Wnt signaling-mediated activation of cancer cell stemness in thoracic SMARCA4-deficient undifferentiated tumor cells

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UT) represent a distinct and highly aggressive malignancy characterized by SMARCA4 deficiency, poor prognosis, and resistance to chemotherapy. The lack of clarity regarding the regulatory mechanisms underlying this disease has hindered the development of standardized treatment guidelines. In this study, we analyzed clinical samples and found significantly elevated levels of cancer stem cell markers, including SOX2, CD34, c-Myc, and EpCam, in thoracic SMARCA4-UT, which were further confirmed in SMARCA4-deficient non-small cell lung cancer (NSCLC) cells. Furthermore, SMARCA4 knockdown in NSCLC cells promoted cell proliferation, migration, invasion, and tumorsphere formation in vitro, as well as enhanced tumor growth in a mouse model in vivo. RNA sequencing analysis of SMARCA4-deficient cells revealed the upregulation of a subset of genes, including Wnt10A, and activation of Wnt signaling. This was validated through SMARCA4-ChIP-seq and SMARCA4-ChIP-PCR analyses, Wnt activity reporter assays, and subcellular distribution analysis of β-catenin. Subsequent studies using a small molecule Wnt inhibitor in SMARCA4-deficient cells and thoracic SMARCA4-UT patient-derived organoids demonstrated induction of apoptosis, inhibition of cell stemness, and suppression of tumor cell growth. These results suggest the potential for developing a novel therapeutic strategy targeting cancer stem cells for the treatment of thoracic SMARCA4-UT.