Effect of valproic acid on miRNAs affecting histone deacetylase in a model of anaplastic thyroid cancer

Background

Thyroid cancer is the most common malignant tumor of the endocrine system seen in the thyroid gland. More than 90% of thyroid cancers comprise papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). Although anaplastic thyroid carcinoma (ATC) accounts for less than 2% of thyroid cancer. But patients’ lifespan after diagnosis is about 6 months. Surgical interventions, radioactive iodine use, and chemotherapy are not sufficient in the treatment of ATC, so alternative therapies are needed.

Methods and results

The WST-1 assay test was performed to evaluate the anti-proliferative effects of Valproic acid (VPA). Also, the effect of VPA on miRNAs affecting histone deacetylase was determined by Quantitative RT-PCR. In the SW1736 cell line, IC50 dose for VPA was found 1.6 mg/ml. In our study, the level of oncogenic genes expression in cells treated with VPA, including miR-184, miR-222-5p, miR-124-3p, and miR-328-3p, decreased. Also, the expression of tumor inhibitory genes including miR-323-5p, miR-182-5p, miR-138-5p, miR-217, miR-15a-5p, miR-29b-3p, miR-324-5p and miR-101-5p increased significantly.

Conclusions

VPA can ad-just countless gene expression patterns, including microRNAs (miRNAs), by targeting histone deacetylase (HDAC). However, further studies are required for more accurate results.

     

Stem cell biology in thyroid cancer: Insights for novel therapies

Currently, thyroid cancer is one of the most common endocrine cancer in the United States. A recent involvement of sub-population of stem cells, cancer stem cells, has been proposed in different histological types of thyroid cancer. Because of their ability of self-renewal and differentiation into various specialized cells in the body, these putative cells drive tumor genesis, metastatic activity and are responsible to provide chemo- and radioresistant nature to the cancer cells in the thyroid gland. Our Review was conducted from previously published literature to provide latest apprises to investigate the role of embryonic, somatic and cancer stem cells, and discusses the hypothesis of epithelial-mesenchymal transition. Different methods for their identification and isolation through stemness markers using various in vivo and in vitro methods such as flow cytometry, thyrosphere formation assay, aldehyde dehydrogenase activity and ATP-binding cassette sub-family G member 2 efflux-pump mediated Hoechst 33342 dye exclusion have been discussed. The review also outlines various setbacks that still remain to target these tumor initiating cells. Future perspectives of therapeutic strategies and their potential to treat advanced stages of thyroid cancer are also disclosed in this review.     

3,3'-Diindolylmethane, a cruciferous vegetable derived synthetic anti-proliferative compound in thyroid disease

Considerable epidemiological evidence exists to link thyroid disease with differing patterns of dietary consumption, in particular, cruciferous vegetables. We have been studying the anti-thyroid cancer (TCa) activity of indole-3-carbinol (I3C) found in cruciferous vegetables and its acid catalyzed dimer, 3,3'-diindolylmethane (DIM). There are no studies as yet to elucidate the effect of these compounds on the altered proliferative patterns in goiter or thyroid neoplasia. In this study, we tested the anti-proliferative effects of I3C and DIM on four different thyroid cancer cell lines representative of papillary (B-CPAP and 8505-C) and follicular carcinoma of the thyroid (CGTH-W-1 and ML-1), and primary human goiter cells. Cell survival and IC50 values for I3C and DIM were calculated by the XTT assay and cell cycle distribution analysis was done by flow cytometry. DIM was found to be a better anti-proliferative agent than I3C in both papillary and follicular TCa resulting in a greater cytotoxic effect at a concentration over three fold lower than predicted by the molar ratio of DIM and I3C. The anti-proliferative activity of DIM in follicular TCa was mediated by a G1 arrest followed by induction of apoptosis. DIM also inhibited the growth of primary goiter cells by 70% compared to untreated controls. Contrary to traditional belief that cruciferous vegetables are "goitrogenic", DIM has anti-proliferative effects in glandular thyroid proliferative disease. Our preclinical studies provide a strong rationale for the clinical exploration of DIM as an adjuvant to surgery in thyroid proliferative disease.     

Identification and functional characterization of isocitrate dehydrogenase 1 (IDH1) mutations in thyroid cancer

Mutations in the genes for isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) have been recently identified in glioblastoma. In the present study, we investigated IDH1 and IDH2 mutations in follicular thyroid cancer (FTC) and anaplastic thyroid cancer (ATC), with the latter, like glioblastoma, having a rapidly aggressive and lethal clinical course. By direct genomic DNA sequencing, we analyzed exon 4 of the IDH1 and IDH2 genes that harbored the mutation hot spots codon 132 and 172 of the two genes in glioblastoma, respectively, in 12 thyroid cancer cell lines, 20 FTC, and 18 ATC tumor samples. A novel homozygous G367A IDH1 mutation, resulting in a G123R amino acid change in codon 123, was identified in a case of ATC. A previously described IDH1 V71I mutation was found in a case of FTC and a case of ATC and no mutations were found in the cell lines. The overall prevalence of mutations was thus 1/20 (5%) in FTC and 2/18 (11%) in ATC. We did not find mutation in the IDH2 gene in these thyroid cancer cell lines and tumor samples. Sequence alignment analysis of 16 species revealed that the novel IDH1 G123R mutation was located in a highly conserved region, raising the possibility of a serious functional consequence as could also be predicted by the occurrence of a positively charged amino acid from this mutation. To test this, we created a G123R mutant by site-directed mutagenesis and demonstrated a decreased enzymatic activity of IDH1, similar to the expected reduction in the enzymatic activity of the previously described R132H IDH1 mutant measured as a control. Thus, functionally relevant IDH1 mutations can also occur in thyroid cancer, particularly ATC, suggesting a potential tumorigenic role of the IDH1 system that could represent a new therapeutic target for thyroid cancer.     

Molecular nuclear therapies for thyroid carcinoma

Thyroid cancer, divided in the subvarieties of papillary and follicular carcinoma, together also called differentiated thyroid carcinoma (DTC), medullary thyroid carcinoma (MTC) and anaplastic thyroid carcinoma (ATC), is the most common endocrine malignancy. Over the course of the last seven decades multiple molecular nuclear therapies have been tried to treat the various varieties of thyroid cancer. The sodium iodine symporter (NIS) substrate I-131 is a well known and extremely successful agent to treat DTC, but is not successful in treating other thyroid cancer varieties and some de-differentiated DTC tumors. An alternative to I-131 are radioactively labeled somatostatin analogues, which have predominantly been used to target MTC, but may also be effective in some DTC cases. In experimental preclinical studies the re-induction of NIS expression or transfection with recombinant NIS shows some promise for the treatment of ATC and dedifferentiated DTC. Furthermore, several other potential radioactive NIS substrates are developed. In this review, we will extensively discuss the aforementioned established therapeutic modalities and promising new concepts in molecular nuclear therapy of thyroid carcinoma.     

青岛地区某医院12年甲状腺癌发病模式变迁

目的:探讨青岛地区某医院12年甲状腺癌的发病趋势和病理类型分布。方法:回顾性分析2001-2012年于青岛大学附属医院行手术切除的甲状腺癌患者的发病年龄、性别比例、手术数量以及病理类型构成比的变化。结果:12年来手术治疗甲状腺癌2421例,其中乳头状癌(PTC)占94.13%,滤泡状癌(FTC)占3.02%,髓样癌(MTC)占2.15%,未分化癌(ATC)占0.70%。甲状腺癌手术数量呈逐年递增趋势,尤以近4年升高显著,其病理类型以PTC为主,构成比例由79.63%上升至97.47%。四类甲状腺癌均以女性多见(男女比例1:1.38-1:4.37)。甲状腺癌的平均确诊年龄为46.80岁,PTC最低(46.48岁),ATC最高(64.25岁)。结论:青岛地区甲状腺癌发病数量呈逐年递增趋势,PTC是最常见的病理类型,其构成比例上升明显,其他类型相对下降。PTC的发病可能与高碘有关。     

MiR-223 inhibitor suppresses proliferation and induces apoptosis of thyroid cancer cells by down-regulating aquaporin-1

To investigate the effect of miR-223 on thyroid cancer cells, further to study its potential mechanisms. The difference in miR-223 expression between normal thyroid Nthy-ori3-l cells and thyroid cancer SW579 cells was detected by PCR. The miR-223 overexpression and silencing vector transfection were verified by qRT-PCR. To further investigate the role of miR-223 in AQP-1, the AQP-1 siRNA vector was transfected on the basis of transfection of miR-223 inhibitor vector. The cell proliferation was detected by plate cloning, MTT, and cellular immunofluorescence assays. Cell cycle and apoptosis were detected by flow cytometry. Western blot was used to detect the expression of AQP-1 protein. The expression of miR-223 in SW579 cells was higher than that in normal cells. After transfection with miR-223 mimic, miR-223 expression was increased in SW579 cells. MiR-223 inhibitor transfection can inhibit SW579 cells proliferation, promote apoptosis, and inhibit cell cycle G0/G1 arrest. The SW579 cells proliferation was decreased, and the apoptosis rate was increased after transfection of AQP-1 silencing vector. Compared with the AQP-1 siRNA group, the SW579 cells proliferation rate was further reduced, and the apoptosis rate was significantly increased after co-transfection of miR-223 silencing vector and AQP-1 silencing vector. AQP-1 protein was highly expressed in SW579 cells, and miR-223 inhibitor can down-regulate the expression of APQ-1 protein. The expression AQP-1 protein was significantly reduced after transfected with AQP-1 silencing vector. Inhibition of miR-223 expression could suppress proliferation and promote apoptosis of SW579, and its mechanism is related to down-regulation of APQ-1 protein expression.     

Identification of a distinct side population of cancer cells in the Cal-51 human breast carcinoma cell line

“Side population” (SP) cells, which pump out the fluorescent dye H33342 via the ABCG2 transporter, define a putative stem/progenitor cell population in the mammary gland. Breast cancer SP cells recently isolated from the MCF-7 cell line possess similar properties and may represent stem cell-like cancer cells. This study extends SP cell analysis to a broad panel of human breast cancer cell lines and investigates the expression of differentiation-associated markers in isolated cancer SP cells. Expression of ABCG2 was determined in 16 breast cancer cell lines by quantitative RT-PCR, Western blotting and immunohistochemistry. Subsequently, all cell lines were screened for the presence of SP cells. Human breast cancer cell lines commonly express ABCG2. ABCG2-immunoreactivity was clearly restricted to rare cancer cells in several cell lines including Cal-51. Analysis of H33342-labeled Cal-51 cells revealed a small fraction of putative SP cells accounting for one percent of all cells. The genuine nature of Cal-51 SP cells was unambiguously verified by demonstrating a 30-fold increased ABCG2-expression in isolated Cal-51 SP cells. During in vitro expansion, Cal-51 SP cells generated heterologous non-SP (NSP) cells and ABCG2-expression declined dramatically. In contrast, NSP cells failed to sustain proliferation. Freshly isolated Cal-51 SP cells also exhibited increased expression of Muc1 and CALLA. Noteworthy, non-malignant mammary epithelial SP cells lack these differentiation markers, highlighting fundamental differences between non-malignant and breast cancer-derived SP cells. In summary, we established Cal-51 SP cells as a novel in vitro model to study differential gene expression in breast cancer-derived SP and NSP cells.     

Genome-wide expression analysis suggests a crucial role of dysregulation of matrix metalloproteinases pathway in undifferentiated thyroid carcinoma

Background

Thyroid cancer (TC) is the most common malignant cancer of the Endocrine System. Histologically, there are three main subtypes of TC: follicular, papillary and anaplastic. Diagnosing a thyroid tumor subtype with a high level of accuracy and confidence is still a difficult task because genetic, molecular and cellular mechanisms underlying the transition from differentiated to undifferentiated thyroid tumors are not well understood.A genome-wide analysis of these three subtypes of thyroid carcinoma was carried out in order to identify significant differences in expression levels as well as enriched pathways for non-shared molecular and cellular features between subtypes.

Results

Inhibition of matrix metalloproteinases pathway is a major event involved in thyroid cancer progression and its dysregulation may result crucial for invasiveness, migration and metastasis. This pathway is drastically altered in ATC while in FTC and PTC, the most important pathways are related to DNA-repair activation or cell to cell signaling events.

Conclusion

A progression from FTC to PTC and then to ATC was detected and validated on two independent datasets. Moreover, PTX3, COLEC12 and PDGFRA genes were found as possible candidates for biomarkers of ATC while GPR110 could be tested to distinguish PTC over other tumor subtypes. The genome-wide analysis emphasizes the preponderance of pathway-dysregulation mechanisms over simple gene-malfunction as the main mechanism involved in the development of a cancer phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1372-0) contains supplementary material, which is available to authorized users.     

Mechanisms and pathogenesis of thyroid cancer in animals and man

The transformation of the normal fully differentiated thyroid follicular cell to the rapidly growing undifferentiated anaplastic thyroid carcinoma cell involves a number of stages which have been defined morphologically and are now being related to various growth pathways and to molecular biological defects. The two main factors involved in this transformation are growth stimulation and mutagenesis. Growth stimulation alone, through elevated TSH, can lead to the development of thyroid tumours, usually benign, and retaining TSH dependency in some cases. Mutagens alone, if growth is suppressed, do not produce tumours, the combination of mutagens and increased growth is a potent carcinogenic regime. Non-genotoxic carcinogenesis in the thyroid involves growth, without mutagenesis the agent often causes this through affecting one component of thyroid hormone synthesis or metabolism, leading to a fall in thyroid hormone levels and a rise in TSH. Growth stimulation increases the rate of cell division, and therefore increases the chance of a mutation. Continued growth increases the change of subsequent events, in particular loss of heterozygosity in a tumour suppressor gene. The main oncogenes involved in human thyroid carcinogens are ras in the follicular tumour pathway, and ret in the papillary carcinoma pathway. p53 is involved in the progression of either papillary or follicular adenoma to an undifferentiated carcinoma. In experimental thyroid carcinogenesis, ras is again involved, with a link between the mutagenic agent used and the type of ras gene showing mutation. Analysis of the involvement of different growth factors and oncogenes in thyroid carcinogenesis suggests that genes related to the two receptors concerned with normal TSH stimulated growth, TSH receptor and the IGF1 recpptor may be involved in the progression of thyroid tumours of follicular pathology. Several tyrosine kinase receptors with unknown ligands or of uncertain physiological function are linked to papillary carcinoma. The recent large increase in papillary carcinoma of the thyroid in children exposed to fallout from the Chernobyl nuclear accident underlines the importance of understanding the pathobiology of thyroid neoplasia.     

Altered expression of key players in vitamin D metabolism and signaling in malignant and benign thyroid tumors

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), the active form of vitamin D, mediates antitumor effects in various cancers. The expression of key players in vitamin D signaling in thyroid tumors was investigated. Vitamin D receptor (VDR) and CYP27B1 and CYP24A1 (respectively activating and catabolizing vitamin D) expression was studied (RT-PCR, immunohistochemistry) in normal thyroid, follicular adenoma (FA), differentiated thyroid cancer (DTC) consisting of the papillary (PTC) and follicular (FTC) subtype, and anaplastic thyroid cancer (ATC). VDR, CYP27B1, and CYP24A1 expression was increased in FA and DTC compared with normal thyroid. However, in PTC with lymph node metastasis, VDR and CYP24A1 were decreased compared with non-metastasized PTC. In ATC, VDR expression was often lost, whereas CYP27B1/CYP24A1 expression was comparable to DTC. Moreover, ATC with high Ki67 expression (>30%) or distant metastases at diagnosis was characterized by more negative VDR/CYP24A1/CYP27B1 staining. In conclusion, increased expression of key players involved in local 1,25(OH)(2)D(3) signaling was demonstrated in benign and differentiated malignant thyroid tumors, but a decrease was observed for local nodal and especially distant metastasis, suggesting a local antitumor response of 1,25(OH)(2)D(3) in early cancer stages. These findings advocate further studies with 1,25(OH)(2)D(3) and analogs in persistent and recurrent iodine-refractory DTC.     

Angiopoietin 1 (Ang-1), angiopoietin 2 (Ang-2) and Tie-2 (a receptor tyrosine kinase) concentrations in peripheral blood of patients with thyroid cancers

There are limited and conflicting studies investigating the role of the angiopoietin family in human thyroid cancer development and progression. We have investigated cytokines angiopoietin-1, -2 and their receptor (Tie-2), known to be involved in angiogenesis, in the serum of 52 thyroid cancer patients (21 cases of papillary cancers, PTC; 8 follicular cancers, FTC; 12 medullary cancers, MTC and 11 anaplastic cancers, ATC), using ELISA assays. The control consisted of 27 healthy volunteers. Statistically significant lower concentrations of Ang-1 were found in patients with thyroid cancers as compared with the control (p<0.003). The levels of Ang-2 and Tie-2 did not differ significantly between thyroid cancer patients and control. We have also compared the results of Ang-1, Ang-2, and Tie-2 determinations obtained in different histopathological subgroups of cancer patients. These results revealed lower Ang-1 concentrations in ATC (p<0.05), MTC (p<0.02), FTC (p<0.01) and in PTC patients (p<0.05) than control. We have also observed lower Ang-2 concentration in PTC patients (p<0.03) and Tie-2 in FTC patients (p<0.02 ) in comparison to controls. In conclusion, the Angs/Tie-2 system dysfunction may play an important role in thyroid cancerogenesis and decreased concentration of Ang-1 in serum can be a useful additional biomarker for the presence of thyroid cancers.     

Antithyroid cancer effects of human neural stem cells expressing therapeutic genes on anaplastic thyroid cancer cells

Stem cells that express therapeutic proteins have been identified to have an anticancer effects on various types of cancer. In the present study study, human neural stem cells (hNSCs) that were genetically engineered to express cytosine deaminase (CD) and human interferon-β (IFN-β) were used for anaplastic thyroid cancer (ATC) treatment owing to their tumor-tropic properties and therapeutic effects. CD is an enzyme that converts 5-fluorocytosine (5-FC), a prodrug, to 5-fluorouracil (5-FU) which is a medication to suppress tumor growth through DNA synthesis inhibition. Also, IFN-β suppresses tumor growth by the induction of apoptotic process. In water soluble tetrazolium salt (WST) assay, SNU-80 cells which are human female ATC cells were cocultured with three cell types including engineered hNSCs such as HB1.F3, HB1.F3.CD, and HB1.F3.CD.IFN-β cells on transwells and treated with 5-FC for 72 hours. Finally, the SNU-80 cell viability was reduced by the coculture with HB1.F3.CD and HB1.F3.CD.IFN-β cells. In dichlorofluorescein diacetate (DCF-DA) and TdT-mediated dUTP nick-end labeling (TUNEL) assays, the production of reactive oxygen species (ROS) and the number of apoptotic cells were increased by HB1.F3.CD and HB1.F3.CD.IFN-β cells in the presence of 5-FC. In Western blot assay, ROS, and apoptosis-related genes were increased in SNU-80 cells when they were cocultured with HB1.F3.CD and HB1.F3.CD.IFN-β cells. In transwell migration assay, hNSCs selectively migrated to SNU-80 cells because hNSCs interacted with chemoattractant factors like SDF-1α, uPAR, and CCR2 secreted by SNU-80 cells. Taken together, engineered hNSCs were revealed to selectively migrate to ATC cells and to inhibit growth as well as to induce apoptosis of ATC cells via ROS production through the actions of transgenes such as CD and IFN-β. Therefore, these engineered hNSCs can be promising candidates for the treatment of metastatic ATC.     

Overexpression of RYBP inhibits proliferation,invasion, and chemoresistance to cisplatin in anaplastic thyroid cancer cells via the EGFR pathway

Ring1 and YY1 binding protein (RYBP), a new member of the polycomb group protein family, has been reported to play an important role in various biological processes. Recently, more and more studies have demonstrated an implication of RYBP in cancer development. However, the specific role of RYBP in anaplastic thyroid cancer (ATC) remains unknown. In this study, we investigated for the first time the expression pattern and biological functions of RYBP in ATC. We showed that RYBP was lowly expressed in ATC tissues and cell lines. We also found that overexpression of RYBP inhibited ATC cell proliferation, invasion, and cisplatin resistance. Furthermore, we observed that upregulation of RYBP decreased the phosphorylation of EGFR and ERK1/2 in ATC cells. Taken together, our data indicated that RYBP might be considered as a promising therapeutic target for the treatment of ATC.     

Thyroid hormone is a MAPK-dependent growth factor for thyroid cancer cells and is anti-apoptotic

Thyroid hormone (l-thyroxine, T(4), or 3,5,3'-triiodo-l-thyronine, T(3)) treatment of human papillary and follicular thyroid cancer cell lines resulted in enhanced cell proliferation, measured by proliferating cell nuclear antigen (PCNA). Thyroid hormone also induced activation of the Ras/MAPK (ERK1/2) signal transduction pathway. ERK1/2 activation and cell proliferation caused by thyroid hormone were blocked by an iodothyronine analogue, tetraiodothyroacetic acid (tetrac), that inhibits binding of iodothyronines to the cell surface receptor for thyroid hormone on integrin alphaVbeta3. A MAPK cascade inhibitor at MEK, PD 98059, also blocked hormone-induced cell proliferation. We then assessed the possibility that thyroid hormone is anti-apoptotic. We first established that resveratrol (10 microM), a pro-apoptotic agent in other cancer cells, induced p53-dependent apoptosis and c-fos, c-jun and p21 gene expression in both papillary and follicular thyroid cancer cells. Induction of apoptosis by the stilbene required Ser-15 phosphorylation of p53. Resveratrol-induced gene expression and apoptosis were inhibited more than 50% by physiological concentrations of T(4). T(4) activated MAPK in the absence of resveratrol, caused minimal Ser-15 phosphorylation of p53 and did not affect c-fos, c-jun and p21 mRNA abundance. Thus, plasma membrane-initiated activation of the MAPK cascade by thyroid hormone promotes papillary and follicular thyroid cancer cell proliferation in vitro.     

Utility of a PI3K/mTOR Inhibitor (NVP-BEZ235) for Thyroid Cancer Therapy

Background

We assessed the utility of the dual PI3K/mTOR inhibitor NVP-BEZ235 (BEZ235) as single agent therapy and in combination with conventional chemotherapy for thyroid cancer.

Methodology/Principal Findings

Eight cell lines from four types of thyroid cancer (papillary, follicular, anaplastic, medullary) were studied. The cytotoxicity of BEZ235 and five conventional chemotherapeutic agents alone and in combination was measured using LDH assay. Quantitative western blot assessed expression of proteins associated with cell cycle, apoptosis and signaling pathways. Cell cycle distribution and apoptosis were measured by flow cytometry. Murine flank anaplastic thyroid cancers (ATC) were treated with oral BEZ235 daily. We found that BEZ235 effectively inhibited cell proliferation of all cancer lines, with ATC exhibiting the greatest sensitivity. BEZ235 consistently inactivated signaling downstream of mTORC1. BEZ235 generally induced cell cycle arrest at G0/G1 phase, and also caused apoptosis in the most sensitive cell lines. Baseline levels of p-S6 ribosomal protein (Ser235/236) and p27 correlated with BEZ235 sensitivity. Growth of 8505C ATC xenograft tumors was inhibited with BEZ235, without any observed toxicity. Combination therapy of BEZ235 and paclitaxel consistently demonstrated synergistic effects against ATC in vitro.

Conclusions

BEZ235 as a single therapeutic agent inhibits thyroid cancer proliferation and has synergistic effects in combination with paclitaxel in treating ATC. These findings encourage future clinical trials using BEZ235 for patients with this fatal disease.     

Blocks to thyroid cancer cell apoptosis can be overcome by inhibition of the MAPK and PI3K/AKT pathways

Current treatment for recurrent and aggressive/anaplastic thyroid cancers is ineffective. Novel targeted therapies aimed at the inhibition of the mutated oncoprotein BRAF^V600E have shown promise in vivo and in vitro but do not result in cellular apoptosis. TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a tumor-selective manner by activating the extrinsic apoptotic pathway. Here, we show that a TRAIL-R2 agonist antibody, lexatumumab, induces apoptosis effectively in some thyroid cancer cell lines (HTh-7, TPC-1 and BCPAP), while more aggressive anaplastic cell lines (8505c and SW1736) show resistance. Treatment of the most resistant cell line, 8505c, using lexatumumab in combination with the BRAF^V600E inhibitor, PLX4720, and the PI3K inhibitor, {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002, (triple-drug combination) sensitizes the cells by triggering both the extrinsic and intrinsic apoptotic pathways in vitro as well as 8505c orthotopic thyroid tumors in vivo. A decrease in anti-apoptotic proteins, pAkt, Bcl-xL, Mcl-1 and c-FLIP, coupled with an increase in the activator proteins, Bax and Bim, results in an increase in the Bax to Bcl-xL ratio that appears to be critical for sensitization and subsequent apoptosis of these resistant cells. Our results suggest that targeting the death receptor pathway in thyroid cancer can be a promising strategy for inducing apoptosis in thyroid cancer cells, although combination with other kinase inhibitors may be needed in some of the more aggressive tumors initially resistant to apoptosis.     

Utility of a Histone Deacetylase Inhibitor (PXD101) for Thyroid Cancer Treatment

Background

We evaluated the therapeutic effects of the histone deacetylase inhibitor PXD101 alone and in combination with conventional chemotherapy in treating thyroid cancer.

Methodology/Principal Findings

We studied eight cell lines from four types of thyroid cancer (papillary, follicular, anaplastic and medullary). The cytotoxicity of PXD101 alone and in combination with three conventional chemotherapeutic agents (doxorubicin, paclitaxel and docetaxel) was measured using LDH assay. Western blot assessed expression of acetylation of histone H3, histone H4 and tubulin, proteins associated with apoptosis, RAS/RAF/ERK and PI3K/AKT/mTOR signaling pathways, DNA damage and repair. Apoptosis and intracellular reactive oxygen species (ROS) were measured by flow cytometry. Mice bearing flank anaplastic thyroid cancers (ATC) were daily treated with intraperitoneal injection of PXD101 for 5 days per week. PXD101 effectively inhibited thyroid cancer cell proliferation in a dose-dependent manner. PXD101 induced ROS accumulation and inhibited RAS/RAF/ERK and PI3K/mTOR pathways in sensitive cells. Double-stranded DNA damage and apoptosis were induced by PXD101 in both sensitive and resistant cell lines. PXD101 retarded growth of 8505C ATC xenograft tumors with promising safety. Combination therapy of PXD101with doxorubicin and paclitaxel demonstrated synergistic effects against four ATC lines in vitro.

Conclusions

PXD101 represses thyroid cancer proliferation and has synergistic effects in combination with doxorubicin and paclitaxel in treating ATC. These findings support clinical trials using PXD101 for patients with this dismal disease.