Anaplastic thyroid cancer therapy: dream or reality?

Targeted therapy with vemurafenib in BRAF(V600E)-mutated anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is one of the most aggressive malignancies, representing less than 5% of all thyroid carcinomas. Τhe median survival is limited to months due to the resistance of ATC to surgery, radioiodine therapy, radiotherapy and chemotherapy. This review will cover novel agents involving several cellular signaling pathways including the BRAF pathway. The BRAF inhibitor vemurafenib improves survival among patients with metastatic melanoma, hairy-cell leukemia and intracranial neoplasms with BRAF gene mutations. The frequency of a BRAF (V600E) mutation in ATC is about 25%.

CASE PRESENTATION

We report the first case of a marked partial response to adjuvant first line monotherapy with vemurafenib in BRAF V600E-mutated ATC. The 78-year-old man showed a sustained response for 7 months, thereafter scans revealed progressive disease and the patient died 10 months after first diagnosis. This case report is accompanied by a comprehensive review of current strategies and tools for ATC treatment.

CONCLUSIONS

This case and the review of current data confirm the benefit of BRAF inhibition in BRAF-mutated ATC, limited by acquired resistance to targeted therapy.

Vitamin B6 based Pt(II) complexes: Biomolecule derived potential cytotoxic agents for thyroid cancer

Vitamin B6 is an essential vitamin that serves as a co-enzyme in a number of enzymatic reactions in metabolism of lipids, amino acids and glucose. In the current study, we synthesized vitamin B6 derived ligand (L) and its complex Pt(L)Cl (C1). The ancillary chloride ligand of C1 was exchanged with pyridine co-ligand and another complex Pt(L)(py).BF4 (C2) was obtained. Both these complexes were obtained in excellent isolated yields and characterized thoroughly by different analytical methods. Thyroid cancer is one of the most common malignancies of the endocrine system, we studied the in vitro anticancer activity and mechanism of these vitamin B6 derived L and Pt(II) complexes in thyroid cancer cell line (FTC). Based on MTT assay, cell proliferation rate was reduced in a dose-dependent manner. According to apoptosis analysis, vitamin B6 based Pt(II) complexes treated cells depicted necrotic effect and TUNEL based apoptosis was observed in cancer cells. Furthermore, qRT-PCR analyses of cancer cells treated with C1 and/or C2 showed regulated expression of anti-apoptotic, pro-apoptosis and autophagy related genes. Western blot results demonstrated that C1 and C2 induced the activation of p53 and the cleavage of Poly (ADP-ribose) polymerase (PARP). These results suggest that these complexes inhibit the growth of FTC cells and induce apoptosis through p53 signaling. Thus, vitamin B6 derived Pt(II) complexes C1 and C2 may be potential cytotoxic agents for the treatment of thyroid cancer.

Chemical Characterization and Biological Activities of Phenolic-Rich Fraction from Cauline Leaves of Isatis tinctoria L. (Brassicaceae) Growing in Sicily, Italy

The present work focused on the evaluation of the antioxidant and cytotoxic activities of the phenolic-rich fraction (ItJ-EAF) obtained from cauline leaves collected in January from Isatis tinctoria L. (Brassicaceae) growing wild around Acireale (Sicily, Italy). The total phenolic, flavonoid, and condensed tannin contents of the fraction were determined spectrophotometrically, whereas the phenolic profile was assessed by HPLC-PDA/ESI-MS analysis. A total of 20 compounds were positively identified and twelve out of them were never previously reported in I. tinctoria leaves. The fraction exhibited good radical scavenging activity in DPPH test (IC₅₀  = 0.6657 ± 0.0024 mg/ml) and reducing power (3.87 ± 0.71 ASE/ml), whereas, it neither showed chelating activity nor was able to counteract H₂ O₂ induced oxidative stress damage in Escherichia coli. The antiproliferative effect was evaluated in vitro on two human anaplastic thyroid carcinoma cell lines (CAL-62 and 8505C) by MTT assay. At the highest tested concentration ItJ-EAF significantly reduced (80%) the growth of CAL-62 cells. No cytotoxicity against Artemia salina was observed. It can be concluded that I. tinctoria cauline leaves represent a source of phenolic compounds which could be potentially used as chemopreventive or adjuvant agents against cancer.

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.

PARP inhibitor olaparib increases the oncolytic activity of dl922-947 in in vitro and in vivo model of anaplastic thyroid carcinoma

PARP inhibitors are mostly effective as anticancer drugs in association with DNA damaging agents. We have previously shown that the oncolytic adenovirus dl922-947 induces extensive DNA damage, therefore we hypothesized a synergistic antitumoral effect of the PARP inhibitor olaparib in association with dl922-947. Anaplastic thyroid carcinoma was chosen as model since it is a particularly aggressive tumor and, because of its localized growth, it is suitable for intratumoral treatment with oncolytic viruses. Here, we show that dl922-947 infection induces PARP activation, and we confirm in vitro and in vivo that PARP inhibition increases dl922-947 replication and oncolytic activity. In vitro, the combination with olaparib exacerbates the appearance of cell death markers, such as Annexin V positivity, caspase 3 cleavage, cytochrome C release and propidium iodide permeability. In vivo, we also observed a better viral distribution upon PARP inhibition. Changes in CD31 levels suggest a direct effect of olaparib on tumor vascularization and on the viral distribution within the tumor mass. The observation that PARP inhibition enhances the effects of dl922-947 is highly promising not only for the treatment of anaplastic thyroid carcinoma but, in general, for the treatment of other tumors that could benefit from the use of oncolytic viruses.

Expression of hedgehog signalling pathway in anaplastic thyroid cancer

The purpose of this work is to study the activation of the hedgehog signalling pathway is associated with tumour progression in various types of cancer, hence the development of specific antagonists raises hope for new therapeutic strategies. Therefore, the expression of hedgehog pathway components in anaplastic thyroid cancer (ATC) and effects of the hedgehog inhibitor Cyclopamine on ATC cells were investigated in this study. Expression of the ligand Sonic Hedgehog (SHh), the transmembrane protein Smoothened (Smo), the receptor Patched (Ptc) and the target gene Gli-1 was evaluated in two ATC cell lines (Hth 74, C643) by RT-PCR and in tumour specimens by immunohistochemistry. The corresponding gene products were examined by western blotting analysis. After treatment with different concentrations of Cyclopamine the time-dependent course of cell viability in ATC cell lines was evaluated by MTT assay. SHh, Smo, Ptc and Gli were clearly expressed on mRNA and protein levels in both cell lines and in tumour samples (41 %SHh, 65 %Smo, 65 %Ptc and 65 %Gli). Treatment with Cyclopamine showed a time- and dose-dependent inhibition of cell numbers with IC50 values between 1 and 4 μM in both cell lines, comparable to other types of cancer. In conclusion, we believe that the hedgehog pathway is expressed in anaplastic thyroid carcinoma specimens and proliferation of ATC cell lines can be influenced by the Hh inhibitor Cyclopamine. Aberrant activation of this pathway might be involved in the aggressive biology of anaplastic cancer and further evaluation regarding a possible clinical impact of pathway inhibition is warranted.

Tolfenamic acid induces apoptosis and growth inhibition in anaplastic thyroid cancer: Involvement of nonsteroidal anti-inflammatory drug-activated gene-1 expression and intracellular reactive oxygen species generation

Nonsteroidal anti-inflammatory drugs (NSAIDs) are usually used for the treatment of inflammatory diseases. However, certain NSAIDs also have antitumor activities in various cancers, including head and neck cancer, through cyclooxygenase-dependent or independent pathways. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a TGF-β superfamily protein, is induced by NSAIDs and has been shown to be induced by several antitumorigenic compounds and to exhibit proapoptotic and antitumorigenic activities. In this report, we demonstrate for the first time that tolfenamic acid (TA) transcriptionally induced the expression of NAG-1 during TA-induced apoptosis of anaplastic thyroid cancer (ATC) cells. TA reduced the viability of ATC cells in a dose-dependent manner and induced apoptosis, findings that were coincident with NAG-1 expression. Overexpression of the NAG-1 gene using cDNA enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. Subsequently, we found that intracellular ROS generation plays an important role in activating the proapoptotic protein NAG-1. Then, we confirmed antitumorigenic effects of TA in a nude mouse orthotopic ATC model, and this result accompanied the augmentation of NAG-1 expression and ROS generation in tumor tissue. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression and ROS generation in in vitro and in vivo ATC models, providing a novel mechanistic explanation and indicating a potential chemotherapeutic approach for treatment of ATC.

Carboplatin synergistically triggers the efficacy of photodynamic therapy via caspase 3-, 8-, and 12-dependent pathways in human anaplastic thyroid cancer cells

Anaplastic thyroid cancer is one of the most aggressive forms of malignancies which grow very rapidly. Several conventional methods have been applied for the treatment of anaplastic thyroid cancer, but most of them were not successful in complete recovery of the patients. Therefore, a combination of two or more conventional modalities is being applied nowadays for the treatment of this type of cancer. In this present study, the combination of photodynamic therapy (PDT) and chemotherapy has been studied in anaplastic thyroid cancer. Human anaplastic thyroid cancer cells FRO were treated with a chemotherapy drug, carboplatin (cis-diammine-1,1-cyclobutanedicarboxyl-ateplatinum II (CBDCA)), and radachlorin-mediated PDT individually and in combination. Several parameters like cytotoxicity assay by MTT, apoptosis study by annexin V and propidium iodide, cell cycle analysis by flow cytometry, confocal microscopic study, and Western blot analysis for different apoptosis-related proteins like Bax, cytochrome c, caspases 3, 9, 8, and 12, etc. were studied to check the efficacy of the combination treatment as well as to find out the mechanism of this enhanced efficacy. Results showed that both PDT and CBDCA can induce apoptosis in FRO cells. However, a synergistic efficacy was observed when the cells were treated with CBDCA and PDT in combination. Changes in mitochondrial membrane potential and an increase in reactive oxygen species generation were observed in combination treatments. The enhanced expression of different apoptotic pathway-related proteins like Bax, cytochrome c, caspase 3, caspase 8, caspase 12, etc. also confirmed the higher efficacy of combination treatment. Therefore, with this combination treatment, not only a higher efficacy can be achieved but also the effective dose of the chemotherapy drug can be reduced, and hence, the adverse side effects of the chemotherapy drugs can also be controlled.

Vandetanib: opening a new treatment practice in advanced medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is frequently diagnosed in a locally advanced or metastatic stage, and 10-year survival rates in these cases are below 20 %. Cytotoxic chemotherapy has no significant impact on overall or progression-free survival. Vandetanib (Caprelsa(®), AstraZeneca) is a once-daily oral tyrosine kinase inhibitor that selectively inhibits signalling mediated by growth-factor receptor tyrosine kinase RET (constitutively activated in roughly 60 % of all MTCs), vascular endothelial growth-factor receptors 2 and 3, and epidermal growth-factor receptors. It is the first systemic drug with demonstrated anti-tumor benefits in advanced MTC, and it has recently been approved for locally advanced or metastatic MTC by the United States Food and Drug Administration (April 2011) and the European Medicines Agency (February 2012). This review, starting from the phases II and III efficacy and safety data that led to these approvals, explores important issues related to dosing, patient selection, and strategies for managing the substantial risk of toxicity associated with the drug (including life-threatening cardiac events that are the subject of a black-box warning in the United States). All these issues still remain to be defined. Vandetanib is becoming a standard of care for symptomatic, progressive, metastatic MTCs, to be used selectively in those patients who are likely to benefit from it.