CRLF1 (cytokine receptor-like factor 1) is a soluble type I cytokine receptor that functions primarily as a component of a heterodimeric cytokine complex. When bound to CLCF1 (cardiotrophin-like cytokine factor 1), CRLF1 forms a neurotropic cytokine playing crucial roles in neuronal development and immune regulation 1. The CRLF1/CLCF1 complex activates JAK/STAT3 signaling pathways 2, while CRLF1 can independently activate multiple downstream effectors including LIFR-JAK1/2-STAT3 3, ERK1/2 4, and AKT/mTORC2 cascades 5. CRLF1 is predominantly expressed in cardiac fibroblasts and immune cells, where it functions as a paracrine factor regulating cell proliferation, differentiation, and inflammatory responses. Functionally, CRLF1 promotes cardiomyocyte hypertrophy in hypertrophic cardiomyopathy 3, cardiac fibrosis 4, and nucleus pulposus cell senescence in intervertebral disc degeneration 2. In cancer contexts, CRLF1 inhibits pyroptosis to enhance chemotherapy resistance in ovarian cancer 5 and promotes papillary thyroid carcinoma progression via MYH9-ERK-ETV4 signaling 6. CRLF1 expression is downregulated by miR-8485 to suppress chondrocyte inflammation in osteoarthritis 7. Loss-of-function studies consistently demonstrate that CRLF1 inhibition attenuates disease phenotypes, establishing it as a potential therapeutic target for cardiac, degenerative, and malignant disorders.