Mallick S, Patil R, Gyanchandani R, Pawar S, Palve V, Kannan S, Pathak K A, Choudhary M, Teni T R
Advanced Centre for Treatment, Research and Education in Cancer, Kharghar, Navi Mumbai-410210, India.
J Pathol. 2009 Feb;217(3):398-407. doi: 10.1002/path.2459.
Expression of Bcl-2 family proteins in tumours can modulate apoptosis, influencing tumour behaviour and treatment. To investigate their role in oral tumourigenesis, nine Bcl-2 family transcripts were examined in three oral cell lines and 25 oral tumours, using ribonuclease protection assay. Since Mcl-1 mRNA was elevated in these samples, Mcl-1 splice variants were assessed by RT-PCR and Mcl-1 protein was studied in normal, premalignant and malignant oral tissues and cell lines, by immunohistochemistry and/or immunoblotting. The cell lines exhibited significantly higher levels of 7/9 Bcl-2 family transcripts as compared to those in normal tongue, and significantly higher (p=0.030, p=0.004) anti-apoptotic versus pro-apoptotic transcripts. Elevated Mcl-1 mRNA was observed in 11/25 (44%) tumours as compared to normal tissues with a five- to ten-fold higher expression of full-length anti-apoptotic Mcl-1 transcript versus the pro-apoptotic short isoform. Strong cytoplasmic Mcl-1 immunoreactivity was detected predominantly in differentiated epithelia in 27/33 (82%) oral tumours, 18/20 (90%) leukoplakia, 25/30 (83%) submucous fibrosis and 3/3 oral cell lines, with weak staining in 8/15 (53%) normal mucosa samples. Mcl-1 positivity in malignant and premalignant tissues was comparable but significantly higher (p<0.01) than that in normal mucosa. The expression of bcl-2 family genes, including Mcl-1 in tumours, did not correlate significantly with clinicopathological parameters. This is the first report delineating the in vivo expression patterns of Mcl-1 protein and Mcl-1 transcripts in oral cancers and premalignant lesions. The observed imbalance between expression of anti-apoptotic and pro-apoptotic Bcl-2 family genes may promote survival in the oral cell lines. Since the majority of oral tumours associated with tobacco-chewing evolve from premalignant lesions, the sustained expression of full-length anti-apoptotic Mcl-1 protein in these tissues suggests an important role for Mcl-1, early in oral cancer pathogenesis in protecting cells from apoptosis via neutralization of pro-apoptotic members and could be a potential therapeutic target for oral cancers.
Bcl-2家族蛋白在肿瘤中的表达可调节细胞凋亡，影响肿瘤行为及治疗效果。为研究其在口腔肿瘤发生中的作用，采用核糖核酸酶保护分析法，检测了三种口腔细胞系和25例口腔肿瘤中9种Bcl-2家族转录本。由于这些样本中Mcl-1 mRNA水平升高，通过逆转录聚合酶链反应评估了Mcl-1剪接变体，并通过免疫组织化学和/或免疫印迹法，研究了正常、癌前和恶性口腔组织及细胞系中的Mcl-1蛋白。与正常舌组织相比，细胞系中7/9种Bcl-2家族转录本水平显著更高，抗凋亡转录本与促凋亡转录本相比也显著更高（p = 0.030，p = 0.004）。与正常组织相比，在11/25（44%）的肿瘤中观察到Mcl-1 mRNA升高，全长抗凋亡Mcl-1转录本的表达比促凋亡短异构体高5至10倍。在27/33（82%）的口腔肿瘤、18/20（90%）的白斑、25/30（83%）的黏膜下纤维化和3/3的口腔细胞系中，主要在分化上皮中检测到强细胞质Mcl-1免疫反应性，在8/15（53%）的正常黏膜样本中染色较弱。恶性和癌前组织中的Mcl-1阳性率相当，但显著高于正常黏膜（p < 0.01）。包括肿瘤中Mcl-1在内的bcl-2家族基因表达与临床病理参数无显著相关性。这是首篇描述口腔癌及癌前病变中Mcl-1蛋白和Mcl-1转录本体内表达模式的报告。观察到的抗凋亡和促凋亡Bcl-2家族基因表达失衡可能促进口腔细胞系存活。由于大多数与嚼烟相关的口腔肿瘤由癌前病变发展而来，这些组织中全长抗凋亡Mcl-1蛋白的持续表达表明Mcl-1在口腔癌发病早期通过中和促凋亡成员保护细胞免于凋亡方面发挥重要作用，可能是口腔癌的潜在治疗靶点。
