135 levels of HMGB1 in tissue samples were measured by quantitative RT-PCR. The protein levels of HMGB1 were measured using the HMGB1 enzyme- linked immunosorbent assay kit in plasma samples, and using immunohisto- chemical staining or western blotting in tissue samples or cell lines. The func- tions of HMGB1 on the ESCC cell lines were investigated by proliferation, invasion, or migration assays. Results: The mRNA and protein expression of HMGB1 in ESCC tissue was signifcantly higher than that in paired non-cancerous esophageal mucosa tissue. Plasma HMGB1 level was slightly higher, but not signifcant, in ESCC patients than in healthy volunteers. However, it was signifcantly higher in ESCC patients with Neoadjuvant chemotherapy (NAC) than in those without NAC. The mRNA and protein expression of HMGB1 were higher in ESCC cell lines than in WI-38 or HUVEC. In ESCC cells with high HMGB1 expression, knockdown of HMGB1 using specifc siRNAs inhibited the cell proliferation, migration and invasion. Conclusion: These fndings suggest that HMGB1 plays a crucial role in tumor malignant potential through its overexpression in esophageal squamous cell carcinoma. Disclosure: All authors have declared no conficts of interest. Keyword: HMGB1 PS02.052: AUTO-ANTIBODIES AGAINST TUMOR ANIGENS ARE USEFUL BIOMARKERS IN PATIENTS WITHESOPHAGEAL SQUA- MOUS CELL CARCINOMA Hideaki Shimada 1 , Satoshi Yajima 2 , Yoko Oshima 2 , Masaaki Ito 2 , Tatsuki Nanami 2 , Takashi Suzuki 2 , Kimihiko Funahashi 2 , Seiko Otsuka 2 , Isamu Hoshino 3 , Yoshihiro Nabeya 3 1 Toho University, Tokyo/JAPAN, 2 Toho university, Tokyo/JAPAN, 3 Chiba Cancer Center, Chiba/JAPAN Background: Serum antibodies are induced even ata the eraly phase of car- cinogenesis. Serum p53 antibodies (s-p53-Abs) have been developed and approved as routine blood test for monitoring esophageal squamous cell car- cinoma (SCC). Recently, we have developed new ELISA systems to detect serum anti-IgG auto-antibodies against tumor antigens in patients with esophageal (SCC). In this paper, we focused on serum auto-antibodies against p53, NY-ESO-1, Galectin-1 and RalA. Methods: Serum samples of patients with esophageal SCC were obtained before surgery. Serum anti-IgG antibodies against several tumor antigens were analyzed by newly developed ELISA systems. Target tumor antigens were p53, NY-ESO-1, Galectin-1 and RalA. Cut-off values were fxed using mean + 3SD of values of a total of 74 healthy controls. Changing pattern of serum p53 antibodies titers was also assessed during postoperative follow-up. Results: Positive rates of serum antibodies were 18% for p53, 31% for NY- ESO-1, 10% for Galectin-1 and 9% for RalA. Positive rates of these antibodies in healthy controls were 0%. Combination assay improved positive rates without increased false positive rates as follows; p53 + NY-ESO-1 = 40%, p53 + NY-ESO-1 + Galectin-1 = 47%, p53 + NY-ESO-1 + Galectin- 1 + RalA = 51%. Although some patients with extremely-high antibody titer for p53 persistently positive even after curative surgery, changing patterns of serum titers seemed to be associated with clinical outcome. Conclusion: Although antibody titer of s-p53-Abs seemed to be associ- ated with tumor burden, the titer gradually decresed at the last several months of the terminal stage. Such independent changing pattern of serum autoantibodies may have adding information to conventinal serum markers. We have developed new ELISA system to detect serum autoantibodies for patients with esophageal SCC. Although the positive rates of single serum auto-antibody were still relatively low, combination assay with plural auto- antibodies may be useful. Disclosure: All authors have declared no conficts of interest. Keywords: NY-ESO-1, auto-antibody, serum p53 antibody, Esophageal squa- mous cell carcinoma PS02.053: DUAL-STRANDS OF MIR-150-DUPLEX (MIR-150–5P AND MIR-150–3P) ACTED AS ANTI-TUMOR MIRNAS THROUGH TAR- GETING SPOCK1 IN ESOPHAGEAL SQUAMOUS CELL CARCI- NOMA Yusaku Osako 1 , Naohiko Seki 2 , Tetsuya Idichi 1 , Yoshiaki Kita 1 , Itaru Omoto 1 , Ken Sasaki 1 , Yasuto Uchikado 1 , Shoji Natsugoe 1 1 Kagoshima University, Kagoshima/JAPAN, 2 Chiba University, Chiba/JAPAN Background: MicroRNAs (miRNAs) belong to a group of small non-coding RNA molecules that act as pivotal agents responsible for fne-tuning RNA expression in a sequence-dependent manner. A large number of studies showed that dysregulated miRNAs are deeply involved in the development of cancer cells, as well as their metastasis and drug resistance. Based on our orig- inal miRNA expression signatures by RNA-sequencing revealed that both strands of miR-150–5p (the guide strand) and miR-150–3p (the passenger strand) was downregulated in several cancers. The general concept of miRNA biogenesis posits that the passenger strand of miRNA (the minor strand or miRNA*) derived from duplex miRNA is degraded and does not regulate gene expression. Here, we aimed that to investigate functional signifcance of these miRNAs in esophageal squamous cell carcinoma (ESCC). Methods: Cancer cell proliferation, migration and invasion abilities were per- formed by using mature miRNAs or siRNAs. Genome-wide gene expression analyses and in silico analyses were applied to identify miRNA target genes in ESCC cells. Results: Expression levels of miR-150–5p and miR-150–3p were signifcantly reduced in ESCC clinical specimens and cell lines. Cancer cell aggressiveness was inhibited by ectopic expression of these miRNAs. A total of 12 genes were identifed as oncogenic targets by both miR-150–5p and miR-150–3p in ESCC cells. SPOCK1 (SPARC/osteonectin, cwcv and kazal-like domains proteoglycan 1) was directly regulated by both miR-150–5p and miR-150– 3p by luciferase reporter assay. Overexpression of SPOCK1 was detected in ESCC specimens and knockdown of SPOCK1 by siRNA signifcantly inhib- ited cancer cell migration and invasion abilities. Conclusion: Both strands of miR-150-duplex (miR-150–5p and miR-150– 3p) acted as anti-tumor miRNAs in ESCC. Overexpression of SPOCK1 was enhanced cancer cell aggressiveness. Involvement of passenger strand of miRNA in cancer pathogenesis is novel concept in cancer research. We sug- gest that identifcation of novel function of passenger strands of miRNAs and the RNA networks they regulate might enhance our understanding of the molecular pathogenesis of ESCC. Disclosure: All authors have declared no conficts of interest. Keywords: Esophageal squamous cell carcinoma, microRNA PS02.054: EXPRESSION OF THE DESMOSOME-RELATED MOLECULE PERIPLAKIN IS ASSOCIATED WITH ADVANCED STAGE AND POOR PROGNOSIS OF ESOPHAGEAL SQUAMOUS CELL CARCINOMA Kazuhiko Yamada 1 , Teruki Hagiwara 2 , Takuhito Sezaki 2 , Toru Igari 1 , Chizu Yokoi 1 , Kyoko Nohara 3 , Masahiro Terayama 3 , Atsuko Kataoka 3 , Satoshi Yamashita 3 , Taeko Dohi 2 , Yuki I. Kawamura 2 , Norihiro Kokudo 3 1 National Center fo Global Health and Medicine, Tokyo/JAPAN, 2 Research Center for Hepatitis and Immunology, Research Institute, National Center fo Global Health and Medicine, Tokyo/JAPAN, 3 National Center for Global Health and Medicine, Shinjukuku, Tokyo/JAPAN Background: Our previous report showed that periplakin (PPL), a member of the plakin family of proteins, was expressed in all the normal esophageal squamous cells, except the Ki67 + basal cell layer; however, PPL-negative cells were observed in esophageal squamous cell carcinoma (ESCC) tissue samples and the proportion of PPL-positive areas in tumors showed considerable vari- ation. In this study, we analyzed the relationships between PPL expression in tumors and the clinicopathological features of ESCC. Methods: PPL expression was evaluated by immunostaining ESCC samples from 70 patients who underwent surgery and we classi ed the samples into PPL-negative and PPL-positive groups based on the proportion of PPL- positive areas in tumors, and the relationships among PPL expression, clinical features, and the ESCC prognosis were analyzed. ESCC cell line KYSE270 cells were stably transfected with the PPL expression vector and their growth was assessed by colony formation assay and subcutaneous xenografts in athymic mice. Results: As found in our previous study, decreased PPL staining intensity was observed in all of the cancer tissues analyzed, compared with that observed in paired normal esophageal mucosae; however, the PPL-positive group (the percentage of PPL-positive tumor cells was > 20% on immunostaining) exhibited positive associations with the pT classi cation (larger primary tumor) (P = 0.029), pN classi cation (lymph node metastasis) (P = 0.0462), and advanced stages of cancer (P = 0.0253). High PPL expression was observed in all of 26 lymph node metastases analyzed. Furthermore, patients with PPL-positive tumors showed poor postoperative prognosis compared to those with PPL-negative ones. Forced expression of PPL in the KYSE270 ESCC cell line induced a strati ed structure and colony formation. In addi- tion, PPL-transfected cells formed larger tumors in nude mice than mock- transfected cells, suggesting that relatively high PPL expression in tumors may facilitate cell-cell adhesion by desmosome formation and eventual cell growth in vivo. Downloaded from https://academic.oup.com/dote/article/31/Supplement_1/135/5097291 by guest on 03 June 2021