Deciphering the role of secretory leukocyte protease inhibitor (SLPI) in respiratory associated cancer

Abstract

Introduction
Respiratory diseases give rise to a considerable global health burden. SLPI possesses anti-proteolytic, anti-inflammatory and anti-bacterial activity. Our research primarily focuses on the role of SLPI in respiratory-associated cancers. Significantly elevated SLPI levels have been shown in lung adenocarcinoma (LUAD) patients compared to healthy controls, and SLPI overexpression was reported to significantly enhance tumour vascularisation. This thesis aims to interrogate how SLPI may play a role in tumour-associated angiogenesis by in vitro, ex vivo, and in vivo experimentation.

Methods
C57BL/6 WT and SLPI^-/- mice were sub-cutaneously injected with 5x10⁵ LLC cells. H&E staining and immunohistochemistry (IHC) was conducted for the endothelial cell (EC) marker, CD31, on excised tumours. EC pulldown was conducted on LLC tumours and healthy lung controls. Western blot (WB) analysis was carried out on the Tumour EC (TEC) and Lung EC (LEC) for alterations in SLPI with subsequent ELISA and qPCR being conducted for various markers. 1x10⁵ HUVEC cells were treated with VEGF, recombinant SLPI (rSLPI) or TEC supernatants for angiogenic and proliferation analysis.

Results and Conclusion
HUVECs cultured with rSLPI exhibited significantly increased enclosed structure, branching point numbers, and enhanced cell proliferation rate. Tumours from SLPI^-/- mice showed significantly diminished tumour burden, functional vessel number and vessel leakiness compared to WT mice. This loss in SLPI signifying that SLPI may promote angiogenesis explicitly signifying a role in a tumour angiogenesis. Future work will investigate the impact of combinational therapies on TECs in vitro and in vivo in our murine models.

Thesis is embargoed until 31 December 2028.

Date of Award	Dec 2023
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Donna Small (Supervisor), Christopher Scott (Supervisor) & Cristina Branco (Supervisor)