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World J Gastroenterol. 2009 Dec 21;15(47):5924-35.

TRAIL-induced apoptosis of hepatocellular carcinoma cells is augmented by targeted therapies.

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First Department of Medicine, Johannes Gutenberg-University Mainz, 55101 Mainz, Germany.



To analyze the effect of chemotherapeutic drugs and specific kinase inhibitors, in combination with the death receptor ligand tumor necrosis factor-related apoptosis inducing ligand (TRAIL), on overcoming TRAIL resistance in hepatocellular carcinoma (HCC) and to study the efficacy of agonistic TRAIL antibodies, as well as the commitment of antiapoptotic BCL-2 proteins, in TRAIL-induced apoptosis.


Surface expression of TRAIL receptors (TRAIL-R1-4) and expression levels of the antiapoptotic BCL-2 proteins MCL-1 and BCL-x(L) were analyzed by flow cytometry and Western blotting, respectively. Knock-down of MCL-1 and BCL-x(L) was performed by transfecting specific small interfering RNAs. HCC cells were treated with kinase inhibitors and chemotherapeutic drugs. Apoptosis induction and cell viability were analyzed via flow cytometry and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.


TRAIL-R1 and -R2 were profoundly expressed on the HCC cell lines Huh7 and Hep-G2. However, treatment of Huh7 and Hep-G2 with TRAIL and agonistic antibodies only induced minor apoptosis rates. Apoptosis resistance towards TRAIL could be considerably reduced by adding the chemotherapeutic drugs 5-fluorouracil and doxorubicin as well as the kinase inhibitors LY294002 [inhibition of phosphoinositol-3-kinase (PI3K)], AG1478 (epidermal growth factor receptor kinase), PD98059 (MEK1), rapamycin (mammalian target of rapamycin) and the multi-kinase inhibitor Sorafenib. Furthermore, the antiapoptotic BCL-2 proteins MCL-1 and BCL-x(L) play a major role in TRAIL resistance: knock-down by RNA interference increased TRAIL-induced apoptosis of HCC cells. Additionally, knock-down of MCL-1 and BCL-x(L) led to a significant sensitization of HCC cells towards inhibition of both c-Jun N-terminal kinase and PI3K.


Our data identify the blockage of survival kinases, combination with chemotherapeutic drugs and targeting of antiapoptotic BCL-2 proteins as promising ways to overcome TRAIL resistance in HCC.


(Mitogen-activated protein kinase)/(extracellular signal regulated kinase) kinase; 5-fluorouracil; Apoptosis; BCL-xL; Doxorubicin; Hepatocellular carcinoma; MCL-1; Phosphoinositol-3-kinase; Sorafenib; Tumor necrosis factor-related apoptosis inducing ligand; c-Jun N-terminal kinase

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