Evaluation of synergy between immune checkpoint blockade therapy with anti-PD-1 and glutaminase inhibition in the treatment of Triple-Negative Breast Cancer

• Grant number: 19/24563-0
• Support type: Scholarships in Brazil - Post-Doctorate
• Effective date (Start): September 01, 2020
• Effective date (End): August 31, 2022
• Field of knowledge: Biological Sciences - Biochemistry - Chemistry of Macromolecules
• Principal Investigator: Sandra Martha Gomes Dias
• Grantee: Amauri da Silva Justo Junior
• Home Institution: Centro Nacional de Pesquisa em Energia e Materiais (CNPEM). Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brasil). Campinas , SP, Brazil

Abstract

Cancer cells have increased glycolytic and glutaminolytic pathways and consume glucose and glutamine at accelerated rates. The intensification of the glycolytic pathway, coined as the Warburg Effect, and the glutaminolytic pathway, provide several intermediates for different synthesis routes and are a hallmark of malignant transformation. Glutamine, in addition to providing biosynthetic intermediates for the 3 major cell building blocks (amino acids, nucleic acids, and lipids), also provides energy, glutathione and NAPDH for the redox balance. Glutamine is also important for maintaining an undifferentiated and metastatic phenotype, with its metabolism being directly linked to tumor aggressiveness. More recently, it has been found that the intense metabolism of glutamine and glucose (in addition to other metabolites) by tumor cells in the tumor microenvironment provides immunosuppression, both by promoting nutrient scarcity and by excreting toxic waste, thus contributing as an important component of the cancer escape to the immune system attack. The glutaminase enzyme (GLS) is often overexpressed in tumors and inhibition of its activity is being tested in clinical studies, among others, for the triple-negative breast cancer subtype (TN; absent estrogen receptor, progesterone, and no Her2 amplification). TN is of high aggressiveness and poor prognosis given that the best target therapies currently employed for breast cancer are not effective in this subtype. The use of immune-checkpoint blockade therapy (ICB) aimed at reactivating the immune system and promoting its attack on tumor cells. The ICB therapy has been shown to be successful but is limited to a fraction of patients. In this sense, we seek treatment combinations that can synergize with immunotherapies. Preliminary data from our group show that breast tumors from patients with high GLS expression have enrichment of a characteristic immune system cell infiltrate profile that includes high CD8+ CTL lymphocytes, strong IFN-³ activity signature and high diversity of T cell receptors (TCR). In addition, these tumors, compared to those with low GLS expression, have a higher expression of PD-1 and PD-L1, which together create a co-repressor T-cell activation complex. Based on the expected impact of GLS inhibition with CB-839 on the phenotypic remodeling of immune cells for tumoricidal subtypes, we hypothesized that tumors with high GLS expression would be good candidates for ICB therapies, with a potential synergy of anti-PD1 treatment and glutaminase inhibition. To evaluate our hypothesis, we will use syngeneic mouse tumor implant models, where we will verify the impact of GLS inhibition with CB-839, as well as overexpression of GLS (or its knock down) with anti-PD1 treatment on tumor growth and metastasis. Remodeling of immune infiltrates and metabolites in tumors will also be evaluated according to the treatments. The results, besides contributing to the basic knowledge in the areas of metabolism and tumor immune control, have the potential to impact the proposition of new treatments for triple-negative breast cancer.