Murine Friend Erythroleukemia Cells Develop IFN Resistance via `IFNAR2` Transcript Absence and `IFNGR2` Frameshift Mutation

Interferons (IFNs) are crucial cytokines in the immune system, mediating antiviral and anti-proliferative responses, often leveraged in cancer therapies. Their signaling typically involves the JAK-STAT pathway, where IFNs bind to specific cell surface receptors, activating associated Janus kinases (JAKs) which then phosphorylate Signal Transducers and Activators of Transcription (STATs). These STATs translocate to the nucleus to regulate gene expression. Resistance to IFN therapy, particularly in leukemia and viral infections, remains a significant clinical challenge, often stemming from defects in this critical signaling cascade. Understanding the precise molecular mechanisms of IFN resistance is vital for developing strategies to overcome treatment failures and improve patient outcomes.

Researchers characterized two IFN-resistant cell clones, 3Cl8 and 3γR8, derived from wild-type Friend erythroleukemia cells 745A. The 3Cl8 clone was resistant to type I IFNs but sensitive to type II IFN, while 3γR8 (derived from 3Cl8) exhibited resistance to both type I and type II IFNs. The study aimed to identify the molecular defects underlying this resistance. They assessed JAK-STAT pathway activation following IFN treatment using methods like western blot for STAT phosphorylation. Furthermore, they analyzed the expression of major transcripts for IFNAR2 and IFNGR2 receptor chains via RT-qPCR and performed sequencing to detect mutations in these receptor genes, comparing findings against the sensitive 745A cells.

No activation of the JAK-STAT pathway was detected in either 3Cl8 or 3γR8 resistant cells after treatment with their respective inhibitory IFNs, confirming the functional resistance. A key finding was the absence of major transcripts for the IFNAR2 receptor chain in the type I IFN-resistant 3Cl8 cells. This transcriptional defect directly impaired the ability of type I IFNs to signal. In the type II IFN-resistant 3γR8 cells, a specific point mutation was identified in the IFNGR2 receptor chain (β chain).