The Curious Case of TRPV2: From Endometrial Cancer biomarker to Pharmacological Target

TRP channels are remarkable proteins that decode physical and chemical stimuli into cellular behavior. Their role as cellular sensors modulating intracellular calcium concentration renders them interesting proteins to study in the context of cellular plasticity. Indeed, extracellular signaling factors driving phenotypic transitions require a secondary messenger to convey their effect onto the target. Due to its remarkable properties, calcium presents an ideal candidate to translate molecular messages from receptor to effector. Therefore, calcium-permeable ion channels that facilitate influx of extracellular calcium can exert major influence on the cellular phenotype. In a physiological context, altered expression of ion channels and Ca2+ homeostasis is required to induce cellular changes in response to a changing environment. However, dysregulation of the delicate balance between extracellular signals, their receptors and their signal transduction pathways can initiate a pathological state, where cells acquire characteristics that promote disease progression. Changes in TRP channel expression patterns might facilitate resilient and aggressive phenotypes, via alterations in intracellular Ca2+ homeostasis. This dissertation aims to investigate how TRP channel expression patterns are altered by phenotypic transitions in the endometrium, and how this translates into TRP channel signatures in endometrial cancer (EC). Using primary cultures of healthy human endometrial stromal and epithelial cells, RT-qPCR and calcium microfluometric imaging techniques; we were able to identify typical mesenchymal and epithelial TRP channel expression patterns. Most notably, TRPV2 expression was strongly associated with the mesenchymal phenotype, since induction of EMT increased the functional expression of the channel, while MET had the opposite effect. Interestingly, these characteristic epithelial and mesenchymal 'TRP fingerprints' were also observed in EC biopsies and cells with variable EMT status. Again, TRPV2 expression was strongly linked to mesenchymal marker gene expression. Moreover, TRPV2 mRNA expression correlated with pathophysiological parameters such as disease stage, myometrial invasion and disease recurrence. Interestingly, a gain-of function mutation of TRPV2 was identified in a patient diagnosed with high-risk EC, further underlining the possible importance of TRPV2 in EC development and progression. Our findings indicate that TRPV2 might prove and interesting target for EC research. However, TRPV2-related studies are drastically hampered by the lack of selective pharmacological tools. Therefore, we next aimed to identify new compounds that could modulate TRPV2 activity. A high-throughput compound screening of a repurposing library revealed a group of antihistamines as potent TRPV2 antagonists. Further characterization of these compounds using both microfluometric imaging techniques and patch clamp measurements, identified loratadine as the most potent TRPV2 antagonist, with limited effects on other TRP(V) channels. Moreover, loratadine was able to block endogenous TRPV2 in mouse endometrial stromal cells, and had an inhibiting effect on the migratory potential of these cells. More research will be necessary to elucidate the nature of the TRPV2-loratadine interaction, and to reveal whether or not TRPV2 inhibition might be responsible for the H1-receptor independent effects of loratadine. Taken together, these findings provide novel insights into how TRP channel expression patterns are connected to endometrial cell phenotypes in both health and disease, and lay the foundations for the discovery of new pharmacological tools to unravel the curious case of TRPV2.

Publication year:2021

Accessibility:Open