Treatment of colon cancer by regulatable lentivirus-mediated interleukin-12 gene

Abstract

Objective To evaluate the efficiency of interleukin-12 (IL-12) gene mediated by RU486 regulatable lentivirus system on tumor growth and microvessel angiogenesis of mouse colon cancer C26 cells subcutaneously implanted tumor.Methods The mouse IL-12 gene was recombined to construct the RU486 regulatable lentivirus transfer plasmid PNL-LV-RUmIL-12.The LV-RUmIL-12 lentiviruses were produced by co-transfecting PNL-LV-RUmIL-12.The expression of IL-12 in C26 colon cancer cells infected by RU486 regulated LV-RUmIL-12 lentivirus was detected by enzyme linked immunosorbent assay (ELISA) kit.Colon cancer model was established by subcutaneously inoculating C26 cells into the BALB/c mice.One hundred mice were divided into 5 groups:PBS group,blank lentivirus group (LV group),RU486 group,LV-RUmIL-12 group and LV-RUmIL-12-RU486 group.The tumor size changes were calculated.After treatment for 21 days,the mice were sacrificed by cervical dislocation.Serum levels of IL-12 were assayed by enzyme linked immunosorbent assay (ELISA).Immunohistochemical staining was employed to determine microvessel density (MVD) and CD4 + and CD8 + lymphocytes in the tumor tissues.Results After injection of LV-RUmIL-12 lentivirus,the expression of IL-12 protein in C26 cells was RU486 dose-dependent.The high-est expression level of IL-12 protein in 1 × 106 C26 cells induced by 1 × 10-5 mol/L RU486 was (148 ± 25) μg/L.Serum levels of IL-12 were (3 572.60 ±245.60),(145.43 ± 13.53),(134.53 ± 12.86),(147.32 ± 15.56) and (139.67 ± 14.84) μg/L in LV-RUmIL-12-RU486,PBS,LV,RU486 and LV-RUmIL-12 groups respectively,and IL-12 level was significantly increased in LV-RUmIL-12-RU486 group (P ＜ 0.05).The tumor growth in LV-RUmIL-12-RU486 group was markedly inhibited.The inhibition rate in LV-RUmIL-12-RU486 group was 72.59％.The MVD in LV-RUmIL-12-RU486 group (12.5 ± 4.3) was statistically decreased as copared with PBS group (45.5 ±5.7),LV group (39.5 ± 3.7),RU486 group (42.4 ±7.5) and LV-RUmIL-12 group (47.2 ±2.6,P＜0.05).AS compared with the control groups,the number of CD4 and CD8 + lymphocytes in tumor tissue of LV-RUmIL-12-RU486 group was significantly reduced (P ＜ 0.05).Conclusion The RU486 regulatable lentivirus containing IL-12 gene can inhibit the growth of transplanted mouse colon cancer in association with a significant reduction in angiogenesis. Key words: Interleukin-12; Colon cancer; Lentivirus; Angiogenesis