Houston Methodist Research Institute/ Hong Zhao*
The activation of the epithelial-to-mesenchymal transition (EMT) program is a critical step in cancer progression and metastasis, but visualization of this process at the single cell level, especially in vivo, remains challenging. We established an in vivo approach to track the fate of tumor cells based on a novel EMT-driven fluorescent color switching breast cancer mouse model and intravital two-photon laser scanning microscopy. Specifically, the MMTV-PyMT, Rosa26-RFP-GFP, and Fsp1-Cre triple transgenic mouse model was used to monitor the conversion of RFP-positive epithelial cells to GFP-positive mesenchymal cells in mammary tumors under the control of the Fsp1 (ATL1) promoter, a gate-keeper of EMT initiation. RFP-positive cells were isolated from the tumors, sorted, and transplanted into mammary fat pads of SCID mice to monitor EMT during breast tumor formation. We found that the conversion from RFP to GFP-positive and spindle-shaped cells was a gradual process, and that GFP-positive cells preferentially localized close to blood vessels, independent of tumor size. Furthermore, cells undergoing EMT expressed high levels of the HGF receptor, c-Met, and treatment of RFP-positive cells with the c-Met inhibitor, cabozantinib, suppressed the RFP-to-GFP conversion in vitro. Moreover, administration of cabozantinib to mice with palpable RFP-positive tumors resulted in a silent EMT phenotype whereby GFP-positive cells exhibited reduced motility, leading to suppressed tumor growth. In conclusion, our imaging technique provides a novel opportunity for visualizing tumor EMT at the single cell level and may help to reveal the intricacies underlying tumor dynamics and treatment responses.
Zhao Z1, Zhu X1, Cui K1, Mancuso J1, Federley R1, Fischer K2, Teng G3, Mittal V2, Gao D2, Zhao H4, Wong ST5.
1Department of Systems Medicine and Bioengineering, The Houston Methodist Hospital Research Institute.
2Cardiothoracic Surgery, Neuberger Berman Lung Cancer Research Center & Cell and Developmental Biology, Weill Cornell Medicine.
3Department of Radiology, Southeast University.
4Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute Hzhao@tmhs.org.
5Department of Systems Medicine and Bioengineering, The Houston Methodist Research Institute.