HDAC inhibitors reverse acquired radio resistance of KYSE-150R esophageal carcinoma cells by modulating Bmi-1 expression

MAGI1 Prevents Senescence and Promotes the DNA Damage Response in ER+ Breast Cancer

MAGI1 acts as a tumor suppressor in estrogen receptor-positive (ER+) breast cancer (BC), and its loss correlates with a more aggressive phenotype. To identify the pathways and events affected by MAGI1 loss, we deleted the MAGI1 gene in the ER+ MCF7 BC cell line and performed RNA sequencing and functional experiments in vitro. Transcriptome analyses revealed gene sets and biological processes related to estrogen signaling, the cell cycle, and DNA damage responses affected by MAGI1 loss. Upon exposure to TNF-α/IFN-γ, MCF7 MAGI1 KO cells entered a deeper level of quiescence/senescence compared with MCF7 control cells and activated the AKT and MAPK signaling pathways. MCF7 MAGI1 KO cells exposed to ionizing radiations or cisplatin had reduced expression of DNA repair proteins and showed increased sensitivity towards PARP1 inhibition using olaparib. Treatment with PI3K and AKT inhibitors (alpelisib and MK-2206) restored the expression of DNA repair proteins and sensitized cells to fulvestrant. An analysis of human BC patients' transcriptomic data revealed that patients with low MAGI1 levels had a higher tumor mutational burden and homologous recombination deficiency. Moreover, MAGI1 expression levels negatively correlated with PI3K/AKT and MAPK signaling, which confirmed our in vitro observations. Pharmacological and genomic evidence indicate HDACs as regulators of MAGI1 expression. Our findings provide a new view on MAGI1 function in cancer and identify potential treatment options to improve the management of ER+ BC patients with low MAGI1 levels.

Promotion of microRNA-146a by histone deacetylase 4 silencing contributes to radiosensitization of esophageal carcinoma

Background

Histone deacetylases (HDACs) have been identified to be implicated in the carcinogenesis and cancer progression. The present study was performed to probe into the effect of HDAC4 on radioresistance of esophageal carcinoma (EC).

Methods

The expression of HDAC4 in responders and non-responders to radiotherapy was characterized by RT-qPCR, immunohistochemistry, and Western blot analysis. EC cells were exposed to continuous fractionated X-ray irradiation, and their proliferation and apoptosis were evaluated by means of colony formation assay and flow cytometry based Annexin V-FITC/PI apoptosis assay in response to HDAC4 overexpression or silencing. Mechanistic investigation was conducted by means of in silico analysis and dual-luciferase reporter gene assay. Tumor xenografts derived from radioresistant EC cells were exposed to local X-ray irradiation in vivo for validation.

Results

High expression of HDAC4 was detected in either tumor tissues derived from radiotherapy responders or radioresistant EC cells. Loss of HDAC4 contributed to suppressed proliferation and enhanced apoptosis of radioresistant EC cells. Moreover, our findings revealed that HDAC4 conferred radioresistance of EC by downregulating microRNA-146a (miR-146a). Interleukin-1 receptor-associated kinase 1 (IRAK1) was a target of miR-146a, and its knockdown promoted radiosensitivity. Silencing of HDAC4 radiosensitized EC cells both in vitro and in vivo via the miR-146a/IRAK1 axis.

Conclusion

Hence, loss of HDAC4 upregulated miR-146a to limit radioresistance. This study aids in the better understanding about mechanism responsible for radioresistance of EC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03171-z.

Biological Adaptations of Tumor Cells to Radiation Therapy

Radiation therapy has been used worldwide for many decades as a therapeutic regimen for the treatment of different types of cancer. Just over 50% of cancer patients are treated with radiotherapy alone or with other types of antitumor therapy. Radiation can induce different types of cell damage: directly, it can induce DNA single- and double-strand breaks; indirectly, it can induce the formation of free radicals, which can interact with different components of cells, including the genome, promoting structural alterations. During treatment, radiosensitive tumor cells decrease their rate of cell proliferation through cell cycle arrest stimulated by DNA damage. Then, DNA repair mechanisms are turned on to alleviate the damage, but cell death mechanisms are activated if damage persists and cannot be repaired. Interestingly, some cells can evade apoptosis because genome damage triggers the cellular overactivation of some DNA repair pathways. Additionally, some surviving cells exposed to radiation may have alterations in the expression of tumor suppressor genes and oncogenes, enhancing different hallmarks of cancer, such as migration, invasion, and metastasis. The activation of these genetic pathways and other epigenetic and structural cellular changes in the irradiated cells and extracellular factors, such as the tumor microenvironment, is crucial in developing tumor radioresistance. The tumor microenvironment is largely responsible for the poor efficacy of antitumor therapy, tumor relapse, and poor prognosis observed in some patients. In this review, we describe strategies that tumor cells use to respond to radiation stress, adapt, and proliferate after radiotherapy, promoting the appearance of tumor radioresistance. Also, we discuss the clinical impact of radioresistance in patient outcomes. Knowledge of such cellular strategies could help the development of new clinical interventions, increasing the radiosensitization of tumor cells, improving the effectiveness of these therapies, and increasing the survival of patients.

The mechanisms and reversal strategies of tumor radioresistance in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of most lethal malignancies with high aggressive potential in the world. Radiotherapy is used as one curative treatment modality for ESCC patients. Due to radioresistance, the 5-year survival rates of patients after radiotherapy is less than 20%. Tumor radioresistance is very complex and heterogeneous. Cancer-associated fibroblasts (CAFs), as one major component of tumor microenvironment (TME), play critical roles in regulating tumor radioresponse through multiple mechanisms and are increasingly considered as important anti-cancer targets. Cancer stemness, which renders cancer cells to be extremely resistant to conventional therapies, is involved in ESCC radioresistance due to the activation of Wnt/β-catenin, Notch, Hedgehog and Hippo (HH) pathways, or the induction of epithelial-mesenchymal transition (EMT), hypoxia and autophagy. Non-protein-coding RNAs (ncRNAs), which account for more than 90% of the genome, are involved in esophageal cancer initiation and progression through regulating the activation or inactivation of downstream signaling pathways and the expressions of target genes. Herein, we mainly reviewed the role of CAFs, cancer stemness, non-coding RNAs as well as others in the development of radioresistance and clarify the involved mechanisms. Furthermore, we summarized the potential strategies which were reported to reverse radioresistance in ESCC. Together, this review gives a systematic coverage of radioresistance mechanisms and reversal strategies and contributes to better understanding of tumor radioresistance for the exploitation of novel intervention strategies in ESCC.

Targeting cancer-cell mitochondria and metabolism to improve radiotherapy response

Radiotherapy is a regimen that uses ionising radiation (IR) to treat cancer. Despite the availability of several therapeutic options, cancer remains difficult to treat and only a minor percentage of patients receiving radiotherapy show a complete response to the treatment due to development of resistance to IR (radioresistance). Therefore, radioresistance is a major clinical problem and is defined as an adaptive response of the tumour to radiation-induced damage by altering several cellular processes which sustain tumour growth including DNA damage repair, cell cycle arrest, alterations of oncogenes and tumour suppressor genes, autophagy, tumour metabolism and altered reactive oxygen species. Cellular organelles, in particular mitochondria, are key players in mediating the radiation response in tumour, as they regulate many of the cellular processes involved in radioresistance. In this article has been reviewed the recent findings describing the cellular and molecular mechanism by which cancer rewires the function of the mitochondria and cellular metabolism to enhance radioresistance, and the role that drugs targeting cellular bioenergetics have in enhancing radiation response in cancer patients.

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.

MLLT10 rearranged acute leukemia: Incidence, prognosis, and possible therapeutic strategies

Rearrangements of the MLLT10 gene occur in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), most commonly T-lineage ALL (T-ALL), in patients of all ages. MLLT10 rearranged (MLLT10r) acute leukemia presents a complex diagnostic and therapeutic challenge due to frequent presentation of immature or mixed phenotype, and a lack of consensus regarding optimal therapy. Cases of MLLT10r AML or T-ALL bearing immature phenotype are at high risk of poor outcome, but the underlying molecular mechanisms and sensitivity to targeted therapies remain poorly characterized. This review addresses the incidence and prognostic significance of MLLT10r in acute leukemia, and how the aberrant gene expression profile of this disease can inform potential targeted therapeutic strategies. Understanding the underlying genomics of MLLT10r acute leukemia, both clinically and molecularly, will improve prognostic stratification and accelerate the development of targeted therapeutic strategies, to improve patient outcomes.

ROS-Mediated Therapeutic Strategy in Chemo-/Radiotherapy of Head and Neck Cancer

Head and neck cancer is a highly genetic and metabolic heterogeneous collection of malignancies of the lip, oral cavity, salivary glands, pharynx, esophagus, paranasal sinuses, and larynx with five-year survival rates ranging from 12% to 93%. Patients with head and neck cancer typically present with advanced stage III, IVa, or IVb disease and are treated with comprehensive modality including chemotherapy, radiotherapy, and surgery. Despite advancements in treatment modality and technique, noisome recurrence, invasiveness, and resistance as well as posttreatment complications severely influence survival rate and quality of life. Thus, new therapeutic strategies are urgently needed that offer enhanced efficacy with less toxicity. ROS in cancer cells plays a vital role in regulating cell death, DNA repair, stemness maintenance, metabolic reprogramming, and tumor microenvironment, all of which have been implicated in resistance to chemo-/radiotherapy of head and neck cancer. Adjusting ROS generation and elimination to reverse the resistance of cancer cells without impairing normal cells show great hope in improving the therapeutic efficacy of chemo-/radiotherapy of head and neck cancer. In the current review, we discuss the pivotal and targetable redox-regulating system including superoxide dismutases (SODs), tripeptide glutathione (GSH), thioredoxin (Trxs), peroxiredoxins (PRXs), nuclear factor erythroid 2-related factor 2/Kelch-like ECH-associated protein 1 (Nrf2/keap1), and mitochondria electron transporter chain (ETC) complexes and their roles in regulating ROS levels and their clinical significance implicated in chemo-/radiotherapy of head and neck cancer. We also summarize several old drugs (referred to as the non-anti-cancer drugs used in other diseases for a long time) and small molecular compounds as well as natural herbs which effectively modulate cellular ROS of head and neck cancer to synergize the efficacy of conventional chemo-/radiotherapy. Emerging interdisciplinary techniques including photodynamic, nanoparticle system, and Bio-Electro-Magnetic-Energy-Regulation (BEMER) therapy are promising measures to broaden the potency of ROS modulation for the benefit of chemo-/radiotherapy in head and neck cancer.

NVP-BSK805, an Inhibitor of JAK2 Kinase, Significantly Enhances the Radiosensitivity of Esophageal Squamous Cell Carcinoma in vitro and in vivo

Purpose

Radiotherapy is one major curative treatment modality for esophageal squamous cell carcinoma (ESCC) patients. This study aimed to find out small-molecular kinase inhibitors, which can significantly enhance the radiosensitivity of ESCC in vitro and in vivo.

Materials and Methods

Ninety-three kinase inhibitors were tested for their radiosensitizing effect in ESCC cells through high-content screening. The radiosensitizing effect of kinase inhibitors was investigated in vitro by detection of DNA double-strand breaks (DSBs) and clonogenic survival assay. By the establishment of xenograft tumor models in BALB/c nude mice, the radiosensitizing effect of kinase inhibitors was investigated in vivo.

Results

Among the 93 kinase inhibitors tested, we found NVP-BSK805, an inhibitor of JAK2 kinase, significantly radiosensitized ESCC cells through enhancing DSBs, inhibiting DNA damage repair and arresting cell cycle in G2/M or G0/G1 phase. After treatment with NVP-BSK805, ESCC cells showed decreased clonogenic survival and delayed tumor growth in vivo. JAK2 kinase was highly expressed in tumor tissues of ESCC patients, while rarely expressed in matched normal esophageal epithelial tissues. Survival analysis revealed JAK2 kinase as a prognostic factor of ESCC patients treated with chemoradiotherapy.

Conclusion

Our study discovered JAK2 kinase as an attractive target to enhance the radiosensitivity of ESCC cells in vitro and in vivo.

A review of radiation genomics: integrating patient radiation response with genomics for personalised and targeted radiation therapy

Background

The success of radiation therapy for cancer patients is dependent on the ability to deliver a total tumouricidal radiation dose capable of eradicating all cancer cells within the clinical target volume, however, the radiation dose tolerance of the surrounding healthy tissues becomes the main dose-limiting factor. The normal tissue adverse effects following radiotherapy are common and significantly impact the quality of life of patients. The likelihood of developing these adverse effects following radiotherapy cannot be predicted based only on the radiation treatment parameters. However, there is evidence to suggest that some common genetic variants are associated with radiotherapy response and the risk of developing adverse effects. Radiation genomics is a field that has evolved in recent years investigating the association between patient genomic data and the response to radiation therapy. This field aims to identify genetic markers that are linked to individual radiosensitivity with the potential to predict the risk of developing adverse effects due to radiotherapy using patient genomic information. It also aims to determine the relative radioresponse of patients using their genetic information for the potential prediction of patient radiation treatment response.

Methods and materials

This paper reports on a review of recent studies in the field of radiation genomics investigating the association between genomic data and patients response to radiation therapy, including the investigation of the role of genetic variants on an individual’s predisposition to enhanced radiotherapy radiosensitivity or radioresponse.

Conclusion

The potential for early prediction of treatment response and patient outcome is critical in cancer patients to make decisions regarding continuation, escalation, discontinuation, and/or change in treatment options to maximise patient survival while minimising adverse effects and maintaining patients’ quality of life.

Circ0043898 acts as a tumor inhibitor and performs regulatory effect on the inhibition of esophageal carcinoma

Objective: The study aimed to investigate candidate circular RNAs (circRNAs) in regulating the pathogenic process of esophageal carcinoma. Methods: Specimens were collected from the patients with esophageal carcinoma. Total RNA was purified and treated with RNase R followed by RNA-seq in the purpose of screening the circRNAs in significant differentially expression. The expression level of the screened circRNAs were further validated using RT-PCR. The circular structure of the circRNA was validated with divergent and convergent primers. Overexpression vector was prepared in the purpose of raising the expression level of circ0043898 in the ECA-109 and Kyse-520 cells. The cell colony assay and MTS assay were conducted to determine the capacity of cell proliferation. Chamber assays were applied to determine the capacity of cell migration and invasion while flowcytometry was applied to determine the cell cycle and cell apoptosis. In vivo animal assay was conducted by injecting the cells to the chest of the mice. RNA-seq was performed followed by GO and KEGG study to further verify the regulation mechanism of circ0043898. Results: circ0043898 was validated that down-regulated expressed in the specimens from the patients with esophageal carcinoma. The cell assays proved that overexpression of circ0043898 can obviously inhibit the cell proliferation, cell migration and invasion and induce cell apoptosis and death in the cancerous cells. The in vivo animal study also suggested that the circ0043898 performed inhibitory functions on oncogenesis. The RNA-seq presented the potential regulation mechanism of circ0043898. Histone H3 and BMI1 were presented significantly differential expression in both ECA-109 and Kyse-520 cells, indicating they might be the targets of circ0043898. Conclusion: circ0043898 is presented as tumor inhibitor and could be a candidate biomarker in the therapeutic target and diagnosis of esophageal carcinoma.

MicroRNA-203 Increases Cell Radiosensitivity via Directly Targeting Bmi-1 in Hepatocellular Carcinoma

BACKGROUND

B-cell-specific moloney leukemia virus insertion site 1 (Bmi-1) plays important roles in various cancers, but its regulation through microRNAs (miRNAs) and its functions in hepatocellular carcinoma (HCC) remains unclear.

METHODS

We evaluated the expression and prognostic significance of Bmi-1 in HCC by using tissue samples and The Cancer Genome Atlas (TCGA) data sets. The relationship between miRNAs and Bmi-1 was verified by bioinformatics prediction and immunofluorescence. Colony formation and apoptosis assays were used to reveal the effect of miR-203 on radiosensitivity.

RESULTS

The Bmi-1 mRNA and protein were upregulated in HCC tissues. Cox regression multivariate analyses showed that Bmi-1 overexpression was an independent prognostic parameter for HCC patients. The expression level of Bmi-1 was negatively associated with miR-203 levels in HCC tissues. Dual-luciferase reporter assays showed that miR-203 could target the 3' untranslated region (3'-UTR) of Bmi-1 directly. Overexpression of miR-203 in HepG2 and Smmc-7721 cells increases their sensitivity to ionizing radiation in vitro and in vivo. Moreover, the improved cell radiosensitivity induced by miR-203 could be rescued by restoration of Bmi-1 expression.

CONCLUSIONS

Bmi-1 could improve the predictive accuracy for HCC patients' survival. Moreover, miR-203 enhance cell radiosensitivity in vitro and in vivo by targeting Bmi-1 in HCC.

Role of metabolism in cancer cell radioresistance and radiosensitization methods

BACKGROUND

Radioresistance is a major factor leading to the failure of radiotherapy and poor prognosis in tumor patients. Following the application of radiotherapy, the activity of various metabolic pathways considerably changes, which may result in the development of resistance to radiation.

MAIN BODY

Here, we discussed the relationships between radioresistance and mitochondrial and glucose metabolic pathways, aiming to elucidate the interplay between the tumor cell metabolism and radiotherapy resistance. In this review, we additionally summarized the potential therapeutic targets in the metabolic pathways.

SHORT CONCLUSION

The aim of this review was to provide a theoretical basis and relevant references, which may lead to the improvement of the sensitivity of radiotherapy and prolong the survival of cancer patients.

CAF-secreted CXCL1 conferred radioresistance by regulating DNA damage response in a ROS-dependent manner in esophageal squamous cell carcinoma

Five-year survival rate of esophageal squamous cell carcinoma (ESCC) patients treated with radiotherapy is <20%. Our study aimed to investigate whether cancer-associated fibroblasts (CAFs), one major component of tumor microenvironment, were involved in tumor radioresistance in ESCC. By use of human chemokine/cytokine array, human chemokine CXCL1 was found to be highly expressed in CAFs compared with that in matched normal fibroblasts. Inhibition of CXCL1 expression in CAFs significantly reversed CAF-conferred radioresistance in vitro and in vivo. CAF-secreted CXCL1 inhibited the expression of reactive oxygen species (ROS)-scavenging enzyme superoxide dismutase 1, leading to increased ROS accumulation following radiation, by which DNA damage repair was enhanced and the radioresistance was mediated. CAF-secreted CXCL1 mediated the radioresistance also by activation of Mek/Erk pathway. The cross talk of CAFs and ESCC cells induced CXCL1 expression in an autocrine/paracrine signaling loop, which further enhanced tumor radioresistance. Together, our study highlighted CAF-secreted CXCL1 as an attractive target to reverse tumor radioresistance and can be used as an independent prognostic factor of ESCC patients treated with chemoradiotherapy.

Drug priming enhances radiosensitivity of adamantinomatous craniopharyngioma via downregulation of survivin

OBJECTIVE In this study, the authors investigated the underlying mechanisms responsible for high tumor recurrence rates of adamantinomatous craniopharyngioma (ACP) after radiotherapy and developed new targeted treatment protocols to minimize recurrence. ACPs are characterized by the activation of the receptor tyrosine kinase epidermal growth factor receptor (EGFR), known to mediate radioresistance in various tumor entities. The impact of tyrosine kinase inhibitors (TKIs) gefitinib or CUDC-101 on radiation-induced cell death and associated regulation of survivin gene expression was evaluated. METHODS The hypothesis that activated EGFR promotes radioresistance in ACP was investigated in vitro using human primary cell cultures of ACP (n = 10). The effects of radiation (12 Gy) and combined radiochemotherapy on radiosensitivity were assessed via cell death analysis using flow cytometry. Changes in target gene expression were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Survivin, identified in qRT-PCR to be involved in radioresistance of ACP, was manipulated by small interfering RNA (siRNA), followed by proliferation and vitality assays to further clarify its role in ACP biology. Immunohistochemically, survivin expression was assessed in patient tumors used for primary cell cultures. RESULTS In primary human ACP cultures, activation of EGFR resulted in significantly reduced cell death levels after radiotherapy. Treatment with TKIs alone and in combination with radiotherapy increased cell death response remarkably, assessed by flow cytometry. CUDC-101 was significantly more effective than gefitinib. The authors identified regulation of survivin expression after therapeutic intervention as the underlying molecular mechanism of radioresistance in ACP. EGFR activation promoting ACP cell survival and proliferation in vitro is consistent with enhanced survivin gene expression shown by qRT-PCR. TKI treatment, as well as the combination with radiotherapy, reduced survivin levels in vitro. Accordingly, ACP showed reduced cell viability and proliferation after survivin downregulation by siRNA. CONCLUSIONS These results indicate an impact of EGFR signaling on radioresistance in ACP. Inhibition of EGFR activity by means of TKI treatment acts as a radiosensitizer on ACP tumor cells, leading to increased cell death. Additionally, the results emphasize the antiapoptotic and pro-proliferative role of survivin in ACP biology and its regulation by EGFR signaling. The suppression of survivin by treatment with TKI and combined radiotherapy represents a new promising treatment strategy that will be further assessed in in vivo models of ACP.

Silencing BMI1 radiosensitizes human breast cancer cells by inducing DNA damage and autophagy

Overexpression of BMI1 in human cancer cells, a member of the polycomb group of repressive complexes, correlates with advanced stage of disease, aggressive clinico-pathological behavior, poor prognosis, and resistance to radiation and chemotherapy. Studies have shown that experimental reduction of BMI1 protein level in tumor cells results in inhibition of cell proliferation, induction of apoptosis and/or senescence, and increased susceptibility to cytotoxic agents and radiation therapy. Although a role for BMI1 in cancer progression and its importance as a molecular target for cancer therapy has been established, information on the impact of silencing BMI1 in triple-negative breast cancer (TNBC) and its consequence on radiotherapy have not been well studied. Therefore, in the present study we investigated the potential therapeutic benefit of radiation therapy in BMI1-silenced breast cancer cells and studied the mechanism(s) of radiosensitization. Human MDA-MB-231 and SUM159PT breast cancer cells that were either stably transfected with a lentiviral vector expressing BMI1 shRNA (shBMI1) or control shRNA (shControl) or transient transfection with a BMI1-specific siRNA were used. Silencing of BMI1 resulted in marked reduction in BMI1 both at the mRNA and protein level that was accompanied by a significant reduction in cell migration compared to control cells. Further, BMI1 knockdown produced a marked enhancement of DNA damage as evidenced by Comet Assay and γH2AX foci, resulting in a dose-dependent radiosensitization effect. Molecular studies revealed modulation of protein expression that is associated with the DNA damage response (DDR) and autophagy pathways. Our results demonstrate that BMI1 is an important therapeutic target in breast cancer and suppression of BMI1 produces radiation sensitivity. Further, combining BMI1-targeted therapeutics with radiation might benefit patients diagnosed with TNBC.

Potential anti-genotoxic effect of sodium butyrate to modulate induction of DNA damage by tamoxifen citrate in rat bone marrow cells

Sodium butyrate (SB) is one of the histone deacetylase inhibitors (HDACi's) that is recently evidenced to have a prooxidant activity and an ability to reduce hydrogen peroxide-induced DNA damage. Since the majority of estrogen receptor positive breast cancer patients are treated with tamoxifen citrate (TC), which exerts well established oxidative and genotoxic effects, thus the basic objective of this study is to determine whether SB could ameliorate or curate tamoxifen citrate-induced oxidative DNA damage and genotoxic effect in vivo through up-regulation of some antioxidant enzymes. The individual and combined effects of SB and TC have been examined on rat bone marrow cells, using Micronucleus assays (MN), Comet assay, DNA fragmentation, expression of some antioxidant genes using Real time-PCR and finally, oxidative stress analysis. SB significantly increased the mitotic activity (P < 0.05), while TC induced marked micronuclei and oxidative DNA damage, in the SB post-treatment group, the combination of SB (300 mg/kg) and TC (40 mg/kg) was able to decrease the induction of MN and oxidative DNA damage through up-regulation of Cat, Sod and Gpx1 genes significantly at (P < 0.05) more efficiently than that in the SB pre-treatment one. Therefore, we postulate that SB can be used therapeutically in combination with TC treatment to modulate TC genotoxic effect by reducing its oxidative stress, and thus being an appropriate agonist agent to combine with TC than each compound alone.

Radiosensitization of esophageal carcinoma cells by the silencing of BMI-1

Radiotherapy (RT) has been widely used to treat cancer patients, particularly esophageal cancer patients. B-cell-specific Moloney murine leukemia virus integration site-1 (BMI-1) plays an important role in promoting the growth of cancer cells after exposure to irradiation. The present study aimed to characterize the effects of BMI-1 on the proliferation and invasion of cancer cells, as well as the mechanism involved in the regulation of the growth of esophageal cancer ECA109 and TE13 cells. The expression levels of the BMI-1 gene and protein in esophageal cancer ECA109 and TE13 cells were determined by quantitative PCR and western blotting after transfection. Co-immunoprecipitation (Co-IP) assay was employed to detect the interaction of BMI-1 with r-H2AX and H2AK119ub. We used flow cytometry to analyze the cell cycle distribution and apoptosis of transfected cells after irradiation or not, and examined cellular growth and invasion in vitro by MTS and Transwell assays. The results revealed that shRNA targeting the BMI-1 gene and protein downregulated BMI-1 expression after transfection for 24 h. The proliferation and invasion of tumor cells in the BMI-1‑shRNA group were suppressed after RT. In addition, the interaction of BMI-1, H2AK119ub and r-H2AX was increased after exposure to IR, followed by an increased apoptosis rate and decreased percentage of cells arrested at the G2/M phase after irradiation and silencing of BMI-1 by shRNA. Knockdown of BMI-1 expression decreased the phosphorylation of H2AX, upregulated p16, and induced the radiosensitivity of esophageal cancer ECA109 and TE13 cells in vitro and significantly inhibited the growth and invasion of tumor cells. The mechanisms were found to be abrogation of cell cycle arrest at the G2/M stage and promotion of apoptosis.

Inhibition of tribbles protein-1 attenuates radioresistance in human glioma cells

Radiotherapy is one of the remedies in the treatment of glioma. The radioresistance is a major drawback, of which the mechanism is unclear. Tribble protein and histone deacetylase are involved in the cancer pathogenesis. This study aims to test a hypothesis that the histone deacetylase inhibitors attenuate the radioresistance in human glioma cells. In this study, human glioma cells were cultured. The cells were treated with irradiation with or without a histone deacetylase inhibitor, butyrate. Apoptosis of the glioma cells was assessed by flow cytometry. The results showed that human glioma cells expressed a low level of Trib1, which was significantly up regulated by exposure to small doses (2 Gy/day for 4 days) of irradiation. Trib1-deficient glioma cells showed an enhanced response to irradiation-induced apoptosis. Exposure to small doses of irradiation, Trib1 formed a complex with pHDAC1 (phosphor histone deacetylase-1) to inhibit p53 expression in glioma cells. The presence of HDAC1 inhibitor, butyrate or parthenolide, significantly enforced irradiation-induced glioma cell apoptosis. In conclusion, the Trib1 plays a critical role in the development of radioresistance of glioma cells. The data suggest that inhibition of Trib1 or HDAC1 has the potential to prevent or attenuate the radioresistance.

Fractionated Ionizing Radiation Promotes Epithelial-Mesenchymal Transition in Human Esophageal Cancer Cells through PTEN Deficiency-Mediated Akt Activation

In some esophageal cancer patients, radiotherapy may not prevent distant metastasis thus resulting in poor survival. The underlying mechanism of metastasis in these patients is not well established. In this study, we have demonstrated that ionizing radiation may induce epithelial-mesenchymal transition (EMT) accompanied with increased cell migration and invasion, through downregulation of phosphatase and tensin homolog (PTEN), and activation of Akt/GSK-3β/Snail signaling. We developed a radioresistant (RR) esophageal squamous cancer cell line, KYSE-150/RR, by fractionated ionizing radiation (IR) treatment, and confirmed its radioresistance using a clonogenic survival assay. We found that the KYSE-150/RR cell line displayed typical morphological and molecular characteristics of EMT. In comparison to the parental cells, KYSE-150/RR cells showed an increase in post-IR colony survival, migration, and invasiveness. Furthermore, a decrease in PTEN in KYSE-150/RR cells was observed. We postulated that over-expression of PTEN may induce mesenchymal-epithelial transition in KYSE-150/RR cells and restore IR-induced increase of cell migration. Mechanistically, fractionated IR inhibits expression of PTEN, which leads to activation of Akt/GSK-3β signaling and is associated with the elevated levels of Snail protein, a transcription factor involved in EMT. Correspondingly, treatment with LY294002, a phosphatidylinositol-3-kinase inhibitor, mimicked PTEN overexpression effect in KYSE-150/RR cells, further suggesting a role for the Akt/GSK-3β/Snail signaling in effects mediated through PTEN. Together, these results strongly suggest that fractionated IR-mediated EMT in KYSE-150/RR cells is through PTEN-dependent pathways, highlighting a direct proinvasive effect of radiation treatment on tumor cells.

Histone deacetylase inhibitor sodium butyrate suppresses DNA double strand break repair induced by etoposide more effectively in MCF-7 cells than in HEK293 cells

Background

Histone deacetylase inhibitors (HDACi’s) are emerging as promising anticancer drugs alone or in combination with chemotherapy or radiotherapy agents. Previous research suggests that HDACi’s have a high degree of selectivity for killing cancer cells, but little is known regarding the impact of different cellular contexts on HDACi treatment. It is likely that the molecular mechanisms of HDACi’s involve processes that depend on the chromatin template, such as DNA damage and repair. We sought to establish the connection between the HDACi sodium butyrate and DNA double-strand break (DSB) damage in human breast cancer MCF-7 and non-cancerous human embryonic kidney293 (HEK293) cells.

Results

Sodium butyrate inhibited the proliferation of both HEK293 and MCF-7 cells in a dose- and time- dependent manner, but the effects on MCF-7 cells were more obvious. This differential effect on cell growth was not explained by differences in cell cycle arrest, as sodium butyrate caused an arrest in G₁/G₂ phase and a decrease in S phase for both cell lines. At high doses of sodium butyrate or in combination with etoposide, MCF-7 cells formed fewer colonies than HEK293 cells. Furthermore, sodium butyrate enhanced the formation of etoposide-induced γ-H2AX foci to a greater extent in MCF-7 than in HEK293 cells. The two cells also displayed differential patterns in the nuclear expression of DNA DSB repair proteins, which could, in part, explain the cytotoxic effects of sodium butyrate.

Conclusions

These studies suggest that sodium butyrate treatment leads to a different degree of chromatin relaxation in HEK293 and cancerous MCF-7 cells, which results in differential sensitivity to the toxic effects of etoposide in controlling damaged DNA repair.

Three measurable and modifiable enteric microbial biotransformations relevant to cancer prevention and treatment

Interdisciplinary scientific evaluation of the human microbiota has identified three enteric microbial biotransformations of particular relevance for human health and well-being, especially cancer. Two biotransformations are counterproductive; one is productive. First, selective bacteria can reverse beneficial hepatic hydroxylation to produce toxic secondary bile acids, especially deoxycholic acid. Second, numerous bacterial species can reverse hepatic detoxification-in a sense, retoxify hormones and xeonobiotics-by deglucuronidation. Third, numerous enteric bacteria can effect a very positive biotransformation through the production of butyrate, a small chain fatty acid with anti-cancer activity. Each biotransformation is addressed in sequence for its relevance in representative gastrointestinal and extra-intestinal cancers. This is not a complete review of their connection with every type of cancer. The intent is to introduce the reader to clinically relevant microbial biochemistry plus the emerging evidence that links these to both carcinogenesis and treatment. Included is the evidence base to guide counseling for potentially helpful dietary adjustments.