New Therapeutic Interventions for Kidney Carcinoma: Looking to the Future

Abstract

Patients suffering from metastatic renal cell carcinoma (mRCC) show an overall survival rate of lower than 10% after 5 years from diagnosis. Currently, the first-line treatment for mRCC patients is based on antiangiogenic drugs that are able to inhibit tyrosine kinase receptors (TKI) in combination with immuno-oncology (IO) therapy or IO-IO treatments. Second-line therapy involves the use of other TKIs, immunotherapeutic drugs, and mTOR inhibitors. Nevertheless, many patients treated with mTOR and TK inhibitors acquire drug resistance, making the therapy ineffective. Therefore, the research of new therapeutic targets is crucial for improving the overall survival and quality of life of mRCC patients. The investigation of the molecular basis of RCC, especially in clear cell renal cell carcinoma (ccRCC), has led to the identification of different signaling pathways that are involved in renal carcinogenesis. Most of ccRCCs are associated with mutation in VHL gene, which mediates the degradation of hypoxia-inducible factors (HIFs), that, in turn, regulate the pathways related to tumorigenesis, including angiogenesis and invasion. Renal tumorigenesis is also associated with the activation of tyrosine kinases that modulate the PI3K-Akt-mTOR pathway, promoting cell proliferation and survival. In ccRCC, the abnormal activity of mTOR activates the MDM2 protein, which leads to the degradation of tumor suppressor p53 via proteasome machinery. In addition, p53 may be degraded by autophagy in a mechanism involving the enzyme transglutaminase 2 (TG2). Suppression of wild-type p53 promotes cell growth, invasion, and drug resistance. Finally, the activation of ferroptosis appears to inhibit cancer progression in RCC. In conclusion, these pathways might represent new therapeutic targets for mRCC.

Keywords: autophagy; drugs; kidney cancer; p53; signaling.

Figure 1

Schematic model of kidney cancer cell with the mainly pathogenic pathways/processes and relative inhibitors/activators. Dashed lines and boxes indicate the inactivated components in RCC. ART: Artesunate; EMP1: Epithelial membrane protein 1; HCQ: Hydroxychloroquine; HIF: Hypoxia-inducible factor; LC3II: Microtubule-associated protein light chain 3B; MDM2: Mouse double minute 2 homolog; mTOR: Mammalian target of rapamycin; NOX4: NADPH oxidase 4; PI3K: Phosphatidylinositol 3-kinase; ROS: Reactive oxygen species; RTK: Receptor tyrosine kinase; SQSTM1: Sequestosome-1; TAZ: Transcriptional co-activator with PDZ-binding motif; TG2: Transglutaminase 2; TK: Tyrosine kinase domain; Ub: Ubiquitin; VEGF: Vascular endothelial growth factor; VHL: von Hippel–Lindau.