Cryptococcus neoformans-astrocyte interactions: effect on fungal blood brain barrier disruption, brain invasion, and meningitis progression.

Cryptococcus neoformans is an opportunistic, neurotropic, and encapsulated fungus that causes life-threatening cryptococcal meningitis (CM), especially in regions of the world where AIDS is endemic. The polysaccharide capsule of C. neoformans is the fungus major virulent factor, being copiously released during infection and causing immunosuppressive defects in the host. Although the capsular material is commonly associated with reactive astrocytes in fatal CM, little is known about the molecular and cellular interactions among astroglia and C. neoformans. As astrocytes also make up the neurovascular unit at the blood-brain barrier (BBB), which C. neoformans must transverse to colonize the central nervous system and cause CM; these cells may play a significant regulatory role in the prevention and progression of infection. For example, astrocytes are implicated in neurological disease including the regulation of cerebral intracranial pressure, immune function, and water homeostasis. Hence, in this review, we provide a general overview of astroglia biology and discuss the current knowledge on C. neoformans-astrocyte interactions including their involvement in the development of CM. This "gliocentric view" of cerebral cryptococcosis suggests that therapeutic interventions particularly targeting at preserving the neuroprotective function of astrocytes may be used in preventing and managing C. neoformans BBB transmigration, brain invasion, colonization, and meningitis.

Co-treatment of LY294002 or MK-2206 with AZD5363 Attenuates AZD5363-induced Increase in the Level of Phosphorylated AKT.

Clinical trials are in progress on AZD5363, an inhibitor of protein kinase B (AKT), to assess its effects on the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. Cells treated with AKT inhibitors have been reported to activate alternative pathways in order to escape growth inhibition. AZD5363-sensitized Hs578T breast cancer cells displayed reduced levels of phosphorylated glycogen synthase kinase 3 beta (pGSK3ß). Interestingly, in AZD5363-treated cells, the level of phosphorylated (activated) AKT (pAKT) increased. Since pAKT positively correlates with cancer growth and survival, we aimed to identify conditions that could reduce AZD5363-induction of pAKT. We examined whether AZD5363 induction of pAKT could be reduced by co-treatment with inhibitors of the PI3K/AKT/mTOR pathway (LY294002, MK-2206, wortmannin, perifosine, rapamycin, everolimus, and temsirolimus). We observed that co-treatment of LY294002 or MK-2206 with AZD5363 reduced the level of pAKT. Since MK-2206 is clinically used, we propose that co-treatment using MK-2206 with AZD5363 would prove beneficial in blocking the AZD5363-induced pAKT signaling pathway. Our findings contribute to the development of AZD5363-based sensitization therapies for patients with cancer.

Anti-malarial Drugs Primaquine and Chloroquine Have Different Sensitization Effects with Anti-mitotic Drugs in Resistant Cancer Cells.

The purpose of this study was to identify conditions that would increase the sensitivity of drug-resistant cancer cells. Previously, two anti-malarial drugs, chloroquine (CHL) and primaquine (PRI), showed different sensitization effects for vinblastine (VIB)-resistant cancer cells. Herein, we tested co-treatment of cells with CHL or PRI and other microtubule-targeting cancer drugs, namely, vinorelbine (VIO), paclitaxel (PAC), docetaxel (DOC), vincristine (VIC), or halaven (HAL). We found that PRI sensitized P-glycoprotein (P-gp)-overexpressing drug-resistant KBV20C cells to all six anti-mitotic drugs to a similar extent. CHL had a similar sensitization effect only for co-treatment with PAC, DOC, VIC, and HAL, while the sensitization effect was less marked for co-treatment with VIB or VIO. FACS analysis and western blot analysis revealed that G2arrest and apoptosis showed only a slight increase on co-treatment with VIB or VIO and CHL. We also found that phospho-histone H3 and pRb were markedly increased only by PRI-VIB co-treatment, but not by CHL-VIB co-treatment. This suggests that reduction in the expression of these proteins correlates with decreased G2arrest in CHL-VIB co-treatment. We further compared the effect of another anti-malarial drug, mefloquine (MEF), in combination with the six anti-mitotic drugs. We found that MEF and PRI had similar sensitization effects in co-treatment with these anti-mitotic drugs. PRI and MEF had generally similar sensitization effects in co-treatment with anti-mitotic drugs, suggesting that they do not have any preferred anti-mitotic drug partner in co-treatment. This indicates that only CHL shows specificity in co-treatment with anti-mitotic drugs in resistant cancer cells. Our results may contribute to the choice of anti-mitotic drugs to be used in co-treatment of resistant cancer cells with the anti-malarial drugs, CHL, PRI, and MEF.