Tervahauta A I, Syrjänen S M, Kallio P J, Syrjänen K J
Department of Pathology, University of Kuopio, Finland.
Anticancer Res. 1992 May-Jun;12(3):1005-11.
The assessment of oncogene expression at cellular level is important in understanding the role of those genes in carcinogenesis. Using in situ hybridization and immunohistochemistry, the expression of oncogenes can be visualized in topographic relation to tissue morphology. In the present study, c-myc overexpression was studied in ten carcinomas of different origin (6 mammary adenocarcinomas, 2 vulvar and 2 bronchial squamous cell carcinomas) by in situ hybridization (ISH) with 35S-labeled RNA probes and by immunohistochemistry (IHC). DNA amplification and transcription of c-myc oncogene were also studied with polymerase chain reaction (PCR) using beta-globin as an intrinsic standard for DNA amplification. The effect of formalin fixation of c-myc expression was simultaneously studied. Half of the tumours (5/10) demonstrated c-myc mRNA overexpression by ISH performed on frozen sections and two of the samples were shown to over-express c-myc protein by IHC. Only two samples fixed in formalin showed positive signals for c-myc mRNA. None of the biopsies showed DNA amplifications either with ISH or PCR. The present results suggest that ISH with RNA probes is a useful method for detecting the transcription of activated oncogenes in malignant tissues, especially when applied on frozen sections. The results also indicate that in some cases, c-myc gene may be adequately transcribed to mRNA but the latter is not translated to the appropriate oncoprotein.
在细胞水平评估癌基因表达对于理解这些基因在致癌过程中的作用至关重要。利用原位杂交和免疫组织化学技术，可以将癌基因的表达与组织形态学的拓扑关系可视化。在本研究中，通过使用35S标记的RNA探针进行原位杂交（ISH）以及免疫组织化学（IHC），对10例不同起源的癌（6例乳腺腺癌、2例外阴癌和2例支气管鳞状细胞癌）中的c-myc过表达进行了研究。还使用聚合酶链反应（PCR），以β-珠蛋白作为DNA扩增的内参标准，研究了c-myc癌基因的DNA扩增和转录情况。同时研究了福尔马林固定对c-myc表达的影响。对冷冻切片进行ISH检测时，一半的肿瘤（5/10）显示c-myc mRNA过表达，并且其中两个样本通过IHC显示c-myc蛋白过表达。仅两个福尔马林固定的样本显示c-myc mRNA呈阳性信号。无论是ISH还是PCR检测，活检样本均未显示DNA扩增。本研究结果表明，使用RNA探针进行ISH是检测恶性组织中活化癌基因转录的一种有用方法，尤其是应用于冷冻切片时。结果还表明，在某些情况下，c-myc基因可能已充分转录为mRNA，但后者并未翻译为相应的癌蛋白。
