HER-2 oncoprotein

It is known that HER-2 signaling enhances metastasis in breast cancer cells by inducing endothelial cell retraction, a process that appears to precede endothelial transmigration (Carter et al., 2001). In other words, breakdown of the vascular barrier caused by HER-2 

It is interesting to note that expression and secretion of an aberrant HER-2 splice variant has been reported in various cell lines and tissues, which can interfere with the oncogenic HER-2 activity (Aigner et al., 2001). Expression of this truncated 100-kDa HER-2 variant encodes the extracellular domain of HER-2 and inhibits growth factor-mediated tumor cell proliferation. The exact role played by this variant during the progression of human cancer is not clear. 

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Three main techniques have been used for detecting HER-2 oncoprotein overexpression Western blot analysis, enzyme-linked immunosorption assay (ELISA), and immunohistochemistry. Western blot analysis is limited to basic research rather than routine clinical... 

Another considerable observation is the relationship between the expression of HER-2 oncoprotein and the expression of steroid hormone receptors. Tumors vfith HER-2 overexpression show usually a low expression level of estrogen and progesterone receptors, while tumors with a high expression level of estrogen and progesterone receptors often lack overexpression of the HER-2 oncoprotein. Moreover, there is an inverse relationship between the expression of the bd-2 oncoprotein and the expression of both HER-2 and EGER. It is also interesting to mention that BRCA-1- and BRCA-2-related breast carcinomas are rarely associated with HER-2 overexpression. 

The overexpression of the HER-2 oncoprotein is an important prognostic factor for breast cancer and the following aspects must be considered ... 

Primary tumors with heterogeneous cell populations exhibiting different expression intensity of the HER-2 oncoprotein and consequently different scores, must be particularly documented. In such cases, the assessment of metastatic tissue to determine the metastasizing cell population is recommended. This phenomenon is described in about 5% of breast tumors. 

V8. Visakorpi, T., Kalloniemi, O. P., Koivula, T., Harvey, J., and Isola, J., Expression of epidermal growth factor receptor and erbB2 (HER-2/Neu) oncoprotein in prostatic carcinomas. Mod. Pathol. 5, 643-648 (1992). 

Zalutsky M R, Xu F J, Yu Y, et al. (1999). Radioiodinated antibody targeting of the HER-2/neu oncoprotein Effects of labeling method on cellular processing and tissue distribution. Nucl. Med. Biol. 26 781-790. 

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