Testing for NTRK Fusions
Starting with a chromosomal rearrangement, NTRK oncogenic activation necessitates translation of the fusion gene and expression of the chimeric TRK protein. To determine if a tumor has an NTRK fusion, various laboratory assays can be employed. The DNA status can be investigated using fluorescence in-situ hybridization (FISH) and DNA-based next-generation sequencing (NGS), while evaluating the transcribed RNA, reverse transcription-polymerase chain reaction (RT-PCR), real time-PCR, and RNA-based NGS analyses can be utilized. These methods examine the RNA molecules produced by the tumor. Finally, the protein product can be directly evaluated using immunohistochemical staining (IHC). This technique allows for the visualization and analysis of the chimeric TRK protein. These laboratory assays collectively help in determining whether a tumor has undergone NTRK fusion and activation.(24)