Immortalized cell lines can be used for diverse in vitro experiments, providing invaluable data before conducting in vivo studies Callithrix jacchus , the common marmoset, is a non-human primate model utilized for studying various human diseases. However, only a few immortalized marmoset cell lines are currently available. In the present study, we reveal that CRISPR-Cas9-mediated targeting of the p53 gene or CDKN2A locus is an effective means for immortalizing primary marmoset skin fibroblasts. In addition to frameshift mutations that result in premature stop codons, in-frame mutations potentially destroying the DNA-binding motif of p53 are frequently detected in immortalized cells. Like Cdkn2a -deficient mouse cells, CDKN2A -deficient marmoset cells express wild-type p53 proteins normally respond to genotoxic stresses, including adriamycin and etoposide. Taken together, these findings indicate that Cas9- mediated gene targeting of the p53 gene or CDKN2A locus is an effective tool for establishing immortalized marmoset cell lines with defined genetic alterations.

ErbB3, a heterodimeric partner of EGFR or ErbB2, plays important roles in the survival and growth of cancer cells through activation of PI3K/AKT pathway. ErbB3 can be activated by NRG1 expressed either by cancer cells or adjacent mesenchymal cells, or NRG1-fusion proteins produced by genetic alterations in cancer cells. Oncogenic driver mutations in ErbB3 also induce its activation. Previously, we have demonstrated preclinical anti-cancer efficacy of a monoclonal anti-ErbB3 antibody, ISU104 as a monotherapy or in combination with anti-EGFR antibody in various preclinical models. Biomarker analysis of the models demonstrated that there is a significant positive correlation between tumor growth inhibition by ISU104 and NRG1 mRNA/pERBB3 protein expression levels. Based on this analysis, anti-cancer efficacy of ISU104 was further explored in cancer cells and cell line- or patient-derived xenograft cancer models with high NRG1 expression, NRG1-fusion or oncogenic ErbB3 mutations. ISU104 potently inhibited phosphorylation of ERBB3 and AKT, cell proliferation and tumor growth of such models. Potential impacts of other genetic alterations on the anti-cancer efficacy of ISU104 were also investigated. Overall, the presented data suggest that ISU104, an anti-ErbB3 agent in the early stage of clinical development, can be applied for the treatment of the solid tumors expressing high level of NRG1 or harboring genetic alterations such as NRG1-fusion or oncogenic ErbB3 mutations. Citation Format: Seung-Beom Hong, Mirim Hong, Tae-Eun Kim, Ju Yeon Kim, Jung Won Kim, Jeongin Cho, Bongseok Shin, Donggoo Bae. Anti-cancer efficacy of an anti-ErbB3 antibody, ISU104, against the cancers with NRG1-overexpression, NRG1-fusion, or oncogenic ErbB3 mutations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3042.

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