👤 F Tissier

Molecular alterations of the MAPK pathway are frequently observed in papillary thyroid carcinomas (PTCs). It leads to a constitutive activation of the signalling pathway through an increase in MEK and ERK phosphorylation. ERK is negatively feedback-regulated by Dual Specificity Phosphatases (DUSPs), especially two ERK-specific DUSPs, DUSP5 (nuclear) and DUSP6 (cytosolic). These negative MAPK regulators may play a role in thyroid carcinogenesis. MAPK pathway activation was analyzed in 11 human thyroid cancer cell lines. Both phosphatases were studied in three PCCL3 rat thyroid cell lines that express doxycycline inducible PTC oncogenes (RET/PTC3, H-RASV12 or BRAFV600E). Expression levels of DUSP5 and DUSP6 were quantified in 39 human PTCs. The functional role of DUSP5 and DUSP6 was investigated through their silencing in two human BRAFV600E carcinoma cell lines. BRAFV600E human thyroid cancer cell lines expressed higher phospho-MEK levels but not higher phospho-ERK levels. DUSP5 and DUSP6 are specifically induced by the MEK-ERK pathway in the three PTC oncogenes inducible thyroid cell lines. This negative feedback loop explains the tight regulation of p-ERK levels. DUSP5 and DUSP6 mRNA are overexpressed in human PTCs, especially in BRAFV600E mutated PTCs. DUSP5 and/or DUSP6 siRNA inactivation did not affect proliferation in two BRAFV600E mutated cell lines, which may be explained by a compensatory increase in other phosphatases. In the light of this, we observed a marked DUSP6 upregulation upon DUSP5 inactivation. Despite this, DUSP5 and DUSP6 positively control cell migration and invasion. Our results are in favor of a stronger activation of the MAPK pathway in BRAFV600E PTCs. DUSP5 and DUSP6 have pro-tumorigenic properties in two BRAFV600E PTC cell line models. Show less

Wnt/β-catenin signaling pathway activation plays an important role in adrenocortical tumorigenesis, but is only in part related to β-catenin activating somatic mutations. Recently, genetic alteration in AXIN2, a key component of the Wnt/β-catenin signaling pathway, has been described in adrenocortical tumors and specifically in adrenocortical carcinoma (ACC). To assess frequency and consequences of AXIN genes alteration on a large cohort of ACC. Forty-nine adult sporadic ACC, with expression data available, in addition to both ACC cell lines H295 and H295R were studied. AXIN2 exon 8 hot-spot sequencing was performed on the entire cohort. AXIN1 entire coding region was studied on the 8 ACC with nuclear β-catenin staining. The previously described AXIN2 in-frame heterozygous 12bp deletion c2013₂₀₂₄del12 was found in 1 of the 49 ACC studied (2%), in a tumor with pSer45del activating CTNNB1 mutation and nuclear β-catenin staining. This heterozygous deletion was also found in the patient's germline DNA, extracted from peripheral blood leukocytes. This genetic alteration was also present in H295 and H295R cell lines. The single-nucleotide polymorphism rs35415678 was found with an allele frequency similar to those found in reference populations. No correlation between AXIN2 expression, AXIN2 genetic variant or nuclear β- catenin staining was observed. No AXIN1 alterations were found in the 8 ACC studied. AXIN genes do not play a major role in ACC tumorigenesis and Wnt/β-catenin signaling pathway activation. AXIN2 germline variant c2013₂₀₂₄del12 is likely to be a non-pathogenic polymorphism. Show less

The MYBPC3-A31P mutation has been identified in the USA in a colony of Maine Coon cats with an autosomal dominant hypertrophic cardiomyopathy (HCM). The objectives of this prospective study were: 1) to evaluate the prevalence of this mutation in a large feline population from Europe; 2) to compare these data with the prevalence of HCM in the Maine Coon breed. 1) 3757 cats from different breeds including 2744 Maine Coon cats were screened for the mutation. 2) 164/2744 Maine Coon cats were subjected to echocardiography (Echo-Group, mean age = 2.6 years [0.3-11.5]). 1) In the whole study population, the mutation was only found in Maine Coon cats (prevalence = 41.5%), except for one British Longhair cat. 2) 55/164 (34%) cats from the Echo-Group carried the mutation while only 12/164 (7%; 5/48 heterozygous, 5/7 homozygous mutated, 2/109 homozygous wild-type cats) showed HCM. MYBPC3-A31P was associated with a significant increased risk of HCM (relative risk = 9.91). The MYBPC3-A31P mutation is highly prevalent in Maine Coon cats in Europe and appears to be breed specific with potential marginal events. Young unaffected mutated cats and affected homozygous wild-type cats illustrate the phenotypic and etiological heterogeneity of feline HCM, as demonstrated in humans. Show less

A mutation in the sarcomeric gene coding for the myosin-binding protein C gene has been identified in a colony of Maine Coon cats with hypertrophic cardiomyopathy (MyBPC3-A31P mutation). However, the close correlation between genotype and phenotype (left ventricular hypertrophy [LVH] and dysfunction) has never been assessed in a large population, particularly in heterozygous (Hetero) cats. To investigate LV morphology and function with echocardiography and tissue Doppler imaging (TDI) in a population of Maine Coon cats tested for the MyBPC3-A31P mutation with focus on Hetero animals. Ninety-six Maine Coon cats. Prospective observational study. Cats were screened for the MyBPC3-A31P mutation and examined with both echocardiography and 2-dimensional color TDI. Fifty-two out of 96 cats did not have the mutation (wild-type genotype, Homo WT), 38/96 and 6/96 were Hetero- and homozygous-mutated (Homo M) cats, respectively. Only 11% of Hetero cats (4/38) had LVH and 29% (10/34) of Hetero cats without LVH were >4 years old (4.1-11.5 years). LVH was also detected in 2 Homo WT cats (4%). A significantly decreased (P < .05) longitudinal E/A (ratio between early and late diastolic myocardial velocities) in the basal segment of the interventricular septum was observed in Hetero cats without LVH (n = 34) compared with Homo WT cats without LVH (n = 50), thus confirming that the Hetero status is associated with regional diastolic dysfunction (P < .05). The heterozygous status is not consistently associated with LVH and major myocardial dysfunction. Moreover, Homo WT cats can also develop LVH, suggesting that other genetic causes might be implicated. Show less