Type I interferons modulate methotrexate resistance in gestational trophoblastic neoplasia

PROBLEM: Resistance to methotrexate is a leading clinical problem in gestational trophoblastic neoplasia (GTN), but there are limited laboratory models for this condition. METHOD OF STUDY: We created isogenic trophoblastic cell lines resistant to methotrexate and compared these to the parent cell lines using gene expression microarrays and qRT-PCR followed by mechanistic studies using recombinant cytokines, pathway inhibitors, and patient sera. RESULTS: Gene expression microarrays and focused analysis by qRT-PCR revealed methotrexate led to type I interferon upregulation, in particular interferon alpha 2 (IFNA2), and methotrexate resistance was associated with chronic low level increases in type I interferon expression. Recombinant IFNA2 imparted chemosensitive choriocarcinoma cells with partial resistance to methotrexate, while chemoresistant choriocarcinoma cells were uniquely sensitive to fludarabine, a STAT1 inhibitor. In pre-treatment patient sera, IFNA2 levels correlated with subsequent resistance to methotrexate chemotherapy. CONCLUSION: Methotrexate resistance is influenced by type I interferon signaling with prognostic and therapeutic implications for treating women with GTN.