Proteomic analysis to identify markers for response to treatment in esophageal cancer.

Abstract

61 Background: Neoadjuvant chemoradiotherapy (NCRT) followed by surgery represents a key therapeutic strategy for locally advanced esophageal cancer (LAEC). Former studies addressed the clinicopathological patterns of patients who demonstrated good response to NCRT compared with inferior response. Nevertheless, there is paucity of data regarding potentially involved cellular pathways that account for tumor response to NCRT. We performed a comprehensive proteomic analysis to identify the key differences in protein function and pathway activation between patients with a poor response and those with a favourable response to treatment. Methods: Patients diagnosed with LAEC who were treated with NCRT and operated at our institution were included in the study. Patients were defined as good responders (GR) upon the tumor regression grade (TRG) in the pathological specimen: GR defined as TRG 0/1 and no evidence of recurrence at 1-year post surgery. Bad responders (BR) were defined as TRG 2/3 and recurrence < 1year. Tumor was isolated from the surgical specimen and proteins were extracted and processed for mass spectrometry-based analysis. Clinical data of demographics, response to treatment, and survival was retrieved from electronic medical records. Difference in protein expression between GR and BR were analysed using validated gene expression pathways tools and correlated to clinical data. Results: Forty-four patients were included in the cohort. Mean age was 66.7 years, male predominance (33/44). Thirty-five patients had adenocarcinoma – 17 GR and 18 BR. Nine patients had squamous cell carcinoma – 6 GR and 3 BR. Protein expression patterns significantly differed between GR and BR regardless of histology, mainly in cellular pathways account for nucleic acid metabolism (p < 10-9), whereas BR had overexpression of these genes. Conclusions: Our study indicate that lack of response to NCRT may derive from overexpression of unique cellular pathways. Former studies imply these cellular pathways may play a role in resistance to cisplatin. Larger transcriptomic studies are warranted for future analysis to extend these observations.