSCLC) targeted therapies

Introduction: The MET gene and its pathway normally plays a crucial role in cell homeostasis, motility, and apoptosis. However, when the MET gene is altered, there is an imbalance toward cell proliferation and invasion commonly seen in numerous different types of cancers. The heterogeneous group of MET alterations that includes MET amplification, MET exon 14 skipping mutation, and MET fusions has been difficult to diagnose and treat. Currently, treatments are focused on tyrosine kinase inhibitors but now there is emerging data on novel MET-targeted therapies including monoclonal antibodies and antibody-drug conjugates that have emerged.Areas covered: We introduce new emerging data on MET alterations in non-small cell lung cancer (NSCLC) that has contributed to advances in MET targeted therapeutics. We offer our perspective and examine new information on the mechanisms of the MET alterations in this review.Expert opinion: Given the trends currently involving the targeting of MET altered malignancies, there will most likely be a continued rapid expansion of testing, novel tyrosine kinase inhibitors and potent antibody approaches. Combination treatments will be necessary to optimize management of advanced and early disease.

Anti-tumor efficacy of human anti-c-met CAR-T cells against papillary renal cell carcinoma in an orthotopic model

Chimeric antigen receptor (CAR)‐T cell therapy has shown salient efficacy in cancer immunotherapy, particularly in the treatment of B cell malignancies. However, the efficacy of CAR‐T for solid tumors remains inadequate. In this study, we displayed that c‐met is an appropriate therapeutic target for papillary renal cell carcinoma (PRCC) using clinical samples, developed an anti‐human c‐met CAR‐T cells, and investigated the anti‐tumor efficacy of the CAR‐T cells using an orthotopic mouse model as pre‐clinical research. Administration of the anti‐c‐met CAR‐T cells induced marked infiltration of the CAR‐T cells into the tumor tissue and unambiguous suppression of tumor growth. Furthermore, in combination with axitinib, the anti‐tumor efficacy of the CAR‐T cells was synergistically augmented. Taken together, our current study demonstrated the potential for clinical application of anti‐c‐met CAR‐T cells in the treatment of patients with PRCC.

Are tyrosine kinase inhibitors fit for purpose in the treatment of metastatic papillary renal cell carcinoma?

Renal cell carcinoma encompasses a range of histological subtypes. The treatment of metastatic disease in this context remains challenging. Papillary renal cell carcinoma is the second most common subtype and forms a significant subsection of non-clear cell renal cell carcinoma. Tyrosine kinase inhibitors form a significant part of the treatment of this largely incurable disease; however, outcomes tend to be poor. The aim of this article is to scrutinise whether these treatments are evidence-based in their use for metastatic papillary renal cell carcinoma and if good outcomes are reported. A literature review was made using PubMed of major prospective and retrospective studies. The European Association of Urology and European Society of Medical Oncology have both published guidance suggesting sunitinib should be offered first line in the treatment of metastatic papillary renal cell carcinoma. This, however, is based upon weak evidence produced by the ASPEN trial, although this did not discriminate between non-clear cell subtypes and results in further studies were modest. The National Institute for Care and Health Excellence has recently published new guidelines for the use of cabozantinib, which has shown evidence of improved progression-free survival and overall response rates compared with sunitinib. Unfortunately, many of the relevant studies did not specifically assess these treatments in patients solely with papillary renal cell carcinoma and had modest overall success. There is weak evidence that tyrosine kinase inhibitors give significant benefit in those patients with metastatic papillary renal cell carcinoma.

Level of evidence: 2a

Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinoma: Morphological appraisal with a comprehensive review of differential diagnoses

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is an autosomal dominant syndrome wherein affected individuals are at risk for the development of cutaneous leiomyomas, early-onset multiple uterine leiomyomas, and an aggressive subtype of renal cell cancer. HLRCC is caused by germline mutations in the fumarate hydratase (FH) gene, which inactivates the enzyme and alters the function of the tricarboxylic acid/Krebs cycle. This article reviews the hitherto described morphologic features of HLRCC-associated renal cell carcinoma (RCC) and outlines the differential diagnosis and ancillary use of immunohistochemistry and molecular diagnostics for these tumors. The morphologic spectrum of HLRCC-associated RCC is wide and histologic features, including tumor cells with prominent nucleoli, perinucleolar halos, and multiple architectural patterns within the same tumor, which are suggestive of this diagnosis. FH immunohistochemistry in conjunction with genetic counseling and germline FH testing are the important parameters for detection of this entity. These kidney tumors warrant prompt treatment as even smaller sized lesions can demonstrate aggressive behavior and systemic oncologic treatment in metastatic disease should, if possible, be part of a clinical trial. Screening procedures in HLRCC families should preferably be evaluated in large cohorts.

Targeting the MET-Signaling Pathway in Non-Small-Cell Lung Cancer: Evidence to Date

The c-MET proto-oncogene (MET) plays an important role in lung oncogenesis, affecting cancer-cell survival, growth and invasiveness. The MET receptor in non-small-cell lung cancer (NSCLC) is a potential therapeutic target. The development of high-output next-generation sequencing techniques has enabled better identification of anomalies in the MET pathway, like the MET exon-14 (METex14) mutation. Moreover, analyses of epidermal growth factor-receptor (EGFR) and mechanisms of resistance to tyrosine-kinase inhibitors (TKIs) demonstrated the importance of MET amplification as an escape mechanism in patients with TKI-treated EGFR-mutated NSCLCs. This review summarizes the laboratory findings on MET and its anomalies, trial results on METex14 alterations and MET amplification in non-EGFR mutated NSCLCs, and acquired resistance to TKI in EGFR-mutated NSCLCs. The outcomes of the first trials with anti-MET agents on non-selected NSCLC patients or those selected for MET overexpression were disappointing. Two situations seem the most promising today for the use of anti-MET agents to treat these patients: tumors harboring METex14 and those EGFR-sensitive mutation mutated under TKI-EGFR with a MET-amplification mechanism of resistance or EGFR-resistance mutation.

Assessing Genomic Copy Number Alterations as Best Practice for Renal Cell Neoplasia: An Evidence-Based Review from the Cancer Genomics Consortium Workgroup

Renal cell neoplasia are heterogeneous with diverse histology, genetic alterations, and clinical behavior that are diagnosed mostly on morphologic features. The Renal Cell Neoplasia Workgroup of the Cancer Genomics Consortium systematically evaluated peer-reviewed literature on genomic studies of renal cell carcinoma (RCC), including clear cell RCC, papillary RCC, chromophobe RCC, and the translocation RCC involving TFE3, TFEB and MITF rearrangements, as well as benign oncocytoma, which together comprise about 95% of all renal cell neoplasia. The Workgroup curated recurrent copy number alterations (CNAs), copy-neutral loss-of-heterozygosity (cnLOH), rearrangements, and mutations, found in each subtype and assigned clinical relevance according to established criteria. In clear cell RCC, loss of 3p has a disease-initiating role and most likely also in progression with mutations detected in VHL and other genes mapped to this arm, and loss of 9p and/or 14q has well-substantiated prognostic utility. Gain of chromosomes 7 and 17 are hallmark CNAs of papillary RCC, but patterns of other CNAs as detected by chromosomal microarray analysis (CMA) afford sub-classification into Type 1 and 2 with prognostic value, and for further sub-stratification of Type 2. Inherent chromosome loss in chromophobe RCC as detected by CMA is useful for distinguishing the eosinophilic variant from benign oncocytoma which in contrast exhibits few CNAs or rearranged CCND1, but share mitochondrial DNA mutations. In morphologically atypical RCCs, rearrangement of TFE3 and TFEB should be considered in the differential diagnosis, portending an aggressive RCC subtype. Overall, this evidence-based review provides a validated role for assessment of CNAs in renal cell neoplasia in the clinical setting to assist in renal cell neoplasm diagnosis and sub-classification within subtypes that is integral to the management of patients, from small incidentally found renal masses to larger surgically resected specimens, and simultaneously identify the presence of key alterations portending outcome in malignant RCC subtypes.

[Chromophobe renal cell carcinoma-diagnosis and prognosis]

Chromophobe renal cell carcinoma is one of four malignant kidney tumor subtypes. Due to its morphological variance in clinical pathological routine diagnostics, this subtype can cause certain difficulties. The tumor can be mistaken for more aggressive or benign tumors. In both cases the consequences of misdiagnosis regarding treatment decisions can be serious. Due to the morphological variance of the tumor, it has not yet been possible to develop a generally accepted, prognostically convincing graduation scheme. The aim is to improve the quality of diagnostics and estimation of prognosis for this subtype of tumor in order to optimize patient care.

TR1801-ADC: a highly potent cMet antibody-drug conjugate with high activity in patient-derived xenograft models of solid tumors

cMet is a well‐characterized oncogene that is the target of many drugs including small molecule and biologic pathway inhibitors, and, more recently, antibody–drug conjugates (ADCs). However, the clinical benefit from cMet‐targeted therapy has been limited. We developed a novel cMet‐targeted ‘third‐generation’ ADC, TR1801‐ADC, that was optimized at different levels including specificity, stability, toxin–linker, conjugation site, and in vivo efficacy. Our nonagonistic cMet antibody was site‐specifically conjugated to the pyrrolobenzodiazepine (PBD) toxin–linker tesirine and has picomolar activity in cancer cell lines derived from different solid tumors including lung, colorectal, and gastric cancers. The potency of our cMet ADC is independent of MET gene copy number, and its antitumor activity was high not only in high cMet‐expressing cell lines but also in medium‐to‐low cMet cell lines (40 000–90 000 cMet/cell) in which a cMet ADC with tubulin inhibitor payload was considerably less potent. In vivo xenografts with low–medium cMet expression were also very responsive to TR1801‐ADC at a single dose, while a cMet ADC using a tubulin inhibitor showed a substantially reduced efficacy. Furthermore, TR1801‐ADC had excellent efficacy with significant antitumor activity in 90% of tested patient‐derived xenograft models of gastric, colorectal, and head and neck cancers: 7 of 10 gastric models, 4 of 10 colorectal cancer models, and 3 of 10 head and neck cancer models showed complete tumor regression after a single‐dose administration. Altogether, TR1801‐ADC is a new generation cMet ADC with best‐in‐class preclinical efficacy and good tolerability in rats.

MET exon 14 skipping mutations and gene amplification in a Taiwanese lung cancer population

Somatic mutations of MET gene are emerging as important driver mutations for lung cancers. To identify the common clinicopathological features of MET exon 14 skipping mutations and amplification and clarify whether the two MET gene alterations cause protein overexpression were investigated using 196 lung cancer samples of Taiwan through real time-qPCR/sequencing, fluorescence in situ hybridization, and immunohistochemistry. The two MET gene alterations are both present in low frequency, ~1%, in the studied lung cancer population of Taiwan. MET exon 14 skipping mutations were identified from two early-stage patients, who were both relatively advanced in age, and did not carry other driver mutations. One was an adenocarcinoma and the other was a rare carcinosarcoma. Three gene amplifications cases were identified. Neither of the two MET gene alterations would lead to protein overexpression; hence, direct detection in nucleic acid level would be a preferred and straightforward solution for the identification of skipping mutations. The presence of MET exon 14 mutations in minor histological types of lung cancers urge to extend screening scope of this mutation in lung cancer and treatment response evaluation in clinical trials. These would be important next steps for the success of MET target therapy in clinical practice.

Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome (HLRCC): A Contemporary Review and Practical Discussion of the Differential Diagnosis for HLRCC-Associated Renal Cell Carcinoma

CONTEXT.—

Hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC) is an uncommon disorder with germline-inactivating mutations in the fumarate hydratase ( FH) gene. The kidney cancers that develop in patients with HLRCC are often unilateral and solitary, with a potentially aggressive clinical course; morphologic identification of suspicious cases is of the utmost importance.

OBJECTIVE.—

To review classic morphologic features of HLRCC-associated renal cell carcinoma, the reported morphologic spectrum of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in diagnosis of these tumors.

DATA SOURCES.—

University of Michigan cases and review of pertinent literature about HLRCC and the morphologic spectrum of HLRCC-associated renal cell carcinoma.

CONCLUSIONS.—

Histologic features, such as prominent nucleoli with perinucleolar halos and multiple architectural patterns within one tumor, are suggestive of HLRCC-associated renal cell carcinoma. However, the morphologic spectrum is broad. Appropriate use of FH immunohistochemistry and referral to genetic counseling is important for detection of this syndrome.

C-Met as a Key Factor Responsible for Sustaining Undifferentiated Phenotype and Therapy Resistance in Renal Carcinomas

C-Met tyrosine kinase receptor plays an important role under normal and pathological conditions. In tumor cells’ overexpression or incorrect activation of c-Met, this leads to stimulation of proliferation, survival and increase of motile activity. This receptor is also described as a marker of cancer initiating cells. The latest research shows that the c-Met receptor has an influence on the development of resistance to targeted cancer treatment. High c-Met expression and activation in renal cell carcinomas is associated with the progression of the disease and poor survival of patients. C-Met receptor has become a therapeutic target in kidney cancer. However, the therapies used so far using c-Met tyrosine kinase inhibitors demonstrate resistance to treatment. On the other hand, the c-Met pathway may act as an alternative target pathway in tumors that are resistant to other therapies. Combination treatment together with c-Met inhibitor reduces tumor growth, vascularization and pro-metastatic behavior and results in suppressed mesenchymal phenotype and vascular endothelial growth factor (VEGF) secretion. Recently, it has been shown that the acquirement of mesenchymal phenotype or lack of cell differentiation might be related to the presence of the c-Met receptor and is consequently responsible for therapy resistance. This review presents the results from recent studies identifying c-Met as an important factor in renal carcinomas being responsible for tumor growth, progression and metastasis, indicating the role of c-Met in resistance to antitumor therapy and demonstrating the pivotal role of c-Met in supporting mesenchymal cell phenotype.

Clinicopathological impacts of high c-Met expression in renal cell carcinoma: a meta-analysis and review

c-Met overexpression has been observed in renal cell carcinoma (RCC). However, its clinicopathological impacts remain uncertain. We performed this meta-analysis to evaluate the pathologic and prognostic impacts of high c-Met expression in patients with RCC. A systematic computerized search of the electronic databases PubMed and Embase was performed. From 12 studies, 1,724 patients with RCC were included in the meta-analysis. Compared with RCCs showing low c-Met expression, tumors with high c-Met expression showed significantly higher nuclear grade (odds ratio = 2.45 [95% CI: 1.43-4.19], P = 0.001) and pT stage (odds ratio = 2.18 [95% CI: 1.27-3.72], P = 0.005). In addition, patients with c-Met-high RCC showed significantly worse overall survival than those with c-Met-low tumor (hazard ratio = 1.32 [95% CI: 1.12-1.56], P = 0.0009). In conclusion, this meta-analysis demonstrates that high c-Met expression correlate with significantly worse pathological features and overall survival, indicating c-Met overexpression is a potential adverse prognostic marker for patients with RCC.

The role of c-Met in prognosis and clinicopathology of renal cell carcinoma: Results from a single-centre study and systematic review

BACKGROUND AND OBJECTIVES

The c-Met proto-oncogene pathway plays an important role in the progression of various cancers. However, the effect of the c-Met pathway on renal cell carcinoma (RCC) remains controversial. We decided to clarify the role of c-Met in prognosis and clinicopathology of RCC.

METHODS

A total of 10 pairs of tumour and adjacent tissues were obtained from patients with primary RCC between 2013 and 2014 and tissue microarrays to assess c-Met expression in tumour tissues from 90 patients with RCC by Western blot and immunohistochemical staining. We also presented a meta-analysis to explore the correlation between c-Met and pathological grade and stage of RCC. The two-tailed Pearson's χ² and Fischer exact tests were used to compare categorical variables. Multivariate analysis was performed using the multivariate Cox proportional hazards model.

RESULTS

C-Met protein levels were increased in 8 of 10 RCC tissue samples compared with their adjacent normal tissue and c-Met expression levels were positively associated with a high nuclear grade (P = 0.008) and pT stage (P = 0.002). Multivariate analysis showed that a high expression of c-Met was an independent predictor of disease-specific survival (P = 0.017). A meta-analysis found that increased c-Met expression in RCC tissues was closely correlated with high tumour grade (P<0.001) and high pT stage (P = 0.001). Most importantly, c-Met expression was significantly correlated with disease-specific survival (P<0.001).

CONCLUSIONS

Because c-Met is strongly associated with pathological grade, stage and disease-specific survival, c-Met levels may have potential to predict patient prognosis and to guide clinical diagnosis and treatment.

Cabozantinib inhibits tumor growth and metastasis of a patient-derived xenograft model of papillary renal cell carcinoma with MET mutation

MET plays an important role in the development and progression of papillary renal cell carcinoma (pRCC). Evaluation of efficacy of MET inhibitors against pRCC has been hampered by limited preclinical models depicting MET abnormalities. We established a new patient-derived xenograft (PDX) model of pRCC carrying an activating mutation of MET and tested the ability of cabozantinib, an inhibitor of receptor tyrosine kinases including MET, to inhibit tumor growth and metastasis. Precision-cut, thin tissue slices from a pRCC specimen obtained by nephrectomy were implanted under the renal capsule of RAG2^-/-γC^-/- mice to establish first generation TSG-RCC-030. Histologic and genetic fidelity and metastatic potential of this model were characterized by immunohistochemistry, direct DNA sequencing and quantitative polymerase chain reaction (qPCR). The effect of cabozantinib on tumor growth and metastasis was evaluated. Whether measurements of circulating tumor DNA (ctDNA) by allele-specific qPCR could be used as a biomarker of tumor growth and response to therapy was determined. Subrenal and subcutaneous tumor grafts showed high take rates and metastasized to the lung. Both primary tumors and metastases expressed typical markers of pRCC and carried the same activating MET mutation as the parental tumor. Cabozantinib treatment caused striking tumor regression and inhibited lung metastasis in TSG-RCC-030. Plasma ctDNA levels correlated with tumor volume in control mice and changed in response to cabozantinib treatment. TSG-RCC-030 provides a realistic preclinical model to better understand the development and progression of pRCC with MET mutation and accelerate the development of new therapies for pRCC.

Relationships between Chromosome 7 Gain, MET Gene Copy Number Increase and MET Protein Overexpression in Chinese Papillary Renal Cell Carcinoma Patients

To investigate the relationships between Chromosome 7 gain, mesenchymal-epithelial transition factor (MET) gene copy number increase and MET protein overexpression in Chinese patients with papillary renal cell carcinoma (PRCC), immunohistochemistry (IHC), immunofluorescence (IF) and fluorescence in situ hybridization (FISH) were performed on 98 formalin-fixed, paraffin-embedded (FFPE) PRCC samples. Correlations between MET gene copy number increase, Chromosome 7 gain and MET protein overexpression were analyzed statistically. A highly significant correlation was observed between the percentage of tumor cells with MET gene copy number ≥3 and CEP7 copy number ≥3 (R² = 0.90, p<0.001) across two subtypes of PRCC. In addition, the percentage of tumor cells with MET gene copy number ≥3 was found to increase along with increases in MET IHC score. This correlation was further confirmed in those PRCC tumor cells with average MET gene copy number >5 using combined IF and FISH methodology. Overall, this study provides evidence that Chromosome 7 gain drives MET gene copy number increase in PRCC tumors, and appears to subsequently lead to an increase in MET protein overexpression in these tumor cells. This supports MET activation as a potential therapeutic target in sporadic PRCC.

Genetic and Chromosomal Aberrations and Their Clinical Significance in Renal Neoplasms

The most common form of malignant renal neoplasms is renal cell carcinoma (RCC), which is classified into several different subtypes based on the histomorphological features. However, overlaps in these characteristics may present difficulties in the accurate diagnosis of these subtypes, which have different clinical outcomes. Genomic and molecular studies have revealed unique genetic aberrations in each subtype. Knowledge of these genetic changes in hereditary and sporadic renal neoplasms has given an insight into the various proteins and signalling pathways involved in tumour formation and progression. In this review, the genetic aberrations characteristic to each renal neoplasm subtype are evaluated along with the associated protein products and affected pathways. The potential applications of these genetic aberrations and proteins as diagnostic tools, prognostic markers, or therapeutic targets are also assessed.

Papillary renal cell carcinoma: A review of the current therapeutic landscape

Renal cell carcinoma (RCC) is the most common cancer of the kidney and accounts for 2-3% of all adult malignancies. Clear cell carcinoma represents the most common histologic subtype, while papillary Renal Cell Carcinoma (pRCC) accounts for 10-20% of all renal cell cancers. While the inactivation of VHL gene can be found in the majority of clear cell carcinomas, different molecular mechanisms are involved into pRCC biology. Mutations in the MET oncogene are an essential step into the pathogenesis of hereditary pRCC forms, but they can be found only in a small rate of sporadic cases. Several agents, including anti-VEGF drugs and mTOR inhibitors, are possible options in the treatment of advanced and metastatic pRCC, following the demonstration of efficacy obtained in clinical trials including all RCC histologic subtypes. However, data specifically obtained in the subgroup of patients affected by pRCC are limited and not conclusive. Several ongoing trials are evaluating the efficacy of targeted therapy in papillary form. However, more rationale approaches based on molecular studies would help improving the outcome of these patients. Among others, MET inhibitors and targeted immunotherapy are promising new strategies for hereditary and sporadic disease. This review summarizes current knowledge on pRCC tumorigenesis and discusses recent and ongoing clinical trials with new therapeutic agents.

Systemic therapy for non-clear cell renal cell carcinomas: a systematic review and meta-analysis

CONTEXT

Clinical data supporting the use of targeted agents for the treatment of metastatic renal cell carcinoma (RCC) are based predominantly on patients with clear cell histology. Little is known about the efficacy of these drugs in non-clear cell variants.

OBJECTIVE

To evaluate the efficacy of different clear cell RCC (ccRCC)-approved targeted agents among patients with non-ccRCC compared with ccRCC.

EVIDENCE ACQUISITION

We conducted a systematic review of electronic databases to identify publications evaluating the outcomes of patients with non-ccRCC treated with targeted agents approved for treatment of ccRCC. Patients with sarcomatoid variant RCC were excluded from the main analysis but were evaluated as an independent cohort. End points of interest were response rate, median progression-free survival (PFS), and median overall survival (OS). Where possible, data were pooled in a meta-analysis. For studies of unselected patients with RCC, the outcomes of patients with non-ccRCC histology were compared with ccRCC. In exploratory analyses, outcomes of non-ccRCC with nonapproved agents were assessed.

EVIDENCE SYNTHESIS

A total of 49 studies comprising 7771 patients were included in the analysis. Of these, 1244 patients (16.0%) had non-ccRCC, 6300 (83.1%) had ccRCC, and 227 (2.9%) had sarcomatoid tumours. The overall response rate for non-ccRCC with targeted agents was 10.5%. In studies directly comparing non-ccRCC and ccRCC, there were significantly lower response rates for non-ccRCC (odds ratio for response: 0.52; 95% confidence interval, 0.40-0.68; p<0.001). For non-ccRCC treated with targeted agents, median PFS and OS were 7.4 and 13.4 mo, respectively; for patients with ccRCC, these were 10.5 mo and 15.7 mo, respectively (p value for difference<0.001 for both parameters).

CONCLUSIONS

Patients with non-clear cell renal cell carcinoma (non-ccRCC) have significantly lower response rates and poorer median progression-free survival and overall survival than those with ccRCC. The optimal treatment of patients with non-ccRCC remains unclear and warrants further study.

PATIENT SUMMARY

Systemic treatments for patients with renal cell carcinoma (RCC) tend to be significantly less effective for non-clear cell RCC, with lower response rates and worse progression-free survival and overall survival when compared with clear cell RCC. Optimal therapy remains unclear and warrants further study.

Novel approaches targeting the vascular endothelial growth factor axis in renal cell carcinoma

In recent years, functional characterization of the von Hippel-Lindau tumor suppressor, hypoxia-induced factors, and one of their key downstream effectors, the vascular endothelial growth factor (VEGF), has revolutionized treatment of advanced renal cell carcinoma. Therapeutic strategies targeting the ligand itself (VEGF-A) or its receptor (VEGFR2) have proven successful. However, complete remissions are rare, and with time patients invariably suffer disease progression. It is understood that this is due to incomplete suppression of VEGF signaling and/or adaptive up-regulation of non-VEGF-dependent tumor-promoting stimuli. In this article, we review novel VEGF-directed agents that are being developed to address the shortcomings of current targeted drugs for the treatment of advanced renal cell carcinoma. Building on our current understanding of molecular mechanisms behind resistance, examples include next-generation multitarget tyrosine kinase inhibitors, biologics, and other compounds.

Foretinib (XL880): c-MET inhibitor with activity in papillary renal cell cancer

Papillary renal cell cancer (RCC) constitutes approximately 10 % of renal cancers and is the commonest form after clear cell RCC, which accounts for approximately 75 % of cases. Until recently, most clinical trials in RCC were open to patients of all histologic types. Very recent clinical trials have been performed predominately in patients with clear cell RCC and relatively few trials have been done for patients with papillary RCC. The clinical characteristics of papillary RCC are less well appreciated because of both its relative rarity in the general oncology population and the lack of related clinical studies. This article reviews papillary RCC as a clinical entity separate from clear cell RCC. The MET signaling pathway, its association with increased invasion and progression of human cancer, and its dysregulation in papillary RCC is discussed. Lastly, foretinib, a multitargeted receptor tyrosine kinase inhibitor of several receptors, including MET and vascular endothelial growth factor receptor 2, is described in preclinical and phase I studies as well as in a phase II study in papillary RCC patients.

Targeted therapies and the treatment of non-clear cell renal cell carcinoma

BACKGROUND

Targeted therapies have shown profound effects on the outcome of patients with advanced renal cell carcinoma (RCC). However, the optimal treatment for RCC of non-clear cell histology (nccRCC)-typically excluded from trials of targeted agents-remains uncertain.

MATERIALS AND METHODS

By carrying out extensive searches of PubMed and ASCO databases, we identified and summarised research into the biological characteristics, clinical behaviour and treatment of different histological subtypes of nccRCC, focusing on targeted therapy.

RESULTS

The available data suggest that treatments currently approved for RCC are active in ncc subtypes, although the overall clinical benefit may be less than for clear cell RCC. Temsirolimus has proven benefit over interferon-alfa (IFN-α) in patients with nccRCC, based on phase III data, while everolimus, sunitinib and sorafenib have all demonstrated some degree of activity in nccRCC in expanded-access trials. No clear picture has emerged of whether individual histological subtypes are particularly responsive to any individual treatment.

CONCLUSIONS

Further molecular studies into the pathogenesis of RCC histological subtypes will help direct the development of novel, appropriate targeted agents. Clinical trials specifically designed to evaluate the role of targeted agents in nccRCC are ongoing, and data from trials with sunitinib and everolimus will be reported soon.

A phase 2 trial of sunitinib in patients with advanced non-clear cell renal cell carcinoma

BACKGROUND

Sunitinib is a standard-of-care treatment in advanced clear cell renal cell carcinoma (ccRCC). Retrospective and expanded access data suggest sunitinib has activity in advanced non-clear cell renal cell carcinoma (nccRCC).

OBJECTIVE

To prospectively determine the clinical efficacy and safety of sunitinib in patients with advanced nccRCC.

DESIGN, SETTING, AND PARTICIPANTS

This is a single-arm phase 2 trial with a two-stage design. Eligibility criteria included pathologically confirmed nccRCC or ccRCC with ≥ 20% sarcomatoid histology, performance status 0-2, measurable disease, a maximum of two prior systemic therapies, and no prior treatment with tyrosine kinase inhibitors directed against the vascular endothelial growth factor receptors.

INTERVENTION

Patients received sunitinib 50mg daily on a 4-wk on, 2-wk off schedule.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Primary end points were objective response rate (ORR) and progression-free survival (PFS). Secondary end points were safety and overall survival (OS).

RESULTS AND LIMITATIONS

Fifty-seven patients were eligible (nccRCC histology: papillary, 27; chromophobe, 5; unclassified, 8; collecting duct or medullary carcinoma, 6; sarcomatoid, 7; and others, 4). Median PFS for 55 evaluable patients was 2.7 mo (95% confidence interval [CI], 1.4-5.4). Two patients with chromophobe and one patient with unclassified histology had a confirmed partial response (5% ORR). Median PFS for patients with papillary histology was 1.6 mo (95% CI, 1.4-5.4). Median PFS for patients with chromophobe histology was 12.7 mo (95% CI, 8.5-NA). Median OS for all patients was 16.8 mo (95% CI, 10.7-26.3). Treatment-emergent adverse events were consistent with sunitinib's mechanism of action. The nonrandomized design and small number of patients are limitations of this study.

CONCLUSIONS

The differential response of chromophobe histology to sunitinib suggests a therapeutically relevant biological heterogeneity exists within nccRCC. The low ORR and short PFS with sunitinib in the other nccRCC subtypes underscore the need to enroll patients with these diverse tumors in clinical trials.

[Incidence and long-term prognosis of papillary renal cancer. Results of a retrospective multicenter study]

OBJECTIVES

Papillary renal cell carcinoma (pRCC) represents the largest subgroup of non-clear-cell kidney cancer. In this retrospective multicenter study, we assessed tumor characteristics and long-term prognosis of patients with pRCC in comparison with conventional clear-cell cancer (ccRCC).

METHODS

We evaluated 2,804 patients who had undergone renal surgery for pRCC or ccRCC between 1990 and 2006. The mean follow-up was 65 months.

RESULTS

Both pRCC and ccRCC groups were comparable concerning age, tumor grade and the incidence of regional lymph node metastasis at diagnosis. The percentage of male patients was higher in pRCC than in ccRCC (76.0% vs. 63.6%), pRCC patients suffered less often from advanced tumors (22.3% vs. 38.1%), visceral metastasis at diagnosis (8.1% vs. 14.5%) and died less frequently due to RCC progression (16.3% vs. 29.6%). Applying multivariable analyses pRCC was found to be an independent predictor of a favorable clinical course for patients with organ-confined RCC. In contrast in advanced disease papillary histology was significantly associated with a poor prognosis and early tumour-related death.

CONCLUSIONS

pRCC seem to be stratified into two different prognostic groups. Localized pRCC has a significantly better prognosis than ccRCC. In contrast, advanced pRCC is characterized by a worse clinical outcome. Whether these two different pRCC cohorts are consistent with the recently defined types 1 and 2 pRCC subtypes or are characterized by other typical genetic alterations, which would lead to a novel pRCC subclassification is currently under investigation within the German Renal Cancer Network.

The expression pattern of Von Hippel-Lindau tumor suppressor protein, MET proto-oncogene, and TFE3 transcription factor oncoprotein in renal cell carcinoma in Upper Egypt

BACKGROUND

Genetic alterations in renal cell carcinoma (RCC) involve tumor suppressor genes such as Von Hippel-Lindau (VHL); proto-oncogenes such as MET and transcription factors such as TFE3 oncoprotein.

AIM

To examine the clinicopathologic features and the expression of some oncogenic molecules in various RCCs in patients from Upper Egypt.

MATERIALS AND METHODS

The authors examined the expression pattern of pVHL; MET; and TFE3 proteins in 59 RCC using immunoperoxidase staining methods. The study group consisted of clear cell RCCs (CRCC); papillary RCCs type 1 (PRCC1); papillary RCCs type 2 (PRCC2); Xp11-2 translocation RCCs (XP11.2RCC); chromophobe RCCs (ChRCC); and sarcomatoid RCCs (SRCC).

RESULTS

Variations were found in the expression of these molecules in the different types of RCCs. The mean age of RCCs among Egyptians was 52.70 ± 1.73 years; with male sex predominance. Mass lesion; pain; and hematuria were the main presenting features. Metastatic disease was more frequent with CRCC variant. pVHL expression was strong in PCRCC2; Xp11.2RCC; and ChRCC; moderate in CRCC; and weak in both PRCC1 and sarcomatoid RCC. MET protein expression was moderate in Xp11.2RCC; PRCC1; PRCC2; and sarcomatoid RCC. TFE3 protein expression was strong in Xp11.2RCC and PRCC2 variants. The expression was moderate in PRCC1; CRCC; ChRCC; and sarcomatoid RCC. Positive correlation was found in the expression of the different proteins (pVHL; MET; and TFE3) and some histological features (tumor grade; inflammation; necrosis and metastasis) and the presence of metastasis and some histological features (inflammation and/or necrosis).

CONCLUSIONS

This study provides the first indication about the clinicopathologic features of RCCs in Upper Egypt. The variable expression of these molecules in the different variants of RCC suggests that several oncogenic pathways are operational in their development.

Chromosomal amplification of leucine-rich repeat kinase-2 (LRRK2) is required for oncogenic MET signaling in papillary renal and thyroid carcinomas

The receptor tyrosine kinase MET is frequently amplified in human tumors, resulting in high cell surface densities and constitutive activation even in the absence of growth factor stimulation by its endogenous ligand, hepatocyte growth factor (HGF). We sought to identify mechanisms of signaling crosstalk that promote MET activation by searching for kinases that are coordinately dysregulated with wild-type MET in human tumors. Our bioinformatic analysis identified leucine-rich repeat kinase-2 (LRRK2), which is amplified and overexpressed in papillary renal and thyroid carcinomas. Down-regulation of LRRK2 in cultured tumor cells compromises MET activation and selectively reduces downstream MET signaling to mTOR and STAT3. Loss of these critical mitogenic pathways induces cell cycle arrest and cell death due to loss of ATP production, indicating that MET and LRRK2 cooperate to promote efficient tumor cell growth and survival in these cancers.

Prognostic factors in a prospective series of papillary renal cell carcinoma

OBJECTIVE

To prospectively assess the clinical outcome of a series of papillary renal cell carcinomas (PRCCs) to identify possible prognostic clinical variables and tumour markers, as previous retrospective series of PRCC do not provide unanimous results on the prognostic utility of clinicopathological variables.

PATIENTS AND METHODS

Forty-six patients with PRCC (median follow-up 40 months) diagnosed in one institution from 1989 to 2002 were prospectively followed until May 2006. The pathology was reviewed, the PRCC subtyped (type 1 and 2) and immunohistochemistry assessed for MIB-1, vascular endothelial growth factor (VEGF), CD31 and c-met oncogenic protein, by a referee pathologist. Prognostic values were estimated by fitting a Cox model.

RESULTS

The 5-year survival rate was 49.5%; type 2 histology was predominant and was almost significant in the univariate analysis. Stage and MIB-1 were significant prognostic factors only in the univariate model, while the Cox model identified only the Fuhrman grade as an independent predictor of survival (hazard ratio 3.054; P = 0.007). MET expression, CD31 and VEGF had no prognostic utility.

CONCLUSION

These patients with PRCC followed prospectively fared worse than in previously reported series. The Fuhrman grade was the sole independent predictor of survival.

c-Met overexpression is a prognostic factor in ovarian cancer and an effective target for inhibition of peritoneal dissemination and invasion

The hepatocyte growth factor receptor c-Met is a receptor tyrosine kinase that plays an important role in tumor growth by activating mitogenic signaling pathways. The goal of this study was to evaluate the role of c-Met in the biology of ovarian cancer and to determine its potential as a therapeutic target. c-Met protein expression was detected by immunohistochemistry in 138 advanced-stage ovarian cancers using a tissue microarray annotated with disease-specific patient follow-up. Fifteen of 138 (11%) tissues had c-Met overexpression. Median survival for patients with high c-Met levels was 17 months versus 32 months (P = 0.001) for patients with low c-Met expression. Infection of SKOV-3ip1 cells with an adenovirus expressing a small interfering RNA (siRNA) against c-Met efficiently inhibited c-Met protein and mRNA expression as well as extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling. It also inhibited adhesion to different extracellular matrix components, human primary mesothelial cells, and full-thickness human peritoneum and, in vivo, to mouse peritoneum. This was paralleled by a significant reduction in alpha(5) and beta(1) integrin protein and mRNA expression as well as a reduction of urokinase and matrix metalloproteinase (MMP)-2/MMP-9 activity. In SKOV-3ip1 ovarian cancer xenografts, i.p. treatment with the c-Met siRNA significantly reduced tumor burden, ascites formation, protease activity, and the number of peritoneal implants but not tumor size or angiogenesis. These results suggest that c-Met overexpression is a prognostic factor in ovarian cancer and that targeting c-Met in vivo inhibits peritoneal dissemination and invasion through an alpha(5)beta(1) integrin-dependent mechanism. Therefore, c-Met should be explored further as a therapeutic target in ovarian cancer.

Role of carbonic anhydrases in the progression of renal cell carcinoma subtypes: proposal of a unified hypothesis

Renal cell carcinoma (RCC) has the highest rate of occurrence within the US when compared with other countries. Recent advances in the basic research and molecular diagnostics of this malignancy have revealed that RCC is not a single disease, but it is a mixture of several types of malignancies with unique molecular mechanisms and pathological attributes. RCC is now divided into clear cell carcinoma (80% of all kidney cancers), papillary type 1 and papillary type 2 neoplasms (10-15% of all RCC patients) and RCC with chromophobic and oncocytic features, called the Birt-Hogg-Dube (BHD) subtype, in roughly 5% of all patients. Apart from these, neoplasms such as the tuberous sclerosis (TSC) syndrome may occur with a mixed pathological features with a renal presentation. In this review, molecular evidence, both direct and indirect, published so far on all these RCC subtypes have been analyzed to find out whether there is any common thread that could run through these disparate malignancies that happen to occur in a single organ, i.e., the kidney. We believe that the role played by the expression and certain non-traditional activities of the cabonic anhydrase (CA) family members, along with the differing levels of hypoxia induced within these tumors may be the most common denominators. Evidence is presented focusing on how the CA family members could participate in the genesis and progression of each and every one of these RCC subtypes and how their function could be influenced by hypoxia, activities of receptor type protein tyrosine kinases and certain other pre-disposing factors. These rationalizations point towards a unified hypothesis that may help explain the occurrence of all these RCC subtypes in a molecular manner. We hope that these analyses would a) stimulate further studies aimed toward a better understanding of the role played by carbonic anhydrases in RCC subtypes and b) would pave way to a better and rationally designed therapies to interfere with their function to benefit patients with RCC and possibly other cancers.

Molecular Biology of Renal Cell Cancer and the Identification of Therapeutic Targets

Renal cell cancer (RCC) is a heterogeneous disease consisting of different histologic types. Major advances have been accomplished during the last 15 years in our understanding of the genetic events that initiate RCC. These advances were greatly facilitated by meticulous clinical description and registration of patients with familial predisposition to RCC. The cloning of the susceptibility genes that underline familial predisposition to RCC has offered entry points into the signaling pathways that are also deregulated in sporadic RCC. Biochemical studies of these signaling pathways and target validation experiments have already culminated in the discovery and clinical application of small molecules with promising activity in RCC. In this article, we highlight the molecular genetic features of RCC that are more directly related to identification and validation of promising targets for molecular therapy.

Second primary malignancies associated with renal cell carcinoma histological subtypes

PURPOSE

Renal cell carcinoma has been linked to numerous secondary malignancies. We evaluated the risk of secondary malignancies by renal cell carcinoma histological subtype in patients with clear cell, papillary and chromophobe renal cell carcinoma.

MATERIALS AND METHODS

We studied 2,722 patients who underwent nephrectomy for sporadic renal cell carcinoma at our institution between 1970 and 2000. All specimens were reviewed by a single urological pathologist for histological subtype. Associations of second primary malignancies by histological subtype were evaluated using the chi-square and Fisher exact tests.

RESULTS

Of the patients studied 2,188 (80.4%) had clear cell, 378 (13.9%) had papillary and 128 (4.7%) had chromophobe renal cell carcinoma. Patients with papillary renal cell carcinoma were significantly more likely to have colon cancer (p = 0.041), prostate cancer (p = 0.003), any second malignancy (p <0.001) and multiple malignancies (p <0.001) compared with patients with clear cell renal cell carcinoma. In addition, patients with chromophobe renal cell carcinoma were significantly more likely to have colon cancer than patients with clear cell renal cell carcinoma (p = 0.020). Although patients with papillary renal cell carcinoma were more likely to have bladder cancer, the incidence did not differ significantly compared with that in patients harboring clear cell and chromophobe renal cell carcinoma (p = 0.193). We did not find a significant difference in the incidence of breast cancer, lung cancer, rectal cancer or lymphoma among histological subtypes.

CONCLUSIONS

Our data indicate that patients with papillary renal cell carcinoma are more likely to harbor secondary malignancies, including colon and prostate cancer, than patients with clear cell renal cell carcinoma. These results may have important implications for patient education and followup evaluation, and they should prompt mechanistic investigations.

Chemotherapy for non-clear-cell renal cell carcinoma

Clear-cell carcinoma is the most common histopathologic subtype of kidney tumors. Consequently, clinical trials for advanced-stage kidney cancer have focused on patients with clear-cell carcinoma and not on the less common subtypes, including papillary, chromophobe, collecting-duct carcinoma, and sarcomatoid-variant tumors. Whereas immunotherapy has constituted the standard treatment for patients with clear-cell renal cell carcinoma (RCC), it does not appear to have activity in the management of patients with other histologic subtypes. Novel therapies, including those targeting the vascular endothelial growth factor pathway, have recently demonstrated significant activity in clear-cell RCC. Historically, chemotherapy has shown limited activity in advanced-stage RCC; however, clinical trials to date have failed to individualize treatment based on histologic subtype. In this article, we will review the literature and present our experience with the use of chemotherapy in patients with non-clear-cell kidney cancer by histologic subtype.

MET expression in sporadic renal cell carcinomas

Although germline mutations of met proto-oncogene on human chromosome 7q31-34 have been known as useful molecular markers of hereditary papillary renal cell carcinoma (RCC), the expression of MET, a product of met proto-oncogene, has not been fully studied in sporadic RCC, along with its clinical significance. We investigated the expression of MET by immunohistochemistry in 182 cases of renal neoplasm encompassing 145 RCC, 25 urothelial carcinomas of renal pelvis, and 12 oncocytomas. MET was diffusely and strongly expressed in 90% of papillary RCC, all collecting duct carcinomas, and 92% of urothelial carcinomas of renal pelvis. On the contrary, clear cell RCC, chromophobe RCC, and oncocytomas were negative or focally positive for MET expression. In clear cell RCC, MET expression was positively correlated with high nuclear grade, presence of infiltrative growth, tumoral necrosis, papillary architecture, sarcomatoid component, tumoral involvement of the renal pelvis or ureter, involvement of the calyx, and lymphatic invasion. In conclusion, diffuse and strong expression of MET in papillary RCC and collecting duct carcinoma might be helpful in discriminating from the other subtypes of RCC with tubular or papillary growth. In case of MET expression observed in clear cell RCC, it might correlate with those clinicopathological parameters implying aggressive behavior.

Molecular classification of renal tumors by gene expression profiling

Renal tumor classification is important because histopathological subtypes are associated with distinct clinical behavior. However, diagnosis is difficult because tumor subtypes have overlapping microscopic characteristics. Therefore, ancillary methods are needed to optimize classification. We used oligonucleotide microarrays to analyze 31 adult renal tumors, including clear cell renal cell carcinoma (RCC), papillary RCC, chromophobe RCC, oncocytoma, and angiomyolipoma. Expression profiles correlated with histopathology; unsupervised algorithms clustered 30 of 31 tumors according to appropriate diagnostic subtypes while supervised analyses identified significant, subtype-specific expression markers. Clear cell RCC overexpressed proximal nephron, angiogenic, and immune response genes, chromophobe RCC oncocytoma overexpressed distal nephron and oxidative phosphorylation genes, papillary RCC overexpressed serine protease inhibitors, and extracellular matrix products, and angiomyolipoma overexpressed muscle developmental, lipid biosynthetic, melanocytic, and distinct angiogenic factors. Quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry of formalin-fixed renal tumors confirmed overexpression of proximal nephron markers (megalin/low-density lipoprotein-related protein 2, alpha-methylacyl CoA racemase) in clear cell and papillary RCC and distal nephron markers (beta-defensin 1, claudin 7) in chromophobe RCC/oncocytoma. In summary, renal tumor subtypes were classified by distinct gene expression profiles, illustrating tumor pathobiology and translating into novel molecular bioassays using fixed tissue.

c-Met as a target for human cancer and characterization of inhibitors for therapeutic intervention

Receptor tyrosine kinase (RTK) targeted agents such as trastuzumab, imatinib, bevacizumab, and gefitinib inhibitors have illustrated the utility of targeting this protein class for treatment of selected cancers. A unique member of the RTK family, c-Met, also represents an intriguing target for cancer therapy that is yet to be explored in a clinical setting. The proto-oncogene, c-Met, encodes the high-affinity receptor for hepatocyte growth factor (HGF) or scatter factor (SF). c-Met and HGF are each required for normal mammalian development and have been shown to be particularly important in cell migration, morphogenic differentiation, and organization of three-dimensional tubular structures (e.g. renal tubular cells, gland formation, etc.) as well as cell growth and angiogenesis. Both c-Met and HGF have been shown to be deregulated in and to correlate with poor prognosis in a number of major human cancers. New data describing the constitutive phosphorylation of c-Met in a number of human tumors is presented here along with a variety of mechanisms by which c-Met can become activated, including mutation and gene amplification. In support of the clinical data implicating c-Met activation in the pathogenesis of human cancers, introduction of c-Met and HGF (or mutant c-Met) into cells conferred the properties of motility, invasiveness, and tumorgenicity to the transformed cells. Conversely, the inhibition of c-Met with a variety of receptor antagonists inhibited the motility, invasiveness, and tumorgenicity of human tumor cell lines. Consistent with this observation, small-molecule inhibitors of c-Met were developed that antagonized c-Met/HGF-dependent phenotypes and tumor growth in mouse models. This review will address the potential for development of c-Met inhibitors for treatment of human cancers with particular emphasis on recent findings with small-molecule inhibitors.

Therapeutic Options for Variant Renal Cancer

Variant or nonclear cell renal cell cancer is a rare disease constituting only approximately 5% to 8% of the metastatic renal cell cancer population. Pathological criteria for the three main variant subtypes, papillary, chromophobe, and collecting duct, have been specified. Nonetheless, there may be subtypes within these variants, many poorly differentiated tumors cannot be reliably classified, and expertise in recognizing specific subtypes is not widespread. Expression analysis and other molecular techniques are beginning to clarify and standardize the pathological classification scheme. Because these classifications are relatively new and the number of patients with any one subtype is limited, little is known about appropriate therapies for patients with metastatic disease. Retrospective series strongly suggest that immunotherapy is not effective in any nonclear cell subtype. Case reports suggest that cytotoxic chemotherapy used for transitional cell cancers may be helpful in patients with collecting duct cancers. A central registry of patients with variant renal cell cancer should be created in which response to various therapies is recorded. Such a registry could provide support for a more formal multi-institutional study investigating a specific drug or regimen.

Practice and progress in kidney cancer: methodology for novel drug development

PURPOSE

The minimal efficacy of standard therapy for metastatic renal cell carcinoma (RCC) has resulted in the evaluation of numerous novel agents. Some agents have shown promise in phase II trials and yet none have improved survival over standard therapy in phase III trials. We examined existing data relevant to standard therapy and clinical trial methodology in RCC to understand patient, disease and trial design factors that have impacted clinical trial outcome and drug evaluation. Furthermore, we describe new paradigms for the evaluation of novel agents to optimize the yield of clinical research in RCC.

MATERIALS AND METHODS

A comprehensive review of published retrospective analyses and phase II/phase III trials in patients with metastatic RCC was undertaken. Publications with patient selection and/or therapeutic implications in our judgment are presented and evaluated.

RESULTS

Patients with good performance status and access to centers with experienced staff may appropriately receive high dose interleukin-2 after consideration of the relative risks and benefits. Alternatively low dose, single agent cytokine regimens are acceptable. Novel agents may be tested in untreated and refractory RCC. Consideration of the prognostic factors of a given phase II cohort is essential when interpreting single arm clinical trial results. RCC histological subtypes continue to be distinguished biologically and treatment relevant to the vascular endothelial growth factor pathway is most appropriately targeted to clear cell RCC. Nephrectomy in metastatic RCC may impact evaluation of the tumor response and survival in metastatic RCC. Thus, consideration of nephrectomy status in phase II trials and stratification in phase III trials is warranted. Clinical trials that include patients with central nervous system metastases should have standardized treatment of these metastases prior to systemic therapy. Objective response rate as an end point should be used with caution, given its unreliable history in metastatic RCC. Novel trial designs using time to disease progression may allow for interpretation of the antitumor effect in the absence of tumor shrinkage.

CONCLUSIONS

Metastatic renal carcinoma is a model disease for the design of clinical trials and testing of novel agents. Novel trial designs and end points should be considered to evaluate new agents in RCC. Phase III trials must be carefully performed with the most promising agents to impact survival in this disease.

Renal cell carcinoma: new prognostic factors?

PURPOSE OF REVIEW

There are limited independent predictors of survival in patients with renal cell carcinoma. Factors related to the tumor, host and treatment may help us to predict prognosis to a certain extent. Prognostic indicators would enable selection of patients who can benefit from adjuvant therapy and thus should be enrolled in clinical trials. This review highlights developments in the identification of current prognosticators for patients with renal cell carcinoma.

RECENT FINDINGS

Tumor stage, grade and patient-performance status are the known prognostic indicators in renal cell carcinoma. Besides these parameters, many molecular and cytogenetic markers were evaluated recently. Unfortunately, none of these parameters appear to be a better predictive prognostic factor than the usual staging and grading. Therefore, efforts to identify new markers for tumor proliferation and progression are still ongoing. It was recently reported that low carbonic anhydrase 9 staining may be an independent poor prognostic factor in patients with renal cell carcinoma. Moreover, there is increasing interest in prognostic indices and predictive algorithms for survival. Staging systems that combine the pathological features with additional prognostic variables have been constructed to predict outcome. The UCLA Integrated Staging System seems to be superior to staging alone in differentiating patients' survival.

SUMMARY

Although the literature reviewed contains numerous promising clinical, histological, molecular and cytogenetic parameters, none of them has yet been shown to have an independent prognostic value

Suppression of HGF receptor gene expression by oxidative stress is mediated through the interplay between Sp1 and Egr-1

Hepatocyte growth factor (HGF) receptor, the product of the c-met protooncogene, is transcriptionally regulated by a wide variety of cytokines as well as extracellular environmental cues. In this report, we demonstrate that c-met expression was significantly suppressed by oxidative stress. Treatment of mouse renal inner medullary collecting duct epithelial cells with 0.5 mM H(2)O(2) inhibited c-met mRNA and protein expression, which was concomitant with induction of Egr-1 transcription factor. Ectopic expression of Egr-1 in renal epithelial cells markedly inhibited endogenous c-met expression in a dose-dependent fashion, suggesting a causative effect of Egr-1 in mediating c-met suppression. The cis-acting element responsible for H(2)O(2)-induced c-met inhibition was localized at nucleotide position -223 to -68 of c-met promoter, in which reside an imperfect Egr-1 and three Sp1-binding sites. Egr-1 markedly suppressed c-met promoter activity but did not directly bind to its cis-acting element in the c-met gene. Induction of Egr-1 by oxidative stress attenuated the binding of Sp1 to its cognate sites, but it did not affect Sp1 abundance in renal epithelial cells. Immunoprecipitation uncovered that Egr-1 physically interacted with Sp1 by forming the Sp1/Egr-1 complex, which presumably resulted in a decreased availability of unbound Sp1 as a transcriptional activator for the c-met gene. Thus it appears that inhibition of c-met expression by oxidative stress is mediated by the interplay between Sp1 and Egr-1 transcription factors. Our findings reveal a novel transcriptional regulatory mechanism by which Egr-1 sequesters Sp1 as a transcriptional activator of c-met via physical interaction.