Establishment and characterization of a novel malignant astrocytoma cell line derived from a tumor removed in a patient with neurofibromatosis type 1

Identification of therapeutic sensitivities in a spheroid drug combination screen of Neurofibromatosis Type I associated High Grade Gliomas

Neurofibromatosis Type 1 (NF1) patients develop an array of benign and malignant tumors, of which Malignant Peripheral Nerve Sheath Tumors (MPNST) and High Grade Gliomas (HGG) have a dismal prognosis. About 15-20% of individuals with NF1 develop brain tumors and one third of these occur outside of the optic pathway. These non-optic pathway gliomas are more likely to progress to malignancy, especially in adults. Despite their low frequency, high grade gliomas have a disproportional effect on the morbidity of NF1 patients. In vitro drug combination screens have not been performed on NF1-associated HGG, hindering our ability to develop informed clinical trials. Here we present the first in vitro drug combination screen (21 compounds alone or in combination with MEK or PI3K inhibitors) on the only human NF1 patient derived HGG cell line available and on three mouse glioma cell lines derived from the NF1-P53 genetically engineered mouse model, which sporadically develop HGG. These mouse glioma cell lines were never exposed to serum, grow as spheres and express markers that are consistent with an Oligodendrocyte Precursor Cell (OPC) lineage origin. Importantly, even though the true cell of origin for HGG remains elusive, they are thought to arise from the OPC lineage. We evaluated drug sensitivities of the three murine glioma cell lines in a 3D spheroid growth assay, which more accurately reflects drug sensitivities in vivo. Excitingly, we identified six compounds targeting HDACs, BRD4, CHEK1, BMI-1, CDK1/2/5/9, and the proteasome that potently induced cell death in our NF1-associated HGG. Moreover, several of these inhibitors work synergistically with either MEK or PI3K inhibitors. This study forms the basis for further pre-clinical evaluation of promising targets, with an eventual hope to translate these to the clinic.

Fluorine Modifications Contribute to Potent Antiviral Activity against Highly Drug-Resistant HIV-1 and Favorable Blood-Brain Barrier Penetration Property of Novel Central Nervous System-Targeting HIV-1 Protease Inhibitors In Vitro

To date, there are no specific treatment regimens for HIV-1-related central nervous system (CNS) complications, such as HIV-1-associated neurocognitive disorders (HAND). Here, we report that two newly generated CNS-targeting HIV-1 protease (PR) inhibitors (PIs), GRL-08513 and GRL-08613, which have a P1-3,5-bis-fluorophenyl or P1-para-monofluorophenyl ring and P2-tetrahydropyrano-tetrahydrofuran (Tp-THF) with a sulfonamide isostere, are potent against wild-type HIV-1 strains and multiple clinically isolated HIV-1 strains (50% effective concentration [EC50]: 0.0001 to ∼0.0032 μM). As assessed with HIV-1 variants that had been selected in vitro to propagate at a 5 μM concentration of each HIV-1 PI (atazanavir, lopinavir, or amprenavir), GRL-08513 and GRL-08613 efficiently inhibited the replication of these highly PI-resistant variants (EC50: 0.003 to ∼0.006 μM). GRL-08513 and GRL-08613 also maintained their antiviral activities against HIV-2ROD as well as severely multidrug-resistant clinical HIV-1 variants. Additionally, when we assessed with the in vitro blood-brain barrier (BBB) reconstruction system, GRL-08513 and GRL-08613 showed the most promising properties of CNS penetration among the evaluated compounds, including the majority of FDA-approved combination antiretroviral therapy (cART) drugs. In the crystallographic analysis of compound-PR complexes, it was demonstrated that the Tp-THF rings at the P2 moiety of GRL-08513 and GRL-08613 form robust hydrogen bond interactions with the active site of HIV-1 PR. Furthermore, both the P1-3,5-bis-fluorophenyl- and P1-para-monofluorophenyl rings sustain greater contact surfaces and form stronger van der Waals interactions with PR than is the case with darunavir-PR complex. Taken together, these results strongly suggest that GRL-08513 and GRL-08613 have favorable features for patients infected with wild-type/multidrug-resistant HIV-1 strains and might serve as candidates for a preventive and/or therapeutic agent for HAND and other CNS complications.

In vitro and in vivo growth inhibition of human malignant astrocytoma cells by the farnesyltransferase inhibitor B1620

p21-Ras, the protein product of the proto-oncogene Ras is overactivated in malignant astrocytomas despite the absence of mutation. It is known that p21-Ras participates in signaling events from membrane tyrosine kinase receptors and a variety of intracellular biochemical pathways to downstream targets. Signal transduction inhibition by targeting against Ras is now thought to be a promising therapeutic strategy for malignant astrocytomas. This study demonstrates that Ras pathway inactivation by a farnesyltransferase inhibitor, B1620, effectively inhibits in vitro and in vivo growth of human astrocytoma cells, although normal human astrocytes (NHA) derived from fetal brain are resistant to B1620. Anti-proliferative effect of B1620 on in vitro growth of astrocytoma cells was examined by MTT assays and soft agar colony formation assay. B1620 inhibited anchorage-dependent growth of six astrocytoma cell lines with a median effective dose (IC50) ranging from 2.0 to 20.7 microM. However, growth of NHA was not significantly affected by B1620 even at the concentration of 100 microM. All astrocytoma cells showed apoptotic figures after Hoechst 33258 staining, when treated for 5 days at each IC50 concentration against B1620. Anchorage-independent growth of these astrocytoma cell lines was inhibited at a much lower concentration than that of anchorage-dependent growth. Daily treatment of U87 xenograft-bearing athymic mice with B1620 at 100 or 50 mg kg(-1) resulted in significant inhibition of tumor growth. A histological study of the B1620-treated tumor tissue showed decreased vascularity with numerous TUNEL-positive apoptotic cells. These results suggest that the mechanism of the growth-inhibitory effect of B1620 is anti-angiogenesis, apoptosis induction and reversion of the transformed phenotype. The potential clinical use of B1620 could be expanded to malignant astrocytomas.