Successful treatment of anaplastic thyroid carcinoma with a combination of oral valproic acid, chemotherapy, radiation and surgery

Anaplastic thyroid cancer: Genetic roles, targeted therapy, and immunotherapy

Anaplastic thyroid cancer (ATC) stands as the most formidable form of thyroid malignancy, presenting a persistent challenge in clinical management. Recent years have witnessed a gradual unveiling of the intricate genetic underpinnings governing ATC through next-generation sequencing. The emergence of this genetic landscape has paved the way for the exploration of targeted therapies and immunotherapies in clinical trials. Despite these strides, the precise mechanisms governing ATC pathogenesis and the identification of efficacious treatments demand further investigation. Our comprehensive review stems from an extensive literature search focusing on the genetic implications, notably the pivotal MAPK and PI3K-AKT-mTOR signaling pathways, along with targeted therapies and immunotherapies in ATC. Moreover, we screen and summarize the advances and challenges in the current diagnostic approaches for ATC, including the invasive tissue sampling represented by fine needle aspiration and core needle biopsy, immunohistochemistry, and 18F-fluorodeoxyglucose positron emission tomography/computed tomography. We also investigate enormous studies on the prognosis of ATC and outline independent prognostic factors for future clinical assessment and therapy for ATC. By synthesizing this literature, we aim to encapsulate the evolving landscape of ATC oncology, potentially shedding light on novel pathogenic mechanisms and avenues for therapeutic exploration.

Valproic acid radiosensitizes anaplastic thyroid cells through a decrease of the DNA damage repair capacity

BACKGROUND

Anaplastic thyroid cancer (ATC) represents a rare lethal human malignancy with poor prognosis. Multimodality treatment, including radiotherapy, is recommended to improve local control and survival. Valproic acid (VA) is a clinically available histone deacetylase inhibitor with a well-documented side effect profile. In this study, we aim to investigate the combined effect of VA with photon irradiation in vitro.

METHODS

Anaplastic thyroid cancer cells (8505c) were used to investigate the radiosensitizing effect of VA.

RESULTS

VA sensitized cells to photon irradiation. VA increased radiation-induced apoptosis and radiation-induced DNA damage measured by γH2AX foci induction. Furthermore, VA prolonged γH2AX foci disappearance over time in irradiated cells and decreased the radiation-induced levels of mRNA of key DNA damage repair proteins of the homologous recombination (HR) and the nonhomologous end joining (NHEJ) pathways.

CONCLUSIONS

VA at a clinically safe dose enhance the radiosensitivity of 8505c cells through an increase in radiation-induced apoptosis and a disruption in the molecular mechanism of HR and NHEJ DNA damage repair pathways.

HDACs as an emerging target in endocrine tumors: a comprehensive review

INTRODUCTION

The pathogenic role of deregulated histone (de-)acetylation by histone deacetyles (HDACs) has been demonstrated in several human cancers. While some HDAC inhibitors (HDACi) have been approved for individual entities, for endocrine tumors such translation into clinical practice has not yet been achieved.

AREAS COVERED

Relevant results identified by structured searches in PubMed as well as in reference lists are summarized in a narrative review to discuss the current knowledge of HDAC involvement and their therapeutic relevance in endocrine tumors. For thyroid, neuroendocrine, and adrenal tumors, various oncogenic mechanisms of HDAC deregulation and effects of HDAC inhibitors (HDACi) have been identified in preclinical studies including direct cancer cell toxicity and modification of differentiation status.

EXPERT OPINION

Based on positive pre-clinical results, the research on HDAC (inhibition) in the various endocrine tumors should be intensified - yet, it needs to be considered that i) HDACs' oncogenic actions might constitute only a part of epigenetic mechanisms driving cancer, ii) individual HDAC has different roles in different endocrine tumor entities, iii) inhibition of HDACs might be especially attractive in combination with conventional or other targeted therapies, and iv) new HDAC-inhibiting drugs with improved specificity or functionally modified HDACi might further improve their efficacy.

Epigenetic modification and BRAF gene mutation in thyroid carcinoma

Thyroid cancer remains the most prevailing endocrine malignancy, and a progressively increasing incidence rate has been observed in recent years, with 95% of thyroid cancer represented by differentiated thyroid carcinomas. The genetics and epigenetics of thyroid cancer are gradually increasing, and gene mutations and methylation changes play an important roles in its occurrence and development. Although the role of RAS and BRAF mutations in thyroid cancer have been partially clarified,but the pathogenesis and molecular mechanisms of thyroid cancer remain to be elucidated. Epigenetic modification refer to genetic modification that does not change the DNA sequence of a gene but causes heritable phenotypic changes in its expression. Epigenetic modification mainly includes four aspects: DNA methylation, chromatin remodelling, noncoding RNA regulation, and histone modification. This article reviews the importance of thyroid cancer epigenetic modification and BRAF gene mutation in the treatment of thyroid cancer.

Anaplastic Thyroid Carcinoma: Current Issues in Genomics and Therapeutics

PURPOSE OF REVIEW

Anaplastic thyroid carcinoma is a type of thyroid carcinoma with the most aggressive biological behaviour amongst thyroid cancer. Here, we review the current genomic and the impacts of advances in therapies to improve the management of patients with the cancer.

RECENT FINDINGS

Common mutations being identified in anaplastic thyroid carcinoma are p53 and TERT promoter mutations. Other common mutated genes included BRAF, RAS, EIF1AX, PIK3CA, PTEN and AKT1, SWI/SNF, ALK and CDKN2A. Changes in expression of different microRNAs are also involved in the pathogenesis of anaplastic thyroid carcinoma. Curative resection combined with radiotherapy and combination chemotherapies (such as anthracyclines, platins and taxanes) has been shown to have effects in the treatment of some patients with anaplastic thyroid carcinoma. Newer molecular targeted therapies in clinical trials target mostly the cell membrane kinase and downstream proteins. These include targeting the EGFR, FGFR, VEGFR, c-kit, PDGFR and RET on the cell membrane as well as VEGF itself and the downstream targets such as BRAF, MEK and mTOR. Immunotherapy is also being tested in the cancer. Updated knowledge of genomic as well as clinical trials on novel therapies is needed to improve the management of the patients with this aggressive cancer.

The combination of histone deacetylase inhibitors and radiotherapy: a promising novel approach for cancer treatment

HDAC inhibitors (HDACi) play an essential role in various cellular processes, such as differentiation and transcriptional regulation of key genes and cytostatic factors, cell cycle arrest and apoptosis that facilitates the targeting of epigenome of eukaryotic cells. In the majority of cancers, only a handful of patients receive optimal benefit from chemotherapeutics. Additionally, there is emerging interest in the use of HDACi to modulate the effects of ionizing radiations. The use of HDACi with radiotherapy, with the goal of reaching dissimilar, often distinct pathways or multiple biological targets, with the expectation of synergistic effects, reduced toxicity and diminished intrinsic and acquired resistance, conveys an approach of increasing interest. In this review, the clinical potential of HDACi in combination with radiotherapy is described as an efficient synergy for cancer treatment will be overviewed.

HDAC Inhibition Induces PD-L1 Expression in a Novel Anaplastic Thyroid Cancer Cell Line

While papillary thyroid cancer (PTC) has largely favorable prognosis, anaplastic thyroid cancer (ATC) is a rare but extremely aggressive malignancy with grim clinical outcome. Even though new therapeutic options are emerging for ATC, additional preclinical models and novel combinations are needed for specific subsets of patients. We established a novel cell line (PF49) from the malignant pleural effusion of a 68-year-old male patient with ATC that rapidly transformed from a BRAF and TERT promoter mutant PTC. PF49 cells demonstrated a robust migratory activity in vitro and strong invasive capacity in vivo in a pleural carcinosis model. Combined BRAF and MEK inhibition decreased the proliferation and migration of PF49 cells, however could not induce cell death. Importantly, HDAC inhibitor treatment with SAHA or valproic acid induced cell cycle arrest and strongly increased PD-L1 expression of the tumor cells. Induction of PD-L1 expression was also present when paclitaxel-cisplatin chemotherapeutic treatment was combined with HDAC inhibitor treatment. Increased PD-L1 expression after HDAC inhibition was recapitulated in an international ATC cell model. Our data suggest that HDAC inhibition alone or in combination with standard chemotherapy may potentiate anaplastic thyroid cancer cells for immunotherapy.

Key actors in cancer therapy: epigenetic modifiers

Epigenetic reprogramming plays a crucial role in the tumorigenicity and maintenance of tumor-specific gene expression that especially occurs through DNA methylation and/or histone modifications. It has well-defined mechanisms. It is known that alterations in the DNA methylation pattern and/or the loss of specific histone acetylation/methylation markers are related to several hallmarks of cancer, such as drug resistance, stemness, epithelial-mesenchymal transition, and metastasis. It has also recently been highlighted that epigenetic alterations are critical for the regulation of the stemlike properties of cancer cells (tumor-initiating cells; cancer stem cells). Cancer stem cells are thought to be responsible for the recurrence of cancer which makes the patient return to the clinic with metastatic tumor tissue. Hence, the dysregulation of epigenetic machinery represents potential new therapeutic targets. Therefore, compounds with epigenetic activities have become crucial for developing new therapy regimens (e.g., antimetastatic agents) in the fight against cancer. Here, we review the epigenetic modifiers that have already been used in the clinic and/or in clinical trials, related preclinical studies in cancer therapy, and the smart combination strategies that target cancer stem cells along with the other cancer cells. The emerging role of epitranscriptome (RNA epigenetic) in cancer therapy has also been included in this review as a new avenue and potential target for the better management of cancer-beneficial epigenetic machinery.

Treatment Outcomes in Anaplastic Thyroid Cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is rare, accounting for 1-2% of thyroid malignancies. Median survival is only 3-10 months, and the optimal therapeutic approach has not been established. This study aimed to evaluate outcomes in ATC based on treatment modality.

METHODS

Retrospective review was performed for patients treated at a single institution between 1990 and 2015. Demographic and clinical covariates were extracted from the medical record. Overall survival (OS) was modeled using Kaplan Meier curves for different treatment modalities. Univariate and multivariate analyses were conducted to assess the relationships between treatment and disease characteristics and OS.

RESULTS

28 patients with ATC were identified (n = 16 female, n = 12 male; n = 22 Caucasian, n = 6 African-American; median age 70.9). Majority presented as Stage IVB (71.4%). Most patients received multimodality therapy. 19 patients underwent local surgical resection. 21 patients received locoregional external beam radiotherapy (EBRT) with a median cumulative dose of 3,000 cGy and median number of fractions of 16. 14 patients received systemic therapy (n = 11 concurrent with EBRT), most commonly doxorubicin (n = 9). 16 patients were never disease free, 11 patients had disease recurrence, and 1 patient had no evidence of disease progression. Median OS was 4 months with 1-year survival of 17.9%. Regression analysis showed that EBRT (HR: 0.174; 95% CI: 0.050-0.613; p=0.007) and surgical resection (HR: 0.198; 95% CI: 0.065-0.598; p=0.004) were associated with improved OS. Administration of chemotherapy was not associated with OS.

CONCLUSIONS

Anaplastic thyroid cancer patients receiving EBRT to the thyroid area/neck and/or surgical resection had better OS than patients without these therapies, though selection bias likely contributed to improved outcomes since patients who can undergo these therapies tend to have better performance status. Prognosis remains poor overall, and new therapeutic approaches are needed to improve outcomes.

Epigenetic modifications in poorly differentiated and anaplastic thyroid cancer

Well-differentiated thyroid cancer accounts for the majority of endocrine malignancies and, in general, has an excellent prognosis. In contrast, the less common poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma (ATC) are two of the most aggressive human malignancies. Recently, there has been an increased focus on the epigenetic alterations underlying thyroid carcinogenesis, including those that drive PDTC and ATC. Dysregulated epigenetic candidates identified include the Aurora group, KMT2D, PTEN, RASSF1A, multiple non-coding RNAs (ncRNA), and the SWI/SNF chromatin-remodeling complex. A deeper understanding of the signaling pathways affected by epigenetic dysregulation may improve prognostic testing and support the advancement of thyroid-specific epigenetic therapies. This review outlines the current understanding of epigenetic alterations observed in PDTC and ATC and explores the potential for exploiting this understanding in developing novel therapeutic strategies.

Combination Therapy With Histone Deacetylase Inhibitors (HDACi) for the Treatment of Cancer: Achieving the Full Therapeutic Potential of HDACi

Genetic and epigenetic changes in DNA are involved in cancer development and tumor progression. Histone deacetylases (HDACs) are key regulators of gene expression that act as transcriptional repressors by removing acetyl groups from histones. HDACs are dysregulated in many cancers, making them a therapeutic target for the treatment of cancer. Histone deacetylase inhibitors (HDACi), a novel class of small-molecular therapeutics, are now approved by the Food and Drug Administration as anticancer agents. While they have shown great promise, resistance to HDACi is often observed and furthermore, HDACi have shown limited success in treating solid tumors. The combination of HDACi with standard chemotherapeutic drugs has demonstrated promising anticancer effects in both preclinical and clinical studies. In this review, we summarize the research thus far on HDACi in combination therapy, with other anticancer agents and their translation into preclinical and clinical studies. We additionally highlight the side effects associated with HDACi in cancer therapy and discuss potential biomarkers to either select or predict a patient's response to these agents, in order to limit the off-target toxicity associated with HDACi.

The Histone Deacetylase Inhibitor Valproic Acid Sensitizes Gemcitabine-Induced Cytotoxicity in Gemcitabine-Resistant Pancreatic Cancer Cells Possibly Through Inhibition of the DNA Repair Protein Gamma-H2AX

BACKGROUND

Gemcitabine (GEM) remains a major chemotherapeutic drug for pancreatic cancer, but resistance to GEM has been a big problem, as its response rate has been decreasing year by year.

METHODS

The effect of the histone deacetylase inhibitor (HDAI) valproic acid (VPA) was compared with tranilast and RI-1 as a combinatorial treatment with GEM in four pancreatic cancer cell lines, BxPC-3, PK45p, MiaPaCa-2 and PK59. Cell viability assays were carried out to check the cytotoxic effects, western blotting was carried out for DNA repair mechanisms, and localization was determined by immunofluorescence.

RESULTS

The sensitization factors (i.e., the fold ratio of cell viability for GEM/GEM plus drug) reveal that VPA increases the cytotoxic sensitization to GEM at approximately 2.7-fold, 1.2-fold, 1.5-fold and 2.2-fold in BxPC-3, MiaPaCa-2, PK-45p and PK-59 cell lines, respectively. Moreover, GEM induces activation of the DNA repair protein H2AX proportional to the dosage. Interestingly, however, this effect can be abrogated by VPA.

CONCLUSIONS

These results indicate that VPA enhances GEM-induced cytotoxicity in GEM-resistant pancreatic cancer cells, possibly through inhibition of DNA damage signaling and repair. Our study suggests VPA as a potential therapeutic agent for combinatorial treatment with GEM in pancreatic cancer.

Spanish consensus for the management of patients with anaplastic cell thyroid carcinoma

Anaplastic thyroid cancer (ATC) is the most aggressive solid tumor and almost uniformly lethal in humans. The Boards of the Thyroid Cancer Group of the Spanish Society of Endocrinology and Nutrition and the Grupo Español de Enfermedades Huérfanas e Infrecuentes of the Spanish Society of Oncology requested that an independent task force draft a more comprehensive consensus statement regarding ATC. All relevant literature was reviewed, including serial PubMed searches together with additional articles. This is the first, comprehensive Spanish consensus statement for ATC and includes the characteristics, diagnosis, initial evaluation, treatment goals, recommendations and modalities for locoregional and advanced disease, palliative care options, surveillance, and long-term monitoring. Newer systemic therapies are being investigated, but more effective combinations are needed to improve patient outcomes. Though more aggressive radiotherapy has reduced locoregional recurrences, median overall survival has not improved in more than 50 years.

RhoB upregulation leads to either apoptosis or cytostasis through differential target selection

Anaplastic thyroid carcinoma is a highly aggressive undifferentiated carcinoma with a mortality rate near 100% due to an assortment of genomic abnormalities which impede the success of therapeutic options. Our laboratory has previously identified that RhoB upregulation serves as a novel molecular therapeutic target and agents upregulating RhoB combined with paclitaxel lead to antitumor synergy. Knowing that histone deacetylase 1 (HDAC1) transcriptionally suppresses RhoB, we sought to extend our findings to other HDACs and to identify the HDAC inhibitor (HDACi) that optimally synergize with paclitaxel. Here we identify HDAC6 as a newly discovered RhoB repressor. By using isoform selective HDAC inhibitors (HDACi) and shRNAs, we show that RhoB has divergent downstream signaling partners, which are dependent on the HDAC isoform that is inhibited. When RhoB upregulates only p21 (cyclin kinase inhibitor) using a class I HDACi (romidepsin), cells undergo cytostasis. When RhoB upregulates BIMEL using class II/(I) HDACi (belinostat or vorinostat), apoptosis occurs. Combinatorial synergy with paclitaxel is dependent upon RhoB and BIMEL while upregulation of RhoB and only p21 blocks synergy. This bifurcated regulation of the cell cycle by RhoB is novel and silencing either p21 or BIMEL turns the previously silenced pathway on, leading to phenotypic reversal. This study intimates that the combination of belinostat/vorinostat with paclitaxel may prove to be an effective therapeutic strategy via the novel observation that class II/(I) HDACi antagonize HDAC6-mediated suppression of RhoB and subsequent BIMEL, thereby promoting antitumor synergy. These overall observations may provide a mechanistic understanding of optimal therapeutic response.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

Spanish consensus for the management of patients with anaplastic cell thyroid carcinoma

Anaplastic thyroid cancer (ATC) is the most aggressive solid tumour known and is a rare but highly lethal form of thyroid cancer that requires a multidisciplinary team approach. No Spanish consensus exists for management of patients with ATC. The Thyroid Cancer Group of the Spanish Society of Endocrinology and Nutrition and the GETHI (Grupo Español de Enfermedades Huérfanas e Infrecuentes) of the Spanish Society of Oncology, in agreement with the Boards of these Societies, commissioned an independent task force to develop a wide consensus on ATC. The relevant literature was reviewed, including serial PubMed searches supplemented with additional articles. The consensus includes the characteristics, diagnosis, initial evaluation, establishment of treatment goals, approaches to locoregional disease (surgery, radiotherapy, systemic therapy, supportive care during active treatment), approaches to advanced/metastatic disease, palliative care options, monitoring, and long-term follow-up of ATC. For operable disease, a combination of radical surgery with adjuvant radiotherapy or chemotherapy, using agents such as doxorubicin, cisplatin and paclitaxel, is the best treatment strategy. Cytotoxic drugs are poorly effective for advanced/metastatic ATC. On the other hand, targeted agents may represent a viable therapeutic option. Patients with stage IVA/IVB resectable disease have the best prognosis, particularly if a multimodal approach is used, and some stage IVB unresectable patients may respond to aggressive therapy. Patients with stage IVC disease should be considered for clinical trials or for hospice/palliative care depending on their preference. This is the first Spanish consensus for ATC, and provides recommendations for management of this extremely aggressive malignancy. Novel systemic therapies are being tested, and more effective combinations are needed to improve patient outcomes. Although more aggressive radiotherapy has reduced locoregional recurrence, mean overall survival has not improved in the past 50 years.

Chromatin-regulating proteins as targets for cancer therapy

Chromatin-regulating proteins represent a large class of novel targets for cancer therapy. In the context of radiotherapy, acetylation and deacetylation of histones by histone acetyltransferases (HATs) and histone deacetylases (HDACs) play important roles in the repair of DNA double-strand breaks generated by ionizing irradiation, and are therefore attractive targets for radiosensitization. Small-molecule inhibitors of HATs (garcinol, anacardic acid and curcumin) and HDACs (vorinostat, sodium butyrate and valproic acid) have been shown to sensitize cancer cells to ionizing irradiation in preclinical models, and some of these molecules are being tested in clinical trials, either alone or in combination with radiotherapy. Meanwhile, recent large-scale genome analyses have identified frequent mutations in genes encoding chromatin-regulating proteins, especially in those encoding subunits of the SWI/SNF chromatin-remodeling complex, in various human cancers. These observations have driven researchers toward development of targeted therapies against cancers carrying these mutations. DOT1L inhibition in MLL-rearranged leukemia, EZH2 inhibition in EZH2-mutant or MLL-rearranged hematologic malignancies and SNF5-deficient tumors, BRD4 inhibition in various hematologic malignancies, and BRM inhibition in BRG1-deficient tumors have demonstrated promising anti-tumor effects in preclinical models, and these strategies are currently awaiting clinical application. Overall, the data collected so far suggest that targeting chromatin-regulating proteins is a promising strategy for tomorrow's cancer therapy, including radiotherapy and molecularly targeted chemotherapy.

The Beneficial Effects of Valproic Acid in Thyroid Cancer Are Mediated through Promoting Redifferentiation and Reducing Stemness Level: An In Vitro Study

Valproic acid (VPA) has been identified as a histone deacetylase inhibitor, inducing differentiation in transformed cells. However, no study has shown the effect of VPA in the redifferentiation induction and stemness of anaplastic thyroid. The main objective of this study was to evaluate the efficacy of VPA as a differentiation therapy agent in human thyroid cancer based on its effect on stemness and differentiation process. Indications for differentiation of 8305C and B-CPAP cell lines following VPA treatment were obtained by analyzing cell proliferation rate, morphological changes, adherent-dependent colony formation, and Hoechst 33342 staining. The expressions of stemness, differentiation, and aggressiveness specific marker genes were measured by quantitative RT-PCR. VPA treatment effectively showed growth inhibition in both cell lines. The high nuclear-cytoplasmic (N : C) ratio of 8305C cells markedly decreased and treated cells became more epithelial-like. Treated cells showed stronger Hoechst 33342 fluorescence compared with control cells. The hTERT and OCT-4 reduction was paralleled with adherent-dependent colony formation decrement in both cell lines. VPA effectively induced NIS and TTF-1 in anaplastic cells, it whereas showed no clear pattern in papillary cell line. VPA treatment also resulted in the reduction of MMP-2 and MMP-9. These finding suggest that VPA could redifferentiate the anaplastic thyroid cancer cells.

Genetics and epigenetics of sporadic thyroid cancer

Thyroid carcinoma is the most common endocrine malignancy, and although the disease generally has an excellent prognosis, therapeutic options are limited for patients not cured by surgery and radioiodine. Thyroid carcinomas commonly contain one of a small number of recurrent genetic mutations. The identification and study of these mutations has led to a deeper understanding of the pathophysiology of this disease and is providing new approaches to diagnosis and therapy. Papillary thyroid carcinomas usually contain an activating mutation in the RAS cascade, most commonly in BRAF and less commonly in RAS itself or through gene fusions that activate RET. A chromosomal translocation that results in production of a PAX8-PPARG fusion protein is found in follicular carcinomas. Anaplastic carcinomas may contain some of the above changes as well as additional mutations. Therapies that are targeted to these mutations are being used in patient care and clinical trials.

Autophagy and thyroid carcinogenesis: genetic and epigenetic links

Thyroid cancer is the most common cancer of the endocrine system and is responsible for the majority of deaths from endocrine malignancies. Although a large proportion of thyroid cancers belong to well differentiated histologic subtypes, which in general show a good prognosis after surgery and radioiodine ablation, the treatment of radio-resistant papillary-type, of undifferentiated anaplastic, and of medullary-type thyroid cancers remains unsatisfactory. Autophagy is a vesicular process for the lysosomal degradation of protein aggregates and of damaged or redundant organelles. Autophagy plays an important role in cell homeostasis, and there is evidence that this process is dysregulated in cancer cells. Recent in vitro preclinical studies have indicated that autophagy is involved in the cytotoxic response to chemotherapeutics in thyroid cancer cells. Indeed, several oncogenes and oncosuppressor genes implicated in thyroid carcinogenesis also play a role in the regulation of autophagy. In addition, some epigenetic modulators involved in thyroid carcinogenesis also influence autophagy. In this review, we highlight the genetic and epigenetic factors that mechanistically link thyroid carcinogenesis and autophagy, thus substantiating the rationale for an autophagy-targeted therapy of aggressive and radio-chemo-resistant thyroid cancers.

New targeted therapies and other advances in the management of anaplastic thyroid cancer

PURPOSE OF REVIEW

Anaplastic thyroid cancer is the most aggressive solid tumor known to humans. Even when found in a localized form, the prognosis is grave. For metastatic disease, there has been little effect on survival using traditional chemotherapy.

RECENT FINDINGS

Over a five-decade interval, there has been little progress in the treatment of this malignancy. However, targeted agents represent a new mode of treatment, and some studies have shown encouraging preclinical results. Combretastatin has shown activity in phase 1 and phase II trials; although the registration phase III study failed to meet its accrual goals, it did appear to show some benefit, especially in younger patients.

SUMMARY

Combinations of this compound and other targeted agents may prove to be a breakthrough in an otherwise untreatable cancer.

Aggressive multimodal approach for anaplastic thyroid cancer and long-term survival

Anaplastic thyroid cancer (ATC) comprises 1-2% of all thyroid cancers and is one of the most aggressive cancers with a median survival rate of around four months. The average 5-year survival rate has been reported to be around 3.6%. In this paper, we have discussed management and prognostic variables of a patient with ATC who has survived for more than 5 years. A 59-year-old female was referred to our facility for an elective thyroid and parathyroidectomy for concerns of thyroid papillary cancer and hyperparathyroidism. At the time of surgery, the tumor mass had invaded the muscular layer of esophagus; radicle thyroidectomy parathyroidectomy along with removal of muscle layer of esophagus was performed, and diagnosis of ATC was made. The patient was treated with chemoradiation with a good treatment response and no recurrence of tumor for two and a half years until PET/CT followed by wedge biopsy of lung confirmed ATC recurrence. The patient was treated with another course of radiation treatment with a good treatment response. Since then, the patient has been following in our outpatient oncology clinic and has no evidence of tumor recurrence. Aggressive multimodal approach of combining radicle surgery with chemoradiation treatment in select patients of ATC with no distant metastasis helps improve prognosis.

Histone deacetylase inhibitors as radiosensitisers: effects on DNA damage signalling and repair

Many cancers display increased expression of histone deacetylases (HDACs) and therefore transcriptionally inactive chromatin, resulting in the downregulation of genes including tumour suppressor and DNA repair genes. Histone deacetylase inhibitors (HDACi) are a heterogeneous group of epigenetic therapeutics, showing promising anticancer effects in both pre-clinical and clinical settings, in particular the effect of radiosensitisation when administered in combination with radiotherapy. Radiotherapy remains one of the most common forms of cancer treatment, leading to cell death through the induction of DNA double-strand breaks (DSBs). Cells have developed mechanisms to repair such DSB through two major pathways: non-homologous end-joining and homologous recombination. Here, we explore the current evidence for the use of HDACi in combination with irradiation, focusing on the effects of HDACi on DNA damage signalling and repair in vitro. In addition, we summarise the clinical evidence for using HDACi with radiotherapy, a growing area of interest with great potential clinical utility.

Epigenetics modifications and therapeutic prospects in human thyroid cancer

At present no successful treatment is available for advanced thyroid cancer, which comprises poorly differentiated, anaplastic, and metastatic or recurrent differentiated thyroid cancer not responding to radioiodine. In the last few years, biologically targeted therapies for advanced thyroid carcinomas have been proposed on the basis of the recognition of key oncogenic mutations. Although the results of several phase II trials look promising, none of the patients treated had a complete response, and only a minority of them had a partial response, suggesting that the treatment is, at best, effective in stabilizing patients with progressive disease. "Epigenetic" refers to the study of heritable changes in gene expression that occur without any alteration in the primary DNA sequence. The epigenetic processes establish and maintain the global and local chromatin states that determine gene expression. Epigenetic abnormalities are present in almost all cancers and, together with genetic changes, drive tumor progression. Various genes involved in the control of cell proliferation and invasion (p16INK4A, RASSF1A, PTEN, Rap1GAP, TIMP3, DAPK, RARβ2, E-cadherin, and CITED1) as well as genes specific of thyroid differentiation (Na+/I- symport, TSH receptor, pendrin, SL5A8, and TTF-1) present aberrant methylation in thyroid cancer. This review deals with the most frequent epigenetic alterations in thyroid cancer and focuses on epigenetic therapy, whose goal is to target the chromatin in rapidly dividing tumor cells and potentially restore normal cell functions. Experimental data and clinical trials, especially using deacetylase inhibitors and demethylating agents, are discussed.

Effect of valproic acid on the outcome of glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM) is the most aggressive type of primary brain tumor. It is a rapidly progressive, highly recurrent, fatal intracranial neoplasm, and the demand for novel treatment is urgent. Valproic acid (VPA) is a potential anticancer agent that belongs to a class of histone deacetylase (HDAC) inhibitors, targeting the epigenetic control of gene functions in cancer cells. This drug has been administered for the prevention or treatment of seizure disorder in GBM patients; therefore, a retrospective analysis may further our understanding of the effect of VPA on GBM patients.

MATERIALS AND METHODS

A retrospective analysis of 102 patients with GBM was conducted to study the effects of VPA on disease outcome. Tumor samples from seven patients receiving VPA treatment between the first and second operations were obtained in order to verify the HDAC inhibitory activity of VPA in these patients.

RESULTS

In univariate analysis, administration of VPA within 2 weeks of initial diagnosis seemed to confer a survival benefit. However, stratified analysis according to chemotherapy showed that VPA did not have significant impact on the GBM patients' overall survival. Analysis of tissue samples from these patients revealed that a small subset of patients had increased histone acetylation after VPA treatment.

CONCLUSION

VPA treatment, when administered according to a protocol targeting seizure control, may result in HDAC inhibition in a small subset of patients, but does not significantly affect overall patient survival. Early administration of VPA as an adjunct to temozolomide chemotherapy may have its merits, but the optimal dosing schedule and target serum level require further investigation.

MiR-129-5p is required for histone deacetylase inhibitor-induced cell death in thyroid cancer cells

The molecular mechanism responsible for the antitumor activity of histone deacetylase inhibitors (HDACi) remains elusive. As HDACi have been described to alter miRNA expression, the aim of this study was to characterize HDACi-induced miRNAs and to determine their functional importance in the induction of cell death alone or in combination with other cancer drugs. Two HDACi, trichostatin A and vorinostat, induced miR-129-5p overexpression, histone acetylation and cell death in BCPAP, TPC-1, 8505C, and CAL62 cell lines and in primary cultures of papillary thyroid cancer (PTC) cells. In addition, miR-129-5p alone was sufficient to induce cell death and knockdown experiments showed that expression of this miRNA was required for HDACi-induced cell death. Moreover, miR-129-5p accentuated the anti-proliferative effects of other cancer drugs such as etoposide or human α-lactalbumin made lethal for tumor cells (HAMLET). Taken together, our data show that miR-129-5p is involved in the antitumor activity of HDACi and highlight a miRNA-driven cell death mechanism.

Anaplastic thyroid carcinoma: palliation or treatment?

PURPOSE OF REVIEW

To review the recent published literature on the topic of anaplastic thyroid carcinoma and discern if significant advances have occurred that alter the historically poor prognosis associated with this diagnosis.

RECENT FINDINGS

Surgical resection for patients with stage IVA disease (intra-thyroidal without extracapsular extension) with postoperative chemoradiation remains the standard recommendation. Care for patients with stage IVB disease, extrathyroidal spread without distant metastases, remains varied and controversial. Research into different molecular therapies (deacetylase inhibitors, tubulin binding compounds, etc.) and the pathogenesis of anaplastic carcinoma continues to evolve. Care for patients with metastatic disease, stage IVC, is focused on quality of life.

SUMMARY

Although occasional reports exist of long-term survivors with anaplastic thyroid carcinoma, the prognosis remains poor. Accurate staging is critical to offering the most appropriate treatment. Multimodality treatment is required if prolonged locoregional control or survival is desired.

Alternative medical treatment for radioiodine-refractory thyroid cancers

Thyroid cancer is one of the most rapidly increasing cancers in many countries. Although most thyroid cancers are differentiated cancers and easily treated with radioiodine (RI), a portion of differentiated and undifferentiated cancers is refractory not only to RI therapy, but also to radiotherapy and chemotherapy. Thus, various alternative therapies have been tested in RI-refractory thyroid cancers. These alternative therapies include two major categories: redifferentiation therapy and recent molecular target therapy. Several clinical trials have investigated these therapies. They demonstrated potential effects of the therapies, although the results have been somewhat limited so far. Thus, the future strategy for undifferentiated thyroid cancers will involve individualized, lesion-specific, and combined therapy. In this review, the basic mechanism of each redifferentiation and molecular target therapy is discussed, and results of recent clinical trials using these therapeutic agents are summarized.

Anaplastic thyroid carcinoma: A comprehensive review of current and future therapeutic options

Anaplastic thyroid carcinoma (ATC) is the rarest, but deadliest histologic type among thyroid malignancies, with a dismal median survival of 3-9 mo. Even though ATC accounts for less than 2% of all thyroid tumors, it is responsible for 14%-39% of thyroid carcinoma-related deaths. ATC clinically presents as a rapidly growing mass in the neck, associated with dyspnoea, dysphagia and vocal cord paralysis. It is usually locally advanced and often metastatic at initial presentation. For operable diseases, the combination of radical surgery with adjuvant radiotherapy or chemotherapy, using agents such as doxorubicin and cisplatin, is the best treatment strategy. Cytotoxic drugs for advanced/metastatic ATC are poorly effective. On the other hand, targeted agents might represent a viable therapeutic option. Axitinib, combretastatin A4, sorafenib and imatinib have been tested in small clinical trials of ATC, with a promising disease control rate ranging from 33% to 75%. Other clinical trials of targeted therapy for thyroid carcinoma are currently ongoing. Biological agents that are under investigation include pazopanib, gefitinib and everolimus. With the very limited therapeutic armamentarium available at the present time, targeted therapy constitutes an exciting new horizon for ATC. In future, biological agents will probably represent the standard of care for this aggressive malignancy, in the same fashion as it has recently occurred for other chemo-refractory tumors, such as kidney and hepatic cancer.

Rational therapeutic combinations with histone deacetylase inhibitors for the treatment of cancer

Histone deacetylases (HDACs) regulate the acetylation of a variety of histone and nonhistone proteins, controlling the transcription and regulation of genes involved in cell cycle control, proliferation, survival, DNA repair and differentiation. Unsurprisingly, HDAC expression is frequently altered in hematologic and solid tumor malignancies. Two HDAC inhibitors (vorinostat and romidepsin) have been approved by the US FDA for the treatment of cutaneous T-cell lymphoma. As single agents, treatment with HDAC inhibitors has demonstrated limited clinical benefit for patients with solid tumors, prompting the investigation of novel treatment combinations with other cancer therapeutics. In this article, the rationales and clinical progress of several combinations with HDAC inhibitors are presented, including DNA-damaging chemotherapeutic agents, radiotherapy, hormonal therapies, DNA methyltransferase inhibitors and various small-molecule inhibitors. The future application of HDAC inhibitors as a treatment for cancer is discussed, examining current hurdles to overcome before realizing the potential of this new approach.

Activating Transcription Factor 3 regulates in part the enhanced tumour cell cytotoxicity of the histone deacetylase inhibitor M344 and cisplatin in combination

Background

Activating Transcription Factor (ATF) 3 is a key regulator of the cellular integrated stress response whose expression has also been correlated with pro-apoptotic activities in tumour cell models. Combination treatments with chemotherapeutic drugs, such as cisplatin, and histone deacetylase (HDAC) inhibitors have been demonstrated to enhance tumour cell cytotoxicity. We recently demonstrated a role for ATF3 in regulating cisplatin-induced apoptosis and others have shown that HDAC inhibition can also induce cellular stress. In this study, we evaluated the role of ATF3 in regulating the co-operative cytotoxicity of cisplatin in combination with an HDAC inhibitor.

Results

The HDAC inhibitor M344 induced ATF3 expression at the protein and mRNA level in a panel of human derived cancer cell lines as determined by Western blot and quantitative RT-PCR analyses. Combination treatment with M344 and cisplatin lead to increased induction of ATF3 compared with cisplatin alone. Utilizing the MTT cell viability assay, M344 treatments also enhanced the cytotoxic effects of cisplatin in these cancer cell lines. The mechanism of ATF3 induction by M344 was found to be independent of MAPKinase pathways and dependent on ATF4, a known regulator of ATF3 expression. ATF4 heterozygote (+/-) and knock out (-/-) mouse embryonic fibroblast (MEF) as well as chromatin immunoprecipitation (ChIP) assays were utilized in determining the mechanistic induction of ATF3 by M344. We also demonstrated that ATF3 regulates the enhanced cytotoxicity of M344 in combination with cisplatin as evidenced by attenuation of cytotoxicity in shRNAs targeting ATF3 expressing cells.

Conclusion

This study identifies the pro-apoptotic factor, ATF3 as a novel target of M344, as well as a mediator of the co-operative effects of cisplatin and M344 induced tumour cell cytotoxicity.

Anaplastic thyroid carcinoma: pathogenesis and emerging therapies

Anaplastic thyroid carcinoma ranges from 1.3 to 9.8% of all thyroid cancers globally. Mutations, amplifications, activation of oncogenes and silencing of tumour suppressor genes contribute to its aggressive behaviour, and recent studies (e.g. microarrays, microRNAs) have provided further insights into its complex molecular dysregulation. Preclinical studies have identified numerous proteins over- or underexpressed that affect critical cellular processes, including transcription, signalling, mitosis, proliferation, cell cycle, apoptosis and adhesion, and a variety of agents that effectively inhibit these processes and tumour growth. In clinical studies of 1771 patients, 64% were women, the median survival was 5 months, and 1-year survival was 20%. The variables associated with survival in some series included age, tumour size, extent of surgery, higher dose radiotherapy, absence of distant metastases at presentation, co-existence of differentiated thyroid cancer and multimodality therapy. However, considerable bias exists in these non-randomised studies. Although more aggressive radiotherapy has reduced locoregional recurrences, the median overall survival has not improved in over 50 years. Newer systemic therapies are being tried, and more effective combinations are needed to improve patient outcomes.

Sodium valproate: an old drug with new roles

Sodium valproate, or Epilim, has been widely used as a broad spectrum, anticonvulsant drug for over 40 years and exhibits a good safety profile. Some of the actions of valproate arise from its more recently described histone deacetylase (HDAC) inhibitory properties and hence it can specifically modulate gene expression. There is now accumulating evidence that HDAC inhibitors may have potential in the treatment of CNS disorders and, in this context, valproate has much potential as a brain-penetrant, clinically available and well tested drug. This article reviews the pharmacology of this remarkable molecule, focusing on its actions as a neuroprotectant and hence with new potential in the treatment of neurodegenerative diseases.