ROS1 (c-ros oncogene 1) is a gene that encodes a receptor tyrosine kinase. Abnormalities in the ROS1 gene, such as gene rearrangements, are associated with certain types of cancer, particularly non-small cell lung cancer (NSCLC). Fluorescence In Situ Hybridization (FISH) is a molecular technique used to detect and assess ROS1 gene rearrangements in cancer cells. Here’s how ROS1 testing by FISH works:
- Sample Collection: A tissue sample, typically obtained through a biopsy or surgical procedure, is collected from the patient. This tissue sample contains cancer cells.
- Tissue Preparation: The collected tissue sample is processed and prepared for FISH analysis. This may involve fixing the tissue and preparing thin sections on glass slides.
- FISH Probe Preparation: Specific DNA probes are designed to target the ROS1 gene region. These probes are labeled with fluorescent molecules that emit distinct colors when exposed to specific wavelengths of light.
- Hybridization: The tissue sample is incubated with the DNA probes. If there are abnormalities in the ROS1 gene, such as rearrangements or fusions with other genes, the DNA probes will bind to the corresponding target sequences.
- Fluorescent Labeling: When the DNA probes bind to the target ROS1 gene sequences, they emit fluorescent signals. These signals can be visualized and analyzed using a fluorescent microscope.
- Imaging and Analysis: The tissue sample is examined under the fluorescent microscope. The number and pattern of fluorescent signals are assessed. Abnormalities, such as ROS1 gene rearrangements, are identified based on the presence of altered patterns of fluorescence signals.
ROS1 FISH testing is particularly important in the diagnosis and treatment of NSCLC. ROS1 gene rearrangements are relatively rare but are considered a driver mutation in a subset of NSCLC cases. Detecting ROS1 gene rearrangements is crucial for identifying patients who may benefit from targeted therapies, such as ROS1 inhibitors like crizotinib, entrectinib, or ceritinib. These drugs are specifically designed to block the activity of the overactive ROS1 protein and can lead to improved treatment outcomes in patients with ROS1-positive NSCLC.
The results of ROS1 FISH testing provide critical information about the genetic characteristics of cancer cells and help guide treatment decisions. As with other FISH tests, the interpretation of ROS1 FISH results should be performed by experienced pathologists or oncologists who are familiar with the clinical context and guidelines for the specific cancer being evaluated. The results are often used in combination with other diagnostic and prognostic factors to tailor treatment plans for individual patients
