Suppressive effect of Thymoquinone on NLRP3 pathway in breast cancer: a novel multi-strike CALR and sec-PD-L1 inhibitor

Abstract

Inflammasome is activated when pattern recognition receptor (PRR) senses danger signals such as Calreticulin (CALR) from damaged\dying cells leading to secretion of Interleukin-1β (IL-1β). High levels of CALR mediated invasive breast cancer (BC) phenotype. The NOD-like receptor (NLR) family Pyrin domain-containing protein3 (NLRP3) inflammasome showed various tumor promoting effects in BC. Interestingly, IL-1β led to endocrine resistance in Estrogen receptor positive (ER+) BC patients and enhanced production of matrix metalloproteinases (MMP), which provoked cleavage and secretion of programmed death ligand-1 (PD-L1) from surface of tumor cells. Recently, studies reported that high levels of secreted PD-L1 (sec-PD-L1) were associated with poor prognosis in triple negative breast cancer (TNBC). The current study searched for a natural product that can target sec-PD-L1 and NLRP3 pathway in TNBC and hormone receptor positive (HR+) subtypes. Thymoquinone (TQ); a natural phytochemical derived from Nigella Sativa seeds was an excellent candidate since it inhibited NLRP3 inflammasome in human and mouse melanoma. Blood samples were collected from forty-five BC patients, comprising TNBC and HR + BC subtypes. The present study investigated the impact of different TQ concentrations for distinct durations on expression of CALR, NLRP3 complex components and IL-1β as well as the protein levels of sec-PD-L1 and IL-1β in peripheral blood mononuclear cells (PBMCs) and Tumor associated macrophages (TAMs), respectively. The current findings showed that TQ significantly downregulated expression of CALR, NLRP3 components and IL-1β together with protein levels of secreted IL-1β and sec-PD-L1. Thus, collectively TQ is a novel multi-strike inhibitor highlighting its potential roles as an excellent adjuvant and a promising immunotherapeutic agent in HR + and TNBC patients.