Inactivation of E-cadherin by Trop-2 drives colon cancer metastasis.

105 Background: Tumor metastasis is the main cause of death of colon cancer patients and the biggest hurdle for cancer cure. We set to identify decisive drivers and of pivotal therapy targets for colon cancer metastasis. Methods: IHC analysis quantified the expression of target molecules in primary tumors and metastases. Cell-cell adhesion capacity was assessed in vitro and in HCT116 colon cancer cell spheroids. Pre-clinical models of orthotopic growth of KM12SM colon cancer cells and metastatic diffusion to the liver were utilized to assess metastatic spreading force of wtTrop-2 and of the constitutively-active, tail-less form of Trop-2 (Δcyto). Xenotransplant and metastasis transcriptomes were analyzed for differential induction of EMT determinants. Kaplan–Meier plots were used to illustrate survival and metastatic relapse in independent case series of colon cancer patients. Results: wtTrop-2 was shown to induce wound-healing. ΔcytoTrop-2 further increased cell migration ability. Both wtTrop-2 and ΔcytoTrop-2 induced resistance to apoptosis in vitro and in vivo. wtTrop-2 strikingly increased the metastatic capacity of KM12SM cells, raising metastasis rates from 45% for control cells to 90% for wtTrop-2 transfectants. The constitutively-active ΔcytoTrop-2 further boosted metastatic spreading, with metastatic livers reaching up to four times their normal size. Cancer metastases revealed high levels of E-cadherin, in the absence of transcriptional down-regulation. EMT transcription factors were largely missing from Trop-2-activated cells. Rather, binding to Trop-2 was shown to cause the release of E-cadherin from the cytoskeleton, loss of cell-cell adhesion and activation of β-catenin. This global, Trop-2/E-cadherin/β-catenin-driven pro-metastatic program was recapitulated in colon cancer patients and was shown to impact on colon cancer metastatic relapse and overall patient survival. Conclusions: We identify Trop-2-driven functional inactivation of E-cadherin as a widespread driver of metastatic diffusion in colon cancer, opening novel avenues for personalized diagnostic procedures and anti-cancer therapies. [Table: see text]