Involvement of glyceraldehyde-3-phosphate dehydrogenase in tumor necrosis factor-related apoptosis-inducing ligand-mediated death of thyroid cancer cells.

TNF-related apoptosis-inducing ligand (TRAIL) is cytotoxic to most thyroid cancer cell lines, including those originating from anaplastic carcinomas, implying TRAIL as a promising therapeutic agent against thyroid cancers. However, signal transduction in TRAIL-mediated apoptosis is not clearly understood. In addition to its well-known glycolytic functions, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein, including its surprising role as a mediator for cell death. In this study we explored the involvement of GAPDH in TRAIL-mediated thyroid cancer cell death. In follicular undifferentiated thyroid cells, S-nitrosylation and nuclear translocation of GAPDH appear to mediate TRAIL-induced cell death at least partially, as evidenced by pretreatment with N-nitro-L-arginine methyl ester, a competitive nitric oxide synthase inhibitor that partially but significantly attenuated TRAIL-induced apoptosis through the reduction of S-nitrosylation and nuclear translocation of GAPDH. In addition, GAPDH small interfering RNA partially prevented the apoptotic effect of TRAIL, although TRAIL-induced nitric oxide synthase stimulation and production of nitric oxide were not attenuated. Furthermore, nuclear localization of GAPDH was observed in another thyroid cancer cell line, KTC2, which is also sensitive to TRAIL, but not in those TRAIL insensitive cell lines: ARO, KTC1, and KTC3. These data indicate that nitric oxide-mediated S-nitrosylation of GAPDH and subsequent nuclear translocation of GAPDH might function as a mediator of TRAIL-induced cell death in thyroid cancer cells.

Different induction of GRP78 and CHOP as a predictor of sensitivity to proteasome inhibitors in thyroid cancer cells.

Proteasome inhibitors represent a novel class of antitumor agents with preclinical and clinical evidence of activity against hematological malignancies and solid tumors. Emerging lines of evidence suggest that the unfolded protein response is implicated in proteasome inhibitors-induced apoptosis. Glucose-regulated protein 78 kDa (GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) as part of the unfolded protein response play critical roles in cell survival or death. Here we demonstrate that induction of GRP78 and CHOP are differently regulated upon proteasome inhibition in different thyroid cancer cell lines, and GRP78 levels as well as preferential induction of GRP78 or CHOP appears to be involved in the responsiveness. Insensitive ARO, 8305C, and 8505C cell lines inherently express relatively high levels of GRP78 compared with sensitive cell lines, and its levels are further up-regulated upon treatment with proteasome inhibitors. CHOP levels are dramatically induced in sensitive cell lines until 24 h after proteasome inhibition. On the other hand, only a slight increase is observed at 4 h in insensitive cell lines, and this increase is unable to be detected after 8 h. Insensitive cells are sensitized to proteasome inhibition by suppression of GRP78. Furthermore, suppression of CHOP induction or overexpression of GRP78 partially prevents proteasome inhibition-mediated cell death. Our study indicates a molecular mechanism by which the sensitivity of thyroid cancer cells is regulated by the level of GRP78 as well as preferential induction of GRP78 or CHOP upon treatment with proteasome inhibitors. Our experiments therefore suggest a novel approach toward sensitization of thyroid cancer cells to proteasome inhibitors.

Antisurvivin oligonucleotides inhibit growth and induce apoptosis in human medullary thyroid carcinoma cells.

Survivin is a novel member of the inhibitor of apoptosis protein (IAP) family, which is known to be over-expressed in various carcinomas and associated with their biologically aggressive characteristics. The aim of this study was to investigate survivin expression in human medullary thyroid carcinoma (MTC) and a MTC cell line TT, correlate survivin expression with clinicopathologic features of MTC, and test effects of antisurvivin oligonucleotides (ASODNs) on growth and apoptosis of TT cells. Survivin expression was immunohistochemically determined in formalin-fixed and paraffin-embedded specimens obtained from 10 cases of normal thyroid (NT) and 10 cases of MTC, and in TT cells. In TT cells, we confirmed survivin expression and its down-regulation by ASODNs using RT-PCR and Western blot analyses, and investigated effects of ASODNs on viability and growth by MTT assay and apoptosis by apoptotic analyses including DNA laddering assay, acridine orange/ethidium bromide staining and flow cytometric cell cycle analysis. Immunohistochemical analysis showed high survivin expression in MTC and TT cells, whereas no immunoreactivity was detectable in NT. Statistical analyses revealed no significant correlation of survivin expression with the clinicopathologic features of MTC. In TT cells, survivin expression at both mRNA and protein levels was confirmed and could be down-regulated by ASODNs concomitant with decrease in viability and growth, and increase in apoptosis. Our results suggest that survivin plays an important role in MTC independent of the conventional clinicopathologic factors, and ASODNs is a promising survivin-targeted gene therapy for MTC.

[The inhibitory effect of vascular endothelial growth factor antisense oligonucleotides in angiogenesis of thyroid carcinoma].

OBJECTIVE: To investigate the inhibitive effect of antisense oligonucleotide (ASODN) on vascular endothelial growth factor (VEGF) expression and endothelial cell growth in thyroid carcinoma. METHODS: Targeted ASODN of VEGF was designed and synthesized, then transfected to TT (medullary thyroid carcinoma) cell line and the culture supernatant was collected in which ECV304 (endothelial cell line) was seeded. At the same time positive control [sense oligonucleotides (SODN) group] and normal control were set for comparison. Cell growth condition was observed under microscope. RT-PCR and immuocytochemistry were used for detection of VEGF mRNA and protein expression in TT cells. MTT assay was used for cell growth inhibition ratio (IR) of TT and ECV304 cells, flow cytometry (FCM) for apoptotic index (AI) of ECV304 cells and acridine orange/ethidium bromide (AO/EB) staining for apoptotic morphology of ECV304 cells. RESULTS: As compared with positive and normal control groups, VEGF mRNA and protein expressions in TT cells of ASODN transfection groups were obviously decreased (P < 0.01). Cell growth was not influenced apparently in ECV304 cells with direct ASODN administration, but ECV304 cell growth in ASODN conditioned medium was significantly inhibited and IR (0.21 +/- 0.03, 0.31 +/- 0.01, 0.42 +/- 0.22) was significantly higher than that of SODN group (0.05 +/- 0.03, P < 0.01), with the presence of apparent apoptosis. The effect mentioned above was in a dose-dependent manner. CONCLUSION: ASODN can suppress endothelial cell growth and inhibit tumor angiogenesis possibly by specifically blocking VEGF expression in thyroid carcinoma.