delta16HER2 splice variant and its role in HER2-overexpressing breast cancer

Deep insight on delta16HER2 splice variant and its role in HER2-overexpressing breast cancer

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

Several transgenic mice models solidly support the hypothesis that HER2 (ERBB2) overexpression or mutation promotes tumorigenesis. Recently, a HER2 splice variant lacking exon-16 (D16HER2) 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 D16HER2 to transform mammary epithelium in vivo and to monitor D16HER2- driven tumorigenesis in live mice, we generated and characterized a mouse line that transgenically expresses both human D16HER2 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 D16HER2 oncogene only in the mammary gland and in strict correlation with tumor development. Transgenic D16HER2 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 D16HER2 isoform to transform ‘‘per se’’ mammary epithelium in vivo. The high tumor incidence as well as the short latency strongly suggests that the D16HER2 splice variant represents the transforming form of the HER2 oncoprotein

Multiorgan Metastasis of Human HER-2+ Breast Cancer in Rag2−/−;Il2rg−/− Mice and Treatment with PI3K Inhibitor

In vivo studies of the metastatic process are severely hampered by the fact that most human tumor cell lines derived from highly metastatic tumors fail to consistently metastasize in immunodeficient mice like nude mice. We describe a model system based on a highly immunodeficient double knockout mouse, Rag2−/−;Il2rg−/−, which lacks T, B and NK cell activity. In this model human metastatic HER-2+ breast cancer cells displayed their full multiorgan metastatic potential, without the need for selections or additional manipulations of the system. Human HER-2+ breast cancer cell lines MDA-MB-453 and BT-474 injected into Rag2−/−;Il2rg−/− mice faithfully reproduced human cancer dissemination, with multiple metastatic sites that included lungs, bones, brain, liver, ovaries, and others. Multiorgan metastatic spread was obtained both from local tumors, growing orthotopically or subcutaneously, and from cells injected intravenously. The problem of brain recurrencies is acutely felt in HER-2+ breast cancer, because monoclonal antibodies against HER-2 penetrate poorly the blood-brain barrier. We studied whether a novel oral small molecule inhibitor of downstream PI3K, selected for its penetration of the blood-brain barrier, could affect multiorgan metastatic spread in Rag2−/−; Il2rg−/− mice. NVP-BKM120 effectively controlled metastatic growth in multiple organs, and resulted in a significant proportion of mice free from brain and bone metastases. Human HER-2+ human breast cancer cells in Rag2−/−;Il2rg−/− mice faithfully reproduced the multiorgan metastatic pattern observed in patients, thus allowing the investigation of metastatic mechanisms and the preclinical study of novel antimetastatic agents

Role of Delta16HER2 splice variant in breast tumor progression and response to HER2-Targeted therapy.

HER2 overexpression is necessary but not sufficient to induce malignant transformatio

Surgicopathologic outcome of laparoscopic versus open radical hysterectomy.

To compare the surgicopathologic outcome of total laparoscopic radical hysterectomy (LRH) with that of abdominal radical hysterectomy (ARH) for the treatment of early-stage cervical cancer.Radical hysterectomy specimens of sequential patients undergoing LRH (N=50) were compared with those of historical controls selected from consecutive women who have had conventional ARH (N=48), and who met the same criteria for eligibility as the cases. To evaluate the extent of parametrial resection, parametrial tissues were systematically measured at their widest dimensions before tissue processing.No difference was found in demographics, histologic type, tumor stage and grade between the two groups. The parametrial width was similar between LRH and ARH in both type II (right parametrium: 2.4 cm (1-3) vs. 2.3 (1.8-4.0), p=0.28; left parametrium: 2.3 cm (1.8-4) vs. 2.2 (1.2-3.0), p=0.54) and type III radical hysterectomy (right parametrium: 3.8 cm (2.3-6.5) vs. 3.4 (1.7-7.0), p=0.59; left parametrium: 3.6 cm (2-6) vs. 3.5 (1.5-6.5), p=0.82). There were no significant differences between the two groups with regard to lymph nodes yield and likelihood of identifying positive margins or metastatic disease.Our results suggest that laparoscopically managed patients with cervical cancer undergo a similar extent of surgery as those treated with the traditional ARH, as judged by objective pathologic criteria

Potential role of HER2-overexpressing exosomes in countering trastuzumab-based therapy

Exosomes are endosome-derived nanovesicles actively released into the extracellular environment and biological fluids, both under physiological and pathological conditions, by different cell types. We characterized exosomes constitutively secreted by HER2-overexpressing breast carcinoma cell lines and analyzed in vitro and in vivo their potential role in interfering with the therapeutic activity of the humanized antibody Trastuzumab and the dual tyrosine kinase inhibitor (TKI) Lapatinib anti-HER2 biodrugs. We show that exosomes released by the HER2-overexpressing tumor cell lines SKBR3 and BT474 express a full-length HER2 molecule that is also activated, although to a lesser extent than in the originating cells. Release of these exosomes was significantly modulated by the growth factors EGF and heregulin, two of the known HER2 receptor-activating ligands and naturally present in the surrounding tumor microenvironment. Exosomes secreted either in HER2-positive tumor cell-conditioned supernatants or in breast cancer patients' serum bound to Trastuzumab. Functional assays revealed that both xenogeneic and autologous HER2-positive nanovesicles, but not HER2-negative ones, inhibited Trastuzumab activity on SKBR3 cell proliferation. By contrast, Lapatinib activity on SKBR3 cell proliferation was unaffected by the presence of autologous exosomes. Together, these findings point to the role of HER2-positive exosomes in modulating sensitivity to Trastuzumab, and, consequently, to HER2-driven tumor aggressiveness