The human epidermal growth factor receptor-2 gene (HER-2) encodes for a membrane-bound tyrosine kinase (Her-2), which is overexpressed in various human cancers. Her-2-targeted therapy has recently been shown to be beneficial for patients with advanced gastric cancer. Her-2 protein expression was investigated in 341 esophageal carcinomas [152 squamous cell carcinomas (SCC), 189 adenocarcinomas (AC)], 39 cases of Barrett mucosa, and 11 cases of squamous cell dysplasia. HER-2 gene amplification was assessed by colorimetric in-situ hybridization. Positive Her-2 status was found in 15.3% of ACs and 3.9% of SCCs. Positive Her-2-status was more common in dysplastic Barrett mucosas compared with nondysplastic ones (P=0.04). In 26% of the patients with ACs who had received neoadjuvant chemotherapy (n=39), the Her-2 status of pretherapeutic biopsies was different compared with subsequent surgical specimens. There was no statistically significant correlation between Her-2 status and patients' survival. Although Her-2 overexpression is rare in SCCs, it is found in 15.3% of ACs, where amplification of HER-2 gene and overexpression of Her-2 protein seem to be early events in carcinogenesis. The evaluation of Her-2 status in tumor biopsies and in particular in the context with possible alterations after neoadjuvant treatment can potentially lead to false Her-2-staging. Although Her-2-overexpression in esophageal cancer seems to have no influence on patients' survival, these subtypes of esophageal ACs have to be considered as targets for an anti-Her-2 therapy.

High CAIX expression is associated with shorter survival in esophageal cancer, and the hypoxic phenotype seems to be preserved at least during formation of lymph node metastases. Inhibition of CAIX might reduce the ability of tumor cells to establish disseminated disease. In Her-2 overexpressing ACs, blocking of this tyrosine kinase, e.g., by monoclonal antibodies, might induce this effect.

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The signal-transcriptional factor signal transducer and activator of transcription (STAT3) is overexpressed in various tumor entities and promotes tumor progression and metastasis. The tyrosine-kinase receptor Her-2 was shown to activate STAT3-expression and is overexpressed in a subtype of esophageal cancer (EC). STAT3 also regulates carbonic anhydrase IX (CAIX) expression in vivo, promoting IL-6-dependent tumor invasion.Tumor-tissue from 324 patients with EC and 45 patients with precursor lesions were analyzed for the expressions of tyrosine-705 phosphorylated STAT3 (pSTAT3). Data on Her-2-status and CAIX expression were available from previous studies. pSTAT3 was overexpressed in 40 % of adenocarcinomas (AC) and 50 % of squamous cell carcinomas of the esophagus and was associated with worse overall (OS) (p = 0.001) and disease free survival (DFS) (p = 0.001). In Barrett's mucosa without/low-grade dysplasia, pSTAT3 was expressed in 14 % compared to 27 % in patients with high-grade dysplasia (p = 0.018). A significant association between Her-2 and pSTAT3 was found in ACs (p = 0.013), showing that patients with tumors expressing both proteins have significantly worse OS (p = 0.0039) and DFS (p = 0.029). One hundred-fifty (46.3 %) cancer cases were considered as positive for CAIX expression, and a strong correlation between pSTAT3 and CAIX expression was seen (p < 0.001). pSTAT3 plays an important role in the development of AC. Expression of pSTAT3 correlates with Her-2 status and CAIX expression and is associated with tumor progression and worse outcome, offering expectantly therapeutical implications.