Abstract LB006: Interactome analysis identifies signaling pathways activated by ETV6-NTRK3 oncogenic gene fusions

Abstract

Abstract Chromosomal translocations creating fusion genes are among the most common mutation class of known cancer genes, and they have long been identified as driver mutations in certain types of cancer. Recently, oncogenic fusion genes (oncofusions, OFs) have been found in many hematological and solid tumors, demonstrating that translocations are a common cause of malignancy. The frequency of recurrent gene fusions varies depending of the specific type of cancer, but currently identified translocations are estimated to drive up-to 20% of cancer morbidity. In many occasions the oncofusion is the sole driver of oncogenesis when present and certain oncofusion pairs are typically found in one or few specific cancers. ETV6-NTRK3 (EN) oncofusion, is a product of the chromosomal t(12; 15)(p13; q25) translocation, which fuses the N-terminal SAM (sterile alpha motif) domain of ETV6 to the C-terminal protein tyrosine kinase domain of NTRK3 (also known as TrkC). EN is expressed from the ETV6 promoter in the fused chromosome 15. The ETV6 promoter is generally more active, than NTRK3 promoter, and causes EN fusions to be expressed more highly in several tissues and especially in bone marrow and salivary glands. ETV6 forms fusions with many kinases, which are found in hematological malignancies and solid tumors. Except for ETV6-NTRK3, other ETV6-kinase fusions are reported in either hematological or solid malignancies and ETV6-NTRK3 further distinguishes itself by being also reported in several subtypes in both cases. Four EN variants with alternating break points have since been detected in a wide range of human cancers. To provide insight into EN oncogenesis, we employed a proximity labeling mass spectrometry approach to define the molecular context of the EN fusions. We identify 237 high-confidence interactors, which link EN fusions to several key signaling pathways, including ERBB, Insulin and JAK/STAT. We then assess the effects of EN variants on these pathways, and show that the pan NTRK inhibitor selitrectinib (LOXO-195) inhibits the oncogenic activity of EN2, the most common variant. This systems-level analysis of defines the molecular framework in which EN oncofusions operate to promote cancer. Citation Format: Matias Kinnunen, Xiaonan Liu, Kari Salokas, Salla Keskitalo, Markku Varjosalo. Interactome analysis identifies signaling pathways activated by ETV6-NTRK3 oncogenic gene fusions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB006.