BACKGROUND: The mda-7/IL-24 receptor belongs to the type 11 cytokine receptor family, and its two heterodimeric receptors are IL-22R1/IL-20R2 and IL-20R1/IL-20R2. Mda-7/IL-24 receptor expression in liver cancer cell lines has not yet been described. This information may be helpful for further clinical gene therapy. METHODS: With normal skin total RNA as template, the cDNA sequences of IL-20R1, IL-20R2 and IL-22R were amplified by RT-PCR. Total RNA was extracted from cultured liver cancer cell lines and a normal liver cell line, then detected by northern blotting, and the expression of mda-7/IL-24 receptors was analyzed. RESULTS: PLC/PRF/5 and SMMC-7721 expressed IL-20R1; BEL-7402, Hep3B, HepG2, and PLC/PRF/5 expressed IL20R2; and HepG2 and PLC/PRF/5 expressed IL-22R. Only HepG2 expressed the IL-22R/IL-20R2 receptor complex. PLC/PRF/5 completely expressed both heterodimeric receptors. Huh-7, QGY-7701 and WRL-68 did not express the IL-24 receptor. CONCLUSION: Complete mda-7/IL-24 receptors are seldom expressed in liver cancer cell lines.