To determine whether IgM was widely expressed in non-B cells, especially epithelial cancer cell lines, we assessed the expression of Ig μ and Ig κ genes in four human epithelial cancer cell lines (cervical cancer cell lines HeLa and HeLa MR, colon cancer cell line SW480, and hepatic cancer cell line HepG2), one osteosarcoma cell line (U-2 OS), and two human embryonic kidney cell lines (293 and 293T) by RT-PCR. The gene discussed is CD40LG; the disease is osteosarcoma.