Enzastaurin (LY317615), a protein kinase Cbeta inhibitor, inhibits the AKT pathway and induces apoptosis in multiple myeloma cell lines.

Enzastaurin (LY317615), an acyclic bisindolylmaleimide, is an oral inhibitor of the protein kinase Cbeta isozyme. The objective of this study was to assess the efficacy of enzastaurin in inducing apoptosis in multiple myeloma (MM) cell lines and to investigate possible mechanisms of apoptosis. Cell proliferation assays were done on a variety of MM cell lines with unique characteristics (dexamethasone sensitive, dexamethasone resistant, chemotherapy sensitive, and melphalan resistant). The dexamethasone-sensitive MM.1S cell line was used to further assess the effect of enzastaurin in the presence of dexamethasone, insulin-like growth factor-I (IGF-I), interleukin-6, and the pan-specific caspase inhibitor ZVAD-fmk. Enzastaurin increased cell death in all cell lines at clinically significant low micromolar concentrations (1-3 micromol/L) after 72 hours of treatment. Dexamethasone and enzastaurin were shown to have an additive effect on MM.1S cell death. Although IGF-I blocked the effect of 1 micromol/L enzastaurin, IGF-I did not abrogate cell death induced with 3 mumol/L enzastaurin. Moreover, enzastaurin-induced cell death was not affected by interleukin-6 or ZVAD-fmk. GSK3beta phosphorylation, a reliable pharmacodynamic marker for enzastaurin activity, and AKT phosphorylation were both decreased with enzastaurin treatment. These data indicate that enzastaurin induces apoptosis in MM cell lines in a caspase-independent manner and that enzastaurin exerts its antimyeloma effect by inhibiting signaling through the AKT pathway.

The selective protein kinase C beta inhibitor enzastaurin induces apoptosis in cutaneous T-cell lymphoma cell lines through the AKT pathway.

Enzastaurin displays pro-apoptotic properties against a spectrum of malignancies and is currently being investigated in clinical trials. We have investigated the effects of enzastaurin on the viability of the cutaneous T-cell lymphoma cell lines HuT-78 and HH by using 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, cell cycle analysis, propidium iodide and annexin-V staining, and caspase-3-mediated proteolytic activation. Enzastaurin-treatment decreased cell viability, increased annexin V-FITC-positive cells, and increased the proportion of sub-G1 populations in both cell lines that was not reversed by the T-cell growth stimulating cytokines IL-2, IL-7, IL-15. Enzastaurin-induced cell death involved caspase-3-activated cleavage of poly(ADP-ribose) polymerase that was inhibited by the pan-caspase inhibitor ZVAD-fmk, whereas the increase in sub-G1 population was only partially inhibited by ZVAD-fmk. Furthermore, enzastaurin downregulated AKT activity and its downstream effectors GSK3beta and ribosomal protein S6. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway has been implicated in the growth and survival of hematologic malignancies and inhibition of this pathway is considered as a therapeutic target. Protein kinase C activation contributes to PI3K/AKT activation, but it is unknown how enzastaurin may interfere with signaling through this pathway. These results demonstrate that enzastaurin, at clinically achievable concentrations, induces apoptosis and affects AKT signaling, and provide a rationale for further in vivo studies addressing the therapeutic efficacy in cutaneous T-cell lymphoma patients.

T-cell non-Hodgkin lymphoma.

T-cell non-Hodgkin lymphomas (NHLs) are uncommon malignancies. The current WHO/EORTC classification recognizes 9 distinct clinicopathologic peripheral T-cell NHLs. These disorders have unique characteristics and require individualized diagnostic and therapeutic strategies. Tremendous progress has been made in recent years in the understanding of the pathogenesis of these disorders. Specific chromosomal translocations and viral infections are now known to be associated with certain lymphomas. In this review, we describe their clinical and pathologic features. We also discuss the use of molecular studies in the diagnostic work-up of T-cell lymphomas. Because of the rarity of these disorders and the lack of well-designed clinical trials, the treatment of peripheral T-cell NHLs is often challenging. Additional studies are required to learn more about the biology of these diseases, which may lead to more optimal and possibly targeted therapies.

Management of adult patients with persistent idiopathic thrombocytopenic purpura following splenectomy: a systematic review.

BACKGROUND: Treatment of chronic refractory idiopathic thrombocytopenic purpura is a dilemma because many patients have minimal symptoms, response to treatment is uncertain, and treatments may have serious adverse effects. PURPOSE: To determine the effectiveness of treatments for adult patients with idiopathic thrombocytopenic purpura who have not responded to splenectomy. DATA SOURCES: English-language reports from 1966 through 2003 that were retrieved from MEDLINE and Reference Update and bibliographies of retrieved articles. STUDY SELECTION: Articles reporting 5 or more total patients were reviewed to select eligible patients. Patients were eligible for inclusion if they were more than 16 years of age, had idiopathic thrombocytopenic purpura for more than 3 months, had a previous splenectomy, and had a platelet count less than 50 x 10(9) cells/L. DATA EXTRACTION: Patients were assessed for platelet count response, bleeding complications, duration of follow-up, and death. Complete remission was defined as a normal platelet count with no treatment for more than 3 months and for the duration of follow-up. DATA SYNTHESIS: 90 articles with 656 patients treated with 22 therapies met selection criteria. Azathioprine, cyclophosphamide, and rituximab had the most reported complete responses, but they were reported in only 41 to 109 patients. Reported complete response rates ranged from 17% to 27%, but 36% to 42% of patients had no response with these 3 treatments. Most reports described only platelet count responses; bleeding outcomes were reported in only 63 patients (10%). Only 111 (17%) of the 656 eligible patients had pretreatment platelet counts of less than 10 x 10(9) cells/L. No treatment method was reported in more than 20 patients. CONCLUSIONS: Evidence for the effectiveness of any treatment for patients with idiopathic thrombocytopenic purpura and persistent severe thrombocytopenia after splenectomy is minimal. Potentially effective treatments must be evaluated by randomized, controlled trials to determine both benefit and safety.