Purpose:In order to identify pretherapeutic predictive biomarkers in tumor biopsies of patients with locally advanced esophageal adenocarcinomas treated with neoadjuvant chemotherapy (CTX) we used an explorative proteomic approach to correlate pretherapeutic protein expression profiles with tumor response to neodadjuvant CTX.Experimental design:34 patients with locally advanced esophageal adenocarcinomas who received neoadjuvant platin/5FU-based CTX before surgical resection were enrolled in this study. Response to CTX was determined (a) by the amount of decline of [F-18]-Fluorodeoxyglucose tumor uptake 2 weeks after the start of CTX measured by PETand (b) by histopathological evaluation of tumor regression after surgical resection. Explorative quantitative and qualitative protein expression analysis was performed using a quantitative differential protein expression analysis employing dual isotope radioactive labeling of protein extracts. Selected identified biomarkers were validated by immunohistochemistry and quantitative real time RT-PCR.Results:Proteomic analysis revealed 4 cellular stress response associated proteins (HSP27, HSP60, GRP94, GRP78), and a number of cytoskeletal proteins, whose pretherapeutic abundance was significantly different (p<0.001) between responders and nonresponders. Immunohistochemistry and gene expression analysis confirmed these data demonstrating a significant association between low HSP27 expression and nonresponse to neoadjuvant CTX (p=0.049 and p=0.032 respectively).Conclusions:Albeit preliminary, our encouraging data suggest that protein expression profiling may distinguish cancers with different response to CTX. Our results suggest that response to CTX may be related to different activation of stress response and inflammatory biology in general. Moreover, the potential of heat shock proteins and glucose regulated proteins as biomarkers of CTX response warrants further validation.