Combination therapy for liver tumor growth and metastasis by low dose rapamycin and FTY720

Abstract

Background: Our previous studies demonstrated that the new immunomodulator FTY720 could suppress liver tumor growth and metastasis through down-regulation of cell survival and invasion pathways. On the other hand, rapamycin shows its anti-angiogenesis function in several cancer therapy. In order to explore the possibility of combination therapy by rapamycin and FTY720, we designed an orthotopic liver tumor nude mice model to investigate the effect of this combination therapy by comparison of the tumor growth and metastases, as well as the related signaling pathways. Materials and methods The orthotopic liver tumor nude mice models with different metastatic potential were applied. 5*106 MHCC97H or MHCC97L cells were injected subcutaneously into the right flank of the mice. Once the subcutaneous tumor reached 1 cm in diameter, it was removed and cut into about 1– 2 mm cubes which were implanted into the left liver lobe of another group of nude mice. In the single treatment group, rapamycin was given by ip injection at 0.8 mg/kg/3 days. In the combination treatment group, rapamycin (0.5 mg/kg) and FTY720 (2 mg/kg) was administrated by ip injection every 3 days. The treatments were started at 7 days after tumor implantation. The mice were sacrificed at day20, 30 and 40 after treatment, respectively. The tumor growth, proliferation (Ki67), apoptosis (TUNEL) and local/distant metastases were compared among the groups. Hepatic stellate cell activation in the tumor tissue was detected by a-SMA staining. Cell signaling related to invasion, migration (ROCK-Rho) and angiogenesis (VEGF) were compared. The effect of FTY720 and rapamycin on MHCC97H and MHCC97L was also studied in vitro functional tests. Results The tumor growth was significantly suppressed by both single and combination treatments by comparison of liver tumor volume. The incidence of lung metastasis was significantly lower in the treatment group at day 40 in a higher metastatic potential model (MHCC97H: 2/8 vs 7/8, p = 0.041; MHCC97L: 0/8 vs 4/8, p = 0.077). Suppression of hepatic stellate cell activation was mainly found in the combination treatment groups. The tumor invasiveness including venous invasion/tumor thrombus was mainly presented in the control groups. The tumor proliferation was significantly suppressed by both single and combination treatments. The RNA and protein expression of Rho, ROCK and VEGF was down regulated in the combination treatment group. Conclusion Low dose rapamycin and FTY720 combination therapy significantly inhibited liver tumor growth and lung metastases.