High Fat Diet Increases HMGB1 Levels in 4NQO‐Induced Oral Cancer

Abstract

IntroductionHMGB1 is a nuclear protein that binds to DNA and regulates gene transcription. HMGB1 can be released from the nucleus to function as a stress signal and/or a chemokine. HMGB1 overexpression has been reported in various cancers. The purpose of this study was to characterize the patterns of cytoplasmic HMGB1 expression in normal and cancerous mouse tongue tissues. Oral squamous cell carcinoma was induced by administration of 4‐nitroquinonline 1‐oxide (4NQO) in drinking water. 4NQO mimics the effects of tobacco and is a well‐established model of oral cancer in mice. In addition, we examined whether gender and high and low in saturated fat diets (HF and LF, respectively) could modify cytoplasmic levels of HMGB1. We hypothesized that higher levels of cytoplasmic HMGB1 will be present in tumor lesions and that gender and diet will affect the levels of expression.Materials and methodsMale and female C57Bl/6 mice (36 each gender), 5 weeks old, were divided into a low fat (10kcal% fat; LF) or HF (60 kcal% fat) diet. Within each dietary group, mice were randomly assigned to one of 3 water treatment groups for 17 weeks: water alone (control); propylene glycol in water (1.25%; PG‐H2O); or 4NQO in PG‐H2O (50 mg/ml; 4NQO). After 17 weeks, all mice were given water alone for 6 weeks prior to euthanasia. The presence of oral lesions, their size and location were monitored and recorded weekly. Upon sacrifice, tongues were harvested, formalin fixed, and processed for histological evaluation. Tongue tissue sections were stained with anti‐HMGB1 antibody (AB18256, Abcam Inc.) and examined microscopically. To evaluate localization and intensity of HMGB1 staining ImageJ program IHC profiler was used. The scale 0–3 was employed to measure the intensity of HMGB1 cytoplasmic staining.ResultsEpithelial cancer lesions were characterized by significantly higher levels of cytoplasmic HMGB1 than control epithelium (1.4–1.8 versus 0.8, p<0.01). Expression of cytoplasmic HMGB1 was limited to cancer lesions since unaffected areas of tongue epithelium from 4NQO animals showed low levels of HMGB1 (0.74–1.0), similar to the control animals (0.8). HMGB1 levels were higher in cancer lesions from HF diet than from LF diet animals (1.8 in HF, 1.4 in LF, p=0.0003). In addition, cancer lesions in females (LF and HF diets combined) showed higher levels of HMGB1 than in males (1.7 versus 1.3, p=0.008).ConclusionCytoplasmic expression of HMGB1 is limited to oral squamous carcinoma cells. HMGB1 may contribute to the tumor progression. Higher levels of HMGB1 in tumors from HF diet animals provide more evidence that HF diet may exacerbate cancer development. HMGB1 could serve as a cancer biomarker and as a therapeutic target.Support or Funding InformationWe recognize the Midwestern University Deans of CDMI and the Basic Science Division for their support of this research. Student research was supported by the Office of Research and Sponsored Programs and the Biomedical Sciences Division.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.