The Y606C RET mutation causes a receptor gain of function

Screening of RET gene mutations in Chinese patients with medullary thyroid carcinoma and their relatives

The rearranged during transfection (RET) gene is a proto-oncogene; active mutations frequently occur in medullary thyroid carcinoma (MTC). This study investigated the spectrum of germline RET mutations and clinical features in Chinese hereditary MTC patients. A total of 53 family members from 11 different hereditary MTC families were recruited for detection of RET exon 8, 10, 11, 13, 14, 15, and 16 mutations, in genomic DNA from peripheral blood leucocytes using polymerase chain reaction (PCR) and direct DNA sequencing. Of the 53 participants, eight different germline RET mutations were detected in 37 individuals. These RET mutations were distributed in exons 10, 11, 13, and 16. The most frequent RET mutation was localized at exon 11 codon 634 (67.6 %; 25/37) and the most prevalent mutation was C634R (37.8 %; 14/37). The most frequent phenotype was multiple endocrine neoplasia type 2A (MEN2A). The incidences of MTC, pheochromocytoma, and hyperparathyroidism in the MEN2A patients were 100, 36.4 and 18.2 %, respectively. The phenotype of families with Y606C or L790F mutation was categorized as familial medullary thyroid carcinoma. Moreover, one proband was identified with multiple endocrine neoplasia type 2B and carried a de novo mutation of M918T. Two families with C618S/Y mutation were categorized as unclassified multiple endocrine neoplasia type 2. Our results further substantiate that most germline mutations of the RET proto-oncogene were localized at codon 634 in Chinese hereditary MTC patients and carriers. RET mutation at codon 634 was always associated to the phenotype of MEN2A. Screening of RET mutations should be probably limited to exons 10, 11, 13 and 16 initially to be cost-effective in China.

Multiple endocrine neoplasia type 2: achievements and current challenges

Incremental advances in medical technology, such as the development of sensitive hormonal assays for routine clinical care, are the drivers of medical progress. This principle is exemplified by the creation of the concept of multiple endocrine neoplasia type 2, encompassing medullary thyroid cancer, pheochromocytoma, and primary hyperparathyroidism, which did not emerge before the early 1960s. This review sets out to highlight key achievements, such as joint biochemical and DNA-based screening of individuals at risk of developing multiple endocrine neoplasia type 2, before casting a spotlight on current challenges which include: (i) ill-defined upper limits of calcitonin assays for infants and young children, rendering it difficult to implement the biochemical part of the integrated DNA-based/biochemical concept; (ii) our increasingly mobile society in which different service providers are caring for one individual at various stages in the disease process. With familial relationships disintegrating as a result of geographic dispersion, information about the history of the origin family may become sketchy or just unavailable. This is when DNA-based gene tests come into play, confirming or excluding an individual's genetic predisposition to multiple endocrine neoplasia type 2 even before there is any biochemical or clinical evidence of the disease. However, the unrivaled molecular genetic progress in multiple endocrine neoplasia type 2 does not come without a price. Screening may uncover unknown gene sequence variants representing either harmless polymorphisms or pathogenic mutations. In this setting, functional characterization of mutant cells in vitro may generate helpful ancillary evidence with regard to the pathogenicity of gene variants in comparison with established mutations.

The FGFR4 Y367C mutant is a dominant oncogene in MDA-MB453 breast cancer cells

Mutational analysis of oncogenes is critical for our understanding of cancer development. Oncogenome screening has identified a fibroblast growth factor receptor 4 (FGFR4) Y367C mutation in the human breast cancer cell line MDA-MB453. Here, we investigate the consequence of this missense mutation in cancer cells. We show that MDA-MB453 cells harbouring the mutation are insensitive to FGFR4-specific ligand stimulation or inhibition with an antagonistic antibody. Furthermore, the FGFR4 mutant elicits constitutive phosphorylation leading to an activation of the mitogen-activated protein kinase cascade as shown by an enhanced Erk1/2 phosphorylation. Cloning and ectopic expression of the FGFR4 Y367C mutant in HEK293 cells revealed high pErk levels and enhanced cell proliferation. Based on these findings, we propose that FGFR4 may be a driver of tumour growth, particularly when highly expressed or stabilized and constitutively activated through genetic alterations. As such, FGFR4 presents an option for further mutational screening in tumours and is an attractive cancer target with the therapeutic potential.

Constitutive RET tyrosine kinase activation in hereditary medullary thyroid cancer: clinical opportunities

The ground-breaking discovery of genotype-phenotype relationships in hereditary medullary thyroid cancer has greatly facilitated early prophylactic thyroidectomy. Its timing depends not solely on a positive gene test but, more importantly, on the type of the REarranged during Transfection (RET) mutation and its underlying mode of RET receptor tyrosine kinase activation. In the past decade, the therapeutic corridor opened by molecular information has been defined down to a remarkable level of detail. Based on mutational risk profiles, preemptive thyroidectomy is recommended at 6 months of age for carriers of highest-risk mutations, before the age of 5 years for carriers of high-risk mutations, and before the age of 5 or 10 years for carriers of least-high-risk mutations. Additional lymph node dissection may not be needed in the absence of increased preoperative basal calcitonin levels. Better comprehension of RET function should enable the design of targeted therapies for RET carriers beyond surgical cure in whom the DNA-based 'window of opportunity' has been missed.

Medullary thyroid cancer: management guidelines of the American Thyroid Association

BACKGROUND

Inherited and sporadic medullary thyroid cancer (MTC) is an uncommon and challenging malignancy. The American Thyroid association (ATA) chose to create specific MTC Clinical Guidelines that would bring together and update the diverse MTC literature and combine it with evidence-based medicine and the knowledge and experience of a panel of expert clinicians.

METHODS

Relevant articles were identified using a systematic PubMed search and supplemented with additional published materials. Evidence-based recommendations were created and then categorized using criteria adapted from the United States Preventive Services Task Force, Agency for Healthcare Research and Quality.

RESULTS

Clinical topics addressed in this scholarly dialog included: initial diagnosis and therapy of preclinical disease (including RET oncogene testing and the timing of prophylactic thyroidectomy), initial diagnosis and therapy of clinically apparent disease (including preoperative testing and imaging, extent of surgery, and handling of devascularized parathyroid glands), initial evaluation and treatment of postoperative patients (including the role of completion thyroidectomy), management of persistent or recurrent MTC (including the role of tumor marker doubling times, and treatment of patients with distant metastases and hormonally active metastases), long-term follow-up and management (including the frequency of follow-up and imaging), and directions for future research.

CONCLUSIONS

One hundred twenty-two evidence-based recommendations were created to assist in the clinical care of MTC patients and to share what we believe is current, rational, and optimal medical practice.