Hookah Smoke Mediates Cancer-Associated Epigenomic and Transcriptomic Signatures in Human Respiratory Epithelial Cells

Abstract

Introduction: Although communal smoking of hookah by means of water pipes is perceived to be a safe alternative to cigarette smoking, the effects of hookah smoke in respiratory epithelia have not been well characterized. This study evaluated epigenomic and transcriptomic effects of hookah smoke relative to cigarette smoke in human respiratory epithelial cells.Methods: Primary normal human small airway epithelial cells from three donors and cdk4 and hTERT-immortalized small airway epithelial cells and human bronchial epithelial cells were cultured for 5 days in normal media with or without cigarette smoke condensates (CSCs) or water pipe condensates (WPCs). Cell count, immunoblot, RNA sequencing, quantitative real-time reverse-transcriptase polymerase chain reaction, methylation-specific polymerase chain reaction, and quantitative chromatin immunoprecipitation techniques were used to compare effects of hookah and cigarette smoke on cell proliferation, global histone marks, gene expression, and promoter-related chromatin structure.Results: CSC and WPC decreased global H4K16ac and H4K20me3 histone marks and mediated distinct and overlapping cancer-associated transcriptome signatures and pathway modulations that were cell line dependent and stratified across lung cancer cells in a histology-specific manner. Epiregulin encoding a master regulator of EGFR signaling that is overexpressed in lung cancers was upregulated, whereas FILIP1L and ABI3BP encoding mediators of senescence that are repressed in lung cancers were down-regulated by CSC and WPC. Induction of epiregulin and repression of FILIP1L and ABI3BP by these condensates coincided with unique epigenetic alterations within the respective promoters.Conclusions: These findings support translational studies to ascertain if hookah-mediated epigenomic and transcriptomic alterations in cultured respiratory epithelia are detectable and clinically relevant in hookah smokers.

Smoking-associated Downregulation of FILIP1L Enhances Lung Adenocarcinoma Progression Through Mucin Production, Inflammation, and Fibrosis

“…To further examine this issue, we evaluated FILIP1L mRNA expression in more extensive NSCLC databases including paired tumor and NAT samples. Consistent with our previous report ( 13 ), FILIP1L mRNA expression was significantly decreased in both LUAD ( Fig. 1A ) and LUSC ( Supplementary Fig.…”

“…We have shown that FILIP1L mRNA levels are lower in LUAD and LUSC compared with unpaired normal lung tissues ( 13 ). To further examine this issue, we evaluated FILIP1L mRNA expression in more extensive NSCLC databases including paired tumor and NAT samples.…”

“…Cigarette smoking has been linked to aberrant DNA methylation in lung cancers ( 8, 9, 12 ). We previously showed that FILIP1L is downregulated by promoter methylation in normal human respiratory epithelial cells following short-term exposure to tobacco condensates ( 13 ). In our current experiments, FILIP1L downregulation was highly associated with FILIP1L promoter methylation in cultured LUAD cells, and FILIP1L repression as well as FILIP1L promoter methylation in LUAD specimens were significantly associated with cigarette smoking.…”

“…Recent transcriptomic and epigenomic analyses have demonstrated that Filamin A interacting protein 1-like ( FILIP1L ) is a key gene that is repressed by promoter DNA methylation in normal human small airway and bronchial epithelial cells following exposure to cigarette as well as hookah tobacco smoke ( 13 ). These findings extend our previous observations that FILIP1L is a novel tumor suppressor gene that is repressed by promoter methylation in several cancer histologies ( 14–18 ).…”

Role of Epiregulin in Lung Tumorigenesis and Therapeutic Resistance

“…Cigarette smoking is a wellknown risk factor for lung cancer [41], and carcinogens in cigarette smoke induce EREG upregulation in bronchial epithelial cells. The exposure of human bronchial epithelial cells to cigarette smoke extract upregulates EREG, which in turn promotes cell proliferation and protects against cigarette smoke-induced cytotoxicity [42,43]. The treatment of lung adenocarcinoma cells with benzo[a]pyrene, which is a potent carcinogen in cigarette smoke, increases EREG expression and promotes cell proliferation [44].…”