Yuri B. Pride

Critical role for Gab2 in transformation by BCR/ABL

The BCR/ABL oncogene causes chronic myelogenous leukemia (CML) in humans and a CML-like disease, as well as lymphoid leukemia, in mice. p210 BCR/ABL is an activated tyrosine kinase that phosphorylates itself and several cellular signaling proteins. The autophosphorylation site tyrosine 177 binds the adaptor Grb2 and helps determine the lineage and severity of BCR/ABL disease: Tyr177 mutation (BCR/ABL-Y177F) dramatically impairs myeloid leukemogenesis, while diminishing lymphoid leukemogenesis. The critical signal(s) from Tyr177 has remained unclear. We report that Tyr177 recruits the scaffolding adaptor Gab2 via a Grb2/Gab2 complex. Compared to BCR/ABL-expressing Ba/F3 cells, BCR/ABL-Y177F cells exhibit markedly reduced Gab2 tyrosine phosphorylation and association of phosphatidylinositol-3 kinase (PI3K) and Shp2 with Gab2 and BCR/ABL, and decreased PI3K/Akt and Ras/Erk activation, cell proliferation, and spontaneous migration. Remarkably, bone marrow myeloid progenitors from Gab2 (-/-) mice are resistant to transformation by BCR/ABL, whereas lymphoid transformation is diminished as a consequence of markedly increased apoptosis. BCR/ABL-evoked PI3K/Akt and Ras/Erk activation also are impaired in Gab2 (-/-) primary myeloid and lymphoid cells. Our results identify Gab2 and its associated proteins as key determinants of the lineage and severity of BCR/ABL transformation.

The BCR/ABL Tyrosine Kinase Induces Production of Reactive Oxygen Species in Hematopoietic Cells

The BCR/ABL oncogene causes chronic myelogenous leukemia, a myeloproliferative disorder characterized by clonal expansion of hematopoietic progenitor cells and myeloid cells. It is shown here that transformation of the hematopoietic cell lines Ba/F3, 32Dcl3, and MO7e with BCR/ABL results in an increase in reactive oxygen species (ROS) compared with quiescent, untransformed cells. The increase in ROS was directly due to BCR/ABL because it was blocked by the ABL-specific tyrosine kinase inhibitor STI571. Oxidative stress through ROS is believed to have many biochemical effects, including the potential ability to inhibit protein-tyrosine phosphatases (PTPases). To understand the significance of increased production of ROS, a model system was established in which hydrogen peroxide (H2O2) was added to untransformed cells to mimic the increase in ROS induced constitutively by BCR/ABL. H2O2 substantially reduced total cellular PTPase activity to a degree approximately equivalent to that of pervanadate, a well known PTPase inhibitor. Further, stimulation of untransformed cells with H2O2 or pervanadate increased tyrosine phosphorylation of each of the most prominent known substrates of BCR/ABL, including c-ABL, c-CBL, SHC, and SHP-2. Treatment of the BCR/ABL-expressing cell line MO7/p210 with the reducing agents pyrrolidine dithiocarbamate orN-acetylcysteine reduced the accumulation of ROS and also decreased tyrosine phosphorylation of cellular proteins. Further, treatment of MO7e cells with H2O2 or pervanadate increased the tyrosine kinase activity of c-ABL. Drugs that alter ROS metabolism or reactivate PTPases may antagonize BCR/ABL transformation.

Effect of Intensive Statin Therapy on Clinical Outcomes Among Patients Undergoing Percutaneous Coronary Intervention for Acute Coronary Syndrome PCI-PROVE IT: A PROVE IT-TIMI 22 (Pravastatin or Atorvastatin Evaluation and Infection Therapy- Thrombolysis In Myocardial Infarction 22) Substudy

OBJECTIVES The goal of this analysis was to determine whether intensive statin therapy, compared with moderate-dose statin therapy, leads to a reduction in major adverse cardiovascular events (MACE) among patients undergoing percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS). BACKGROUND When compared with moderate-dose statins, intensive statin therapy reduces MACE among patients with ACS. The role of intensive statin therapy specifically among patients who undergo PCI for ACS is unknown. METHODS Outcomes were compared in 2,868 patients who underwent PCI for ACS just prior to enrollment in the PROVE IT-TIMI 22 (Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis In Myocardial Infarction 22) trial, which randomized patients to either atorvastatin 80 mg or pravastatin 40 mg daily. The incidence of the primary composite end point of all-cause mortality, myocardial infarction, unstable angina leading to hospitalization, and revascularization after 30 days and stroke was evaluated, as was the incidence of target vessel revascularization (TVR) and non-TVR during follow-up. RESULTS Treatment with 80 mg atorvastatin reduced the incidence of the composite end point (21.5% vs. 26.5%, hazard ratio: 0.78, 95% confidence interval: 0.67 to 0.91, p=0.002) and lowered the incidence of both TVR (11.4% vs. 15.4%, p=0.001) and non-TVR (8.0% vs. 10.5%, p=0.017) compared with 40 mg pravastatin. After adjusting for on-treatment serum low-density lipoprotein cholesterol and C-reactive protein concentrations, the odds of TVR with high-dose statin therapy remained significant (odds ratio: 0.74, p=0.015) while the odds of non-TVR did not (odds ratio: 0.92, p=0.55). CONCLUSIONS Among patients with ACS who undergo PCI, intensive statin therapy reduces MACE compared with moderate-dose statin therapy. The reduction in the incidence of TVR was independent of low-density lipoprotein cholesterol and C-reactive protein lowering and may therefore be due, at least in part, to a pleiotropic effect of high-dose statin therapy. (PROVE IT-TIMI 22; NCT00382460).

Association of blood glucose with angiographic and clinical outcomes among patients with ST-segment elevation myocardial infarction (from the CLARITY-TIMI-28 study).

Overt hyperglycemia has been associated with adverse clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI). The association of hypoglycemia and mild hyperglycemia with angiographic outcomes and the effect of clopidogrel on these outcomes have not been extensively evaluated. Patients with STEMI enrolled in the CLARITY-TIMI 28 trial (n=3,491) were divided into 6 groups based on admission blood glucose level (<81, 81 to 99, 100 to 125, 126 to 149, 150 to 199, and >199 mg/dl). Angiographic and clinical outcomes were analyzed. Thirty-day mortality was increased (p<0.001) in patients with hypoglycemia (glucose<81 mg/dl, 6.3%) and severe hyperglycemia (glucose>199 mg/dl, 10.4%) compared with the euglycemic group (glucose 81 to 99 mg/dl, 2.6%). Occlusion of the infarct-related artery (IRA; Thrombolysis In Myocardial Infarction flow grade 0/1) at scheduled angiography was more common with increased glucose (9.3% for glucose 81 to 99 mg/dl, 15.6% for glucose>199 mg/dl, p=0.004). Multivariable analysis demonstrated that hyperglycemia was associated with a twofold increase in the composite of an occluded IRA, death, or recurrent MI before angiography (glucose>199 mg/dl, odds ratio 1.93, 95% confidence interval 1.17 to 3.18, p=0.01; glucose 150 to 199 mg/dl, odds ratio 2.04, 95% confidence interval 1.30 to 3.22, p=0.002). There was no significant interaction between clopidogrel administration and the association of glucose and IRA patency (p interaction=NS). In conclusion, in patients with STEMI, hypoglycemia and severe hyperglycemia are associated with increased 30-day mortality. IRA patency after fibrinolytic administration is related to admission glucose independent of clopidogrel administration.

Outcomes Among Patients With ST-Segment–Elevation Myocardial Infarction Presenting to Interventional Hospitals With and Without On-Site Cardiac Surgery

Background—Primary percutaneous coronary intervention (pPCI) is the preferred reperfusion strategy for patients with ST-segment–elevation myocardial infarction (STEMI). The quality of care and safety and efficacy of pPCI at hospitals without on-site open heart surgery (No-OHS hospitals) remains an area of active investigation. Methods and Results—The National Registry of Myocardial Infarction enrolled 58 821 STEMI patients from 214 OHS hospitals (n=54 076) and 52 No-OHS hospitals (n=4745) with PCI capabilities from 2004 to 2006. Patients presenting to OHS hospitals had substantially lower in-hospital mortality (7.0% versus 9.8%, P<0.001) and were more likely to receive any form of acute reperfusion therapy (80.8% versus 70.8%, P<0.001). Patients who presented to OHS hospitals were more likely to receive guideline recommended medications within 24 hours of arrival. In a propensity score model matching for patient characteristics and transfer status, in-hospital mortality remained significantly lower among patients presenting to OHS hospitals (7.2% versus 9.3%, P=0.025). When this model was further adjusted for differences in the use of acute reperfusion therapy, medications administered within 24 hours and hospital characteristics, the mortality difference was of borderline significance (hazard ratio, 0.87; 95% CI, 0.75 to 1.01; P=0.067). When the propensity score analysis was restricted to patients who underwent pPCI, there was no significant difference in mortality (3.8% versus 3.3%, P=0.44). Conclusions—STEMI patients presenting to No-OHS hospitals have substantially higher mortality, are less likely to receive guideline recommended medications within 24 hours, and are less likely to undergo acute reperfusion therapy, although this difference was of borderline significance after adjusting for hospital and treatment variables. There was no difference in mortality among patients undergoing pPCI.

Angiographic and Clinical Outcomes Among Patients With Acute Coronary Syndromes Presenting With Isolated Anterior ST-Segment Depression: A TRITON–TIMI 38 (Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel–Thrombolysis In Myocardial Infarction 38) Substudy

OBJECTIVES This study sought to determine angiographic and clinical outcomes among patients with acute coronary syndrome (ACS) presenting with isolated anterior ST-segment depression on 12-lead electrocardiogram (ECG). BACKGROUND In patients with ACS, anterior ST-segment depression on 12-lead ECG may represent plaque rupture with: 1) acute thrombotic occlusion with elevation of cardiac biomarkers (+Tn); 2) a patent artery with +Tn; or 3) a patent artery with -Tn. METHODS The TRITON-TIMI 38 (Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition with Prasugrel-Thrombolysis In Myocardial Infarction 38) enrolled 13,608 ACS patients. Those with isolated anterior (leads V(1) to V(4)) ST-segment depression were analyzed. Angiograms and ECGs were interpreted by local investigators. RESULTS There were 1,198 (8.8%) patients with isolated anterior ST-segment depression. Of those, 314 (26.2%) had an occluded culprit artery (TIMI flow grade 0/1) and +Tn, 641 (53.5%) had a patent culprit artery (TIMI flow grade 2/3) and +Tn, and 243 (20.3%) had TIMI flow grade 2/3 and -Tn. Among patients with an occluded artery, the culprit artery was most often the left circumflex artery (48.4%). The 30-day incidence of the composite of death and MI was significantly higher among patients with an occluded artery (8.6%) than among those with a patent culprit artery and either +Tn (6.3%) or -Tn (2.9%) (3-way p = 0.006). Among patients with an occluded artery, the median time from ECG to percutaneous coronary intervention was 29.4 h (interquartile range 26.1 to 44.1 h). CONCLUSIONS Among ACS patients presenting with isolated anterior ST-segment depression, over one-quarter had an occluded culprit artery and elevated cardiac biomarkers. These patients had significantly worse clinical outcomes, and few underwent urgent angiography.

Acute Detection of ST-Elevation Myocardial Infarction Missed on Standard 12-Lead ECG With a Novel 80-Lead Real-Time Digital Body Surface Map: Primary Results From the Multicenter OCCULT MI Trial

STUDY OBJECTIVE Although 80-lead ECG body surface mapping is more sensitive for ST-elevation myocardial infarction (STEMI) than the 12-lead ECG, its clinical utility in chest pain in the emergency department (ED) has not been studied. We sought to determine the prevalence, clinical care patterns, and clinical outcomes of patients with STEMI identified on 80-lead but not on 12-lead (80-lead-only STEMI). METHODS The Optimal Cardiovascular Diagnostic Evaluation Enabling Faster Treatment of Myocardial Infarction trial was a multicenter prospective observational study of moderate- to high-risk chest pain patients presenting to the ED. Patients received simultaneous 12-lead and 80-lead ECGs as part of their initial evaluation and were treated according to the standard of care, with clinicians blinded to the 80-lead results. The primary outcome of the trial was door-to-sheath time in patients with 80-lead-only STEMI versus patients with STEMI identified by 12-lead alone (12-lead STEMI). Secondary outcomes included angiographic and clinical outcomes at 30 days. RESULTS One thousand eight hundred thirty patients were evaluated, 91 had a discharge diagnosis of 12-lead STEMI, and 25 patients met criteria for 80-lead-only STEMI. Eighty-four of the 91 12-lead STEMI patients underwent cardiac catheterization, with a median door-to-sheath time of 54 minutes, versus 14 of the 25 80-lead-only STEMI patients, with a door-to-sheath time of 1,002 minutes (estimated treatment difference in median=881; 95% confidence interval 181 to 1,079 minutes). Clinical outcomes and revascularization rates, however, were similar between 80-lead-only STEMI and 12-lead STEMI patients. CONCLUSION The 80-lead ECG provides an incremental 27.5% increase in STEMI detection versus the 12-lead. Patients with 80-lead-only STEMI have adverse outcomes similar to those of 12-lead STEMI patients but are treated with delayed or conservative invasive strategies.

Outcomes Among Patients With Non–ST-Segment Elevation Myocardial Infarction Presenting to Interventional Hospitals With and Without On-Site Cardiac Surgery

OBJECTIVES The goals of this analysis were: 1) to evaluate outcomes among non-ST-segment elevation myocardial infarction (NSTEMI) patients presenting to hospitals with on-site cardiac surgery (OHS hospitals) and without on-site cardiac surgery (No-OHS hospitals); and 2) to specifically examine outcomes among the subset of NSTEMI patients undergoing percutaneous coronary intervention (PCI). BACKGROUND Whether backup cardiac surgery improves outcomes among NSTEMI patients or is simply a marker of better adherence to guideline recommendations is unknown. METHODS The NRMI (National Registry of Myocardial Infarction) enrolled 100,071 NSTEMI patients from 2004 to 2006. Outcomes were evaluated in the population as a whole and in propensity-matched analyses in the entire population and in the subset of patients undergoing PCI. RESULTS In-hospital mortality was significantly lower at OHS hospitals (5.0% vs. 8.8%, p < 0.001). Patients presenting to OHS hospitals were significantly more likely to receive aspirin, beta-blockers, and statins (p < 0.05 for all) and to undergo PCI (38.4% vs. 14.1%, p < 0.001). In the propensity-matched model, the difference in mortality remained significant (5.9% vs. 8.5%, p < 0.001). After adjusting for differences in medications administered within 24 h of arrival and hospital characteristics, the difference in mortality was nearly attenuated (hazard ratio: 0.89, 95% confidence interval: 0.79 to 1.00, p = 0.050). When the propensity-matched model was restricted to patients undergoing PCI, there was no significant difference in mortality (1.3% vs. 1.0%, p = 0.51). CONCLUSIONS NSTEMI patients presenting to No-OHS hospitals have significantly higher mortality. This appears to be due to both modifiable (lower use of guideline-recommended medications) and nonmodifiable factors (hospital size, myocardial infarction volume). In a propensity-matched analysis of patients undergoing PCI for NSTEMI, there was no significant difference in mortality.

Effect of prasugrel versus clopidogrel on outcomes among patients with acute coronary syndrome undergoing percutaneous coronary intervention without stent implantation: A TRial to assess Improvement in Therapeutic Outcomes by optimizing platelet inhibitioN with prasugrel (TRITON)–Thrombolysis in Myocardial Infarction (TIMI) 38 Substudy

BACKGROUND Prasugrel led to a significant reduction in ischemic cardiovascular events among patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) with stent implantation compared to clopidogrel. Whether this benefit extends to patients undergoing PCI without stent implantation is unknown. METHODS In TRial to assess Improvement in Therapeutic Outcomes by optimizing platelet inhibitioN with prasugrel (TRITON)-Thrombolysis in Myocardial Infarction (TIMI) 38, patients (n = 13 608) undergoing PCI for ACS were randomized to aspirin plus clopidogrel or prasugrel. This postrandomization analysis of a prespecified subgroup was restricted to patients who underwent PCI without stent implantation (n = 569). RESULTS Patients who underwent PCI without stent implantation were older and had a higher incidence of hypertension, diabetes, prior myocardial infarction (MI), prior coronary artery bypass (CABG) surgery, and renal dysfunction than patients who underwent stent implantation. In the group that did not undergo stent implantation, baseline characteristics were similar between patients receiving clopidogrel and prasugrel. The composite of cardiovascular death, nonfatal MI, and nonfatal stroke occurred in 14.2% of patients receiving prasugrel and 17.1% of patients receiving clopidogrel (HR 0.82, P = .27). There were significant reductions favoring prasugrel in the rates of urgent target vessel revascularization (TVR; HR 0.46, P = .040) and any TVR (HR 0.40, P = .009) and a trend toward a reduction in the incidence of nonfatal MI (HR 0.65, P = .11). CABG-related TIMI major bleeding was more frequent among patients receiving prasugrel. There were no significant interactions between treatment and PCI type. CONCLUSION Among ACS patients who underwent PCI without stent implantation, prasugrel therapy tended to reduce clinical ischemic events and to increase bleeding events to a similar magnitude as among patients who received stents.

Differential expression and signaling of CBL and CBL-B in BCR/ABL transformed cells.

CBL and the related CBL-B protein are two members of a family of RING finger type ubiquitin E3 ligases that are believed to function as negative regulators of signal transduction in hematopoietic and immune cells. In mice, expression of v-Cbl causes lymphomas, and targeted disruption of either the CBL gene or the CBL-B gene can result in a lymphoproliferative disorder or hypersensitivity of lymphocytes. CBL is one of the most prominent targets of the BCR/ABL tyrosine kinase oncogene. We compared the role of CBL and CBL-B in signal transduction of BCR/ABL using pairs of cell lines before and after expression of BCR/ABL. In contrast to CBL, BCR/ABL was found to rapidly downregulate the expression of CBL-B protein. The decrease in CBL-B protein induced by BCR/ABL was associated with downregulation of CBL-B mRNA. Downregulation and tyrosine phosphorylation of CBL-B required BCR/ABL kinase activity. However, despite their known similarities in structure and function, we found CBL and CBL-B proteins to be involved in distinct signaling complexes. CBL was predominantly in a complex with phosphatidylinositol 3′-kinase and CRKL, while CBL-B was not associated with any significant phosphatidylinositol 3′-kinase activity. A major CBL-B associated protein was identified as mono-ubiquitinated Vav, a nucleotide exchange factor for Rac1. These results demonstrate that BCR/ABL signals differentially through CBL and CBL-B, with downregulation of the CBL-B protein potentially contributing to BCR/ABL-mediated transformation.