Identification and regulation of EMT cells <i>in vivo</i> by laser stimulation

Cells undergoing epithelial-to-mesenchymal transition (EMT) exhibit significant plasticity, making them more tumorigenic, invasive, and stem-like. PLCG2 has been identified as being linked to EMT. Specifically, the PLCG2-high subpopulation of tumor cells shows strong correlations with metastasis. However, it remains unclear whether PLCG2 serves as a direct driver of EMT. In this study, we employ an <i>in vivo</i> photostimulation method using tightly focused femtosecond-laser scanning to activate intracellular Ca²⁺ signaling and induce PLCG2 upregulation. By constructing a subcutaneous tumor model with prostate cancer PC3 cells and single-cell RNA sequencing, we identify distinct cell populations, including cancer stem cells, epithelial tumor cells, proliferating cells, and EMT cells. Upon photostimulation, EMT cells are notably expanded among the primary tumor cells, while epithelial tumor cells decrease in number. During the tumor progression, treatment with a specific PLCG2 inhibitor effectively suppresses the growth of the primary tumor but has no significant impact on metastatic cells. These findings offer valuable insights into the role of PLCG2 in regulating EMT and tumor development.