Abstract B12: Exploiting the zebrafish to study lymphocyte infiltration in MYCN-driven neuroblastoma

Abstract

Abstract Application of tumor immunotherapy has achieved an unprecedented success in patients with hematopoietic malignancies. However, it remains challenging to treat the majority of solid tumors with immunotherapy due to low lymphocyte infiltration, treatment resistance, and immunosuppressive tumor microenvironment. Improving the clinical efficacy of immunotherapy in solid tumors requires a deeper understanding of immune evasion. Neuroblastoma is the most common extracranial tumor in children and is responsible for ~15% of childhood cancer-related deaths. MYCN is a member of the MYC oncogene family, and its aberrant expression in neuroblastoma predicts aggressive disease and poor prognosis. This largely results from the low infiltration rates of cytotoxic lymphocytes in MYCN-amplified neuroblastoma. Elucidation of the mechanism by which MYCN suppresses antitumor response in the neuroblastoma microenvironment will provide useful information to guide immunotherapy. Here we generated a compound transgenic zebrafish, Tg(dβh:MYCN;dβh:EGFP;lck:EGFP;CD4:mCherry), in which lymphocytes and tumor cells are differentially fluorescently labeled. We first monitored the infiltration of mCherry-labeled CD4+ T cells in EGFP-positive MYCN-overexpressing premalignant neural crests at 7, 14, and 21 days post fertilization (dpf). We found that at day 14 and 21, MYCN-overexpressing premalignant neural crests can attract a significantly higher number of lymphocytes, compared to control neural crests without MYCN overexpression. Interestingly, we also found the increased number of infiltrated T cells was MYCN dose dependent by using low MYCN-expressing transgenic fish, Tg(dβh:MYCN;dβh:mCherry;lck:EGFP). To determine if T-cell development is impacted, we imaged the thymus of MYCN-overexpressing or control fish at day 7, 14, and 21 dpf. We found that fluorescent intensity of thymus is significantly higher in MYCN-overexpressing fish compared to control fish. Taken together, our study identified MYCN-overexpressing premalignant neural crests can not only affect T-cell development but also attract T cells to disease site. We will perform further experiments to understand how and why MYCN-overexpressing premalignant neural crests impact T-cell development and which population of T cells is attracted to disease site. Citation Format: Xiaodan Qin, Andrew Lam, Xike Zhang, Adam Hurlstone, Hui Feng. Exploiting the zebrafish to study lymphocyte infiltration in MYCN-driven neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B12.