Abstract A38: Aberrant expression of cell growth-critical genes in 4-nitroquinoline 1-oxide-induced mouse tumors and in human esophageal cancer tissues
Authors: Yang Zhengduo , Guan Baoxiang , Men Taoyan , Fujimoto Junya , Xu Xiaochun 
Published: January 2014

Background: An animal model of 4-nitroquinoline 1-oxide(4-NQO)-induced oral and esophageal cancer is useful in study of human diseases, but the underlying molecular events remain to be determined. Tobacco smoke, the major risk factor for human oral and esophageal squamous cell carcinoma, alters expression of certain cell growth-critical genes (e.g., p-ERK1/2, COX-2, and RAR-β2). This study aimed to detect expression of these genes in 4-NQO-induced mouse tumors and then in esophageal cancer cell lines and tissues for association with clinicopathological and survival data from patients.

Methods: C57LB6/129Sv mice were given in the drinking water to produce oral and esophageal cancers. qRT-PCR, Western blot, and immunohistochemistry were used to detect gene expressions in mouse tissues or human esophageal cancer tissues. Methylation-specific PCR and DNA sequence were performed to assess promoter methylation of RAR-β2 promoter. the Kaplan-Meier analysis was performed to associate gene expression with survival of patients.

Results: 4-NQO induced premalignant and malignant lesions in mouse oral cavity and esophagus in a dose-dependent manner, which pathologically and morphologically mimicked human oral and esophageal cancers. Molecularly, 4-NQO inhibited RAR-β2 but induced p-Erk1/2 and COX-2 expression and RAR-β2 gene promoter methylation in mouse tumors. In vitro treatment with 4-NQO altered expression of RAR-β2, p-Erk1/2, and COX-2 in esophageal cell lines. Ex vivo expression of p-Erk1/2 and COX-2 in 90 cases of esophageal cancer patients was upregulated and p-ERK1/2 expression was associated with advanced clinical tumor stage and consumption of hot beverage, while COX-2 expression was associated with tumor de-differentiation in esophageal cancers. Furthermore, expression of p-Erk1/2 was associated with worse overall survival of esophageal cancer patients (p = 0.014), while COX-2 expression didn't reach statistically significant (p = 0.19). Knockdown of COX-2 expression using transient transfection of a COX-2 antisense expression vector inhibited Ki67 expression, an indicator of cell proliferation, in esophageal cancer cells.

Conclusion: 4-NQO-induced lesions in mouse oral cavity and esophagus not only pathologically and morphologically mimicked human oral and esophageal cancers, but also shared some molecular alterations (e.g., aberrant expression of RAR-β2, p-Erk1/2, and COX-2). This study further demonstrated that targeting of the altered RAR-β2-led gene pathway could effectively suppress development of these now deadly cancers.

Citation Format: Zhengduo Yang, Baoxiang Guan, Taoyan Men, Junya Fujimoto, Xiaochun Xu. Aberrant expression of cell growth-critical genes in 4-nitroquinoline 1-oxide-induced mouse tumors and in human esophageal cancer tissues. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A38.