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Expression and Its Clinical Significance of Metallothioneins in Primary Laryngeal Squamous Carcinoma

Author: LiLin
Tutor: ZhaoXiaoDong
School: Jilin University
Course: Department of Otolaryngology - Head and Neck Surgery
Keywords: Metallothionein Laryngeal squamous cell carcinoma Immunohistochemical staining
CLC: R739.65
Type: Master's thesis
Year: 2005
Downloads: 27
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Abstract

Background Metallothioneins (MTs) are a family of the low molecular mass proteins characterized by a high cysteine content and high binding capacity of transition metals, free oxidants and some of the products of the cell. They are involved in the progress of the organic development and play a significant role in the development in the tumorgenesis. Some reports suggest that the level of MT expression changed in varieties of tumors, such as lung cancer nasopharyngeal carcinomas and etc, and implied that MT may contribute to the growth of the tumor, influence the programme death, involve in angiogenesis, and aggravate the injury originated from free oxidants and the reaction related. But MTs expression represents in the laryngeal squamous carcinoma has not been reported domestically, our group analyzed MTs expression and explore its significance in clinic work. Object To study the correlation of the metallothioneins (MTs) expression with clinicopathology in laryngeal squamous carcinomas. Method : Tissue samples: tumor tissues were obtained from 50 patients (33 males, 17 females) who underwent laryngeal squamous carcinoma surgery, ranged from 18 to 70years, the median age of the patients was 43.5. In addition we collected laryngeal biopsy from 10 patients (7 males, 3 females) without any laryngeal diseases. Formalin-fixed tissues were stained with H&E for histological evaluation. For the histological tumor typing, we used Lauren’s classification; tumor stage was determined according to the TNM classification. Immunohistochemistry The presence of MTs was assessed used formalin-fixed, paraffin-embeded laryngeal tissue section. Sections (4um) were deparaffinized in graded alcohol. After rising with Tris bulffen, the sections were incubated with anti-MT monoclonal. The MT antibody (Beijing Zhongshang Corp) is a monoclonal mouse antibody derived the ascites of immunized mice. Detection of the bound primary antibody was performed using the avidin-biotin-complex method (vestastain SABC kit bought from Bejing Zhongshang Corp). All of the immunohistochemical studies were performed a number of negative and positive controls. As positive controls observed samples provided was shown to expressed abundant MT by immunohistochemistry used in our immunohistochemical analysis. As negative control none staining was shown. Furthermore, to ensure the specificity of immunostaining we preformed immunohistochemistry using consecutive sections. In the absence of the primary antibody and with PBC (preimmune serum). In all of these cases, no immunnoataining was detected (not shown).H&E and immunohistochemistry datas were reviewed by an experienced pathologist who was blind to the clinical data of the patients. The number of positive cell was counted, and immunoreactivity was graded as absent, low (<50%), strong (>50%). Results: 1. MTs immunoreactivity was observed in 38/50 cancer tissues. Inmmunoreactivity was present in the cytoplasm of the carcinoma cells, while none was found in the control cases. 2. MTs were observed diffused or massed in the locus, while none was found in the control cases. 3. The expression of MT was related to histological grades and lymphnodes metastasis and clinical classification of the carcinoma (p<0.05). It can be concluded that distinct higher positive rate in the low differentiated cases than in the high ones. The difference was also observed between the Ⅰ+Ⅱphase and Ⅲ+Ⅳphase, the trend of MTs expression was improved according to the clinical grade(p<0.05). Positive rate was also higher in the tumor with lymphnodes metastasis than the ones without lymphnodes metastasis(p<0.05). Discussion : Metallothioneins have received their designation from their prominent metal and sulfur content which, varying with metal species present, together may contribute to over 20% of their weight. All cysteins occur in the reduced form and are coordinated to the metal ions through mercaptide bonds, giving rise to spectroscopicfeatures characteristic of metal-thiolate cluster. The most conspicuous biological feature of the MTs is their inducibility by varies of agents and conditions. That is, MTs are greatly enchanced by certain hormone, cytokines, growth factors, tumor promoters and many other chemicals, several fold accretion of MTs is also observed in cultured cells in the transition from S to G phase[1]. Uncontrolled development, falling in the programme death system, angiogenesis are now concerned as the main factors in the development of the tumorgenesis. Latest research indicates: many kinds of malignant tumor, such as head and neck, ovarian neck, small cell lung cancer, and etc represent the high expression of MT protein and its mRNA. Hishikawa[2] and his colleagues reported the strong positive relation between MT and proliferative nucleus antigen, implied that MT maybe improve the carcinogenesis. Some researchers believe that the location of the MTs is dependent on the stage of the cell cycle, according to research of the active expression of MTs in the human bladder cancer[3]. The overexpression of MTs in gastric cancer and the expression of MTs in intestinal metaplasia and dysplasia as well as the expression of MTs in the gastic mucosa of first-degree relatives of patients with gastric cancer point to a role for MTs in early process of malignant transformation of the gastric mucosa[4]. Regulation of znic by MTs influences the prolifertive capability of the tumor, the whole zinc concentration is the determined factor to the growth speed. There is abundant znic in the nucleus which regulate synthesis of DNA and

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