Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma (RCC), accounting for ~75% of cases. First-line treatment for advanced RCC relies on immune checkpoint inhibitor–based combinations, including those with tyrosine kinase inhibitors such as cabozantinib, the one we use in the study. Cabozantinib is a multi-tyrosine kinase inhibitor targeting receptors involved in angiogenesis and tumour growth. Despite its efficacy, resistance usually emerges within 1–1.5 years, and the underlying mechanisms remain unclear. My project aims to improve cabozantinib efficacy by combining it with another molecule. Preliminary RNA-Seq analyses of cabozantinib-induced ccRCC adaptive responses showed upregulation of mTOR target genes in ccRCC cell lines. Based on this data, we combined cabozantinib with the RMC-5552, a third-generation mTOR inhibitor, recently tested in phase I clinical trial.

In vitro analyses were performed in 2D and 3D models across four human ccRCC cell lines (786-O, A-498, Caki-1, and Caki-2) and two murine lines (RENCA and RENCA-KO VHL), to assess synergistic anti-tumour effects using matrices. In vivo, we evaluated efficacy and toxicity in swiss nude mouse xenograft model subcutaneously grafted with 786-O cells. We monitored tumour growth and body weight over time, and performed biochemical and haematological analyses to assess treatment toxicity, in accordance with regulatory approvals. At the mechanistic level, we conducted multi-omics analyses including metabolomics, RNA-Seq, polysome profiling and single cell proteomic to elucidate the molecular mechanisms underlying the efficacy of the combination.

We demonstrated the synergistic effect of this new therapeutic combination, cabozantinib + RMC-5552, for kidney cancer in vitro, and confirmed its efficacy in vivo where we observed an additive effect. For the mechanism of action, we showed that the combination inhibits cell proliferation, cellular translation and decreases the oxidative phosphorylation. We also showed the essential role of the translational repressor 4EBP1 in this synergistic effect.

We identified a novel synergistic treatment combination for ccRCC, in vitro and in vivo, that affects cells proliferation by perturbing cellular metabolic status. This combination appears highly promising and may ultimately contribute to improve therapeutic management of ccRCC patients, with potential extension to other cabozantinib-treated cancers, such as liver cancer (HCC).

I’m funded by the University of Montpellier and the project is funded by Ipsen.