Differential Expression Of COX-2and RAR-β₂and Their Association In Esophageal Cancer Tissue Specimens

Background: Esophageal cancer is one of the most common human malignancies inChina with a high incidence and a poor survival rate. To date, the molecularmechanisms responsible for esophageal carcinogenesis remain to be defined, althoughthere are a number of risk factors that were established for esophageal carcinoma, suchas tobacco smoking, alcohol consumption, and environmental pollutants. These factorscould alter the expression of various cell growth-critical genes that associate withtumorigenesis and cancer promotion （e.g. COX-2and EGFR）, but suppress theexpression of other genes that are frequently lost in the development of differenttobacco-related cancers （e.g. RAR-β₂and p53）. Previous studies in the laboratorydemonstrated that some of these genes might coordinate each other in vitro to form agene pathway; thus, better understanding of the risk factor-altered or mediated signalingtransduction pathway could provide insightful information towards to define themolecular mechanisms responsible for esophageal carcinoma development andprogression, which could lead to effective control of this now-deadly disease in future.Objective: The current study was to investigate the differential expression of RAR-β₂vs. COX-2mRNA and mTOR vs. Akt protein in normal and cancerous esophagealtissues for association with clinicopathological features from esophageal cancer patients.This study could provide ex vivo data to support the role of these gene alterations inesophageal carcinogenesis and cancer progression and to identify novel biomarkers inearly diagnosis or prediction of esophageal cancer progression.Methods: A total of33fresh tissue specimens from esophageal cancer patients wererecruited from The First Affiliated Hospital of Anhui Medical University, Hefei, China between October2010and January2011. The specimens, including both esophagealsquamous cell carcinoma and the corresponding noncancerous tissues, were obtainedfrom surgery and immediately snap-frozen in liquid nitrogen and stored in-80oC untiluse. Real-time fluorescent quantitative reverse transcription polymerase chain reactiontechnique was used to detect expression levels of COX-2and RAR-β₂in these tissuesamples. Immunohistochemistry was performed to analyze the expression of mTOR andAkt proteins in formalin-fixed and paraffin-embedded tissue sections. Expression ofthese four genes were then compared and associated with clinicopathological data fromthe cancer patients.Results: The qRT-PCR data showed that RAR-β₂expression was significantly lower incancerous tissue specimens than that of the corresponding normal tissues （P <0.05） andaltered RAR-β₂expression was associated with tumor de-differentiation （P <0.05） anddrinking of hot liquid, such as hot tea （i.e. temperature equal or more than70oC; P <0.05）. In contrast, expression of COX-2mRNA was significantly higher in canceroustissue specimens than that of the corresponding normal tissues （P <0.05）, whichassociated with consumption of the pickled vegetables （P <0.05）, but didn’t statisticallyassociated with tobacco smoking, excessive alcohol drinking, or age and gender of thepatients. Furthermore, expression of mTOR and AKT proteins was significantly higherin cancerous tissue specimens than that of the normal tissues （P <0.05）. Specifically,mTOR protein was expressed in28.6%and52.1%cases of normal esophageal mucosaeand malignant esophageal tissues, respectively, while expression of AKT proteinoccurred in20.2%and42.6%cases of normal esophageal mucosae and malignantesophageal tissues, respectively. The increased expression of these two proteins betweennormal and malignant esophageal tissues was statistically significant （χ²=10.175, P <0.05and χ²=10.148, P <0.05, respectively）.Conclusions: The data from the current study demonstrated that differential expressionof these four genes in esophageal cancer tissue specimens is associated with various clinicopathological parameters from the patients. Further study will investigate theirrole in esophageal cancer and verify them as biomarkers in esophageal cancer earlydiagnosis and prognosis.