Yoshihisa Kadota

Clinical and functional significance of WHO classification on human thymic epithelial neoplasms: a study of 146 consecutive tumors.

We examined the clinical and functional significance of histologic classification of thymic epithelial neoplasms proposed by the World Health Organization (WHO), based on an analysis of 146 consecutive tumors derived from 141 patients and 47 normal thymuses derived from children ranging in age from 1 to 9 years. Invasive tumors were seen in 12.5%, 38.6%, 40.0%, 69.4%, 80.0%, and 100% of type A, AB, B1, B2, B3, and C primary tumors, respectively. All of six recurrent or metastatic lesions were type B2 tumors. Myasthenia gravis was associated in 0%, 6.8%, 40.0%, 55.6%, 10.0%, and 0% in patients with type A, AB, B1, B2, B3, and C tumors, respectively. The average number (×106) of tumor-associated CD4+CD8+ cells present in 1 g of tumor tissue was 1.5, 391.1, 1041.7, 333.9, 24.5, and 0.2 in type A, AB, B1, B2, B3, and C, respectively, and it was 1168.2 in the normal thymuses. Thus, type B1 tumor retained the function to induce CD4+CD8+ double-positive cells at a level comparable to that of the normal thymic cortical epithelial cells, followed by type AB and type B2 tumors. Type A and B3 tumors had this function at a barely detectable level, and type C tumor was nonfunctional. WHO histologic classification was shown to reflect the clinical features and the T-cell-inducing function of thymic epithelial tumors.

Epithelial to Mesenchymal Transition Is a Determinant of Sensitivity to Chemoradiotherapy in Non-Small Cell Lung Cancer

BACKGROUND The epithelial to mesenchymal transition (EMT) is a fundamental biological process during which epithelial cells change to a mesenchymal phenotype; it has a profound impact on cancer progression. The purpose of this study was to clarify the role of EMT in the sensitivity of non-small cell lung cancer (NSCLC) to chemoradiotherapy (CRT). METHODS We evaluated the correlation between EMT and sensitivity to chemotherapy or radiotherapy using NSCLC cells induced to undergo EMT with epidermal growth factor or transforming growth factor-β1. Immunohistochemistry was used to examine the expression of EMT markers, E-cadherin, cytokeratin, N-cadherin, and vimentin in 50 tumor specimens obtained from patients with NSCLC both before and after CRT. RESULTS The EMT resulted in increased malignant potential and reduced sensitivity to cisplatin and paclitaxel in NSCLC cells. Furthermore, chronic exposure to cisplatin, paclitaxel, or radiation altered the cells into therapy-resistant sub-lines that showed phenotypic changes such as a spindle-cell shape and increased EMT marker expression. Also, decreased expression of epithelial markers and upregulation of mesenchymal markers were detected in surgically resected specimens after CRT compared with biopsy specimens obtained before treatment. The disease-free survival rate of patients with EMT marker-positive tumors was significantly lower than that of those with EMT marker-negative tumors. CONCLUSIONS The EMT marker expression was detected in NSCLC tumors after CRT, indicating that EMT changes are associated with insensitivity to CRT. New therapeutic combinations using EMT-signaling inhibitors may be needed to circumvent the resistance of some types of cancer to CRT.

Immunological function of thymoma and pathogenesis of paraneoplastic myasthenia gravis.

Thymoma and thymic carcinoma are the representative tumors arising from the thymic epithelium. Thymoma is well known for association with autoimmune diseases including myasthenia gravis, suggesting its biological activity. Herein, recent progress in research of thymoma is reviewed with reference to its immunological function. Myasthenia gravis is frequently associated with WHO type B1 and B2 thymomas. These types of thymomas hold a significant number of CD4+CD8+ double-positive T cells, and at the same time, the neoplastic epithelial cells express HLA-DR molecules at a slightly reduced level compared with the normal thymus. The impaired expression of HLA-DR molecules in neoplastic epithelial cells of thymomas possibly affects positive selection of CD4+CD8− single-positive T cells and may result in alteration of its repertoire. The function of thymoma neoplastic cells as the cortical epithelium of the thymus and the morphological resemblance of thymomas to the cortex suggest that thymoma is of cortical epithelial origin; this might imply that thymoma lacks the functional medulla where professional antigenpresenting cells are engaged in negative selection. These findings suggest that thymoma generates autoreactive T cells causing autoimmunity. Further investigation on immunological function of thymoma is supposed to elucidate the pathogenesis of thymoma-related autoimmunity and the high affinity of thymoma with myasthenia gravis. In addition, studying the biology of thymoma is also expected to contribute to further understanding of T-cell development and immunological tolerance in the human, because thymoma can be considered an acquired thymus.

Clinical and pathological aspects of thymic epithelial tumors

A histological classification of thymic epithelial tumors was presented by the World Health Organization (WHO) in 1999 and again in 2004 following slight modifications, in which thymic epithelial tumors were categorized as thymomas and thymic carcinomas. Whereas thymoma is defined as an organotypic (thymuslike) tumor, thymic carcinoma is a malignant epithelial neoplasm with a morphology similar to that of malignant neoplasms arising from other organs. Herein, the recent progress in research of thymic epithelial tumors is reviewed with reference to the WHO histological classification system, with the focus on thymomas. Thymomas are classified into five types—A, AB, B1, B2, B3—according to the shape and atypia of their epithelial cells as well as the abundance of lymphocytes. The invasiveness, prognosis, and genetic imbalance of thymomas have been shown to be related to this classification system. Myasthenia gravis is frequently associated with types B1 and B2. The WHO histological classification of thymomas is not only useful for treatment but reflects their biological characteristics, including genetic alterations. Advances are expected in future studies of thymomas from the standpoint of their clinical, pathological, and biological aspects.

Altered T cell development in human thymoma is related to impairment of MHC class II transactivator expression induced by interferon-gamma (IFN-γ)

Thymoma is known to contain CD4+CD8+ T cells, indicating that neoplastic epithelial cells of thymoma have a function as thymic cortical epithelium. However, it has been shown that there is an impairment of CD4+ T cell development in thymoma and that IFN‐γ‐induced HLA‐DR expression on cultured thymic epithelial cells (TEC) derived from thymoma is decreased when compared with the normal thymus. MHC class II transactivator (CIITA) is known to play a critical role in IFN‐γ‐induced MHC II expression. In this study, we attempted to elucidate whether CIITA is responsible for the impaired up‐regulation of MHC II molecules in response to IFN‐γ in thymoma TEC. A quantitative reverse transriptase‐polymerase chain reaction examination revealed that the induced level of CIITA was significantly lower in thymoma TEC than in normal TEC. The induced levels of invariant chain (Ii) and HLA‐DR in thymoma TEC were correlated with CIITA expression. The proportion of CD3+ cells in the CD4+CD8− subset in thymoma was also correlated with CIITA expression. A gel mobility shift assay however, revealed translocation of STAT1 to the nucleus in thymoma as well as normal TEC. Intercellular adhesion molecule‐1 was up‐regulated in the thymoma TEC to a level similar to normal TEC in response to IFN‐γ. These results indicate that impaired up‐regulation of HLA‐DR in response to IFN‐γ results from insufficient induction of CIITA, but not from the signal from IFN‐γ receptor to the nucleus. The abnormal regulation of HLA‐DR expression caused by impaired induction of CIITA may affect CD4+ T cell development in thymoma.

Local IL-17 production and a decrease in peripheral blood regulatory T cells in an animal model of bronchiolitis obliterans.

Background. Recently, it has been reported that Th17 contributes to allograft rejection after transplantation. We investigated the alteration of Th17 and regulatory T cells (Treg) distribution in an animal model of bronchiolitis obliterans following ectopic tracheal transplantation model. Methods. Tracheal grafts from B6 mice transplanted into subcutaneous sites of C3H mice. Allografts were histologically evaluated, and expressions of CD4, CD8, CD25, CD28, CD127, CD152 and Foxp3, and intracellular interleukin (IL)-4, -6, -17, and interferon-&ggr;, in peripheral blood lymphocytes were analyzed. Tracheal graft IL-6 and -17 mRNA expression was assessed using a quantitative reverse-transcriptase polymerase chain reaction. All the data in allogenic transplantation was compared with those in isograft controls. In addition, the effect of IL-6 neutralization on the allograft was evaluated with histopathology and the IL-17 mRNA expression. Results. Treg was significantly lower in peripheral blood of allogenic mice, whereas no significant difference in Th17 in the CD4+ T-cell population was observed after allogenic or isogenic transplantation. Locoregional histologic examination revealed the presence of IL-6-producing lymphocytes and endothelium in the allograft, and the luminal obliteration by fibroblast proliferation. Both IL-6 and IL-17 mRNA levels were elevated in the allograft. Severity of tracheal obliteration and IL-17 mRNA level was significantly suppressed in the IL-6 neutralized allografts. Conclusions. After allograft in a mouse bronchiolitis obliterans model, IL-17 production increases locally without an alteration in peripheral blood Th17 cells, whereas peripheral Tregs decreases. Th17 cells, which can be regulated by IL-6 stimulation, may play a role in posttransplantation rejection of the allograft.

Clinicopathologic factors influencing postoperative prognosis in patients with small-sized adenocarcinoma of the lung.

OBJECTIVE Recent technologic developments in computed tomography have increased the incidence of surgical intervention for small-sized lung cancer. Although indications of a sublobar resection for early disease have been discussed, we occasionally encounter locally advanced small-sized lung cancer with node metastasis. The present study aimed to clarify the histopathologic factors influencing nodal involvement and prognosis of such patients. METHODS We studied 97 patients who underwent complete resection for an adenocarcinoma of 2 cm or less in diameter. Lymph node metastasis and necrosis were microscopically evaluated, whereas immunohistochemical studies were also performed with Ki-67 and D2-40 for proliferation activity and lymphatic invasion, respectively. In addition, carcinoembryonic antigen expression in the tumor and its level in serum were investigated. Survival analysis was then conducted by using these clinicopathologic factors. RESULTS The 5-year disease-free survival rate was 90%. Nodal involvement was significantly frequent in patients with tumors showing microscopic necrosis, a Ki-67 labeling index of greater than 5%, and an increased serum carcinoembryonic antigen level. Furthermore, 5-year disease-free survival was worse in patients with lesions showing microscopic necrosis (68%), a Ki-67 labeling index of greater than 5% (76%), and lymphatic invasion detected with D2-40 staining (77%). Multivariate analysis identified lymphatic invasion detected with D2-40 to be an independent predictor for postoperative recurrence. CONCLUSIONS These results indicate that microscopic necrosis, Ki-67 labeling index, and serum carcinoembryonic antigen level are predictors of nodal involvement. Careful postoperative follow-up examinations for recurrence are required for patients with tumors that show microscopic necrosis, high Ki-67 labeling index, and lymphatic invasion, even in those with stage IA disease.

The immunologic role of thymectomy in the treatment of myasthenia gravis: implication of thymus-associated B-lymphocyte subset in reduction of the anti-acetylcholine receptor antibody titer

BACKGROUND AND PURPOSE Thymectomy is generally accepted as the major option of treatment for myasthenia gravis. To elucidate the biological role of thymectomy in the treatment of myasthenia gravis, the immunologic characteristics of the thymus was studied in association with the postoperative kinetics of the anti-acetylcholine receptor antibody titer. MATERIALS AND METHODS Thirty-four patients with nonthymomatous myasthenia gravis who had positive anti-acetylcholine receptor antibody titer and undergoing extended thymectomy were subjected to the study. Reduction of anti-acetylcholine receptor antibody titer was evaluated in terms of the proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy to that before the operation. The numbers of B lymphocytes (CD19(+) cells) and the germinal center B lymphocytes (CD19(+)CD38(high) cells) present in 1 g of the thymic tissue were calculated by flow cytometry. RESULTS The proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy ranged from 27.5% to 150%. The numbers of B lymphocytes and the germinal center B lymphocytes in 1 g of the thymic tissue ranged from 0.19 x 10(6)/g to 162.8 x 10(6)/g and from 0.09 x 10(6)/g to 33.4 x 10(6)/g, respectively. The proportion of anti-acetylcholine receptor antibody titer at 1 year after thymectomy had a significant inverted correlation with the number of B lymphocytes (P =.002) as well as that of the germinal center B lymphocytes (P =.007). CONCLUSION Effectiveness of thymectomy was dependent on predominance of B lymphocytes and the germinal center B lymphocytes in the thymus, suggesting that one of the biological roles of thymectomy in the treatment of myasthenia gravis is removing the thymus-associated germinal centers.

Clinical outcome of resected solid-type small-sized c-stage IA non-small cell lung cancer.

BACKGROUND The chances of pulmonary resection for small-sized lung cancer have increased because of the development of thin-slice computed tomography (CT). Though sublobar resection could be indicated for ground glass opacity (GGO)-dominant adenocarcinoma with low-grade behaviour, the malignant potential of solid-type, small-sized lung cancer has not been sufficiently assessed. We aimed to address the clinical outcomes of resected solid-type c-stage IA non-small cell lung cancer (NSCLC) smaller than 2 cm. METHODS A retrospective observational study involving 118 patients who had undergone a complete resection for lung cancer smaller than 2 cm with solid component more than 50% on CT was conducted, and their postoperative survival and recurrence pattern were analysed. RESULTS Thirty-five patients with solid component-dominant lesion (SCDL) and 83 patients with pure solid lesion (PSL) without GGO were enrolled. Lymph node involvement was found in 15 patients with PSL (18%). The 5-year disease-free survival (DFS) was 100% in SDCL patients and 83% in PSL patients. Multivariate analysis of PSL patients showed that lymph node metastasis and pleural invasion were independent negative prognostic predictors. The 5-year DFS was 88%, 80% and 46% in p-N0, p-N1 and p-N2 patients, respectively. The 5-year DFS was 33% for patients with pleural invasion, which was significantly worse than that for patients without pleural involvement. Postoperative recurrence was mainly observed as intrathoracic lesions within 3 years. CONCLUSIONS A proportion of solid-type NSCLC has malignant potential, even for tumours smaller than 2 cm. Periodic intrathoracic evaluation is required following complete resection.

Glucocorticoids induce G1 cell cycle arrest in human neoplastic thymic epithelial cells

Purpose Glucocorticoids exert anti-proliferative effects in various cell types and have long been known to induce apoptosis in thymocytes. Although a few reports have described the regression of human thymoma with glucocorticoid therapy, its effects on neoplastic thymic epithelial cells (TECs) have not been reported. In the present study, we investigated glucocorticoid receptor (GR) expression on neoplastic TECs and the effects of glucocorticoids in vitro on the cell cycle progression of tumor cells.Patients and methods Thymoma specimens were obtained during surgery from 21 patients. Three of the specimens with glucocorticoid therapy were examined using the TdT-mediated dUTP-biotin nick-end labeling method. Primary tumor specimens from ten untreated thymomas were examined for GR expression by immunohistochemistry. Isolated neoplastic TECs from the remaining eight untreated thymomas were examined using immunohistochemistry, flow cytometric and cell cycle analysis.Results GR are expressed on neoplastic TECs as well as on non-neoplastic thymocytes in thymomas, regardless of WHO histological classification. Glucocorticoids caused an accumulation of TEC in G0/G1 phase in all cases examined (n=6), and also induced apoptosis in the three with the lowest levels of Bcl-2 expression.Conclusions Our results indicate that neoplastic TECs express GR and that glucocorticoids directly suppress their in vitro proliferation.