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

The SWI/SNF Protein PBRM1 Restrains VHL-Loss-Driven Clear Cell Renal Cell Carcinoma

PBRM1 is the second most commonly mutated gene after VHL in clear cell renal cell carcinoma (ccRCC). However, the biological consequences of PBRM1 mutations for kidney tumorigenesis are unknown. Here, we find that kidney-specific deletion of Vhl and Pbrm1, but not either gene alone, results in bilateral, multifocal, transplantable clear cell kidney cancers. PBRM1 loss amplified the transcriptional outputs of HIF1 and STAT3 incurred by Vhl deficiency. Analysis of mouse and human ccRCC revealed convergence on mTOR activation, representing the third driver event after genetic inactivation of VHL and PBRM1. Our study reports a physiological preclinical ccRCC mouse model that recapitulates somatic mutations in human ccRCC and provides mechanistic and therapeutic insights into PBRM1 mutated subtypes of human ccRCC.

Resistance to Targeted Therapies in Renal Cancer: The Importance of Changing the Mechanism of Action

Renal cell carcinoma (RCC) is a complex disease characterized by mutations in several genes. Loss of function of the von Hippel-Lindau (VHL) tumour suppressor gene is a very common finding in RCC and leads to up-regulation of hypoxia-inducible factor (HIF)-responsive genes accountable for angiogenesis and cell growth, such as platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). Binding of these proteins to their cognate tyrosine kinase receptors on endothelial cells promotes angiogenesis. Promotion of angiogenesis is in part due to the activation of the phosphatidylinositol-3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathway. Inhibition of this pathway decreases protein translation and inhibits both angiogenesis and tumour cell proliferation. Although tyrosine kinase inhibitors (TKIs) stand as the main first-line treatment option for advanced RCC, eventually all patients will become resistant to TKIs. Resistance can be overcome by using second-line treatments with different mechanisms of action, such as inhibitors of mTOR, c-MET, programmed death 1 (PD-1) receptor, or the combination of an mTOR inhibitor (mTORi) with a TKI. In this article, we briefly review current evidence regarding mechanisms of resistance in RCC and treatment strategies to overcome resistance with a special focus on the PI3K/AKT/mTOR pathway.

Overcome tumor heterogeneity-imposed therapeutic barriers through convergent genomic biomarker discovery: A braided cancer river model of kidney cancer

Tumor heterogeneity, encompassing genetic, epigenetic, and microenvironmental variables, is extremely complex and presents challenges to cancer diagnosis and therapy. Genomic efforts on genetic intratumor heterogeneity (G-ITH) confirm branched evolution, support the trunk-branch cancer model, and present a seemingly insurmountable obstacle to conquering cancers. G-ITH is conspicuous in clear cell renal cell carcinoma (ccRCC), where its presence complicates identification and validation of biomarkers and thwarts efforts in advancing precision cancer therapeutics. However, long-term clinical benefits on targeted therapy are not uncommon in metastatic ccRCC patients, implicating that there are underlying constraints during ccRCC evolution, which in turn force a nonrandom sequence of parallel gene/pathway/function/phenotype convergence within individual tumors. Accordingly, we proposed a "braided cancer river model" depicting ccRCC evolution, which deduces cancer development based on multiregion tumor genomics of exceptional mTOR inhibitor (mTORi) responders. Furthermore, we employ an outlier case to explore the river model and highlight the importance of "Five NGS Matters: Number, Frequency, Position, Site and Time" in assessing cancer genomics for precision medicine. This mutable cancer river model may capture clinically significant phenotype-convergent events, predict vulnerability/resistance mechanisms, and guide effective therapeutic strategies. Our model originates from studying exceptional responders in ccRCC, which warrants further refinement and future validation concerning its applicability to other cancer types. The goal of this review is employing kidney cancer as an example to illustrate critical issues concerning tumor heterogeneity.

A river model to map convergent cancer evolution and guide therapy in RCC

Intratumoural heterogeneity in clear cell renal cell carcinoma (ccRCC) complicates identification and validation of biomarkers and thwarts attempts to improve precision medicine. Efforts to depict intratumoural heterogeneity and to pinpoint strategies for disease control resulted in the creation of the trunk-branch model of mutational cancer evolution, which emphasizes targeting trunk mutations. However, most patients with ccRCC receiving current therapeutics that target these mutations, such as inhibitors of vascular endothelial growth factors, eventually develop resistance. A novel paradigm might improve depiction of cancer evolution and advise therapeutic selection: the river model is based on findings from multiregion sequencing in samples from exceptional responders to mTOR inhibitors. The accumulating data on genotypic and phenotypic convergence in renal cell carcinoma and other malignancies can be used to examine how a mutable river model might best describe clinically significant phenotype-convergent events that could guide effective cancer control. This model originates from studying exceptional responders and its generalizability awaits validation.

New strategies in renal cell carcinoma: targeting the genetic and metabolic basis of disease

The development of new forms of treatment of advanced renal cell carcinoma over the past two decades has been primarily focused on targeting the VHL/HIF pathway. The recent identification of mutations of chromatin-remodeling genes in clear-cell renal carcinoma (ccRCC), of genomic heterogeneity, and of a Warburg-like metabolic phenotype in advanced disease has had a profound effect on our understanding of the evolution of ccRCC and on potential approaches to personalized therapy. Early approaches to therapy for patients with advanced type I papillary RCC that have centered around the MET/HGF pathway will expand as more genomic information becomes available. Sporadic and familial type II papillary renal cell carcinoma are characterized by enhanced aerobic glycolysis and share an antioxidant response phenotype. In fumarate hydratase-deficient RCC, fumarate-induced succination of KEAP1 activates Nrf2 signaling. CUL3 and Nrf2 mutations as well as an Nrf2 activation phenotype are found in sporadic type II papillary RCC. Therapeutic approaches designed to target the Nrf2 pathway as well as to impair blood flow and glucose delivery in these cancers that are highly dependent on a robust tumor vasculature and on ready availability of glucose for energy production and glycolysis are in development.

Targeted therapies for treatment of renal cell carcinoma: recent advances and future perspectives

PURPOSE

A wide variety of targeted therapies are available for the treatment of renal cancer that has progressed beyond the point at which surgery is a viable option. In addition, there are many more that are in the different stages of clinical trials. Here, we provide a methodical discussion of the efficacy and safety of targeted therapies for the treatment of advanced renal cell carcinoma.

METHODS

We conducted a systematic literature employing the search terms: renal cell carcinoma targets, tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors, and each of the drugs discussed within these papers.

RESULTS

The identified targeted therapies work by disrupting specific signalling pathways involved in tumour progression, such as those responsible for angiogenesis and cell proliferation. Tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors are now established classes of drugs used in the treatment of renal cancer, with a total of six having received regulatory approval to date (sorafenib, sunitinib, pazopanib, axitinib, temsirolimus, and everolimus). Ongoing trials are likely to result in addition to these in the near future, for example, tivozanib, dovitinib, and cediranib. Furthermore, in addition to these small molecule drugs, immunotherapies involving monoclonal antibodies against signalling molecules such as vascular endothelial growth factor (bevacizumab) or programmed death-1 (nivolumab) are receiving increasing attention.

CONCLUSIONS

Targeted therapies have great potential for disrupting tumour progression by inhibiting certain signalling pathways. As our understanding of the biochemical pathways involved in cancer progresses, additional targets are certain to become apparent, expanding treatment options even further.

Sunitinib as a paradigm for tyrosine kinase inhibitor development for renal cell carcinoma

OBJECTIVES

To describe the drug development and regulatory approval process for tyrosine kinase inhibitors in renal cell carcinoma using sunitinib as a model drug.

METHODS AND MATERIALS

Key findings from pivotal clinical trials that contributed to regulatory approval and drug development were reviewed.

RESULTS

The pathway of development for sunitinib starts from preclinical models to a phase I clinical trial followed by 2 phase II clinical trials for Food and Drug Administration accelerated approval and a phase III clinical trial for Food and Drug Administration standard approval. After standard approval, optimal dosing and use in the adjuvant setting were further explored. As an established first-line therapy for renal cell carcinoma, sunitinib is now used as a comparator arm for other drugs.

CONCLUSIONS

The development of sunitinib is a model example of "bench to bedside" work in renal cell carcinoma and may provide a framework for the development of other drugs.

Landmarks in the diagnosis and treatment of renal cell carcinoma

The most common renal cancer is renal cell carcinoma (RCC), which arises from the renal parenchyma. The global incidence of RCC has increased over the past two decades by 2% per year. RCC is the most lethal of the common urological cancers: despite diagnostic advances, 20-30% of patients present with metastatic disease. A clearer understanding of the genetic basis of RCC has led to immune-based and targeted treatments for this chemoresistant cancer. Despite promising results in advanced disease, overall response rates and durable complete responses are rare. Surgery remains the main treatment modality, especially for organ-confined disease, with a selective role in advanced and metastatic disease. Smaller tumours are increasingly managed with biopsy, minimally invasive interventions and surveillance. The future promises multimodal, integrated and personalized care, with further understanding of the disease leading to new treatment options.

VEGFR-1 Expression Relates to Fuhrman Nuclear Grade of Clear Cell Renal Cell Carcinoma

Background:

Increasing evidence suggests that vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) 1 signaling may play an important role in the progression of pathological angiogenesis that occurs in many tumors, including renal cell carcinoma (RCC). Therapeutic targeting directed against VEGF and VEGFR-2 has been proven to be successful for metastatic clear cell RCC (CCRCC). However, the expression of VEGFR-1 and its association with prognostic parameters of CCRCC in the tumorigenesis of renal cancer remains unclear. Therefore, we examined the expression of VEGFR-1 and its prognostic significance in CCRCC.

Methods:

Immunohistochemical staining for VEGFR-1 was performed on 126 formalin-fixed paraffin-embedded CCRCC tissue samples. Six of these cases were available for Western blot analyses. The results were compared with various clinicopathologic parameters of CCRCC and patients’ survival.

Results:

VEGFR-1 expression was detected in 59 cases (46.8%) of CCRCC. Higher VEGFR-1 expression was significantly correlated with a lower Fuhrman nuclear grade and the absence of renal pelvis invasion, although it was not related to patients’ survival. Western blot analyses showed higher VEGFR-1 expression in low grade tumors.

Conclusion:

VEGFR-1 expression may be associated with favorable prognostic factors, particularly a lower Fuhrman nuclear grade in CCRCC.