Abstract B03: Identification of R-spondin fusions in NSCLC.

Abstract

Abstract Autocrine Wnt signaling has been reported in a significant fraction of NSCLC. The R-spondin (RSPO) protein family is a small family of four secreted growth factors. The four paralogs share 40–60% pairwise amino acid sequence identity and are predicted to share substantial structural homologies. RSPO proteins are involved in vertebrate development and their ligand-type activities overlap substantially with those of canonical Wnt ligands. A characteristic feature of all four RSPO members is their ability to activate β-catenin signaling and enhance WNT-mediated β-catenin activation. It has recently been described that recurrent gene fusions involving RSPO family members of RSPO2 and RSPO3 that occur in ~10% of colon tumors and are mutually exclusive with other WNT pathway genetic alterations. In this study we developed a TaqMan qRT-PCR-based approach to evaluate systematically the expression of these three (3) RSPO fusion transcripts in formalin-fixed paraffin embedded tissue (FFPET) samples. We examined 324 NSCLC samples that included 197 squamous and 127 adenocarcinoma subtypes for the presence of EIF3E(e1)-RSPO2(e1), PTPRK(e1)-RSPO3(e2), PTPRK(e7)-RSPO3(e2). EIF3E(e1)-RSPO2(e1) was identified in 1% and this fusion transcript is expected to produce a functional RSPO2 protein driven by the EIF3E promoter. The PTPRK(e1)–RSPO3(e2) transcript found in 2% and is an in-frame fusion that preserves the entire coding sequence of RSPO3 and replaces its secretion signal sequence with that of PTPRK. Interestingly, all the fusions were detected only in the squamous subtype of NSCLC. These findings suggest an important role for dysregulated Wnt-β-catenin signaling in lung cancer and identify a new driver segment in NSCLC for therapeutic intervention. Citation Format: Jayaprakash Karkera, Gabriela Martinez, Katherine Bell, Joseph Portale, Dana Gaffney, Matthew V. Lorenzi, Suso Platero. Identification of R-spondin fusions in NSCLC. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr B03.