Radiosensitizing effects of arsenic trioxide on MCF-7 human breast cancer cells exposed to 89strontium chloride

Application of nanomedicine in radiotherapy sensitization

Radiation therapy is an important component of cancer treatment. As research in radiotherapy techniques advances, new methods to enhance tumor response to radiation need to be on the agenda to enable enhanced radiation therapy at low radiation doses. With the rapid development of nanotechnology and nanomedicine, the use of nanomaterials as radiosensitizers to enhance radiation response and overcome radiation resistance has attracted great interest. The rapid development and application of emerging nanomaterials in the biomedical field offers good opportunities to improve the efficacy of radiotherapy, which helps to promote the development of radiation therapy and will be applied in clinical practice in the near future. In this paper, we discuss the main types of nano-radiosensitizers and explore their sensitization mechanisms at the tissue level, cellular level and even molecular biology and genetic level, and analyze the current status of promising nano-radiosensitizers and provide an outlook on their future development and applications.

Targeting GLI1 Transcription Factor for Restoring Iodine Avidity with Redifferentiation in Radioactive-Iodine Refractory Thyroid Cancers

Simple Summary

Thyroid cancers have an excellent prognosis by standard therapy of surgery followed by radioactive-iodine therapy. However, metastatic thyroid cancers do not response to radioactive-iodine therapy by losing iodine avidity. Therefore, reversing iodine avidity to metastatic thyroid cancers gives a new chance of applying radioactive-iodine therapy to the cancers. In the current study, we found that GLI1 knockdown can revert iodine non-avid thyroid cancers to iodine avid cancers by increasing expression of thyroid-specific proteins. Restoration of iodine avidity in thyroid cancers makes the cancers sensitive to radioactive-iodine therapy again. Therefore, the GLI1 can be a potential therapeutic target of radioactive-iodine resistant thyroid cancers.

Abstract

Radioactive-iodine (RAI) therapy is the mainstay for patients with recurrent and metastatic thyroid cancer. However, many patients exhibit dedifferentiation characteristics along with lack of sodium iodide symporter (NIS) functionality, low expression of thyroid-specific proteins, and poor RAI uptake, leading to poor prognosis. Previous studies have demonstrated the effect of GLI family zinc finger 1 (GLI1) inhibition on tumor growth and apoptosis. In this study, we investigated the role of GLI1 in the context of redifferentiation and improvement in the efficacy of RAI therapy for thyroid cancer. We evaluated GLI1 expression in several thyroid cancer cell lines and selected TPC-1 and SW1736 cell lines showing the high expression of GLI. We performed GLI1 knockdown and evaluated the changes of thyroid-specific proteins expression, RAI uptake and I-131-mediated cytotoxicity. The effect of GANT61 (GLI1 inhibitor) on endogenous NIS expression was also assessed. Endogenous NIS expression upregulated by inhibiting GLI1, in addition, increased expression level in plasma membrane. Also, GLI1 knockdown increased expression of thyroid-specific proteins. Restoration of thyroid-specific proteins increased RAI uptake and I-131-mediated cytotoxic effect. Treatment with GANT61 also increased expression of endogenous NIS. Targeting GLI1 can be a potential strategy with redifferentiation for restoring RAI avidity in dedifferentiated thyroid cancers.

Synergistic Effects of Arsenic Trioxide and Radiation: Triggering the Intrinsic Pathway of Apoptosis

Background

Arsenic trioxide (ATO) has been reported as an effective anti-cancer and a US Food and Drug Administration (FDA) approved drug for treatment of some cancers. The aim of this study was to determine the underlying apoptosis molecular and cellular mechanisms of ATO in the presence or absence of ionizing radiation (IR) in vitro in the glioblastoma multiforme (GBM) cell line, U87MG.

Methods

Cells were treated by different concentrations of ATO either in presence or absence of IR. Viability and apoptosis pathway of both treated and control groups were evaluated using MTT assay and the expression analysis of Bax, Bcl-2, and caspase-3 genes, respectively. All treatments were performed on 100-μm diameter spheroids.

Results

Results showed a significant reduction in the survival of the cells in all treated groups. As expected, cell survival was much less in combination treatment than treatment with only ATO. Moreover, combination therapy made Bax and caspase-3 up-regulated and Bcl-2 down-regulated.

Conclusion

ATO and radiation had a synergistic apoptotic effect on GBM cells by up-regulation of caspase-3 and alteration of the Bax-Bcl-2 balance; therefore, ATO may act as a potential anti-cancer agent against GBM cells through triggering the mitochondrial pathway of apoptosis.

Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells

Arsenic trioxide (As₂O₃) has been used clinically as an anti-tumor agent. Its mechanisms are mostly considered to be the induction of apoptosis and cell cycle arrest. However, the detailed molecular mechanisms of its anti-cancer action through cell cycle arrest are poorly known. Furthermore, As₂O₃ has been shown to be a potential DNA methylation inhibitor, inducing DNA hypomethylation. We hypothesize that As₂O₃ may affect the expression of cell cycle regulatory genes by interfering with DNA methylation patterns. To explore this, we examined promoter methylation status of 24 cell cycle genes in breast cancer cell lines and in a normal breast tissue sample by methylation-specific polymerase chain reaction and/or restriction enzyme-based methods. Gene expression level and cell cycle distribution were quantified by real-time polymerase chain reaction and flow cytometric analyses, respectively. Our methylation analysis indicates that only promoters of RBL1 (p107), RASSF1A, and cyclin D2 were aberrantly methylated in studied breast cancer cell lines. As₂O₃ induced CpG island demethylation in promoter regions of these genes and restores their expression correlated with DNA methyltransferase inhibition. As₂O₃ also induced alterations in messenger RNA expression of several cell cycle-related genes independent of demethylation. Flow cytometric analysis revealed that the cell cycle arrest induced by As₂O₃ varied depending on cell lines, MCF-7 at G1 phase and both MDA-MB-231 and MDA-MB-468 cells at G2/M phase. These changes at transcriptional level of the cell cycle genes by the molecular mechanisms dependent and independent of demethylation are likely to represent the mechanisms of cell cycle redistribution in breast cancer cells, in response to As₂O₃ treatment.

Arsenic Trioxide as a Radiation Sensitizer for 131I-Metaiodobenzylguanidine Therapy: Results of a Phase II Study

Arsenic trioxide has in vitro and in vivo radiosensitizing properties. We hypothesized that arsenic trioxide would enhance the efficacy of the targeted radiotherapeutic agent (131)I-metaiodobenzylguanidine ((131)I-MIBG) and tested the combination in a phase II clinical trial.

METHODS

Patients with recurrent or refractory stage 4 neuroblastoma or metastatic paraganglioma/pheochromocytoma (MP) were treated using an institutional review board-approved protocol (Clinicaltrials.gov identifier NCT00107289). The planned treatment was (131)I-MIBG (444 or 666 MBq/kg) intravenously on day 1 plus arsenic trioxide (0.15 or 0.25 mg/m(2)) intravenously on days 6-10 and 13-17. Toxicity was evaluated using National Cancer Institute Common Toxicity Criteria, version 3.0. Response was assessed by International Neuroblastoma Response Criteria or (for MP) by changes in (123)I-MIBG or PET scans.

RESULTS

Twenty-one patients were treated: 19 with neuroblastoma and 2 with MP. Fourteen patients received (131)I-MIBG and arsenic trioxide, both at maximal dosages; 2 patients received a 444 MBq/kg dose of (131)I-MIBG plus a 0.15 mg/kg dose of arsenic trioxide; and 3 patients received a 666 MBq/kg dose of (131)I-MIBG plus a 0.15 mg/kg dose of arsenic trioxide. One did not receive arsenic trioxide because of transient central line-induced cardiac arrhythmia, and another received only 6 of 10 planned doses of arsenic trioxide because of grade 3 diarrhea and vomiting with concurrent grade 3 hypokalemia and hyponatremia. Nineteen patients experienced myelosuppression higher than grade 2, most frequently thrombocytopenia (n = 18), though none required autologous stem cell rescue. Twelve of 13 evaluable patients experienced hyperamylasemia higher than grade 2 from transient sialoadenitis. By International Neuroblastoma Response Criteria, 12 neuroblastoma patients had no response and 7 had progressive disease, including 6 of 8 entering the study with progressive disease. Objective improvements in semiquantitative (131)I-MIBG scores were observed in 6 patients. No response was seen in MP. Seventeen of 19 neuroblastoma patients continued on further chemotherapy or immunotherapy. Mean 5-year overall survival (±SD) for neuroblastoma was 37% ± 11%. Mean absorbed dose of (131)I-MIBG to blood was 0.134 cGy/MBq, well below myeloablative levels in all patients.

CONCLUSION

(131)I-MIBG plus arsenic trioxide was well tolerated, with an adverse event profile similar to that of (131)I-MIBG therapy alone. The addition of arsenic trioxide to (131)I-MIBG did not significantly improve response rates when compared with historical data with (131)I-MIBG alone.