MCM5於口腔上皮變異及口腔鱗狀細胞癌中之表現

Abstract

背景 MCM5 (minichromosome maintenance 5)為MCM家族成員之一，在DNA的複製起始、細胞分裂週期的調控扮演重要角色。MCM5同時和細胞生長(proliferation)有關，在人體中如食道、子宮頸、卵巢、皮膚及胃的癌症都有表現量提高的情形。本研究欲探討MCM5蛋白於口腔癌、口腔上皮變異、和正常口腔黏膜中的表現量，以及口腔癌患者中，MCM5表現與各項臨床病理參數以及存活時間的關係。 材料與方法 本研究利用免疫組織化學染色方法，探討MCM5於97例口腔鱗狀細胞癌(OSCC)、80例口腔上皮變異(OED; 31例輕度、29例中度、20例重度)、及20例正常口腔黏膜(NOM)中的表現，並以標記指數(labeling indices, LIs。定義為所有觀察細胞中，陽性染色細胞的百分比)紀錄其染色程度，比較各組間差異。同時利用卡方檢定(chi-square test)、Cox proportional hazard mode以及Kaplan-Meier 存活率方法來分析MCM5的表現與口腔鱗狀細胞癌患者臨床病理參數及存活率之相關性，並試圖尋找影響存活時間的獨立預後因子。 結果 就MCM5平均標記指數而言，正常口腔黏膜為15±6% (最低)、口腔輕度上皮變異為25±10%、中度上皮變異為34±9%、重度上皮變異為43±12%，而口腔癌為61±16% (最高)，從正常口腔黏膜、上皮變異至口腔癌的癌化過程，MCM5表現有隨著變異程度的增加而呈現統計學上有意義增加的情形 ( P < 0.001 )。較高的MCM5表現和較差的腫瘤分化(P = 0.002)、較大的腫瘤大小(P = 0.032)、有淋巴結轉移 ( P = 0.003)、較晚的腫瘤臨床分期(P = 0.002)、較深的侵犯深度(P = 0.0001)、或神經侵犯(P = 0.0047)有統計上有意義相關。各項臨床病理參數在單變數分析中發現，有淋巴結轉移(P = 0.048)、較晚的腫瘤臨床分期(P = 0.031)以及MCM5的標記指數(LI) ≧ 60% (P = 0.0017)患者之存活率較差；然而以Cox proportional hazard regression model做多變數分析之後，只有MCM5的標記指數(LI) ≧ 60% 為影響存活時間的獨立因子(independent factor; P = 0.0049); MCM5標記指數若≧60%，影響病人存活的危險率(hazard ratio)達4.630倍( p= 0.049)。而Kaplan-Meier 存活曲線也顯示若口腔癌病人的MCM5標記指數≧60%，和MCM5標記指數< 60%的組別相比，有較差的累積存活率，統計上達顯著差異(P = 0.0062, log-rank test)。 結論 MCM5表現的增加，從口腔癌前病變時即開始。MCM5在口腔鱗狀細胞癌病人的標記指數，可以推斷口腔癌的病程發展、以及病人的存活率。MCM5表現量較高者，其存活時間較短。因此，MCM5在組織切片中的表現程度，或許可以做為口腔癌的預後指標(prognostic marker)。 關鍵字：MCM5、口腔鱗狀細胞癌、口腔上皮變異、預後。

Background Of the MCM family, MCM5 involves important roles in both initiation of DNA replication and regulation of cell division cycle. MCM5 is also known for its effect on cell proliferation. Recent studies have shown a significantly higher expression of MCM5 in human cancers, such as esophageal, uterine cervical, ovarian, skin, and gastric cancers. This study assessed the expression of MCM5 in specimens of oral squamous cell carcinoma (OSCC), oral epithelial dysplasia (OED), and normal oral mucosa (NOM). We also evaluated the correlation between the expression of MCM5 and clinicopathological parameters of OSCCs or survival of OSCC patients. Material and Methods This study examined the expression of MCM5 in 97 OSCC, 80 OED (31 mild, 29 moderate, and 20 severe OED cases), and 20 NOM specimens by immunohistochemical staining with a MCM5 monoclonal antibody. The labeling indices (LIs, defined as the percentage of positive cells in total cells) in OSCC OED and NOM samples were calculated and compared among groups. The correlations between expression of MCM5 and clinicopathological parameters or the overall survival of OSCC patients were analyzed statistically via chi-square test, Cox proportional hazard regression model, and Kaplan-Meier plots. Results We found that the mean MCM5 LIs increased gradually and significantly from NOM (15 ± 6%), through mild (25 ± 10%), moderate (34 ± 9%), and severe OED (43 ± 12%), to OSCC samples (61 ± 16%, P < 0.001). A significant correlation was found between the higher mean MCM5 LI and OSCCs with higher histological grade (P = 0.002), larger tumor size (P = 0.032), positive lymph node metastasis (P = 0.003), more advanced clinical stage (P = 0.002), deeper invasion depth (P = 0.0001), or perineural invasion (P = 0.0047). Univariate analyses identified positive lymph node metastasis (P = 0.048), advanced clinical stage (P = 0.031), and MCM5 LI ≧ 60% (P = 0.0017) as correlating with poor survival. However, only MCM5 LI ≧ 60% (P = 0.049) was identified as an independent unfavorable prognosis factor by multivariate analyses with Cox proportional hazard regression model. Kaplan-Meier curve showed that OSCC patients with an MCM5 LI ≧ 60% had a significantly poorer cumulative survival than those with an MCM5 LI < 60% (P = 0.0062, log-rank test). Conclusions The increased expression of MCM5 is an early event in oral carcinogenesis. The MCM5 LI in OSCC samples can predict the progression of OSCC and the survival of OSCC patients. Keywords: MCM5, oral squamous cell carcinoma, oral epithelial dysplasia, prognosis