World first hybrid neuroendocrine cell line sharing properties of NET G3 and dedifferentiated NEC.

Current therapies for neuroendocrine neoplasms (NENs) are limited, especially for fast-growing dedifferentiated NECs, which exhibit low somatostatin receptor (SSTR) expression and poor prognosis. Well-differentiated neuroendocrine tumors (NETs), on the other hand, retain SSTR expression, making them amenable to receptor-targeted therapies. In dedifferentiated NEC, C-X-C motif chemokine receptor 4 (CXCR4) has been shown to be abundantly expressed, making it a potential target for alternative treatment and diagnostic strategies. A major challenge in developing targeted therapies is the lack of primary patient-derived cell lines that maintain receptor profiles suitable for preclinical evaluation of established or innovative receptor-targeted approaches. We established the MS-18 cell line from a metastatic rectal NEC. Neuroendocrine differentiation markers, SSTRs1-5, CXCR4, epithelial and mesenchymal markers, drug transporters (ABCB1, ABCG2), and Ki-67 were analyzed using qPCR and immunoblotting. Somatostatin receptor and CXCR4 function was evaluated by radiouptake assays. Electron microscopy, karyotyping, and CGH were performed, and the cell's in vivo engraftment rate was evaluated in a mouse NSG model. Viability studies on conventional therapeutic agents were performed. Extended molecular profiling of the primary tumor, liver metastasis, and MS-18 cell line was conducted. MS-18 cells showed strong expression of neuroendocrine markers (synaptophysin, neuron-specific enolase) and preserved epithelial differentiation (high E-cadherin, absence of mesenchymal markers). SSTR1, SSTR2, and SSTR5 were highly expressed, while SSTR3 and SSTR4 were absent. Uniquely, MS-18 cells exhibited strong CXCR4 expression. The proliferation index (Ki-67: 90%) matched that of the primary tumor. Elevated ABCG2 expression contributed to resistance to etoposide. Molecular profiling revealed no pathogenic mutations in key genes commonly altered in NENs, including MEN1, DAXX, ATRX, mTOR, PTEN, TP53, and RB1. The successful in vivo engraftment rate was high (4/5). The MS-18 cell line is the first patient-derived cell line with a transitional phenotype between differentiated NET and dedifferentiated NEC, showing strong expression of SSTR2 and CXCR4 and absence of driver mutations in key NET-/NEC-associated genes. It offers a unique platform for preclinical evaluation of targeted therapies.