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)