Periodic Reporting for period 2 - UreaCa (Deciphering the metabolic roles of the urea-cycle pathway in carcinogenesis for improving diagnosis and therapy) Reporting period: 2020-11-01 to 2022-04-30 Summary of the context and overall objectives of the project Almost 100 years ago, Warburg described a metabolic change in energy flux during cancerous transformation. Since then, multiple studies have demonstrated how the anabolic synthesis of macromolecules can be altered to support cancer cell progression. Yet, the potential effect of altered catabolic degradation of macromolecules on tumor carcinogenesis has been much less studied. We hypothesize that to support cancer growth robustly, catabolic pathways must be changed too. Thus, the focus of our studies is to identify changes in catabolism to improve cancer patients' diagnosis and therapy. The urea cycle (UC) is mammals' main catabolic pathway to excrete waste nitrogen. Although the complete UC pathway is liver-specific, most tissues express different combinations of UC enzymes according to cellular needs. Encouragingly, we find that dysregulated expression of the UC pathway (UCD) is a global phenomenon in cancer that increases nitrogen availability for the synthesis of macromolecules by decreasing its urine excretion. This metabolic alteration is associated with poor patient prognosis. Thus, we hypothesize that UCD provides a significant metabolic advantage to multiple aspects of carcinogenesis and leads to specific, identifiable genomic and biochemical signatures, with implications for cancer diagnosis and therapy. To pursue our hypothesis, we incorporate state-of-the-art comparative genomic, proteomic, metabolomic, and molecular approaches to explore this scientific "blind spot" of nitrogen catabolism in carcinogenesis. We investigate how UCD causally affects carcinogenesis by characterizing tumor-specific functions of UC enzymes (Aim I), correlating tumor phenotypes with systemic biomarkers (Aim II), and testing the treatment efficacy of drug combinations targeting UCD in cancers (Aim III). Our proposal, strengthened by my training as a physician-scientist, harbors a considerable potential for translational diagnostic and therapeutic impacts by enabling us to identify specific new diagnostic biomarkers for monitoring cancer initiation and progression and predicting and enhancing therapeutic response. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far During the time that passed since the beginning of this project, we have identified a way to improve cancer response to immunotherapy, published in Nature Cancer 2020. In previous work, we and others demonstrated a specific rewiring in cancer that channels amino acid to nucleotide synthesis rather than disposal, specifically increasing pyrimidine nucleotides. The rise in pyrimidine levels generates nucleotide imbalance that induces a unique mutational signature, which can predict response to immunotherapy. Furthermore, these genomic changes lead to the presentation of more immunogenic neo-antigens, which augment cancer response to immunotherapy.In our recent work, we took this finding a step further and showed that increasing pyrimidine levels converts tumors documented to be unresponsive to immunotherapy into responsive ones in both cancer mouse models and human patients. This result was exciting and led to a patent development and 3 invited reviews in impactful journals (Cancer Discovery, Molecular Cell, and Science Advances). Yet, this approach has a caveat as it involves decreasing purine levels using Mizoribine, causing immunosuppression, and hence requiring a step-wise approach. We are now looking for ways to metabolically induce high pyrimidine levels without perturbing purine synthesis. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) Notably, while focusing on changes to cancer metabolism during tumorigenesis, we have noticed significant changes occurring in the systemic metabolism of the host. This result was unexpected and potentially holds substantial implications for cancer diagnosis and therapy that we may unravel by the end of the project. In addition, while immunotherapy is the cutting-edge therapy against cancer, more than 80% of cancer patients do not benefit from it. Identifying regulators that can metabolically induce response would enable multiple cancer patients who currently are unresponsive or unqualified to receive this therapy, to benefit from it. The inherent balance between anabolism and catabolism is perturbed in cancer to promote cell growth
