Immune evasion and resistance to immunotherapy in TK1-High Adrenocortical Tumors: evaluation in novel in vivo and in vitro models.

• Grant number: 25/14697-0
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: October 06, 2025
• End date: October 05, 2026
• Field of knowledge: Health Sciences - Medicine - Maternal and Child Health
• Principal Investigator: Carlos Alberto Scrideli
• Grantee: Alcides Euzebio Tavares Xavier
• Supervisor: David Breault
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil
• Institution abroad: Boston Children's Hospital, United States
• Associated to the scholarship: 23/11490-0 - Evaluation of the Role of the TK1 Gene in Malignancy and Immune Evasion of Adrenocortical Tumors in vitro and in vivo model, BP.DR

Abstract

Adrenocortical carcinoma (ACC) is a highly aggressive endocrine malignancy with a dismal 5-year survival rate and limited treatment options. Although immune checkpoint blockade (ICB) has shown success in many solid tumors, ACC displays intrinsic resistance to immunotherapy, likely due to poorly understood tumor-intrinsic mechanisms. One major limitation in elucidating these mechanisms has been the lack of preclinical models that recapitulate tumor-immune interactions in ACC. Recently, our collaborators at Boston Children's Hospital, Harvard Medical School, developed the first genetically engineered mouse model of ACC (BPCre), which targets Wnt/beta-catenin and p53 pathways and includes a syngeneic cell line (BCH-ACC3). This model recapitulates molecular and histopathologic features of human ACC, including immune exclusion. Moreover, they found that MART-1, a known target in melanoma, is also expressed in human ACC tumors and the H295R cell line. DMF5 TCR-engineered CD8 T cells partially killed H295R cells, validating MART-1 as a model antigen in ACC and supporting its use to study T cell cytotoxicity.Through integrative analyses, we identified thymidine kinase 1 (TK1), a key enzyme in DNA synthesis, as a candidate driver of immune evasion in ACC. TK1 is overexpressed in BPCre tumors and correlates with poor prognosis in both pediatric and adult ACC. In adults, TK1 is positively correlated with infiltration by Th2 and MDSCs, while in pediatric ACC it is negatively associated with HLA gene expression. TK1 knockdown in H295R cells does not alter proliferation in vitro but reduces cell growth when co-cultured with PBMCs, suggesting a role in immune evasion.Aim: Determine the effects of TK1 inhibition on tumor immune evasion and response to ICB.Using BCH-ACC3 cells, we will:(1) Generate TK1 knockout using the SCAR system;(2) Establish orthotopic tumors via adrenal injection in mice;(3) Compare tumor growth in NSG vs. C57BL/6 mice to dissect immune-dependent effects;(4) Evaluate response to anti-PD-1 in TK1 KO and control tumors;(5) Characterize immune populations by multiplex IHC;(6) Test cytotoxicity of MART-1-specific CD8 T cells against TK1-KD H295R cells, with/without anti-PD-1;(7) Perform RNA-seq in mouse and human ACC cells to reveal pathways downstream of TK1.This project will provide mechanistic insight into TK1-mediated immune evasion in ACC and establish preclinical rationale for targeting TK1 to improve immunotherapy responses. (AU)