Cigarette Smoking, E-Cigarette Use Induces Stress and Production of Pro-Cancerous EVs by Bladder Cancer Cells

Exposure to cigarette smoke and electronic cigarettes (E-cigarettes) led to significant genotoxic and endoplasmic reticulum (ER) stress in bladder cancer cells, resulting in the release of extracellular vesicles (EVs) that promote transformation of normal urothelial cells, according to a study presented at the 2021 American Urological Association Annual Meeting. These findings, according to the study researchers, suggest the use of traditional cigarettes and E-cigarettes could drive bladder cancer onset and recurrence.

One of the most well-established risk factors for bladder cancer is cigarette smoking. In addition, preclinical evidence indicates E-cigarette exposure may also increase inflammation, oxidative stress, and genotoxic damage in certain tissues. Previous lab work has shown that BC cell-derived EVs induce neoplastic transformation of recipient urothelial cells. Few research studies, however, have identified how cigarette smoking and use of E-cigarettes impact the EV-mediated field cancerization effect.

To elucidate the role of cigarettes and E-cigarettes in bladder cancer, researchers exposed human bladder cancer cell lines to cigarette smoke extract (CSE), unflavored E-liquid (UEL), or menthol E-liquid (MEL). The investigators quantified EV biogenesis in the cell lines using nanoparticle tracking analysis.

Additionally, the researchers treated human uroepithelial cells (HUC) transformed with simian virus 40 (SV40) urothelial cells with EV protein cargos, identified by label-free quantitative LC-MS, for 5 to 15 weeks. These cells were subsequently subjected to clonogenic and migration assays to identify EV carcinogenicity. The researchers also examined genotoxic damage, stress, and apoptotic responses in EV recipient cells.

The results showed that CSE, UEL, and MEL led to DNA double-strand break formation as well as enhanced EV production in the bladder cancer cells. Neoplastic transformation was induced by chronic treatment of SV-HUC cells with the EVs, as reflected by enhanced colony formation and migration.

According to findings from proteomic analyses, the researchers observed that the EVs contained increased levels of ER stress response proteins, such as VCP and CALR, in addition to the dimeric DSB repair enzymes XRCCS/6. Increased DNA damage, ER stress response induction, and inflammatory signaling was also observed in SV-HUC cells treated with the EVs compared with cells treated with EVs from untreated bladder cancer cells.

While insightful, these findings require future larger-scale studies to determine the full extent cigarette smoking and E-cigarette use has on bladder cancer risk and prognosis. The researchers noted that there is currently an ongoing collection of primary bladder cancer patient urinary EV samples, including 26 from current smokers and 24 from non-smokers.