Pharmacological Modulation of Cancer Migration and Invasion Through Targeting AQP1 Ion and Water Channel Activity

Abstract

Cancer invasion and metastasis are the leading causes of cancer-related deaths. Aquaporin-1 is a dual water and ion channel that is upregulated in many aggressive cancers including colon, breast, and brain cancer; aquaporin-1 enhances cell migration, invasion and metastasis in these cancer types. Other aquaporins with water channel function are not able to substitute for aquaporin-1 in facilitating cell migration. There is a gap in knowledge regarding the properties of aquaporin-1 that permit its migration-enhancing effect, but both the ion and water channel activities appear to be involved. Thus, it was hypothesised that aquaporin-1 water and ion channels exhibit a coordinated role in aquaporin-1-facilitated cancer cell motility. The aims of this thesis were to test whether pharmacological block of the aquaporin-1 water and ion channel would impede cell migration and invasion in aquaporin-1-expressing cancer cell lines, and to see if the efficacy of aquaporin-1 inhibitors depended on membrane localisation of the channel. Proposed aquaporin-1 blocker AqB050, AQP1 water channel blocker bacopaside II, and an aquaporin-1 ion channel blocker AqB011 were used. The circular wound closure assay is an innovative alternative approach for measuring cell migration and was introduced and utilised in this thesis. Cell viability and proliferation was quantified using an alamarBlue assay. Cell invasion was measured with the transwell assay. Glioblastoma, colorectal adenocarcinoma, and mammary gland tumour cell lines were used. Results showed that combined pharmacological inhibition of aquaporin-1 water and ion conductance amplified the block of cancer cell migration as compared to block by each inhibitor alone, suggesting a cooperative role of aquaporin-1 water and ion channels in cell migration. Cancer cells that express aquaporin-1 on the membrane were more sensitive to block by aquaporin-1 inhibitors; this could be an important screening tool for identifying cancer subtypes likely to respond to AQP1 inhibitors. AqB011 and AqB050 inhibited glioblastoma, breast and colon cancer invasiveness. A newly generated mixture of compounds (AqB051) containing the proposed AQP1 blocker AqB050 and related derivatives was found to strongly block cancer transwell invasion. The potent biologically active agent (not AqB050) was then narrowed to one fraction (fraction E) from AqB051. AqB051 and fraction E significantly inhibited invasiveness in all glioblastoma cell lines. Work in this thesis paves the way for improving methods utilized for measuring cell migration, investigating the role of AQP1 ion conductance and subcellular localisation in cancer migration and growth, investigating a novel and potent inhibitor for glioblastoma invasion, and testing the effects of AQP1 modulators in treating other non-neoplastic diseases.