Gene expression profiling reveals biological pathways responsible for phenotypic heterogeneity between UK and Sri Lankan OSCC. Homo sapiens

Background: Oral squamous cell carcinoma (OSCC) is a major world health problem with over 400,000 new cases diagnosed annually. Despite advances in surgery and chemo-radiotherapy, the 5 year survival has remained roughly constant at approximately 50% for several decades. The disease is characterized by both clinical and genetic heterogeneity, so elucidating the molecular basis of this heterogeneity would have significant clinical implications. It is well recognized that OSCCs from Asia that are associated with betel quid chewing are phenotypically distinct from those from the West that are predominantly caused by smoking/drinking, but the genetic basis of these differences are largely unknown. The aim of this study is to examine the most related genetic factors, carcinogenic related pathways, and molecular processes that might be responsible for the phenotypic heterogeneity of OSCC between UK and Sri Lankan population groups. Methods: We have compared the gene expression profiles of OSCCs and normal oral mucosal tissues from both Sri Lankan and UK individuals using Affymetrix gene expression arrays. Results: The gene expression profiles of UK and Sri Lankan OSCC are similar in many respects to other oral cancer expression profiles reported in the literature and were mainly similar to each other. However, genes involved in tumor invasion, metastasis and recurrence were more obviously associated with UK tumors as opposed to those from Sri Lanka. Interestingly, Ingenuity Pathway Analysis (IPA) revealed a highly activated cell-mediated immune response in both Sri Lankan normal and tumor samples relative to UK cohorts, which may, in part, explain the less aggressive behavior of these betel quid-induced OSCCs. Conclusion: The development of OSCCs in both UK and Sri Lankan populations appears largely mediated by similar biological pathways despite the differences related to race, ethnicity, lifestyle, and/or exposure to environmental carcinogens. However, IPA revealed a highly activated “Cell-mediated Immune Response” in Sri Lankan normal and tumor samples relative to UK cohorts. It seems likely, therefore, that any future attempts to personalize treatment for OSCC patients will need to be different in Western and Asian countries to reflect differences in gene expression and the immune status of the patients. Overall design: All biopsy specimens of OSCC and normal oral mucosa were harvested with appropriate ethical approval and informed consent of individual patients (LREC 0769). Identical protocols for tissue collection and processing were used in both countries. OSCC samples were obtained from sequential incident cases treated by a single consultant surgeon from 2001 to 2004 at University Hospital of Birmingham, NHS Foundation Trust, Birmingham, UK, and Kandy General Hospital, Kandy, Sri Lanka. A total of 21 UK and 27 Sri Lankan samples yielded RNA of sufficient quality and quantity for microarray analysis. In addition, 8 normal oral mucosa specimens (five samples from UK & three samples from Sri Lankan population) were also profiled. All normal samples were from non-smokers, who did not chew betel quid and did not consume in excess of the national recommended weekly gender allowance of alcohol. Normal samples were taken from individuals with no history of cancer and had no first degree relatives with a history of cancer.

背景：口腔鳞状细胞癌（Oral squamous cell carcinoma, OSCC）是全球性重大公共卫生问题，每年新增确诊病例超40万例。尽管手术与放化疗技术已取得进展，但数十年来患者的5年生存率始终维持在约50%的水平，未有明显提升。该疾病兼具临床与遗传异质性，阐明此类异质性的分子机制将具有重要的临床价值。众所周知，亚洲地区与槟榔咀嚼相关的口腔鳞状细胞癌，在表型上与西方以吸烟/饮酒为主要诱因的病例存在显著差异，但此类差异的遗传基础目前仍不明确。本研究旨在探究英国与斯里兰卡人群口腔鳞状细胞癌表型异质性相关的关键遗传因素、致癌相关通路及分子进程。

方法：本研究采用Affymetrix基因表达芯片，对比分析了斯里兰卡与英国人群的口腔鳞状细胞癌组织及正常口腔黏膜组织的基因表达谱。

结果：英国与斯里兰卡人群的口腔鳞状细胞癌基因表达谱，在诸多方面与文献报道的其他口腔癌表达谱具有相似性，且二者之间整体表达模式也较为接近。但与斯里兰卡病例相比，英国肿瘤样本中与肿瘤侵袭、转移及复发相关的基因表达更为显著。值得注意的是，Ingenuity通路分析（Ingenuity Pathway Analysis, IPA）显示，相较于英国队列，斯里兰卡正常组织与肿瘤样本中均呈现出高度激活的细胞介导免疫应答，这或许可以部分解释槟榔嚼块诱导的口腔鳞状细胞癌侵袭性较低的特征。

结论：尽管英国与斯里兰卡人群在种族、民族、生活方式及环境致癌物暴露方面存在差异，但二者口腔鳞状细胞癌的发生发展整体上由相似的生物学通路所介导。但IPA分析显示，相较于英国队列，斯里兰卡人群的正常与肿瘤样本中"细胞介导免疫应答"通路呈现高度激活。因此，未来针对口腔鳞状细胞癌患者的个体化治疗方案，或许需要根据西方国家与亚洲国家的差异进行调整，以适配不同人群的基因表达特征与免疫状态。

实验整体设计：本研究中所有口腔鳞状细胞癌及正常口腔黏膜活检样本的采集，均获得了伦理委员会批准，并获得了患者的书面知情同意（伦理批件号：LREC 0769）。两国均采用统一的组织采集与处理流程。口腔鳞状细胞癌样本采集自2001年至2004年间，分别在英国伯明翰NHS基金会信托基金伯明翰大学医院以及斯里兰卡康提康提总医院，由同一名顾问外科医生接诊的连续新发患者病例。最终共有21份英国样本与27份斯里兰卡样本的RNA，其质量与浓度均满足芯片分析要求。此外，本研究还纳入了8份正常口腔黏膜样本（其中5份来自英国人群，3份来自斯里兰卡人群）进行表达谱分析。所有正常黏膜样本均来自无吸烟史、无槟榔咀嚼习惯，且酒精摄入量未超过本国推荐的性别特异性每周限量的受试者，且所有受试者均无癌症病史，其一级亲属也无癌症病史。