Suberoylanilide hydroxamic acid affects γH2AX expression in osteosarcoma, atypical teratoid rhabdoid tumor and normal tissue cell lines after irradiation

Selective Targeting of Class I Histone Deacetylases in a Model of Human Osteosarcoma

Dysregulation of histone deacetylases (HDACs) is associated with the pathogenesis of human osteosarcoma, which may present an epigenetic vulnerability as well as a therapeutic target. Domatinostat (4SC-202) is a next-generation class I HDAC inhibitor that is currently being used in clinical research for certain cancers, but its impact on human osteosarcoma has yet to be explored. In this study, we report that 4SC-202 inhibits osteosarcoma cell growth in vitro and in vivo. By analyzing cell function in vitro, we show that the anti-tumor effect of 4SC-202 involves the combined induction of cell-cycle arrest at the G2/M phase and apoptotic program, as well as a reduction in cell invasion and migration capabilities. We also found that 4SC-202 has little capacity to promote osteogenic differentiation. Remarkably, 4SC-202 revised the global transcriptome and induced distinct signatures of gene expression in vitro. Moreover, 4SC-202 decreased tumor growth of established human tumor xenografts in immunodeficient mice in vivo. We further reveal key targets regulated by 4SC-202 that contribute to tumor cell growth and survival, and canonical signaling pathways associated with progression and metastasis of osteosarcoma. Our study suggests that 4SC-202 may be exploited as a valuable drug to promote more effective treatment of patients with osteosarcoma and provide molecular insights into the mechanism of action of class I HDAC inhibitors.

Combination of rapamycin and SAHA enhanced radiosensitization by inducing autophagy and acetylation in NSCLC

Radiotherapy plays an essential role in the treatment of non-small-cell lung cancer (NSCLC). However, cancer cells' resistance to ionizing radiation (IR) is the primary reason for radiotherapy failure leading to tumor relapse and metastasis. DNA double-strand breaks (DSB) repair after IR is the primary mechanism of radiotherapy resistance. In this study, we investigated the effects of autophagy-inducing agent, Rapamycin (RAPA), combined with the histone deacetylase inhibitor (HDACi), Suberoylanilide Hydroxamic Acid (SAHA), on the radiosensitivity of A549 and SK-MES-1 cells, and examined the combination effects on DNA damage repair, and determined the level of autophagy and acetylation in A549 cells. We also investigated the combination treatment effect on the growth of A549 xenografts after radiotherapy, and the level of DNA damage, autophagy, and acetylation. Our results showed that RAPA combined with SAHA significantly increased the inhibitory effect of radiotherapy compared with the single treatment group. The combined treatment increased the expression of DNA damage protein γ-H2AX and decreased DNA damage repair protein expression. RAPA combined with SAHA was induced mainly by regulating acetylation levels and autophagy. The effect of combined treatment to increase radiotherapy sensitivity will be weakened by inhibiting the level of autophagy. Besides, the combined treatment also showed a significantly inhibited tumor growth in the A549 xenograft model. In conclusion, these results identify a potential therapeutic strategy of RAPA combined with SAHA as a radiosensitizer to decreased DSB repair and enhanced DNA damage by inducing acetylation levels and autophagy for NSCLC.

Histone Deacetylase Inhibitors in Pediatric Brain Cancers: Biological Activities and Therapeutic Potential

Brain cancers are the leading cause of cancer-related deaths in children. Biological changes in these tumors likely include epigenetic deregulation during embryonal development of the nervous system. Histone acetylation is one of the most widely investigated epigenetic processes, and histone deacetylase inhibitors (HDACis) are increasingly important candidate treatments in many cancer types. Here, we review advances in our understanding of how HDACis display antitumor effects in experimental models of specific pediatric brain tumor types, i.e., medulloblastoma (MB), ependymoma (EPN), pediatric high-grade gliomas (HGGs), and rhabdoid and atypical teratoid/rhabdoid tumors (ATRTs). We also discuss clinical perspectives for the use of HDACis in the treatment of pediatric brain tumors.

Deletion of INMAP postpones mitotic exit and induces apoptosis by disabling the formation of mitotic spindle

INMAP was first identified as a spindle protein that plays important roles in cell-cycle progression, and previous studies have revealed that its abnormal expression leads to mitotic disorder and the growth inhibition of human tumor xenografts, but the underlying mechanism is still unclear. In this study, we knocked out INMAP in HEK293T cells, a strain of human embryonic renal cells, through CRISPR-Cas9 gene editing technology, resulting in obvious cell growth inhibition. In this system, the deletion of INMAP caused obviously apoptosis. And we also found that knockout of INMAP caused micronuclei formation, chromosome aberration, and γH2AX expression upregulation, suggesting DNA damage induction and genomic stability impairment. As a principal component of spindle, the expression of β-tubulin, detected through Western blot, is obviously upregulated in HEK293T-INMAP^-/-. Meanwhile, the level of Cyclin B is also upregulated, whereas, that of Cyclin E, downregulated, with the postponement of mitotic exit and the assembly anomaly of spindle. These results suggest that the deletion of INMAP block the formation of spindle, leading to arrest of cell cycle and DNA damage, finally blocking cell proliferation and inducing apoptosis. Therefore, INMAP is an indispensable factor for genomic integrity and normal mitotic exit.

Network Pharmacology Integrated Molecular Docking Reveals the Antiosteosarcoma Mechanism of Biochanin A

Background

As the malignant tumor with the highest incidence in teenagers, osteosarcoma has become a major problem in oncology research. In addition to surgical management, the pharmacotherapeutic strategy for osteosarcoma treatment is an attractive way to explore. It has been demonstrated that biochanin A has an antitumor capacity on multiple kinds of solid tumor, including osteosarcoma. But the precise mechanism of biochanin A against osteosarcoma is still needed to be discovered.

Objective

To identify the potential therapeutic targets of biochanin A in treating osteosarcoma.

Methods

In present study, an integrated approach including network pharmacology and molecular docking technique was conducted, which mainly comprises target prediction, network construction, gene ontology, and pathway enrichment. CCK8 test was employed to evaluate the cell viability of MG63 cells. Western-blot was used to verify the target proteins of biochanin A.

Results

Ninety-six and 114 proteins were obtained as the targets of biochanin A and osteosarcoma, respectively. TP53, IGF1, JUN, BGLAP, ATM, MAPK1, ATF3, H2AFX, BAX, CDKN2A, and EGF were identified as the potential targets of biochanin A against osteosarcoma. Based on the western-blot detection, the expression of BGLAP, BAX, and ATF3 in MG63 cell line changed under the treatment of biochanin A.

Conclusion

Biochanin A can effectively suppress the proliferation of osteosarcoma and regulate the expression of BGLAP, BAX, and ATF3, which may act as the potential therapeutic targets of osteosarcoma.

Enhancement of Soft Tissue Sarcoma Cell Radiosensitivity by Poly(ADP-ribose) Polymerase-1 Inhibitors

Soft tissue sarcomas (STS) are aggressive tumors with a poor prognosis. Poly(ADP-ribose) polymerase (PARP)-1 inhibitors (PARPi) enhance the cytotoxic effects of radiation. In this study, we evaluated the effect of PARPi on survival and DNA damage of irradiated STS cells. For clonogenic assays, STS cell lines were irradiated with or without olaparib, iniparib or veliparib pretreatment. The effect of PARP inhibition on γ-H2AX and Rad51 foci formation, on PARP-1, phospho-ERK and cleaved caspase-3 protein expression and on cell cycle progression was evaluated on irradiated rhabdomyosarcoma cells pretreated with olaparib. The results from this work showed that PARPi induced significant radiosensitization in STS cells. Rhabdomyosarcoma cells showed the highest increase in radiosensitivity, with a radiosensitization enhancement ratio at 50% survival (ER50) of 3.41 with veliparib. All PARPi exerted a synergistic effect when combined with radiation. Fibrosarcoma cells showed an ER50 of 2.29 with olaparib. Leiomyosarcoma and liposarcoma cells showed their highest ER50 with veliparib (1.71 and 1.84, respectively). In rhabdomyosarcoma, olaparib enhanced the formation of radiation-induced γ-H2AX/Rad51 foci and PARP-1 cleavage, induced slightly increased expression of cleaved caspase-3 and reduced phospho-ERK expression. Moreover, the combination of olaparib and radiation resulted in a significantly enhanced cell cycle arrest in the G₂/M phase compared to the two treatments alone. In conclusion, we have shown that PARPi are potent radiosensitizers of human STS cells. These results support the pursuit of further investigations into the effects of PARPi combined with radiation on STS.

Histone Deacetylase Inhibitor Induced Radiation Sensitization Effects on Human Cancer Cells after Photon and Hadron Radiation Exposure

Suberoylanilide hydroxamic acid (SAHA) is a histone deacetylase inhibitor, which has been widely utilized throughout the cancer research field. SAHA-induced radiosensitization in normal human fibroblasts AG1522 and lung carcinoma cells A549 were evaluated with a combination of γ-rays, proton, and carbon ion exposure. Growth delay was observed in both cell lines during SAHA treatment; 2 μM SAHA treatment decreased clonogenicity and induced cell cycle block in G1 phase but 0.2 μM SAHA treatment did not show either of them. Low LET (Linear Energy Transfer) irradiated A549 cells showed radiosensitization effects on cell killing in cycling and G1 phase with 0.2 or 2 μM SAHA pretreatment. In contrast, minimal sensitization was observed in normal human cells after low and high LET radiation exposure. The potentially lethal damage repair was not affected by SAHA treatment. SAHA treatment reduced the rate of γ-H2AX foci disappearance and suppressed RAD51 and RPA (Replication Protein A) focus formation. Suppression of DNA double strand break repair by SAHA did not result in the differences of SAHA-induced radiosensitization between human cancer cells and normal cells. In conclusion, our results suggest SAHA treatment will sensitize cancer cells to low and high LET radiation with minimum effects to normal cells.

Enhanced inhibition of clonogenic survival of human medulloblastoma cells by multimodal treatment with ionizing irradiation, epigenetic modifiers, and differentiation-inducing drugs

Background

Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis.

Methods

In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2′-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start.

Results

All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures.

Conclusion

In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.

Depletion of Histone Demethylase Jarid1A Resulting in Histone Hyperacetylation and Radiation Sensitivity Does Not Affect DNA Double-Strand Break Repair

Histone demethylases have recently gained interest as potential targets in cancer treatment and several histone demethylases have been implicated in the DNA damage response. We investigated the effects of siRNA-mediated depletion of histone demethylase Jarid1A (KDM5A, RBP2), which demethylates transcription activating tri- and dimethylated lysine 4 at histone H3 (H3K4me3/me2), on growth characteristics and cellular response to radiation in several cancer cell lines. In unirradiated cells Jarid1A depletion lead to histone hyperacetylation while not affecting cell growth. In irradiated cells, depletion of Jarid1A significantly increased cellular radiosensitivity. Unexpectedly, the hyperacetylation phenotype did not lead to disturbed accumulation of DNA damage response and repair factors 53BP1, BRCA1, or Rad51 at damage sites, nor did it influence resolution of radiation-induced foci or rejoining of reporter constructs. We conclude that the radiation sensitivity observed following depletion of Jarid1A is not caused by a deficiency in repair of DNA double-strand breaks.

Low-Dose Histone Deacetylase Inhibitor Treatment Leads to Tumor Growth Arrest and Multi-Lineage Differentiation of Malignant Rhabdoid Tumors

PURPOSE

Malignant rhabdoid tumor (MRT) and atypical teratoid rhabdoid tumors (ATRT) are rare aggressive undifferentiated tumors primarily affecting the kidney and CNS of infants and young children. MRT are almost exclusively characterized by homozygous deletion or inactivation of the chromatin remodeling gene SMARCB1 SMARCB1 protein loss leads to direct impairment of chromatin remodeling and we have previously reported a role for this protein in histone acetylation. This provided the rationale for investigating the therapeutic potential of histone deactylase inhibitors (HDACi) in MRT.

EXPERIMENTAL DESIGN

Whereas previously HDACis have been used at doses and schedules that induce cytotoxicity, in the current studies we have tested the hypothesis, both in vitro and in vivo, that sustained treatment of human MRT with low-dose HDACi can lead to sustained cell growth arrest and differentiation.

RESULTS

Sustained low-dose panobinostat (LBH589) treatment led to changes in cellular morphology associated with a marked increase in the induction of neural, renal, and osteoblast differentiation pathways. Genome-wide transcriptional profiling highlighted differential gene expression supporting multilineage differentiation. Using mouse xenograft models, sustained low-dose LBH589 treatment caused tumor growth arrest associated with tumor calcification detectable by X-ray imaging. Histological analysis of LBH589-treated tumors revealed significant regions of ossification, confirmed by Alizarin Red staining. Immunohistochemical analysis showed increased TUJ1 and PAX2 staining suggestive of neuronal and renal differentiation, respectively.

CONCLUSIONS

Low-dose HDACi treatment can terminally differentiate MRT tumor cells and reduce their ability to self-renew. The use of low-dose HDACi as a novel therapeutic approach warrants further investigation. Clin Cancer Res; 22(14); 3560-70. ©2016 AACR.

Establishment of a patient-derived orthotopic osteosarcoma mouse model

Background

Osteosarcoma (OS) is the most common pediatric primary malignant bone tumor. As the prognosis for patients following standard treatment did not improve for almost three decades, functional preclinical models that closely reflect important clinical cancer characteristics are urgently needed to develop and evaluate new treatment strategies. The objective of this study was to establish an orthotopic xenotransplanted mouse model using patient-derived tumor tissue.

Methods

Fresh tumor tissue from an adolescent female patient with osteosarcoma after relapse was surgically xenografted into the right tibia of 6 immunodeficient BALB/c Nu/Nu mice as well as cultured into medium. Tumor growth was serially assessed by palpation and with magnetic resonance imaging (MRI). In parallel, a primary cell line of the same tumor was established. Histology and high-resolution array-based comparative genomic hybridization (aCGH) were used to investigate both phenotypic and genotypic characteristics of different passages of human xenografts and the cell line compared to the tissue of origin.

Results

A primary OS cell line and a primary patient-derived orthotopic xenotranplanted mouse model were established. MRI analyses and histopathology demonstrated an identical architecture in the primary tumor and in the xenografts. Array-CGH analyses of the cell line and all xenografts showed highly comparable patterns of genomic progression. So far, three further primary patient-derived orthotopic xenotranplanted mouse models could be established.

Conclusion

We report the first orthotopic OS mouse model generated by transplantation of tumor fragments directly harvested from the patient. This model represents the morphologic and genomic identity of the primary tumor and provides a preclinical platform to evaluate new treatment strategies in OS.

Suberoylanilide hydroxamic acid (SAHA) and cladribine synergistically induce apoptosis in NK-LGL leukaemia

Natural killer (NK) large granular lymphocyte (LGL) leukaemia features a clonal proliferation of CD3(-) NK cells that can be classified into either aggressive or chronic categories. The NKL cell line, derived from an aggressive Asian NK cell leukaemia, and patient samples from chronic NK-LGL leukaemia were used in our study to probe for synergistic efficacy of the epigenetic drugs vorinostat (SAHA) and cladribine in this disease. We demonstrate that histone deacetylases (HDACs) are over-expressed in both aggressive and chronic NK leukaemia. Administration of the HDAC inhibitor SAHA reduces class I and II HDAC expression and enhances histone acetylation in leukaemic NK cells. In vitro combination treatment with SAHA and cladribine dose-dependently exerts synergistic cytotoxic and apoptotic effects on leukaemic NK cells. Expression profiling of apoptotic regulatory genes suggests that both compounds led to caspase-dependent apoptosis through activation of intrinsic mitochondrial and extrinsic death receptor pathways. Collectively, these data show that combined epigenetic therapy, using HDAC and DNA methyltransferase inhibitors, may be a promising therapeutic approach for NK-LGL leukaemia.

Altered regulation of DNA ligase IV activity by aberrant promoter DNA methylation and gene amplification in colorectal cancer

Colorectal cancer (CRC) presents as a very heterogeneous disease which cannot sufficiently be characterized with the currently known genetic and epigenetic markers. To identify new markers for CRC we scrutinized the methylation status of 231 DNA repair-related genes by methyl-CpG immunoprecipitation followed by global methylation profiling on a CpG island microarray, as altered expression of these genes could drive genomic and chromosomal instability observed in these tumors. We show for the first time hypermethylation of MMP9, DNMT3A and LIG4 in CRC which was confirmed in two CRC patient groups with different ethnicity. DNA ligase IV (LIG4) showed strong differential promoter methylation (up to 60%) which coincided with downregulation of mRNA in 51% of cases. This functional association of LIG4 methylation and gene expression was supported by LIG4 re-expression in 5-aza-2'-deoxycytidine-treated colon cancer cell lines, and reduced ligase IV amounts and end-joining activity in extracts of tumors with hypermethylation. Methylation of LIG4 was not associated with other genetic and epigenetic markers of CRC in our study. As LIG4 is located on chromosome 13 which is frequently amplified in CRC, two loci were tested for gene amplification in a subset of 47 cases. Comparison of amplification, methylation and expression data revealed that, in 30% of samples, the LIG4 gene was amplified and methylated, but expression was not changed. In conclusion, hypermethylation of the LIG4 promoter is a new mechanism to control ligase IV expression. It may represent a new epigenetic marker for CRC independent of known markers.

Radiosensitization by histone deacetylase inhibition in an osteosarcoma mouse model

BACKGROUND

Osteosarcomas (OS) are highly malignant and radioresistant tumors. Histone deacetylase inhibitors (HDACi) constitute a novel class of anticancer agents. We sought to investigate the effect of combined treatment with suberoylanilide hydroxamic acid (SAHA) and radiotherapy in OS in vivo.

METHODS

Clonogenic survival of human OS cell lines as well as tumor growth delay of OS xenografts were tested after treatment with either vehicle, radiotherapy (XRT), SAHA, or XRT and SAHA. Tumor proliferation, necrosis, microvascular density, apoptosis, and p53/p21 were monitored by immunohistochemistry. The CD95 pathway was performed by flow cytometry, caspase (3/7/8) activity measurements, and functional inhibition of CD95 death signaling.

RESULTS

Combined treatment with SAHA and XRT markedly reduced the surviving fraction of OS cells as compared to XRT alone. Likewise, dual therapy significantly inhibited OS tumor growth in vivo as compared to XRT alone, reflected by reduced tumor proliferation, impaired angiogenesis, and increased apoptosis. Addition of HDACi to XRT led to elevated p53, p21, CD95, and CD95L expression. Inhibition of CD95 signaling reduced HDACi- and XRT-induced apoptosis.

CONCLUSION

Our data show that HDACi increases the radiosensitivity of osteosarcoma cells at least in part via ligand-induced apoptosis. HDACi thus emerge as potentially useful treatment components of OS.

Survivin, a target to modulate the radiosensitivity of Ewing's sarcoma

BACKGROUND AND PURPOSE

Radiotherapy constitutes an essential element in the multimodal therapy of Ewing's sarcoma. Compared to other sarcomas, Ewing tumors normally show a good response to radiotherapy. However, there are consistently tumors with a radioresistant phenotype, and the underlying mechanisms are not known in detail. Here we investigated the association between survivin protein expression and the radiosensitivity of Ewing's sarcoma in vitro.

MATERIAL AND METHODS

An siRNA-based knockdown approach was used to investigate the influence of survivin expression on cell proliferation, double-strand break (DSB) induction and repair, apoptosis and colony-forming ability in four Ewing's sarcoma cell lines with and without irradiation.

RESULTS

Survivin protein and mRNA were upregulated in all cell lines tested in a dose-dependent manner. As a result of survivin knockdown, STA-ET-1 cells showed reduced cell proliferation, an increased number of radiation-induced DSBs, and reduced repair. Apoptosis was increased by knockdown alone and increased further in combination with irradiation. Colony formation was significantly reduced by survivin knockdown in combination with irradiation.

CONCLUSION

Survivin is a radiation-inducible protein in Ewing's sarcoma and its down-regulation sensitizes cells toward irradiation. Survivin knockdown in combination with radiation inhibits cell proliferation, repair, and colony formation significantly and increases apoptosis more than each single treatment alone. This might open new perspectives in the radiation treatment of Ewing's sarcoma.