Prexasertib (LY2606368) reduces clonogenic survival by inducing apoptosis in primary patient-derived osteosarcoma cells and synergizes with cisplatin and talazoparib.

Progress in the systemic control of osteosarcoma has been limited over the past decades thus indicating the urgent clinical need for the development of novel treatment strategies. Therefore, we have recently developed new preclinical models to study promising novel agents for the treatment of pediatric osteosarcoma. The checkpoint kinase (chk) inhibitor prexasertib (LY2606368) and its salt form (LSN2940930) have recently been shown to be active in adult and pediatric malignancies, including sarcoma. We have now tested the potency of prexasertib in clonogenic survival assays in two new lines of primary patient-derived osteosarcoma cells and in two established osteosarcoma cell lines as a single agent and in combination with cisplatin and the poly ADP-ribose polymerase (PARP) inhibitor talazoparib. Prexasertib alone results in strongly reduced clonogenic survival at low nanomolar concentrations and acts by affecting cell cycle progression, induction of apoptosis and induction of double-stranded DNA breakage at concentrations that are well below clinically tolerable and safe plasma concentrations. In combination with cisplatin and talazoparib, prexasertib acts in a synergistic fashion. Chk1 inhibition by prexasertib and its combination with the DNA damaging agent cisplatin and the PARP-inhibitor talazoparib thus emerges as a potential new treatment option for pediatric osteosarcoma which will now have to be tested in preclinical primary patient derived in vivo models and clinical studies.

Single-Gap Superconductivity and Dome of Superfluid Density in Nb-Doped SrTiO_{3}.

SrTiO_{3} exhibits a superconducting dome upon doping with Nb, with a maximum critical temperature T_{c}≈0.4 K. Using microwave stripline resonators at frequencies from 2 to 23 GHz and temperatures down to 0.02 K, we probe the low-energy optical response of superconducting SrTiO_{3} with a charge carrier concentration from 0.3 to 2.2×10^{20} cm^{-3}, covering the majority of the superconducting dome. We find single-gap electrodynamics even though several electronic bands are superconducting. This is explained by a single energy gap 2Δ due to gap homogenization over the Fermi surface consistent with the low level of defect scattering in Nb-doped SrTiO_{3}. Furthermore, we determine T_{c}, 2Δ, and the superfluid density as a function of charge carrier concentration, and all three quantities exhibit the characteristic dome shape.

Histone deacetylase inhibition sensitizes osteosarcoma to heavy ion radiotherapy.

BACKGROUND: Minimal improvements in treatment or survival of patients with osteosarcoma have been achieved during the last three decades. Especially in the case of incomplete tumor resection, prognosis remains poor. Heavy ion radiotherapy (HIT) and modern anticancer drugs like histone deacetylase inhibitors (HDACi) have shown promising effects in osteosarcoma in vitro. In this study, we tested the effect of HIT and the combination of HIT and the HDACi suberoylanilide hydroxamic acid (SAHA) in a xenograft mouse model. METHODS: Osteosarcoma xenografts were established by subcutaneous injection of KHOS-24OS cells and treated with either vehicle (DMSO), SAHA, HIT or HIT and SAHA. Tumor growth was determined and tumor necrosis, proliferation rate, apoptotic rate as well as vessel density were evaluated. RESULTS: Here, we show that the combination of HIT and SAHA induced a significant delay of tumor growth through increased rate of apoptosis, increased expression of p53 and p21(Waf1/Cip1), inhibition of proliferation and angiogenesis compared to tumors treated with HIT only. CONCLUSION: HIT and in particular the combination of HIT and histone deacetylase inhibition is a promising treatment strategy in OS and may be tested in clinical trials.

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.

In vivo efficacy of the histone deacetylase inhibitor suberoylanilide hydroxamic acid in combination with radiotherapy in a malignant rhabdoid tumor mouse model.

PURPOSE: Histone deacetylase inhibitors are promising new substances in cancer therapy and have also been shown to sensitize different tumor cells to irradiation (XRT). We explored the effect as well as the radiosensitizing properties of suberoylanilide hydroxamic acid (SAHA) in vivo in a malignant rhabdoid tumor (MRT) mouse model. METHODS AND MATERIAL: Potential radiosensitization by SAHA was assessed in MRT xenografts by analysis of tumor growth delay, necrosis (HE), apoptosis (TUNEL), proliferation (ki-67) and γH2AX expression as well as dynamic 18F-Fluorodeoxyglucose Positron Emission Tomography (18F-FDG -PET) after treatment with either SAHA alone, single-dose (10 Gy) or fractionated XRT (3 × 3Gy) solely as well as in combination with SAHA compared to controls. RESULTS: SAHA only had no significant effect on tumor growth. Combination of SAHA for 8 days with single-dose XRT resulted in a higher number of complete remissions, but failed to prove a significant growth delay compared to XRT only. In contrast fractionated XRT plus SAHA for 3 weeks did induce significant tumor growth delay in MRT-xenografts. The histological examination showed a significant effect of XRT in tumor necrosis, expression of Ki-67, γH2AX and apoptosis. SAHA only had no significant effect in the histological examination. Comparison of xenografts treated with XRT and XRT plus SAHA revealed a significantly increased γH2AX expression and apoptosis induction in the mice tumors after combination treatment with single-dose as well as fractionated XRT. The combination of SAHA with XRT showed a tendency to increased necrosis and decrease of proliferation compared to XRT only, which, however, was not significant. The 18F-FDG-PET results showed no significant differences in the standard uptake value or glucose transport kinetics after either treatment. CONCLUSION: SAHA did not have a significant effect alone, but proved to enhance the effect of XRT in our MRT in vivo model.

Combination of suberoylanilide hydroxamic acid with heavy ion therapy shows promising effects in infantile sarcoma cell lines.

INTRODUCTION: The pan-HDAC inhibitor (HDACI) suberoylanilide hydroxamic acid (SAHA) has previously shown to be a radio-sensitizer to conventional photon radiotherapy (XRT) in pediatric sarcoma cell lines. Here, we investigate its effect on the response of two sarcoma cell lines and a normal tissue cell line to heavy ion irradiation (HIT). MATERIALS AND METHODS: Clonogenic assays after different doses of heavy ions were performed. DNA damage and repair were evaluated by measuring γH2AX via flow-cytometry. Apoptosis and cell cycle analysis were also measured via flow cytometry. Protein expression of repair proteins, p53 and p21 were measured using immunoblot analysis. Changes of nuclear architecture after treatment with SAHA and HIT were observed in one of the sarcoma cell lines via light microscopy after staining towards chromatin and γH2AX. RESULTS: Corresponding with previously reported photon data, SAHA lead to an increase of sensitivity to heavy ions along with an increase of DSB and apoptosis in the two sarcoma cell lines. In contrast, in the osteoblast cell line (hFOB 1.19), the combination of SAHA and HIT showed a significant radio-protective effect. Laser scanning microscopy revealed no significant morphologic changes after HIT compared to the combined treatment with SAHA. Immunoblot analysis revealed no significant up or down regulation of p53. However, p21 was significantly increased by SAHA and combination treatment as compared to HIT only in the two sarcoma cell lines--again in contrast to the osteoblast cell line. Changes in the repair kinetics of DSB p53-independent apoptosis with p21 involvement may be part of the underlying mechanisms for radio-sensitization by SAHA. CONCLUSION: Our in vitro data suggest an increase of the therapeutic ratio by the combination of SAHA with HIT in infantile sarcoma cell lines.

Enhancement of radiation response in osteosarcoma and rhabdomyosarcoma cell lines by histone deacetylase inhibition.

PURPOSE: Histone deacetylase inhibitors (HDACIs) can enhance the sensitivity of cells to photon radiation treatment (XRT) by altering numerous molecular pathways. We investigated the effect of pan-HDACIs such as suberoylanilide hydroxamic acid (SAHA) on radiation response in two osteosarcoma (OS) and two rhabdomyosarcoma (RMS) cell lines. METHODS AND MATERIALS: Clonogenic survival, cell cycle analysis, and apoptosis were examined in OS (KHOS-24OS, SAOS2) and RMS (A-204, RD) cell lines treated with HDACI and HDACI plus XRT, respectively. Protein expression was investigated via immunoblot analysis, and cell cycle analysis and measurement of apoptosis were performed using flow cytometry. RESULTS: SAHA induced an inhibition of cell proliferation and clonogenic survival in OS and RMS cell lines and led to a significant radiosensitization of all tumor cell lines. Other HDACI such as M344 and valproate showed similar effects as investigated in one OS cell line. Furthermore, SAHA significantly increased radiation-induced apoptosis in the OS cell lines, whereas in the RMS cell lines radiation-induced apoptosis was insignificant with and without SAHA. In all investigated sarcoma cell lines, SAHA attenuated radiation-induced DNA repair protein expression (Rad51, Ku80). CONCLUSION: Our results show that HDACIs enhance radiation action in OS and RMS cell lines. Inhibition of DNA repair, as well as increased apoptosis induction after exposure to HDACIs, can be mechanisms of radiosensitization by HDACIs.

Production of different phenotypes from the same genotype in the same environment by developmental variation.

The phenotype of an organism is determined by the genes, the environment and stochastic developmental events. Although recognized as a basic biological principle influencing life history, susceptibility to diseases, and probably evolution, developmental variation (DV) has been only poorly investigated due to the lack of a suitable model organism. This obstacle could be overcome by using the recently detected, robust and highly fecund parthenogenetic marbled crayfish as an experimental animal. Batch-mates of this clonal crayfish, which were shown to be isogenic by analysis of nuclear microsatellite loci, exhibited surprisingly broad ranges of variation in coloration, growth, life-span, reproduction, behaviour and number of sense organs, even when reared under identical conditions. Maximal variation was observed for the marmorated coloration, the pattern of which was unique in each of the several hundred individuals examined. Variation among identically raised batch-mates was also found with respect to fluctuating asymmetry, a traditional indicator of the epigenetic part of the phenotype, and global DNA methylation, an overall molecular marker of an animal's epigenetic state. Developmental variation was produced in all life stages, probably by reaction-diffusion-like patterning mechanisms in early development and non-linear, self-reinforcing circuitries involving behaviour and metabolism in later stages. Our data indicate that, despite being raised in the same environment, individual genotypes can map to numerous phenotypes via DV, thus generating variability among clone-mates and individuality in a parthenogenetic species. Our results further show that DV, an apparently ubiquitous phenomenon in animals and plants, can introduce components of randomness into life histories, modifying individual fitness and population dynamics. Possible perspectives of DV for evolutionary biology are discussed.

Metabolic activation of benzo[a]pyrene in vitro by hepatic cytochrome P450 contrasts with detoxification in vivo: experiments with hepatic cytochrome P450 reductase null mice.

Many studies using mammalian cellular and subcellular systems have demonstrated that polycyclic aromatic hydrocarbons, including benzo[a]pyrene (BaP), are metabolically activated by cytochrome P450s (CYPs). In order to evaluate the role of hepatic versus extra-hepatic metabolism of BaP and its pharmacokinetics, we used the hepatic cytochrome P450 reductase null (HRN) mouse model, in which cytochrome P450 oxidoreductase, the unique electron donor to CYPs, is deleted specifically in hepatocytes, resulting in the loss of essentially all hepatic CYP function. HRN and wild-type (WT) mice were treated intraperitoneally (i.p.) with 125 mg/kg body wt BaP daily for up to 5 days. Clearance of BaP from blood was analysed by high-performance liquid chromatography with fluorescence detection. DNA adduct levels were measured by (32)P-post-labelling analysis with structural confirmation of the formation of 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene by liquid chromatography-tandem mass spectrometry analysis. Hepatic microsomes isolated from BaP-treated and untreated mice were also incubated with BaP and DNA in vitro. BaP-DNA adduct formation was up to 7-fold lower with the microsomes from HRN mice than with that from WT mice. Most of the hepatic microsomal activation of BaP in vitro was attributable to CYP1A. Pharmacokinetic analysis of BaP in blood revealed no significant differences between HRN and WT mice. BaP-DNA adduct levels were higher in the livers (up to 13-fold) and elevated in several extra-hepatic tissues of HRN mice (by 1.7- to 2.6-fold) relative to WT mice. These data reveal an apparent paradox, whereby hepatic CYP enzymes appear to be more important for detoxification of BaP in vivo, despite being involved in its metabolic activation in vitro.

Determination of the DNA methylation level of the marbled crayfish: an increase in sample throughput by an optimised sample preparation.

Using a previously described capillary electrophoretic method with laser-induced fluorescence detection the genomic methylation level can be determined exactly. We present a sample preparation that eliminates the surplus of fluorescence marker used for coupling resulting in an increase of sample throughput from 75 to 250 analyses per week. The sensitivity of the method was also increased, which allows the determination of methylation levels under 1%. With these changes in sample preparation a methylation level of 1.64+/-0.03% in hepatopancreas DNA of the recently discovered marbled crayfish could be determined.