G2/M inhibitors as pharmacotherapeutic opportunities for glioblastoma:the old,the new,and the future

Glioblastoma(GBM) is one of the deadliest tumors and has a median survival of 3 months if left untreated. Despite advances in rationally targeted pharmacological approaches, the clinical care of GBM remains palliative in intent. Since the majority of altered signaling cascades involved in cancer establishment and progression eventually affect cell cycle progression, an alternative approach for cancer therapy is to develop innovative compounds that block the activity of crucial molecules needed by tumor cells to complete cell division. In this context, we review promising ongoing and future strategies for GBM therapeutics aimed towards G2/M inhibition such as anti-microtubule agents and targeted therapy against G2/M regulators like cyclin-dependent kinases,Aurora inhibitors, PLK1, BUB, 1, and BUBR1, and survivin. Moreover, we also include investigational agents in the preclinical and early clinical settings. Although several drugs were shown to be gliotoxic, most of them have not yet entered therapeutic trials. The use of either single exposure or a combination with novel compounds may lead to treatment alternatives for GBM patients in the near future.

Purification and Biochemical Characterization of Native and Pegylated Form of L-Asparaginase from Aspergillus terreus and Evaluation of Its Antiproliferative Activity

L-asparaginase is a chemotherapeutic drug used in the treatment of lymphoblastic leukemia. In the present study, the extracellular L-asparaginase produced by strain (PC-1.7A) of Aspergillus terreus was purified, characterized, and modified with polyethylene glycol. Moreover, its antiproliferative activity was evaluated. The apparent molecular weight of the enzyme was found to be 136 kDa. The optimal pH and temperature for the enzyme were 9.0℃ and 40℃, respectively. The enzyme retained 100% of the activity at 40℃ for 120 min. Pegylated L-asparaginase was more thermostable and more resistant to trypsin than native enzyme. Native L-asparaginase against human normal cells did not show cytotoxicity. However, in the leukemia cell lines RS4;11 and HL60 the antiproliferative effects of native L-asparaginase were observed after 96 and 72 h of incubation, respectively. For the first time, an L-asparaginase from fungus was evaluated as an antitumor agent in human cells lines and further investigations should be conducted to improve the knowledge about this enzyme.

Base Excision Repair Inhibition by Methoxyamine Impairs Growth and Sensitizes Osteosarcoma Cells to Conventional Treatments

The outcome of patients with osteosarcoma has not significantly improved in the last three decades. Therefore, there is still a need for the development of more effective therapeutic strategies. Methoxyamine (MX) is a base excision repair (BER) inhibitor that has shown anticancer potential by sensitizing a variety of tumor cells to ionizing radiation and chemotherapeutic drugs. In the present study, the in vitro antiproliferative effects of MX were evaluated in two osteosarcoma cell lines, HOS and MG-63. Evaluation of the influence on radiosensitivity and drug interactions in simultaneous treatments with methotrexate, doxorubicin, and cisplatin was also performed. Exposure to MX significantly decreased cell proliferation and mediated a substantial increase of apoptosis. Moreover, our results showed that MX synergized with ionizing radiation in both cell lines while potentiated the antitumor effects of cisplatin and methotrexate. Altogether, the results presented herein demonstrate the feasibility of inhibiting the BER pathway, which may in future be a promising strategy for overcoming intrinsic tumor resistance and to improve the outcome of patients with osteosarcoma.

Does DKC1 Mutation Suffice to Define the Phenotype Severity of Hoyeraal-Hreidarsson Syndrome?

Both dyskeratosis congenita (DC) and Hoyeraal-Hreidarsson Syndrome (HHS) are rare inherited bone marrow failure conditions. HHS is considered to be a variant of DC in which neurological deficits and immunodeficiencies are also present. We describe a very interesting familial cluster where an invariant point mutation of DKC1 located in the exon 11 is observed in the carrier mother and in two decedent males. The older child developed the classical phenotype of HHS at a very early age. The second affected child remains poorly symptomatic, with only mild haematological changes. Telomere shortening, with different severity, is also present in both cases. This paper discusses the clinical spectrum of inherited BM failure syndromes from the perspective different clinical presentation within a family with a DKC1 mutation.