Abstract Background: Esophageal Adenocarcinoma (EAC) continues to rise in incidence, with prognosis remaining poor despite advances in multimodality therapy. Several novel target agents are now being explored as an option for treating EAC. One potential target is heat shock protein 90 (Hsp90), a chaperone protein that is involved in many diverse biological processes including cell signaling, proliferation, and survival. Many of the client proteins are known oncoproteins that allow Hsp90 to stabilize cancer cell growth by supporting proliferation and preventing apoptosis. The isoform, Hsp90β, is constituently expressed, while Hsp90α is inducible during times of stress, with expression increased 2-10 fold in cancers. Our hypothesis is that Hsp90 inhibition, in combination with standard chemotherapeutic drugs, will cause EAC cancer cells to be more susceptible to apoptosis and reduce the rate of proliferation. Methods: EAC cell lines, OE19 and OE33, were used to evaluate the effects of Hsp90 inhibitor, AUY-922, in cancer cell growth and apoptosis. ELISA of WST-1 and BrdU were used to determine the effective dosage and assess proliferation. Pathway inhibition was evaluated by Western Blot of Hsp90α and Hsp70. OE19, OE33, and patient samples of EAC tumor and gastroesophageal reflux tissue were used to assess the gene expression of Hsp90 and several client protein pathways by reverse transcription polymerase chain reaction (RT-PCR). Results: The ED50 of AUY-922 was determined to be 30ηM. A combination of chemotherapeutic drugs, cisplatin and 5-fluorouracil (5-Fu), along with AUY-922 showed significantly decreased proliferation compared to untreated and single agent treated cell lines. Western blot demonstrated that Hsp90 was inhibited by AUY-922 treatment, by a decrease in expression of Hsp90α, and an increase in the expression of Hsp70. RT-PCR in the cell line treatment groups showed an impact on many client oncoproteins involved in cancer cell survival and Hsp90 was shown to be upregulated in tumor samples when compared to normal GERD samples. Conclusion: The use of Hsp90 inhibitor, AUY-922, leads to reduced Hsp90 pathway expression, resulting in a degradation of many Hsp90 client proteins involved in cancer genesis. Cell proliferation was decreased with AUY-922 treatment, with the greatest demonstrated effect when used in combination with cisplatin and 5-Fu. Therefore, Hsp90 inhibition may have an application in multimodal EAC chemotherapy. Citation Format: Christina L. Rotoloni, Jaclyn M. LaRosa, Michael J. Porter, Lori A. Kelly, Katherine Nega, Emily Wolfson, Yoshihiro Komastu, Juliann E. Kosovec, Pashtoon M. Kasi, Toshitaka Hoppo, Ali H. Zaidi, Blair A. Jobe. Enhanced efficacy of cisplatin and 5-fluorouracil combination with AUY-922 in esophageal adenocarcinoma cells. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr A48.