Tributyltin and triphenyltin isothiocyanates down-regulate immune check-point receptors, but not HLA G in human triple-negative breast carcinoma MDA-MB-231 cell line.

Introduction

Programmed Death 1 receptor (PD-1) is expressed in activated T-lymphocytes, B-lymphocytes, mononuclear cells, NK cells and some dendritic cells. As a consequence of PD-L1 ligand binding to PD-1 is down-regulation of T-cell activity. Human leukocyte antigen G (HLA-G) is an immunotolerant nonclassical major histocompatibility complex Class Ib molecule, overexpressed in tumors and involved in cancer immune evasion.

We combined anticancer/genotoxic properties of two chemically different types of molecules, triorganotins and isothiocyanate,into tributyltin isothiocyanate (TBT-ITC) and triphenyltin isothiocyanate (TPT-ITC) and recently have shown their genotoxic effects in human breast carcinoma MCF 7 and MDA-MB-231 cell lines. In this study, we demonstrate immunomodulatory properties of their non-genotoxic concentrations in tripple negative human breast cancer cell line MDA-MB-231.

Material and Method

To select the optimal compounds concentrations that do not affect cell viability, the MTT test has been used. Conventional comet assay and its modification – incubation of cells with styrene oxide (StO) were used for the detection of DNA damage as DNA breakage as well as DNA crosslinks formation. PDL-1 and HLA G expression were determined by flow cytometry.

Results and Discussion

100 nM concentration of studied compounds has been selected for further in vitro experiments based on MTT test for 48 h. This concentration kept the viability of cells over 93%. Comet assay did not reveal the presence of DNA breaks or crosslinks in MDA-MB-231 cells after 24 h treatment with both ITC derivatives, indicating their non genotoxic potential at low 100 nM concentrations. Immune-regulatory properties of tested derivatives were demonstrated by flow cytometry and displayed down-regulation of PD-L1 molecule after 24 hour incubation with 100 nM concentration of both triorganotin isothiocyanates. However, these compounds did not modulate HLA G expression.

Conclusion

Serious interests in novel organotin compounds are undoubtebly increasing due to their possible use in clinical oncology. Here, we demonstrated down-regulation of an immune regulatory molecule that suppresses the anticancer tumor PD-L1 response on the surface of MDA-MB-231 cells after TBT-ITC and TPT-ITC treatment. These triorganotin compounds did not alter HLA G expression.

Funding Study was supported by the Slovak Research and Development Agency Grant APVV-15-0372, the Scientific Grant Agency of the Ministry of Education of Slovak Republic and the Academy of Sciences (VEGA) grants 2/0084/16 and 1/0136/18, the project 315/2019/FaF (IGA UVPS Brno) and also the following project implementations: TRANSMED, ITMS: 26240120008 and ITMS: 26240220071 supported by the Research & Development Operational Programme funded by the ERDF.