Abstract P078: Cancer cell derived extracellular vesicles convey protein signatures of small cell lung carcinoma

Abstract Extracellular vesicles (EVs) are known effectors of cell signaling and exchange implicated in cancer development and progression, as well as remodeling and immunomodulation of the tumor microenvironment. EVs are detected in various biofluids and are considered to convey signature features of the cells from which they originate. Clinical assessment of plasma-derived EV molecular contents therefore offers promise of “liquid biopsies” for detection or subtyping of cancers as well as dynamic reporting of tumor status during and after treatment. To date, there have been no comprehensive analyses aimed at interrogating the diverse repertoire of EV protein cargoes in small cell lung carcinoma (SCLC). Using plasmas from a cohort of 18 SCLC cases, 16 lung adenocarcinoma (LUAD) cases and 34 controls matched based on smoking status, age, and sex, EVs were enriched via affinity capture using magnetic beads functionalized with phosphatidyl serine binding protein TIM4 in addition to single-step density flotation ultracentrifugation to deplete abundant protein background. In-depth proteomic profiling was performed on enriched EVs via nano liquid chromatography / high-resolution ion-mobility mass spectrometry. Profiles were intersected with proteomic profiles generated from intratumor EVs dissociated from 12 SCLC patient-derived xenograft (PDX) mouse models as well as EVs isolated from cell-conditioned medias of a panel of 17 SCLC cell lines. A total of 496 proteins were quantified in TIM4pos EVs. Unsupervised hierarchical clustering and principal component analyses showed that TIM4pos EV protein cargoes differentiate SCLC from LUAD and matched controls. Differential analyses identified 117 proteins that were elevated (AUC> 0.60) in TIM4pos SCLC EVs compared to controls. Of these 117 features, 101 (86%) were also elevated (AUC> 0.60) in TIM4pos SCLC EVs compared to TIM4pos LUAD EVs. Intersection of proteins elevated in TIM4pos SCLC EVs with proteomic profiles of intratumor EVs from SCLC PDX models and conditioned media-derived EVs from SCLC cell lines yielded 67 and 92 overlapping proteins, respectively. Overlapping proteins were characterized by YAP1-associated signatures of cytoskeletal re-arrangement and epithelial-to-mesenchymal transition and included a prevalence of neuronal tubulin and actin family members, YWHA family members, and annexins. We developed and applied an optimized EV isolation and proteomics workflow to profile EV protein cargoes and establish circulating EV-associated protein signatures of SCLC with biomarker potential. Our integrated analyses identified novel EV-associated proteins for detection of SCLC that are associated with oncogenic drivers. These studies demonstrate that EVs harbor cancer cell disseminated signatures and that continued efforts to query the EV proteome towards discovery of novel SCLC biomarkers are warranted. Citation Format: Jody Vykoukal, Taketo Kato, Hiroyuki Katayama, Allison Stewart, Ehsan Irajizad, Yining Cai, Fu-Chung Hsiao, Jennifer B. Dennison, Edwin J. Ostrin, Hai T. Tran, Carl M. Gay, Lauren A. Byers, Johannes F. Fahrmann, Samir M. Hanash. Cancer cell derived extracellular vesicles convey protein signatures of small cell lung carcinoma. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P078.