Identification of TAZ as the essential molecular switch in orchestrating SCLC phenotypic transition and metastasis

Small cell lung cancer (SCLC) is a recalcitrant cancer featured with high metastasis. However, the exact cell type contributing to metastasis remains elusive. Using Rb1 L/L /Trp53 L/L mouse model, we identify the NCAM hi CD44 lo/− subpopulation as SCLC metastasizing cell (SMC), which is progressively transitioned from non-metastasizing NCAM lo CD44 hi cell (Non-SMC). Integrative chromatin accessibility and gene expression profiling studies reveal an important role of SWI/SNF complex, and knockout of its central component, Brg1 , significantly inhibits such phenotypic transition and metastasis. Mechanistically, TAZ is silenced by SWI/SNF complex during SCLC malignant progression, and its knockdown promotes SMC transition and metastasis. Importantly, ectopic TAZ expression reversely drives SMC-to-Non-SMC transition and alleviates metastasis. Single-cell RNA-sequencing analyses identify SMC as the dominant subpopulation in human SCLC metastasis, and immunostaining data show a positive correlation between TAZ and patient prognosis. These data uncover high SCLC plasticity and identify TAZ as key molecular switch in orchestrating SCLC phenotypic transition and metastasis.