Relevance of BRAF and NRAS mutations in the primary tumor and metastases of papillary thyroid carcinomas

Genetic alterations landscape in paediatric thyroid tumours and/or differentiated thyroid cancer: Systematic review

Differentiated thyroid cancer (DTC) is a rare disease in the paediatric population (≤ 18 years old. at diagnosis). Increasing incidence is reflected by increases in incidence for papillary thyroid carcinoma (PTC) subtypes. Compared to those of adults, despite aggressive presentation, paediatric DTC has an excellent prognosis. As for adult DTC, European and American guidelines recommend individualised management, based on the differences in clinical presentation and genetic findings. Therefore, we conducted a systematic review to identify the epidemiological landscape of all genetic alterations so far investigated in paediatric populations at diagnosis affected by thyroid tumours and/or DTC that have improved and/or informed preventive and/or curative diagnostic and prognostic clinical conduct globally. Fusions involving the gene RET followed by NTRK, ALK and BRAF, were the most prevalent rearrangements found in paediatric PTC. BRAF V600E was found at lower prevalence in paediatric (especially ≤ 10 years old) than in adults PTC. We identified TERT and RAS mutations at very low prevalence in most countries. DICER1 SNVs, while found at higher prevalence in few countries, they were found in both benign and DTC. Although the precise role of DICER1 is not fully understood, it has been hypothesised that additional genetic alterations, similar to that observed for RAS gene, might be required for the malignant transformation of these nodules. Regarding aggressiveness, fusion oncogenes may have a higher growth impact compared with BRAF V600E. We reported the shortcomings of the systematized research and outlined three key recommendations for global authors to improve and inform precision health approaches, glocally.

Thyroglobulin expression, Ki-67 index, and lymph node ratio in the prognostic assessment of papillary thyroid cancer

The clinical significance of thyroglobulin (Tg) expression in papillary thyroid cancer (PTC) has not been systematically explored in relation to the Ki-67 index, lymph node ratio (LNR), or other conventional prognostic predictors. In this retrospective study of 327 patients with PTC, we investigated the immunohistochemical expression of Tg in both primary tumors and their matching lymph node metastases in relation to the Ki-67 index, LNR, and clinical data. Tumoral Tg immunoreactivity was inversely correlated to the Ki-67 index and tumor recurrence. The Ki-67 index was higher in lymph node metastases (mean 4%) than in the primary tumors (mean 3%). Reduced Tg expression, estimated as 0-25% Tg positive tumor cells, was more common in lymph node metastases compared to primary tumors. In addition to advanced metastatic burden (defined as N1b stage and LNR ≥ 21%), low Tg expression (0-25% positive tumor cells) in lymph node metastases had a significant prognostic impact with shorter recurrence-free survival. These findings support the potential value of histopathological assessment of Tg expression and Ki-67 index in lymph node metastases as complementary predictors to anticipate the prognosis of PTC patients better.

The clonal origin of multifocal papillary thyroid cancer: intrathyroidal spread or independent tumors?

Multifocality is a common finding in papillary thyroid cancer but the molecular pathogenesis, prognosis and management of multifocal papillary thyroid cancer are debated. The clonal origin of multifocal papillary thyroid cancer represents a controversial aspect, as two opposite viewpoints have been proposed: independent origin or intraglandular spread. Different approaches have been used for inferring the clonality of multifocal papillary thyroid cancer, including X-chromosome inactivation, mutational analysis, determination of loss of heterozygosity and, more recently, next-generation sequencing. Next-generation sequencing, able to provide information on genetic heterogeneity and phylogenetic evolution in multifocal tumors, represents the most reliable approach. While most evidences indicated an independent origin of multifocal papillary thyroid cancer, a minority of studies suggested that multifocal papillary thyroid tumors might be monoclonally derived. This discrepancy may reflect technical limitations; nevertheless, studies based on next-generation sequencing indicated that both independent and clonal origins are possible. The co-existence of multiple tumors implies a high degree of genetic heterogeneity, which may influence the best and targeted therapeutic strategy. On the other hand, intrathyroidal dissemination may indicate metastatic potential of the dominant tumor, thereby prompting more aggressive treatments. In conclusion, data available in the literature indicated that multifocal papillary thyroid cancer may derived from both intraglandular spread and independent tumor foci. The understanding of the clonal origin of multifocal papillary thyroid tumors might represent an important issue in patient treatment.

Intratumoral Genetic Heterogeneity in Papillary Thyroid Cancer: Occurrence and Clinical Significance

Intratumoral heterogeneity (ITH) refers to a subclonal genetic diversity observed within a tumor. ITH is the consequence of genetic instability and accumulation of genetic alterations, two mechanisms involved in the progression from an early tumor stage to a more aggressive cancer. While this process is widely accepted, the ITH of early stage papillary thyroid carcinoma (PTC) is debated. By different genetic analysis, several authors reported the frequent occurrence of PTCs composed of both tumor cells with and without RET/PTC or BRAF^V600E genetic alterations. While these data, and the report of discrepancies in the genetic pattern between metastases and the primary tumor, demonstrate the existence of ITH in PTC, its extension and biological significance is debated. The ITH takes on a great significance when involves oncogenes, such as RET rearrangements and BRAF^V600E as it calls into question their role of driver genes. ITH is also predicted to play a major clinical role as it could have a significant impact on prognosis and on the response to targeted therapy. In this review, we analyzed several data indicating that ITH is not a marginal event, occurring in PTC at any step of development, and suggesting the existence of unknown genetic or epigenetic alterations that still need to be identified.

Network-based method for mining novel HPV infection related genes using random walk with restart algorithm

The human papillomavirus (HPV), a common virus that infects the reproductive tract, may lead to malignant changes within the infection area in certain cases and is directly associated with such cancers as cervical cancer, anal cancer, and vaginal cancer. Identification of novel HPV infection related genes can lead to a better understanding of the specific signal pathways and cellular processes related to HPV infection, providing information for the development of more efficient therapies. In this study, several novel HPV infection related genes were predicted by a computation method based on the known genes involved in HPV infection from HPVbase. This method applied the algorithm of random walk with restart (RWR) to a protein-protein interaction (PPI) network. The candidate genes were further filtered by the permutation and association tests. These steps eliminated genes occupying special positions in the PPI network and selected key genes with strong associations to known HPV infection related genes based on the interaction confidence and functional similarity obtained from published databases, such as STRING, gene ontology (GO) terms and KEGG pathways. Our study identified 104 novel HPV infection related genes, a number of which were confirmed to relate to the infection processes and complications of HPV infection, as reported in the literature. These results demonstrate the reliability of our method in identifying HPV infection related genes. This article is part of a Special Issue entitled: Accelerating Precision Medicine through Genetic and Genomic Big Data Analysis edited by Yudong Cai & Tao Huang.