The Human Splice Variant Δ16HER2 Induces Rapid Tumor Onset in a Reporter Transgenic Mouse

University of California, Los Angeles, and Cedars-Sinai Medical Center, United States of America
PLoS ONE (Impact Factor: 3.23). 04/2011; 6(4):e18727. DOI: 10.1371/journal.pone.0018727
Source: PubMed


Several transgenic mice models solidly support the hypothesis that HER2 (ERBB2) overexpression or mutation promotes tumorigenesis. Recently, a HER2 splice variant lacking exon-16 (Δ16HER2) has been detected in human breast carcinomas. This alternative protein, a normal byproduct of HER2, has an increased transforming potency compared to wild-type (wt) HER2 receptors. To examine the ability of Δ16HER2 to transform mammary epithelium in vivo and to monitor Δ16HER2-driven tumorigenesis in live mice, we generated and characterized a mouse line that transgenically expresses both human Δ16HER2 and firefly luciferase under the transcriptional control of the MMTV promoter. All the transgenic females developed multifocal mammary tumors with a rapid onset and an average latency of 15.11 weeks. Immunohistochemical analysis revealed the concurrent expression of luciferase and the human Δ16HER2 oncogene only in the mammary gland and in strict correlation with tumor development. Transgenic Δ16HER2 expressed on the tumor cell plasma membrane from spontaneous mammary adenocarcinomas formed constitutively active homodimers able to activate the oncogenic signal transduction pathway mediated through Src kinase. These new transgenic animals demonstrate the ability of the human Δ16HER2 isoform to transform "per se" mammary epithelium in vivo. The high tumor incidence as well as the short latency strongly suggests that the Δ16HER2 splice variant represents the transforming form of the HER2 oncoprotein.

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    • "In addition to dasatinib, other tyrosine kinase inhibitors such as erlotinib, emodin, lapatinib and gefitinib are effective in treating trastuzumab-resistant breast tumors. (Marchini et al., 2011). "
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    ABSTRACT: HER2 overexpression has been observed in 20-30% of breast cancer cases. In addition to main products of HER2 gene, there are other variations, of which, the most important one is Δ16HER2. In principle, although HER2 overexpression is the first step for carcinogenesis, it is not sufficient, and the main reason responsible for breast tumorigenesis is Δ16HER2. This onco-protein, which lacks exon 16, can form stable homodimers remaining active constitutively. Like Δ16HER2, 611-CTF, a specific HER2 carboxy-terminal fragment, expresses a constitutively active homodimers. Therefore, targeting of Δ16HER2 and 611-CTF is the most promising strategy for treating HER2+ breast cancer. Along with inhibitors of HER2 gene products, miRNAs are also novel candidates for treatment of breast malignancy. Several drugs, working against different domains of the HER2 receptor, have been presented for treatment of HER2 positive breast cancers and they can increase mortality in patients.
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    • "Whole-mount sections of all mammary glands were prepared as described previously [24]. Briefly, mouse skin was removed and fixed overnight in 10% buffered formalin. "
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    ABSTRACT: The availability of mice transgenic for the human HER2 gene (huHER2) and prone to the development of HER2-driven mammary carcinogenesis (referred to as FVB-huHER2 mice) prompted us to study active immunopreventive strategies targeting the human HER2 molecule in a tolerant host. FVB-huHER2 were vaccinated with either IL-12-adjuvanted human HER2-positive cancer cells or DNA vaccine carrying chimeric human-rat HER2 sequences. Onset and number of mammary tumors were recorded to evaluate vaccine potency. Mice sera were collected and passively transferred to xenograft-bearing mice to assess their antitumor efficacy. Both cell and DNA vaccines significantly delayed tumor onset, leading to about 65% tumor-free mice at 70 weeks, whereas mock-vaccinated FVB-huHER2 controls developed mammary tumors at a median age of 45 weeks. In the DNA vaccinated group, 65% of mice were still tumor-free at about 90 weeks of age. The number of mammary tumors per mouse was also significantly reduced in vaccinated mice. Vaccines broke the immunological tolerance to the huHER2 transgene, inducing both humoral and cytokine responses. The DNA vaccine mainly induced a high and sustained level of anti-huHER2 antibodies, the cell vaccine also elicited interferon (IFN)-gamma production. Sera of DNA-vaccinated mice transferred to xenograft-carrying mice significantly inhibited the growth of human HER2-positive cancer cells. Anti-huHER2 antibodies elicited in the tolerant host exert antitumoral activity.
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    • "They can be used for preclinical testing of therapeutic agents against human p185, for example monoclonal antibodies (Finkle et al., 2004) that are not cross-reactive with rat HER-2. A more recent application of human HER-2 expression in transgenic mice was the establishment of mice carrying HER-2 variants found in patients, such as the Delta16 isoform (Castiglioni et al., 2006; Marchini et al., 2011), thus allowing the study of their carcinogenicity and the direct comparison between wild-type and variant or mutant forms of the HER-2 oncogene. "
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    ABSTRACT: Effective prevention of human cancer with vaccines against viruses, such as HBV and HPV, raises the question whether also non-virus related tumors could be prevented with immunological means. Studies in HER-2-transgenic mice showed that powerful anti-HER-2 vaccines, could almost completely prevent the onset of mammary carcinoma. Protective immune responses were orchestrated by T cells and their cytokines, and effected by antibodies against HER-2 gene product p185. Analogous findings were reported in a variety of other cancer immunoprevention systems, thus leading to the definition of oncoantigens, optimal target antigens that are causally involved in carcinogenesis and cancer progression. Prophylactic HER-2 vaccines were also effective in preventing metastasis outgrowth, indicating that concepts and approaches developed for cancer immunoprevention could prove fruitful in cancer immunotherapy as well. The availability of cancer-prone mice carrying a human HER-2 transgene is now fostering the design of novel vaccines against human p185. A further bridge toward human cancer was recently provided by novel immunodeficient models, like Rag2(-/-);Il2rg(-/-) mice, which are permissive for metastatic spread of human HER-2+ cancer cells and can be engrafted with a functional human immune system, allowing for the first time the study of vaccines against oncoantigens to elicit human immune responses against human cancer cells in vivo.
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