Abstract: OBJECTIVE: To study the expression of 4_1BB and its biological function in different human gastric cancer cell lines. METHODS: The expression of 4_1BB in different human gastric cancer cell lines was detected by immunohistochemical technique and reverse transcription polymerase chain reaction (RT_PCR). The killing activity of lymphocytes against gastric cancer cell lines was detected by MTT, whilst IL_2,IL_10,TNF_α were tested in the supernatant by ELISA. RESULTS: RT_PCR analysis showed that the 4_1BB mRNA expressions were MGC_803 (77.30％),BGC_823 (71.68％),SGC_7901(40.06％) and MKN_28(37.65％) in decreasing order. The 4_1BB protein expressions were MGC_803, BGC_823, SGC_7901 and MKN_28 in decreasing order by cytoimmunochemistry staining. MTT analysis showed that the killing activities from high to low were MKN_28, SGC_7901, BGC_823 and MGC_803. ELISA analysis showed that IL_2 and TNF_α levels were MKN_28, SGC_7901, BGC_823 and MGC_803 and IL_10 level was MGC_803,BGC_823, SGC_7901 and MKN_28, from high to low. CONCLUSION: The four different gastric cancer cell lines all expressed 4_1BB at mRNA and protein levels. The 4_1BB expression level related to gastric cancer cell lines to different degrees. The killing activity of lymphocytes against gastric cancer cell lines increased with decreasing 4_1BB expression. 4_1BB could regulate tumor immunity by inhibiting cell factors TNF_α and IL_2 and promoting cell factor IL_10.

Key words: gastric cancer cell lines, tumor immunity, 4-1BB