Klin Onkol 2022; 35(Suppl 2): 107-109. DOI: 10.48095/ccko20221S107.
Background: Brain metastases (BM) are the most common intracranial tumors in adult cancer patients. While previously BMs were only treated symptomatically, the approach to therapy is changing due to the increasing incidence resulting from more effective treatment of primary tumors and earlier detection of small asymptomatic BMs. As the prognosis of patients with BM is highly variable, it would be useful to improve diagnostic and prognostic tools by incorporating new powerful biomarkers. MicroRNAs (miRNAs) are promising in this regard and, due to their high stability, suitable both for sequencing (RNA-Seq) and for retrospective analyses in formalin-fixed and paraffin-embedded (FFPE) tissues. Material and methods: Total RNA enriched for miRNAs was isolated from 71 fresh-frozen histopathologically confirmed BM tissues originating from 5 tumor types (lung cancer, 37%; melanoma, 23%; breast cancer, 18%; renal cell carcinoma, 15%; colorectal carcinoma, 7%). Informed consent approved by the local ethics committee was obtained from each patient before treatment. Libraries were prepared from RNA for sequencing on the NextSeq 500 platform (Illumina). Read-to-reference mapping was performed using the tool miraligner and the database miRBase, and differential analysis for 2 437 matured miRNAs was done using the tool limma. MiRNA molecules from total RNA samples isolated from a retrospective set of 119 FFPE tissues were reverse transcribed and the expression of selected differentially expressed miRNAs (miR-122-5p, miR-141-3p, miR-146a-5p, miR-194-5p, miR-200c -3p, miR-211-3p, miR-215-5p, miR-514b-3p, miR-934, miR-1270) was validated by qPCR. Results: Differential analysis identified 373 miRNAs with significantly different expression between the five BM groups (P < 0.001). Subsequent pilot validation verified significantly different expression of selected miRNAs in five BM groups. Conclusion: The presented results confirm the importance of studying dysregulated miRNA expression in BM and the diagnostic potential of validated miRNAs.
