Keiji Kato

Methylated TMS1 and DAPK genes predict prognosis and response to chemotherapy in gastric cancer.

Gastric cancer is the second most common cause of cancer deaths worldwide. The identification of molecular genetic parameters that are associated with response to chemotherapy and prognosis is of utmost interest. We examined methylation of the apoptosis‐related genes, TMS1 and DAPK, in 81 primary gastric cancers using methylation‐specific PCR and compared their methylation status with clinicopathological findings. Aberrant methylation of TMS1 and DAPK genes was detected in 26 (32.1%) tumors and in 18 (22.2%) tumors, respectively. The overall survival of patients with both methylated genes was significantly shorter compared with those with only one methylated gene or no methylated genes (p = 0.0003). Neither gene methylation had any relation to other clinicopathological findings. Next, we examined 43 patients treated by 5‐fluorouracil–based chemotherapy, who had distant metastasis or recurrence after radical resection, to determine the relation between chemosensitivity and methylation. The response rate was lower in patients with either methylation than without (TMS1: 22.2% vs. 48.0%; DAPK: 21.4% vs. 44.8%). Overall survival tended to be shorter in the patients with both methylations compared with either or no methylations (p = 0.0806). The time to progression of patients with methylation of TMS1 or DAPK was significantly shorter than patients without methylation (TMS1: p = 0.0123; DAPK: p = 0.0464). Furthermore, the time to progression of patients with both methylated genes was significantly shorter than patients with one methylation or no methylation (p = 0.0082). In conclusion, TMS1 and DAPK methylation might predict the prognosis and response to chemotherapy in gastric cancer.

Methylation of BNIP3 and DAPK indicates lower response to chemotherapy and poor prognosis in gastric cancer

Aberrant promoter hypermethylation (methylation) is an epigenetic change that silences the expression of crucial genes, thus inactivating the apoptotic pathway in various cancers. Inactivation of the apoptotic pathway has been considered to be associated with chemoresistance. The objective of the present study was to clarify the effect of the methylation of the apoptosis-related genes, Bcl-2/adenovirus E1B 19 kDa-interacting protein 3 (BNIP3) and death-associated protein kinase (DAPK), on the response to chemotherapy in metastatic or recurrent gastric cancers. Tumor samples were obtained from 80 gastric cancer patients who were treated with fluoropyrimidine-based chemotherapy for distant metastatic or recurrent disease, after surgical resection of the primary tumor. The methylation status of the apoptosis-related genes, BNIP3 and DAPK, was investigated by methylation-specific PCR. Methylation in BNIP3 was detected in 31 tumors (39%) and in DAPK in 33 tumors (41%). There was no correlation between the methylation status of BNIP3 and that of DAPK. The response rate was significantly lower in patients with methylation of DAPK, than in those without (21 vs. 49% p=0.012). Progression-free survival time (PFS) was shorter in patients with methylation of DAPK than in those without (p=0.007). The overall survival time (OS) was shorter in patients with methylation of BNIP3 than in those without (p=0.031). The response rate was significantly lower in patients with methylation of either DAPK or BNIP3, or both, than in those without methylation (p=0.003). PFS and OS were significantly shorter in patients with methylation of either or both of these genes than in those without (p=0.002, p=0.001). The methylation of BNIP3 and DAPK can predict lower response to chemotherapy and poor prognosis in gastric cancer.

Vimentin expression is associated with decreased survival in gastric cancer.

Gastric cancer rich in stromal tissue, such as diffuse-type disease, carries a poor prognosis. In some cancers, expression of vimentin, a mesenchymal maker, is associated with poor survival. The expression of mesenchymal markers such as vimentin is observed after epithelial-mesenchymal transition (EMT), an important initial behavioral change related to the adhesion and migration properties of tumor cells that is required for local tumor invasion. A hallmark of EMT is the loss of E-cadherin. EMT-inducing regulators, including SIP1, Slug, and Twist, repress E-cadherin transcription by interacting with E-cadherin promoter. We investigated the expression of vimentin and EMT-related genes, including SIP1, Slug, and Twist, in frozen cancer tissues and normal tissues by real-time quantitative reverse-transcriptase polymerase chain reaction. Tumor samples were obtained from 106 patients with gastric adenocarcinomas who underwent a gastrectomy. The relation of the expression of these genes to clinicopathological factors and outcomes was studied. Vimentin mRNA was significantly higher in diffuse type compared to intestinal type according to Laurens classification (p=0.048) and was significantly elevated in patients with recurrent or distant metastatic disease (p=0.049). Immunohistochemically, however, vimentin was detected only in cancer stroma. Twist mRNA expression significantly correlated with tumor depth (p=0.042) and advanced tumor stage (I-II vs. III-IV, p=0.030). E-cadherin immunohistochemical expression was significantly associated with Laurens histopathological type (p<0.001). Univariate analysis of relapse-free survival showed that tumor depth, lymph node metastasis, Laurens histopathological type, and vimentin mRNA expression were significant prognostic factors (p<0.001, p=0.013, p=0.011, and p=0.019). On multivariate analysis, vimentin mRNA expression was an independent prognostic factor [hazard ratio (HR)=2.1; 95% confidence interval (CI), 1.0-4.4; p=0.036], coming after tumor depth (HR=9.7; 95%CI, 3.7-24; p<0.001). Vimentin mRNA expression is associated with recurrence or distant metastasis and decreased survival in gastric cancer.

Effect of Combined Therapy With Low-Dose 5-Aza-2′-Deoxycytidine and Irinotecan on Colon Cancer Cell Line HCT-15

BackgroundAberrant promoter hypermethylation is an epigenetic change that silences the expression of crucial genes, resulting in inactivation of the apoptotic pathway in various cancers. This hypermethylation can be restored by the demethylating agent 5-aza-2′-deoxycytidine (DAC). DAC might increase the tumor sensitivity to chemotherapy through demethylation and restoration of gene expression. We investigated the effect of combined therapy with DAC and irinotecan (CPT-11) on the human colon cancer cell line HCT-15.MethodsHuman colon cancer cell line HCT-15 was treated with DAC and/or CPT-11 both in vitro and in vivo. The changes in mRNA expression of several apoptosis-related genes were investigated by reverse transcriptase–polymerase chain reaction (PCR). Promoter methylation was detected by methylation-specific PCR and combined bisulfite restriction analysis. Suppression of tumor growth was observed during the treatment with DAC and/or CPT-11 and apoptosis in the tumors was investigated by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) assay.ResultsPromoter methylation of p14ARF, p16INK4a, BNIP3, and XAF1 was confirmed, and DAC restored mRNA expression of these genes. Demethylation and restoration of gene expression was observed with low-dose DAC, and demethylation status was sustained for several weeks. Combined therapy with DAC and CPT-11 produced marked suppression in tumor growth compared with DAC or CPT-11 alone, both in vitro and in vivo.ConclusionsPretreatment with low-dose DAC may have the potential to be used as a “biosensitizer” of DNA-damaging agents such as CPT-11 when the apoptotic pathway is inactivated as a result of aberrant promoter methylation in the cancer.

Prognostic value of RKIP and p-ERK in gastric cancer

BackgroundThe mitogen-activated protein kinase (MAPK) signaling pathway participates in several steps of tumour development and is considered a prominent therapeutic target for the design of chemotherapeutic agents. We evaluated the expressions of extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MEK), an upstream regulator of ERK, and Raf kinase inhibitor protein (RKIP), and investigated correlations of these expressions with clinicopathological features and outcomes in gastric cancer.MethodsTumour samples were obtained from 105 patients with gastric adenocarcinomas who underwent radical gastrectomy. The expressions of phosphorylated ERK (p-ERK), phosphorylated MEK (p-MEK), and RKIP were analysed by immunohistochemical staining.ResultsExpression of RKIP, p-MEK, and p-ERK was found in 69 (66%), 54 (51%), and 64 (61%) of all tumours, respectively. RKIP expression negatively correlated with the depth of invasion (p < 0.001), lymph node involvement (p = 0.028), and Union for International Cancer Control (UICC) stage (p = 0.007). RKIP expression was associated with significantly longer relapse-free survival (RFS) (p = 0.0033), whereas p-MEK was not (p = 0.79). Patients with p-ERK expression had slightly, but not significantly shorter RFS than those without such expression (p = 0.054). Patients with positive p-ERK and negative RKIP expression had significantly shorter RFS than the other patients (p < 0.001). The combination of RKIP and p-ERK expression was an independent prognostic factor (hazard ratio, 2.4; 95% confidence interval, 1.3 - 4.6; p = 0.008).ConclusionsOur results demonstrated that loss of RKIP was associated with tumour progression and poor survival. Negative RKIP expression combined with positive p-ERK expression was an independent predictor of poor outcomes in patients with gastric cancer.

The Synergistic Effect of 5-Aza-2′-Deoxycytidine and 5-Fluorouracil on Drug-Resistant Tumors

Purpose: We investigated whether a 5-fluorouracil (5-FU)-resistant tumor could regain chemosensitivity after the administration of 5-aza-2′-deoxycytidine (DAC) as a demethylating agent. Methods: Human colorectal cancer cells (SW48) are characterized by the hypermethylation of proapoptotic genes. They were transplanted into 20 athymic BALB/c nu/nu mice which were randomly placed into 4 groups (1 = control; 2 = 5-FU alone; 3 = DAC alone; 4 = DAC followed by 5-FU). We evaluated the synergistic effect of DAC and 5-FU on the growth of these xenografts. Reactivation of proapoptotic genes in these cells was analyzed by methylation-specific PCR. Gene expression was determined by a quantitative reverse-transcription PCR assay. Results: Compared with the control group, relative tumor volumes were statistically significantly decreased only in group 4 mice (p = 0.006). In groups 3 and 4, p14, p16 and death-associated protein kinase (DAPK) promoter regions were demethylated and p14 gene expression was gradually increased after DAC administration. Conclusion: DAC could be a useful medicine that breaks the silencing of various genes and recovers some expressions. By pretreating with DAC at a nontoxic level, we confirmed the restoration of 5-FU chemosensitivity and apoptosis induction. The combination of demethylating agents and several cytotoxic drugs has potential in clinical practice.

EphA4 is a prognostic factor in gastric cancer

BackgroundErythropoietin-producing hepatocellular (Eph) receptor, consisting of a family of receptor tyrosine kinases, plays critical roles in tumour development and is considered an attractive target for cancer therapy.MethodsTumour samples were obtained from 222 patients with gastric adenocarcinoma who underwent gastrectomy. The expressions of EphA2, EphA4, and ephrinA1 were evaluated immunohistochemically.ResultsHigh expressions of EphA2, EphA4, and ephrinA1 significantly correlated with variables related to tumour progression, including the depth of invasion, metastatic lymph nodes, pathological stage, and distant metastasis or recurrent disease. High expressions of EphA2, EphA4, and ephrinA1 were significantly associated with poorer disease-specific survival (DSS; p < 0.001, p < 0.001, p = 0.026). On multivariate analysis, EphA4 was an independent prognostic factor of DSS (hazard ratio [HR], 2.3; 95% confidence interval [CI], 1.1-4.8; p = 0.028), and EphA2 tended to be a prognostic factor (HR, 2.4; 95% CI, 1.0-5.8; p = 0.050). In stage II and III cancer, EphA4 and EphA2 were both significantly associated with shorter survival (p = 0.007 and 0.019), but only EphA2 was an independent prognostic factor (HR, 2.6; 95% CI, 1.1-6.3; p = 0.039).ConclusionEphA4 may play important roles in tumor progression and outcomes in patients with gastric cancer.

Impact of comorbidities on postoperative complications in patients undergoing laparoscopy-assisted gastrectomy for gastric cancer.

BackgroundComorbidity is a predictor of postoperative complications (PCs) in gastrectomy. However, it remains unclear which comorbidities are predictors of PCs in patients who undergo laparoscopy-assisted gastrectomy (LAG). Clinically, insufficient lymphadenectomy (LND) is sometimes performed in high-risk patients, although the impact on PCs and outcomes remains unclear.MethodsWe retrospectively studied 529 patients with gastric cancer (GC) who underwent LAG. PCs were defined as grade 2 or higher events according to the Clavien-Dindo classification. We evaluated various comorbidities as risk factors for PCs and examined the impact of insufficient LND on PCs in patients with risky comorbidities.ResultA total of 87 (16.4%) patients had PCs. There was no PC-related death. On univariate analysis, heart disease, central nervous system (CNS) disease, liver disease, renal dysfunction, and restrictive pulmonary dysfunction were significantly associated with PCs. Both liver disease and heart disease were significant independent risk factors for PCs on multivariate analysis (odds ratio [OR] = 3.25, p = 0.022; OR = 2.36, p = 0.017, respectively). In patients with one or more risky comorbidity, insufficient LND did not significantly decrease PCs (p = 0.42) or shorten GC-specific survival (p = 0.25).ConclusionIn patients who undergo LAG for GC, the presence of heart disease or liver disease is an independent risk factor for PC. Insufficient LND (for example, D1+ for advanced GC) might be permissible in high-risk patients, because although it did not reduce PCs, it had no negative impact on GC-specific survival.

CD49fhigh Cells Retain Sphere-Forming and Tumor-Initiating Activities in Human Gastric Tumors

Identification of gastric tumor-initiating cells (TICs) is essential to explore new therapies for gastric cancer patients. There are reports that gastric TICs can be identified using the cell surface marker CD44 and that they form floating spheres in culture, but we could not obtain consistent results with our patient-derived tumor xenograft (PDTX) cells. We thus searched for another marker for gastric TICs, and found that CD49fhigh cells from newly-dissected gastric cancers formed tumors with histological features of parental ones while CD49flow cells did not when subcutaneously injected into immunodeficient mice. These results indicate that CD49f, a subunit of laminin receptors, is a promising marker for human gastric TICs. We established a primary culture system for PDTX cells where only CD49fhigh cells could grow on extracellular matrix (ECM) to form ECM-attaching spheres. When injected into immunodeficient mice, these CD49fhigh sphere cells formed tumors with histological features of parental ones, indicating that only TICs could grow in the culture system. Using this system, we found that some sphere-forming TICs were more resistant than gastric tumor cell lines to chemotherapeutic agents, including doxorubicin, 5-fluorouracil and doxifluridine. There was a patient-dependent difference in the tumorigenicity of sphere-forming TICs and their response to anti-tumor drugs. These results suggest that ECM plays an essential role for the growth of TICs, and that this culture system will be useful to find new drugs targeting gastric TICs.

Gastric Carcinoma: Ex Vivo MR Imaging at 7.0 T–Correlation with Histopathologic Findings

PURPOSE To determine the imaging detail and diagnostic information that can be obtained at 7.0-T magnetic resonance (MR) imaging with a voxel volume of 9.5-14.0 nL as a means of evaluating the depth of mural invasion by gastric carcinomas ex vivo. MATERIALS AND METHODS This study was approved by the institutional review board, and written informed consent was obtained from each patient. Twenty gastric specimens containing 20 carcinomas were studied with a 7.0-T MR imaging system equipped with a four-channel surface coil. MR images were obtained with a 50-60 × 25-30 mm field of view, a 512 × 256 matrix, and a 1.0-mm section thickness, resulting in a voxel volume of 0.0095-0.0140 mm(3) (9.5-14.0 nL). The signal intensity of the gastric wall layers, tumor tissue, and fibrosis was described as low, intermediate, or high by comparing it with the signal intensity of the muscularis propria. Depth of invasion initially was assessed by two reviewers independently and then by the two reviewers in consensus. MR images were compared with histopathologic findings. RESULTS The 7.0-T T2-weighted MR images clearly depicted the normal gastric wall in all 20 specimens (100%) as consisting of seven layers, which clearly corresponded to the tissue layers of the gastric wall. These MR images enabled clear differentiation between tumor tissue and fibrosis. Reviewers disagreed on the depth of invasion at the initial reading in three (15%) of 20 specimens (between mucosa and submucosa in two specimens and between muscularis propria and subserosa and serosa in one specimen); however, in all 20 gastric carcinomas, the depth of invasion could be accurately determined on T2-weighted images after consensus interpretation. CONCLUSION Ex vivo 7.0-T MR imaging enables clear delineation of the gastric wall layers and clear differentiation of tumor tissue from fibrosis and allows one to assess the depth of mural invasion by gastric carcinomas.