Driscoll, Olivia

Abstract Introduction: The incidence of esophageal adenocarcinoma (EAC) has increased more than any other cancer in our lifetime. Barrett’s esophagus (BE) is the only known precursor to EAC. At present, HER-2 and anti-PD-L1 therapies are FDA-approved for EAC, and off-label use of EGFR-directed therapy has been reported. Our study aims to use liquid chromatography mass spectrometry (LC/MS) to measure the expression of oncoproteins that are currently approved-drug targets in EAC and explore new promising targets for drug development and diagnostic applications for EAC and BE. Methods: EAC patients who underwent esophagectomy without chemo-radiation were identified. BE patients with subsequent progression to EAC and those without progression for >10 years were identified. Normal esophageal mucosa tissues with no history of progression were analyzed for baseline expression. Tissue sections were microdissected to isolate pure EAC, BE and normal mucosal cells from stroma. These biopsies were solubilized for LC/MS-based quantification of 80+ clinically relevant tumor markers including novel markers which are believed to play a role in the disease progression from BE to EAC. The expression trends of these markers were scrutinized by immunofluorescence (IF) in a subset of specimens/biomarkers to confirm mass spec results. Results: A total of 159 tissues were analyzed via LC-MS. In 55 EAC tissues - HER2, PD-L1 and EGFR were overexpressed in 16.3%, 0%, and 0% of patients, respectively. New markers DAD1 and S100P were noted to have high (7,634.0 and 27,222.6 attomoles/ug) and consistent (98.1% and 94.5%) overexpression in EAC samples. Expression of HER2, S100P and DAD1 were significantly higher in EAC compared to 23 normal esophageal mucosa specimens. There was no statistical difference in the expression of PD-L1 and EGFR between EAC and healthy mucosal samples. 45 BE biopsies progressed to EAC within a mean of 380 days, while the remaining 36 BE specimens did not progress over a 10-year period. 8 novel biomarkers were expressed at a higher level in BE tissue that progressed to cancer when compared to esophageal tissue that remained stable over 10 years. The expression trends observed via LC/MS were confirmed via IF in DAD1, S100P and two other novel markers. Discussion: LC-MS revealed low prevalence of target proteins in currently approved EAC therapies and high levels of newly discovered disease drivers that should be explored as possible therapy targets or diagnostic markers. The differential overexpression of the novel markers in progressive and non-progressive BE tissues, as well as the consistent overexpression of these markers in EAC tumors, demonstrates the potential for early detection of esophageal carcinogenesis and/or reveals potential therapeutic programs for an indication that lacks highly efficacious targeted therapy options. Citation Format: Christopher Hartley, Ajay Bansal, Catherine Hagen, Olivia Driscoll, Seyun Oh, Joe Abdo, Sumeet K. Mittal. Mass spectrometry detects lower frequency of routine markers and consistent overexpression of novel disease drivers in Barrett's-related esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2805.

343 Background: Esophageal adenocarcinoma (EAC) continues to have extremely poor prognosis despite advances in surgical and oncological regimens. Targeted and immune therapy hold promise to improve outcomes in solid tumors including EAC. At present HER-2 and anti-PD-L1 therapies are approved by the FDA for EAC. Additionally, off-label use of EGFR directed therapy has been reported. The aim of this study is to measure expression of 80+ oncoproteins in EAC using multiplexed mass spectrometry to elucidate expression of currently approved-drug targets and explore promising new targets for drug development. Methods: After Institutional Review Board approval (Mayo Clinic and KUMC), EAC patients whose tumors were resected via esophagectomy before chemotherapy and/or radiation were identified. Normal esophageal mucosa samples with no history of EAC were also retrieved for analysis. Tissue sections were microdissected to exclude stroma from adenocarcinoma cells. Isolated EAC cells were solubilized for mass spectrometry-based quantitation of more than 80 clinically relevant tumor markers. Results: 55 EAC tissues were analyzed. HER2, PD-L1 and EGFR were overexpressed only in 16.3%, 0%, and 0% of patients, respectively. New oncoproteins #2 and #6 were noted to have high (7,634.0 and 27,222.6 attomoles/ug) and consistent (98.1% and 94.5%) overexpression in EAC samples. Expression of HER2, oncoproteins #2 and #6 were significantly higher in EAC compared to normal esophageal mucosa. There was no statistical difference in the expression of PD-L1 and EGFR between EAC and normal samples. Conclusions: Mass spectrometry revealed a very low prevalence of target oncoproteins in EAC for currently used drugs. Our study potentially reveals alternate markers which are near universally present at high levels and should be further explored for targeted treatment.[Table: see text]