Abstract
BackgroundAlong with de novo resistance, continued exposure to trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2/neu) antibody, can lead to acquired resistance. In this study, we characterize a new anti-HER2/neu antibody resistant and metastatic mouse breast carcinoma cell line, TUBO-P2J. This cell line was developed during in vivo experiments using the antibody sensitive and non-metastatic tumor line TUBO. In addition, TUBO-P2J was used to establish an intratumoral HER2 heterogenous animal tumor model to evaluate the therapeutic effects of anti-HER2/neu antibody.MethodsAfter establishing the cell line, TUBO-P2J was characterized regarding its susceptibility to anti-neu antibody and chemotherapeutics, as well as its metastatic potential in vitro and in vivo. In addition, expression profiles of metastasis related genes were also evaluated. A clinically relevant intratumoral HER2 heterogenous tumor model was established by inoculating mice with tumor cells consisting of TUBO and TUBO-P2J at a ratio of 1,000:1 or 10,000:1. Tumor growth and mouse survival were used to evaluate the therapeutic effects of anti-neu antibody.ResultsThe TUBO-P2J cell line is a HER2/neu negative and highly metastatic variant of TUBO. This cell line was resistant to anti-neu antibody therapy, and when inoculated subcutaneously, metastasized to the lungs within 14 days. Compared to the parental TUBO cell line, TUBO-P2J displayed an epithelial-mesenchymal transition (EMT) related gene expression profile including: the loss of E-cadherin, and increased Vimentin, Snail, and Twist1 expression. In addition, TUBO-P2J exhibited increased invasion and migration activity, and was resistant to chemotherapy drugs. Finally, mixed tumor implantations experiments revealed that an increased percentage of TUBO-P2J rendered tumors less responsive to anti-neu antibody therapy.ConclusionThis study describes a novel model of intratumoral heterogenous metastatic breast cancer in immune competent mice that can be used to develop novel or combined immunotherapies to overcome antibody resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-647) contains supplementary material, which is available to authorized users.
Highlights
Along with de novo resistance, continued exposure to trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2/neu) antibody, can lead to acquired resistance
TUBO-P2J cell line is a HER2/neu loss variant resistant to anti-neu antibody and chemotherateutics Spontaneous metastases have not been reported in previous studies using subcutaneous implantation of TUBO
TUBO-P2J cells only expressed H-2Kd and not H-2Kq (Figure 1B). These data suggest that TUBO-P2J is a metastatic version of the TUBO cell line
Summary
Along with de novo resistance, continued exposure to trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2/neu) antibody, can lead to acquired resistance. We characterize a new anti-HER2/neu antibody resistant and metastatic mouse breast carcinoma cell line, TUBO-P2J. This cell line was developed during in vivo experiments using the antibody sensitive and non-metastatic tumor line TUBO. TUBO-P2J was used to establish an intratumoral HER2 heterogenous animal tumor model to evaluate the therapeutic effects of anti-HER2/neu antibody. Trastuzumab (herceptin) is a humanized, recombinant monoclonal antibody that binds to the extracellular, juxtamembrane domain of HER2, and is standard care for patients whose breast cancer cells show strong immunohistochemical staining for HER2 or moderate immunohistochemical staining with HER2/neu gene amplification [2]. Even though reports for intratumoral HER2 heterogeneity are increasing, there are no valuable preclinical animal models to test whether trastuzumab or HER2 targeted treatments are effective or to develop new treatment strategies
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