Testung und Etablierung von ALK1-Inhibitoren als potentielle Therapeutika in der Prävention der Metastasierung von TGF-β2 sekretierenden Melanomen
Zusammenfassung der Projektergebnisse
Cutaneous melanoma is one of the most aggressive form of skin cancer with an increasing incidence worldwide. While AJCC staging guides patient management and treatment stratification, the current criteria within this staging system are unable to identify high risk early stage I or II tumour subsets, leaving an urgent need for novel prognostic and companion biomarkers markers for stratified personalised treatment. Recent publication by the host group, showed that the combined loss of epidermal differentiation proteins AMBRA1, an autophagy regulatory protein, and Loricrin, a marker of terminal keratinocyte differentiation, (AMLo) is a highly sensitive and specific prognostic biomarker for non-ulcerated AJCC stage I melanoma. Furthermore, initial observations by the Lovat group also indicate loss of epidermal AMBRA1 overlying primary melanomas is also associated with the loss of endothelial AMBRA1 expression in surrounding blood and lymphatic vessels, leading to the aim of the present study of deciphering the mechanisms leading to loss of epidermal and endothelial AMBRA1 and the potential role of the TGF-β signalling pathway. Results revealed a significant correlation between increased melanoma TGF-β2 secretion and loss of epidermal AMBRA1, with increased TGF-β2 secretion by AJCC stage I melanomas also significantly associated with a high-risk AMLo status and tumour metastasis. A significant correlation between loss of epidermal AMBRA1 and loss of Claudin1 expression was also observed in AJCC stage I and II melanomas, with AMLo high risk stage II melanomas exhibiting signs of pre-ulceration, such as epidermal consumption, loss of rete ridges and cleft formation. qPCR analysis further revealed mRNA expression of the TGFβ receptor ALK5, but not ALK1, by primary keratinocytes with chemical inhibition of ALK5 resulting in prevention of TGF-β2–induced activation of psmad2/3 and AMBRA1 and Claudin1 downregulation. Studies in the endothelial cell line HUVEC, revealed exogenous TGFβ2 impaired cellular differentiation as shown by a significant reduction in cell junctions, meshes and total network length as well as a reduction in Claudin5 expression. However, there were no observed effects of TGF-β2 on AMBRA1 expression by HUVEC cells. Collectively, these data define the mechanisms by which TGF-β2 secretion by high risk primary early stage melanomas leads to epidermal AMBRA1 downregulation and subsequent loss of epidermal integrity thereby facilitating tumour ulceration. Specifically, TGF-β2 evokes canonical TGF-β2/ALK5 receptor mediated activation of p-Smad 2/3 resulting in loss of AMBRA1 and subsequent AMBRA1-dependent loss of Loricrin and Claudin1. However, while TGF-β2 secretion by primary melanomas leads to loss of epidermal AMLo and likely contributes to tumour ulceration as well as loss of endothelial integrity and metastasis, this signalling pathway does not appear to contribute to the loss of endothelial AMBRA1 expression, suggesting differing TGF-β superfamily ligands may contribute to loss of endothelial AMBRA1.
Projektbezogene Publikationen (Auswahl)
- Melanoma secretion of TGFβ2 mediates epidermal AMBRA1 and Claudin1 downregulation, loss of epidermal integrity and tumour ulceration. Journal of Investigative Dermatology 139 (9), S299
I Cosgarea, A Mc Connell, D Tang, A Greenwood, R Ellis, P Lovat
(Siehe online unter https://doi.org/10.1016/j.jid.2019.07.543) - Melanoma transforming growth factor-beta 2 secretion leads to loss of endothelial integrity and tumour metastasis. British Journal of Dermatology 180 (6), E197-E198
A McConnell, I Cosgarea, F Shekleton, A Murry, R Ellis, D Tang, M Labus, M Corazzari, J Armstrong, P Lovat
