Gores, Gregory J.

AbstractCholangiocarcinomas 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-xL, 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-xL, 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.

Background Lidocaine, a local anesthetic, can be neurotoxic. However, the cellular mechanisms of its neurotoxicity at concentrations encountered during spinal anesthesia remain unclear. Methods The authors examined the mechanisms of lidocaine neurotoxicity in the ND7 cell line derived from rat dorsal root ganglion. Individual neurons were assayed by flow cytometry or microscopy using fluorescent probes of plasma membrane integrity, mitochondrial membrane potential, caspase activity, phospholipid membrane asymmetry, and mitochondrial cytochrome c release. Results In the ND7 cell line, lidocaine at 185 mm x 10 min to 2.3 mm x 24 h caused necrosis or late apoptosis. Equimolar Tris buffer and equipotent tetrodotoxin controls were not toxic, indicating that neither osmotic nor Na-blocking effects explain lidocaine neurotoxicity. The earliest manifestation of lidocaine neurotoxicity was complete loss of mitochondrial membrane potential within 5 min after exposure to lidocaine at a concentration of 19 mm or greater. Consistent with these data, 37 mm lidocaine (1%) induced release of mitochondrial cytochrome c into the cytoplasm, as well as plasma membrane blebbing, loss of phosphatidylserine membrane asymmetry, and caspase activation, with release of mitochondrial cytochrome c to the cytoplasm within 2 h. Treatment with z-VAD-fmk, a specific inhibitor of caspases, prevented caspase activation and delayed but did not prevent neuronal death, but did not inhibit the other indicators of apoptosis. Conclusions Collectively, these data indicate that lidocaine neurotoxicity involves mitochondrial dysfunction with activation of apoptotic pathways.

Both inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) have been implicated in the biliary tract carcinogenesis. However, it is not known whether these inflammatory mediators are induced by interdependent or parallel pathways. Because iNOS activity has been associated with diverse gene expression, the aim of this study was to determine whether iNOS induces COX-2. To address this objective, immortalized, but nonmalignant, murine cholangiocytes, 603B cells were employed for these studies. Both iNOS and COX-2 protein and mRNA were expressed in these cells. However, iNOS inhibition with either N-[3-(aminomethyl) benzyl]acetamidine or stable transfection with an iNOS antisense construct inhibited COX-2 mRNA and protein expression, an effect that was reversed by NO donors. COX-2 mRNA expression in 603B cells was reduced by pharmacological inhibitors of the p38 MAPK and JNK1/2 pathways. In contrast, neither inhibitors of the soluble guanylyl cyclase inhibitor/protein kinase G nor p42/44 MAPK pathways attenuated COX-2 mRNA expression. Finally, 603B cells grew at a rate threefold greater than 603B-iNOS antisense cells. The low growth rate of 603B-iNOS antisense cells could be restored to near that of the parent cell line with exogenous PGE2. In conclusion, iNOS induces COX-2 expression in cholangiocytes, which promotes cell growth. COX-2 induction may contribute to iNOS-associated carcinogenesis.

Background— Caveolin-1 is a regulator of signaling events originating from plasma membrane microdomains termed caveolae. This study was performed to determine the regulatory role of caveolin-1 on the proliferative events induced by platelet-derived growth factor (PDGF) in vascular smooth muscle cells (VSMCs). Methods and Results— Treatment of VSMCs with PDGF for 24 hours resulted in a loss of caveolin-1 protein expression and plasma membrane–associated caveolae, despite a 3-fold increase in caveolin-1 mRNA. Pretreatment of VSMCs with chloroquine, an inhibitor of lysosomal function, inhibited the PDGF-induced loss of caveolin-1. These studies demonstrated that caveolin-1 was a target of PDGF signaling events. Adenoviral overexpression of caveolin-1 was associated with a switch in PDGF-induced signaling events from a proliferative response to an apoptotic response. This overexpression inhibited PDGF-induced expression of cyclin D1 in the presence of unaffected mitogen-activated protein kinase activation. Conclusions— Taken together, these studies suggest that caveolin-1 is an inhibitor of PDGF proliferative responses and might be capable of transforming PDGF-induced proliferative signals into death signals.

Purpose: To study the efficacy and safety of percutaneous cisplatin-epinephrine (CDDP-EPI) injectable gel in patients with localized unresectable hepatocellular carcinoma (HCC). Patients and Methods: Eligible patients had histologically proven HCC, no prior treatment except for surgery, and no more than three tumors (each measured ≤ 7 cm, total tumor volume ≤ 200 cm3). They were treated percutaneously under ultrasound or computed tomography (CT) guidance, with up to 10 mL of CDDP-EPI gel (1 mL contains 4 mg of CDDP and 0.1 mg of EPI) per treatment and four treatments in 6 weeks to a maximum of eight treatments. The primary end points were tumor response, defined by change of percentage of tumor necrosis according to CT criteria, and safety. Survival parameters were secondary end points. Results: From June 1997 to April 2000, 58 patients (median age, 65 years) entered the study. All patients were assessable for safety, and 51 were assessable for efficacy. The median number of treatments was four (range, one to eight treatments). Objective response rate was 53% (27 of 51 patients), including 16 complete and 11 partial responses. Of the 27 responders, 14 (52%) subsequently developed progressive disease, but in most of them (93%), a new tumor arose at untreated liver sites. Median survival was 27 months (range, 18.4 to 35.7 months). The 1-, 2-, and 3-year survival rates were 79%, 56%, and 14% respectively. The procedure was well tolerated with only minor side effects. Conclusion: Percutaneous local ablation with CDDP-EPI injectable gel can induce significant tumor necrosis and local control for localized unresectable HCC, and the treatment is well tolerated.

Acute vascular or humoral rejection, a vexing outcome of organ transplantation, has been attributed by some to activation and by others to apoptosis of endothelial cells in the graft. We asked which of these processes causes acute vascular rejection by tracing the processes during the development of acute vascular rejection in porcine cardiac xenografts performed in baboons. Apoptosis, assayed by terminal deoxynucleotidyl transferase–mediated dUTP nick end-labeling (TUNEL), expression of activated caspase-3, and proapoptotic genes Bax and Bcl-x L , was not detected until acute vascular rejection was well advanced, and even then, apoptosis was largely confined to myocytes. Activation of the endothelium, as evidenced by expansion of rough endoplasmic reticulum and increased ribosomal antigen and phospho-p70 S6 kinase, occurred early in the course of acute vascular rejection and progressed through the disease process. These findings suggest that acute vascular rejection is caused by an active metabolic process and not by apoptosis in the endothelium.