Die Expression tumorkorrelierter mikroRNAs und ihrer potenziellen Ziel-Gene APAF1 und HMGA2 in Lungenkarzinomen und Lymphknotenmetastasen

MiRNAs are single-stranded, non-coding and approximately 22 nucleotide-long RNAs being able to affect almost all cellular processes such as growth, differentiation and apoptosis, by translational inhibition or degradation of their target mRNA. They have been increasingly studied over the last 20 years, as they have been shown in the literature to be valid biomarkers of a wide variety of diseases including cancer. Lung carcinomas are among the most commonly diagnosed malignant neoplasms and account for the most cancer-related deaths worldwide. Despite state-of-the-art therapies, the prognosis of lung cancer is often poor and therefore requires new concepts for early detection, diagnosis and therapy. MiRNAs offer great potential in this regard, as many studies have already shown that numerous miRNAs exhibit an altered expression in lung carcinomas, are involved in carcinogenesis and metastasis, and may correlate with TNM stage and patient prognosis. In the present dissertation, the expression of miRNAs miR-19a, miR-19b, miR-21-1, miR-30-5p, let-7b-5p, and let-7f-5p and their potential targets HMGA2 and APAF1 was investigated in lung carcinoma and lymph node metastasis compared to healthy tissue. Formalin-fixed and paraffin-embedded (FFPE) samples from 31 patients operated at the University Hospital of Marburg between 2000 and 2004 were collected. Twenty-eight lung carcinoma samples, 16 lymph node metastasis samples, 14 healthy lung samples, and 12 healthy lymph node samples were included in the study. After RNA isolation, four pools were created from the samples, which contained all samples in the group in equal amounts. The expression of miRNAs and mRNAs was measured by quantitative real-time reverse transcriptase polymerase chain reaction. The expression of miRNAs in lung carcinoma was compared with their expression in healthy lung tissues. The expression of miRNAs in lymph node metastasis was compared to healthy lung and lymph node tissue. Hsa-miR-19a and hsa-miR-19b did not show significantly altered expression in lung cancer tissues. Instead, they showed a strong downregulation in lymph node metastasis tissues compared to healthy lung and lymph node tissues. The expression of hsa-miR-30a-5p was unchanged in lung carcinoma tissues. Its expression was down regulated in lymph node metastasis tissues compared to healthy lung tissues and up regulated compared to healthy lymph node tissues. Hsa-miR-21-1 showed a strong downregulation in lung carcinoma samples and a strong upregulation in lymph node metastases compared with healthy lymph node tissue. Hsa-let-7b-5p exhibited significant downregulation in lung carcinoma tissues, whereas no altered expression of hsa-let-7f-5p was detected. 62 However, both hsa-let-7b-5p and hsa-let-7f-5p showed a significant upregulation in lymph node metastasis tissues compared to healthy lung and lymph node tissues. The potential target (of miRNAs hsa-miR-19a, hsa-miR-19b, and hsa-miR-21-1) APAF1 exhibited a significant downregulation in lung cancer tissues and a significant upregulation in lymph node tissues. APAF1 did not correlate with any of the predicted miRNAs in lung cancer tissues. An inverse correlation between APAF1 and hsa-miR-19a and hsa-miR-19b was found in lymph node metastasis tissues compared to healthy lymph node tissues. The potential target (of miRNAs hsa-let-7b-5p and hsa-let-7f-5p) HMGA2 was found upregulated in lung cancer tissues and in lymph node metastasis tissues compared to healthy lung, but its expression was stable in comparison to healthy lymph node tissues. Thus, it inversely correlated with the expression of hsa-let-7b-5p in lung carcinoma tissue but not with hsa-let-7f-5p. Because HMGA2 did not show altered expression in lymph node metastases compared with healthy lymph node, it did not correlate with either miRNA. The study performed provides an overview of the expression of miRNAs in lung carcinomas and in lymph node metastases. The exploration of the expression profiles in primary tumor and metastasis could provide a better understanding of lung tumorigenesis and metastasis and enable a better diagnosis and therapy in the future. Further studies will enable to validate the results presented here and to highlight the miRNA expression profile in lymph node metastases. Thus providing better insight into the pathogenesis of lung cancer metastasis.