Mark R. Jackson

Osteosarcoma (OSA) is the most common primary bone tumor in dogs and cats, and accurate diagnosis of OSA has therapeutic and prognostic implications. Immunohistochemistry targeting osterix (Osx), a transcription factor expressed in osteoblasts, was applied to 80 canine samples (40 OSAs and 40 controls (8 chondrosarcomas, 8 fibrosarcomas, 8 hemangiosarcomas, 8 histiocytic sarcomas, and 8 malignant melanomas)) and 40 feline samples (20 OSAs and 20 controls (5 fibrosarcomas, 5 hemangiosarcomas, 5 chondrosarcomas, 3 malignant melanomas, and 2 histiocytic sarcomas)), diagnosed histologically. All 120 samples were assessed blinded using a previously established semiquantitative scoring and classification system. In dogs, 37/40 OSAs (true positives, sensitivity 92.5%) and 2/40 controls (false positives, specificity 95.0%) were classified as OSA. In cats, 14/20 OSAs (true positives, sensitivity 70.0%) and 5/20 controls (false positives, specificity 75.0%) were classified as OSA. Tumors most often “misclassified” as OSAs were chondrosarcomas in both dogs (2/8) and cats (4/5). In 4 cases for which paired decalcified and nondecalcified samples of the same OSA were available, decalcification of OSAs did not affect classification. Quiescent canine, feline, and murine osteoblasts and canine reactive, metaplastic, and non-OSA neoplastic osseous conditions were also tested and demonstrated Osx immunoreactivity; avian and piscine osteoblasts did not. In conclusion, Osx is a highly sensitive and specific marker of canine OSA and a moderately sensitive and specific marker of feline OSA. The diagnostic algorithm applied in this study is a useful adjunctive tool in the diagnosis of canine OSA.

Radiosensitisation of G1 and G7 3D GSC by PARP inhibitor olaparib and ATM inhibitor KU55933. A, Determination of secreted VEGF by Elisa assay of media recovered from G7, E2 and R10 3D cells grown at hypoxic (1% O2) and normoxic (20% O2) conditions. Media was collected 48 h after seeding. Data represents means {plus minus} SD from 3 independent experiments performed in duplicate. B, Clonogenic survival efficiency of G1 and G7 GSC grown on 3D conditions after receiving 0 or 3 Gy in a 96-well clonogenic assay. C-E, Erlotinib (C), olaparib (D) and KU55933 (E) dose response (0.1 microM to 10 microM) at 0 and 3 Gy in G1 and G7 3D GSC. Cells were treated with respective inhibitor 2 h prior to ionizing radiation. Values were normalized to vehicle (DMSO) against their respective radiation dose. Curves were fitted with a median enhancement effect model. Statistical analysis with one-way ANOVA, *p<0.05; **p<0.005.

Akt expression in 3D GSC before and after radiation treatment. A, Bar charts representing mRNA expression of Akt, PARP and PTEN genes in G7 and E2 3D cells treated with 0 or 5 Gy. RNA extraction was performed 4 h after irradiation treatment. B, Protein expression of G7 and E2 3D GSC for Akt1, Akt2, Akt3, PARP1 and PTEN treated with 0 or 5 Gy. Cell lysates were prepared 4 h after irradiation treatment. Actin serves as loading control. C, Enrichment analysis of RNASeq data for G7 or E2 3D cells grown in the presence of VEGF comparing no radiation v radiation treatment. Analysis was performed using Biocarta_Akt_Pathway. D. Perifosine dose response (0.1 microM to 10 microM) at 0 and 3 Gy in G7 3D GSC. Cells were treated with respective inhibitor 2 h prior to ionizing radiation. Values were normalized to vehicle (DMSO) against their respective radiation dose. Curves were fitted with a median enhancement effect model. Statistical analysis with one-way ANOVA, *p<0.05; **p<0.005.

Glioblastoma is resistant to conventional treatments and has dismal prognosis. Despite promising in vitro data, molecular targeted agents have failed to improve outcomes in patients, indicating that conventional two-dimensional (2D) in vitro models of GBM do not recapitulate the clinical scenario. Responses of primary glioblastoma stem-like cells (GSC) to radiation in combination with EGFR, VEGF, and Akt inhibition were investigated in conventional 2D cultures and a three-dimensional (3D) in vitro model of GBM that recapitulates key GBM clinical features. VEGF deprivation had no effect on radiation responses of 2D GSCs, but enhanced radiosensitivity of GSC cultures in 3D. The opposite effects were observed for EGFR inhibition. Detailed analysis of VEGF and EGF signaling demonstrated a radioprotective role of Akt that correlates with VEGF in 3D and with EGFR in 2D. In all cases, positive correlations were observed between increased radiosensitivity, markers of unrepaired DNA damage and persistent phospho-DNA-PK nuclear foci. Conversely, increased numbers of Rad51 foci were observed in radioresistant populations, indicating a novel role for VEGF/Akt signaling in influencing radiosensitivity by regulating the balance between nonhomologous end-joining and homologous recombination–mediated DNA repair. Differential activation of tyrosine kinase receptors in 2D and 3D models of GBM explains the well documented discrepancy between preclinical and clinical effects of EGFR inhibitors. Data obtained from our 3D model identify novel determinants and mechanisms of DNA repair and radiosensitivity in GBM, and confirm Akt as a promising therapeutic target in this cancer of unmet need.

Erlotinib radiosensitisation of 2D GSC is VEGF-independent. A-D, Clonogenic survival of R10 GSC grown in 3D (A) and 2D (B-D) conditions and irradiated with single doses of X-rays (0-6 Gy; n=3) 2 hours after treatment of erlotinib (1microM) or vehicle (DMSO) in the presence (+VEGF) or absence (-VEGF) of VEGF (3 ng/ml). Mean {plus minus} SD of 3 independent experiments is shown; curves are fitted to a linear quadratic model. Erlotinib significantly radioprotected 3D VEGF-deprived cells (two-way ANOVA; R10 3D (-) VEGF vehicle vs 3D (-) VEGF plus erlotinib p < 0.05). No significant effect of erlotinib was observed in the presence of VEGF in 3D cells. Erlotinib radiosensitised 2D G7, E2 and R10 cells irrespective of VEGF presence (B-D). E, Quantification of gH2AX foci per nucleus in G7 3D cells treated with erlotinib in the absence of VEGF, or with VEGF after radiation treatment (24 h). Graph represents mean of medians from 3 independent experiments. p values calculated by t test (* p<0.01; ** p<0.001). F and G, Quantification of pDNA-PKcs (upper graph) and Rad51 foci (lower graph) per nucleus following radiation treatment. Graph represents mean of medians from 3 independent experiments. p values calculated by t test (* p <0.01; ** p <0.001).H, Quantification of DNA-PKcs and EGFR colocalisation per nucleus in E2 3D GSC. Approximately 40 nuclei were quantified for each condition. Box and whisker plots represent median number of signal per nucleus, p values calculated by Mann Whitney U test (*p<0.05; **p<0.005).

2D and 3D GSC exhibit similar levels of CENPF positive cells and radiation response to MK-2206. A, Representative immunofluorescent images of G7 and E2 cells grown in 2D or 3D conditions for CENPF. B, Percentage of cells showing CENPF staining per field as in (A). Graph depicts mean {plus minus}SD of three independent experiments. C, Representative immunofluorescent images for gammaH2AX foci of E2 GSC grown in 2D conditions fixed with 2% PFA at the indicated time points following ionising radiation (5 Gy). D, Percentages of cells displaying micronuclei. An average of 350 cells/condition/experiment were identified randomly and scored. Mean {plus minus} SEM of 3 independent experiments. P values calculated by t test. Aberrant DNA damage repair in VEGF-deprived GSC. E, Quantification of pDNA-PKcs (Thr2609) foci per nucleus following radiation treatment. Graph represents mean of medians from 3 independent experiments. p values calculated by t test (* p<0.01; ** p3 Rad51 foci per nucleus) were quantified and expressed as the percentage of total cells per image field. 3 fields (~ 30-50 cells per field) from 4 independent experiments were quantified. Graph depicts mean {plus minus}SD.

Statistical analysis of MK2206 efficacy study

Statistical analysis of MK2206 efficacy study