The dissemination of oncogenic RasV12-transformed cells in the adult Drosophila intestine

Abstract

Dissemination of transformed cells is a key process in metastasis. Despite its importance, how transformed cells disseminate from an intact tissue and enter the circulation is poorly understood. Here, we use a fully developed tissue, Drosophila midgut, and describe the morphologically distinct steps and the cellular events occurring over the course of RasV12-transformed cell dissemination. Notably, RasV12-transformed cells formed the Actin- and Cortactin-rich invasive protrusions that were important for breaching the extracellular matrix (ECM) and visceral muscle. Next, employing this Drosophila model of cell dissemination, we uncovered the essential roles of the mechanosensory channel Piezo in orchestrating dissemination of RasV12-transformed cells. Moreover, we demonstrate that the cell adhesion protein E-cadherin (E-cad) is necessary for the invasiveness of RasV12-transformed cells in vivo, challenging the prior perceived principle of the inverse relationship between E-cad levels and cell invasion. We demonstrate that Drosophila E-cad/beta-catenin disassembles at adherens junctions and assembles at invasive protrusions during cell dissemination. Loss of E-cad attenuates dissemination of RasV12-transformed cells by impairing their ability to compromise the ECM. Furthermore, we show that the remodeling of E-cad/beta-catenin subcellular distribution is controlled by two discrete intracellular calcium signaling pathways: Ca2+ release from endoplasmic reticulum via the inositol triphosphate receptor (IP3R) disassembles E-cad at adherens junctions while Ca2+ entry via Piezo assembles E-cad at invasive protrusions. Thus, our study provides molecular insights into the unconventional role of E-cad in cell invasion during cell dissemination in vivo and describes the discrete roles of intracellular calcium signaling in the remodeling of E-cad/beta-catenin subcellular localization. Collectively, our study establishes an in vivo model for studying how transformed cells migrate out from a complex tissue and provides unique insights into the roles of E-cad, IP3R, and Piezo in invasive cell behavior.