Research Article Studying the Anticancer Effects of Thymoquinone on Breast Cancer Cells through Natural Killer Cell Activity Huda F. Alshaibi , 1,2 Nouf A. Aldarmahi, 1 Nuha A. Alkhattabi , 1 Hadeil M. Alsufiani , 1,3 and Nesrin I. Tarbiah 1 1 Biochemistry Department, Faculty of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia 2 Embryonic Stem Cell Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia 3 Experimental Biochemistry Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia Correspondence should be addressed to Huda F. Alshaibi; halshaibi@kau.edu.sa Received 26 June 2022; Revised 22 August 2022; Accepted 24 August 2022; Published 20 September 2022 Academic Editor: Yue Gu Copyright © 2022 Huda F. Alshaibi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cancer immunotherapy is quickly growing and can now be viewed as the “fifth column” of cancer treatment. In addition, cancer immunotherapy has shown promising results with different kinds of cancers and may be used as a complementary therapy with various types of treatments. Thus, “immuno-oncology” is showing astounding advantages. However, one of the main challenges that face this type of therapy is that cancer cells can evade immune system elimination through different mechanisms. Many studies were done to overcome this issue including adding immune stimulants to generate synergistic effects or by genetically modifying NK cells themselves to be stronger and more resistant. Nigella sativa, also known as black cumin, is a well-known example of a widely applicable herbal medicine. It can effectively treat a variety of diseases, such as hypertension, diabetes, bronchitis, gastrointestinal upset, and cancer. The anticancer qualities of Nigella sativa appear to be mediated by an immune- modulatory effect that stimulates human natural killer (NK) cells. These are a type of lymphocyte and first line of defense against pathogens. Objectives. In this study, we investigated the therapeutic effect of thymoquinone, a major component of Nigella sativa, on the cytotoxic pathways of NK cells. Methods. NK cells were cultured with breast cancer cell line Michigan Cancer Foundation-7 (MCF-7); and were treated with Thymoquinone. The cytotoxicity of NK cells on cancer cells was measured. The cultured media were then collected and measured via enzyme-linked immunosorbent assay (ELISA) for concentrations of perforin, granzyme B and interferon-α (IFN-α). Results. The cytotoxic effect of NK cells on tumor cells was increased in the presence of thymoquinone, with an increased release of perforin, granzyme B, and IFN-α. Conclusion. Thymoquinone promotes the cytotoxic activity of NK cells against breast cancer MCF-7 cells. 1. INTRODUCTION Breast cancer is one of the main causes of death in women according to the world health organization [1]. It is a metas- tatic and commonly spreads from its origin to distant organs of the body, with the most common sites of distant metasta- ses being bone, liver, lungs, and brain [2]. Breast cancer is a heterogeneous disease [3] at the histological and biological levels due to genetic, epigenetic, and transcriptome changes. This phenotypic difference influences breast cancer diagno- sis, treatment, and thus prognosis. Thus, initially treatment of breast cancer was depending on tumor characteristics such as its clinical stage, histopathologic features, and bio- marker profiling. However, in the last few decades, our understanding of its biological and molecular characteristics has improved [4]. We can now classify breast cancer to five subtypes according to molecular profiling, hormone indica- tors, and growth factor expressions. These subtypes are luminal A and B, human epidermal growth factor receptor 2 (HER2) enriched, triple-negative or basal-like (BL), and normal- like BC. Luminal A subtype is characterized by high expression of luminal gene and hormone receptors genes including estrogen receptor (ER) and progesterone receptors (PR). Luminal B subtype is characterized by expressing Hindawi BioMed Research International Volume 2022, Article ID 9218640, 8 pages https://doi.org/10.1155/2022/9218640