ABSTRACT
DNA repair can prevent mutations and cancer development, but it can also restore damaged tumor cells after chemo and radiation therapy. We performed RNA sequencing on 95 human pathological thyroid biosamples including 17 follicular adenomas, 23 follicular cancers, 3 medullar cancers, 51 papillary cancers and 1 poorly differentiated cancer. The gene expression profiles are annotated here with the clinical and histological diagnoses and, for papillary cancers, with BRAF gene V600E mutation status. DNA repair molecular pathway analysis showed strongly upregulated pathway activation levels for most of the differential pathways in the papillary cancer and moderately upregulated pattern in the follicular cancer, when compared to the follicular adenomas. This was observed for the BRCA1, ATM, p53, excision repair, and mismatch repair pathways. This finding was validated using independent thyroid tumor expression dataset PRJEB11591. We also analyzed gene expression patterns linked with the radioiodine resistant thyroid tumors (n = 13) and identified 871 differential genes that according to Gene Ontology analysis formed two functional groups: (i) response to topologically incorrect protein and (ii) aldo-keto reductase (NADP) activity. We also found RNA sequencing reads for two hybrid transcripts: one in-frame fusion for well-known NCOA4-RET translocation, and another frameshift fusion of ALK oncogene with a new partner ARHGAP12. The latter could probably support increased expression of truncated ALK downstream from 4th exon out of 28. Both fusions were found in papillary thyroid cancers of follicular histologic subtype with node metastases, one of them (NCOA4-RET) for the radioactive iodine resistant tumor. The differences in DNA repair activation patterns may help to improve therapy of different thyroid cancer types under investigation and the data communicated may serve for finding additional markers of radioiodine resistance.
ABSTRACT
Cyclin D1 is a target molecule transcriptionally activated by aberrant beta-catenin in Wnt signalling, while prolyl isomerase Pin1 promotes cyclin D1 overexpression directly or through accumulation of beta-catenin in cancer cells. This study aimed to elucidate whether Pin1 was involved in cyclin D1 overexpression and aberrant beta-catenin in thyroid tumourigenesis by examining 14 follicular adenomas (FAa) and 14 papillary thyroid carcinomas (PTCs). All PTCs displayed cyclin D1 overexpression and strong cytoplasmic beta-catenin and/or decreased membrane beta-catenin expression by immunohistochemistry. Overexpression of cyclin D1 mRNA was observed in 45.5% of FAs and 54.5% of PTCs by TaqMan real-time PCR. Pin1 expression was observed in PTC by immunostaining and was confirmed by reverse transcriptase-PCR. There was a strong correlation between cyclin D1 and Pin1/cytoplasmic/membrane beta-catenin expression (p < 0.001), and between Pin1 and cytoplasmic (p < 0.001)/membrane (p = 0.002) beta-catenin expression in thyroid tumours. Mutation of the beta-catenin gene could not be detected in PTC. Western blot analysis demonstrated high levels of cyclin D1 and beta-catenin as well as Pin1 expression in a human PTC cell line possessing wild-type beta-catenin and APC genes. This study suggests that both cyclin D1 overexpression and aberrant beta-catenin expression are of significance in thyroid tumours. Pin1 expression appears to correlate closely with the level of cyclin D1 and aberrant beta-catenin expression in thyroid tumours such as FA and PTC. Pin1 may be an important factor in regulating cyclin D1 and beta-catenin expression during thyroid carcinogenesis.
