FUNCTIONAL ROLES OF AQUAPORIN 5 IN BREAST CANCER METASTATIC INITIATION MODELED IN VITRO

Abstract

Despite causing 90% of cancer-related deaths, metastasis remains untargeted by widely available therapeutics. This deficiency of viable treatments stems from the field’s lack of foundational knowledge underlying the mechanistic progression of metastasis. Scientists have extensively used standard in vitro and in vivo models to study the disease state. However, these models are widely recognized for their limited translatability to human cancers. Commonly used in vitro models drastically oversimplify the physical, biochemical, and cell-to-cell cues that would normally be experienced within the tumor microenvironment (TME); conversely, the in vivo models employed lack the ability for long-term real-time data acquisition necessary to delineate the mechanisms underlying cancer metastasis. Limitations of both model types have drastically mitigated a physiologically relevant understanding of metastatic initiation and, thus, the discovery of appropriate markers for facilitating this progression. Aquaporins (AQPs) are a family of transmembrane water channel proteins that could act as regulators of metastatic initiation. Some AQP isoforms are significantly overexpressed in cancer cells and the TME, contributing to enhanced cancer proliferation, rates of metastasis, adoption of aggressive states, and, most extensively studied, cell motility. Yet the field’s understanding of AQP-mediated metastasis is inherently insubstantial, derived entirely from these limited in vitro and in vivo models. This dissertation elucidates the impact of the pro-metastatic isoform AQP5 on enhanced cell motility within complex in vitro microenvironments. To accomplish this, AQP5’s role in tumor progression was assessed from biological and biophysical perspectives. Additionally, in vitro models were developed and validated to better study AQP5’s involvement in metastatic initiation. This dissertation presents a newly identified mechanism by which AQP5 facilitates spheroid invasion, along with AQP5-based corruption of TME-resident cells and its role in promoting pro-metastatic cellular mechanical properties. Additionally, it characterizes a new model to study how biophysical cues dictate AQP5-mediated cell dynamics and introduces an in vitro system designed to recapitulate metastatic initiation.