Radiosensitivity enhancement of human thyroid carcinoma cells by the inhibitors of histone deacetylase sodium butyrate and valproic acid

Mechanistic Sequence of Histone Deacetylase Inhibitors and Radiation Treatment: An Overview

Histone deacetylases inhibitors (HDACis) have shown promising therapeutic outcomes in haematological malignancies such as leukaemia, multiple myeloma, and lymphoma, with disappointing results in solid tumours when used as monotherapy. As a result, combination therapies either with radiation or other deoxyribonucleic acid (DNA) damaging agents have been suggested as ideal strategy to improve their efficacy in solid tumours. Numerous in vitro and in vivo studies have demonstrated that HDACis can sensitise malignant cells to both electromagnetic and particle types of radiation by inhibiting DNA damage repair. Although the radiosensitising ability of HDACis has been reported as early as the 1990s, the mechanisms of radiosensitisation are yet to be fully understood. This review brings forth the various protocols used to sequence the administration of radiation and HDACi treatments in the different studies. The possible contribution of these various protocols to the ambiguity that surrounds the mechanisms of radiosensitisation is also highlighted.

The role of microbial metabolites in endocrine tumorigenesis: From the mechanistic insights to potential therapeutic biomarkers

Microbial metabolites have been indicated to communicate with the host's endocrine system, regulating hormone production, immune-endocrine communications, and interactions along the gut-brain axis, eventually affecting the occurrence of endocrine cancer. Furthermore, microbiota metabolites such as short-chain fatty acids (SCFAs) have been found to affect the tumor microenvironment and boost immunity against tumors. SCFAs, including butyrate and acetate, have been demonstrated to exert anti-proliferative and anti-protective activity on pancreatic cancer cells. The employing of microbial metabolic products in conjunction with radiation and chemotherapy has shown promising outcomes in terms of reducing treatment side effects and boosting effectiveness. Certain metabolites, such as valerate and butyrate, have been made known to improve the efficiency of CAR T-cell treatment, whilst others, such as indole-derived tryptophan metabolites, have been shown to inhibit tumor immunity. This review explores the intricate interplay between microbial metabolites and endocrine tumorigenesis, spanning mechanistic insights to the discovery of potential therapeutic biomarkers.

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.

Therapeutic targeting of DNA damage repair pathways guided by homologous recombination deficiency scoring in ovarian cancers

The susceptibility of cells to DNA damage and their DNA repair ability are crucial for cancer therapy. Homologous recombination is one of the major repairing mechanisms for DNA double-strand breaks. Approximately half of ovarian cancer (OvCa) cells harbor homologous recombination deficiency (HRD). Considering that HRD is a major hallmark of OvCas, scholars proposed HRD scoring to evaluate the HRD degree and guide the choice of therapeutic strategies for OvCas. In the last decade, synthetic lethal strategy by targeting poly (ADP-ribose) polymerase (PARP) in HR-deficient OvCas has attracted considerable attention in view of its favorable clinical effort. We therefore suggested that the uses of other DNA damage/repair-targeted drugs in HR-deficient OvCas might also offer better clinical outcome. Here, we reviewed the current small molecule compounds that targeted DNA damage/repair pathways and discussed the HRD scoring system to guide their clinical uses.

Polyphenols as Potent Epigenetics Agents for Cancer

Human diseases such as cancer can be caused by aberrant epigenetic regulation. Polyphenols play a major role in mammalian epigenome regulation through mechanisms and proteins that remodel chromatin. In fruits, seeds, and vegetables, as well as food supplements, polyphenols are found. Compounds such as these ones are powerful anticancer agents and antioxidants. Gallic acid, kaempferol, curcumin, quercetin, and resveratrol, among others, have potent anti-tumor effects by helping reverse epigenetic changes associated with oncogene activation and tumor suppressor gene inactivation. The role dietary polyphenols plays in restoring epigenetic alterations in cancer cells with a particular focus on DNA methylation and histone modifications was summarized. We also discussed how these natural compounds modulate gene expression at the epigenetic level and described their molecular targets in cancer. It highlights the potential of polyphenols as an alternative therapeutic approach in cancer since they modulate epigenetic activity.

Histone Deacetylases and Their Potential as Targets to Enhance Tumour Radiosensitisation

In mammalian cells, genomic DNA is packaged with histone proteins and condensed into chromatin. To gain access to the DNA, chromatin remodelling is required that is enhanced through histone post-translational modifications, which subsequently stimulate processes including DNA repair and transcription. Histone acetylation is one of the most well understood modifications and is controlled by histone acetyltransferases (HATs) and histone deacetylases (HDACs). These enzymes play critical roles in normal cellular functioning, and the dysregulation of HDAC expression in particular has been linked with the development of a number of different cancer types. Conversely, tumour cell killing following radiotherapy is triggered through DNA damage and HDACs can help co-ordinate the cellular DNA damage response which promotes radioresistance. Consequently, HDAC inhibitors have been investigated as potential radiosensitizers in vitro and in vivo to improve the efficacy or radiotherapy in specific tumour types. In this review, we provide an up-to-date summary of HDACs and their cellular functions, including in DNA damage repair. We also review evidence demonstrating that HDAC inhibitors can effectively enhance tumour radiosensitisation, and which therefore show potential for translation into the clinic for cancer patient benefit.

Histone Deacetylase Inhibitors and Papillary Thyroid Cancer

BACKGROUND/AIM

Papillary Thyroid Cancer (PTC) is the most common type of endocrine malignancy. Although PTC has an excellent prognosis, the recurrent or metastatic disease could affect patients' survival. Recent studies show that Histone Deacetylase Inhibitors (HDACIs) might be promising anticancer agents against PTC. The aim of this review is to evaluate the role of HDACIs as an additional modality in PTC treatment and to depict the latest trends of current research on this field.

MATERIALS AND METHODS

This literature review was performed using the MEDLINE database. The search strategy included terms: "thyroid cancer", "papillary", "HDAC", "histone", and "deacetylase".

RESULTS

Agents, such as Suberoyl Anilide Hydroxamic Acid, Trichostatin A, Valproic Acid, Sodium butyrate, Panobinostat, Belinostat, Romidepsin, CUDC907 and N-Hydroxy-7-(2-naphthylthio)-Hepanomide have shown promising anti-cancer effects on PTC cell lines but fail to trigger a major response in clinical trials.

CONCLUSION

HDACIs have no significant effect as monotherapy against PTC, but further research needs to be conducted in order to investigate their potential effect when used as an additional modality.

Review: Effect of Gut Microbiota and Its Metabolite SCFAs on Radiation-Induced Intestinal Injury

Gut microbiota is regarded as the second human genome and forgotten organ, which is symbiotic with the human host and cannot live and exist alone. The gut microbiota performs multiple physiological functions and plays a pivotal role in host health and intestinal homeostasis. However, the gut microbiota can always be affected by various factors and among them, it is radiotherapy that results in gut microbiota ¹²dysbiosis and it is often embodied in a decrease in the abundance and diversity of gut microbiota, an increase in harmful bacteria and a decrease in beneficial bacteria, thereby affecting many disease states, especially intestine diseases. Furthermore, gut microbiota can produce a variety of metabolites, among which short-chain fatty acids (SCFAs) are one of the most abundant and important metabolites. More importantly, SCFAs can be identified as second messengers to promote signal transduction and affect the occurrence and development of diseases. Radiotherapy can lead to the alterations of SCFAs-producing bacteria and cause changes in SCFAs, which is associated with a variety of diseases such as radiation-induced intestinal injury. However, the specific mechanism of its occurrence is not yet clear. Therefore, this review intends to emphasize the alterations of gut microbiota after radiotherapy and highlight the alterations of SCFAs-producing bacteria and SCFAs to explore the mechanisms of radiation-induced intestinal injury from the perspective of gut microbiota and its metabolite SCFAs.

Synergic radiosensitization of sinomenine hydrochloride and radioiodine on human papillary thyroid carcinoma cells

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This is the first time to study and find out that sinomenine hydrochloride and iodine-131 synergic enhance the apoptosis and regulate DNA repair and cell cycle checkpoint on papillary thyroid carcinoma cells.

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This is the first time to study and find out that sinomenine hydrochloride increased the radiosensitivity of papillary thyroid carcinoma cells and normal thyroid cells.

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This is the first time to study and find out that sinomenine hydrochloride could be a potential therapeutic radiosensitizer in papillary thyroid carcinoma radiotherapy after total thyroidectomy .

Radioiodine (¹³¹I) therapy is an important treatment for thyroid carcinoma. The response to radiotherapy sometimes limited by the development of radioresistance. Sinomenine hydrochloride(SH), was reported as a prospective radiosensitizer. This study was aim to evaluate synergic radiosensitization of SH and ¹³¹I on papillary thyroid carcinoma (PTC). We evaluated HTori-3, BCPAP and TPC-1 cells, the cell viability was evaluated by MTT. The experiment was divided into 4 groups: control group, SH (0.8 mM) group, I (¹³¹I 14.8 MBq/ml) group and ISH (SH 0.8 mM plus ¹³¹I 14.8 MBq/ml) group. Flow cytometry was used to investigate cell cycle phases and cell apoptosis. RT-PCR and western blotting were performed to determine the molecular changes. Compared to control group, SH significantly increased apoptosis and enhanced radiosensitivity of HTori-3 and PTC cells were related to the ratio of Bcl-2 to Bax protein downregulation and Fas, p21, p-ATM, p-Chk1, p-Chk2 and p53 protein expression upregulation in the ISH group (P < 0.05). Our results indicate that synergic radiosensitization of SH and iodine-131 on PTC cells and SH could be a potential therapeutic radiosensitizer in PTC radio therapy after total thyroidectomy.

Managing radioiodine refractory thyroid cancer: the role of dosimetry and redifferentiation on subsequent I-131 therapy

Poor responses to iodine-131 (I-131) therapy can relate to either low iodine uptake and retention in thyroid cancer cells or to increased radioresistance. Both mechanisms are currently termed radioactive iodine (RAI)-refractory (RAI-R) thyroid cancer but the first reflects unsuitability for I-131 therapy that can be evaluated in advance of treatment, whereas the other can only be identified post hoc. Management of both represents a considerable challenge in clinical practice as failure of I-131 therapy, the most effective treatment of metastatic thyroid cancer, is associated with a poor overall prognosis. The development of targeted therapies has shown substantial promise in the treatment of RAI-R thyroid cancer in progressive patients. Recent studies show that selective tyrosine kinase inhibitors (TKIs) targeting B-type rapidly accelerated fibrosarcoma kinase (BRAF) and mitogen-activated protein kinase (MEK) can be used as redifferentiation agents to re-induce RAI uptake, thereby (re)enabling I-131 therapy. The use of dosimetry prior- and post-TKI treatment can assist in quantifying RAI uptake and improve identification of patients that will benefit from I-131 therapy. It also potentially offers the prospect of calculating individualized therapeutic administered activities to enhance efficacy and limit toxicity. In this review, we present an overview of the regulation of RAI uptake and clinically investigated redifferentiation agents, both reimbursed and in experimental setting, that induce renewed RAI uptake. We describe the role of dosimetry in redifferentiation and subsequent I-131 therapy in RAI-R thyroid cancer, explain different dosimetry approaches and discuss limitations and considerations in the field.

Suberoylanilide hydroxamic acid enhances the radiosensitivity of lung cancer cells through acetylated wild-type and mutant p53-dependent modulation of mitochondrial apoptosis

Objective

Suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, has shown potential as a candidate radiosensitizer for many types of cancers. This study aimed to explore the radiosensitization mechanism of SAHA in lung cancer cells.

Methods

Mutations in p53 were generated by site-directed mutagenesis using polymerase chain reaction. Transfection was performed to generate H1299 cells carrying wild-type or mutant p53. The radiosensitizing enhancement ratio was determined by clonogenic assays. Mitochondrial apoptosis was detected using JC-1 staining and flow cytometry analysis.

Results

Our results showed that SAHA induced radiosensitization in H1299 cells expressing wild-type p53, p53^R175H or p53^P223L, but this enhanced clonogenic cell death was not observed in parental H1299 (p53-null) cells or H1299 cells expressing p53 with K120R, A161T and V274R mutations. In SAHA-sensitized cells, mitochondrial apoptosis was induced following exposure to irradiation. Additionally, we observed that a secondary mutation at K120 (K120R) could eliminate p53-mediated radiosensitization and mitochondrial apoptosis.

Conclusions

The results of this study suggest that wild-type and specific mutant forms of p53 mediate SAHA-induced radiosensitization by regulating mitochondrial apoptosis, and the stabilization of K120 acetylation by SAHA is the molecular basis contributing to radiosensitization in lung cancer cells.

FK228 sensitizes radioresistant small cell lung cancer cells to radiation

Background

Concurrent thoracic radiation plus chemotherapy is the mainstay of first-line treatment for limited-stage small cell lung cancer (LS-SCLC). Despite initial high responsiveness to combined chemo- and radiotherapy, SCLC almost invariably relapses and develops resistance within one year, leading to poor prognosis in patients with LS-SCLC. Developing new chemical agents that increase ionizing radiation’s cytotoxicity against SCLC is urgently needed.

Results

Dual histone deacetylase (HDAC) and PI3K inhibitor FK228 not only displayed potent anticancer activity, but also enhanced the therapeutic effects of radiotherapy in SCLC cells. Mechanistically, radioresistant SCLC cells exhibit a lower level of histone H3K9 acetylation and a higher expression level of the MRE11-RAD50-NBS1 (MRN) complex and show more efficient and redundant DNA damage repair capacities than radiosensitive SCLC cells. FK228 pretreatment resulted in marked induction of H3k9 acetylation, attenuated homologous recombination (HR) repair competency and impaired non-homologous end joining (NHEJ) repair efficacy, leading to the accumulation of radiation-induced DNA damage and radiosensitization.

Conclusion

The study uncovered that FK228 sensitized human radioresistant SCLC cells to radiation mainly through induction of chromatin decondensation and suppression of DNA damage signaling and repair. Our study provides a rational basis for a further clinical study to test the potential of FK228 as a radiosensitizing agent to increase the radiation-induced tumor cell kill in LS-SCLC patients.

The intervention of valproic acid on the tumorigenesis induced by an environmental carcinogen of PAHs

This study investigated whether valproic acid (VPA, a histone deacetylase inhibitor) can interfere with the carcinogenicity of polycyclic aromatic hydrocarbons (PAHs). A typical representative compound of PAHs, 7,12-Dimethylbenz[a]anthracene (DMBA), was used to induce rat breast cancer. The results showed that therapeutic concentration of VPA (50 and 100 mg/kg) delayed the occurrence of tumors, reduced tumor formation rate and attenuated tumors growth, and have a protective effect on normal tissues. The macrophage-mediated inflammatory response was found to be associated with the observed effect of VPA. In addition, we screened and validated a possible gene, Sema3c, which was involved in DMBA-induced breast cancer development and can be inhibited by VPA.

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.

Experimental studies of boron neutron capture therapy (BNCT) using histone deacetylase inhibitor (HDACI) sodium butyrate, as a complementary drug for the treatment of poorly differentiated thyroid cancer (PDTC)

PURPOSE

The present study analyzed different protocols of administration of boronophenylalanine (BPA) and sodium butyrate (NaB) to increase the BNCT efficacy for poorly differentiated thyroid cancer (PDTC).

MATERIALS AND METHODS

Nude mice implanted with human PDTC cells (WRO) were distributed into four protocols: 1) BPA; 2) BPA + ip NaB; 3) BPA + oral NaB; 4) Control. Biodistribution and histologic studies were performed. LAT (BPA transporter) isoforms gene expression was assessed by RT-PCR.

RESULTS

Tumor growth delay was observed in animals of the Protocol #3 (p < 0.05). NaB (Protocol #2) increased tumor boron uptake 2-h post BPA injection (p < 0.05). On the other hand, NaB upregulated the expression of all the isoforms of the LAT transporter in vitro. Histologic studies showed a significant decrease of mitotic activity and an increase of vacuoles in tumors of Protocol #3. Neutrons alone or combined with NaB caused some tumor growth delay (p < 0.05), while in the BNCT and BNCT + NaB groups, there was a halt in tumor growth in 70 and 80% of the animals, respectively.

CONCLUSIONS

Intraperitoneally administration of NaB increased boron uptake while oral administration for a longer period of time induced tumor growth delay previous to BPA administration. The use of NaB via ip would optimize the irradiation results.

Correction for hyperfunctioning radiation-induced stunning (CHRIS) in benign thyroid diseases

PURPOSE

Radioiodine-131 treatment has been a well-established therapy for benign thyroid diseases for more than 75 years. However, the physiological reasons of the so-called stunning phenomenon, defined as a reduced radioiodine uptake after previous diagnostic radioiodine administration, are still discussed controversially. In a recent study, a significant dependence of thyroid stunning on the pre-therapeutically administered radiation dose could be demonstrated in patients with goiter and multifocal autonomous nodules. A release of thyroid hormones to the blood due to radiation-induced destruction of thyroid follicles leading to a temporarily reduced cell metabolism was postulated as possible reason for this indication-specific stunning effect. Therefore, the aim of this study was to develop dose-dependent correction factors to account for stunning and thereby improve precision of radioiodine treatment in these indications.

METHODS

A retrospective analysis of 313 patients (135 with goiter and 178 with multifocal autonomous nodules), who underwent radioiodine uptake testing and radioiodine treatment, was performed. The previously determined indication-specific values for stunning of 8.2% per Gray in patients with multifocal autonomous nodules and 21% per Gray in patients with goiter were used to modify the Marinelli equation by the calculation of correction factors for hyperfunctioning radiation-induced stunning (CHRIS). Subsequently, the calculation of the required activity of radioiodine-131 to obtain an intra-therapeutic target dose of 150 Gy was re-evaluated in all patients. Furthermore, a calculation of the hypothetically received target dose by using the CHRIS-calculated values was performed and compared with the received target doses.

RESULTS

After integrating the previously obtained results for stunning, CHRIS-modified Marinelli equations could be developed for goiter and multifocal autonomous nodules. For patients with goiter, the mean value of administered doses calculated with CHRIS was 149 Gy and did not differ from the calculation with the conventional Marinelli equation of 152 Gy with statistical significance (p = 0.60). However, the statistical comparison revealed a highly significant improvement (p < 0.000001) of the fluctuation range of the results received with CHRIS. Similar results were obtained in the subgroup of patients with multifocal autonomous nodules. The mean value of the administered dose calculated with the conventional Marinelli equation was 131 Gy and therefore significantly below the CHRIS-calculated radiation dose of 150 Gy (p < 0.05). Again, the fluctuation range of the CHRIS-calculated radiation dose in the target volume was significantly improved compared with the conventional Marinelli equation (p < 0.000001).

CONCLUSIONS

With the presented CHRIS equation it is possible to calculate a required individual stunning-independent radioiodine activity for the first time by only using data from the radioiodine uptake testing. The results of this study deepen our understanding of thyroid stunning in benign thyroid diseases and improve precision of dosimetry in radioiodine-131 therapy of goiter and multifocal autonomous nodules.

Effective treatment of drug-resistant lung cancer via a nanogel capable of reactivating cisplatin and enhancing early apoptosis

Cisplatin resistance is a daunting obstacle in cancer therapy and one of the major causes for treatment failure due to the inadequate drug activity and apoptosis induction. To overcome cisplatin resistance, we proposed a multifunctional nanogel (designated as Valproate-D-Nanogel) capable of reactivating cisplatin and enhancing early apoptosis. This Valproate-D-Nanogel was prepared through copolymerizing carboxymethyl chitosan with diallyl disulfide and subsequent grafting with valproate to reverse the drug-resistance in cisplatin-resistant human lung adenocarcinoma cancer. It can significantly increase the proportion of G2/M phase (up to 3.2-fold enhancement) to reactivate cisplatin via high level of G2/M arrest induced by valproate. Meanwhile, the intracellular ROS-P53 crosstalk can be upregulated by diallyl disulfide (up to 8-fold increase of ROS) and valproate (up to 18-fold increase of P53) to enhance early apoptosis. The synchronization of enhanced G2/M arrest and ROS-P53 crosstalk devotes to reverse the cisplatin resistance with a high level of resistance reversion index (50.22). As a result, improved in vivo tumor inhibition (up to 15-fold higher compared to free cisplatin) and decreased systemic toxicity was observed after treatment with Valproate-D-Nanogels. Overall, this nanogel can effectively inhibit cisplatin-resistance cancer through combined pathways and provides an effective approach for overcoming cisplatin-resistance in cancer treatment.

Epigenetic Drugs for Cancer and microRNAs: A Focus on Histone Deacetylase Inhibitors

Over recent decades, it has become clear that epigenetic abnormalities are involved in the hallmarks of cancer. Histone modifications, such as acetylation, play a crucial role in cancer development and progression, by regulating gene expression, such as for oncogenes or tumor suppressor genes. Therefore, histone deacetylase inhibitors (HDACi) have recently shown efficacy against both hematological and solid cancers. Designed to target histone deacetylases (HDAC), these drugs can modify the expression pattern of numerous genes including those coding for micro-RNAs (miRNA). miRNAs are small non-coding RNAs that regulate gene expression by targeting messenger RNA. Current research has found that miRNAs from a tumor can be investigated in the tumor itself, as well as in patient body fluids. In this review, we summarized current knowledge about HDAC and HDACi in several cancers, and described their impact on miRNA expression. We discuss briefly how circulating miRNAs may be used as biomarkers of HDACi response and used to investigate response to treatment.