Z Gastroenterol 2014; 52 - P_4_48
DOI: 10.1055/s-0033-1361001

The limonoids TR4 and TR9 induce apoptosis in mouse and human hepatoma cell lines

N Lange 1, AT Tsamo 3, AK Horst 2, AE Nkengfack 3, G Tiegs 1, G Sass 1
  • 1University Medical Center Hamburg-Eppendorf, Institute of Experimental Immunology and Hepatology, Hamburg, Germany
  • 2University Medical Center Hamburg-Eppendorf, Institute of Clinical Chemistry – Center for Diagnostics, Hamburg, Germany
  • 3University of Yaoundé I, Department of Organic Chemistry, Yaounde, Cameroon

Backgrounds and aims:

Treatment options for hepatocellular carcinoma (HCC), one of the most malignant tumors worldwide, are still limited. Currently only Sorafenib is able to prolong patient survival, implicating a need for further therapy improvement. A source for potential new therapeutics is traditional medicine. Here plant extracts and some secondary metabolites extracted from plants have been shown to exert anti-viral, anti-bacterial or anti-tumor and anti-angiogenic activities. We investigated the anti-tumor activity of three different, but structurally related, new limonoids from root bark of Trichilia rubescens Oliv. in vitro.

Methods:

Human (HepG2) and mouse (Hepa1 – 6) hepatoma cell lines as well as primary mouse hepatocytes were incubated with limonoids (TR3, TR4, TR9) or solvent. Cell viability was determined by performing MTT-Assays. Induction of apoptosis was measured by Western Blot analysis as well as by colorimetric substrate turnover assays, both measuring activation of caspase-3. Luciferase reporter assays were performed to analyze NFkB and wnt pathway activity. Specific target gene expression was analyzed by real-time RT-PCR. To investigate angiogenesis, endothelial cell (HMEC-1) tube formation assays were performed.

Results:

Within 24 hours of incubation, TR4 and TR9, but not TR3, decreased viability of human hepatoma cells with a TC50 of about 5µM. Viability of mouse hepatoma cells was decreased significantly by TR4 and TR9 at 10µM, while viability of primary mouse hepatocytes was not altered. TR4 and TR9 interfered with tumor cell proliferation and induced apoptosis. Incubation of HepG2 cells with TR4 and TR9 for 6 hours resulted in reduction of NFkB- and wnt-promoter activities. Furthermore mRNA expression of NFkB and wnt target genes was decreased. In addition TR9 completely suppressed tube formation by HMEC-1 cells at a concentration of 5µM within 24 hours.

Conclusions:

The newly isolated limonoids TR4 and TR9 selectively induce apoptosis in human and mouse hepatoma cells at TC50 s below those of Sorafenib. TR4 and TR9 might therefore become new candidate substances to improve treatment of HCC.