Evaluation of PPARγ agonists on rodent endothelial cell proliferation

The PPARγ agonist troglitazone (TG) induced an increased incidence of hemangiosarcomas in mice but was not carcinogenic in rats. In contrast, pioglitazone (PIO) did not induce hemangiosarcomas or any other tumors in mice. We previously demonstrated that TG increased the proliferation of endothelial cells (ECs) in liver and adipose tissue in mice, and acted as a mitogenic stimulant and an inhibitor of apoptosis in vitro in mouse, but not human, ECs. In the present study, we investigated whether TG had any effect on the proliferation of ECs in rats. We also evaluated the in vivo and in vitro effects of PIO on ECs in mice. In rats, TG did not increase the Ki-67 labeling index (LI) of ECs in liver or adipose tissue at doses used in the two-year bioassay, and did not increase hepatocyte proliferation. PIO administered to mice did not increase the Ki-67 LI of hepatocytes or ECs in liver or white adipose tissue, but slightly increased the EC proliferation in brown adipose tissue. PIO was slightly mitogenic on cultured mouse ECs after 3 days of treatment but not after 6 days, and there was no inhibition of apoptosis, in contrast to what was seen with TG. The data support the conclusion that sustained EC proliferation in mice is necessary, for the induction of hemangiosarcomas by TG, and these short-term and long-term effects are not seen with TG in the rat or with PIO in mice, treatments that also are not related to the induction of hemangiosarcomas in two-year bioassays.     

Evaluation of direct and indirect effects of the PPARγ agonist troglitazone on mouse endothelial cell proliferation

Peroxisome proliferator-activated receptor gamma (PPARγ) agonists and PPARγ/α dual agonists are used in the treatment of type 2 diabetes mellitus and hyperlipidemias. In carcinogenicity studies, some of these agonists induced hemangiomas/hemangiosarcomas in mice, but not in rats. We hypothesized that increased endothelial cell (EC) proliferation may be involved in the mechanism of PPAR agonist-induced vascular tumors in mice. We previously showed that the sarcomagenic PPARγ agonist troglitazone (TG) increased EC proliferation in brown and white adipose tissue and liver in mice at sarcomagenic doses (400 and 800 mg/kg) after four weeks of treatment. In vitro, TG had a mitogenic effect on mouse microvascular mouse ECs by increasing cell proliferation and survival. The current studies showed that treatment of mouse ECs in vitro induced alterations in proliferation pathway gene expression, especially the expression of insulin-like growth factor-1, but had no effect on mouse oxidative stress pathways. In vivo, treatment with vitamin E did not inhibit TG-induced EC proliferation in liver and adipose tissue. In addition, no hypoxic effect was detected in adipose tissue of TG-treated mice; however, TG had a minor effect on hepatocellular hypoxia. These results provide additional evidence supporting a direct mitogenic effect in the mode of action of TG-induced hemangiosarcomas in mice.     

Epstein-Barr Virus nuclear antigen 1 (EBNA1) confers resistance to apoptosis in EBV-positive B-lymphoma cells through up-regulation of survivin

Resistance to apoptosis is an important component of the overall mechanism which drives the tumorigenic process. EBV is a ubiquitous human gamma-herpesvirus which preferentially establishes latent infection in viral infected B-lymphocytes. EBNA1 is typically expressed in most forms of EBV-positive malignancies and is important for replication of the latent episome in concert with replication of the host cells. Here, we investigate the effects of EBNA1 on survivin up-regulation in EBV-infected human B-lymphoma cells. We present evidence which demonstrates that EBNA1 forms a complex with Sp1 or Sp1-like proteins bound to their cis-element at the survivin promoter. This enhances the activity of the complex and up-regulates survivin. Knockdown of survivin and EBNA1 showed enhanced apoptosis in infected cells and thus supports a role for EBNA1 in suppressing apoptosis in EBV-infected cells. Here, we suggest that EBV encoded EBNA1 can contribute to the oncogenic process by up-regulating the apoptosis suppressor protein, survivin in EBV-associated B-lymphoma cells.     

A Prospective Study of Cyclosporine A Treatment of Patients with Low-Risk Myelodysplastic Syndrome: Presence of CD55−CD59− Blood Cells Predicts Platelet Response

Although immunosuppressive therapy using antithymocyte globulin or cyclosporine A (CSA) is effective in selected patients with low-risk myelodysplastic syndrome, the response rates reported so far are inconsistent, and the indication of immunosuppressive therapy for myelodysplastic syndrome has not been clearly defined. We treated 20 myelodysplastic syndrome patients (17 refractory anemia cases [RA], 2 RA with excess blasts, and one RA with ringed sideroblasts) with 4 mg/kg per day of CSA for 24 weeks. Among the 19 patients evaluated, 10 showed hematologic improvement; 8 patients showed an erythroid response, 6 showed a platelet response, and one showed a neutrophil response. Most patients with hematologic improvement continued CSA thereafter, and the progressive response was observed until the latest follow-up (median, 30 months). Most toxicities associated with CSA usage were manageable, and no patient had developed acute leukemia up to this point. Short duration of illness, refractory anemia with minimal dysplasia determined by bone marrow morphology, and the presence of paroxysmal nocturnal hemoglobinuria-type cells were significantly associated with the platelet response. A minority of RA patients who did not possess such predictive variables achieved an isolated erythroid response. In conclusion, CSA may be a therapeutic option for patients with RA who do not have adverse prognostic factors.     

Long-term Results after Dissection of Positive Thoracic Lymph Nodes in Patients with Esophageal Squamous Cell Carcinoma

Background Although thoracic lymph node metastasis in patients with thoracic esophageal squamous cell carcinoma (SCC) has been reported to be a negative risk factor for long-term survival, only a few studies have evaluated the clinicopathologic difference between the impact of metastasis to the paraesophageal lymph nodes and to the nonparaesophageal lymph nodes. The purpose of this study was to evaluate surgical outcome after the clearance of metastatic thoracic lymph nodes. Methods Retrospectively reviewed were 164 consecutive patients with thoracic esophageal SCC who had not had preoperative treatment and underwent surgery from 1980 to 2005 and were found to have thoracic lymph node metastases. Of these patients, 83 underwent surgery from 1980 to 1994 and 81 from 1995 to 2005. Univariate and multivariate analyses were performed to evaluate the impact of nonparaesophageal lymph node metastasis on survival. Results Univariate analysis revealed that T3/T4 tumors and the presence of nonparaesophageal node metastases were associated with only a 20% overall five-year survival rate. The overall five-year survival for the most recent period was significantly better than for the former period (42% vs. 13%, p < 0.01). Based on a multivariate analysis of prognostic impact of each nonparaesophageal node, the presence of metastatic subcarinal and/or posterior mediastinal nodes was an independent risk factor for reduced survival. Conclusion Surgical outcome for patients with thoracic esophageal cancer and metastatic thoracic lymph nodes has improved during the last 25 years. Although postoperative chemotherapy might improve survival, the presence of T3/T4 tumors and/or metastatic nonparaesophageal nodes were unfavorable factors for survival.     

Inhibition of tumor growth and metastasis by depletion of vesicular sorting protein Hrs: its regulatory role on E-cadherin and beta-catenin

Abnormally high signals from receptor tyrosine kinases (RTK) are associated with carcinogenesis, and impaired deactivation of RTKs may also be a mechanism in cancer. Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is one of the master regulators that sort activated receptors toward lysosomes and shut down their signals. Hrs contains a ubiquitin-interacting motif and is involved in the endosomal sorting of monoubiquitinated membrane proteins, such as growth factor receptor and E-cadherin. Here, we investigated the role of Hrs in determining the malignancy of cancer cells and discovered that the targeted disruption of Hrs by small interfering RNA effectively attenuated the proliferation, anchorage-independent growth, tumorigenesis, and metastatic potential of HeLa cells in vitro and in vivo. The restoration of Hrs expression increased cell proliferation and anchorage-independent growth in a mouse embryonic fibroblast line established from a Hrs knockout mouse. Further analysis revealed that Hrs depletion was associated with the up-regulation of E-cadherin and reduced beta-catenin signaling. The aberrant accumulation of E-cadherin most likely resulted from impaired E-cadherin degradation in lysosomes. These results suggest that Hrs may play a critical role in determining the malignancy of cancer cells by regulating the degradation of E-cadherin.     

Hepatitis C virus infection in a Japanese leprosy sanatorium for the past 67 years

Oku‐Komyo‐En is one of the national leprosy sanatoria, located on a small island in Setouchi city, Okayama prefecture of Japan since 1938. Since autopsies were carried out routinely on almost all patients who had died in the sanatorium up to 1980, approximately 1,000 formalin‐fixed autopsy tissue samples were available for analysis. When these samples were reviewed, the pathological data indicated a sharp rise in the death rate caused by cirrhosis of the liver and hepatocellular carcinoma (HCC) since 1960 and 1970, respectively. Hepatitis C virus (HCV) infection is a common cause of HCC in Japan. The presence of HCV RNA was demonstrated in paraffin sections prepared from the autopsied liver tissue fixed in formalin for a prolonged period of time, by employing nested RT‐PCR using type‐specific primers. The data showed that HCV RNA was detectable in samples of the liver archived as early as 1940, representing the liver tissues kept in formalin for up to 67 years. HCV genotypes 1b and 2a were found by RT‐PCR at 85.7% and 14.3%, respectively, in patients with leprosy. J. Med. Virol. 82:556–561, 2010. © 2010 Wiley‐Liss, Inc.