Effects Of The Risk Variants In ADH1B And ALDH2 Coupled With Alcohol Consumption On Esophageal Squamous Cell Carcinoma And Tumor Microenvironment

Numerous epidemiological studies have confirmed that heavy alcohol drinking is one of the important etiological factors in esophageal squamous-cell carcinoma(ESCC).Two single-nucleotide polymorphisms,rs1229984 in the gene for alcohol dehydrogenase 1B(ADH1B)and rs671 in the aldehyde dehydrogenase-2(ALDH2)gene were identified as important susceptibility polymorphisms for ESCC in a gene and alcohol consumption interactive manner.Alcohol(ethanol)is a toxic substance mainly oxidized by ADHs to carcinogenic aldehyde,which is further oxidized by ALDHs,forming nontoxic acetate.Therefore,it is reasonable that individuals with risk variants for these dehydrogenases might accelerate the production or slow down the degradation of aldehyde,both leading to accumulation of aldehyde in tissues,consequently resulting in increased ESCC risk from gene and environmental interactions.As the first metabolite of alcohol oxidation,aldehyde is highly toxic and mutagenic,is considered to be "carcinogenic to humans",and plays a central role in alcohol-associated carcinogenesis,including ESCC.Numerous in vitro and in vivo experiments in prokaryotic and eukaryotic cell cultures,as well as in animal models,have shown that aldehyde interferes at many sites affecting DNA synthesis and repair,and has direct mutagenic effects,resulting in DNA damage.In line with these findings,our previous work showed that alcohol drinkers with germline variants of ADH1 Band ALDH2 harbored more somatic mutations induced by DNA damage,demonstrating that alcohol intake in individuals with risk variants of ADH1B and ALDH2 might aggravate genomic instability.However,recent studies also found that somatic mutations may emerge in physiologically normal esophageal epithelial cells,indicating that tumorigenesis relies not only on genome aberrations but also on interactions with different cell populations in the tumor microenvironment.We previously have applied single-cell RNA sequencing(scRNA-seq)on a large scale in cells from ESCC tumors to provide important insights into the cellular heterogeneity of ESCC at single-cell resolution.We identified eight epithelial expression programs with different functions,as well as a large number of tumorpromoting and immunosuppressive cell populations enriched in the TME.Of note,one of the epithelial programs was characterized by epithelial mucosal defense function,and was identified as a potential prognosis marker.In addition,we deciphered the dynamic transition of fibroblasts in the TME and found that the accumulation of cancer-associated fibroblasts(CAFs)may play crucial roles in tumor progression.Moreover,we have found that regulatory T(Treg)and exhausted T(Tex)cells were more enriched in ESCC tumors compared with adjacent normal tissues,and were mostly responsible for causing immunosuppression in the TME.These complex ecosystems may have important impacts in shaping the intricate dynamic network of tumorigenesis and need to be further elucidated.Therefore,in the present study,we created a mouse model mimicking human ESCC development and constructed a single-cell ESCC developmental atlas.Meanwhile,we leveraged our previous scRNA-seq data to illuminate how alcohol exposure and variants of these two dehydrogenases(rs 1229984 and rs671 genotypes)could interact with TME cellular and molecular dynamics to promote ESCC progression.