Germline alteration analysis reveals EPHB4R91H mutation as a key player in multiple primary lung tumors.

Multiple primary lung tumors are garnering attention from clinicians, with adenocarcinoma emerging as the predominant histological type. Because of the heterogeneity and diffuse distribution of lesions in the same patient, the treatment of multiple primary lung adenocarcinoma (MPLA) is a significant challenge. As a kind of variation unaffected by tumor heterogeneity, germline alterations may play a key role in the development of MPLA. Here, whole-exome sequencing of peripheral blood was employed to obtain germline alteration data. Intergroup comparative analyses on rare and deleterious alterations of MPLA, solitary lung adenocarcinoma, and healthy individuals in an MPLA family were performed to clarify the candidate alterations. Whole-exome sequencing and targeted Sanger sequencing were performed in 27 disseminated MPLA patients to detect the mutation site that had been screened. A rare and deleterious germline alteration, EPHB4R91H, was found in all of the patients of an MPLA family and a patient with disseminated MPLA. It was revealed that EPHB4R91H was able to enhance the proliferation, migration, and invasion ability of A549 cells through increased binding affinity to ephrinB2, which in turn activated the EPHB4/ERK/JNK/MAPK pathway. Our findings corroborate that germline alterations are involved in the development of MPLA. And it was found for the first time that the EPHB4R91H mutation promotes the development of MPLA by enhancing its affinity for ephrinB2 and thereby active EPHB4/ERK/JNK/MAPK pathway.