Cytosolic DNA-Sensing Pathways in BRCA1-Deficient Breast Cancer Development
Abstract
This proposal will address the Breast Cancer Research Program overarching challenges, prevent breast cancer (primary prevention) and identify what drives breast cancer growth; determine how to stop it. Women with inherited mutations in the BRCA1 gene are at high risk of developing basal-like breast cancer (BLBC). The current treatment and preventative strategies for BRCA1-mutant BLBC include therapies based on platinum or PARP inhibitors, as well as risk-reduction approaches based on annual screening with mammography and MRI (magnetic resonance imaging), prophylactic mastectomies, or prophylactic oophorectomy. Due to the nature of these approaches, less invasive and/or more effective strategies for breast cancer prevention are urgently needed. Working toward achieving this long-term goal, we have developed a novel mouse model to recapitulate BLBC development in BRCA1 mutation carriers, and characterized key events at different stages of BRCA1 mammary tumor development. We found that loss of BRCA1 function in luminal mammary epithelial cells (MECs) led to accumulation of DNA damage in them, which may lead to release of DNA fragments into their cytoplasm (normally these genomic DNAs should be within the nucleus of a cell). The presence of abnormal DNA fragments in the cytoplasm can trigger a series of immune reactions, which on one hand may restrict the proliferation of MECs with DNA damage, on the other hand can also cause chronic inflammation to promote cancer development. By shifting the balance between these two, one may be able to develop a novel strategy to prevent breast cancer development in BRCA1 mutation carriers. A key question here is what is the program that links DNA damage accumulation in BRCA1-deficient MECs to host immune responses. Our preliminary studies suggested that pathways that sense the presence of abnormal DNA fragments in the cytoplasm of a cell and relay this signal to its nucleus may provide such a link. These so-called cytosolic DNA-sensing pathways, once activated, can lead to production of a series of soluble factors from the affected cells to induce host immune responses. The goal of this proposed project is to investigate the role of cytosolic DNA-sensing pathways, in particular one such pathway referred to as the STING pathway, in development of BRCA1-deficient breast cancer. To achieve this goal, we propose two specific aims. In one set of experiments (Aim 1), we will culture BRCA1-deficient MECs isolated from our mouse model in a three-dimensional format as mini-glands (referred to as organoids) and use these organoids to study: (1) whether DNA damage accumulation in BRCA1-deficient MECs activates the STING pathway, leading to production of inflammation-inducing soluble factors from them; whether production of these factors is mediated via a downstream effector referred to as NFkappaB, and whether we can change levels and types of these MEC-produced factors by modulating the activity of the STING pathway; (2) how BRCA1-deficient MECs interact with immune cells, such as macrophages, antigen-presenting cells (e.g., dendritic cells) and cytotoxic T cells, and whether modulation of the STING pathway activity can alter these interactions and affect the growth of the co-cultured organoid MECs. In another set of experiments (Aim 2), we will use our BRCA1-deficient breast cancer mouse model described above to directly assess the role of cytosolic DNA-sensing pathways, particularly the STING pathway, in BRCA1 mammary tumor development. We will either disrupt the STING gene in both MECs and immune cells or induce its loss specifically in BRCA1-deficient MECs, and determine how these genetic manipulations affect development of BRCA1-deficient mammary tumor. We will also give mice activator or inhibitor of the STING pathway at different time points during development of BRCA1-deficient mammary tumor, and determine if these different pharmacological treatments can block mammary tumor initiation f
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210493
Entities
People
- Zhe Li
Organizations
- United States Army