Mcl-1 mediates tumor necrosis factor-related apoptosis-inducing ligand resistance in human cholangiocarcinoma cells

• Published in: Cancer research (Chicago, Ill.) Vol. 64; no. 10; pp. 3517 - 3524
• Main Authors: TANIAI, Makiko, GRAMBIHLER, Annette, HIGUCHI, Hajime, WERNEBURG, Nate, BRONK, Steve F, FARRUGIA, Daniel J, KAUFMANN, Scott H, GORES, Gregory J
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 15.05.2004
• Subjects: Antineoplastic agents; Antineoplastic Agents - antagonists & inhibitors; Antineoplastic Agents - pharmacology; Apoptosis - drug effects; Apoptosis - physiology; Apoptosis Regulatory Proteins; bcl-X Protein; Biological and medical sciences; Carrier Proteins - biosynthesis; CASP8 and FADD-Like Apoptosis Regulating Protein; Cell Line, Tumor; Cholangiocarcinoma - drug therapy; Cholangiocarcinoma - genetics; Cholangiocarcinoma - metabolism; Cholangiocarcinoma - pathology; Down-Regulation; Drug Resistance, Neoplasm; Drug Synergism; Flavonoids - pharmacology; Genes, bcl-2 - genetics; Humans; Intracellular Signaling Peptides and Proteins; Medical sciences; Membrane Glycoproteins - antagonists & inhibitors; Membrane Glycoproteins - pharmacology; Mitochondria - drug effects; Mitochondria - physiology; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins - antagonists & inhibitors; Neoplasm Proteins - biosynthesis; Neoplasm Proteins - genetics; Neoplasm Proteins - physiology; Pharmacology. Drug treatments; Piperidines - pharmacology; Proto-Oncogene Proteins c-bcl-2 - genetics; Receptors, Tumor Necrosis Factor - biosynthesis; RNA, Small Interfering - genetics; TNF-Related Apoptosis-Inducing Ligand; Tumor Necrosis Factor-alpha - antagonists & inhibitors; Tumor Necrosis Factor-alpha - pharmacology; Tumors; Human; Resistance; Malignant cholangioma; Digestive diseases; Hepatic disease; TNF related apoptosis inducing ligand; Malignant tumor; Biliary tract disease; Protéine MCL-1
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.CAN-03-2770

Cholangiocarcinomas are usually fatal neoplasms originating from bile duct epithelia. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising agent for cancer therapy, including cholangiocarcinoma. However, many cholangiocarcinoma cells are resistant to TRAIL-mediated apoptosis. Thus, our aim was to examine the intracellular mechanisms responsible for TRAIL resistance in human cholangiocarcinoma cell lines. Three TRAIL-resistant human cholangiocarcinoma cell lines were identified. All of the cell lines expressed TRAIL receptor 1/death receptor 4 (TRAIL-R1/DR4) and TRAIL-R2/DR5. Expression of TRAIL decoy receptors and the antiapoptotic cellular FLICE-inhibitory protein (cFLIP) was inconsistent across the cell lines. Of the antiapoptotic Bcl-2 family of proteins profiled (Bcl-2, Bcl-x(L), and Mcl-1), Mcl-1 was uniquely overexpressed by the cell lines. When small-interfering-RNA (siRNA) technology was used to knock down expression of Bcl-2, Bcl-x(L), and Mcl-1, only the Mcl-1-siRNA sensitized the cells to TRAIL-mediated apoptosis. In a cell line stably transfected with Mcl-1-small-hairpin-RNA (Mcl-1-shRNA), Mcl-1 depletion sensitized cells to TRAIL-mediated apoptosis despite Bcl-2 expression. TRAIL-mediated apoptosis in the stably transfected cells was associated with mitochondrial depolarization, Bax activation, cytochrome c release from mitochondria, and caspase activation. Finally, flavopiridol, an anticancer drug that rapidly down-regulates Mcl-1, also sensitized cells to TRAIL cytotoxicity. In conclusion, these studies not only demonstrate that Mcl-1 mediates TRAIL resistance in cholangiocarcinoma cells by blocking the mitochondrial pathway of cell death but also identify two strategies for circumventing this resistance.