Long‐term exposure to extremely low‐dose of nicotine and 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (NNK) induce non‐malignant breast epithelial cell transformation through activation of the a9‐nicotinic acetylcholine receptor‐mediated signaling pathway

Abstract

Breast cancer (BC) is the most common cancer affecting women worldwide and has been associated with active tobacco smoking. Low levels of nicotine (Nic) and 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanone (NNK), have been detected in cases of second‐hand smoke (SHS). However, the correlation between SHS and BC risk remains controversial. In this study, we investigated whether the physiological SHS achievable dose of Nic and tobacco specific nitrosamine, NNK act together to induce breast carcinogenesis using an in vitro breast cell carcinogenesis model. Immortalized non‐tumorigenic breast epithelial cell line, HBL‐100 used for a time‐course assay, was exposed to very low levels of either Nic or NNK, or both. The time‐course assay consisted of 23 cycles of nitrosamines treatment. In each cycle, HBL‐100 cells were exposed to 1pM of Nic and/or 100 femtM of NNK for 48 hours. Cells were passaged every 3 days and harvested after 10, 15, and 23 cycles. Our results demonstrated that the tumorigenicity of HBL‐100, defined by soft agar colony forming, proliferation, migration and invasion abilities, was enhanced by co‐exposure to physiologically SHS achievable doses of Nic and NNK. In addition, α9‐nAChR signaling activation, which plays an important role in cellular proliferation and cell survival, was also observed. Importantly, an increase in stemness properties including the prevalence of CD44+/CD24− cells, increase Nanog expression and mammosphere‐forming ability were also observed. Our results indicate that chronic and long term exposure to environmental tobacco smoke, may induce breast cell carcinogenesis even at extremely low doses.

The α9 Nicotinic Acetylcholine Receptor Mediates Nicotine-Induced PD-L1 Expression and Regulates Melanoma Cell Proliferation and Migration

“…Many studies indicate that nicotine induces breast cancer growth and metastasis in vitro and in vivo through binding to and activating α9-nAChR [20,23,30,31]. Long-term exposure to extremely low doses of nicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced nonmalignant breast epithelial cell transformation through activation of the α9-nAChR-mediated signaling pathways [32]. However, the mechanisms by which nicotine-induced α9-nAChR activity promotes melanoma growth and metastasis are not fully understood.…”

α9-Containing Nicotinic Receptors in Cancer

“…As it is still debated whether exposure to second-hand smoke (SHS) affects the risk of breast cancer, Fararjeh et al (2019) used a model of breast cell carcinogenesis in which immortalized normal human breast epithelial cells exposed to a carcinogen undergo long-term exposure to 1 pM nicotine and/or 100 femtM NNK doses (that can be reached during exposure to SHS). They found that repeated co-exposure to nicotine and NNK disrupted cell growth control and led to the acquisition of cancer cell properties, and increased the levels of a number of α9 nAChR downstream signaling proteins, such as the FAK migration marker and the PI3K/Akt intracellular signaling pathway.…”

Exploring neurotransmitters and their receptors for breast cancer prevention and treatment

“…Indeed, the interaction of nicotine and its derivatives with nAChRs has been well linked to the development of many types of cancers 144 . In particular, a number of studies have shown that exposure to nicotine or NNK induces malignant transformation of normal breast epithelial cells and promotes proliferation and metastasis of BC cells 145 . This is supported by epidemiological findings that cigarette smoking is associated with increased BC risk.…”