Dicarbonyl stress enhances tumor intravasation

Abstract

Metastasis of cancer is a multi-step process that involves the migration of transformed cells from their native organ into a vascular channel, followed by their dissemination to prospective sites of colonization. The entry of tumor cells into blood or lymph, known as intravasation involves their breaching the stromal and endothelial extracellular matrix (ECM) and the endothelial barriers. How the kinetics of these cell-ECM interactions are confounded by chronic inflammatory stresses seen in comorbid risk factors of cancer such as diabetes and aging remain ill-investigated. Here, we construct and deploy a histopathology-motivated, imaging-tractable, microfluidic multi-organ-on-chip platform, that seamlessly integrates two tissue environments: that of a breast tumor and a vascular channel, to study the problem. The former comprises invasive triple-negative MDA-MB-231 breast cancer cells embedded within a three-dimensional fibrillar Collagen I milieu. The latter consists of a monolayer of TeloHAEC, immortalized human aortic endothelial cells arranged on laminin-rich basement membrane ECM, both of which concentrically line a hollow channel, wherein unidirectional fluid flows are implemented. The chip showcases the complexity of intravasation, wherein tumor cells and endothelia cooperate to form anastomotic structures. The formation of such structures is regulated by fluid flow in the vascular channel and is associated with cancer cell migration and entry into the vascular channel. Disseminated cancer cells are observed to enter, get adhered within, and flow through the vascular channel. Exposure to methylglyoxal (MG), a mediator of dicarbonyl stress associated with diabetic circulatory milieu, leads to greater cancer cell intravasation and flow through the vascular channel. This could be driven not just by MG-induced endothelial senescence and shedding, but also by the effect of MG on the chip ECM: we demonstrate it can degrade basement membrane and pathologically crosslink Collagen I, diminishing their cell adhesiveness. Our results thus show how dicarbonyl stress may attenuate homoeostatic barriers to cancer intravasation, exacerbating metastasis.