Catia Mio

Synergy between HDAC and PARP Inhibitors on Proliferation of a Human Anaplastic Thyroid Cancer-Derived Cell Line

Anaplastic thyroid carcinoma (ATC) is a very aggressive human malignancy, having a marked degree of invasiveness and no features of thyroid differentiation. It is known that either HDAC inhibitors or PARP inhibitors have antiproliferative effects on thyroid cancer cells. Therefore, in this study the possible synergy between the two types of compounds has been investigated. The ATC-derived cell line SW1736 has been treated with the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) and the PARP inhibitor PJ34, alone or in combination. In terms of cell viability, the combination index value was always lower than 1 at various tested dosages, indicating, therefore, synergy in a wide range of doses for both compounds. Synergy was also observed in induction of apoptosis. In terms of thyroid-specific gene expression, synergy was observed for TSHR mRNA levels but not for NIS, TTF1, TTF2, and PAX8 mRNA levels. Altogether, these data suggest that the combined use of HDAC and PARP inhibitors may be a useful strategy for treatment of ATC.

MCM5 as a target of BET inhibitors in thyroid cancer cells

Anaplastic thyroid carcinoma (ATC) is an extremely aggressive thyroid cancer subtype, refractory to the current medical treatment. Among various epigenetic anticancer drugs, bromodomain and extra-terminal inhibitors (BETis) are considered to be an appealing novel class of compounds. BETi target the bromodomain and extra-terminal of BET proteins that act as regulators of gene transcription, interacting with histone acetyl groups. The goal of this study is to delineate which pathway underlies the biological effects derived from BET inhibition, in order to find new potential therapeutic targets in ATC. We investigated the effects of BET inhibition on two human anaplastic thyroid cancer-derived cell lines (FRO and SW1736). The treatment with two BETis, JQ1 and I-BET762, decreased cell viability, reduced cell cycle S-phase, and determined cell death. In order to find BETi effectors, FRO and SW1736 were subjected to a global transcriptome analysis after JQ1 treatment. A significant portion of deregulated genes belongs to cell cycle regulators. Among them, MCM5 was decreased at both mRNA and protein levels in both tested cell lines. Chromatin immunoprecipitation (ChIP) experiments indicate that MCM5 is directly bound by the BET protein BRD4. MCM5 silencing reduced cell proliferation, thus underlining its involvement in the block of proliferation induced by BETis. Furthermore, MCM5 immunohistochemical evaluation in human thyroid tumor tissues demonstrated its overexpression in several papillary thyroid carcinomas and in all ATCs. MCM5 was also overexpressed in a murine model of ATC, and JQ1 treatment reduced Mcm5 mRNA expression in two murine ATC cell lines. Thus, MCM5 could represent a new target in the therapeutic approach against ATC.

Identification of tumorigenesis-related mRNAs associated with RNA-binding protein HuR in thyroid cancer cells

RNA binding proteins (RBPs) play a central role in cell physiology and pathology. Among them, HuR is a nuclear RBP, which shuttles to the cytoplasm to allow its RNA targets processing. HuR over-expression and delocalization are often associated to cell transformation. Numerous cancers display increased HuR protein levels and its high cytoplasmic levels has been associated with a worse prognosis. In our study, we first evaluated HuR expression in normal and cancer thyroid tissues and then evaluated its function in thyroid cell lines. HuR is over-expressed in all thyroid tumor tissues; high cytoplasmic levels are detected in all thyroid carcinomas. HuR silencing decreased cell viability and determined apoptotic cell death, in a non-tumorigenic (Nthy-ori-3.1) and a tumorigenic (BCPAP) thyroid cell line. Global transcriptome analysis indicated that HuR silencing, though having similar biological effects, induces distinct gene expression modifications in the two cell lines. By using the RIP-seq approach, the HuR-bound RNA profiles of different thyroid cell lines were evaluated. We show that in distinct cell lines HuR-bound RNA profiles are different. A set of 114 HuR-bound RNAs distinguishing tumorigenic cell lines from the non-tumorigenic one was identified. Altogether, our data indicate that HuR plays a role in thyroid tumorigenesis. Moreover, our findings are a proof of concept that RBP targets differ between cells with the same origin but with distinct biological behavior.

Epigenetic bivalent marking is permissive to the synergy of HDAC and PARP inhibitors on TXNIP expression in breast cancer cells

Studies on stem cell differentiation led to the identification of paused genes, characterized by the contemporary presence of both activator and repressor epigenetic markers (bivalent marking). TXNIP is an oncosuppressor gene the expression of which was reduced in breast cancer. In the present study, we evaluated whether the concept of epigenetic bivalent marking can be applied to TXNIP gene in breast cancer cells. Using chromatin immunoprecipitation (ChIP), three histone modifications were investigated: two associated with transcriptional activation, lysines 9-14 acetylation of H3 histone (H3K9K14ac) and lysine 4 trimethylation of H3 histone (H3K4me3), and one associated with transcriptional silencing, lysine 27 trimethylation of H3 histone (H3K27me3). According to the bivalent marking model, TXNIP gene appears to be paused in MDA157 cells (markers of active and repressed transcription are present), but are definitively silenced in MDA468 cells (presence of only markers of transcription repression). This was proven by evaluating TXNIP mRNA and protein levels after the treatment of cell lines with a histone deacetylase inhibitor (SAHA) and a poly-ADP-ribose polymerases inhibitor (PJ34). In MDA157 cells, SAHA and PJ34 showed a synergistic effect: a large increment was observed in TXNIP mRNA and protein levels. By contrast, in MDA468 cells, synergy between the two compounds was not observed. Therefore, the pausing epigenetic signature was permissive for synergy between SAHA and PJ34 on TXNIP gene expression. The synergy between SAHA and PJ34 on TXNIP expression was associated with variation in cell viability and apoptosis. In MDA157 cells, but not in MDA468 cells, combined treatment of SAHA and PJ34 induced a decrease in cell viability and an increase of apoptosis. Thus, our data support the hypothesis that TXNIP is an effective target for the treatment of breast cancer.

Expression of PAX8 target genes in papillary thyroid carcinoma

PAX8 is a thyroid-specific transcription factor whose expression is dysregulated in thyroid cancer. A recent study using a conditional knock-out mouse model identified 58 putative PAX8 target genes. In the present study, we evaluated the expression of 11 of these genes in normal and tumoral thyroid tissues from patients with papillary thyroid cancer (PTC). ATP1B1, GPC3, KCNIP3, and PRLR transcript levels in tumor tissues were significantly lower in PTCs than in NT, whereas LCN2, LGALS1 and SCD1 expression was upregulated in PTC compared with NT. Principal component analysis of the expression of the most markedly dysregulated PAX8 target genes was able to discriminate between PTC and NT. Immunohistochemistry was used to assess levels of proteins encoded by the two most dyregulated PAX8 target genes, LCN2 and GPC3. Interestingly, GPC3 was detectable in all of the NT samples but none of the PTC samples. Collectively, these findings point to significant PTC-associated dysregulation of several PAX8 target genes, supporting the notion that PAX8-regulated molecular cascades play important roles during thyroid tumorigenesis.

Effects of BP-14, a novel cyclin-dependent kinase inhibitor, on anaplastic thyroid cancer cells

Anaplastic thyroid carcinoma (ATC) is an extremely aggressive human malignancy characterized by a marked degree of invasiveness, absense of features of thyroid differentiation and resistance to current medical treatment. It is well known that ATCs are characterized by deregulation of genes related to cell cycle regulation, i.e., cyclin-dependent kinases (CDKs) and endogenous cyclin-dependent kinase inhibitors (CDKIs). Therefore, in the present study, the effect of a novel exogenous cyclin-dependent kinase inhibitor, BP-14, was investigated in three human ATC cell lines. The ATC-derived cell lines FRO, SW1736 and 8505C were treated with BP-14 alone or in combination with the mTOR inhibitor everolimus. In all ATC cell lines, treatment with BP-14 decreased cell viability and, in two of them, BP-14 modified expression of genes involved in epithelial-mesenchymal transition. Thus, our data indicate that BP-14 is a potential new compound effective against ATC. Combined treatment with BP-14 and the mTOR inhibitor everolimus had a strong synergistic effect on cell viability in all three cell lines, suggesting that the combined used of CDK and mTOR inhibitors may be a useful strategy for ATC treatment.

Targeting post-translational histone modifications for the treatment of non-medullary thyroid cancer

Genomic and epigenetic alterations are now being exploited as molecular targets in cancer treatment. Abnormalities involving the post-translational modification of histones have been demonstrated in thyroid cancer, and they are regarded as promising molecular targets for novel drug treatment of tumors that are resistant to conventional therapies. After a brief overview of the histone modifications most commonly associated with human malignancies, we will review recently published preclinical and clinical findings regarding the use of histone-activity modulators in thyroid cancers. Particular attention will be focused on their use as re-differentiating or anti-proliferating agents, the differential effects observed when they are used alone and in combination with other targeted drugs, and current prospects for their use in the treatment of thyroid cancer.

Effects of HuR downregulation on anaplastic thyroid cancer cells

Anaplastic thyroid cancer (ATC) constitutes one of the most aggressive types of human solid cancer, and is characterized by the absence of thyroid differentiation features and a marked degree of invasiveness. We have previously demonstrated that the RNA-binding protein Hu antigen R (HuR) is overexpressed in thyroid carcinoma; thus, the biological role of this RNA-binding protein was investigated in the present study using the ATC cell lines SW1736 and 8505C. In both cell lines, HuR protein levels were higher compared with in the non-tumorigenic thyroid cell line Nthy-ori-3.1. HuR silencing by RNA interference in both ATC cell lines decreased cell viability, increased apoptosis rates and reduced the capability to form colonies in soft agar. Thus, HuR plays an important role in the proliferation and aggressiveness of ATC cells. The histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) was able to reduce the viability of ATC cells. The results demonstrated that SAHA was able to decrease HuR expression in SW1736 and 8505C cells. Furthermore, since it is known that the transcription factor nuclear factor (NF)-κB modulates HuR expression, whether SAHA affects the nuclear (active) fraction of NF-κB in ATC cells was investigated. The data suggested that SAHA decreases ATC cell viability by reducing the active form of NF-κB, which, in turn, modulates HuR expression.

A polymorphic GGC repeat in the NPAS2 gene and its association with melanoma

Circadian clock regulation in mammals is controlled by feedback loops of a set of circadian genes. One of these circadian genes, NPAS2, encodes for a member of the bHLH-PAS class of transcription factors and is expressed in the forebrain and in some peripheral organs such as liver and skin. Other biological processes are also regulated by circadian genes. For example, NPAS2 is involved in cell proliferation, DNA damage repair and malignant transformation. Aberrant expression of clock genes has been previously observed in melanoma which led to our effort to sequence the NPAS2 promoter region in this cancer type. The NPAS2 putative promoter and 5′ untranslated region of ninety-three melanoma patients and ninety-six control subjects were sequenced and several variants were identified. Among these is a novel microsatellite comprising a GGC repeat with different alleles ranging from 7 to 13 repeats located in the 5′ untranslated exon. Homozygosity of an allele with nine repeats (9/9) was more prevalent in melanoma than in control subjects (22.6% and 13.5%, respectively, P: 0.0206) suggesting that some NPAS2 variants might contribute to melanoma susceptibility. Impact statement This report describes a variable microsatellite repeat sequence located in the 5′ untranslated exon of NSPAS2, a gene encoding a clock transcription factor. Significantly, this study is the first to show that a variant copy number GGC repeat sequence in the NPAS2 clock gene associates with melanoma risk and which may be useful in the assessment of melanoma predisposition.

Effects of nutraceuticals on anaplastic thyroid cancer cells

PurposeThe anaplastic thyroid carcinoma (ATC) is the most aggressive thyroid cancer with a high mortality rate. Since nutraceuticals may exert beneficial effects on tumor biology, here, effects of four of these compounds [resveratrol, genistein, curcumin and epigallocatechin-3-gallate (EGCG)] on ATC cell lines were investigated.MethodsTwo ATC-derived cell lines were used: SW1736 and 8505C. Cell viability and in vitro aggressiveness was tested by MTT and soft agar assays. Apoptosis was investigated by Western Blot, using an anti-cleaved-PARP antibody. mRNA and miRNA levels were quantified by real-time PCR.ResultsAll tested nutraceuticals caused in both cell lines decrease of cell viability and increase of apoptosis. In contrast, only curcumin reduced in vitro aggressiveness in both SW1736 and 8505C cell lines, while genistein and EGCG determined a reduction of colony formation only in 8505C cells. Effects on genes related to the thyroid-differentiated phenotype were also tested: resveratrol and genistein administration determined the increment of almost all tested mRNAs in both cell lines. Instead curcumin and EGCG treatments had opposite effects in the two cell lines, causing the increment of almost all the mRNAs in 8505C cells and their reduction in SW1736. Finally, effects of nutraceuticals on levels of several miRNAs, known as important in thyroid cancer progression (hsa-miR-221, hsa-miR-222, hsa-miR-21, hsa-miR-146b, hsa-miR-204), were tested. Curcumin induced a strong and significant reduction of all miR analyzed, except for has-miR-204, in both cell lines.ConclusionsAltogether, our results clearly indicate the anti-cancer proprieties of curcumin, suggesting the promising use of this nutraceutical in ATC treatment. Resveratrol, genistein and EGCG have heterogeneous effects on molecular features of ATC cells.