Expression of manganese superoxide dismutase in patients with breast cancer

Breast cancer has become the second leading cancer among females in Taiwan. Even though the etiology of breast cancer is multifactorial, oxidative stress plays an important role in the carcinogenesis. The purpose of this study was to investigate the expression of manganese superoxide dismutase (MnSOD), one of the major antioxidant enzymes that is involved against oxidative stress, in adjacent cancer-free breast tissues and neoplasm tissues within the same patient. Sixty-five breast cancer patients’ formalin-fixed tissue blocks, including ductal carcinoma in situ (DCIS) tissues, invasive ductal carcinoma (IDC) tissues, and adjacent cancer-free tissues, were evaluated by immunohistochemical stain. Meanwhile, their demographic and clinical information was also collected. The combined scores of MnSOD-positive cell proportion and MnSOD staining intensity were compared for different tissues within the same patient. The results showed that the mean combined scores of MnSOD expression in adjacent cancer-free tissues (6.33), IDC (5.30), and DCIS (3.78) were significantly different when assessed by repeated-measurement analysis of variance (F = 14.17, p < 0.001). Additionally, the results revealed that the distribution of strong MnSOD protein expression was 80.0%, 72.3%, and 52.3% in adjacent cancer-free tissues, IDC, and DCIS, respectively. However, there was no statistically significant relationship between the expression of MnSOD and grades of breast cancer or other clinicopathologic variables. We suggest that the expression of MnSOD in neoplasm tissues, independent of the clinicopathologic characters, plays a critical role in breast cancer biology.

摘要乳癌目前已經位居台灣女性癌症的第二位，根據文獻報導，乳癌雖然有許多的致病因子，然而氧化性傷害在其致癌機轉中扮演重要的角色，因此本研究擬探討生物體中最重要的抗氧化酵素--錳超氧化物歧化酶(Manganese superoxide dismutase; MnSOD)在乳癌組織中之表現。本實驗共收集65位診斷為乳癌病人(年紀51.5±10.7歲)之乳房組織為實驗材料。經由免疫組織化學染色法分析同一病人之乳腺管原位癌(DCIS)、浸潤性乳腺管癌(IDC) 及其鄰近無癌化乳房組織之MnSOD蛋白表現。而MnSOD蛋白表現之綜合分數表示方法乃結合細胞染色定性強度及定量評分價數來呈現。結果顯示：於鄰近之無癌化乳房組織、IDC與DCIS等乳房癌組織之MnSOD蛋白表現之平均綜合分數分別為6.33、 5.30與3.79。以重複測量變異數分析，發現：這些平均值具有統計上的差異(F = 14.17, p < 0.001)。此外，本研究也指出：於同一病人之鄰近無癌化乳房組織、IDC、DCIS等乳房癌組織其MnSOD蛋白之極強免疫染色反應比例分別為80.0%、 72.3% 和 52.3%。然而在本研究中也發現MnSOD蛋白表現之平均綜合分數與其他臨床指標值之間均無統計學上的相關性。綜合以上結果，MnSOD蛋白表現在乳癌致癌過程中可能扮演重要的角色。