Abstract 4595: STAT-3 chemical inhibition modulates decidual-like polarization in NK cells from PCa patients and restore their anti-tumor activities
Authors: Gallazzi Matteo , Palano Maria Teresa , Cucchiara Martina , Dehò Federico , Capogrosso Paolo , Franzi Francesca , Sessa Fausto , Naselli Angelo , Mortara Lorenzo , Bruno Antonino 
Published: April 2023

Abstract
Introduction. Natural Killer (NK) cells are innate lymphoid cells involved in tumour recognition/elimination. NK cells are altered in their phenotype and functions in diverse tumors, including prostate cancer (PCa). We demonstrated that PCa circulating NK cells (TANKs) acquire the pro-angiogenic/decidual-like CD56brightCD9+CD49a+ phenotype, release IL-8 and MMP-9, functionally support endothelial cell activation and secrete monocyte-recruiting/M2-like macrophage-polarizing factors.
Materials and methods. Here, we characterized the phenotype of tumour infiltrating NKs (TINKs) and tumour-associated (TANKs) in PCa patients and evaluated the contribution of STAT3, as possible driver of NK cell polarization. PCa TINKs and TANKs were characterized by multicolour flow cytometry (FC) for decidual-like surface markers (CD9, CD49a) and degranulation capabilities (CD107a). STAT3 activation, was investigated in circulating PCa NK cells, by FC. Using a drug-repurposing approach with the antipsychotic agent Pimozide (a chemical inhibitor of STAT3), we modulated STAT3 activation, ex vivo, in PCa TANKs and monitored their secretome changes, by commercially available protein membrane arrays together with their capability to degranulate and produce perforin/GranzymeB.
Results and discussion. We observed that PCa TINKs acquire the same CD9+CD49a+ decidual-like NK cell phenotype, as found in PCa TANKs. We detected the presence of CD56brightCD9+CD49a+ decidual-like NK cell also in peripheral blood of subjects with benign prostatic hyperplasia (BPH), but in a lower frequency, compared to those from PCa TANKs. Sera from PCa patients were enriched in IL-4, IL-6, IL-8 and IL-10, all cytokines able to activate STAT3 signalling. We detected increased phosphorylation of STAT3 in PCa TANKs, compared to NK cells from healthy controls, that was reduced following 24 hours of stimulation by Pimozide. This treatment resulted in decreased capabilities of PCa TANKs to secrete pro-angiogenic factors (IL-8, IL-6), molecules involved in monocytes recruitment/M2-like macrophage polarization (CCL-2, CCL5, GM-CSF, IL-10), together with increased degranulation, augmented secretion of (IFN-γ and TNF-α) and increased production of Perforin and Granzyme.
Conclusions. Our results suggest that STAT3 inhibition can be envisaged as a potential strategy to limit the generation of pro-angiogenic/decidual-like NKs, while contributing to NK cell re-education in PCa.
Citation Format: Matteo Gallazzi, Maria Teresa Palano, Martina Cucchiara, Federico Dehò, Paolo Capogrosso, Francesca Franzi, Fausto Sessa, Angelo Naselli, Lorenzo Mortara, Antonino Bruno. STAT-3 chemical inhibition modulates decidual-like polarization in NK cells from PCa patients and restore their anti-tumor activities. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4595.