Częstość występowania mutacji somatycznych RAS w raku rdzeniastym tarczycy — analiza populacji polskiej

Introduction: Somatic RET mutations are detectable in two-thirds of sporadic cases of medullary thyroid cancer (MTC). Recent studies reported a high proportion of RAS somatic mutations in RET negative tumours, which may indicate RAS mutation as a possible alternative genetic event in sporadic MTC tumorigenesis. Thus, the aim of the study was to evaluate the frequency of somatic RAS mutations in sporadic medullary thyroid cancer in the Polish population and to relate the obtained data to the presence of somatic RET mutations.Material and methods: Somatic mutations (RET, RAS genes) were evaluated in 78 snap-frozen MTC samples (57 sporadic and 21 hereditary) by direct sequencing. Next, three randomly selected RET-negative MTC samples were analysed by the next generation sequencing.Results: RAS mutation was detected in 26.5% of 49 sporadic MTC tumours. None of all the analysed samples showed N-RAS mutation. When only RET-negative samples were considered, the prevalence of RAS mutation was 68.7%, compared to 6% observed in RET-positive samples. Most of these mutations were located in H-RAS codon 61 (72%). None of 21 hereditary MTC samples showed any RAS mutations.Conclusions: RAS mutations constitute a frequent molecular event in RET-negative sporadic medullary thyroid carcinoma in Polish patients. However, their role in MTC tumorigenesis remains unclear. (Endokrynol Pol 2015; 66 (2): 121–125)Wstęp: Somatyczne mutacje proto-onkogenu RET wykrywane są w trzech czwartych wszystkich sporadycznych raków rdzeniastych tarczycy (MTC). Ostatnie badania wykazały, że mutacja genu RAS jest również częstym wydarzeniem w sporadycznych guzach MTC, co może oznaczać, że mutacje genów z rodziny RAS są alternatywnym wydarzeniem molekularnym w kancerogezie sporadycznej postaci tego raka. Z tego względu celem niniejszej pracy było oszacowanie częstości występowania mutacji genów RAS w sporadycznym raku rdzeniastym tarczycy w populacji polskiej i odniesieniu częstości ich występowania do obecności mutacji somatycznych proto-onkogenu RET.Materiał i metody: Materiał do badań stanowiło 78 fragmentów guza raka rdzeniastego tarczycy (57 próbek postaci sporadycznej i 21 dziedzicznej MTC). Analizowano mutacje genu RET, H-RAS, K-RAS i N-RAS metodą bezpośredniego sekwencjonowania a także 3 próbki raka sporadycznego, wybrane losowo, zostały zeskwencjonowane metodą głębokiego sekwencjonowania (Illumina).Wyniki: Mutację genów RAS wykryto w 26,5% z 49 przeanalizowanych guzów sporadycznej postaci MTC. Natomiast, gdy tylko brano pod uwagę próbki RET-negatywne, częstość występowania mutacji genów RAS wynosiła 68,7% w porównaniu z 6% obserwowanych w guzach RET-pozytywnych. Nie wykryto, w żadnej z próbek, mutacji genu N-RAS. Najczęściej wykrywaną mutacją była zmiana w kodonie 61 genu H-RAS (72%). Nie wykryto mutacji genów RAS w żadnej z próbek dziedzicznego guza raka tarczycy.Wnioski: Mutacje somatyczne genów RAS są częstym wydarzeniem obserwowanym w RET-negatywnych sporadycznych rakach rdzeniastych tarczycy w populacji polskiej. Jednakże rola tych mutacji w rozwoju rdzeniastego raka tarczycy nie jest do końca poznana. (Endokrynol Pol 2015; 66 (2): 121–125

Coexistence of TERT Promoter Mutations and the BRAF V600E Alteration and Its Impact on Histopathological Features of Papillary Thyroid Carcinoma in a Selected Series of Polish Patients

TERT promoter (TERTp) mutations are important factors in papillary thyroid carcinomas (PTCs). They are associated with tumor aggressiveness, recurrence, and disease-specific mortality and their use in risk stratification of PTC patients has been proposed. In this study we investigated the prevalence of TERTp mutations in a cohort of Polish patients with PTCs and the association of these mutations with histopathological factors, particularly in coexistence with the BRAF V600E mutation. A total of 189 consecutive PTC specimens with known BRAF mutational status were evaluated. TERTp mutations were detected in 8.5% of cases (16/189) with the C228T mutation being the most frequent. In six of the PTC specimens (3.2%), four additional TERTp alterations were found, which included one known polymorphism (rs2735943) and three previously unreported alterations. The association analysis revealed that the TERTp hotspot mutations were highly correlated with the presence of the BRAF V600E mutation and their coexistence was significantly associated with gender, advanced patient age, advanced disease stage, presence of lymph node metastases, larger tumor size, and tumor-capsule infiltration. While correlations were identified, the possibility of TERTp mutations being key molecular modulators responsible for PTC aggressiveness requires further studies

The Risk of Relapse in Papillary Thyroid Cancer (PTC) in the Context of <i>BRAF^V600E</i> Mutation Status and Other Prognostic Factors

<div><p>Introduction</p><p>The risk of over-treatment in low-advanced PTC stages has prompted clinicians to search for new reliable prognostic factors. The presence of <i>BRAF</i> mutation, the most frequent molecular event in PTC, seems to be a good candidate. However, there is still lack of randomised trials and its significance has been proved by retrospective analyses, involving a large group of patients. The question arises whether this factor is useful in smaller populations, characterised for specialised centres. Thus, the aim of the study was to evaluate the use of <i>BRAF</i> mutation as a potential predictive marker in PTC patients.</p><p>Material</p><p>233 PTC subjects treated between 2004-2006, were retrospectively analysed. Stage pT1 was diagnosed in 64.8% patients and lymph node metastases in 30.9%. Median follow-up was 7.5 years. <i>BRAF^V600E</i> mutation was assessed postoperatively in all cases.</p><p>Results</p><p><i>BRAF ^V600E</i> mutation was found in 54.5%. It was more frequent in patients > 45 years (p=0.0001), and associated with larger tumour size (p=0.004). Patients with tumours <= 10 mm were over-represented among <i>BRAF</i> negative population (p=0.03). No association between <i>BRAF</i> mutation and other clinicopathological factors was observed. <i>BRAF</i> status was associated neither with relapse nor with disease-free survival (DFS) (p=0.76). Nodal status, extrathyroidal invasion and tumour size significantly influenced DFS.</p><p>Conclusion</p><p>The risk of PTC recurrence is mainly related to the presence of lymph node metastases and extrathyroidal invasion, whereas no impact of <i>BRAF ^V600E</i> mutation has been demonstrated.</p></div

The average tumour size in <i>BRAF</i> positive patients was significantly higher than in the wild-type group (p = 0.04).

<p>The average tumour size in <i>BRAF</i> positive patients was significantly higher than in the wild-type group (p = 0.04).</p

The presence of <i>BRAF</i> mutation did not increase the risk of cancer relapse (A). However, known histopathological factors, such as lymph node involvement (B) and thyroid capsule infiltration (C) significantly influenced disease-free survival.

<p>The presence of <i>BRAF</i> mutation did not increase the risk of cancer relapse (A). However, known histopathological factors, such as lymph node involvement (B) and thyroid capsule infiltration (C) significantly influenced disease-free survival.</p

The occurrence of <i>BRAF</i> mutation in the whole study population (A), according to patients’ age (B) and gender (C).

<p>MUT—BRAF-positive samples; WT—BRAF-negative samples.</p

Detailed description of all cancer relapses.

<p>F-female, M-male, CR- complete remission, SD- stable disease</p><p>* lung metastases without radioiodine uptake</p><p>** ¹³¹I positive lung micro-dissemination</p><p>Detailed description of all cancer relapses.</p

Classification and regression tree analysis (CART) for discrimination between patients with relapse (denoted by a red bar) and non-relapsing patients (white bars).

<p>Numbers of patients are given, proportion of bars is proportional to the number of patients.</p

The association between <i>BRAF</i> mutation and TNM classification and other pathological factors.

<p>The association between <i>BRAF</i> mutation and TNM classification and other pathological factors.</p