
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.08.23.609469
preprint
1
Article
E-cigarettes increase the risk of adenoma formation in murine colorectal cancer model
Sayed Ibrahim M http://orcid.org/0000-0001-8207-6401

Chakraborty Anirban
Inouye Kaili
Dugan Leanne
Tocci Stefania
Advani Ira
Park Kenneth
Hazra Tapas K
Das Soumita http://orcid.org/0000-0003-3895-3643

Crotty Alexander Laura E.
26 8 2024
2024.08.23.609469https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.08.23.609469
nihpp-2024.08.23.609469.pdf
Abstract

Background

E-cigarettes (E.cigs) cause inflammation and damage to human organs, including the lungs and heart. In the gut, E.cig vaping promotes inflammation and gut leakiness. Further, E.cig vaping increases tumorigenesis in oral and lung epithelial cells by inducing mutations and suppressing host DNA repair enzymes. It is well known that cigarette (cig) smoking increases the risk of colorectal cancer (CRC). To date, it is unknown whether E.cig vaping impacts CRC development.

Methods

A mouse model of human familial adenomatous polyposis (CPC-APC) was utilized wherein a mutation in the adenomatous polyposis coli (APC) gene, CDX2-Cre-APC Min/+ , leads to the development of colon adenomas within 16 weeks. Mice were exposed to air (controls), E.cig vaping, cig, or both (dual exposure). After 4 weeks of 2-hour exposures per day (1 hour of each for dual exposures), the colon was collected and assessed for polyp number and pathology scores by microscopy. Expression of inflammatory cytokines and cancer stem cell markers were quantified. DNA damage such as double-strand DNA breaks was evaluated by immunofluorescence, western blot and gene-specific long amplicon qPCR. DNA repair enzyme levels (NEIL-2, NEIL-1, NTH1, and OGG1) were quantified by western blot. Proliferation markers were assessed by RT-qPCR and ELISA.

Results

CPC-APC mice exposed to E.cig, cig, and dual exposure developed a higher number of polyps compared to controls. Inflammatory proteins, DNA damage, and cancer stemness markers were higher in E-cig, cig, and dual-exposed mice as well. DNA damage was found to be associated with the suppression of DNA glycosylases, particularly with NEIL-2 and NTH1. E.cig and dual exposure both stimulated cancer cell stem markers ( CD44, Lgr-5, DCLK1, and Ki67). The effect of E.cigs on polyp formation and CRC development was less than that of cigs, while dual exposure was more tumorigenic than either of the inhalants alone.

Conclusion

E.cig vaping promotes CRC by stimulating inflammatory pathways, mediating DNA damage, and upregulating transcription of cancer stem cell markers. Critically, combining E.cig vaping with cig smoking leads to higher levels of tumorigenesis. Thus, while the chemical composition of these two inhalants, E.cigs and cigs, is highly disparate, they both drive the development of cancer and when combined, a highly common pattern of use, they can have additive or synergistic effects.
==== Body
pmc
