nutlin-3a and Brain-Neoplasms

Topics: Biomarkers, Tumor; Brain Neoplasms; Gene Expression Profiling; Glioma; Humans; Imidazoles; Mutation; Neoplasm Grading; Oximes; Piperazines; Precision Medicine; Tumor Suppressor Protein p53; Zearalenone

Glioblastoma (GB) is the most common and aggressive malignant tumor of the central nervous system. Despite current intensive treatment regimens, consisting of surgical resection followed by radiotherapy with concomitant and adjuvant temozolomide (TMZ) chemotherapy, the prognosis of patients with GB remains extremely poor. Considering that alterations of the p53 tumor suppressor pathway have a key role in both GB development and resistance to TMZ treatment, the re‑activation of p53 could be an effective therapeutic approach against GB. In this study, we challenged p53 wild‑type and mutant GB cell lines with RITA, a molecule originally identified for its ability to restore p53 functions, although it was subsequently shown to act also through p53‑independent mechanisms. We examined the effects of RITA on GB cell viability, through MTS and clonogenic assays, and analyzed cell death through cytoflourimetric analyses. In all the tested GB cell lines, RITA significantly reduced the cell proliferative and clonogenic potential and induced cell accumulation in the S and/or G2/M cell cycle phases and massive p53‑dependent apoptosis. Moreover, RITA was more effective than the well‑known p53 re‑activating molecule, nutlin‑3, and did not affect the viability of normal astrocytes. In addition, RITA decreased survivin expression and induced DNA damage, two mechanisms that likely contribute to its anti‑tumor effects. Furthermore, RITA synergized with TMZ and was able to decrease the expression of MGMT, which is a crucial player in TMZ resistance. Thus, although further studies are warranted to clarify the exact mechanisms of action of RITA, the data of this study suggest the potential of such an approach for GB therapy, which may also help to overcome resistance to TMZ.

Topics: Brain Neoplasms; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cell Survival; Drug Resistance, Neoplasm; Drug Synergism; Furans; Glioblastoma; Humans; Imidazoles; Mutation; Piperazines; Protein Binding; Proto-Oncogene Proteins c-mdm2; Temozolomide; Tumor Suppressor Protein p53

OBJECTIVE Improvement in treatment outcome for patients with glioblastoma multiforme (GBM) requires a multifaceted approach due to dysregulation of numerous signaling pathways. The murine double minute 2 (MDM2) protein may fulfill this requirement because it is involved in the regulation of growth, survival, and invasion. The objective of this study was to investigate the impact of modulating MDM2 function in combination with front-line temozolomide (TMZ) therapy in GBM. METHODS The combination of TMZ with the MDM2 protein-protein interaction inhibitor nutlin3a was evaluated for effects on cell growth, p53 pathway activation, expression of DNA repair proteins, and invasive properties. In vivo efficacy was assessed in xenograft models of human GBM. RESULTS In combination, TMZ/nutlin3a was additive to synergistic in decreasing growth of wild-type p53 GBM cells. Pharmacodynamic studies demonstrated that inhibition of cell growth following exposure to TMZ/nutlin3a correlated with: 1) activation of the p53 pathway, 2) downregulation of DNA repair proteins, 3) persistence of DNA damage, and 4) decreased invasion. Pharmacokinetic studies indicated that nutlin3a was detected in human intracranial tumor xenografts. To assess therapeutic potential, efficacy studies were conducted in a xenograft model of intracranial GBM by using GBM cells derived from a recurrent wild-type p53 GBM that is highly TMZ resistant (GBM10). Three 5-day cycles of TMZ/nutlin3a resulted in a significant increase in the survival of mice with GBM10 intracranial tumors compared with single-agent therapy. CONCLUSIONS Modulation of MDM2/p53-associated signaling pathways is a novel approach for decreasing TMZ resistance in GBM. To the authors' knowledge, this is the first study in a humanized intracranial patient-derived xenograft model to demonstrate the efficacy of combining front-line TMZ therapy and an inhibitor of MDM2 protein-protein interactions.

Topics: Animals; Antineoplastic Agents, Alkylating; Brain Neoplasms; Combined Modality Therapy; Disease Models, Animal; Glioblastoma; Humans; Imidazoles; Piperazines; Proto-Oncogene Proteins c-mdm2; Temozolomide; Xenograft Model Antitumor Assays

Aurora kinase inhibitors displayed activity in pre-clinical neuroblastoma models. Here, we studied the effects of the pan-aurora kinase inhibitor tozasertib (VX680, MK-0457) and the aurora kinase inhibitor alisertib (MLN8237) that shows some specificity for aurora kinase A over aurora kinase B in a panel of neuroblastoma cell lines with acquired drug resistance. Both compounds displayed anti-neuroblastoma activity in the nanomolar range. The anti-neuroblastoma mechanism included inhibition of aurora kinase signalling as indicated by decreased phosphorylation of the aurora kinase substrate histone H3, cell cycle inhibition in G2/M phase, and induction of apoptosis. The activity of alisertib but not of tozasertib was affected by ABCB1 expression. Aurora kinase inhibitors induced a p53 response and their activity was enhanced in combination with the MDM2 inhibitor and p53 activator nutlin-3 in p53 wild-type cells. In conclusion, aurora kinases are potential drug targets in therapy-refractory neuroblastoma, in particular for the vast majority of p53 wild-type cases.

Topics: Antineoplastic Agents; Apoptosis; ATP Binding Cassette Transporter, Subfamily B; Aurora Kinase A; Aurora Kinase B; Azepines; Brain Neoplasms; Cell Cycle Checkpoints; Cell Proliferation; Drug Resistance, Neoplasm; Drug Synergism; Gene Expression Regulation, Neoplastic; Histones; Humans; Imidazoles; Neuroblastoma; Phosphorylation; Piperazines; Primary Cell Culture; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-mdm2; Pyrimidines; Signal Transduction; Tumor Suppressor Protein p53

A critical component of the cellular stress response, the p53 tumor suppressor protein must be functional for many cancer therapies to be effective. Adjuvant therapies that augment p53 function are predicted to sensitize tumor cells to cancer therapies that rely upon p53 for their efficacy. Of those strategies currently being explored to enhance p53 function, inhibition of the ubiquitin ligase, MDM2, a negative regulator of p53, has shown promise. Here, we investigated whether MDM2 antagonism might be effective in inducing cell death in human medulloblastoma (MB) cells. Nutlin-3, a small-molecule inhibitor of MDM2, potently induced apoptosis in MB cells with wild-type TP53. Moreover, nutlin-3 potentiated p53 activation and growth impairment of MB cells in combination with the classic DNA-damaging agent doxorubicin. Together, these results support the concept that MDM2 antagonists may be therapeutically beneficial for patients with MB tumors.

Topics: Antibiotics, Antineoplastic; Apoptosis; Blotting, Western; Brain Neoplasms; Cell Cycle; Cell Death; Cell Line, Tumor; Coloring Agents; Doxorubicin; Humans; Imidazoles; Medulloblastoma; Piperazines; Proto-Oncogene Proteins c-mdm2; Tetrazolium Salts; Thiazoles; Tumor Suppressor Protein p53

Integrins play a role in the resistance of advanced cancers to radiotherapy and chemotherapy. In this study, we show that high expression of the α5 integrin subunit compromises temozolomide-induced tumor suppressor p53 activity in human glioblastoma cells. We found that depletion of the α5 integrin subunit increased p53 activity and temozolomide sensitivity. However, when cells were treated with the p53 activator nutlin-3a, the protective effect of α5 integrin on p53 activation and cell survival was lost. In a functional p53 background, nutlin-3a downregulated the α5 integrin subunit, thereby increasing the cytotoxic effect of temozolomide. Clinically, α5β1 integrin expression was associated with a more aggressive phenotype in brain tumors, and high α5 integrin gene expression was associated with decreased survival of patients with high-grade glioma. Taken together, our findings indicate that negative cross-talk between α5β1 integrin and p53 supports glioma resistance to temozolomide, providing preclinical proof-of-concept that α5β1 integrin represents a therapeutic target for high-grade brain tumors. Direct activation of p53 may remain a therapeutic option in the subset of patients with high-grade gliomas that express both functional p53 and a high level of α5β1 integrin.

Topics: Animals; Antineoplastic Agents, Alkylating; Brain Neoplasms; Cell Line, Tumor; Dacarbazine; Drug Resistance, Neoplasm; Glioblastoma; Humans; Imidazoles; Integrin alpha5beta1; Mice; Piperazines; Temozolomide; Treatment Outcome; Tumor Suppressor Protein p53