Deciphering the mechanisms underlying antitumor immunity is critical for improving cancer immunotherapy efficacy. Here, we identify WFDC21P (lnc-DC) as a positive regulator of antitumor immunity through promoting the activation of the RNA-sensing retinoic acid-inducible gene-I (RIG-I) pathway in triple-negative breast cancer (TNBC). WFDC21P directly binds to RIG-I-interacting protein G3BP1 and is required for a rapid assembly of functional G3BP1-RIG-I-double-stranded RNAs condensates via phase s...