Spread of cancer cells into the spinal fluid, or leptomeningeal metastasis (LM), is an increasingly common complication of cancer that results in rapid neurologic disability and death. The spinal fluid represents a poor medium for cell growth: it is hypoxic, with sparse metabolic intermediates, minimal protein, and few growth factors. Despite this, select cancer cells survive and grow within this space. The mechanisms that underlie cancer cell growth with the spinal fluid remain poorly understood. The primary objective of the proposed research is to determine the mechanisms by which breast cancer cells grow within the spinal fluid. Preliminary data from patient samples and mouse modeling suggest that cancer cells exploit innate immunity to improve their growth in the spinal fluid. We hypothesize that cancer cell- macrophage interactions alter the cancer cell transcriptome to enable cancer cells to access limiting substrates for growth such as iron. To address this hypothesis, we propose to subject iteratively collected spinal fluid samples to multiple orthogonal analyses, including single cell RNA sequencing, flow cytometry, bulk RNA sequencing and mass spectrometry. Cellular and molecular components correlating with development of LM will generate a genes of interest list. This list will be curated through gain-of- function and loss-of-function studies in syngeneic mouse models of LM. These mouse models together with in vitro growth assays will enable granular dissection of the molecular mechanisms governing cancer cell growth within the spinal fluid. This approach will enable us to: 1. Address cellular transcriptional adaptations to the low- iron environment of the spinal fluid; 2. Determine mechanistic consequences of adaptation to this low iron microenvironment; and 3. Establish cancer cell-macrophage interactions in leptomeningeal metastasis. This translational approach will improve understanding of the essential steps that govern cancer cell growth within the spinal fluid in human disease, identifying key mechanistic steps for rational targeting strategies in the future.
Spread of cancer cells into the spinal fluid, or leptomeningeal metastasis, is a cruel complication of cancer that results in rapid neurologic disability and death. We understand little about the mechanisms that allow cancer cells to grow with the spinal fluid. To remedy this, we propose a bench-to-bedside approach combining state-of- the-art analyses of clinical samples with rigorous, hypothesis-driven mouse modeling.
