Halting Breast Cancer Metastasis by Blocking Cancer-MSC Engulfment

Breast cancer metastasis, causing over 40,000 annual deaths in the United States, poses a significant challenge
despite advancements in detection and treatment. The tumor microenvironment plays a pivotal role in cancer
metastasis, with mesenchymal stem cells (MSCs) engaging in complex interactions with cancer cells. These
interactions involve the release of growth factors and cytokines, promoting cancer cell proliferation, angiogenesis,
and immunosuppression, while also aiding cancer cell invasion through extracellular matrix modifications.
Furthermore, mitochondrial transfer from MSCs to cancer cells has been associated with malignancy. Recent
studies suggest cancer cells can engulf neighboring stromal cells, including MSCs, yet the functional implications
of this process remain poorly understood, with limited reports regarding its role in metastasis. Conventional
methods for studying these interactions have limitations in the precision and throughput, so we used microfluidic
technology to create a high-throughput cell pairing platform, revealing a strong connection between MSC
engulfment and breast cancer metastatic potential. In animal studies, these engulfing cancer cells exhibit
increased tumorigenicity, metastatic potential, and resistance to chemotherapy, highlighting the significance of
cancer cell-MSC engulfment in disease progression. As such, we hypothesize that inhibiting breast cancer
cell engulfment of MSCs can effectively impede metastasis. Given the significance of this phenomenon,
challenges remain. Firstly, there is a lack of known small molecular drugs that selectively block cancer-MSC
engulfment for translational studies, and secondly, it is unclear if engulfment directly contributes to metastasis
or just identifies preexisting aggressive cancer cells. Our multifaceted approach involves two main
complementary aims: Aim 1: Discovering and validating compounds that block cancer-MSC engulfment.
We will optimize the high-throughput microfluidic engulfment assay with robotic liquid handling and autonomous
image processing, conduct a comprehensive screening of 2,726 compounds with established Phase I drug safety
profiles, and validate these compounds using a 3D cancer spheroid model and animal studies. Aim 2:
Unraveling the role of cancer-MSC engulfment in metastasis: from cell identification to genetic insights.
We will determine if the population of cancer cells involved in engulfment represents a sub-group of control cells
or is altered by MSC engulfment through scRNA-Seq, conduct a CRISPR screening to identify the pivotal genes
involved in cancer-MSC engulfment process, and experimentally validate these genes' impact on inhibiting
engulfment in vitro and cancer metastasis in vivo. This initiative aims to discover and validate anti-engulfment
compounds and gene targets, with a focus on repurposing FDA-approved compounds for clinical trials. This
groundbreaking drug discovery approach can be extended to address various malignancies, and our high-
throughput microfluidic cell pairing platform has broad applicability for research on cell-cell interactions.

Grant Number: 5R21CA293424-02
NIH Institute/Center: NIH
Principal Investigator: Yu-Chih Chen