The antitumor effects of interleukin 12 gene on colon cancer in vitro

Objective: To construct a Retroviral vector (GCXEXPN-mIL12) which can coexpress p35 and p40 and establish a PA317-mIL12 packaging cell system which has a sufficient expression quantity of mIL12 and a good biological activity. To observe the effects of PA317-mIL12 on the cancer cell cidal action of human peripheral lymphocyte in vitro. Methods: The full-length cDNA encoding mouse IL12 subunits p35 and p40 were amplified by polymerase chain reaction (PCR) separately. The polycistronic retroviral vector (pGCXEXPN-mIL12) was constructed in which both p35 and p40 were linked with internal ribosome entry site (IRES) from encephalomyocarditis virus and poliovirus by cohesive end ligation action. Subsequently the monophilic retrovirus packaging cell strain (PE 501) was transfected by pGCXEXPN-mIL12 with the method of electroporation. Then the packaging cells (PA317) transfected with bi-ophilic retroviral in viral supernatant were monocloned after screening with G-418 for 4 weeks. The PA317-mIL12 was generated and its virus titre was determined by NIH373. The mIL12 concentration in supernatant of PA317-mIL12 was measured by enzyme-linked immunosorbent assay (ELISA) and its biological activity measured by the method off spleen lymphocyte proliferation. The human colon adenocarcinoma cells (Lovo) were co-incubated with human peripheral blood mononuclear cells and PA317-mIL12. The killing rate of lymphocytes to Lovo was measured by MTT assay. Results: The concentration of mIL12 in the supernatant of PA317-mIL12 reached 27 ng/106/48 hrs and PA317-mIL12 could promote the spleen lymphocytic proliferation just like standard mIL12. The study also showed that the cell-mediated cytotoxicity of lymphocyte was enhanced by PA317-mIL12. The MTT result of experiment group was significantly differ from that of control group (P<0.05). Conclusion: The mIL12 gene transfer system (PA317-mIL12) which can express both p35 and p40 and has potential biological activity can obviously enhance the cell-mediated cytotoxicity of lymphocyte by PA317-mIL12