Insulin receptor substrate-1 and -2 mediate resistance to glucose-induced caspase-3 activation in human neuroblastoma cells.

Hyperglycemia in patients with type 2 diabetes causes multiple neuronal complications, e.g., diabetic polyneuropathy, cognitive decline, and embryonic neural crest defects due to increased apoptosis. Possible mechanisms of neuronal response to increased glucose burden are still a matter of debate. Insulin and insulin-like growth factor-1 (IGF-1) receptor signaling inhibits glucose-induced caspase-3 activation and apoptotic cell death. The insulin receptor substrates (IRS) are intracellular adapter proteins mediating insulin's and IGF-1's intracellular effects. Even though all IRS proteins have similar function and structure, recent data suggest different actions of IRS-1 and IRS-2 in mediating their anti-apoptotic effects in glucose neurotoxicity. We therefore investigated the role of IRS-1/-2 in glucose-induced caspase-3 activation using human neuroblastoma cells. Overexpression of IRS-1 or IRS-2 caused complete resistance to glucose-induced caspase-3 cleavage. Inhibition of PI3-kinase reversed this protective effect of IRS-1 or IRS-2. However, MAP-kinases inhibition had only minor impact. IRS overexpression increased MnSOD abundance as well as BAD phosphorylation while Bim and BAX levels remained unchanged. Since Akt promotes cell survival at least partially via phosphorylation and inhibition of downstream forkhead box-O (FoxO) transcription factors, we generated neuroblastoma cells stably overexpressing a dominant negative mutant of FoxO1 mimicking activation of the insulin/IGF-1 pathway on FoxO-mediated transcription. Using these cells we showed that FoxO1 is not involved in neuronal protection mediated by increased IRS-1/-2 expression. Thus, overexpression of both IRS-1 and IRS-2 induces complete resistance to glucose-induced caspase-3 activation via PI3-kinase mediated BAD phosphorylation and MnSOD expression independent of FoxO1.

Features of extramedullary myeloma relapse: high proliferation, minimal marrow involvement, adverse cytogenetics: a retrospective single-center study of 24 cases.

Extramedullary (e) relapse in multiple myeloma(MM) has an adverse prognosis, but knowledge concerning biological features and preferred treatment is scarce. We screened the myeloma registry of our institution for eMM relapses and identified 24 cases among 357 patients (pts).Only 8% of eMM relapses occurred after initial therapy, but 54% occurred after third-line or subsequent therapy. Baseline molecular cytogenetics revealed high-risk features in 10 of 19 evaluable patients. Most frequently, eMM presented as soft tissue (67%) and organ involvement (25%) or malignant effusion (12.5%). Incidence of leptomeningeal/CNS involvement was 21%. At eMM relapse, bone marrow infiltration was absent in 46% and low in 21%. Ten eMM biopsies were available showing increased proliferation, i.e., Ki-67 of 67%(range, 30­90%) of all cancer cells. Pts received radiation therapy, dose-intense chemotherapy, novel agents, and allogeneic SCT resulting in an overall response rate of 54%. Median progression-free survival was 2 (95% CI 0.08­3.92) and median overall survival 7 months (95% CI 3.56­10.43), respectively,with only three patients being alive at 12 months from diagnosis. EMM relapse may present at any anatomical site with frequent CNS involvement. Biological features include increased proliferation and low rate of marrow involvement.Prognosis remains poor despite intensive treatment.