HER2 has been implicated in biliary carcinogenesis, because gene amplification of HER2 has been observed in 20% of gallbladder carcinoma (GBC) (Kawamoto, et al. GCR 2007). The first-in-class HER2 dimerization inhibitor (HDI) pertuzumab is a humanized monoclonal antibody that binds HER2 at an epitope that prevents HER2 from dimerizing with ligand-activated HER family receptors, In this study, we determined the expression of HER family proteins in GBC, cholangiocellular carcinoma(CC), and examined whether treatment with pertuzumab would affect GBC and CC cell lines. Methods: HER family expression was examined in surgical or biopsied specimens from 47 GBCs and 57 CCs by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Using 6 GBC and 8 CC cell lines, heregulin-stimulated cell proliferation and its inhibition by pertuzumab, were tested in vitro by MTT assay. The phosphorylated HER family proteins and their respective downstream molecules were examined by Western blot analysis. Anti-tumor activity of pertuzumab in vivo was evaluated in the CC cell line KMCH-1 xenograft model with weekly intraperitoneal administration. Results: Over-expression of HER2 or HER3 was observed in 14-34% of all patients (Table 1). Six of 14 cell lines demonstrated over-expression of both HER2 and HER3, and heregulin stimulation increased the proliferation in 3 of them. In the HER2- and HER3- over-expressing KMCH-1, pertuzumab significantly inhibited cell proliferation in a dose-dependent manner. Pertuzumab completely blocked heregulin-induced phosphorylation of HER3. Furthermore, suppression of downstream pathway molecules including pAKT and pS6 were observed. The xenograft model also revealed tumor growth inhibition with pertuzumab. Conclusions: Pertuzumab demonstrated significant antitumor activities in HER2 and HER3 over-expressing cancer cells. Thus, pertuzumab may provide a new therapy option for both HER2- and HER3- positive GBC and CC.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1684. doi:1538-7445.AM2012-1684
e22083 Background: ErbB2 has been known to be important for gallbladder carcinogenesis. Supporting this, the gene amplification of HER2 was found in ca. 20% of human gallbladder carcinoma (GBC) (Kawamoto, et al. Gastrointest Cancer Res 2007). Following these results, a Phase II study of trastuzumab for treatment of GBC (NSC 688097) is being conducted. Although the mechanism of HER2 activation is not well understood, the role of HER3 in HER2-driven tumorigenesis has been discussed and we have concluded that HER2/HER3 heterodimerization might be important for GBC cell proliferation (ASCOGI 2009, ab#155). In this study, we determined HER family expressions in human GBC and examined the effect of pertuzumab against human GBC cell lines. Methods: Tissues from 47 GBCs and 6 non-cancerous gallbladders were examined. All cases were screened for HER1, HER2, HER3 expressions by immunohistochemistry (IHC) and those HER family gene amplification by fluorescence in situ hybridization (FISH) were performed. 6 human GBC cell lines were also analyzed by Western blotting and FISH as well and their growth assays were investigated with heregulin stimulation to confirm the existence of HER2/HER3 heterodimerization. Then, GBC cells were cultured with heregulin and various doses of pertuzumab for 72 hours and CCK-8 assay was performed. Results: HER3, HER2 and HER1 overexpression by IHC was found in 34%, 32% and 19% of GBCs, respectively. Phosphorylated (p-) HER2 and p-HER1 were found in 23% and 11% of GBCs, respectively. FISH analysis was considered successful in the same serial sections. HER3, HER2 and HER1 FISH (+) was found in 26%, 19% and 4% of GBCs, respectively. Three of 6 GBC cell lines were recognized their growth curves with heregulin were increasing. These 3 cell lines showed good responses to the treatment with pertuzumab. Conclusions: More than 20% of GBC over-expressed either HER2 or HER3. These HER2 and HER3 may form heterodimer, which in turn results in the activation of HER2. The cell lines proliferating with the administration of heregulin showed good responses to the pertuzumab treatment. Therefore, HER2/HER3 heterodimerization may be an ideal biomarker for the treatment by pertuzumab and this agent may be a new therapeutic regimen for GBC. No significant financial relationships to disclose.
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