Abstract 3148: Implication of highly cytotoxic natural killer cells for esophageal cancer treatment
Authors: Lim Kee Siang , Kua Ley Fang , Mimura Kosaku , Shiraishi Kensuke , Chng Wee Joo , Yong Wei Peng , Campana Dario , Kono Koji 
Published: August 2015

Abstract
Natural killer cell-based immunotherapy is a potential treatment for esophageal cancer due to the cytotoxic effect of NK cell and minimal side effects. Natural Killer Activation and Expansion System (NKAES) is our unique system that capable to produce highly cytotoxic and highly proliferative NK cells. Previous studies showed that NKAES-generated NK cells exerted high cytotoxicity on various types of leukemic cell lines and soft tissue cancer cell lines. Our study focuses on the feasibility of NKAES-generated NK cell immunotherapy for esophageal cancer. To generate NKAES-generated NK, peripheral blood mononuclear cell (PBMC) is co-cultured with feeder cells (genetically modified K562 leukemic cell) in presence of interleukin 2. The feeder cells express 4-1BB ligands and membrane bound interleukin 15, which enhance NK responsiveness to interleukin 2, NK activation, NK proliferation and NK survival. Our NK cytotoxicity assay results indicate that seven esophageal cancer cell lines (TE1, TE2, TE3, TE4, TE5, KYSE110 and KYSE30) are highly sensitive to NKAES-generated NK cells. We further compared the cytotoxicity between resting NK, IL-2 activated NK, and NKAES-generated NK on these cell lines. We found that NKAES-generated NK produced the strongest cytotoxicity on these cancer cell lines. NK cytotoxicity is strongly depending on the expression of NK Group 2 Member D (NKG2D) ligands. During cancer metastasis, NKG2D ligands are shedded off by metalloproteinase, which contributes to immune evasion. Interestingly, a previous study showed that a colorectal cancer cell line was sensitive to NK cytotoxicity in early phase of EMT. We further investigated this phenomena in esophageal cancer. To study this, we successfully established an in vitro model, in which stimulated EMT event in esophageal cancer cell lines by using GSK3β inhibitor and epithelial growth factor (EGF). Astonishingly, beside EMT features, we observed that surface NKG2D ligand expression was higher in EMTed esophageal cancer cells compared with control. In addition, EMTed esophageal cancer cells were much sensitive to NKAES-generated NK cytotoxicity. The difference of NK sensitivity was insignificant in IL-2 activated NK. These findings suggest that early EMT event is a crucial checkpoint to prevent further progression that ultimately lead to cancer metastasis, and NK Immunosurveillance is important in this checkpoint. As a conclusion, NKAES-generated NK cells are capable to exert high cytotoxic effect on esophageal cancer cells as well as to establish a strong checkpoint to prevent the progression of EMT event.
Citation Format: Kee Siang Lim, Ley Fang Kua, Kosaku Mimura, Kensuke Shiraishi, Wee Joo Chng, Wei Peng Yong, Dario Campana, Koji Kono. Implication of highly cytotoxic natural killer cells for esophageal cancer treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3148. doi:10.1158/1538-7445.AM2015-3148