Guray Saydam

Involvement of protein phosphatase 2A in interferon-α-2b-induced apoptosis in K562 human chronic myelogenous leukaemia cells

Interferon-alpha (IFN-alpha)-2b is known to have antiproliferative effects on hematological malignant cells, especially chronic myelogenous leukaemia (CML). However, it can induce cytogenetical remissions in a very small percentage of the patients. Also during interferon therapy, resistance can emerge in the CML clones. K562 is an in vitro model cell line transformed from a Ph positive CML patient. It can be induced to differentiate to granulocytic and/or monocytic lineages with certain molecules. IFN-alpha-2b generally exerts its effects on CML cells by Janus family kinases (Jak/Stat) pathway, mostly through tyrosine kinase system. However, there is almost no data on the relevance of serine/threonine (Ser/Thr) protein phosphatase (PP) system in the interferon induced signal transduction pathways. In this study, we investigated serine/threonine protein phosphatases in the IFN-alpha-2b induced K562 cytotoxicity. Trypan blue dye exclusion test and MTT assay were utilised for determining cytotoxicity. IC(50) of IFN-alpha-2b on K562 cells was found to be 600IU/ml. However, no differentiation was determined by analysis of cell surface antigen expressions. Serine/threonine protein phosphatase inhibitors calyculin A (Cal A) and okadaic acid (OKA) augmented the IFN-alpha-2b induced cytotoxicity. Apoptosis assay by the mono-oligonucleosome detection and acridine orange/propidium iodide dye revealed marked apoptosis underlying cytotoxicity. Phosphatase enzyme assay revealed a gradual increase in protein phosphatase 2A (PP2A) activity during interferon induced cytotoxicity. Conversely, immunoblots showed no change in the expression of PP2A catalytic and regulatory subunits. In conclusion, PP2A plays a role in IFN-alpha-2b induced apoptosis of K562 cells and should be investigated as a new window furthermore.

Ruxolitinib for the treatment of inadequately controlled polycythaemia vera without splenomegaly (RESPONSE-2): a randomised, open-label, phase 3b study

BACKGROUND In the pivotal RESPONSE study, ruxolitinib, a Janus kinase (JAK)1 and JAK2 inhibitor, was superior to best available therapy at controlling haematocrit and improving splenomegaly and symptoms in patients with polycythaemia vera with splenomegaly who were inadequately controlled with hydroxyurea. In this study, we assessed the efficacy and safety of ruxolitinib in controlling disease in patients with polycythaemia vera without splenomegaly who need second-line therapy. METHODS RESPONSE-2 is a randomised, open-label, phase 3b study assessing ruxolitinib versus best available therapy in patients with polycythaemia vera done in 48 hospitals or clinics across 12 countries in Asia, Australia, Europe, and North America. Eligible patients (aged ≥18 years) with polycythaemia vera, no palpable splenomegaly, and hydroxyurea resistance or intolerance were stratified by their hydroxyurea therapy status (resistance vs intolerance) and randomly assigned (1:1) by an interactive response technology provider using a validated system to receive either oral ruxolitinib 10 mg twice daily or investigator-selected best available therapy (hydroxyurea [at the maximum tolerated dose], interferon or pegylated interferon, pipobroman, anagrelide, approved immunomodulators, or no cytoreductive treatment). Investigators and patients were not masked to treatment assignment; however, the study sponsor was masked to treatment assignment until database lock. The primary endpoint was the proportion of patients achieving haematocrit control at week 28. Analyses were done according to an intention-to-treat principle, including data from all patients randomly assigned to treatment. This study is registered with ClinicalTrials.gov (NCT02038036) and is ongoing but not recruiting patients. FINDINGS Between March 25, 2014, and Feb 11, 2015, of 173 patients assessed for eligibility, 74 patients were randomly assigned to receive ruxolitinib and 75 to receive best available therapy. At randomisation, best available therapy included hydroxyurea (37 [49%] of 75 in the best available therapy group), interferon or pegylated interferon (ten [13%] of 75), pipobroman (five [7%] of 75), lenalidomide (one [1%] of 75), no treatment (21 [28%] of 75), and other (one [1%] of 75). Haematocrit control was achieved in 46 (62%) of 74 ruxolitinib-treated patients versus 14 (19%) of 75 patients who received best available therapy (odds ratio 7·28 [95% CI 3·43-15·45]; p<0·0001). The most frequent haematological adverse events of any grade were anaemia (ten [14%] of 74 in the ruxolitinib group vs two [3%] of 75 in the best available therapy group) and thrombocytopenia (two [3%] vs six [8%]). No cases of grade 3-4 anaemia or thrombocytopenia occurred with ruxolitinib; one patient (1%) reported grade 3-4 anaemia and three patients (4%) reported grade 3-4 thrombocytopenia in the group receiving best available therapy. Frequent grade 3-4 non-haematological adverse events were hypertension (five [7%] of 74 vs three [4%] of 75) and pruritus (0 of 74 vs two [3%] of 75). Serious adverse events occurring in more than 2% of patients in either group, irrespective of cause, included thrombocytopenia (none in the ruxolitinib group vs two [3%] of 75 in the best available therapy group) and angina pectoris (two [3%] of 74 in the ruxolitinib group vs none in the best available therapy group). Two deaths occurred, both in the best available therapy group. INTERPRETATION RESPONSE-2 met its primary endpoint. The findings of this study indicate that ruxolitinib could be considered a standard of care for second-line therapy in this post-hydroxyurea patient population. FUNDING Novartis.

The roles of bioactive sphingolipids in resveratrol-induced apoptosis in HL60 acute myeloid leukemia cells

PurposeAcute promyelocytic leukemia results from a translocation between 15 and 17 chromosomes that produce PML/RARα fusion protein. PML/RARα inhibits differentiation of myeloid precursor cells at stem cell level. Resveratrol is a phytoalexin that exerts cytotoxic effects on cancer cells. Ceramides have crucial roles in cell growth, proliferation, differentiation, drug resistance, and apoptosis. In this study, we examined the possible cytotoxic effects of resveratrol on acute myeloid leukemia cells and determined the roles of ceramide-metabolizing genes in resveratrol-induced apoptosis, in addition to investigating the possibility of increasing the sensitivity of HL60 cells to resveratrol by manipulating sphingolipids.MethodsCytotoxic effects of resveratrol, C8:ceramide, PDMP, and SK-1 inhibitor were determined by XTT cell proliferation assay. Changes in caspase-3 enzyme activity and mitochondrial membrane potential (MMP) were measured using caspase-3 colorimetric assay and JC-1 MMP detection kit. Expression levels of ceramide-metabolizing genes were examined by RT-PCR.ResultsThe results revealed that manipulations of ceramide metabolism toward generation or accumulation of apoptotic ceramides increased apoptotic effects of resveratrol in HL60 cells, synergistically. More importantly, gene expression analyses revealed that resveratrol-induced apoptosis via increasing expression levels of ceramide-generating genes and decreasing expression levels of antiapoptotic sphingosine kinase-1 and glucosylceramide synthase genes.ConclusionThese results showed for the first time that increasing intracellular levels of ceramides by biochemical approaches has also increased sensitivity of HL60 cells to resveratrol. We also showed that resveratrol induces apoptosis through manipulating ceramide-metabolizing genes that resulted in the accumulation of ceramides in HL60 cells.

Resveratrol Triggers Apoptosis Through Regulating Ceramide Metabolizing Genes in Human K562 Chronic Myeloid Leukemia Cells

Resveratrol, an important phytoalexin in many plants, has been reported to have cytotoxic effects on various types of cancer. Ceramide is a bioactive sphingolipid that regulates many signaling pathways, including cell growth and proliferation, senescence and quiescence, apoptosis, and cell cycle. Ceramides are generated by longevity assurance genes (LASS). Glucosylceramide synthase (GCS) and sphingosine kinase-1 (SK-1) enzymes can convert ceramides to antiapoptotic molecules, glucosylceramide, and sphingosine-1-phosphate, respectively. C8:ceramide, an important cell-permeable analogue of natural ceramides, increases intracellular ceramide levels significantly, while 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) and SK-1 inhibitor increase accumulation of ceramides by inhibiting GCS and SK-1, respectively. Chronic myelogenous leukemia (CML) is a hematological disorder resulting from generation of BCR/ABL oncogene. In this study, we examined the roles of ceramide metabolizing genes in resveratrol-induced apoptosis in K562 CML cells. There were synergistic cytotoxic and apoptotic effects of resveratrol with coadministration of C8:ceramide, PDMP, and SK-1 inhibitor. Interestingly, there were also significant increases in expression levels of LASS genes and decreases in expression levels of GCS and SK-1 in K562 cells in response to resveratrol. Our data, in total, showed for the first time that resveratrol might kill CML cells through increasing intracellular generation and accumulation of apoptotic ceramides.

Cytotoxicity and Cell Growth Assays

Publisher Summary Various assays are in use to determine the effect of a drug on cells propagated in vitro. The trypan blue exclusion test is a rapid method to assess cell viability in response to environmental insults. When membrane integrity of the cells is compromised, there is uptake of the dye into the cells so that viable cells, which are unstained, appear clear with a refractile ring around them and nonviable cells appear dark blue colored with no refractile ring around them. Sulforhodamine B Assay (SRB) is based on the binding of the dye to basic amino acids of cellular proteins, and colorimetric evaluation provides an estimate of total protein mass, which is related to cell number. This assay has been widely used for the in vitro measurement of cellular protein content of both adherent and suspension cultures. AlamarBlue is used to monitor the reducing environment of proliferating cells. Because it is non-toxic, cells exposed to it can be returned to culture or used for other purposes. AlamarBlue takes advantage of mitochondrial reductase to convert nonfluorescent resazurin to fluorescent resorufin.

Augmentation of methylprednisolone-induced differentiation of myeloid leukemia cells by serine/threonine protein phosphatase inhibitors

To elucidate the roles of serine/threonine protein phosphatases type 1 (PP1) and type 2A (PP2A) in methylprednisolone-induced differentiation of HL60 cells into granulocytes and K562 cells into monocytes, we examined the effect of serine/threonine protein phosphatase inhibitors, okadaic acid and Cal-A on the proliferation/differentiation of HL60 and K562 cells. Okadaic acid and Cal-A augmented methylprednisolone induced granulocytic differentiation and cell death of HL60 cells and monocytic differentiation and cell death of K562 cells in different dose ranges, respectively. These data suggest an important role of PP1 and PP2A in the mechanism leading to differentiation of leukemic cells.

Arsenic trioxide and methylprednisolone use different signal transduction pathways in leukemic differentiation

Certain cell lines like HL 60 and K 562 are utilised as leukemic cell models for leukemogenesis research, which differentiate along the granulocytic and/or monocytic pathway when treated with certain inducer molecules. High dose methylprednisolone treatment has been shown to induce in vivo and in vitro differentiation of myeloid leukemia cells to mature granulocytes in patients with acute promyelocytic leukemia (APL) and other subtypes of acute myeloid leukemia (AML). Arsenic trioxide (As(2)O(3)) has been confirmed to have remission induction effects on APL. However, there are conflicting results on the effects with other AML subtypes. Also, it has been well established that the reversible phosphorylation of proteins is a major regulatory mechanism in the signal transduction pathways that control cell growth and differentiation. Serine/threonine protein phosphatases (PP) are major components of phosphorylation. In this study, we investigated the effect of As(2)O(3) on HL 60 and K 562 myeloid leukemic differentiation and compared the signalling cascades of the two inducers with respect to serine/threonine PP 1 and 2A. We utilised PP1 and PP2A inhibitors okadaic acid and calyculin A. In contrast to methylprednisolone, there was no effect of phosphatase inhibitors on As(2)O(3)-induced leukemic differentiation. Incomplete leukemic differentiation occurred with lower As(2)O(3) concentration as 10(-6)M. Unlike As(2)O(3), methylprednisolone induced complete granulocytic and/or monocytic differentiation of HL 60 and K 562 cells via upregulation of PP2A regulatory subunits. Therefore, As(2)O(3) and methylprednisolone are promising agents that have the potential to be used together in myeloid leukemic differentiation therapy.

Radioisotope synovectomy with rhenium186 in haemophilic synovitis for elbows, ankles and shoulders

Summary.  We have performed 221 radioisotope synovectomy (RS) in more than 150 children and young adults with haemophilia, age ranging 3–30 years (mean 15) in Ege Hemophilia Center, Izmir, Turkey for last 7 years. We always preferred to use Yttrium 90 (Y90) for knees; however, since 2005, we started using rhenium 186 (Re186) for medium‐sized joints with respect to safety. In this article, we have evaluated long‐term experience ranging from 6 months to 3 years (mean 18 months) with Re186 for elbows (n = 35), ankles (n = 26) and shoulders (n = 2) in total of 63 RS procedures for 49 patients. Their age range was 3–30 years and mean age was 15.5. Two mCi of Re186 intra‐articularly injected for treating target joints and chronical synovitis. After RS, joint bleedings were decreased for all patients. The best results were obtained for all joints in patients with grade‐II synovitis as like earlier experience with Y90. Excellent rates (no bleeding) were observed in grade‐II synovitis in 81% and 46% for elbows vs. 86% and 57% for ankles after 6 months and after 1 year follow‐up of patients, respectively. In grade‐III synovitis, excellent rates were 53% and 25% for elbows and 44% and 29% for ankles, respectively. In five joints for five patients, repeated injections were needed for better outcome. No adverse events such as radioisotope leakage, local inflamatory reactions or malignancy development were observed during and after RS. For medium‐sized joints, RS with Re186 seems to be either effective or safe treatment method. Our results confirm those previously published by others on the value of Re186 synoviorthesis in medium‐sized joints in haemophilia patients. After this experience, we changed our protocol and we use Re186 for all medium‐sized joints for treating chronical synovitis.

Caffeic acid phenethyl ester triggers apoptosis through induction of loss of mitochondrial membrane potential in CCRF-CEM cells

PurposeCAPE (caffeic acid phenethyl ester) is one of the most valuable and investigated component of propolis which is composed by honeybees. In the current study, we aimed at examining apoptotic effects of CAPE on CCRF-CEM leukemic cells and at determining the roles of mitochondrial membrane potential (MMP) in cell death.MethodsTrypan blue and XTT methods were used to evaluate the cytotoxicity. Apoptosis was examined by ELISA-based oligonucleotide and acridine orange/ethidium bromide dye techniques. Loss of mitochondrial membrane potential was evaluated using JC-1 dye by flow cytometric analysis and under fluorescent microscope.ResultsWe detected the time- and dose-dependent increases in cytotoxic effect of CAPE on CCRF-CEM cells. ELISA and acridine orange/ethidium bromide results showed that apoptotic cell population increased significantly in CCRF-CEM cells exposed to increasing concentrations of CAPE. On the other hand, there was significant loss of MMP determined in response to CAPE in CCRF-CEM cells.ConclusionThis in vitro data by being supported with clinical data may open the way of the potential use of CAPE for the treatment of leukemia.

Dural plasmacytoma mimicking meningioma in a patient with multiple myeloma

Apart from calvarial infiltration, intracranial involvement in multiple myeloma is uncommon. Diffuse leptomeningeal invasion with or without parenchymal involvement is most common. Dural infiltration without involvement of the parenchyma, leptomeninges or skull is rare. The differential diagnosis of a dural plasmacytoma includes meningioma, which has a similar MRI appearance, metastasis, lymphoma and sarcoma of the dura mater. We present a patient with multiple myeloma presenting with an intracerebral mass mimicking a meningioma on MRI. Multiple myeloma had been diagnosed seven years previously. The patient presented with headache and speech disturbance 12 months after autologous peripheral stem cell transplantation for recurrence of multiple myeloma. MRI revealed a left temporal extra-axial mass with a dural tail mimicking meningioma. Histopathological examination of the mass after excision showed multiple myeloma immunopositive for IgG, kappa light chain and CD38. There was no recurrence after postoperative radiotherapy. Plasmacytoma should be considered in the differential diagnosis of a solitary dural mass, particularly in a patient with multiple myeloma.