Abstract A01: Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells
Authors: Bauer Alison K. , Siegrist Katelyn J. , Plöttner Sabine , Brüning Thomas , Käfferlein Heiko U. 
Published: June 2022

Rationale: Polycyclic aromatic hydrocarbons (PAHs) are prevalent contaminants in our environment, workplace, and in first- and secondhand smoke from both cigarettes and marijuana. The toxicity of low molecular weight (LMW) PAHs compared to high molecular weight PAHs (e.g., benzo[a]pyrene, B[a]P) is not well studied in lung cells. Our overall hypothesis was that LMW PAHs act as cocarcinogens in the presence of a known carcinogen (B[a]P) in human and mouse lung epithelial cells. Gap junctions are commonly suppressed during tumor promotion, while DNA-adduct formation and micronuclei (MN) are observed during the initiation stage of cancer. We used these endpoints together as markers of carcinogenicity in Beas2B and C10 cells.

Methods: Beas2B, a human bronchial epithelial cell line, and C10 cells, a nontumorigenic type II alveolar pneumocyte cell line, were used. LMW PAHs (1-methylanthracene, 1-MeA, and fluoranthene, Flthn) were applied in a 1:1 ratio mixture based on previous studies and B[a]P as a classic carcinogen. Cells were treated for 30 min.-24 h with the LMW PAH mixture, B[a]P, or both, and assessed for the following endpoints: cytotoxicity, genotoxicity (MN), apoptosis, proliferation, gap junctional intercellular communication (GJIC) by the lucifer yellow scalpel-loaded/dye-transfer assay, and DNA adducts of B[a]P by HPLC with fluorescence detection in C10 cells.

Results: LMW PAHs are more cytotoxic in the human Beas2B cells than the mouse C10 cells. Significant toxicity is observed in Beas2B cells at 0.3 uM B[a]P combined with the LMW PAH mixture (0.1-1 uM), while no toxicity is observed in C10 cells at identical doses. No significant apoptosis was observed in Beas2B cells while significant increases in S-phase were observed in response to B[a]P combined with LMW PAH mixture compared to B[a]P alone. B[a]P in combination with the LMW PAH mixture significantly inhibited GJIC in C10 and Beas2B cells compared to B[a]P or the LMW PAH mixture alone, supporting a role for GJIC suppression in cancer development. B[a]P diol-epoxide (BPDE)-DNA adduct levels were also significantly induced in C10 cells at 1.0 uM B[a]P with the LMW PAH mixture at several doses (less than or equal to 1.0 uM) and significant increases in BPDE-DNA adduct formation compared to B[a]P alone were observed. Lastly, MN were also observed in both cell lines and significantly differed between B[a]P alone and in combination with the LMW PAH mixture. DNA adduct formation and genotoxicity coincided with GJIC inhibition.

Conclusion: These studies provide evidence that LMW PAHs in combination with B[a]P can elicit increased carcinogenic potential in human and mouse cells.

Support: Flight Attendant Medical Research Institute (CIA130022, AKB); the National Institute for Environmental Health Sciences (R15ES024893, AKB).

Citation Format: Alison K. Bauer, Katelyn J. Siegrist, Sabine Plöttner, Thomas Brüning, Heiko U. Käfferlein. Environmentally prevalent polycyclic aromatic hydrocarbons elicit cocarcinogenic properties in human and mouse lung cells [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A01.