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Background: Immunotherapies targeting the PD-1/PD-L1 pathway have emerged as promising therapeutic strategies for many cancers. PD-L1 and PD-L2 are ligands of PD-1 on T-cells and prevent T-cells activation and proliferation. There have been reported that PD-L1 and PD-L2 are expressed on not only antigen-presenting cells but also some types of tumors. Clinical and prognostic features of the PD-L1 have been widely reported for many types of cancers but those of PD-L2 remain unclear in esophageal cancer. The aim of this study was to analyze the clinical significance and the difference between PD-L1 and PD-L2 in esophageal cancer. Methods: Using a database of 437 curatively resected esophageal cancer from April 2005 to March 2016, we evaluated PD-L1 and PD-L2 expression in tumor cells by immunohistochemical staining and analyzed the association between those with clinicopathological features. Double immunohistochemical staining for PD-L1 and PD-L2 was performed to confirm the localization of each positive cell. Results: Out of 437 cases of esophageal cancer, 69 cases (15.8%) showed PD-L1 positive and 71 cases (16.2%) showed PD-L2 positive expression. There was no significant relationship between PD-L1 and PD-L2 positive cases (p=0.18). In both PD-L1 and PD-L2 positive cases, double immunohistochemical staining for PD-L1 and PD-L2 showed that there was a heterogeneity for PD-L1 and PD-L2 positive tumor cell. PD-L1 positive cases were significantly associated with tobacco use (p=0.013), pathological stage (p=0.001), and preoperative therapy present cases (p=0.015). In the other hand, PD-L2 positive cases were significantly associated with younger age (p=0.029). Thus PD-L1 and PD-L2 patient characteristics were likely different. Overall survival rates of the patients with PD-L1 or PD-L2 positive were significantly worse than those with PD-L1 or PD-L2 negative (p=0.009 and p=0.013, respectively). Conclusion: There was no significant relationship between PD-L1 and PD-L2 expression, and patient characteristics of those were different in patients with esophageal cancer. But both PD-L1 and PD-L2 expression were significantly associated with prognosis, supporting their roles as prognostic biomarkers. Citation Format: Kazuo Okadome, Yoshifumi Baba, Taisuke Yagi, Yuki Kiyozumi, Kojiro Eto, Yukiharu Hiyoshi, Yohei Nagai, Takatsugu Ishimoto, Masaaki Iwatsuki, Shiro Iwagami, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. Clinical significance and the difference between programmed death-1 ligand-1 and ligand-2 in patients with esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4123.

[Background] Esophageal cancer is the sixth most common cause of death from cancer worldwide. Although the development of multidisciplinary treatment for esophageal cancer, the prognosis of those patients remains poor. Recently, immunotherapy is expected as innovative therapy for several types of cancer. Indoleamine 2, 3- Dioxygenase (IDO1) is an enzyme responsible for the oxidation of tryptophan into kynurenine and implicated in immune modulation through its ability to limit T cell function and engage mechanisms of immune tolerance. IDO1 is focused as one of the immune subversion strategy and the therapy of targeting IDO1 is in clinical development for many types of cancer. IDO1 activation induces the downregulation of activating natural killer (NK) cell receptors on NK cells and inhibition of cytotoxic T cells by promotion of cell cycle arrest and apoptosis. However, the significance of IDO1 expression in esophageal cancer remains still unknown. The aim of this study is to examine the relationship between IDO1 expression and tumoral immune status, and its prognostic impact in esophageal cancer. [Methods] IDO1 expression, cluster of differentiation (CD8) expression as a marker of cytotoxic T cells, forkhead Box P3 (FOXP3) as a maker of regulatory T cells were evaluated by immunostaining in 305 clinical samples of curative resected esophageal cancer. [Result] In 305 clinical samples, high IDO1 high expression (n=71) was significantly associated with poor prognosis in overall survival(OS)(p=0.0034). In uni-and multivariate analysis, IDO1 high expression was an independent prognostic factor for OS. In those patients, CD8 low expression was also associated with poor prognosis in OS (p = 0.025). Furthermore, double immunostaning with IDO1 and CD8 revealed that CD8 expression levels was inverse correlated with IDO1 expression levels in those patients. In combination analysis of IDO1 and CD8 expression, IDO1 high expression and CD8 low expression group experienced worse overall survival (p=0.0024). Conversely, IDO1 low expression and CD8 high expression group was shown the best overall survival. In addition, IDO1 high expression group is correlate with the high counts of FOXP3 positive cells (p = 0.02). [Conclusion] IDO1 expression was associated with an unfavorable clinical outcomes by induced immune tolerance and the classification of IDO1 and CD8 expression levels might serve as a predictive biomarker in esophageal cancer. The correlation between IDO1 and FOXP3 expression suggested that IDO1 involved in immune tolerance in esophageal cancer. These findings indicate that IDO1 would be a regulator of, and candidate therapeutic target in esophageal cancer. Citation Format: Yuki Kiyozumi. IDO1 high expression is associated with a poor prognosis in patients with esophageal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5700.

Introduction: It has become clear that macrophages are important cells forming cancer microenvironment and tumor-associated macrophages (TAM) promote their proliferation in various cancer types. In particularly, M2-type macrophages have been reported to promote the production of anti-inflammatory factors and the infiltration of regulatory T cells and suppress anti-tumor immunity, and new antitumor therapies that control tumor growth by controlling TAM have been proposed. In addition, "anti-PD-1 antibody" has attracted attention also in esophageal cancer, but the relationship between TAM and PD-L1 expression has not been clarified. Methods: A retrospective study was performed on 301 patients who underwent esophagectomy for esophageal cancer between March 2005 and June 2013. We performed immunohistochemistry and evaluation of macrophage markers (CD163 and CD204) and PD-L1. In addition, we performed in vitro experiments to clarify the cellular malignancy and relationship with PD-L1 expression. Results: Out of 301 cases of esophageal cancer, 156 cases showed CD163 high expression (51.8%) while 146 cases showed CD204 high expression (48.5%). We divided into three groups of TAM status based on CD204 and CD163 expression (CD163 and CD204 both positive: TAM status high (n=100), either one positive: moderate (n=102), both negative: low (n=99)). In TAM high group, there were more advanced cancers and adenocarcinoma cases (P Conclusion: This study suggested that TAM correlated with poor prognosis in patients with esophageal cancer. In addition, TAM correlated with invasive capacity and migratory capacity. Importantly, TAM correlated PD-L1 expression in esophageal cancer cell lines. Citation Format: Taisuke Yagi, Yoshifumi Baba, Yuki Koga, Tomoyuki Uchihara, Yuki Kiyozumi, Hiroshi Sawayama, Yukiharu Hiyoshi, Masaaki Iwatsuki, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. Role of tumor-associated macrophages in esophageal cancer: PD-L1 expression and prognosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4742.

Background: Tumor microenvironment consists of various types of cells. Although cancer associated fibroblasts (CAFs) have been reported to enhance tumor progression and anticancer drug resistance through secretion of soluble factors so far, the crucial mechanism is not fully understood. On the other hand, advanced gastric cancer (GC) is still poor prognosis due to metastasis and recurrence despite the progression of diagnosis and treatment. The aim of this study is to identify the molecular mechanism underlying anticancer drug resistance mediated by CAFs in GC. Methods: We have isolated CAFs from surgically resected GC tissues and collected conditioned medium (CM) of CAFs. Human GC cell lines with or without CAF-CM were examined the drug sensitivity and analyzed expression of specific genes using quantitative reverse transcription PCR. We isolated extracellular vesicles (EVs) from CAF-CM by ExoQuick-TC ® and ultracentrifugal separation. We observed GC cells with confocal microscopy after the solution of stained EVs treated. We performed EVs from CAF-CM and GC-CM to mass analysis. Results: GC cells with CAF-CM showed drug resistance on normal coated plates. Moreover, we found that GC cells with CAF-CM on extracellular matrix (ECM)-coated plates showed remarkable morphological change and much higher drug resistance than those without CAF-CM. In contrast, GC cells with GC cell line-CM on ECM- coated plates did not show morphological change. We also found that EVs isolated from CAF-CM caused morphological change and drug resistance of GC cells. Moreover, we identified five proteins included in CAF-EVs as possible candidates involving in GC drug resistance by mass analysis. Gene expression analysis revealed that SNAI2, which is one of the Epithelial Mesenchymal Transition (EMT)-related gene, was significantly up-regulated in GC cells cultured with CAF-CM or EVs from CAF-CM on ECM-coated plates. Conclusion and future perspective: These findings in current study suggest that EVs from CAFs cause characteristic gene expression change and enhance drug resistance along with morphological change of GC cells. We are trying to identify the critical factor in CAF-EVs for drug resistance of GC cells. Citation Format: Tomoyuki Uchihara, Keisuke Miyake, Eri Oda, Yuki Koga, Taisuke Yagi, Daisuke Kuroda, Tsugio Eto, Yuki Kiyozumi, Kota Arima, Hiroshi Sawayama, Yukiharu Hiyoshi, Masaaki Iwatsuki, Yoshifumi Baba, Yuji Miyamoto, Naoya Yoshida, Hideo Baba, Takatsugu Ishimoto. To identify the critical factors in extracellular vesicles derived from cancer-associated fibroblasts for drug resistance of gastric cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5086.

Objective: Gastrointestinal stromal tumor (GIST) is a rare mesenchymal tumor originated from the interstitial cells of Cajal in the gastrointestinal tract. A significant breakthrough was achieved with the identification of the expression of the c-kit (CD117) antigen in GISTs. However, alternate oncogenic pathways have not sufficiently been understood. FBXW7 is a ubiquitin ligase that mediates ubiquitylation of oncoproteins, which is known as tumor-suppressor gene in various malignancies. Previous reports showed that FBXW7 is associated with tumor progression by regulating some oncoprotein such as c-myc and c-jun. The aim of this study is to elucidate the clinicopathological significance of FBXW7 in GIST. Methodology: (i) We examined the FBXW7 expression in GIST cells by immunostaining and correlation clinicopathological characteristics. (ii) We examined cell proliferation by Cytotoxicity assays in GIST-T1 cells suppressed by FBXW7-specific siRNA. Results: (i) In 90 cases of GIST samples with surgical resection, high FBXW7 and observed are 47 cases and low expression are 43 cases. There are significantly more large size, located small intestine, high mitotic index in low FBXW7 cases (P=0.05, P=0.01, P=0.04). There are significantly more high risk cases in modified-Fletcher classification in low FBXW7 expression cases (P=0.0008). There are significantly higher value of SUV max in high risk cases of modified-Fletcher classification and low FBXW7 expression cases (P=0.007, P=0.02). In GIST cases with distant metastasis, there are significantly more low FBXW7 expression cases than GIST cases without distant metastasis (P=0.009). FBXW7 expression is significantly inversely correlated with C-MYC expression (P=0.0004). (ii) The GIST cells suppressed FBXW7 expression by siRNA have higher proliferation rate compared to control GIST cells (P=0.02). Conclusion: We demonstrated that FBXW7 expression is correlated with modified-Fletcher classification, SUV max value, c-myc expression and cell proliferation in GIST. These results are suggesting that FBXW7 may be associated with tumor progression. These findings suggest that it is possible that FBXW7 can be a promising biomarker for disease progression of GIST. Citation Format: Yuki Koga, Masaaki Iwatsuki, Kouhei Yamashita, Yuki Kiyozumi, Hiroshi Sawayama, Yukiharu Hiyoshi, Yoshihfumi Baba, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. The clinicopathoogical significance of FBXW7 expression in GIST [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 557A.

Purpose: Gastric cancer (GC) is the fourth most commonly diagnosed cancer and the third leading cause of cancer mortality worldwide. The range of therapeutic strategies available for the treatment of GC has improved in recent decades. However, the prognosis of patients with advanced GC remains poor even after curative resection, mainly because of recurrence, such as peritoneal dissemination and liver metastases. Previous studies have shown that the interaction between cancer cells and their surrounding stroma plays an important role in tumor development. Cancer-associated fibroblasts (CAFs) have been reported to be involved in invasion and metastasis in cancers, including gastric cancer (GC), via their stimulation of CXCL12/CXCR4 signaling. However, the mechanisms underlying the tumor-promoting effects and the potential of developing therapeutic targets using CXCL12/CXCR4 signaling activated by CAFs are not fully understood. Experimental Design: We first analyzed CXCL12 expression in resected GC tissues of 110 patients by immunohistochemistry (IHC). We next established primary normal fibroblasts (NFs) and CAFs from GC tissues and examined the functional differences between these primary fibroblasts using co-culture assays with GC cell lines. Furthermore, we evaluated the efficacy of a CXCR4 antagonist (AMD3100) and a FAK inhibitor (PF-573,228) on the invasive ability of GC cells. Results: We determined that high CXCL12 expression was significantly associated with larger tumor size, deeper tumor depth, lymphatic invasion and poor prognosis in GC. We established new primary CAFs and their adjacent NFs from resected stomach tissue in GC patients. We evaluated the change in mobility during the direct co-culture of GC cells and fibroblasts using real-time imaging. The motility of GC cells significantly increased upon direct co-culture with CAFs more than it did in cells with NFs compared with control RPMI during observation for 24 hours. The motility of GC cells with CAFs was effectively suppressed by AMD 3100 compared to GC cells with NFs. CXCL12/CXCR4 activation by CAFs mediated the clustering of integrin β1 on the cell surface and promoted the invasive ability of GC cells. Notably, AMD3100 was more efficient at inhibiting GC cell invasion through the suppression of integrin β1/FAK signaling compared with PF-573,228. Conclusions: These results suggest that CXCL12 derived from CAFs promotes invasive ability by enhancing the clustering of integrin β1 in GC cells and results in GC progression. The current data provide evidence that CXCL12/CXCR4 inhibition by AMD3100 is more efficient in suppressing GC cell invasion by not only inhibiting intracellular signaling but also by attenuating the interaction between cancer cells and the extracellular matrix compared with PF-573,228. Our present study represents the rationale for establishing a therapeutic strategy targeting CXCL12/CXCR4 signaling. Citation Format: Daisuke Izumi, Takatsugu Ishimoto, Hidetaka Sugihara, Eto Kojiro, Hiroshi Sawayama, Keisuke Miyake, Yuki Kiyozumi, Keisuke Kosumi, Ryuma Tokunaga, Kazuto Harada, Junji Kurashige, Masaaki Iwatsuki, Shiro Iwagami, Yoshifumi Baba, Yasuo Sakamoto, Yuji Miyamoto, Naoya Yoshida, Masayuki Watanabe, Hideo Baba. CXCL12/CXCR4 activation by cancer-associated fibroblasts promotes integrin β1 clustering and invasive ability in gastric cancer. [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 423. doi:10.1158/1538-7445.AM2015-423

Objectives: DNA methylation change is common epigenetic change in cancer. The promoter CpG island hypermethylation is one of the most common mechanisms by which tumor suppressor miRNAs are inactivated during tumorigenesis. However, microRNA (miRNA) regulations by epigenetic alteration, especially CpG island hypermethylation, have been not yet substantially understood in esophageal squamous cell carcinoma (ESCC). Therefore, we performed the screening of miRNAs which should be up-regulated after 5-aza-20-deoxycytidine (5-Aza) treatment in ESCC cell lines, then from up-regulated miRNAs, we focused on a suppressor miR-145-5p. Since miRNA-145-5p attracts an increasing attention as a tumor suppressor miRNA in ESCC, we evaluated miRNA-145 promoter methylation level and miRNA-145-5p expression level in ESCC Methods: The screening of miRNAs was analyzed using the Human miFinder 384HC miScript miRNA PCR Array. DNA methylation level was evaluated by using bisulfite-pyrosequencing assay. miRNA expression level was evaluated by using TaqMan quantitative real-time reverse transcription-polymerase chain reaction. miRNA-145-5p expression and its promoter methylation levels were quantified in 15 ESCC and matched 15 normal adjacent esophageal mucosa frozen tissues and in 105 formalin-fixed paraffin-embedded ESCC tissues between September 2009 and June 2012 at Kumamoto University Hospital (Kumamoto, Japan). Results Twenty miRNAs including miR-145-5p were up-regulated more than 3 fold in both TE-1 and KYSE30 after 5-Aza treatment by using miRNA PCR array analysis. After 5-Aza treatment, miRNA-145 promoter methylation level decreased and the expression level of miRNA-145-5p was significantly enhanced in 8 of 10 ESCC cell lines. The miRNA-145-5p expression levels in the cancer tissues (mean ± SD; 6.37 ± 1.47) was significantly lower than in matched normal adjacent esophageal epithelial mucosa (235.6 ± 61.9) (p = 0.0024). Moreover, the miRNA-145 promoter in the cancer tissues (41.4 ± 3.05) was significantly hyper methylated than in matched normal adjacent epithelial mucosa (mean; 57.1 ± 3.36) (p = 0.0042 by the paired t test). In 105 ESCC samples, the “high miRNA-145-5p expression level group” and “low miRNA-145-5p expression level group” experienced similar overall survival (Kaplan-Meier analysis; log rank p = 0.58) and disease-free survival (Kaplan-Meier analysis; log rank p = 0.80) Conclusions: Our results suggest that hypermethylation of the miRNA-145 promoter region might regulate miRNA-145 expression in ESCC. This is the first report on the epigenetic regulation of miRNA-145 in ESCC. However, further work is needed to assess our results and to make them more definite. Citation Format: kazuto harada, Yoshifumi Baba, Keisuke Kosumi, Ryuma Tokunaga, Daisuke Izumi, Mayuko Ouchi, Kennichi Nakamura, Yuki Kiyozumi, Junji Kurashige, Yukiharu Hiyoshi, Shiro Iwagami, Yuji Miyamoato, Yasuo Sakamoto, Naoya Yoshida, Masayuki Watanabe, Hideo Baba. Suppressor microRNA-145 is epigenetically regulated by promoter hypermethylation in esophageal squamous cell carcinoma. [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 3132. doi:10.1158/1538-7445.AM2015-3132

Background: The incidence of esophageal adenocarcinoma (EAC) or esophagogastric junction adenocarcinoma (EGJA) has been dramatically increasing. KRAS oncogenic alterations activate multiple pathways in various types of cancer. A recent comprehensive genetic study has reported that around 20% of EAC harbor KRAS copy number gain (Dulak AM et al, 2012, Nat Genet). However, the prognostic role KRAS amplification has not been well examined in EAC/EGJA. Methods: DNA was extracted from formalin-fixed paraffin-embedded tissue of 145 EGJA (Siewert types I-III). KRAS copy number was detected by real-time quantitative PCR, and KRAS copy number gain was defined as KRAS/RNase P (as a reference) ratio ≥ 2.5. The impact of KRAS amplification was analyzed in relation to clinicopathological factors, and patient outcomes [disease free survival (DFS), and overall survival (OS)]. Multivariate cox proportional hazards model was performed adjusting clinicopathological factors. Results: KRAS amplification was observed in 40 (33.1%) cases. KRAS amplification was significantly associated with the lymph node metastasis (P = 0.0145), and was significantly associated with poorer patient outcome (P = 0.0355 in DFS, and P = 0.0067 in OS). In multivariate analysis, KRAS amplification was an independent prognostic factor for OS [multivatiate hazard ratio (HR) = 2.53; 95% confidence interval (CI), 1.22-5.25, P = 0.014] and DFS [multivatiate hazard ratio (HR) = 1.94; 95% confidence interval (CI), 1.04-3.56, P = 0.0382]. Conclusions: KRAS copy number gain may be a useful prognostic marker in EGJA. Citation Format: Kenichi Nakamura, Yu Imamura, Ryuma Tokunaga, Mayuko Ohuchi, Yuki Kiyozumi, Keisuke Kosumi, Daisuke Izumi, Kazuto Harada, Junji Kurashige, Ryuichi Karashima, Yukiharu Hiyoshi, Shiro Iwagami, Yoshifumi Baba, Yasuo Sakamoto, Yuji Miyamoto, Naoya Yoshida, Hiroshi Saeki, Eiji Oki, Yoshihiko Maehara, Hideo Baba. Prognostic impact of KRAS copy number amplification in esophagogastric junction adenocarcinoma. [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 3861. doi:10.1158/1538-7445.AM2015-3861

Backgrounds: APOBEC3B is one of the cytidine deaminase apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC3) family, and APOBEC3B can induce transitions into target DNA through cytidine deamination. To date, APOBEC attracts attention due to its functioning as part of the innate immune system by protecting against retrovirus and retrotransposon propagation. And, recent studies revealed that APOBEC3B might contribute to several mutations in various types of cancers, including cervical, breast, head and neck, lung, bladder cancers, and APOBEC3B may have a crucial role in carcinogenesis and cancer development. Esophageal squamous cell carcinoma (ESCC) reportedly has several molecular features, and we recently reported that long interspersed nucleotide element 1 (LINE-1) hypomethylation might contribute to poor prognosis and PIK3CA mutation to good prognosis in ESCC. However, there is no report which investigates the relationship between APOBEC3B expression, clinical and pathological features in ESCC. Methods: We compared the expression of APOBEC3B mRNA between cancer tissues and noncancerous esophageal mucosae by using GEO profiles and ESCC frozen tissues. In addition, we investigated the relationships between the APOBEC3B immunohistochemical expression levels, clinical and pathological features, and molecular features including p53 expression, global DNA methylation level and PIK3CA mutation. We quantified LINE-1 retrotransposons, of which a substantial portion of the human genome consists, to assess global DNA methylation. Results: APOBEC3B expression at mRNA level was significantly higher in cancer tissues than in noncancerous esophageal mucosae (P = 0.050). In the immunohistochemical study, the APOBEC3B expression of ESCC was stronger than that of noncancerous esophageal mucosa. We found no significant correlation of APOBEC3B expression with tumor size, T stage, N stage and pStage (P = 0.74, P = 0.32, P = 0.19, P = 0.23, respectively). There were no correlation between APOBEC3B expression and prognosis. There was no correlation between APOBEC3B expression and p53 expression (P = 0.23), but, interestingly, a high expression of APOBEC3B was significantly associated with LINE-1 hypomethyaltion and PIK3CA mutation (P = 0.029, P = 0.020). Conclusions: APOBEC3B high expression had significant relationships with LINE-1 hypomethylation and PIK3CA mutation, supporting that APOBEC3B might contribute to malignant behavior through the molecular features in ESCC. Citation Format: Keisuke Kosumi, Yoshifumi Baba, Takatsugu Ishimoto, Kenichi Nakamura, Kazuto Harada, Mayuko Ohuchi, Yuki Kiyozumi, Daisuke Izumi, Ryuma Tokunaga, Junji Kurashige, Ryuichi Karashima, Yukiharu Hiyoshi, Shiro Iwagami, Yasuo Sakamoto, Yuji Miyamoto, Naoya Yoshida, Masayuki Watanabe, Hideo Baba. The clinical significance of APOBEC3B in esophageal squamous cell carcinoma. [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 4829. doi:10.1158/1538-7445.AM2015-4829

Purpose: Colorectal cancer (CRC) is the second most commonly diagnosed cancer and the third leading cause of cancer mortality in Japan. Almost 15% and 10% of patients with CRC are diagnosed with synchronous and metachronous liver metastasis, respectively. In the last decade, the therapeutic strategies including chemotherapy and molecular targeted therapy have improved. However, the prognosis of patients with CRC remains poor because of their acquirement of chemoresistance. Previous studies have shown that enhancer of zeste homologue 2 (EZH2) is associated with proliferation of various cancers. EZH2 is the catalytic subunit of Polycomb repressive complex2 (PRC2) which catalyzes the methylation of lysine 27 on histone H3 (H3K27), leading to repress the transcription of tumor-suppressor genes. In addition, high EZH2 expression is associated with the resistance to cisplatin in non-small cell lung carcinoma. However, the association between the resistance to oxaliplatin and the expression of EZH2 is unrevealed. The aim of this study is to investigate the correlation between the expression of EZH2 and response to oxaliplatin-based chemotherapy as well as survival of patients with colorectal liver metastasis (CRLM). Experimental Design: Sixty-one patients who underwent first-line oxaliplatin-based chemotherapy before resection of CRLM were enrolled in this study. Immunohistochemistry of EZH2 was performed, and then the correlation between response to chemotherapy and survival was evaluated. Results: Immunohistochemistry revealed 38 patients (62.3%) with high EZH2 expression, and 23 patients (37.7%) with low EZH2 expression. Of the 38 patients with EZH2 high expression, 15 patients (39.5%) responded to oxaliplatin-based chemotherapy with either complete response or partial response. Of the 23 patients with low EZH2 expression, 14 patients (60.9%) exhibited a response to chemotherapy. There was significant difference in response to oxaliplatin-based chemotherapy between high and low EZH2 expression patients (p = 0.04). Univariate survival analysis indicated that patients with high EZH2 expression had a lower overall survival than those with low EZH2 expression. Moreover, multivariate Cox regression analysis revealed that high EZH2 expression was an independent prognostic factor for overall survival. Kaplan-Meier survival curves also confirmed that high EZH2 expression correlates with poor prognosis in patients who underwent hepatectomy for CRLM. Conclusions: Our results indicated that prognosis of patients with high EZH2 expression who received preoperative oxaliplatin-based chemotherapy and underwent hepatectomy for CRLM was worse than those with low EZH2 expression. EZH2 may be a predictive factor for oxaliplatin-based chemotherapy response and overall survival in patients with CRLM. Citation Format: Mayuko Ohuchi, Yasuo Sakamoto, Ryuma Tokunaga, Kenichi Nakamura, Yuki Kiyozumi, Daisuke Izumi, Keisuke Kosumi, Kazuto Harada, Junji Kurashige, Yukiharu Hiyoshi, Shiro Iwagami, Yoshifumi Baba, Yuji Miyamoto, Naoya Yoshida, Hideo Baba. Prognostic impact of enhancer of zeste homologue 2 (EZH2) in patients underwent hepatectomy for colorectal liver metastases who received preoperative oxaliplatin-based chemotherapy. [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 2277. doi:10.1158/1538-7445.AM2015-2277