A 6-Base Pair in Frame Germline Deletion in Exon 7 Of RET Leads to Increased RET Phosphorylation, ERK Activation, and MEN2A.

CONTEXT: Multiple endocrine neoplasia type 2 (MEN2) is usually caused by missense mutations in the proto-oncogene, RET. OBJECTIVE: This study aimed to determine the mutation underlying MEN2A in a female patient diagnosed with bilateral pheochromocytoma at age 31 years and with medullary thyroid carcinoma (MTC) 6 years later. METHODS: Leukocyte DNA was used for exome and Sanger sequencing. Wild-type (WT) RET and mutants were expressed in HEK293 cells. Activation of MAPK/ERK and PI3K/AKT was analyzed by Western blotting and luciferase assay. The effect of RET mutants on cell proliferation was tested in a colony forming assay. RESULTS: Exome sequencing revealed a 6-nucleotide/2-amino acid in-frame deletion in exon 7 of RET (c.1512_1517delGGAGGG, p.505_506del). In vitro expression showed that phosphorylation of the crucial tyrosine 905 was much stronger in the p.505_506del RET mutant compared with WT RET, indicating ligand-independent autophosphorylation. Furthermore, the p.505_506del RET mutant induced a strong activation of the MAPK/ERK pathway and the PI3K/AKT pathway. Consequently, the p.505_506del RET mutant cells increased HEK293 colony formation 4-fold compared with WT RET. CONCLUSION: The finding of bilateral pheochromocytoma and MTC in our patient was highly suspicious of a RET mutation. Exome sequencing revealed a 6-base-pair deletion in exon 7 of RET, an exon not yet associated with MEN2. Increased ligand-independent phosphorylation of the p.505_506del RET mutant, increased activation of downstream pathways, and stimulation of cell proliferation demonstrated the pathogenic nature of the mutation. We therefore recommend screening the whole sequence of RET in MTC and pheochromocytoma patients with red flags for a genetic cause.

Radiometal targeted tumor diagnosis and therapy with peptide hormones.

Radiometal labeled peptide hormones are promising tools for a new generation of radiopharmaceuticals, because their receptors frequently are overexpressed in many human tumors. Furthermore, peptide hormones are characterized by different advantages for clinical application, such as high tumor-to-background ratios as well as rapid blood clearance. Peptidic tumor targeting agents can be sub-divided into the following segments: peptide, spacer, bifunctional chelator and radioisotope. Here the biological and chemical properties of peptide hormones are summarized as well as their prerequisites for their use as tumor targeting agents. Additionally, promising bifunctional chelators and radioisotopes for radiometal labeling are reviewed. Some few special peptide hormones that have been pre-clinically or clinically investigated are furthermore presented, such as somatostatin, bombesin (BBS) / gastrin releasing peptide (GRP), vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY). In vitro and in vivo investigations of the binding affinity, selectivity, metabolic stability, bioavailability and biodistribution of radiolabeled peptide hormones could lead to potential peptide-based tumor targeting agents for tumor diagnosis and therapy.

A clinical evaluation of the differential force concept as applied to the edgewise bracket.

When the Siamese edgewise bracket with continuous arch wires is used, it does not always follow that with 100 to 150 Gm. of applied force only the canine and not the buccal segment or anchor unit will move. Conversely, it does not always follow that with 400 to 500 Gm. of applied force only the buccal segment or anchor unit will move forward and the canine will not move. With the sliding mechanics of this study, the percentage of greater rates of tooth movement happening coincident with greater forces was found to be 0.86. With the edgewise bracket and sliding mechanics, the curves showed that, in general, reciprocal forces cause reciprocal tooth movement with varying and relative rates of space closure. Subjectively, no relationship was found between pain and increased forces; that is, pain in this study was found just as often on the side with 100 to 150 Gm. of applied force as on the side with 400 to 500 Gm. of applied force. This is not to say that there is not more tissue damage found with the use of heavier forces.