Invasive Mucinous Adenocarcinoma (IMA) accounts for 2-5% of lung adenocarcinomas and it is associated with an unfavorable clinical course, mainly due to lack of effective treatments. Current knowledge of the molecular alterations involved in IMAs is limited. Recently, the NRG1 genomic rearrangement was identified as a subtype-specific molecular feature of Asiatic IMA cohorts since it acts as a strong inductor of the aberrant tyrosine kinase activity of ErbB2/ErbB3 heterodimers through PI3K–AKT and MAPK cellular cascades.

In light of these premises we explored the occurrence and frequency of NRG1 fusions in a cohort of 90 Formalin Fixed Paraffin Embedded (FFPE) lung adenocarcinoma from Caucasian patients (35 non-IMAs and 55 IMAs) by performing FISH analysis to study the NRG1 genomic region (β-III isoform, chr 8p12). In total, 16 out of 55 (29%) IMAs showed NRG1 rearrangements, whereas in non-mucinous lung adenocarcinoma group it was found with a frequency of 3% (1/35). The functional effect of the genomic rearrangement was confirmed by RT-PCR and sequencing in three cases with available RNA, where NRG1-CD74 fusion transcripts were identified. An aberrant expression of pErbB3 was also observed in these three NRG1 rearranged cases by performing immunohistochemistry analysis, thus confirming the ErbB3 cascade activation.

Our results strongly confirm NRG1 rearrangements as potentially treatable oncogenic driver alterations associated with a definite lung adenocarcinoma subtype in Caucasian population and support a clear molecular rationale to novel therapeutic opportunity for these aggressive tumors.

Note: This abstract was not presented at the meeting.

Citation Format: Domenico Trombetta, Giulio Rossi, Angelo Sparaneo, Federico P. Fabrizio, Maria C. Manzorra, Evaristo Maiello, Vito M. Fazio, Paolo Graziano, Lucia A. Muscarella. Frequent NRG1 genomic rearrangements in invasive mucinous adenocarcinoma from caucasian patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 494. doi:10.1158/1538-7445.AM2017-494