Kazuya Yasui

Abstract 2317: PD-1 and PD-L1 expression patterns and DNA mismatch repair status for precision management of patients with gastric cancer

BACKGROUND: Programmed cell death protein 1 (PD-1) and its ligand (PD-L1) downregulate T cell activation and are related to immune tolerance. Recently, microsatellite unstable (MSI) colorectal cancers have been shown to have good therapeutic response to PD-1 antibody immunotherapy, possibly due to release exhaustion of their ability to recognize high number of tumor neo-antigens. The aim of this study was to clarify the significance of PD-1 and PD-L1 expression, and to analyze the relationship between MSI status and MLH1 hypermethylation status in gastric cancer. METHODS: A total of 105 patients who underwent curative gastrectomy for gastric cancer were included in this study. The PD-1, PD-L1, HER2, and mismatch repair proteins (MLH1/PMS2/MSH2/MSH6) expression were examined by immunohistochemistry. MSI status were examined by analyzing three mononucleotide repeat markers. MLH1 methylation was evaluated using a highly sensitive fluorescence-based PCR assay, as we reported previously (JNCI 2009). KRAS/BRAF/PIK3CA mutations were determined by conventional Sanger sequencing. Infection of Helicobacter Pylori (H. Pylori) and EB virus (EBV) were determined by amplifying H. Pylori and EBV specific sequence by PCR, followed by conventional Sanger sequencing. RESULTS: PD-1 and PD-L1 were expressed in 40% (38/95) and 33% (31/95) gastric cancers, respectively. HER2 was expressed in 15% (14/96) gastric cancers. Infection of H.Pylori and EBV were observed in 71% (70/98) and 8% (8/98) gastric cancers, respectively. MSI was observed in 13% (13/98) gastric cancers. Among 13 MSI cancers, 11 cases (85%) showed extensive methylation in the MLH1 promoter region, suggesting their sporadic manifestation. KRAS (exon 2), BRAF (exon 15) and PIK3CA (exon 9 & 20) mutations were observed in 5% (5/98), 0% (0/98), and 4% (4/98), respectively. Among these, one case harbored simultaneous KRAS and PIK3CA mutation. Gastric cancers with KRAS/PIK3CA were more frequently MSI-positive (5/8, p = 0.003). Among eight EBV infected cancers, only one case showed MSI and MLH1 methylation. PD-1 expression was significantly correlated with PD-L1 expression (p = 0.04). Although both PD-1 and PD-L1 expression were associated with MSI (p = 0.007 and p = 0.008, respectively), only PD-L1 expression was significantly correlated with gastric cancers with MLH1 methylation (p = 0.01). While expression of immune checkpoint molecules were specific for tumors with MMR deficiency, HER2 expression was exclusively observed in MMR-proficient tumors. CONCLUSIONS: PD-1/PD-L1 expression is associated with MMR-deficient gastric cancers. In contrast, HER2 expression is observed exclusively in gastric cancers with MMR-proficiency. Our result highlight that expression analysis of genetic markers could lead the precision management of patients with gastric cancer. Citation Format: Keisuke Kimura, Takeshi Nagasaka, Yoshiko Mori, Takashi Kawai, Tomokazu Fuji, Fumitaka Taniguchi, Kazuya Yasui, Toshiaki Toshima, Yuzo Umeda, Hiroshi Tazawa, Ajay Goel, Toshiyoshi Fujiwara. PD-1 and PD-L1 expression patterns and DNA mismatch repair status for precision management of patients with gastric cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2317.

Clinical outcomes of women with ovarian metastases of colorectal cancer treated with oophorectomy with respect to their somatic mutation profiles

We clarified the clinical prevalence of ovarian metastases from colorectal cancers (CRCs) in 296 female patients with CRC and evaluated clinical outcomes with relation to their mutational profiles, such as BRAF/KRAS mutation and microsatellite instability (MSI) status. The female CRCs were categorised into three subsets: CRCs with ovarian metastases [6.4% (n = 19), 5-year overall survival (OS) = 24.7%], CRCs with extra-ovarian metastases only [32.4% (n = 96), 5-year OS = 34.5%] and CRCs without any recurrence or metastasis [61.2% (n = 181), 5-year OS = 91.3%]. All patients with ovarian metastases underwent oophorectomy; of these, 9 who received preoperative chemotherapy had measurable metastases to extra-ovarian sites and the ovaries. Although 5 of 9 (56%) achieved partial response or complete response at extra-ovarian sites, no patient archived objective response at ovarian sites. Regarding the mutation profiles, in CRCs with extra-ovarian metastases only, the median survival time (MST) after initial treatments to progression to stage IV or recurrence was 13 [95% confidence interval (CI): 7–16 months] in BRAF-mutant and 34 months (95% CI: 22–58 months) in BRAF wild-type (P = 0.0033). Although ovarian metastases demonstrated poor response to systemic chemotherapy in CRCs with ovarian metastases, the MST after initial treatments to progression to stage IV or recurrence was 22 (95% CI: 21–25 months) in BRAF-mutant and 38 months (95% CI: 24–42 months) in BRAF wild-type (P = 0.0398). The outcomes of patients with ovarian metastases could be improved by oophorectomy regardless of their mutation profiles.

Heterogeneity of Epigenetic and Epithelial Mesenchymal Transition Marks in Hepatocellular Carcinoma with Keratin 19 Proficiency

Objective: Keratin 19 (K19) expression is a potential predictor of poor prognosis in patients with hepatocellular carcinoma (HCC). To clarify the feature of K19-proficient HCC, we traced epigenetic footprints in cultured cells and clinical materials. Patients and Methods: In vitro, KRT19 promoter methylation was analyzed and 5-aza-2’-deoxycytidine with trichostatin A (TSA) treatment was performed. Among 564 surgically resected HCCs, the clinicopathological relevance of K19-proficent HCCs was performed in comparison with hepatocytic (HepPar-1 and arginase-1), epithelial-mesenchymal transition (E-cadherin and vimentin), biliary differentiation-associated (K7 and NOTCH-1) markers, and epigenetic markers (KRT19 promoter/long interspersed nucleotide element-1 [LINE-1] methylation status). Results: KRT19 promoter methylation was clearly associated with K19 deficiency and 5-aza-2’-deoxycytidine with TSA treatment-stimulated K19 re-expression, implicating DNA methylation as a potential epigenetic process for K19 expression. After excluding HCCs with recurrence, TNM stage as IIIB or greater, preoperative therapy, transplantation, and combined hepatocellular cholangiocarcinoma, we assessed 125 of 564 HCC cases. In this cohort, K19 expression was found in 29 HCCs (23.2%) and corresponded with poor survival following surgery (p = 0.025) and extrahepatic recurrence-free survival (p = 0.017). Compared with K19-deficient HCCs, lower KRT19 promoter methylation level was observed in K19-proficient HCCs (p < 0.0001). Conversely, HCC with genome-wide LINE-1 hypermethylation was frequently observed in K19-proficient HCCs (p = 0.0079). Additionally, K19 proficiency was associated with K7 proficiency (p = 0.043), and reduced E-cadherin and HepPar-1 expression (p = 0.043 and p < 0.0001, respectively). Conclusions: K19-proficient HCC exhibited poor prognosis owing to extrahepatic recurrence, with molecular signatures differing from those in conventional cancer stem cells, providing novel insights of the heterogeneity underlying tumor development.

Abstract 510: A novel circulating cell free DNA-based assay in colorectal cancer patients during treatment with systematic chemotherapy

Introduction: Although circulating cell-free DNA (cfDNA) in blood plasma is being touted as a frontier noninvasive approaches, its clinical utility still remains questionable. The purpose of this study was to compare the efficacy of cfDNA by comparing blood CEA levels and radiological evaluation in patients with unresectable metastatic colorectal cancer (mCRC) who received systemic chemotherapy. Experimental Procedures: In this study, we measured aberrant cancer-specific methylation in cfDNA and the concentration of cfDNA in plasma obtained following each treatment cycle of systemic chemotherapy in three patients with mCRC. To analyze aberrant cancer-specific methylation, we used a modified highly sensitive assay for bisulfite DNA followed by fluorescence-based PCR, as reported previously (JNCI 2009). This methodology can detect methylation status in eight regions, therefore both recovery score (RS) and methylation score (MS), ranged from 0-8 at a given time. We measured RS and MS two-times in each plasma specimen obtained before administration of systemic chemotherapies. Results: In this pilot study, we examined a series of blood plasma obtained from three patients who received oxaliplatin-based chemotherapy together with molecularly-targeted agents. Despite initial tumor shrinkage in the metastases, all patients ultimately developed progressive disease (PD). Patient1 had wild-type KRAS, but had developed a sigmoid colon cancer with synchronous multiple liver and lung metastases. In contrast, Patient2 had mutant KRAS with sigmoid colon cancer and synchronous multiple liver metastasis. Both patients 1 and 2, demonstrated decreasing levels of CEA after the first-line chemotherapy, along with low methylation scores and concentration of cfDNA. Interestingly, in both patients, MS and concentration level of cfDNA increased prior to radiographic documentation of PD. Patient3 harbored BRAF V600E mutation, and a cancer in the ascending colon with systemic lymph node metastasis. Although, in this case, the tumor development progressed rapidly, similar to patients 1 and 2, MS and the concentration levels of cfDNA also increased prior to radiographic documentation of rapid PD. Conclusions: Our novel DNA methylation and concentration-based monitoring assay is a novel methodology for capturing DNA methylation in circulating cell-free DNA in plasma, and is useful for the early identification of colorectal cancer patients who are at risk of developing PD prior to radiographic documentation. Citation Format: Toshiaki Toshima, Takeshi Nagasaka, Yoshiko Mori, Takashi Kawai, Tomokazu Fuji, Fumitaka Taniguchi, Keisuke Kimura, Kazuya Yasui, Hiroyuki Kishimoto, Yuzo Umeda, Hiroshi Tazawa, Ajay Goel, Toshiyoshi Fujiwara. A novel circulating cell free DNA-based assay in colorectal cancer patients during treatment with systematic chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 510.

Abstract 1078: Micro RNAs as promising therapeutic targets for anti-metastatic therapy in colorectal cancer

Background: Colorectal cancer (CRC) is the third most common cancer and is a leading cause of cancer related death worldwide and arises by accumulation of genetic and epigenetic alterations. Recently, it has been demonstrated that microRNAs (miRNAs) play critical roles in tumor progression in various cancers. In this study, we tried to find miRNAs associated with distant metastasis and poor outcome and evaluate those miRNAs as therapeutic target for advanced CRC. Methods: MiRNA array was done on CRC specimens derived from tumors with various gene status (KRAS/BRAF/microsatellite instability [MSI] status) with reference of their normal mucosal specimens. The array analysis revealed that a set of miRNAs was specifically down-regulated in CRC with BRAF V600E mutation without MSI, considered to be the poorer outcome. To examine whether the set of miRNAs causes distant metastasis or not, we investigated malignant potential of cell lines transfected and knock-downed the set of miRNAs by siRNA. Expression status of ZEB2 and Epithelial-Mesenchymal Transition (EMT) markers, E-cadherin, were evaluated. In addition, we analyzed expression level of the set of miRNAs in a cohort of 67 stage IV CRCs (TNM staging system by UICC 7th) by quantitative reverse transcription PCR using a comparative Ct method and examined association of target-miRNA fold change (tumor/normal tissue) and their clinocopathilogical findings. Patient survival analysis were performed by Cox proportional hazard model and Kaplan-Meier analysis. Results: In vitro, cell lines transfected the set of miRNAs significantly reduced their malignant potentials. In contrast cell lines knock-downed the set of miRNAs by siRNA obviously increased their malignant potentials. Finally, to confirm our results obtained from in vitro assays, we analyzed expression level of the set of miRNAs in a cohort of stage IV CRCs. Of 67 patients with stage IV CRCs, 15 patients showed KRAS mutation, 4 patients showed BRAF mutation. CRCs with the lower expression level of the set of miRNAs showed poor outcome compared with those with the higher expression level by Cox proportional hazard model and Kaplan-Meier analysis. Conclusions: Our data indicate that miRNAs associated with BRAF mutant CRCs is promising prognostic biomarkers and therapeutic targets for anti-metastatic therapy in CRC. Citation Format: Takashi Kawai, Takeshi Nagasaka, Yoshiko Mori, Tomokazu Fuji, Fumitaka Taniguchi, Keisuke Kimura, Toshiaki Toshima, Kazuya Yasui, Yuzo Umeda, Hiroshi Tazawa, Ajay Goel, Toshiyoshi Fujiwara. Micro RNAs as promising therapeutic targets for anti-metastatic therapy in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1078.