E-cadherin: Unexpected actor of invadopodia formation in pancreatic cancer

Invasion/metastasis axis is the major driver of cancer mortality. By maintaining tissue cohesion, E-cadherin is considered as a protective marker for tumoral progression. However, recent studies suggested that the appearance of hybrid epithelial-mesenchymal (E/M) cells still expressing E-cadherin is favourable for the establishment of metastasis. This hypothesis is consistent with the observation that most pancreatic ductal adenocarcinomas (PDAC) are invasive and express E-cadherin in primary tumour and metastases. By using a data constituted by a series of patient-derived xenografts (PDX) from the PaCaOmics multi-centric clinical trial, we show that E-cadherin expression is not associated with stages of the pathology, prognosis, and overall survival in PDAC. The role of E-cadherin in PDAC aggressiveness was tested both in vitro and in cancer cell implantation models. We show that E-cadherin is a key component of membrane protrusions implicated in the extracellular matrix remodelling and degradation, called invadopodia. E-cadherin downregulation in a pancreatic model of E/M hybrid cells reveals that E-cadherin downregulates Arp2/3 complex expression. As this complex is essential for branched actin structure, E-cadherin depletion strongly impaired invadopodia formation. On the other hand, we demonstrate that E-cadherin interacts with the membrane protease MT1-MMP at the in-vadopodial membrane. E-cadherin could be recycled back to the invadopodial membrane simultaneously with MT1-MMP. Indeed, both Rab7 vesicle-dependant and/or a Rab11 vesicle-dependant pathway are required for both E-cadherin and MT1-MMP trafficking. This new localization of E-cadherin and its implication in cell invasion shines a new light on hybrid EMT features in tumoral invasion.