Fra1/FOSL1

Fra1/FOSL1 encodes FRA1, an inducible AP-1 transcription factor subunit that regulates gene expression in response to proliferative and environmental cues^[1]. Mechanistically, FRA1-containing AP-1 dimers connect oncogenic pathways including RAS-ERK, IL-6/STAT3, AKT/mTOR, and TGFβ signaling to transcriptional programs controlling EMT, invasion, stem-like states, and cell plasticity^[2][3][4][5]. In breast epithelial models, Fra-1/AP-1 induces EMT by increasing TGFβ1, Zeb1, Zeb2, and Slug, thereby promoting mesenchymal, invasive, and tumorigenic capacities^[2]. In colorectal cancer, FRA1 directly controls EMT-related genes and mediates crosstalk between oncogenic RAS-ERK and TGFβ signaling during tumor progression^[3]. In pancreatic models, FRA1 links KRAS signaling to acinar-to-ductal metaplasia and modulates response to RAF-MEK-ERK inhibition^[4][6]. Compared with related FOS isoforms, FRA1 showed a unique inverse correlation with distant-metastasis-free survival among Fos genes in breast cancer datasets^[2]. For experimental applications, FRA1 studies support perturbation strategies targeting expression, stability, post-translational regulation, or downstream effectors, including PARP7 inhibition, HDAC6 inhibition, MEK inhibitor combinations, and FRA1-associated target networks^[6][7][8].