IGF2 and small cell lung carcinoma: Notably, LOI of IGF2 is an early initiating event in the development of ileal neuroendocrine tumors [55, 56], and our results show biallelic expression of IGF2 isoforms in cell lines from other neuroendocrine tumors (neuroblastoma and SCLC; Additional file 17: Table S9 G and J).