What is ROS1?

ROS1 is a proto-oncogene that encodes a receptor tyrosine kinase (RTK), structurally related to ALK and LTK. Normally expressed in tissues such as the kidney and nervous system, it is typically absent in normal lung tissue. In cancers such as glioblastoma, cholangiocarcinoma, and NSCLC, rearrangements involving ROS1 lead to the formation of gene fusions that activate oncogenic signaling.

These fusions retain the kinase domain of the gene and are paired with various partners such as FIG (GOPC), CD74, SLC34A2, and EZR, resulting in continuous activation of growth and survival pathways. This molecular mechanism has direct implications for targeted therapy in lung cancer.

Role of ROS1 Fusions in Disease

In non-small cell lung cancer (NSCLC), ROS1 rearrangements are present in approximately 1–2% of cases. Although less common than ALK or EGFR alterations, ROS1 fusions represent a distinct and actionable molecular subset. Patients with these fusions often respond to tyrosine kinase inhibitors (TKIs) such as crizotinib, which blocks downstream signaling driven by the active kinase.

Because ROS1 fusions do not co-occur with mutations in KRAS or EGFR, testing for this marker is crucial to ensure accurate molecular profiling and avoid inappropriate therapy. Identifying the status early helps clinicians align patients with the most effective treatment options.

About the TRUPCR® ROS1 Gene Fusions Detection Kit

The TRUPCR® ROS1 Gene Fusions Detection Kit is an in vitro diagnostic solution built for the detection of 14 known ROS1 gene fusions in NSCLC FFPE tissue. It uses a two-step real-time PCR workflow that begins with RNA extraction and reverse transcription to cDNA, followed by amplification with fusion-specific primers and probes.

Key features:

• Qualitative detection of 14 fusion transcripts
• Total assay time: approximately 80 minutes
• ABL1 included as an internal control
• Ready-to-use reagents for cDNA prep and qPCR

The assay covers known junctions involving exons 32, 34, 35, and 36 of ROS1, with fusion partners including CD74, SLC34A2, TPM3, SDC4, LRIG3, and CCDC6. This broad coverage makes the kit clinically relevant and valuable in NSCLC diagnostics.

Principle and Workflow

1. RNA Extraction: Isolate RNA from FFPE lung cancer tissue.
2. Reverse Transcription: Convert total RNA to cDNA using kit components.
3. Real-Time PCR: Amplify target fusion transcripts using gene-specific primers and probes.
4. Internal Control: The ABL1 target validates RNA quality and reverse transcription.
5. Interpretation: Analyze amplification curves to identify specific ROS1 fusions.

The assay delivers results rapidly using most standard qPCR platforms and requires minimal hands-on time, enabling high-throughput screening in clinical laboratories.

Clinical Application

The TRUPCR® ROS1 Gene Fusions Detection Kit is CE-IVD marked and optimized for use in molecular diagnostics settings. Its main clinical applications include:

• Molecular profiling of NSCLC for therapy stratification
• Companion testing for patients considered for ROS1-targeted TKIs
• Integration into multi-marker panels in lung cancer diagnostics
• Use in centralized pathology labs and hospital molecular departments

By detecting key gene fusion events early, this test supports precision oncology workflows and contributes to better patient outcomes.