COX‐2 upregulation in thymomas and thymic carcinomas

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Abstract
The treatment of advanced stage thymomas and thymic carcinomas is a multimodal therapy. New therapeutic targets are currently under investigation, including the epidermal growth factor receptor (EGFR) as well as KIT. A number of studies have shown protumorigenic potential of Cyclooxygenase‐2 (COX‐2) in a variety of human malignancies, but so far it is unknown whether COX‐2 is expressed in primary malignancies of the thymus. Using tissue microarrays, the expression of COX‐2, microsomal‐PGES‐1 and ‐PGES‐2 (mPGES‐1 and mPGES‐2), as well as EGFR was evaluated in different subtypes of thymoma and thymic carcinomas. COX‐2 was expressed in all subtypes as determined by immunohistochemistry. Some cases of type B2 and thymic carcinomas had COX‐2 staining levels classified as mild to moderate. However, when measuring the optical color intensity, no significant differences could be detected. Concerning the expression levels, a weak correlation between the expression of COX‐2, mPGES‐1 and mPGES‐2 as well as EGFR was found. Furthermore, additional cases of thymomas and thymic carcinomas were analyzed by COX‐2 Western immunoblot analysis and were compared to normal thymi. The analysis showed that thymomas and thymic carcinomas had a significantly stronger COX‐2 expression than that of the normal thymi (p < 0.04). In summary, COX‐2 is expressed in all subtypes of thymomas and thymic carcinomas and thus represents, in addition to EGFR and KIT, a potential therapeutic target. Further studies are needed in order to determine whether a combined therapy using COX‐2 inhibitors in addition to the evolving anti‐EGFR antibody therapy may be considered as a treatment option.
Funding Information
  • Tumorzentrum Heidelberg/Mannheim (TZ Periode 2005-2007/FSPII./.6)
  • Deutsche Dr. Mildred Scheel Stiftung (Ke10-2080)
  • National Genome Research Network (NGFN/No. 01 GR 0417)