MSLN-mediated activation of EGFR-ERK1/2 signaling drives liver metastasis in breast cancer [HCC1806-HM3]

Introduction: Breast cancer (BC) is the most prevalent malignant disease affecting female patients globally, with triple-negative breast cancer (TNBC) being the subtype linked to the poorest clinical outcome. The liver is a frequent metastatic site of breast cancer. Therefore, elucidating the mechanism underlying liver metastasis in TNBC is crucial for identifying effective diagnostic and therapeutic targets, which holds significant potential for guiding clinical treatment. Objectives: To identify the key gene driving liver metastasis in breast cancer, investigate its mechanism of action, and advance breast cancer treatment. Methods: RNA sequencing was conducted on 4T1-HM3 and its corresponding primary tumor cell 4T1-Pri to identify and screen genes involved in liver metastasis. The enhanced MSLN, a gene encoding mesothelin, was identified in metastatic TNBC cells and tissues using qRT-PCR, Western blotting, and immunohistochemistry. Dual-luciferase reporter assays, chromatin immunoprecipitation (ChIP) analysis, and bioinformatics were employed to identify transcription factors regulating MSLN. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), co-immunoprecipitation (co-IP), and immunofluorescence (IF) co-localization were utilized to investigate the mechanism of MSLN action in BC cells. Cellular viability was assessed using a colony formation assay. Cell proliferation and chemosensitivity were assessed using the CCK8 assay. Results: MSLN exhibits aberrantly overexpression in liver-metastatic cells. Elevated MSLN levels are significantly associated with liver metastasis compared to metastases in other organs. MSLN promotes cell proliferation and survival in vitro and TNBC liver metastasis in vivo. Mechanistically, MSLN binds to epidermal growth factor receptor (EGFR) and activates the EGFR-ERK1/2 signaling axis, thereby promoting TNBC cell survival and proliferation during metastasis. Notably, targeting MSLN with a paclitaxel/carboplatin combination can efficiently inhibit liver metastasis of hepatotropic TNBC in a mouse model.