Seung Sam Paik

MTA1 overexpression correlates significantly with tumor grade and angiogenesis in human breast cancers

Metastasis associated antigen 1 (MTA1) is a recently identified candidate metastasis‐associated gene that plays an important role in tumorigenesis and tumor aggressiveness, especially tumor invasiveness and metastasis. We analyzed the relationship between MTA1 expression and variable clinicopathological features and characterized its role in tumor angiogenesis in human breast cancers. Two hundred and sixty‐three breast cancer cases that successfully underwent surgery at Hanyang University Hospital (Seoul, Korea) between January 1989 and December 1997 were enrolled. MTA1 expression was observed by immunohistochemical staining and correlated with intratumoral microvessel density (MVD) and other clinicopathological parameters. MTA1 overexpression correlated significantly with higher tumor grade (grades 1 and 2 vs grade 3, P = 0.009). However, MTA1 expression did not correlate with tumor stage, status of estrogen and progesterone receptors, or axillary lymph node metastasis. Interestingly, MTA1 expression was found to correlate significantly with tumor MVD (P = 0.002). Survival analysis did not show a significant difference between MTA1 overexpression and poorer survival. In conclusion, MTA1 overexpression was found to be closely associated with higher tumor grade and increased tumor angiogenesis. These findings suggest MTA1 as a predictor of aggressive phenotype and a possible target molecule for anti‐angiogenic drugs in breast cancer treatment. (Cancer Sci 2006)

In Vitro Differentiation of Mouse Embryonic Stem Cells: Enrichment of Endodermal Cells in the Embryoid Body

Embryonic stem (ES) cells have the potential to differentiate into all three germ layers, providing new perspectives not only for embryonic development but also for the application in cell replacement therapies. Even though the formation of an embryoid body (EB) in a suspension culture has been the most popular method to differentiate ES cells into a wide range of cells, not much is known about the characteristics of EB cells. To this end, we investigated the process of EB formation in the suspension culture of ES cells at weekly intervals for up to 6 weeks. We observed that the central apoptotic area is most active in the first week of EB formation and that the cell adhesion molecules, except β‐catenin, are highly expressed throughout the examination period. The sequential expression of endodermal genes in EBs during the 6‐week culture correlated closely with that of normal embryo development. The outer surface of EBs stained positive for α‐fetoprotein and GATA‐4. When isolated from the 2‐week‐old EB by trypsin treatment, these endodermal lineage cells matured in vitro into hepatocytes upon stimulation with various hepatotrophic factors. In conclusion, our results demonstrate that endodermal cells can be retrieved from EBs and matured into specific cell types, opening new therapeutic usage of these in vitro differentiated cells in the cell replacement therapy of various diseases.

Clinicopathological significance of nuclear PTEN expression in colorectal adenocarcinoma.

Jang K‐S, Song Y S, Jang S‐H, Min K‐W, Na W, Jang S M, Jun Y J, Lee K H, Choi D & Paik S S
(2010) Histopathology56, 229–239

CT analysis and histopathology of bone remodeling in patients with chronic rhinosinusitis

Objective To evaluate the findings of computed tomography (CT) and histopathology of the bulla ethmoidalis as objective markers of bone remodeling in chronic rhinosinusitis (CRS). Methods Preoperative ostiomeatal unit (OMU) scans and histopathologic findings of the bulla ethmoidalis were performed on 23 patients (39 sides) undergoing endoscopic sinus surgery for CRS. Lund-Mackay scores and Hounsfield units (HU) of the bulla were checked in coronal CT scans. The pathologist graded the severities of the mucosal and bony changes in histopathology. Statistical analysis was performed using Mann-Whitney U test and Spearman correlation coefficient (r). Results The HU values of the bulla were significantly increased with higher Lund-Mackay scores in OMU CT (r = 0.405, P = 0.01). The bony grades in histopathology were significantly increased with higher mucosal grades (r = 0.821, P = 0.0001). These findings in CT scans and histopathology were well correlated with each other (r > 0.3, P < 0.05). Conclusion HU may be a useful objective marker of bone remodeling in chronic rhinosinusitis.

Loss of SIRT1 histone deacetylase expression associates with tumour progression in colorectal adenocarcinoma.

Background The class III histone deacetylase SIRT1 is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, and has been reported to serve diverse roles in various biological processes, such as caloric restriction, apoptosis, neuronal protection, cell growth, differentiation and tumourigenesis. With respect to tumourigenesis, there have been conflicting data supporting whether SIRT1 act as a tumour promoter or as a tumour suppressor. Methods SIRT1 protein expression, determined by immunohistochemistry, was investigated in human normal colonic mucosa, adenoma, adenocarcinoma and metastatic tissue samples. Results All normal colonic mucosa showed SIRT1 expression with no exception, and 42 (80.8%) of 52 adenomatous polyps were positive for SIRT1. However, only 208 (41.9%) of 497 colorectal adenocarcinomas were positive. Moreover, 45 (35.7%) of 126 metastatic tissues were positive. Collectively, the SIRT1 expression was gradually decreased during carcinogenesis and tumour progression. The associations between SIRT1 expression and clinicopathological parameters revealed that loss of SIRT1 expression was associated with proximal tumour location, mucinous histology and defective mismatch repair protein expression. This suggests that loss of SIRT1 expression is associated with the microsatellite instability phenotype of colorectal adenocarcinoma. In survival analyses, the loss of SIRT1 expression was significantly associated with overall survival (p=0.027, log-rank test) in univariable analysis, but multivariable analysis failed to achieve significance. Conclusions SIRT1 expression was gradually decreased during the normal–adenoma–adenocarcinoma–metastasis sequence, suggesting a possible role of SIRT1 in tumour suppression in the colorectum, and a probable link to the microsatellite instability pathway.

Epithelial–mesenchymal transition gene signature to predict clinical outcome of hepatocellular carcinoma

Hepatocellular carcinoma is one of the most lethal cancers worldwide. More accurate stratification of patients at risk is necessary to improve its clinical management. As epithelial–mesenchymal transition is critical for the invasiveness and metastasis of human cancers, we investigated expression profiles of 12 genes related to epithelial–mesenchymal transition through a real‐time polymerase chain reaction. From a univariate Cox analysis for a training cohort of 128 hepatocellular carcinoma patients, four candidate genes (E‐cadherin [CDH1], inhibitor of DNA binding 2 [ID2], matrix metalloproteinase 9 [MMP9], and transcription factor 3 [TCF3]) with significant prognostic values were selected to develop a risk score of patient survival. Patients with high risk scores calculated from the four‐gene signature showed significantly shorter overall survival times. Moreover, the multivariate Cox analysis revealed that four‐gene signature (P = 0.0026) and tumor stage (P = 0.0023) were independent prognostic factors for overall survival. Subsequently, the four‐gene signature was validated in an independent cohort of 231 patients from three institutions, in which high risk score was significantly correlated with shorter overall survival (P = 0.00011) and disease‐free survival (P = 0.00038). When the risk score was entered in a multivariate Cox analysis with tumor stage only, both the risk score (P = 0.0046) and tumor stage (P = 2.6 × 10−9) emerged as independent prognostic factors. In conclusion, we suggest that the proposed gene signature may improve the prediction accuracy for survival of hepatocellular carcinoma patients, and complement prognostic assessment based on important clinicopathologic parameters such as tumor stage. (Cancer Sci 2010)

Radiofrequency Ablation of the Liver in a Rabbit Model: Creation of Artificial Ascites to Minimize Collateral Thermal Injury to the Diaphragm and Stomach

PURPOSE To assess whether the creation of artificial ascites during radiofrequency (RF) ablation of the subcapsular portion of the liver can minimize collateral thermal injury to the diaphragm and stomach. MATERIALS AND METHODS A total of 20 percutaneous RF ablation procedures were performed in the livers of 10 rabbits (control, n = 5; experimental, n = 5) with use of an internally cooled electrode (1-cm active tip). In the experimental group, artificial ascites was established before RF ablation by dripping 320 mL of normal saline solution via a 20-gauge sheathed needle to separate the liver from the diaphragm and stomach. In each rabbit, two subcapsular ablation zones were made in the inferior tip of the left lobe of the liver adjacent to the stomach and in the far dome of the right lobe next to the diaphragm consecutively. After the animals were killed 3 days after the procedure, the frequency, size, and degree of thermal injury were compared between the experimental and control groups. The degree of thermal injury was graded by visual inspection according to a four-point scoring system. Representative cases underwent gross and histologic analysis. RESULTS Artificial ascites was achieved successfully with a single puncture in all rabbits in the experimental group. Mean procedure time for the formation of artificial ascites was 9 minutes. There was no difference in the size of the RF ablation zones in the liver between the two groups (P > .05). Thermal injury in the adjacent organs was observed significantly more frequently in the control group compared with the experimental group (diaphragm, 100% vs 0; stomach, 80% vs 20%; P < .05). CONCLUSION Creation of artificial ascites may be a simple and useful technique that can be used to reduce the frequency and severity of thermal injury during RF ablation of subcapsular hepatic tumors.

Reduced expression of Apaf-1 in colorectal adenocarcinoma correlates with tumor progression and aggressive phenotype.

BackgroundApoptotic protease activating factor-1 (Apaf-1) is one of the key regulators in the mitochondrial apoptotic pathway, and the loss of Apaf-1 leads to cellular resistance against the apoptotic signals. We investigated the expression of Apaf-1 in colorectal tissues corresponding to the multistep carcinogenesis model to determine correlations between the clinicopathologic characteristics and the expression of this molecule and to evaluate the role of Apaf-1 in the development and progression of colorectal adenocarcinoma.MethodsImmunohistochemistry for Apaf-1 was performed on the tissue microarray of 38 normal mucosal tissues, 46 adenomatous polyps, 529 colorectal adenocarcinomas, and 76 metastatic tumors.ResultsNormal colonic mucosa tissues and adenomas were positive for Apaf-1 with no exceptions (100%). However, in colorectal adenocarcinomas, 119 of 529 cases (22.5%) were positive and 410 cases (77.5%) were negative. Moreover, 67 of 76 metastatic cases (88.2 %) were negative and only nine cases (11.8%) were positive for Apaf-1 expression. In the analyses between Apaf-1 expression and clinicopathologic parameters, reduced expression of Apaf-1 correlated with left colon location (p < 0.001), deeper tumor invasion (p < 0.001), frequent lymph node metastasis ( p= 0.021), higher American Joint Committee on Cancer (AJCC) and Dukes’ stage (p = 0.02 and p = 0.001, respectively) and poorer differentiation (p < 0.001). The patient survival was significantly associated with age, histological grade, AJCC stage, and lymphovascular invasion, but not Apaf-1 expression (p = 0.478).ConclusionsThe results suggest that the loss of Apaf-1 expression is a relatively frequent late event and the loss of Apaf-1 expression may play an important role in tumorigenesis and tumor progression in colorectal adenocarcinoma.

Stable hepatocyte transplantation using fibrin matrix

Fibrin matrix, a naturally derived biodegradable polymer matrix, was evaluated as a scaffold for hepatocyte transplantation in an athymic mouse model. One week after transplantation, opaque conglomerates of the transplanted hepatocytes and fibrin matrix were found on the intestinal mesentery, whereas no transplanted hepatocytes were observed in control groups (transplantation of hepatocytes suspended in culture medium). The hepatocytes in the conglomerates retained hepatocyte-specific functions, as examined with histochemical and immunohistochemical stainings. Stable hepatocyte engraftment may thus be achieved by hepatocyte transplantation using fibrin matrix.

Novel tumor suppressive function of Smad4 in serum starvation-induced cell death through PAK1–PUMA pathway

DPC4 (deleted in pancreatic cancer 4)/Smad4 is an essential factor in transforming growth factor (TGF)-β signaling and is also known as a frequently mutated tumor suppressor gene in human pancreatic and colon cancer. However, considering the fact that TGF-β can contribute to cancer progression through transcriptional target genes, such as Snail, MMPs, and epithelial–mesenchymal transition (EMT)-related genes, loss of Smad4 in human cancer would be required for obtaining the TGF-β signaling-independent advantage, which should be essential for cancer cell survival. Here, we provide the evidences about novel role of Smad4, serum-deprivation-induced apoptosis. Elimination of serum can obviously increase the Smad4 expression and induces the cell death by p53-independent PUMA induction. Instead, Smad4-deficient cells show the resistance to serum starvation. Induced Smad4 suppresses the PAK1, which promotes the PUMA destabilization. We also found that Siah-1 and pVHL are involved in PAK1 destabilization and PUMA stabilization. In fact, Smad4-expressed cancer tissues not only show the elevated expression of PAK1, but also support our hypothesis that Smad4 induces PUMA-mediated cell death through PAK1 suppression. Our results strongly suggest that loss of Smad4 renders the resistance to serum-deprivation-induced cell death, which is the TGF-β-independent tumor suppressive role of Smad4.