Aims Development of novel targeted therapies directed against hepatocyte growth factor (HGF) or its receptor (MET) necessitates the availability of quality diagnostics to facilitate their safe and effective use. Limitations of some commercially available anti‐MET antibodies have prompted development of the highly sensitive and specific clone A2H2‐3. Here we report its analytical properties when applied by an automated immunohistochemistry method. Methods and results Excellent antibody specificity was demonstrated by immunoblot, ELISA, and IHC evaluation of characterised cell lines including NIH3T3 overexpressing the related kinase MST1R (RON). Sensitivity was confirmed by measurements of MET in cell lines or characterised tissues. IHC correlated well with FISH and quantitative RT‐PCR assessments of MET (P < 0.001). Good total agreement (89%) was observed with the anti‐MET antibody clone SP44 using whole‐tissue sections, but poor positive agreement (21–47%) was seen in tissue microarray cores. Multiple lots displayed appropriate reproducibility (R2 > 0.9). Prevalence of MET positivity by IHC was higher in non‐squamous cell NSCLC, MET or EGFR amplified cases, and in tumours harbouring abnormalities in EGFR exon 19 or 21. Conclusions The anti‐MET antibody clone A2H2‐3 displays excellent specificity and sensitivity. These properties make it suitable for clinical trial investigations and development as a potential companion diagnostic.
Context.— RET gene fusions are oncogenic drivers in nonsmall cell lung cancer and nonmedullary thyroid cancer. Selpercatinib (RETEVMO), a targeted inhibitor of RET, was approved by the US Food and Drug Administration for the treatment of RET fusion–positive nonsmall cell lung cancer and nonmedullary thyroid cancer emphasizing the need for rapid and accurate diagnosis of RET fusions. Fluorescence in situ hybridization (FISH) has been used to detect gene rearrangements, but its performance detecting RET rearrangements is understudied. Objective.— To validate and describe the performance of Abbott Molecular RET break-apart FISH probes for detecting RET rearrangements. Design.— A training set with RET fusion–positive (13) and RET fusion–negative nonsmall cell lung cancer and nonmedullary thyroid cancer samples (12) was used to establish criteria for FISH scoring. The scoring criteria was then applied to a larger validation set of samples (96). Results.— A cutoff of 19% or more positive nuclei by FISH was established in the training set and determined by the mean ±3 SD. The validation set was tested using Abbott Molecular RET break-apart FISH compared with sequencing. With this cutoff, a sensitivity of 86% (12 of 14) and specificity of 99% (81 of 82) was achieved. Bootstrapping showed sensitivity could be optimized by using a greater than 13% cutoff with indeterminate samples of 13% to 18% abnormal nuclei requiring confirmation by an orthogonal method. Using this 3-tier scoring system sensitivity increased to 100% (14 of 14) and specificity was 96% (79 of 82). Conclusions.— Abbott Molecular break-apart FISH probes can be used to detect RET fusions. Laboratories can optimize cutoffs and/or testing algorithms to maximize sensitivity and specificity to ensure appropriate patients receive effective, timely therapy.
An indirect immunoperoxidase technique was used to study by light microscopy the binding of serum from experimental autoimmune myasthenia gravis (EAMG) rabbits to junctionally and extrajunctionally located acetylcholine receptors (AChRs) in human and rat muscles. Binding was restricted to junctional AChR. Alpha bungarotoxin (a-BGT) partially blocked the binding of EAMG serum, while myasthenia gravis serum, carbamylcholine, decamethonium, and tubocurarine did not. A radioimmunoassay showed significant binding of antibodies in EAMG sera to 125l AChR. This binding was not inhibited by a-BGT, nor by carbamylcholine, decamethonium, or tubocurarine. Sera from 10 myasthenia gravis patients did not contain antibodies binding to the 125l AChR. We suggest that EAMG in rabbits induced by Torpedo AChR differs serologically from myasthenia gravis in patients, probably owing to antigenic differences between Torpedo and human AChR, and that antigenic differences also exist between junctional and extrajunctional receptors.
The recent success of vitamin D and its analogues in the treatment of psoriasis has generated extensive research into the role of vitamin D and calcium in this hyperproliferative skin disease. The ohjective of this study was to evaluate calcium and phosphorus levels in patients admitted to our dermatology service for treatment of severe psoriasis. The charts of 15 patients from 21 to 80 years of age were reviewed and admission lahoratory data values recorded. Retrospective analysis of laboratory data from patients admitted with psoriasis demonstrated no abnormalities of calcium metabolism when assessed by calcium and phosphorus levels. Although vitamin D and its analogues appear to have a role in the treatment of psoriasis, this study suggests that a systemic aberration of calcium metabolism probably does not occur.
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