Understanding the Variability of 22q11.2 Deletion Syndrome: The Role of Epigenetic Factors.

Initially described as a triad of immunodeficiency, congenital heart defects and hypoparathyroidism, 22q11.2 deletion syndrome (22q11.2DS) now encompasses a great amount of abnormalities involving different systems. Approximately 85% of patients share a 3 Mb 22q11.2 region of hemizygous deletion in which 46 protein-coding genes are included. However, the hemizygosity of the genes of this region cannot fully explain the clinical phenotype and the phenotypic variability observed among patients. Additional mutations in genes located outside the deleted region, leading to "dual diagnosis", have been described in 1% of patients. In some cases, the hemizygosity of the 22q11.2 region unmasks autosomal recessive conditions due to additional mutations on the non-deleted allele. Some of the deleted genes play a crucial role in gene expression regulation pathways, involving the whole genome. Typical miRNA expression patterns have been identified in 22q11.2DS, due to an alteration in miRNA biogenesis, affecting the expression of several target genes. Also, a methylation epi-signature in CpG islands differentiating patients from controls has been defined. Herein, we summarize the evidence on the genetic and epigenetic mechanisms implicated in the pathogenesis of the clinical manifestations of 22q11.2 DS. The review of the literature confirms the hypothesis that the 22q11.2DS phenotype results from a network of interactions between deleted protein-coding genes and altered epigenetic regulation.

Targeted activity of the small molecule kinase inhibitor Pz-1 towards RET and TRK kinases.

We have recently described Pz-1, a benzimidazole-based type-2 RET and VEGFR2 inhibitor. Based on a kinome scan, here we show that Pz-1 is also a potent (IC50 < 1 nM) TRKA/B/C inhibitor. Pz-1 potently inhibited proliferation of human cancer cells carrying either RET- or TRKA oncoproteins (IC50 ~ 1 nM), with a negligible effect against RET- and TRKA-negative cells. By testing mutations, known to mediate resistance to other compounds, RET G810R/S, but not L730I/V, E732K, V738A and Y806N, showed some degree of resistance to Pz-1. In the case of TRKA, G595R and F589L, but not G667C, showed some degree of resistance. In xenograft models, orally administered Pz-1 almost completely inhibited RET- and TRKA-mutant tumours at 1-3 mg/kg/day but showed a reduced effect on RET/TRKA-negative cancer models. The activity, albeit reduced, on RET/TRKA-negative tumours may be justified by VEGFR2 inhibition. Tumours induced by NIH3T3 cells transfected by RET G810R and TRKA G595R featured resistance to Pz-1, demonstrating that RET or TRKA inhibition is critical for its anti-tumourigenic effect. In conclusion, Pz-1 represents a new powerful kinase inhibitor with distinct activity towards cancers induced by oncogenic RET and TRKA variants, including some mutants displaying resistance to other drugs.

Clinical characteristics of individuals with Down syndrome deceased with CoVID-19 in Italy-A case series.

BACKGROUND: Persons with Down syndrome (DS) are presumed to be at high risk of severe CoVID-19, due to immune dysregulation and often compromised cardiopulmonary function. Aim of the present study is to assess epidemiological and clinical characteristics of individuals with DS deceased in Italian hospitals with CoVID-19. METHODS: We used a nationwide database of 3,438 patients deceased with RT-PCR-confirmed SARS-CoV-2 infection in Italy (10.4% of all deaths with CoVID-19 in the country at the time of analysis). Data on demographics, pre-existing comorbidities and in-hospital complications leading to death were extracted from medical charts obtained from hospitals. Data on individuals with DS deceased with CoVID-19 were obtained from this sample. RESULTS: Sixteen cases of death in individuals with DS (0.5% of all charts analyzed) were identified. Acute respiratory distress syndrome occurred in all 16 cases. Compared with individuals without DS, those with DS deceased with CoVID-19 were younger (52.3 ± 7.3 vs. 78.1 ± 10.6 years, p < .001) and presented a higher incidence of superinfections (31.2 vs. 13.0%, p = .029). Autoimmune diseases (43.8 vs. 4%, p < .001), obesity (37.5 vs. 11%, p = .009), and dementia (37.5 vs. 16.3%, p = .012) were more prevalent in individuals with DS. ICU admissions was similar in both groups (25 vs. 18.8%, p = .129). CONCLUSIONS: Individuals with DS deceased with CoVID-19 are younger than individuals without DS. Comorbidity burden and increased risk of complications (i.e., bacterial superinfections) can influence CoVID-19 prognosis in individuals with DS. Specific strategies to prevent and mitigate the effects of CoVID-19 in the population with DS are needed.

Primary prevention as an essential factor ensuring sustainability of health systems: the example of congenital anomalies.

Protection of early development contributes to health of next generations. Congenital anomalies (and other adverse reproductive outcomes) are an important public health issue and early indicator of public health risks, as early development is influenced by many risk factors (e.g., nutrition, lifestyles, pollution, infections, medications, etc). Effective primary prevention requires an integrated "One Health" approach, linking knowledge and action. This requires surveillance of health events and potential health-damaging factors, science-based risk analysis, citizens' empowerment and education of health professionals. From the policy standpoint, joint budgeting mechanisms are needed to sustain with equity intersectoral actions (involving policy domains of health, social affairs, education, agriculture and environment). States should devote resources to strengthen registries and systematic data collection for surveillance of congenital anomalies, to better inform national prevention strategies. Investing in primary prevention based on scientific evidence is essential to support sustainable and resilient health systems and sustainable development of the society.

Association between DNA methylation profile and malignancy in follicular-patterned thyroid neoplasms.

Molecular differentiation between benign (follicular thyroid adenoma, FTA) and malignant (follicular thyroid carcinoma, FTC) thyroid neoplasms is challenging. Here, we explored the genome-wide DNA methylation profile of FTA (n.10) and FTC (n.11) compared to normal thyroid (NT) (n.7) tissues. FTC featured 3,564 differentially-methylated CpGs (DMCpG), most (84%) of them hypermethylated, with respect to normal controls. At the principal component analysis (PCA), the methylation profile of FTA occupied an intermediate position between FTC and normal tissue. A large fraction (n. 2,385) of FTC-associated DMCpG were related (intragenic or within 1500 bp from the transcription start site) to annotated genes (n. 1,786). FTC-hypermethylated genes were enriched for targets of the Polycomb transcriptional repressor complex and the specific histone H3 marks (H3K4me2/me3-H3K27me3) found in chromatin domains known as "bivalent". Transcriptome profiling by RNAseq showed that 7.9% of the DMCpGs-associated genes were differentially expressed in FTC compared to NT, suggesting that altered DNA methylation may contribute to their altered expression. Overall, this study suggests that perturbed DNA methylation, in particular hypermethylation, is a component of the molecular mechanisms leading to the formation of FTC and that DNA methylation profiling may help differentiating FTCs from their benign counterpart.

Oncogene-induced senescence and its evasion in a mouse model of thyroid neoplasia.

Here we describe a conditional doxycycline-dependent mouse model of RET/PTC3 (NCOA4-RET) oncogene-induced thyroid tumorigenesis. In these mice, after 10 days of doxycycline (dox) administration, RET/PTC3 expression induced mitogen activated protein kinase (MAPK) stimulation and a proliferative response which resulted in the formation of hyperplastic thyroid lesions. This was followed, after 2 months, by growth arrest accompanied by typical features of oncogene-induced senescence (OIS), including upregulation of p16INK4A and p21CIP, positivity at the Sudan black B, activation of the DNA damage response (DDR) markers γH2AX and pChk2 T68, and induction of p53 and p19ARF. After 5 months, about half of thyroid lesions escaped OIS and formed tumors that remained dependent on RET/PTC3 expression. This progression was accompanied by activation of AKT-FOXO1/3a pathway and increased serum TSH levels.

Anterior gradient protein 2 promotes survival, migration and invasion of papillary thyroid carcinoma cells.

BACKGROUND: Through a transcriptome microarray analysis, we have isolated Anterior gradient protein 2 (AGR2) as a gene up-regulated in papillary thyroid carcinoma (PTC). AGR2 is a disulfide isomerase over-expressed in several human carcinomas and recently linked to endoplasmic reticulum (ER) stress. Here, we analyzed the expression of AGR2 in PTC and its functional role. METHODS: Expression of AGR2 was studied by immunohistochemistry and real time PCR in normal thyroids and in PTC samples. The function of AGR2 was studied by knockdown in PTC cells and by ectopic expression in non-transformed thyroid cells. The role of AGR2 in the ER stress was analyzed upon treatment of cells, expressing or not AGR2, with Bortezomib and analyzing by Western blot the expression levels of GADD153. RESULTS: PTC over-expressed AGR2 at mRNA and protein levels. Knockdown of AGR2 in PTC cells induced apoptosis and decreased migration and invasion. Ectopic expression of AGR2 in non-transformed human thyroid cells increased migration and invasion and protected cells from ER stress induced by Bortezomib. CONCLUSIONS: AGR2 is a novel marker of PTC and plays a role in thyroid cancer cell survival, migration, invasion and protection from ER stress.

Identification of targets of Twist1 transcription factor in thyroid cancer cells.

CONTEXT: Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human tumors. Twist1 is a basic helix-loop-helix transcription factor involved in cancer development and progression. We showed that Twist1 affects thyroid cancer cell survival and motility. OBJECTIVE: We aimed to identify Twist1 targets in thyroid cancer cells. DESIGN: Transcriptional targets of Twist1 were identified by gene expression profiling the TPC-Twist1 cells in comparison with control cells. Functional studies were performed by silencing in TPC-Twist1 and in CAL62 cells the top 10 upregulated genes and by evaluating cell proliferation, survival, migration, and invasion. Chromatin immunoprecipitation was performed to verify direct binding of Twist1 to target genes. Quantitative RT-PCR was applied to study the expression level of Twist1 target genes in human thyroid carcinoma samples. RESULTS: According to the gene expression profile, the top functions enriched in TPC-Twist1 cells were cellular movement, cellular growth and proliferation, and cell death and survival. Silencing of the top 10 upregulated genes reduced viability of TPC-Twist1 and of CAL62 cells. Silencing of COL1A1, KRT7, and PDZK1 also induced cell death. Silencing of HS6ST2, THRB, ID4, RHOB, and PDZK1IP also impaired migration and invasion of TPC-Twist1 and of CAL62 cells. Chromatin immunoprecipitation showed that Twist1 directly binds the promoter of the top 10 upregulated genes. Quantitative RT-PCR showed that HS6ST2, COL1A1, F2RL1, LEPREL1, PDZK1, and PDZK1IP1 are overexpressed in thyroid carcinoma samples compared with normal thyroids. CONCLUSIONS: We identified a set of genes that mediates Twist1 biological effects in thyroid cancer cells.

Overexpression of miR-10a and miR-375 and downregulation of YAP1 in medullary thyroid carcinoma.

MicroRNAs are a primordial mechanism of gene expression control that appear to be crucial to cellular development and may play an important role in tumor development. Much is known about the genetics of medullary thyroid carcinomas, as approximately 25% are hereditary and harbor germ line activating mutations in the RET gene. Somatic RET mutations are also seen in roughly 50% of sporadic medullary thyroid carcinomas. Few studies, however, have evaluated the role of microRNA expression in these tumors. DNA and RNA were extracted from formalin-fixed paraffin-embedded tissue blocks of 15 medullary thyroid carcinomas [10 with RET mutations (3 hereditary) and 5 without RET mutations] and 5 non-tumor thyroid glands. miRNA expression of 754 targets was quantitated by real-time PCR using the ABI OpenArray miRNA assay. Three miRNAs showed significant differential expression and were validated in a larger cohort of 59 cases by real-time PCR. Expression of potential downstream targets and upstream regulators was also investigated by real-time PCR. miR-375 and miR-10a were significantly overexpressed, while miR-455 was underexpressed in medullary thyroid carcinomas. Expression of all 3 miRNAs was validated in the larger cohort of cases (miR-375, p=3.3×10(-26); miR-10a, p=5.6×10(-14); miR-455, p=2.4×10(-4)). No significant differences in miRNA expression were found between RET mutation positive and negative tumors nor between sporadic and hereditary tumors. Expression of the potential downstream targets of miR-375, YAP1 (a growth inhibitor) and SLC16a2 (a transporter of thyroid hormone), was down-regulated in the tumors suggesting that miR-375 is a negative regulator of the expression of these genes. Thus, differential expression of miR-375, miR-10a and miR-455 may be important for tumor development and/or reflect C-cell lineage of medullary thyroid carcinoma. Furthermore, the growth inhibitor YAP1 is identified as a potential important downstream target of miR-375.

FOXM1 is a molecular determinant of the mitogenic and invasive phenotype of anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma (ATC) is a very aggressive thyroid cancer. forkhead box protein M1 (FOXM1) is a member of the forkhead box family of transcription factors involved in control of cell proliferation, chromosomal stability, angiogenesis, and invasion. Here, we show that FOXM1 is significantly increased in ATCs compared with normal thyroid, well-differentiated thyroid carcinomas (papillary and/or follicular), and poorly differentiated thyroid carcinomas (P=0.000002). Upregulation of FOXM1 levels in ATC cells was mechanistically linked to loss-of-function of p53 and to the hyperactivation of the phosphatidylinositol-3-kinase/AKT/FOXO3a pathway. Knockdown of FOXM1 by RNA interference inhibited cell proliferation by arresting cells in G2/M and reduced cell invasion and motility. This phenotype was associated with decreased expression of FOXM1 target genes, like cyclin B1 (CCNB1), polo-like kinase 1 (PLK1), Aurora B (AURKB), S-phase kinase-associated protein 2 (SKP2), and plasminogen activator, urokinase: uPA (PLAU). Pharmacological inhibition of FOXM1 in an orthotopic mouse model of ATC reduced tumor burden and metastasization. All together, these findings suggest that FOXM1 represents an important player in thyroid cancer progression to the anaplastic phenotype and a potential therapeutic target for this fatal cancer.

Activation of the mTOR pathway in primary medullary thyroid carcinoma and lymph node metastases.

PURPOSE: Understanding the molecular pathogenesis of medullary thyroid carcinoma (MTC) is prerequisite to the design of targeted therapies for patients with advanced disease. EXPERIMENTAL DESIGN: We studied by immunohistochemistry the phosphorylation status of proteins of the RAS/MEK/ERK and PI3K/AKT/mTOR pathways in 53 MTC tissues (18 hereditary, 35 sporadic), including 51 primary MTCs and 2 cases with only lymph node metastases (LNM). We also studied 21 autologous LNMs, matched to 21 primary MTCs. Staining was graded on a 0 to 4 scale (S score) based on the percentage of positive cells. We also studied the functional relevance of the mTOR pathway by measuring cell viability, motility, and tumorigenicity upon mTOR chemical blockade. RESULTS: Phosphorylation of ribosomal protein S6 (pS6), a downstream target of mTOR, was evident (S ≥ 1) in 49 (96%) of 51 primary MTC samples. This was associated with activation of AKT (phospho-Ser473, S > 1) in 79% of cases studied. Activation of pS6 was also observed (S ≥ 1) in 7 (70%) of 10 hereditary C-cell hyperplasia specimens, possibly representing an early stage of C-cell transformation. It is noteworthy that 22 (96%) of 23 LNMs had a high pS6 positivity (S ≥ 3), which was increased compared with autologous matched primary MTCs (P = 0.024). Chemical mTOR blockade blunted viability (P < 0.01), motility (P < 0.01), and tumorigenicity (P < 0.01) of human MTC cells. CONCLUSION: The AKT/mTOR pathway is activated in MTC, particularly, in LNMs. This pathway sustains malignant features of MTC cell models. These findings suggest that targeting mTOR might be efficacious in patients with advanced MTC.

Novel candidate genes of thyroid tumourigenesis identified in Trk-T1 transgenic mice.

For an identification of novel candidate genes in thyroid tumourigenesis, we have investigated gene copy number changes in a Trk-T1 transgenic mouse model of thyroid neoplasia. For this aim, 30 thyroid tumours from Trk-T1 transgenics were investigated by comparative genomic hybridisation. Recurrent gene copy number alterations were identified and genes located in the altered chromosomal regions were analysed by Gene Ontology term enrichment analysis in order to reveal gene functions potentially associated with thyroid tumourigenesis. In thyroid neoplasms from Trk-T1 mice, a recurrent gain on chromosomal bands 1C4-E2.3 (10.0% of cases), and losses on 3H1-H3 (13.3%), 4D2.3-E2 (43.3%) and 14E4-E5 (6.7%) were identified. The genes Twist2, Ptma, Pde6d, Bmpr1b, Pdlim5, Unc5c, Srm, Trp73, Ythdf2, Taf12 and Slitrk5 are located in these chromosomal bands. Copy number changes of these genes were studied by fluorescence in situ hybridisation on 30 human papillary thyroid carcinoma (PTC) samples and altered gene expression was studied by qRT-PCR analyses in 67 human PTC. Copy number gains were detected in 83% of cases for TWIST2 and in 100% of cases for PTMA and PDE6D. DNA losses of SLITRK1 and SLITRK5 were observed in 21% of cases and of SLITRK6 in 16% of cases. Gene expression was significantly up-regulated for UNC5C and TP73 and significantly down-regulated for SLITRK5 in tumours compared with normal tissue. In conclusion, a global genomic copy number analysis of thyroid tumours from Trk-T1 transgenic mice revealed a number of novel gene alterations in thyroid tumourigenesis that are also prevalent in human PTCs.

TWIST1 plays a pleiotropic role in determining the anaplastic thyroid cancer phenotype.

CONTEXT: Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human tumors; it is characterized by chemoresistance, local invasion, and distant metastases. ATC is invariably fatal. OBJECTIVE: The aim was to study the role of TWIST1, a basic helix-loop-helix transcription factor, in ATC. DESIGN: Expression of TWIST1 was studied by immunohistochemistry and real-time PCR in normal thyroids and well-differentiated, poorly differentiated, and ATC. The function of TWIST1 was studied by RNA interference in ATC cells and by ectopic expression in well-differentiated thyroid carcinoma cells. RESULTS: ATCs up-regulate TWIST1 with respect to normal thyroids as well as to poorly and well-differentiated thyroid carcinomas. Knockdown of TWIST1 by RNA interference in ATC cells reduced cell migration and invasion and increased sensitivity to apoptosis. The ectopic expression of TWIST1 in thyroid cells induced resistance to apoptosis and increased cell migration and invasion. CONCLUSIONS: TWIST1 plays a key role in determining malignant features of the anaplastic phenotype in vitro.

Extracellular superoxide dismutase is a thyroid differentiation marker down-regulated in cancer.

Reactive oxygen species, specifically hydrogen peroxide (H(2)O(2)), have a significant role in hormone production in thyroid tissue. Although recent studies have demonstrated that dual oxidases are responsible for the H(2)O(2) synthesis needed in thyroid hormone production, our data suggest a pivotal role for superoxide dismutase 3 (SOD3) as a major H(2)O(2)-producing enzyme. According to our results, Sod3 is highly expressed in normal thyroid, and becomes even more abundant in rat goiter models. We showed TSH-stimulated expression of Sod3 via phospholipase C-Ca(2+) and cAMP-protein kinase A, a pathway that might be disrupted in thyroid cancer. In line with this finding, we demonstrated an oncogene-dependent decrease in Sod3 mRNA expression synthesis in thyroid cancer cell models that corresponded to a similar decrease in clinical patient samples, suggesting that SOD3 could be used as a differentiation marker in thyroid cancer. Finally, the functional analysis in thyroid models indicated a moderate role for SOD3 in regulating normal thyroid cell proliferation being in line with our previous observations.

Cytostatic activity of adenosine triphosphate-competitive kinase inhibitors in BRAF mutant thyroid carcinoma cells.

CONTEXT: The V600E mutation accounts for the vast majority of thyroid carcinoma-associated BRAF mutations. OBJECTIVE: The aim was to study the effects of the two BRAF V600E ATP-competitive kinase inhibitors, PLX4032 and PLX4720, in thyroid carcinoma cell lines. EXPERIMENTAL DESIGN: We examined the activity of PLX4032 and PLX4720 in thyroid carcinoma cell lines harboring BRAF V600E (8505C, BCPAP, SW1736, BHT101), NRAS Q61R (HTH7), KRAS G12R (CAL62), HRAS G13R (C643), or RET/PTC1 (TPC-1) oncogenes. Normal thyrocytes (PC Cl 3) were used as control. RESULTS: Both compounds inhibited the proliferation of BRAF mutant cell lines, but not normal thyrocytes, with a half maximal effective concentration (EC(50)) ranging from 78-113 nm for PLX4720 and from 29-97 nm for PLX4032. Doses equal to or higher than 500 nm were required to achieve a similar effect in BRAF wild-type cancer cells. Phosphorylation of ERK 1/2 and MAPK kinase (MEK) 1/2 decreased upon PLX4032 and PLX4720 treatment in BRAF mutant thyroid carcinoma cells but not in normal thyroid cells or in cell lines harboring mutations of RAS or RET/PTC1 rearrangements. PLX4032 and PLX4720 treatment induced a G(1) block and altered expression of genes involved in the control of G(1)-S cell-cycle transition. 8505C cell tumor xenografts were smaller in nude mice treated with PLX4032 than in control mice. This inhibition was associated with reduction of phospho-ERK and phospho-MEK levels. CONCLUSIONS: This study provides additional evidence of the promising nature of mutant BRAF as a molecular target for thyroid carcinoma cells.

Morphological ultrasound microimaging of thyroid in living mice.

The objective of the study was to explore high-frequency ultrasound (HFUS) for noninvasive microimaging of thyroid in living mice. Thyroid examination was performed by HFUS in 10 normal C57BL/6 mice, eight mice treated by propylthiouracil, and 22 Tg-TRK-T1 transgenic mice. The dimension of the gland and the presence of nodules were evaluated. Nodules were classified as malignant (hypoechogenicity, poorly defined margins, internal microcalcification, irregular shapes, and extra glandular extension) or not, and the findings were compared with histological data. Thyroid images were successfully obtained in all the animals analyzed. Normal thyroid reached a volume of 4.92 microl (range 2.11-4.92 microl). Mice with propylthiouracil-induced goiter showed diffuse thyroid enlargement (median volume 6.67 microl, range 4.09-8.82 microl). In 19 of 22 Tg-TRK-T1 mice (86%), HFUS identified a nodular process (the smallest detected nodule had a diameter of 0.46 mm). Eleven nodules were classified as malignant and eight as benign. Compared with histological analysis, HFUS showed a sensitivity of 100% in the detection of thyroid nodules and a specificity of 60% (two of the nodules identified by HFUS were not confirmed at the histology). The specificity and sensitivity of HFUS in predicting the malignancy of the thyroid nodules were 83 and 91%, respectively. Thus, HFUS is an accurate imaging modality that can potentially replace more invasive techniques, and, therefore, it represents a significant advancement in phenotypic assessment of mouse models of thyroid cancer.

Identification of Polo-like kinase 1 as a potential therapeutic target in anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive and chemoresistant cancers. The serine/threonine kinase Polo-like kinase 1 (PLK1), a key regulator of multiple steps during mitotic progression, is highly expressed in ATC. Here, we used the BI 2536 PLK1 inhibitor on ATC and nontransformed thyroid follicular cell lines. Our data show that ATC cells are addicted to high levels of PLK1 activity for proliferation, survival, anchorage-independent growth, and tumorigenicity. On treatment with nanomolar doses of BI 2536, ATC cells progressed normally through S phase but died thereafter, directly from mitotic arrest. Immunofluorescence microscopy, immunoblot, and flow cytometry analysis showed that, on PLK1 blockade, ATC cells arrested in prometaphase with a 4N DNA content. Treated ATC cells accumulated phosphohistone H3 and displayed characteristic mitotic (Polo) spindle aberrations. Nontransformed thyroid cells were 3.2- to 18.4-fold less susceptible to BI 2536-induced cell cycle effects compared with ATC cells. These findings identify PLK1 as a promising target for the molecular therapy of ATC.

Biological role and potential therapeutic targeting of the chemokine receptor CXCR4 in undifferentiated thyroid cancer.

Anaplastic thyroid carcinoma (ATC) is a rare thyroid cancer type with an extremely poor prognosis. Despite appropriate treatment, which includes surgery, radiotherapy, and chemotherapy, this cancer is invariably fatal. CXCR4 is the receptor for the stromal cell-derived factor-1 (SDF-1)/CXCL12 chemokine and it is expressed in a variety of solid tumors, including papillary thyroid carcinoma. Here, we show that ATC cell lines overexpress CXCR4, both at the level of mRNA and protein. Furthermore, we found that CXCR4 was overexpressed in ATC clinical samples, with respect to normal thyroid tissues by real-time PCR and immunohistochemistry. Treatment of ATC cells with SDF-1 induced proliferation and increase in phosphorylation of extracellular signal-regulated kinases and protein kinase B/AKT. These effects were blocked by the specific CXCR4 antagonist AMD3100 and by CXCR4 RNA interference. Moreover, AMD3100 effectively reduced tumor growth in nude mice inoculated with different ATC cells. Thus, we suggest that CXCR4 targeting is a novel potential strategy in the treatment of human ATC.