Geldanamycin (GA) binds to heat shock protein 90 (Hsp90) and interferes with its function which is to protect various cellular proteins involved in signaling, growth control, and survival from ubiquitination and subsequent degradation by the proteasome. Recently, we demonstrated that GA inhibited migration of glioma cells in vitro associated with downregulation of hypoxia-inducible factor (HIF-1 alpha) and phosphorylation of focal adhesion kinase (FAK) (Zagzag et al., 2003, J Cell Physiol 196:394-402). Here, we have investigated the mechanisms through which GA treatment of the T98G glioma cell line induces apoptosis. We found that GA treatment induced cell death in a caspase-dependent manner through activation of caspase-3 and PARP cleavage together with release of cytochrome c and apoptosis inducing factor (AIF) from the mitochondria. Use of synchronized T98G cells showed that GA treatment of glioma cells during S-phase enhanced cytotoxicity followed by M-phase arrest, resulting in mitotic catastrophe. In addition, apoptosis was associated with the downregulation of the survival protein, phosphorylated Akt (pAkt), an important signaling protein in the PI3K pathway, that is overexpressed in many cancers including gliomas. Given that many glioma tumors show deregulation of the PI3K signaling pathway, either through loss of the tumor suppressor protein PTEN or overexpression of the growth factor EGFR, the ability to identify different subsets of patients using simple immunohistochemistry for the presence of absence of pAkt could enable selection of the appropriate kinase inhibitor, such as GA, for drug therapy. Based on our data presented here, GA or its analogs may have potential in the treatment of glioma.

Following peripheral inflammation, NMDA receptor (NMDAR) activation in spinal cord dorsal horn neurons facilitates the generation of pain in response to low threshold inputs (allodynia) and signals the phosphorylation of protein kinase C (pPKC) and extracellular signal-regulated kinase 2 (pERK2). Intraplantar complete Freund's adjuvant (CFA) induces inflammatory nociception (allodynic pain) at 24 hours (h) with a concurrent increase in neuronal pPKCgamma and pERK2 but not glial pERK2. These effects are attenuated in a spatial knockout of the NMDAR (NR1 KO) confined to SCDH neurons. Although glia and proinflammatory cytokines are implicated in the maintenance of inflammatory pain and neuronal activation, the role of NMDARs and neuronal-glial-cytokine interactions that initiate and maintain inflammatory pain are not well defined. In the maintenance phase of inflammatory pain at 96h after CFA the NR1 KO mice are no longer protected from allodynia and the SCDH expression of pPKCgamma and pERK2 are increased. At 96h the expression of the proinflammatory cytokine, IL-1beta, and pERK2 are increased in astrocytes. Intrathecal IL-1 receptor antagonist (IL-1ra), acting on neuronal IL-1 receptors, completely reverses the allodynia at 96h after CFA. Deletion of NMDAR-dependent signaling in neurons protects against early CFA-induced allodynia. Subsequent NMDAR-independent signaling that involves neuronal expression of pPKCgamma and the induction of pERK2 and IL-1beta in activated astrocytes contributes to the emergence of NMDAR-independent inflammatory pain behavior at 96h after CFA. Effective reduction of the initiation and maintenance of inflammatory pain requires targeting the neuron-astrocyte-cytokine interactions revealed in these studies.

The mechanism of action of many chemotherapeutic agents targets the cell cycle. Recently, we demonstrated cytotoxic and other anti-tumor effects of flavopiridol, the first synthetic cyclin dependent kinase (CDK) inhibitor to enter clinical trials, on the murine GL261 glioma cell line in vitro (Newcomb et al., Cell Cycle 2003; 2:243). Given that flavopiridol has demonstrated anti-tumor activity in several human xenograft models, we wanted to evaluate it for anti-glioma activity in vivo in our established subcutaneous and intracranial GL261 experimental tumor models. In particular, the intracranial animal model recapitulates many of the histopathological and biological features of human high-grade glioma including both necrosis with pseudopalisading and invasion of the brain adjacent to tumor. Here we tested the activity of flavopiridol against tumors formed by GL261 cells, first as subcutaneous implants, and then in the intracranial model. We demonstrate efficacy of flavopiridol as a single modality treatment in delaying tumor growth in both animal models. We hypothesize that flavopiridol treatment induced tumor growth delay by two possible mechanisms involving growth arrest combined with recruitment of tumor cells to S-phase. Based on our findings, flavopiridol should be considered as a treatment approach for patients with high-grade glioma. © L a n d e s B i o s c i e n c e 2 0 0 4. N o t f o r d i s t r i b u t i o n .

Glioblastoma (GBM) remains one of the most challenging solid cancers to treat due to its highly proliferative, angiogenic and invasive nature. The small molecule CDK inhibitor, flavopiridol, has demonstrated antitumor activity in human xenograft models and is currently in clinical trials showing efficacy in patients with advanced disease. We have developed an experimental animal model using the murine glioma GL261 cells as a novel in vivo system to screen potential therapeutic agents for GBM. Results of in vitro testing demonstrate that flavopiridol has several relevant clinical characteristics such as its ability to:

This article describes a case of severe opioid-induced pruritus following systemic morphine administration. Symptoms did not resolve after administration of antihistamines or rotation to fentanyl or hydromorphone, but oral oxycodone and small-dose intravenous naloxone did alleviate the patient’s itching. The pathogenesis of opioidinduced pruritus and the rationale for opioid rotation are briefly discussed. Current and possible future therapeutic options are mentioned.