The prevalence of RET/PTC mutations in papillary thyroid cancers in Turkish population and its relation between tumor histopathology and prognostic factors

Molecular targets of tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer (TC) is the eighth most frequently diagnosed cancer worldwide with a rising incidence in the past 20 years. Surgery is the primary strategy of therapy for patients with medullary TC (MTC) and differentiated TC (DTC). In DTC patients, radioactive iodine (RAI) is administered after thyroidectomy. Neck ultrasound, basal and thyroid-stimulating hormone-stimulated thyroglobulin are generally performed every three to six months for the first year, with subsequent intervals depending on initial risk assessment, for the detection of possible persistent/recurrent disease during the follow up. Distant metastases are present at the diagnosis in ∼5 % of DTC patients; up to 15 % of patients have recurrences during the follow up, with a survival reduction (70 %-50 %) at 10-year. During tumor progression, the iodide uptake capability of DTC cancer cells can be lost, making them refractory to RAI, with a negative impact on the prognosis. Significant advances have been done recently in our understanding of the molecular pathways implicated in the progression of TCs. Several drugs have been developed, which inhibit signaling kinases or oncogenic kinases (BRAF^V600E, RET/PTC), such as those associated with Platelet-Derived Growth Factor Receptor and Vascular Endothelial Growth Factor Receptor. Tyrosine kinase receptors are involved in cancer cell proliferation, angiogenesis, and lymphangiogenesis. Several tyrosine kinase inhibitors (TKIs) are emerging as new treatments for DTC, MTC and anaplastic TC (ATC), and can induce a clinical response and stabilize the disease. Lenvatinib and sorafenib reached the approval for RAI-refractory DTC, whereas cabozantinib and vandetanib for MTC. These TKIs extend median progression-free survival, but do not increase the overall survival. Severe side effects and drug resistance can develop in TC patients treated with TKIs. Additional studies are needed to identify a potential effective targeted therapy for aggressive TCs, according to their molecular characterization.

Novel RET Proto-oncogene variants identified in Turkish patients with thyroid carcinoma

Thyroid cancer is one of the few malignancies whose incidence is increasing in the last decades. Advances in understanding the molecular mechanisms lead to provide opportunity for prevention, effective early identification and targeted therapies for management. A total of 63 patients with participated in this study Genomic DNA samples were obtained from the samples formalin- embedded tissue and peripheral blood. Following polymerase chain reaction amplification of the 6 RET key exons (10, 11, 13, 14, 15, and 16) were applied and PCR products were subjected to next generation DNA sequencing (ABI 3730). Results revealed that; genotype frequencies were for rs1800961 (G > T) , GG 6 (%9.5), GT 17 (%27) TT40 (%63.5) for rs2472732 (G > A), GG31 (%49.2) GA29 (%46) AA3 (%4.8,) for rs1799939, (G > A) GG42 (%66.7) GA19 (%30.2) AA2 (%3.2), for rs1800962, (C > T) CC54 (%85.7) CT9 (%14.3), for rs1800863 (C > G), CC39 (%61.9) CG22 (%34.9) GG2 (%3.2), for rs3026272 (C > G) CC 13 (%20.6) CG 50 (%79.4). Additionally 15 potential novel genetic variants were identified in these key exons. Detailed information was given both known and new detected variants in supplementary table. Genetic variants distribution frequencies and new variants represented in Turkish thyroid cancer patients for RET proto-oncogene and that results would provide contribution to the literature.

Gene Fusions in Thyroid Cancer

BACKGROUND

Gene fusions are known in many cancers as driver or passenger mutations. They play an important role in both the etiology and pathogenesis of cancer and are considered as potential diagnostic and prognostic markers and possible therapeutic targets. The spectrum and prevalence of gene fusions in thyroid cancer ranges from single cases up to 80%, depending on the specific type of cancer. During last three years, massive parallel sequencing technologies have revealed new fusions and allowed detailed characteristics of fusions in different types of thyroid cancer.

SUMMARY

This article reviews all known fusions and their prevalence in papillary, poorly differentiated and anaplastic, follicular, and medullary carcinomas. The mechanisms of fusion formation are described. In addition, the mechanisms of oncogenic transformation, such as altered gene expression, forced oligomerization, and subcellular localization, are given.

CONCLUSION

The prognostic value and perspectives of the utilization of gene fusions as therapeutic targets are discussed.

Radiation exposure, young age, and female gender are associated with high prevalence of RET/PTC1 and RET/PTC3 in papillary thyroid cancer: a meta-analysis

Background

RET/PTC rearrangements have been identified as a specific genetic event in papillary thyroid cancer (PTC). We conducted this meta-analysis to identify an enriched population who were more likely to occur RET/PTC fusion genes.

Methods

All relevant studies in the PubMed, Web of Science, and Embase databases were searched up to June 2015. The studies found were screened according to our inclusion and exclusion criteria. All analyses were performed using STATA software.

Results

Eventually, 38 eligible studies comprising 2395 participants were included. Overall analysis indicated that radiation exposure contributed to increased RET/PTC risk (OR = 2.82; 95%CI: 1.38–5.78, P = 0.005). Stratified analysis according to RET/PTC subtype and geographical area showed that this association was restricted to the RET/PTC3 subtype (OR = 8.30, 95%CI: 4.32–15.96, P < 0.001) in the Western population. In addition, age < 18 years, i.e., young age, was associated with higher prevalence of RET/PTC3 (OR = 2.03, 95%CI: 1.14–3.62, P = 0.017), especially in the radiation-exposure subpopulation (OR = 2.35, 95%CI: 1.01–5.49, P = 0.048). The association between female gender and RET/PTC1 risk was more significant in the PTC patients without radiation exposure (OR = 1.69, 95%CI: 1.04–2.74, P = 0.034).

Conclusion

Both radiation exposure and young age are associated with increased risk of RET/PTC3 and that female gender is associated with higher prevalence of RET/PTC1 in the subpopulation without radiation exposure. The RET/PTC status in combination with radiation exposure, age, and sex should be considered in the differential diagnosis of suspicious PTC.