microRNA存在肿瘤内异质性

　　

生物通报道：microRNAs (miRNAs) 被认为与乳腺癌的发展和转移有关，并能为人们提供预后信息。利用miRNA方法进行乳腺癌诊断具有广阔的前景。不过，乳腺癌的miRNA表达谱研究往往得出相互矛盾的结果。慕尼黑工业大学的一项新研究指出，乳腺癌miRNA的量和类型差异可能将miRNA诊断引入歧途，该文章发表在Journal of Molecular Diagnostics杂志上。

“个人化医疗是癌症治疗的未来，”研究带头人慕尼黑工业大学的Stefanie Avril博士解释道。“然而，仅仅取一份肿瘤样品进行组织学活检来指导个体治疗可能过于简单，我们需要考虑到肿瘤的异质性。”研究人员在单一肿瘤样本中发现乳腺癌相关miRNA的表达存在显著差异（被称为肿瘤内异质性）。他们提出使用miRNA进行诊断或预后需要对不同肿瘤部位和肿瘤相关淋巴结进行取样。

研究人员收集了16位患者的132份肿瘤样本，这些患者患有原发性侵袭性乳腺癌，并接受了乳房肿瘤或乳房切除手术。研究人员分别从肿瘤中心、肿瘤外周和中间区域取样。如果发生癌转移，研究人员也对淋巴结进行了取样。随后他们分别对这些样品中的四个miRNA（miR-31, miR-335, miR-10b和miR-210）和四个对照基因（let-7a, miR-16, RNU48和RNU44）进行了检测分析。

研究发现同一患者原发乳腺癌肿瘤和淋巴结转移性肿瘤中的miRNA表达存在巨大的差异。这一异质性的程度与不同肿瘤区域间的异质性相似类似于。

为了研究肿瘤内异质性误导实验结果的原因，研究人员对不同患者的miRNA表达差异进行了检测。患者5原发肿瘤部位所有区域的miR31（与癌转移有关）平均表达水平大大低于患者6相应区域的miR31平均表达水平。而患者5单个肿瘤区域样本中miR31表达水平会比患者6的miR31最低水平高。研究人员认为，这一现象可能是miRNA表达谱分析结果出现矛盾的部分原因。

“该研究的优势在于，系统性的对肿瘤8至10个不同区域进行了取样，而此前的研究通常只是分析一个肿瘤切片的不同区域或对同一肿瘤进行核心活检，”Avril博士说“我们的研究显示，要保证miRNA图谱分析在乳腺癌研究中的可靠性就需要对原发性肿瘤的不同部位进行取样，如果发生癌转移还应对肿瘤相关淋巴结进行取样。”

（生物通编辑：叶予）

生物通推荐原文摘要：

Intratumoral Heterogeneity of microRNA Expression in Breast Cancer

Profiling studies have identified specific microRNA (miRNA) signatures in malignant tumors including breast cancer. Our aim was to assess intratumoral heterogeneity in miRNA expression levels within primary breast cancers and between axillary lymph node metastases from the same patient. Specimens of 16 primary breast cancers were sampled in 8-10 distinct locations including the peripheral, intermediate, and central tumor zones, as well as two to five axillary lymph node metastases (n = 9). Total RNA was extracted from 132 paraffin-embedded samples, and the expression of miR-10b, miR-210, miR-31, and miR-335 was assessed as well as the reproducibility of RNA extraction and miRNA analysis by quantitative RT-PCR. Considerable intratumoral heterogeneity existed for all four miRNAs within primary breast cancers (CV 40%). No significant differences within (CV 34%) or between different tumor zones (CV 33%) were found. A similar variation in miRNA expression was observed between corresponding lymph node metastases (mean CV 40%). In comparison, the variation among different patients showed a CV of 80% for primary tumors and 103% for lymph node metastases. Both miRNA extraction procedures and quantitative RT-PCR showed high reproducibility (CV ≤ 2%). Thus, the intratumoral heterogeneity of miRNA expression in breast cancers can lead to significant sampling bias. Assessment of breast cancer miRNA profiles may require sampling at several different tumor locations and of several tumor-involved lymph nodes when deriving miRNA expression profiles of metastases.