To ameliorate expression B₇ molecule of tumor cell. Mouse lung cancer cell line ALA₉₇₀₂ and active B lymphocytes were fused by polyethylene glycol. After screening with ELISA and immunocytochemistry, the expression of lung cancer antigen and B₇ molecule in the fusion cells were monitored by S-P immunocytochemistry staining. Proliferation of the fusion cells was observed in vitro and in vivo. A fusion cell line, FLB2C, was obtained through screening. FLB2C could express the lung cancer antigen and B₇ molecule. The results of in vitro culture showed that the wall adherence characteristic of FLB2C was abated and the growth of FLB2C was slower than that of ALA₉₇₀₂ . The cell multiplication time of FLB2C prolonged and no colony was formed in soft agar. No tumor mass was observed in vivo after inoculation of FLB2C into mice. Expression of B₇ molecule in tumor cell can be ameliorated through cell fusion, thereby antigenicity of tumor cell will be raised. The oncogenicity of FLB2C is obviously weakened through fusion with normal cells. This provides the basis for preparation of better lung cancer vaccines.