Effect of PlGF-inhibition on survival in mice with hepatocellular carcinoma

Background: Inhibition of angiogenesis is currently hot topic in the search for an effective treatment for hepatocellular carcinoma (HCC). Up till recently, the focus was mainly on VEGF, an important regulator in the pathologic and physiologic angiogenesis. Although promising results are seen by inhibiting the VEGF-pathway, patients often suffer from major side effects. Placental growth factor (PlGF) is a VEGF analogue only involved in pathologic angiogenesis and its inhibition has the potential to restrain tumour growth, without affecting healthy organs. Therefore, we assessed whether administration of PlGF-antibodies could serve as a potential therapy for HCC in mice.\nMethods: 5-week-old male mice (sv129) received intraperitoneal (ip) injections once per week with N-nitrosodiethylamine (35 mg/kg bodyweight) or saline , which gives rise to HCC after 25W in WT. PlGF-knock-out mice (PlGF-/-) received weekly ip DEN-injections and were compared with their WT counterparts. At 26W, WT mice were treated with twice a week with murine monoclonal PlGF-antibodies (20 mg/kg anti-PlGF) or IgG for 5W and 10W. \nResults: By 25 weeks of DEN treatment, 29% of the WT mice but none of the PlGF-/- mice had succumbed to the disease (p = 0,056). Also, treatment of DEN-injected HCC mice from 25 weeks for 5 weeks with 5D11D4 (ThromboGenics N.V.) or IgG showed a significant difference in mortality. While 45% died in the control IgG group, only 23% mortality was observed in the anti-PlGF group (N=48; P < 0.05). Also, the liver/body weight ratio was 0.057 ± 0.003 in the control group versus 0.042 ± 0.004 in the 5D11D4 group (N=19; P < 0,05). After 10W treatment 90% died in the control IgG group, while only 41 % mortality was observed in the anti-PlGF group (N = 11, P < 0,05). No mortality was observed in mice injected with saline instead of DEN, followed by 5 wks of treatment with anti-PlGF or IgG. The liver/body weight ratio was 0.038 ± 0.001 in the saline and IgG group versus 0.041 ± 0.002 in the anti-PlGF group (N=12, P = 0,27).\nFigure 1: left: Mean survival of IgG and aPlGF treated mice ; right: mean survival of PlGF knock out mice and WT’s during DEN-induction \nConclusion: Our study showed that administration of 20 mg/kg anti-PlGF twice a week, has a positive effect on survival in mice with HCC. The liver/bodyweight ratio of anti-PlGF treated mice was significantly lower than in the control IgG group, showing a specific effect on liver tumours. Treatment of anti-PlGF in healthy mice did not induce negative side effects. Therefore, treatment with PlGF antibodies might serve as a promising systemic treatment in hepatocellular carcinoma patients.