Adequacy of thyroid hormone replacement for people with hypothyroidism in real-world settings: A systematic review and meta-analysis of observational studies.

OBJECTIVE: Thyroid hormone under-replacement and over-replacement are associated with adverse health outcomes. This systematic review aimed to evaluate the extent of thyroid hormone replacement adequacy for patients with known hypothyroidism in real-word settings, excluding those receiving thyroid hormone suppressive therapy as thyroid cancer treatment. DESIGN: Four electronic databases (Embase [Ovid], Medline [Ovid], PubMed and SCOPUS) were searched for published and unpublished observational studies until 12 December 2022. The results of the studies were meta-analysed to calculate pooled prevalence estimates for thyroid hormone supplementation adequacy, over-replacement and under-replacement. Quality assessment of studies was performed using the Joanna-Briggs appraisal tool for prevalence studies. RESULTS: Seven studies with a total of 4230 patients were eligible for quantitative synthesis. The pooled prevalence estimates of adequate thyroid replacement, over-replacement and under-replacement were 0.55 (95% confidence interval [CI]: 0.49-0.60, p = .001), 0.20 (95% CI: 0.14-0.27, p = .001) and 0.24 (95% CI: 0.13-0.36, p = .001), respectively. Four studies subclassified hypothyroidism and hyperthyroidism into overt and subclinical. The pooled prevalence of overt and subclinical hyperthyroidism was 0.04 (95% CI: 0.00-0.11, p = .01) and 0.17 (95% CI: 0.09-0.27 p = .001), respectively. For overt and subclinical hypothyroidism, the pooled prevalence was 0.02 (95% CI: 0.01-0.03, p = .001) and 0.20 (95% CI: 0.12-0.29, p = .001), respectively. CONCLUSIONS: On average, approximately half of patients with hypothyroidism are only treated to target euthyroidism. In real-world practice, a significant number of patients are over-treated or under-treated, leading to adverse healthcare outcomes. It is imperative that more effective thyroid monitoring strategies be implemented, with an emphasis on primary care thyroid function monitoring, to minimise inappropriate thyroid replacement treatments and optimise healthcare outcomes at a population level.

Local arterial stiffness measured by ultrafast ultrasound imaging in childhood cancer survivors treated with anthracyclines.

Background: There is conflicting literature regarding the long-term effect of anthracycline treatment on arterial stiffness. This study assessed local arterial stiffness using ultrafast ultrasound imaging (UUI) in anthracycline treated childhood cancer survivors, at rest and during exercise. Methods: 20 childhood cancer survivors (mean age 21.02 ± 9.45 years) treated with anthracyclines (mean cumulative dose 200.7 ± 126.80 mg/m2) and 21 healthy controls (mean age 26.00 ± 8.91 years) were included. Participants completed a demographic survey, fasting bloodwork for cardiovascular biomarkers, and performed a submaximal exercise test on a semi-supine bicycle. Pulse wave velocity (PWV) was measured in the left common carotid artery by direct pulse wave imaging using UUI at rest and submaximal exercise. Both PWV at the systolic foot (PWV-SF) and dicrotic notch (PWV-DN) were measured. Central (carotid-femoral) PWV was obtained by applanation tonometry. Carotid measurements were taken by conventional ultrasound. Measures were compared using two-tailed Students t-test or Chi-squared test, as appropriate. Results: There was no statistically significant difference (p > 0.05) between childhood cancer survivors and healthy controls in demographic parameters (age, sex, weight, height, BMI), blood biomarkers (total cholesterol, triglycerides, LDL-c, HDL-c, hs-CRP, fasting glucose, insulin, Hb A1c), cardiovascular parameters (intima media thickness, systolic and diastolic blood pressure, heart rate, carotid diameters, distensibility) or PWV measured by UUI at rest or at exercise. There was also no difference in the cardiovascular adaptation between rest and exercise in the two groups (p > 0.05). Multivariate analysis revealed age (p = 0.024) and LDL-c (p = 0.019) to be significant correlates of PWV-SF in childhood cancer survivors, in line with previously published data. Conclusion: We did not identify a significant impact of anthracycline treatment in young survivors of childhood cancer on local arterial stiffness in the left common carotid artery as measured by UUI.

Imaging features of renal malperfusion in aortic dissection.

OBJECTIVES: Malperfusion syndrome accompanying aortic dissection is an independent predictor of death with in-hospital mortality rates >60%. Asymmetrically decreased renal enhancement on computed tomography angiography is often considered evidence of renal malperfusion. We investigated the associations between renal enhancement, baseline laboratory values and the diagnosis of renal malperfusion, as defined by invasive manometry, among patients with aortic dissection. METHODS: In this retrospective cohort study, we included all patients who were referred to our institution with acute dissection and suspected visceral malperfusion between 2010 and 2020. We determined asymmetric renal enhancement by visual assessment and quantitative density measurements of the renal cortex. We collected invasive renal artery pressures during invasive angiography at the aortic root and in the renal arteries. Logistic regression was performed to evaluate independent predictors of renal malperfusion. RESULTS: Among the 161 patients analysed, the majority of patients were male (78%) and had type A dissection (52%). Invasive angiography confirmed suspected renal malperfusion in 83% of patients. Global asymmetric renal enhancement was seen in 42% of patients who did not have renal malperfusion during invasive angiography. Asymmetrically decreased renal enhancement was 65% sensitive and 58% specific for renal malperfusion. Both global [odds ratio (OR) 4.43; 1.20-16.41, P = 0.03] and focal (OR 11.23; 1.12-112.90, P = 0.04) enhancement defects were independent predictors for renal malperfusion. CONCLUSIONS: In patients with aortic dissection, we found that differential enhancement of the kidney as seen on the computed tomography angiography is predictive, but not prescriptive for renal malperfusion. While detection of renal malperfusion is aided by computed tomography angiography, its diagnosis requires close monitoring and often invasive assessment.

Successful Intratracheal Treatment of Phage and Antibiotic Combination Therapy of a Multi-Drug Resistant Pseudomonas aeruginosa Murine Model.

BACKGROUND: Pseudomonas aeruginosa (PsA) is a common etiology of bacteria-mediated lower respiratory tract infections, including pneumonia, hospital acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP). Given the paucity of novel antibiotics in our foreseeable pipeline, developing novel non-antibiotic antimicrobial therapies saliently targeting drug resistant PsA isolates remains a priority. Lytic bacteriophages (or phages) have come under scrutiny as a potential antimicrobial for refractory bacterial infections. We evaluated intratracheally and intraperitoneally (IP) administered phage therapy (with/without meropenem) in an acute immunocompromised mouse model of multi-drug resistant (MDR) PsA pulmonary infection. The MDR P. aeruginosa respiratory disease model used in these studies was developed to investigate novel therapies that might have efficacy as either monotherapies or as combination therapy with meropenem. METHODS: We utilized eight-week-old, 18 g BALB/cJ female mice and an MDR strain of PsA (UNC-D). Mice were immunosuppressed with cyclophosphamide. We employed a three-phage cocktail targeting PsA (PaAH2ΦP (103), PaBAP5Φ2 (130), and PaΦ (134)), confirmed to exhibit in vitro suppression of the infecting isolate out to 45 h. Suppression was confirmed with phages acting in isolation and in combination with meropenem. RESULTS: IP administration of phage did not protect mice from death. A one-time delivery of phage directly to the lungs via a single intubation-mediated, intratracheal (IMIT) instillation protected mice from lethal infection. Protection was observed despite delaying therapy out to 6 h. Finally, we observed that, by slowing the progression of infection by treatment with a sub-efficacious dose of meropenem, we could protect the mice from lethal infection via IP phage administration coupled to meropenem, observing partial additive effects of phage-antibiotic combination therapy. CONCLUSIONS: A personalized phage cocktail administered via IMIT exhibits high therapeutic efficacy, despite delayed treatment of 6 h in a lethal MDR PsA pneumonia model. IP phage alone did not forestall mortality, but exhibited efficacy when combined with meropenem and IMIT-administered phage. These additive effects of combined IP phage and meropenem confirm that phage may indeed reach the lung bed via the systemic circulation and protect mice if the infection is not too acute. Therefore, adjunctive phage therapy with concerted attention to identifying optimal phage targeting of the infecting isolate in vitro may exhibit transformative potential for combating the specter of MDR bacterial infections. Phage should serve as an integral component of a four-pronged approach coupled with antibiotics, source control, and immune optimization.

Incidence and Risk Factors for Fatal Graft-versus-host Disease After Liver Transplantation.

BACKGROUND: Graft-versus-host disease (GVHD) after liver transplantation (LT) is a rare but serious complication. The aim of this study is to identify risk factors, including immunosuppressive regimens, for mortality due to GVHD (fatal GVHD). METHODS: Using data from the Organ Procurement and Transplantation Network and United Network for Organ Sharing registry, 77 416 adult patients who underwent LT between 2003 and 2018 were assessed. Risk factors for fatal GVHD were analyzed by focusing on induction and maintenance immunosuppression regimens. RESULTS: The incidence of fatal GVHD was 0.2% (121 of 77 416), of whom 105 (87%) died within 180 d and 13 (11%) died between 181 d and 1 y. Median survival after LT was 68.0 (49.5-125.5) d. Recipient age minus donor age >20 y (hazard ratio [HR], 2.57; P < 0.001) and basiliximab induction (HR, 1.69; P = 0.018) were independent risk factors for fatal GVHD. Maintenance therapy with mycophenolate mofetil (MMF) was associated with a decrease in fatal GVHD (HR, 0.51; P = 0.001). In an increased risk cohort of patients with recipient-donor age discrepancy >20 y, MMF use was associated with a 50% decline in fatal GVHD (HR, 0.50; P < 0.001). CONCLUSIONS: Recipient age minus donor age >20 y remains a significant risk factor for fatal GVHD. The risk of fatal GVHD significantly increases in association with basiliximab induction and decreases with MMF maintenance. These associations were pronounced in patients with recipient minus donor age >20 y. These results emphasize the importance of donor age and individualized immunosuppression regimens on the risk of fatal GVHD.

High prevalence of early arch reobstruction after arch repair in patients with anomalous right subclavian artery.

OBJECTIVES: Having an anomalous right subclavian artery has been quoted to be a risk factor for early and late adverse events. We wanted to determine the rate of adverse outcomes in patients who have undergone arch repair with an associated anomalous right subclavian artery. METHODS: The follow-up of 76 patients, with an anomalous right subclavian artery, who underwent arch repair at a single institution for various indications between 1981 and 2017 was reviewed. RESULTS: There were 12 patient deaths. Twenty-three patients required an aortic arch reintervention (17 surgeries, 2 of which were indicated for bronchial obstruction). At last follow-up, 8 of 54 surviving patients (15%) had arch reobstruction (peak gradient >25 mmHg or reintervention). Freedom from aortic arch obstruction at 10 and 15 years was 51% [95% confidence interval (CI) 36-65%] and 35% (95% CI 19-51%), respectively. Neither the complete resection of the adjacent ridge nor the detachment and reimplantation of the anomalous subclavian vessel seemed to have an impact on the rate of reobstruction [hazard ratio (HR) 1.6, 95% CI 0.77-3.5; P = 0.2 and HR 0.61, 95% CI 0.083-4.5; P = 0.6, respectively]. CONCLUSIONS: Patients with an anomalous right subclavian artery are at risk of arch reobstruction necessitating reintervention but long-term follow-up was unable to demonstrate the mechanism of this obstruction in patients with this anomaly.

Systematic preoperative CT scan is associated with reduced risk of stroke in minimally invasive mitral valve surgery: A meta-analysis.

BACKGROUND: Minimally invasive mitral valve surgery (MIMVS) is performed with increasing frequency. However, patients undergoing MIMVS might be at increased risk of perioperative stroke, mainly due to retrograde aortic embolization during femoral cardio-pulmonary bypass. Pre-operative computed tomography (CT) screening allows visualization of the aorta and femoro-iliac vessels and individualization of the surgical approach. In this meta-analysis, we aim to determine if systematic pre-operative CT screening is associated with decreased incidence of post-operative stroke and other complications following MIMVS. METHODS: A comprehensive review was performed in PubMed (inception-May 2018). Eligible studies included those which reported on MIMVS (mini-thoracotomy, port access or robotic approach) with retrograde arterial perfusion. Studies were separated into two subgroups: systematic pre-operative CT screening (CT-group) and no CT screening (Non-CT). Pooled event rates (PER) for operative mortality, post-operative stroke, perioperative myocardial infarction (MI), and new onset renal failure requiring dialysis were estimated and inter-group comparisons were performed. RESULTS: Data from 57 studies (13,731 patients) were analyzed (19 CT-group, 38 Non-CT). PER for post-operative stroke was 2.0% with a statistically significant difference between the groups (CT-group: 1.5% versus Non-CT: 2.2%, P = 0.03). PER for new dialysis was 1.9%, significantly lower in the CT-group (0.8% versus 2.3% in the Non-CT group, P = 0.02). PER for operative mortality was 1.4% with a trend towards better outcomes in the CT-group (0.8% versus 1.6% in the Non-CT group, P = 0.05). CONCLUSIONS: Systematic pre-operative CT screening is associated with lower risk of post-operative stroke and need for dialysis and a trend toward lower operative mortality after MIMVS.

Development and Use of Personalized Bacteriophage-Based Therapeutic Cocktails To Treat a Patient with a Disseminated Resistant Acinetobacter baumannii Infection.

Widespread antibiotic use in clinical medicine and the livestock industry has contributed to the global spread of multidrug-resistant (MDR) bacterial pathogens, including Acinetobacter baumannii We report on a method used to produce a personalized bacteriophage-based therapeutic treatment for a 68-year-old diabetic patient with necrotizing pancreatitis complicated by an MDR A. baumannii infection. Despite multiple antibiotic courses and efforts at percutaneous drainage of a pancreatic pseudocyst, the patient deteriorated over a 4-month period. In the absence of effective antibiotics, two laboratories identified nine different bacteriophages with lytic activity for an A. baumannii isolate from the patient. Administration of these bacteriophages intravenously and percutaneously into the abscess cavities was associated with reversal of the patient's downward clinical trajectory, clearance of the A. baumannii infection, and a return to health. The outcome of this case suggests that the methods described here for the production of bacteriophage therapeutics could be applied to similar cases and that more concerted efforts to investigate the use of therapeutic bacteriophages for MDR bacterial infections are warranted.

Innominate artery cannulation for proximal aortic surgery: outcomes and neurological events in 263 patients.

OBJECTIVES: To determine whether innominate artery cannulation is the ideal perfusion strategy for delivering antegrade cerebral perfusion (ACP) during surgery on the proximal ascending aorta and transverse aortic arch. METHODS: A total of 263 patients underwent innominate artery cannulation with a side graft for surgery on the proximal aorta. Operations performed were ascending and proximal arch replacement (n = 213, 81.0%), ascending and total arch replacement (n = 33, 12.6%) and ascending aortic replacement (n = 12, 4.6%). Concomitant or other procedures included aortic root replacement and repair (n = 113, 43.0%), aortic valve replacement or repair (n = 118, 44.9%), coronary artery bypass (n = 40, 15.2%), antegrade stent graft delivery to the proximal descending thoracic aorta for aneurysm or dissection (n = 28, 10.7%), mitral valve repair (n = 11, 4.2%), patent foramen ovale repair (n = 3, 1.1%) and tricuspid valve repair (n = 2, 0.8%). Twenty-seven patients (10.3%) presented with acute or subacute Type I aortic dissection, and 45 (17.1%) had a previous sternotomy. Median cardiopulmonary bypass (CPB), cardiac ischaemia and ACP times were 126.0 [95-163 interquartile range (IQR)], 91.0 (73-121 IQR) and 21.0 (16-32 IQR) min. Bilateral ACP was delivered in 235 patients (90.7%). RESULTS: The operative mortality rate was 4.9% (n = 13). Nine patients (3.4%) had postoperative stroke, which was permanent in 5 (1.9%) of them. Multivariate analysis associated risk of stroke or temporary neurological deficit with acute or subacute Type I aortic dissection (P = 0.028) and age (P = 0.015). Renal disease (P = 0.036) and CPB time (P = 0.011) were independent risk factors for operative mortality. Circulatory arrest time was identified as a risk factor for mortality (P = 0.038). CONCLUSIONS: Innominate artery cannulation can be performed safely and poses a low risk of neurological events in procedures requiring hypothermic circulatory arrest. The technique for cannulating this artery should be part of the routine armamentarium of cardiac and aortic surgeons, and the innominate artery is among the preferred perfusion sites for delivering ACP.

Left ventricular aneurysm repair with use of a bovine pericardial patch.

Left ventricular aneurysm, which can impair systolic function, has a reported incidence of 10% to 35% in patients after myocardial infarction. In a 58-year-old woman who had a history of myocardial infarction, we excised a large left ventricular aneurysm and restored left ventricular geometry with use of a bovine pericardial patch. The aneurysm's characteristics and the patient's preoperative left ventricular ejection fraction of 0.25 had indicated surgical intervention. The patient had an uneventful postoperative course, and her left ventricular ejection fraction was 0.50 to 0.55 on the 4th postoperative day. This case illustrates the value of surgical treatment for patients who have a debilitating left ventricular aneurysm.

Endovascular repair of the ascending aorta: when and how to implement the current technology.

BACKGROUND: The purpose of our study was to examine when and how to implement the current endoluminal stent graft technology to treat ascending aortic disease. METHODS: During a 7-year period (March 2006 through July 2013), 7 consecutive patients (median age, 69 years; range, 61.5 to 80.5 years) with multiple comorbidities underwent endoluminal repair of the ascending aorta. Six had an ascending aortic pseudoaneurysm, and 1 had iatrogenic coarctation. The median number of prior sternotomies was 2 (range, 1 to 4). RESULTS: Technical success was achieved in all but 1 patient, with 1 death (14.3%) at 30 days. The endoluminal technology used included the Gore TAG (W.L. Gore and Associates, Flagstaff, AZ) thoracic graft (including the new C-TAG) in 6 patients, the Talent stent graft (Medtronic, Santa Rosa, CA) in 1, an Excluder cuff (W.L. Gore) in 2, and an Amplatzer occluder (AGA Medical Corp, Plymouth, MN) in 1. More than 1 stent was placed in 4 patients. Three patients required innominate artery stenting, and 1 required additional left common carotid artery stenting. One patient (14.3%) required intraoperative conversion to open surgical repair. Median follow-up was 14.4 months (interquartile [25th to 75th percentile] range, 5.5 to 22.6 months) with 66.6% overall survival. No aortic-related death was reported during the follow-up period. CONCLUSIONS: Stent grafting of the ascending aorta is feasible but limited and is reserved for high-risk individuals. Technical expertise is essential, and follow-up is mandatory. Technical points, tips, and challenges of the current endovascular technology to effectively treat the ascending aorta are described.

The effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on fuel stores and ion balance in a non-target fish, the rainbow trout (Oncorhynchus mykiss).

The pesticide 3-trifluoromethyl-4-nitrophenol (TFM) is used to control sea lamprey (Petromyzon marinus) populations in the Great Lakes through its application to nursery streams containing larval sea lampreys. TFM uncouples oxidative phosphorylation, impairing mitochondrial ATP production in sea lampreys and rainbow trout (Oncorhynchus mykiss). However, little else is known about its sub-lethal effects on non-target aquatic species. The present study tested the hypotheses that TFM exposure in hard water leads to (i) marked depletion of energy stores in metabolically active tissues (brain, muscle, kidney, liver) and (ii) disruption of active ion transport across the gill, adversely affecting electrolyte homeostasis in trout. Exposure of trout to 11.0mgl(-1) TFM (12-h LC50) led to increases in muscle TFM and TFM-glucuronide concentrations, peaking at 9h and 12h, respectively. Muscle and brain glycogen was reduced by 50%, while kidney and muscle lactate increased with TFM exposure. Kidney ATP and phosphocreatine decreased by 50% and 70%, respectively. TFM exposure caused no changes in whole body ion (Na(+), Cl(-), Ca(2+), K(+)) concentrations, gill Na(+)/K(+) ATPase activity, or unidirectional Na(+) movements across the gills. We conclude that TFM causes a mismatch between ATP supply and demand in trout, leading to increased reliance on glycolysis, but it does not have physiologically relevant effects on ion balance in hard water.

Alternative medicine techniques have non-linear effects on radiation response and can alter the expression of radiation induced bystander effects.

Many so-called "alternative medicine" techniques such as Reiki and acupuncture produce very good outcomes for intractable pain and other chronic illnesses but the efficacy is often dismissed as being psychosomatic. However a plausible mechanism does exist i.e. that the treatments alter the electromagnetic fields in living organisms and thereby prevent or reduce activity of neurons which lead to the pain. Low doses of ionising radiation have similar effects on electromagnetic fields and are known to induce signaling cascades in tissues due to ion gradients. To test this hypothesis cell cultures were exposed to Reiki - like and to acupuncture - like treatments, both performed by qualified practitioners. The cells were exposed either before or after the treatment to x-rays and were monitored for production of direct damage or bystander signals. The data suggest that the alternative techniques altered the response of cells to direct irradiation and altered bystander signal mechanisms. We conclude that alternative medicine techniques involving electromagnetic perturbations may modify the response of cells to ionizing radiation. In addition to the obvious implications for mechanistic studies of low dose effects, this could provide a novel target to exploit in radiation protection and in optimizing therapeutic gain during radiotherapy.

Multiple cutaneous granular cell tumors: case report of a 19-year-old African American female.

BACKGROUND AND OBJECTIVE: This is a somewhat rare case of a 19-year-old African American female with multiple cutaneous granular cell tumors. Granular cell tumors are of neural origin, except in rare cases, and are considered benign, with a low incidence of malignancy. The clinical presentation varies greatly, but these tumors are most commonly painful and slow growing, with two-thirds occurring on the head and neck. Patients are most commonly in their second to fourth decades of life, two-thirds are black, and two-thirds are women. Granular cell tumors are diagnosed by the characteristic pathologic findings of polygonal cells with eosinophilic granular cytoplasm. CONCLUSION: These tumors are most commonly singular but can be multiple in 10 to 15% of patients. Older patient age, rapid growth or enlargement, and a history of local recurrence should raise concern for malignant behavior. The distribution and family history in this case are suggestive of possible mosaicism.

Erythropoietin receptor signal transduction requires protein geranylgeranylation.

Erythropoietin (Epo) acts through the erythropoietin receptor, a member of the type-1 cytokine receptor family, to influence survival, proliferation, and differentiation of erythroid progenitors. Epo stimulation of factor-dependent 32D cells results in phosphorylation of many proteins, including Janus kinase (Jak) 2, signal transducer and activator of transcription (Stat) 5, and extracellular signal-regulated kinase (Erk). Some of Epo-activated signaling proteins require isoprenylation, either farnesylation or geranylgeranylation, for post-translational modification. In this study, we sought to characterize the interplay between protein isoprenylation and Epo signal transduction. Using two different Epo-responsive cell lines, we found that depletion of mevalonate and its isoprenoid derivatives using the 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor lovastatin impairs Epo signaling as assessed by phosphorylation of cellular substrates and inhibition of apoptosis. Interestingly, the effect of mevalonate depletion was prevented by adding back geranylgeranyl pyrophosphate but not farnesyl pyrophosphate. Furthermore, selective inhibition of protein geranylgeranylation mimicked the effect of lovastatin, whereas selective inhibition of farnesylation had no effect. These results indicate that protein geranylgeranylation and not farnesylation is important for proper Epo signal transduction.

Prolactin and heregulin override DNA damage-induced growth arrest and promote phosphatidylinositol-3 kinase-dependent proliferation in breast cancer cells.

Heregulin (HRG), a ligand of ErbB receptor tyrosine kinases, is a potent mitogenic factor for breast cancer cells. Prolactin (PRL) has also been reported to regulate proliferation in breast cancer cells through its receptor, a member of the type I cytokine receptor family. Cytokine receptors are potent mitogens in hematopoietic cells, where they also override DNA damage-induced growth arrest checkpoints through activation of a phosphatidylinositol-3 kinase (PI3K) signaling pathway. In this study, we assessed the effect of gamma-irradiation on the mitogenic activity of HRG and PRL in breast cancer cells. HRG and PRL enhanced the proliferation of non-irradiated breast cancer cell lines in association with their ability to activate PI3K signaling pathways. Both growth factors also overrode irradiation-induced growth arrest in T47D cells, which resulted in decreased viability after irradiation. An inhibitor of PI3K, LY294002, abrogated growth factor-induced proliferation and the activity of cell cycle-dependent kinases in non-irradiated and irradiated cells. Thus, growth factors acting through distinct receptor families share a similar PI3K-dependent ability to promote proliferation and override DNA damage-induced growth arrest in breast cancer cells. These observations also suggest that selective activation of PI3K-dependent signaling can enhance radiosensitivity in breast cancer cells.

Cytokine-induced phosphoinositide 3-kinase activity promotes Cdk2 activation in factor-dependent hematopoietic cells.

Cytokine growth factors regulate the proliferation of hematopoietic cells through activation of several distinct signaling pathways. We have assessed the contribution of phosphoinositide 3-kinase (PI3K) pathways to erythropoietin (Epo) and interleukin (IL)-3-induced proliferation of factor-dependent hematopoietic cells. Lack of cytokine-induced PI3K activation caused by receptor mutation or treatment with a specific inhibitor (LY294002) did not prevent proliferation but resulted in an increase in the G1 phase content and doubling time of cell cultures. The reduced proliferation of cells lacking cytokine-induced PI3K activity could be partially restored by overexpressing constitutively active Akt. Inhibition of PI3K activity decreased the proportion of cytokine-treated cells entering S phase and was associated with a significant reduction in cytokine-induced phosphorylation and activation of Cdk2. By contrast, Cdk4 activity and p27(Kip1) expression were not significantly altered by inhibition of PI3K. Together, these observations identify a mechanism through which cytokine-activated PI3K contributes to G1 to S phase progression in factor-dependent hematopoietic cells by enhancing the phosphorylation and activation of Cdk2.

Cytokine activation of phosphoinositide 3-kinase sensitizes hematopoietic cells to cisplatin-induced death.

Cytokine growth factors regulate the normal proliferation of hematopoietic cells but can also override irradiation-induced growth arrest checkpoints through activation of a phosphoinositide 3-kinase (PI3K) signaling pathway. In the present study, we assessed the effect that erythropoietin and interleukin-3 have on cisplatin-treated hematopoietic cells. When cultured in the presence of cytokine, cisplatin-treated 32D cells transiently accumulated in a G(2)-M phase arrest and ultimately died by a nonapoptotic mechanism. By comparison, reduction of cytokine-induced PI3K activity, either through cytokine receptor mutation or direct inhibition with LY294002, caused cisplatin-treated cells to enter a biphasic G(1) and G(2)-M arrest. The arrest of these cells coincided with an absence of cyclin-dependent kinase (Cdk)1 and Cdk2 activity and significantly reduced cell death during cisplatin treatment. Indeed, LY294002 treatment during cisplatin exposure allowed the recovery of a viable, proliferating cell population after removal of cisplatin. In contrast, Cdks remained active in the G(2)-M-arrested population of cisplatin-treated cells with continuous cytokine activation of PI3K, and even transient exposure to cisplatin resulted in death of the entire population. These data suggest that cytokine activation of PI3K signaling pathways overrides cisplatin-induced growth arrest checkpoints, thereby sensitizing hematopoietic cells to DNA damage-induced death.