Apoptosis Of Thyroid Carcinoma Cells Research Articles

Tripartite motif containing 63, regulated by E26 transformation specific variant 4, facilitates the thyroid carcinoma progression and the AKT, p38, and ERK signaling pathways

The current study aimed to investigate the role of tripartite motif containing 63 (TRIM63) in the progression of thyroid carcinomas. The results showed that TRIM63 was highly expressed in thyroid carcinomas tissues. TRIM63 knockdown inhibited the proliferation and induced the apoptosis of thyroid carcinoma cells, and overexpression of TRIM63 promoted the cell proliferation ability. These results were further confirmed by the in vivo growth of xenograft tumors. Subsequently, the underlying mechanism was explored. TRIM63 silencing repressed the AKT, p38, and ERK signaling pathways in thyroid carcinoma cells, and the contrary results were observed in TRIM63-upregulated thyroid carcinoma cells. Furthermore, we found that E26 transformation specific variant 4 (ETV4) regulated the transcription of TRIM63. The loss of TRIM63 reversed the ETV4 overexpression-induced promotion of proliferation in thyroid carcinomas cells. In conclusion, TRIM63, regulated by ETV4, activates the AKT, p38, and ERK signaling pathways and facilitates the thyroid carcinoma development.

FOXP2 regulates the proliferation, migration, and apoptosis of thyroid carcinoma cells via Wnt/β-catenin signaling pathway

Purpose: To determine the effect of Forkhead box P2 (FOXP2) on thyroid carcinoma cell growth and metastasis.
 Methods: Expression of FOXP2 in thyroid carcinoma cells was determined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. The 3-[4,5-dimethylthiazol-2-yl]- 2,5 diphenyl tetrazolium bromide (MTT) was applied to evaluate cell viability, while cell migration and invasion were assessed by wound healing and Transwell assays, respectively. Flow cytometry and western blot were conducted to investigate cell apoptosis. The underlying mechanisms were investigated using western blot assay.
 Results: Expression of FOXP2 was lower in primary thyroid carcinoma tissues than in normal tissues based on data from the TCGA database. Similarly, FOXP2 was lower in thyroid carcinoma cells at the mRNA and protein levels. Ectopic FOXP2 expression decreased cell viability, and retarded the migration and invasion of thyroid carcinoma cells. FOXP2 overexpression in thyroid carcinoma cells led to down-regulated expression of matrix metallopeptidase (MMP) 2, MMP 9, and proliferating cell nuclear antigen (PCNA), as well as induction of cell apoptosis. Moreover, FOXP2 overexpression resulted in enhanced Bax expression while Bcl-2 was reduced. Ectopic expression of FOXP2 decreased β-catenin, c-myc, and cyclin D1 in thyroid carcinoma cells.
 Conclusion: FOXP2 suppresses the proliferation and metastasis of thyroid carcinoma cells, but promotes apoptosis through suppression of the Wnt/β-catenin signaling pathway. These results provide an insight that may lead to the development of a novel potential therapeutic strategy for treating thyroid carcinoma.

Integrated bioinformatics analysis for the identification of key genes and signaling pathways in thyroid carcinoma.

Thyroid carcinoma (TC) is one of the most common types of endocrine neoplasm with poor prognosis due to its aggressive behavior. Biomarkers for early diagnosis and prevention of TC are in urgent demand. By using a bioinformatics analysis, the present study aimed to identify essential genes and pathways associated with TC. First, the GSE27155 and GSE50901 expression profiles were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were obtained using the two microarray datasets and further subjected to integrated analysis. A gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed 45 common DEGs in the two datasets. GO and KEGG pathway analysis indicated that the biological functions of the DEGs included protein binding, cardiac muscle cell potential involved in contraction, aldehyde dehydrogenase activity, the TGF-β receptor signaling pathway and the canonical Wnt signaling pathway. A protein-protein interaction network was also constructed and visualized to display the nodes of the top 9 up- and 36 downregulated common DEGs. The integrated bioinformatics analysis indicated that potassium inwardly rectifying channel subfamily J member 2 (KCNJ2) was the most significantly upregulated DEG. The transcriptional levels of KCNJ2 were confirmed to be elevated in TC tissues compared with those in normal tissues using reverse transcription-quantitative PCR analysis. Furthermore, the expression level of KCNJ2 was significantly associated with the 5-year survival rate of patients with TC, which was determined using the Kaplan-Meier method. In TC cell lines, KCNJ2 was also upregulated as compared with that in a normal control cell line. Finally, small interfering RNA was used to knock down the expression of KCNJ2, which was demonstrated to inhibit cell proliferation, migration and invasion, while increasing apoptosis in TC cells. In conclusion, in the present study, KCNJ2 was screened as an oncogene with a crucial role in TC development and progression and may represent a promising candidate biomarker and therapeutic target for TC.

Oleanolic acid inhibits cell proliferation migration and invasion and induces SW579 thyroid cancer cell line apoptosis by targeting forkhead transcription factor A.

Oleanolic acid (OA) is a naturally occurring triterpenoid that possesses antitumor activity against several tumor cell lines. However, the potential mechanism underlying OA-induced thyroid carcinoma cell death is poorly understood. We investigated the biological functions of OA by performing migration, invasion, colony formation, and apoptosis assays on SW579 cells. Forkhead box A1 (FOXA1) expression was used to predict poor prognosis in patients with thyroid carcinoma among the TCGA samples from the UALCAN and gene expression profiling interactive analysis databases. Western blot was used to detect protein expression level. Results revealed that OA inhibited the migration, colony formation, and invasion of thyroid carcinoma cells in a dose-dependent manner. Further investigation verified that OA treatment induced significant apoptosis of thyroid carcinoma cells. Moreover, high FOXA1 expression predicted the poor prognosis of patients with thyroid cancer. The proliferation, migration, and invasion of thyroid carcinoma cells were significantly decreased when FOXA1 was silenced. OA significantly increased Akt phosphorylation and reduced FOXA1 expression in SW579 cells, but only PI3K/Akt inhibitor LY294002 attenuated OA-induced FOXA1 downregulation. Furthermore, Akt overexpression suppressed the FOXA1 expression in SW579 cells. In addition, molecular docking assay revealed that OA possessed high affinity toward FOXA1 with a low binding energy. OA may be a potential chemotherapeutic agent against thyroid carcinoma cells.

Effects of serine/threonine-protein kinase B-Raf-activated long-chain non-coding RNA on apoptosis and autophagy in thyroid carcinoma cells

To investigate the effect of serine/threonine-protein kinase B-Raf (BRAF)-activated long-chain non-coding RNA (lncRNA-BANCR) on apoptosis and autophagy in thyroid carcinoma cells and the underlying mechanisms. Methods: RT-PCR was used to detect the expression of lncRNA-BANCR in thyroid carcinoma and normal thyroid tissues. The association between lncRNA-BANCR and clinicopathological data was analyzed in patients with thyroid cancer. Cell counting kit-8 (CCK-8) was used to detect the effect of lncRNA-BANCR on the proliferation of thyroid cancer cells. The effect of lncRNA-BANCR on the apoptosis of thyroid carcinoma cells was detected by flow cytometry. Transwell invasion assay was used to detect the effect of lncRNA-BANCR on the invasive ability of thyroid cancer cells. Western blot was used to detect the changes of autophagy proteins LC3-I and LC3-II after the lncRNA-BANCR expression was suppressed. Results: Compared with normal thyroid tissues, the expression level of lncRNA-BANCR in thyroid carcinoma tissues was elevated (P<0.05). The expression of lncRNA-BANCR was positively related to the pathological stage of thyroid carcinoma and the lymph node metastasis. Inhibition of lncRNA-BANCR expression attenuated the proliferation and invasion ability of thyroid cancer cells (both P<0.05); but the apoptosis was enhanced (P<0.05); the expression levels of autophagy protein LC3-I and LC3-II were also increased (P<0.05). Conclusion: The expression level of lncRNA-BANCR affects the proliferation, invasion and apoptosis of thyroid cancer cells through modulation of autophagy behavior.

Effects of nuclear factor‑κB on the uptake of 131iodine and apoptosis of thyroid carcinoma cells.

Thyroid carcinoma is primarily treated by surgery combined with radioactive 131iodine (131I) treatment; however, certain patients exhibit resistance to 131I treatment. Previous research indicated that nuclear factor-κB (NF-κB) was associated with resistance to 131I in cancer cells. The present study aimed to investigate the effects of NF-κB on 131I uptake and apoptosis in thyroid carcinoma cells. TPC-1 and BCPAP cell lines were employed as research models in the present study, and the expression of NF-κB was inhibited by RNA interference (RNAi). The ability of TPC-1 and BCPAP cells to uptake 131I was measured and the cell viability was detected by an MTT assay. Finally, the expression of the apoptosis-associated proteins X-linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis protein 1 (cIAP1) and caspase-3 in TCP-1 and BCPAP cells was determined by western blotting. Western blotting results demonstrated that the expression levels of NF-κB in TPC-1 and BCPAP cells were successfully downregulated by RNAi (P<0.05), while analysis of 131I uptake revealed no significant alterations in the 131I uptake ability of cells following RNAi (P>0.05). MTT experiments demonstrated that the inhibition of NF-κB expression in combination with radiation (131I treatment) led to a marked reduction in cell viability (P<0.05). Furthermore, western blot analysis revealed that the inhibition of NF-κB expression downregulated the expression levels of XIAP and cIAP1 (P<0.05), while the expression levels of caspase-3 were upregulated, indicating that the observed reduction in cell viability following NF-κB inhibition may be due to an increased level of apoptosis. Although NF-κB inhibition did not affect the 131I uptake of thyroid cancer cells, this inhibition may increase the apoptotic effects of radioactive 131I.

TRAP1 regulates cell cycle and apoptosis in thyroid carcinoma cells.

Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a heat shock protein 90 (HSP90) molecular chaperone upregulated in several human malignancies and involved in protection from apoptosis and drug resistance, cell cycle progression, cell metabolism and quality control of specific client proteins. TRAP1 role in thyroid carcinoma (TC), still unaddressed at present, was investigated by analyzing its expression in a cohort of 86 human TCs and evaluating its involvement in cancer cell survival and proliferation in vitro Indeed, TRAP1 levels progressively increased from normal peritumoral thyroid gland, to papillary TCs (PTCs), follicular variants of PTCs (FV-PTCs) and poorly differentiated TCs (PDTCs). By contrast, anaplastic thyroid tumors exhibited a dual pattern, the majority being characterized by high TRAP1 levels, while a small subgroup completely negative. Consistently with a potential involvement of TRAP1 in thyroid carcinogenesis, TRAP1 silencing resulted in increased sensitivity to paclitaxel-induced apoptosis, inhibition of cell cycle progression and attenuation of ERK signaling. Noteworthy, the inhibition of TRAP1 ATPase activity by pharmacological agents resulted in attenuation of cell proliferation, inhibition of ERK signaling and reversion of drug resistance. These data suggest that TRAP1 inhibition may be regarded as potential strategy to target specific features of human TCs, i.e., cell proliferation and resistance to apoptosis.

Effect of human leukocyte antigen-F associated transcript 10 on the proliferation and apoptosis of thyroid carcinoma cells

Objective To observe the effects of human leukocyte antigen (HLA)-F associated transcript 10 (FAT10)ΔGG, a carboxyl-terminal diglycine deficient mutant, on the proliferation and apoptosis of thyroid carcinoma cell line TPC-1. Methods Specimens of cervical carcinoma in situ and normal thyroid tissue, 10 each, were collected. The expression levels of FAT10 protein in these specimens were detected by Western blotting. Site-directed mutagenesis was applied to construct the mutant pcDNA3.0-flag-FAT10ΔGG plasmid. The TPC-1 cells were then transiently transfected with wild-type FAT10, FAT10ΔGG and empty vector (used as negative control), and the wild-type TPC-1 cells served as blank control group. The transfection efficiency of FAT10 or FAT10ΔGG was detected by Western blotting, and cell proliferation was determined by cell counting kit-8 (CCK-8) assay. Cisplatin was used to induce cells after cells were transfected for 24 h, and the cell apoptotic rate was examined by flow cytometry. Results Western blotting showed a significantly increased expression of FAT10 protein in cervical carcinoma tissues as compared with that in normal cervical tissues. Over-expression of wild FAT10 in TPC-1 cells obviously promoted cell proliferation, but this promotion was significantly inhibited in cells transfected with its diglycine mutant. As compared with blank control group [(22.7±4.2)%] and negative control group [(24.1±3.8)%], the apoptotic rate was significantly reduced in wild FAT10 group [(10.9±2.0)%, P 0.05]. Conclusion FAT10 can promote cell proliferation and inhibit cell apoptosis through its carboxyl-terminal diglycine motif, and it may play an essential role in carcinogenesis and development of cancer. Key words: Thyroid carcinoma; Human leukocyte antigen-F associated transcript 10; Apoptosis

Embryonic develop-associated gene 1 is overexpressed and acts as a tumor promoter in thyroid carcinoma.

Embryonic develop-associated gene 1 (EDAG-1), a hematopoietic tissue-specific protein, is usually highly expressed in the placenta, fetal liver, bone marrow and leukemia cells, but the expression status in normal or solid tumor tissues is rarely reported. In this study, we found that EDAG-1 was up-regulated in thyroid carcinoma tissues and cells. Knockdown of EDAG-1 suppressed proliferation and enhanced cisplatin-induced apoptosis of thyroid carcinoma cells. We also demonstrated that knockdown of EDAG-1 inactivated the phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway in vitro and in vivo. Moreover, knockdown of EDAG-1 suppressed tumorigenesis of thyroid carcinoma in vivo. Taken together, these results suggest that EDAG-1 regulates the proliferation and apoptosis of thyroid carcinoma via the PI3K/Akt signaling pathway.

Effect of WW domail-containing oxidoreductase gene on apoptosis of papillary thyroid carcinoma cells and its mechanism

Objective To investigate the effects of WW domail-containing oxidoreductase (WWOX)-mediated apoptosis on papillary thyroid carcinoma in vitro and its possible mechanism. Methods A eukaryotic expression vector containing WWOX was transfected into papillary thyroid cancer cell line K1(recombinant plasmid group),and positive cell clones were selected and amplified. Synthesized small interfering RNA(siRNA) targeting WWOX(WWOX siRNA group) was transfected into TPC-1 cells.On the other hand, TPC-1 cells transfected with Lipofectamine 2000(liposomes control group)and vacant TPC-1 cells(blank control group) were used as controls.The expression of WWOX m RNA was detected by real-time quantitative reverse transcriptase-polymerase chain reaction(RT-qPCR).The effects of WWOX on apoptosis releated protein were analyzed by Western blotting. Results Recombinant plasmid group cells could steadily express WWOX mRNA, which was more than 4. 5 times higher than plasmid group and blank control group(P< 0. 05).The absorbance of TPC-1 cells decreased greatly after transfection with WWOX siRNA, which was 0. 2 times lower than in control groups(P< 0. 05).Forced expression of WWOX in K1 cells enhanced the expression of apoptosis releated protein. Conversely, knockdown of WWOX in TPC-1 cells using siRNA targeting WWOX decreased the expression of apoptosis releated protein. Conclusion WWOX can promote apoptosis of human PTC cells through a mechanism which may be assocoated with activation of the mitochondrial apoptosis pathway. Key words: WW domail-containing; Oxidoreductase gene; Apoptosis; Gene transfection

Galectin-3 leads to attenuation of apoptosis through Bax heterodimerization in human thyroid carcinoma cells.

Cancer cells survive escaping normal apoptosis and the blocks in apoptosis that keep cancer cells alive are promising candidates for targeted therapy. Galectin-3 (Gal-3) is, a member of the lectin family, which is involved in cell growth, adhesion, proliferation and apoptosis. It remains elusive to understand the role of Gal-3 on apoptosis in thyroid carcinoma cells. Here, we report that Gal-3 heterodimerizes Bax, mediated by the carbohydrate recognition domain (CRD) of Gal-3, leading to anti-apoptotic characteristic. Gal-3/Bax interaction was suppressed by an antagonist of Gal-3, in which in turn cells became sensitive to apoptosis. The data presented here highlight that Gal-3 is involved in the anti-apoptosis of thyroid carcinoma cells. Thus, it suggests that targeting Gal-3 may lead to an improved therapeutic modality for thyroid cancer.

Cl‐IB‐MECA enhances TRAIL‐induced apoptosis via the modulation of NF‐κB signalling pathway in thyroid cancer cells

Apoptosis is an endogenous process that can be a useful anti-cancer tool. This study aimed to investigate the effect of Cl-IB-MECA, adenosine receptor A3 agonist, on TRAIL-induced apoptosis of thyroid carcinoma cells. Cl-IB-MECA enhanced TRAIL-mediated apoptosis in FRO but not in ARO cells. This effect was correlated to higher expression levels of DR5 on FRO than ARO cells, that instead presented higher levels of decoy receptors, DcR1 and DcR2. To understand the cross-talk between the effect of Cl-IB-MECA and TRAIL, we evaluated the nuclear translocation of p65 and c-Rel. Since the dependency by NF-kappaB, TRAIL promoted the nuclear translocation of both p65 and c-Rel subunits. However, the addition of Cl-IB-MECA led to the predominant translocation of c-Rel after TRAIL addition. Furthermore, Bcl-2, cFLIP and pAkt were lower induced than caspase-3 and -9 in FRO cells. To discriminate a specific effect of TRAIL, we used tumour necrosis factor-alpha (TNF-alpha) with Cl-IB-MECA. In this case, no synergism was observed. In addition, the effect of Cl-IB-MECA was not A3 receptor-dependent since its antagonists, MRS1191 and FA385, failed to block Cl-IB-MECA activity on TRAIL-treated FRO cells. In conclusion, Cl-IB-MECA enhanced TRAIL-mediated apoptosis via NF-kappaB/c-Rel activation and DR5-dependent manner. This study may shed light on a potential drug cocktail that may prove useful as anti-cancer in an in vivo animal model.

Induction of BAG2 protein during proteasome inhibitor‐induced apoptosis in thyroid carcinoma cells

Proteasome inhibitors exhibit cytotoxic against tumours of different histology. However, the mechanism of apoptosis induction by these compounds remains unclear and is likely to be a complex cascade of events. Bcl-2-associated athanogene (BAG) family proteins are characterized by their property of interaction with a variety of partners involved in modulating the proliferation/death balance, including heat shock proteins (HSP), Bcl-2, Raf-1. The role of BAG family proteins in proteasome inhibition has not been elucidated. Effects of proteasome inhibitors on BAG2 expression were evaluated using real-time reverse transcription-polymerase chain reaction (RT-PCR). BAG2 expression was knocked down by small interfering RNAs (siRNA). Cell death was evaluated using Annexin V/propidium iodide staining and subsequent FACS. The proteasome inhibitors, MG132, PSI, lactacystin and epoxomicin, induced BAG2 at the transcriptional level. MG132-induced apoptosis was significantly suppressed by BAG2 knockdown using RNA interference. Our results suggest that BAG2 is a novel molecule induced by proteasome inhibition, which exhibits a pro-apoptotic property in death of thyroid cancer cells induced by proteasome inhibition.

Calcium-mediated activation of PI3K and p53 leads to apoptosis in thyroid carcinoma cells.

The molecular mechanism responsible for cadmium-induced cell death in thyroid cancer cells (FRO) is unknown. We demonstrated that apoptosis of FRO cells induced by cadmium was concentration and time dependent. Cadmium caused the rapid elevation of intracellular calcium and induced phosphorylation of Akt, p53, JNK, ERK and p38. Inhibition of PI3K/Akt attenuated the cadmium-induced apoptosis, but the inhibition of JNK inhibitor, ERK or p38 aggravated it, indicating that activation of PI3K/Akt was a pro-apoptosis signal in response to cadmium treatment, whereas the activation of stress-activated protein kinase JNK, ERK and p38 functioned as survival signals to counteract the cadmium-induced apoptosis. Buffering of the calcium response attenuated mitochondrial impairment, recovered the cadmium-activated Akt, p53, JNK, ERK and p38, and subsequently blocked the apoptosis. These results suggested that apoptosis induced by cadmium in FRO cells was initiated by the rapid elevation of intracellular calcium, followed by calcium-mediated activation of PI3K/Akt and mitochondrial impairment.

Effects of PPARγ agonists on cell survival and focal adhesions in a Chinese thyroid carcinoma cell line

Peroxisome proliferator-activated receptor gamma (PPARgamma) agonists cause cell death in several types of cancer cells. The aim of this study was to examine the effects of two PPARgamma agonists, ciglitazone and 15-deoxy-delta(12,14)-prostaglandin J2 (15dPGJ2), on the survival of thyroid carcinoma CGTH W-2 cells. Both ciglitazone and 15dPGJ2 decreased cell viability in a time- and dose-dependent manner. Cell death was mainly due to apoptosis, with a minor contribution from necrosis. Increased levels of active caspase 3, cleaved poly (ADP-ribose) polymerase (PARP), and cytosolic cytochrome-c were noted. In addition, ciglitazone and 15dPGJ2 induced detachment of CGTH W-2 cells from the culture substratum. Both the protein levels and immunostaining signals of focal adhesion (FA) proteins, including vinculin, integrin beta1, focal adhesion kinase (FAK), and paxillin were decreased after PPARgamma agonist treatment. Meanwhile, reduced phosphorylation of FAK and paxillin was noted. Furthermore, PPARgamma agonists induced expression of protein tyrosine phosphatase-PEST (PTP-PEST), and of phosphatase and tensin homologue deleted on chromosome ten (PTEN). The upregulation of these phosphatases might contribute to the dephosphorylation of FAK and paxillin, since pre-treatment with orthovanadate prevented PPARgamma agonist-induced dephosphorylation of FAK and paxillin. Perturbation of CGTH W-2 cells with anti-integrin beta1 antibodies induced FA disruption and apoptosis in the same cells, thus the downregulation of integrin beta1 by PPARgamma agonists resulted in FA disassembly and might induce apoptosis via anoikis. Our results suggested the presence of crosstalk between apoptosis and integrin-FA signaling. Moreover, upregulation and activation of PTEN was correlated with reduced phosphorylation of Akt, and this consequence disfavored cell survival. In conclusion, PPARgamma agonists induced apoptosis of thyroid carcinoma cells via the cytochrome-c caspase 3 and PTEN-Akt pathways, and induced necrosis via the PARP pathway.

Induction of annexin-1 during TRAIL-induced apoptosis in thyroid carcinoma cells

Induction of annexin-1 during TRAIL-induced apoptosis in thyroid carcinoma cells

Regulation of Apo2L/Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis in Thyroid Carcinoma Cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)/Apo2 ligand selectively kills neoplastic cells, including thyroid carcinoma cells (Mitsiades et al: Thyroid carcinoma cells are resistant to FAS-mediated apoptosis but sensitive to tumor necrosis factor-related apoptosis-inducing ligand. Cancer Res 2000, 60:4122-41299). We investigated the mechanisms regulating Apo2L/TRAIL-induced apoptosis in thyroid carcinoma cells, as well as the impact of insulin-like growth factor (IGF)-1, interferon-gamma, and TNF-alpha. We found that the emergence of resistance to Apo2L/TRAIL, after prolonged incubation with this cytokine, was associated with increased levels of FLICE inhibitory protein (FLIP), and was overcome by cycloheximide and bisindolylmaleimide, that specifically down-regulated FLIP expression, as well as by transfection of a FLIP anti-sense oligonucleotide. IGF-1 activated Akt; up-regulated the caspase inhibitors FLIP, cIAP-2, XIAP, and survivin; and attenuated Apo2L/TRAIL-induced apoptosis. This effect was inhibited by the IGF-1 receptor neutralizing antibody aIR3, the PI-3K inhibitor wortmannin, and the heat shock protein-90 chaperone inhibitor geldanamycin. Transfection of constitutively active Akt protected from TRAIL. Conversely, interferon-gamma and TNF-alpha had a sensitizing effect. We conclude that FLIP may negatively regulate Apo2L/TRAIL-induced apoptosis in thyroid carcinomas. Microenvironmental paracrine survival factors, such as IGF-1, up-regulate caspase inhibitors, including FLIP, and protect from Apo2L/TRAIL in a PI-3K/Akt-dependent manner. T helper-1 cytokines and compounds that selectively abrogate the IGF-1 signaling pathway may be helpful adjunct agents in Apo2L/TRAIL-based anti-cancer therapeutic regimens.

Fas ligand expression in thyroid carcinomas: a potential mechanism of immune evasion.

Fas ligand (FasL) induces apoptosis by cross-linking the Fas receptor and is expressed by cells of the immune system. Recently, FasL was found in malignant tumors, suggesting that it helps them escape immune surveillance by eliminating infiltrating lymphocytes. We investigated the presence of FasL immunohistochemically in 48 thyroid carcinomas and by Western blotting and RT-PCR in 5 thyroid carcinoma cell lines. We found that in contrast to normal thyroid tissue, FasL was highly expressed in all papillary, follicular, and Huerthle carcinomas. Medullary carcinomas lacked or had minimal FasL expression. In papillary carcinomas, high levels of expression correlated independently with aggressive histology and unfavorable clinical presentation. FasL was also present in all thyroid cell lines. Thyroid carcinoma cells killed Fas-sensitive targets in a FasL-dependent manner in a coculture experiment. Cross-linking of Fas induced apoptosis in thyroid carcinoma cells only in the presence of cycloheximide. We conclude that FasL is specifically expressed in thyroid carcinomas of follicular epithelial origin, may help them evade the immune system, and may have prognostic implications in papillary carcinoma, as it is associated with a more aggressive phenotype. Thyroid carcinoma cells avoid Fas-mediated suicide possibly by expressing an inhibitor of the Fas apoptotic pathway.