Redifferentiation therapy for thyroid cancer

Dual effects for lovastatin in anaplastic thyroid cancer: the pivotal effect of transketolase (TKT) on lovastatin and tumor proliferation

This study tested the hypothesis that the effects of lovastatin on anaplastic thyroid cancer cell growth are mediated by upregulation of transketolase (TKT) expression. The effects of lovastatin on TKT protein levels in ARO cells were determined using western blot and proteomic analyses. After treatment with lovastatin and oxythiamine, the in vitro and in vivo growth of ARO cells was determined using 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assays and tumor xenografts in nude mice. TKT protein expression in the ARO tumors was assessed using immunohistochemistry analysis. Proteomic analysis revealed that 25 µM lovastatin upregulated TKT expression. Co-treatment of ARO cells with 1 µM lovastatin + 1 µM oxythiamine increased TKT protein expression compared with control levels; however, no differences were observed with 10 µM lovastatin + 1 µM oxythiamine. Furthermore, treatment with either oxythiamine or lovastatin alone reduced ARO tumor expression of TKT, as well as decreased ARO cell proliferation in vitro and tumor growth in vivo. However, mice treated with both lovastatin and oxythiamine at the same time had tumor volumes similar to that of the untreated control group. We conclude that either lovastatin or oxythiamine reduced ARO cell growth; however, the combination of these drugs resulted in antagonism of ARO tumor growth.

Curcumin induces G2/M arrest, apoptosis, NF-κB inhibition, and expression of differentiation genes in thyroid carcinoma cells

PURPOSE

The therapy of unresectable advanced thyroid carcinomas shows unfavorable outcome. Constitutive nuclear factor-κB (NF-κB) activation in thyroid carcinomas frequently contributes to therapeutic resistance; the radioiodine therapy often fails due to the loss of differentiated functions in advanced thyroid carcinomas. Curcumin is known for its anticancer properties in a series of cancers, but only few studies have focused on thyroid cancer. Our aim was to evaluate curcumin's molecular mechanisms and to estimate if curcumin could be a new therapeutic option in advanced thyroid cancer.

METHODS

Human thyroid cancer cell lines TPC-1 (papillary), FTC-133 (follicular), and BHT-101 (anaplastic) were treated with curcumin. Using real-time PCR analysis, we investigated microRNA (miRNA) and mRNA expression levels. Cell cycle, Annexin V/PI staining, and caspase-3 activity analysis were performed to detect apoptosis. NF-κB p65 activity and cell proliferation were analyzed using appropriate ELISA-based colorimetric assay kits.

RESULTS

Treatment with 50 μM curcumin significantly increased the mRNA expression of the differentiation genes thyroglobulin (TG) and sodium iodide symporter (NIS) in all three cell lines and induced inhibition of cell proliferation, apoptosis, and decrease of NF-κB p65 activity. The miRNA expression analyses showed a significant deregulation of miRNA-200c, -21, -let7c, -26a, and -125b, known to regulate cell differentiation and tumor progression. Curcumin arrested cell growth at the G2/M phase.

CONCLUSIONS

Curcumin increases the expression of redifferentiation markers and induces G2/M arrest, apoptosis, and downregulation of NF-κB activity in thyroid carcinoma cells. Thus, curcumin appears to be a promising agent to overcome resistance to the conventional cancer therapy.

A Unique Case of Extraovarian Sex-Cord Stromal Fibrosarcoma, With Subsequent Relapse of Differentiated Sex-Cord Tumor

Primary fibrosarcoma arising from ovarian sex-cord stroma is a very rare neoplasm, with only a few reports in the literature. These tumors have been reported to express inhibin which allows their distinction from fibrosarcomas of soft tissue. Here, we report a case of a fibrosarcoma arising in the broad ligament. Despite being totally separate from the ovary, the tumor was diagnosed as sex-cord stromal type on the basis of inhibin expression. Furthermore, this patient suffered a recurrence of her tumor in the pelvis, which showed both the fibrosarcomatous, as well as other sex-cord elements, confirming the sex-cord stromal differentiation of the sarcoma. To our knowledge, this is the first case of a sex-cord stromal fibrosarcoma arising from an extraovarian site. Furthermore, this is also the first case of a recurrent fibrosarcoma, which showed redifferentiation of the tumor into other sex-cord components.

Novel approaches in anaplastic thyroid cancer therapy

Anaplastic thyroid cancer (ATC), accounting for less than 2% of all thyroid cancer, is responsible for the majority of death from all thyroid malignancies and has a median survival of 6 months. The resistance of ATC to conventional thyroid cancer therapies, including radioiodine and thyroid-stimulating hormone suppression, contributes to the very poor prognosis of this malignancy. This review will cover several cellular signaling pathways and mechanisms, including RET/PTC, RAS, BRAF, Notch, p53, and histone deacetylase, which are identified to play roles in the transformation and dedifferentiation process, and therapies that target these pathways. Lastly, novel approaches and agents involving the Notch1 pathway, nuclear factor κB, Trk-fused gene, cancer stem-like cells, mitochondrial mutation, and tumor immune microenvironment are discussed. With a better understanding of the biological process and treatment modality, the hope is to improve ATC outcome in the future.

Surgical management of thyroid cancer

Thyroid cancer is the most common endocrine neoplasm; however, it only accounts for less than 1% of all human malignances. Thyroid cancers are divided into well differentiated and non-well differentiated cancers, according to their histology and behavior. The surgical management options of well-differentiated thyroid cancer include total or near-total thyroidectomy, subtotal thyroidectomy and lobectomy plus isthmusectomy. The extent of surgery for thyroid cancer continues to be an area of controversy. Complications associated with thyroid surgery are directly proportional to the extent of thyroidectomy and inversely proportional to the experience of the operating surgeon. They occur less frequently with good surgical technique and better understanding of surgical anatomy, and include wound healing and infections (seroma, hematoma and wound infection), nerve injury, hypoparathyroidism, hypothyroidism, postoperative hemorrhage and respiratory obstruction.

Vitamin D in thyroid tumorigenesis and development

Besides its classical role in bone and calcium homeostasis, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D, has many non-classical effects; antiproliferative, anti-apoptotic and prodifferentiating effects of 1,25(OH)2D3 have been described in several tumour types in preclinical models. This review focuses on the insights gained in the elucidation of the role of 1,25(OH)2D3 in the normal thyroid and in the pathogenesis, progression and treatment of thyroid cancer, the most common endocrine malignancy. An increasing amount of observations points towards a role for impaired 1,25(OH)2D3-VDR signalling in the occurrence and progression of thyroid cancer, and a potential for structural analogues in the multimodal treatment of dedifferentiated iodine-resistant thyroid cancer. A role for vitamin D in thyroid-related autoimmunity is less convincing and needs further study. Altered 1,25(OH)2D3-VDR signalling does not influence normal thyroid development nor thyrocyte function, but does affect C-cell function, at least in rodents. If these findings also apply to humans deserves further study.

Resveratrol induces differentiation markers expression in anaplastic thyroid carcinoma via activation of Notch1 signaling and suppresses cell growth

Anaplastic thyroid carcinoma (ATC) is an extremely aggressive malignancy with undifferentiated features, for which conventional treatments, including radioactive iodine ablation, are usually not effective. Recent evidence suggests that the Notch1 pathway is important in the regulation of thyroid cancer cell growth and expression of thyrocyte differentiation markers. However, drug development targeting Notch1 signaling in ATC remains largely underexplored. Previously, we have identified resveratrol out of over 7,000 compounds as the most potent Notch pathway activator using a high-throughput screening method. In this study, we showed that resveratrol treatment (10-50 μmol/L) suppressed ATC cell growth in a dose-dependent manner for both HTh7 and 8505C cell lines via S-phase cell-cycle arrest and apoptosis. Resveratrol induced functional Notch1 protein expression and activated the pathway by transcriptional regulation. In addition, the expression of thyroid-specific genes including TTF1, TTF2, Pax8, and sodium iodide symporter (NIS) was upregulated in both ATC cell lines with resveratrol treatment. Notch1 siRNA interference totally abrogated the induction of TTF1 and Pax8 but not of TTF2. Moreover, Notch1 silencing by siRNA decreased resveratrol-induced NIS expression. In summary, our data indicate that resveratrol inhibits cell growth and enhances redifferentiation in ATC cells dependent upon the activation of Notch1 signaling. These findings provide the first documentation for the role of resveratrol in ATC redifferentiation, suggesting that activation of Notch1 signaling could be a potential therapeutic strategy for patients with ATC and thus warrants further clinical investigation.

Antiproliferation and redifferentiation in thyroid cancer cell lines by polyphenol phytochemicals

Thyroid carcinogenesis is accompanied by loss of thyroid-specific functions and refractory to radioiodine and thyroid stimulating hormone (TSH) suppression therapy. Redifferentiating agents have been shown to inhibit tumor growth and improve the response to conventional therapy. Polyphenol phytochemicals (PPs) in fruits and vegetables have been reported to inhibit cancer initiation, promotion, progression and induce redifferentiation in selected types. In this study we examined PPs induce redifferentiation in thyroid cancer cell lines. We investigated the effects of genistein, resveratrol, quercetin, kaempferol, and resorcinol on the F9 embryonal carcinoma cell differentiation model. The thyroid cancer cell lines, TPC-1, FTC-133, NPA, FRO, and ARO, displayed growth inhibition in response to genistein, resveratrol, quercetin. We further demonstrated that genistein decreased the dedifferention marker CD97 in NPA cells and resveratrol decreased CD97 in FTC-133, NPA, FRO cells and quercetin decreased CD97 in all cell lines. We observed increased expression of differentiation marker NIS in FTC-133 cells in response to genistein, and resveratrol but no change in NPA, FRO, ARO cells. Quercetin increased or induced NIS in FTC-133, NPA, FRO cells. These findings suggest that PPs may provide a useful therapeutic intervention in thyroid cancer redifferentiation therapy.

1,25-dihydroxyvitamin D3 and a superagonistic analog in combination with paclitaxel or suberoylanilide hydroxamic acid have potent antiproliferative effects on anaplastic thyroid cancer

Anaplastic thyroid cancer represents one of the most aggressive cancers. The active form of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), has been shown to have antiproliferative and/or redifferentiating properties in several malignancies, including thyroid cancer. The objective of this study was to investigate the effects of 1,25(OH)(2)D(3) and the superagonistic analog CD578 in anaplastic thyroid cancer, alone or in combination with paclitaxel, a taxane, and suberoylanilide hydroxamic acid (SAHA), a potent histone deacetylase inhibitor with promising effects in undifferentiated thyroid cancer. Four human thyroid cancer cell lines (FTC-133, C643, 8505C and HTh74) were treated with 1,25(OH)(2)D(3) or CD578, alone or in combination with paclitaxel or SAHA. Effects on cell growth and differentiation were evaluated. Clear effects on growth arrest were observed in a clonogenic assay, and absolute cell counts demonstrated a 24-36% reduction in all cell lines after 72h treatment with 1,25(OH)(2)D(3) (10(-6)M) and a 60% inhibition after 120h in the most sensitive cell line HTh74. A similar growth inhibition was shown after treatment with a 1000-fold lower concentration of analog CD578. This growth arrest was explained by antiproliferative effects, further supported by an increased % of cells in the G(0)-G(1) phase of the cell cycle and by a decreased transcription factor E2F1 mRNA expression. Combination treatments of 1,25(OH)(2)D(3) or CD578 with paclitaxel or SAHA resulted in an additive and in some conditions a synergistic effect on the inhibition of proliferation. Redifferentiation analysis revealed only a modest increase in sodium iodide symporter and thyroglobulin mRNA expression after treatment with 1,25(OH)(2)D(3), without additive effect after combination treatment. No effects were observed on TSH-receptor or thyroid peroxidase mRNA expression. Our in vitro findings demonstrate that the superagonistic vitamin D analog CD578 holds promise as adjuvant antiproliferative therapy of anaplastic thyroid cancer, especially in combination with other drugs such as paclitaxel or SAHA.

The paired box-8/peroxisome proliferator-activated receptor-gamma oncogene in thyroid tumorigenesis

The American Cancer Society estimates 30,180 new cases of thyroid cancer in the United States in 2006. Of all thyroid cancers, 15-20% are follicular thyroid carcinoma (FTC), making this the second most common thyroid malignancy (after papillary carcinoma). A proportion of FTC has been found to be associated with a chromosomal translocation, t (2, 3)(q13;p25), which fuses the thyroid-specific transcription factor paired box-8 with the peroxisome proliferator-activated receptor-gamma nuclear receptor, a ubiquitously expressed transcription factor. This fusion event causes expression of a paired box-8/peroxisome proliferator-activated receptor-gamma fusion protein (PPFP). PPFP is detected in approximately 30% of FTC. In this report we review data on the role of PPFP in FTC, its mechanism of oncogenesis, and PPFP targeting as a strategy in thyroid cancer treatment.

Papillary thyroid cancer

Papillary thyroid cancer (PTC), the most common thyroid malignancy, is associated with an excellent prognosis. Overall survival is more than 90%. The first-line treatment is surgical excision, and although the debate continues as to whether a total thyroidectomy or thyroid lobectomy should be recommended, most patients at the University of California, San Francisco are treated with a total thyroidectomy. Not only has this been shown to be superior for overall survival in select patient populations, but local recurrence is also significantly lower with this approach. Total thyroidectomy also optimizes the adjuvant treatment options that are unique to "differentiated" thyroid cancer because these malignant cells retain many of the features of the native thyroid follicular cell. These cellular features are used for specialized investigations and treatment options in patients with PTC. For example, PTC cells retain the ability to produce thyroglobulin, to be stimulated by thyroid-stimulating hormone (TSH), and to take up iodine. These features are vital and separate differentiated thyroid cancer from other epithelial malignancies because such features can be used in clinical follow-up (monitoring serum thyroglobulin levels, whole body radioactive iodine scans) and in the treatment of patients with PTC (TSH suppression, radioactive iodine ablation of thyroid remnant, local recurrences, and regional or distant metastases). In summary, the wide array of treatment options for patients with PTC includes surgery, radioactive iodine, thyroid hormone suppression of TSH, external beam radiation (less commonly), and rarely, chemotherapy. This continues to be an area of exciting research for emerging therapy, much of which concentrates on enhancing or re-establishing the differentiated features of the thyroid cancer cell, in an effort to optimize the adjuvant treatment options. The treatment options that are chosen depend on patient factors, disease factors, and the decisions of the patient and treatment team.

Valproic acid inhibits growth, induces apoptosis, and modulates apoptosis-regulatory and differentiation gene expression in human thyroid cancer cells

BACKGROUND

Among the most promising new therapies for thyroid cancer are the histone deacetylase inhibitors. Valproic acid (VA) is an anticonvulsant that inhibits histone deacetylase activity at nontoxic concentrations. We hypothesized that VA would have antineoplastic effects on human thyroid cancer cells.

METHODS

We treated 1 papillary and 3 follicular thyroid cancer cell lines with VA (0.5-2 mmol/L) for 24 to 72 hours. Cell proliferation was measured with a cell proliferation assay kit. Annexin V-fluorescein isothiocyanate was used to quantitate cells that were undergoing apoptosis. Quantitative polymerase chain reaction was used to measure expression of apoptosis-regulatory and differentiation genes.

RESULTS

VA inhibited growth in all cell lines by 26% to 59% at 48 hours and up to 77% at 72 hours. Nineteen percent to 30% of VA-treated cells underwent apoptosis, compared with 4% to 8% of the control cells. Expression of pro survival genes bcl-2 and bcl-xl was down-regulated by 10% to 60%; expression of the proapoptosis gene bax was up-regulated by 23% to 85%. Sodium-iodide symporter and thyroglobulin messenger RNA expression were up-regulated by 93% to 370% in follicular cell lines but remained unchanged in the papillary cell line.

CONCLUSION

VA inhibits growth, induces apoptosis, and modulates apoptosis-regulatory and differentiation gene expression in thyroid cancer cells. These findings suggest that VA may be useful clinically for patients with thyroid cancers of follicular cell origin.

Treatment of thyroid cancer with histone deacetylase inhibitors and peroxisome proliferator-activated receptor-gamma agonists

Among the most promising new antineoplastic therapies for poorly differentiated or undifferentiated thyroid cancer are the histone deacetylase inhibitors and the peroxisome proliferator-activated receptor (PPAR)-gamma agonists. These two classes of drugs have been shown to inhibit growth and induce apoptosis and redifferentiation in a variety of hematologic and solid cancer cell lines and animal models. In this article we review the molecular mechanisms, in vitro and in vivo studies, and clinical applications of the histone deacetylase inhibitors and PPAR-gamma agonists in the treatment of thyroid cancer.