A Novel Immunological Role of Hydrogen Sulphide in Shaping Natural Killer Cells Cytoxicity in Breast Cancer Patients

Abstract

Abstract Background Triple Negative Breast cancer (TNBC) is a complex challenging disease that is not amenable to conventional treatment. Our research group has recently portrayed hydrogen sulphide (H2S) and its synthesizing enzymes, cystathionine β-synthase (CBS) and cystathionine-γ-lyase (CSE), as potent oncogenic mediators for TNBC progression. Recently, H2S has been casted as a potential modulator of cancer immune surveillance as well. Yet, the impact of H2S on the immunological profile of TNBC cells has never been investigated. Natural Killer (NK) cells are the native sentinels of the immune system that plays an indisputable role in TNBC-immune surveillance. TNBC immune suppressive tumour microenvironment is also rate-limiting step when immunotherapeutic approaches are tackled in case of TNBC patients. Thus the main aim of this study is to identify the role of endogenous H2S on NK cells' activating ligands present on TNBC cells, immune suppressive tumour microenvironment and net effect on NK cells cytotoxicity. Methods Breast tissues were collected from 80 BC patients. ER, PR, HER-2 and Ki-67 levels were quantified using immunohistochemistry. MDA-MB-231 and MCF7 cells were cultured and transfected with different oligonucleotides. Total RNA was extracted and quantified by qRT-PCR. IFN-γ and TNF-α in cellular supernatant was measured using representative ELISA kits. NK cells were isolated from 30 healthy controls. The cytotoxicity of NK cells was measured using LDH Cytotoxicity Assay. Results MICA, MICB and ULBP2 were significantly down-regulated in TNBC tissues and cell lines. Knocking down of CBS and CSE using siRNAs resulted in a marked increase in MICA/B and ULBP2 expression in MDA-MB-231 cells. Nonetheless, knocking down of CBS and CSE resulted in a marked induction in IFN-γ production and attenuation of TNF-α levels. Upon co-culturing with healthy NK cells, Knocking down of endogenous H2S resulted in a marked increase in NK cells cytotoxicity. Conclusion This study showed that knocking down of CBS and CSE resulted in a improving NK cells cytotoxicity and alleviating tumor-induced immune suppressive microenvironment in TNBC patients. Legal entity responsible for the study German University in Cairo. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.