Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Return to Play Following Achilles Tendon Rupture in NFL Players Based on Position

BACKGROUND

The purpose of this study was to determine the return-to-play (RTP) rate and postinjury performance after Achilles tendon (AT) ruptures in National Football League (NFL) skill position players.

METHODS

The study included NFL skill positions with an AT rupture between the 2009-2010 and 2015-2016 seasons. Performance data were collected and compared against a matched control group. RTP was defined as playing in at least 1 game after repair.

RESULTS

RTP rate was 57% for the study cohort. The tight ends (TEs) had the highest RTP rate at 71% while the wide receivers (WRs) had the lowest RTP rate at 38%. Compared with the control group, WRs with successful RTP had significantly less receptions per game (P = .01). For defensive players with RTP there were significant decreases in postrepair performance in tackles, passes defended, and fumbles forced/recovered compared with the control group.

CONCLUSION

A total of 57% of players achieved RTP with WRs and running backs (RBs) having the lowest RTP rates and TEs and linebackers (LBs) having the highest RTP rates. RBs, defensive backs (DBs), and LBs with successful RTP had decreased performance in all categories. This updated information may be helpful for athletes, physicians, scouts, and coaches in evaluating players with a history of AT rupture.

LEVELS OF EVIDENCE

Analytic, level 3, retrospective cohort study, Epidemiologic study.

Effect of Fibular Malrotation on Tibiotalar Joint Contact Mechanics in a Weber B Ankle Fracture Model

BACKGROUND

In minimally displaced Weber B ankle fractures, the distal fibular fracture fragment can be externally rotated. This malrotation is difficult to detect on radiographs and, when left malreduced through nonoperative treatment, may contribute to altered joint mechanics, predisposing to posttraumatic osteoarthritis. This study evaluates the effects of fibular malrotation on tibiotalar joint contact mechanics.

METHODS

Six cadaveric ankles were tested using a materials testing system (MTS) machine. A tibiotalar joint sensor recorded contact area and pressure. Samples were tested in the intact, neutrally rotated, and malrotated state. Each trial applied a 686N axial load and a 147N Achilles tendon load in neutral position, 15° dorsiflexion, and 15° plantarflexion.

RESULTS

In the comparison of malrotated to intact ankles, peak contact pressure was found to be significantly greater at neutral flexion (intact 5.56 MPa ± 1.39, malrotated 7.21 MPa ± 1.07, P = .03), not significantly different in dorsiflexion, and significantly decreased in plantarflexion (intact 11.2 MPa ± 3.04, malrotated 9.01 MPa ± 1.84, P = .01). Significant differences in contact area were not found between conditions.

CONCLUSION

The findings suggest that fibular malrotation contributes to significant alterations in tibiotalar joint contact pressures, which may contribute to the development of posttraumatic osteoarthritis. When malrotation of the fibula is suspected on plain radiographs, a computer tomography (CT) scan should be obtained to evaluate its extent and further consideration should be given to surgical treatment.

LEVELS OF EVIDENCE

Level V: Bench testing.

Evaluation of estimated glomerular function (eGFR) versus creatinine clearance (CrCl) to predict acute kidney injury when using zoledronate for the treatment of osteoporosis

Zoledronate could be contributing to the development of acute kidney injury in a small number of patients. Since estimated glomerular function (eGFR) is simpler to obtain and at least as good a predictor as creatinine clearance (CrCl), it should be used in everyday practice.

INTRODUCTION

Zoledronate is widely used for the treatment of osteoporosis. A potential side effect is acute kidney injury (AKI). Advice from the UK Medicines and Healthcare products Regulatory Agency (MHRA) in 2019 stated that CrCl and not estimated glomerular filtration rate (eGFR) should be used and that treatment should not be given if CrCl < 35 ml/min. The objective of this study was to compare our current method of assessing renal function (eGFR) with the method proposed by the MHRA (CrCl) for predicting AKI after zoledronate infusions.

METHODS

The evaluation was performed at the Metabolic Bone Centre in Sheffield Teaching Hospitals, UK. Data on all the patients who had zoledronate from 1/09/2015 to 1/10/2020 were included.

RESULTS

Data on 4405 patients were retrieved (total number of infusions 7660). Creatinine in the 14 days post-infusion was available for a total of 969 infusions and AKI was observed within 14 days following 45 infusions (4.6%). One patient died due to pneumonia. One patient needed continued haemodialysis. Severe AKI (threefold in creatinine and/or eGFR < 15 ml/min/173 m²) was observed within 1 year following 24 infusions. If the MHRA recommendations had been followed, 996 infusions with baseline CrCl < 35 ml/min would not have been given. Of these, follow-up data on serum creatinine within 14 days were available for 142 infusions, showing AKI in only four (2.8%). Logistic regression showed that both CrCl and eGFR were significant factors in predicting AKI within 14 days, but that the current recommended cut-off of CrCl 35 ml/min had poor sensitivity.

CONCLUSION

Since eGFR is at least as good a predictor of AKI as CrCl, and permits the treatment of more patients at high fracture risk, we recommend that eGFR is used to determine renal function for zoledronate treatment. We suggest that the infusion is given over 30 min in patients with eGFR < 50 ml/min/1.73 m².

Research Productivity of Foot and Ankle Fellowship Faculty

BACKGROUND

Contribution to literature is critical for progress in the field of orthopaedics. No previous study has yet examined the academic productivity of foot and ankle surgery fellowship faculty.

PURPOSE

To evaluate the publishing productivity of foot and ankle fellowship faculty.

METHODS

Faculty and program characteristics of orthopaedic foot and ankle fellowship programs across the United States and Canada were collected from American Orthopaedic Foot and Ankle Society (AOFAS) and program websites. Faculty publication productivity measures, including publications, number of publications in specific journals, number of citations, and Hirsch index (h-index) were gathered using the Scopus database.

RESULTS

A total of 48 AOFAS foot and ankle surgery fellowship programs were identified with an associated 185 faculty members. The mean number of publications per faculty member was 44.9 (SD = 53.0; range = 0-323), with a mean h-index of 11.9 (SD = 10.6; range = 0-54). A total of 144 (77.8%) academic-affiliated faculty had a significantly greater number of publications (P < .01), total citations (P < .05), and publications in Foot and Ankle International (P < .05), Journal of Bone and Joint Surgery (P < .05), Clinical Orthopaedics and Related Research (P < .05), and Journal of the American Academy of Orthopaedic Surgeons (P < .05) compared to the 41 (22.2%) nonacademic faculty. There were no significant differences between measures of publication productivity between male and female faculty, except for maximum citations in a single article (67.1 vs 142.3; P < .05).

CONCLUSIONS

Academic-affiliated foot and ankle fellowship faculty have higher research productivity than nonacademic surgeons. The mean h-index of foot and ankle fellowship faculty was 11.9, which is lower than that reported in sports, joints, and spine fellowship faculty but higher than that reported for hand fellowship faculty.

LEVEL OF EVIDENCE

Level IV.

Biomechanics of periprosthetic femur fractures and early weightbearing

PURPOSE

The incidence of periprosthetic fractures is expected to rise increase by 4.6% every 10 years between 2015 and 2060. There are few large series examining optimal fixation constructs or the influence of early ambulation on outcome. The purpose of this narrative review is to investigate the published biomechanical considerations for periprosthetic fracture fixation, with specific consideration of early postoperative weightbearing.

METHODS

A literature review was performed to identify fracture incidences, etiology, and current trends in weightbearing after fixation. Benefits of early weightbearing, current constructs, and biomechanics are reviewed.

RESULTS

The limited data available support medical benefits and increased union rates with early mobilization. Optimal fixation constructs are not agreed upon, but mechanical studies suggest that dual implant constructs can support physiologic weightbearing loads.

CONCLUSION

Further clinical trials are required to investigate fracture union and hardware complications in dual implant construct.

Return to Play Rates in NFL Wide Receivers and Running Backs After ACL Reconstruction: An Updated Analysis

Background:

Anterior cruciate ligament (ACL) ruptures are potentially career-threatening injuries to National Football League (NFL) skill position players. A 2006 study showed a return-to-play (RTP) rate of 79% for NFL running backs (RBs) and wide receivers (WRs). Since then, a number of factors affecting RTP, including style of play as well as rules regarding hits to the head, have changed how defensive players tackle offensive ball carriers.

Purpose/Hypothesis:

To determine whether the RTP rate for RBs and WRs in the NFL has changed since data were collected in the 2000s. Additionally, we evaluated player performance before and after ACL reconstruction (ACLR). We hypothesized that there will be a lower RTP rate than previously reported as well as a decrease in performance statistics after ACLR.

Study Design:

Descriptive epidemiology study.

Methods:

Publicly available NFL injury reports between the 2009-2010 and 2015-2016 seasons were utilized for RBs and WRs who underwent ACLR. Successful RTP was indicated by playing in at least 1 NFL game after reconstruction. Position-specific performance statistics from before and after reconstruction were gathered for these players, and the RTP players were compared against the players who did not RTP (dnRTP group). Pre- and postinjury performance measures were also compared against a matched control group of NFL RBs and WRs who had not sustained an ACL injury.

Results:

Overall, 61.8% of players (64.5% of RBs, 60% of WRs) returned to play at a mean of 13.6 months. Prior to injury, the RTP group had played in significantly more career games and had significantly more rushes and receptions per game than the dnRTP group; however, there was no significant difference in performance after ACLR. The WR RTP group had significantly decreased performance in all measured categories when compared with the control group.

Conclusion:

Our study found a lower RTP rate in RBs and WRs than previous studies conducted in the early 2000s. WRs who achieved RTP had decreased performance when compared with noninjured controls.

Acute kidney injury: prevention, detection, and management. Summary of updated NICE guidance for adults receiving iodine-based contrast media

The National Institute for Health and Care Excellence (NICE) has recently updated the guideline for Acute kidney injury: prevention, detection and management (NG148), providing new recommendations on preventing acute kidney injury (AKI) in adults receiving intravenous iodine-based contrast media. The association between intravenous iodinated contrast media and AKI is controversial, particularly with widespread use of iso-osmolar agents. Associations between contrast media administration and AKI are largely based on observational studies, with inherent heterogeneity in patient populations, definitions applied, and timing of laboratory investigations. In an attempt to mitigate risk, kidney protection has typically been employed using intravenous volume expansion and/or oral acetylcysteine. Such interventions are in widespread use, despite lacking high-quality evidence of benefit. In the non-emergency setting, glomerular filtration rate (GFR) measurements should be obtained within the preceding 3 months before offering intravenous iodine-based contrast media. In the acute setting, adults should also have their risk of AKI assessed before offering intravenous iodine-based contrast media; however, this should not delay emergency imaging. Based on the evidence available from randomised controlled trials, the NICE committee recommends that oral hydration should be encouraged in adults at increased risk of AKI and that volume expansion with intravenous V fluids should only be considered for inpatients at particularly high risk.

Website evaluation for shoulder and elbow fellowships in the United States: an evaluation of accessibility and content

Hypothesis and/or Background

When examining the access and content related to shoulder and elbow fellowship websites, only 64% of programs had individual websites in a query performed 5 years earlier. The purpose of this study was to re-evaluate content about individual programs listed on the American Shoulder and Elbow Surgeons (ASES) website and on individual program websites and compare the results to prior data.

Methods

The ASES website was accessed to determine both the number of ASES-recognized shoulder and elbow fellowships and the number of direct links to fellowship program websites. A Google search was also performed to determine the ease of access to fellowship program websites. Each website was then evaluated for content in regard to their recruitment and educational program.

Results

The ASES website includes contact information and a brief description for 29 programs with 40 reported positions. When trying to identify links to program websites, there were functioning links to 6 programs (21%) and absent/nonfunctioning links for the remaining 23 (79%). Through a Google search, there were functioning links to 22 (76%) and absent/nonfunctioning links for 7 (24%) programs. All 29 program websites had faculty listing and program contact info whereas 28 (97%) had a description of their program. In terms of educational content, 17 (59%) included description of operative cases and 18 (62%) had descriptions of rotations/curriculum.

Discussion and/or Conclusion

Individual shoulder and elbow fellowship program websites provide varied content and accessibility. In the intervening 5 years, there has been minimal improvement in the accessibility of individual fellowship websites from the ASES website.

An Update on Foot and Ankle Fellowship Website Content and Accessibility

Background:

The content and accessibility of foot and ankle fellowship websites impact applicants and fellowship programs. This study aimed to evaluate the accessibility provided via the American Orthopaedic Foot & Ankle Society (AOFAS) websites and individual websites.

Methods:

The AOFAS website was used to identify existing foot and ankle fellowship programs. The database information was reviewed for links to fellowship program websites, which was corroborated through a Google search for accessibility. Information from fellowship program websites and the AOFAS was analyzed for the presence of recruitment and educational content, and this analysis was compared to previously reported metrics.

Results:

Forty-eight orthopedic foot and ankle fellowship programs were identified. The AOFAS database featured direct links to 19 (40%) fellowship websites with the Google search providing direct links to 35 (73%) websites. Foot and ankle fellowship information markedly improved in domains of Salary/Benefits (+233%), Rotations/Curriculum (+199%), and Faculty Listing (+67%), but there was a reduction in available content in the domains of Operative Experience (–79%), Office/Clinic information (–78%), and Didactics (–39%) compared with the lone existing study.

Conclusion:

There continues to be variability between foot and ankle fellowship websites and the AOFAS website regarding program content and descriptions. Some information is more readily available, but other domains have less information now than in previously reported research.

Early musculoskeletal classroom education confers little advantage to medical student knowledge and competency in the absence of clinical experiences: a retrospective comparison study

BACKGROUND

Deficiencies in medical student knowledge in musculoskeletal medicine have been well documented. To address these deficiencies, numerous curricular changes at our institution were instituted. The objective of this study was to determine whether medical students in their preclinical years benefit from early exposure to musculoskeletal medicine when compared to students exposed to musculoskeletal medicine just prior to completion of their preclinical curriculum.

METHODS

United States Medical Licensing Examination (USMLE) Step 1 and 2 scores were compared for periods of time before and after institution of the new curriculum. Scores on the previously validated 24-question short answer survey from Freedman and Bernstein were also compared over these same periods of time between these two groups and to established standards for competency, using a student's two-tailed unpaired t-test for significance. Entering Medical College Admission Test (MCAT) scores were used to compare baseline preparation of students.

RESULTS

Overall USMLE scores as well as scores on the USMLE subtest on Musculoskeletal, Skin and Connective Tissue Disease showed no improvement when scores were compared between the two groups of students. There was a statistically significant lower performance on the Freedman and Bernstein knowledge assessment exam for students in the new pre-clinical curriculum as compared to those introduced under the old model, considering both musculoskeletal knowledge (p < 0.001) and proficiency (p < 0.01), though the response rate on the recent survey was low (112/986 or 11%). Spine remained the least understood sub-topic, while a dedicated course in rheumatology likely contributed to increased student knowledge in that area. Additional exposure to musculoskeletal topics during the clinical years increased student knowledge. There was no difference between groups when comparing entering MCAT scores.

CONCLUSIONS

Classroom curricular changes, including moving the introductory musculoskeletal course to the first year, intended to optimize musculoskeletal medicine education in the pre-clinical years of medical school did not appear to improve student musculoskeletal knowledge at any year of training. Further efforts to improve the education of medical students in musculoskeletal medicine should be directed towards providing more clinical experiences with patients having musculoskeletal concerns. This was a retrospective comparative study, level III evidence.

Pharmacological Management of Secondary Hyperparathyroidism in Patients with Chronic Kidney Disease

Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease (CKD) and is part of the CKD-mineral bone disorder (CKD-MBD). SHPT is associated with increased risk of fracture and mortality; thus, SHPT control is recommended as kidney function declines. Effective SHPT management becomes more difficult once skeletal and cardiovascular adverse effects associated with severe SHPT have become established. However, interventional studies to lower parathyroid hormone (PTH) have so far shown inconsistent results in improving patient-centred outcomes such as mortality, cardiovascular events and fracture. Pharmacological treatment effect on PTH level is also inconsistent between pre-dialysis CKD and dialysis patients, which adds to the complexity of SHPT management. This review aims to give an overview on the pathophysiology, pharmacological and non-pharmacological treatment for SHPT in CKD including some of the limitations of current therapeutic options.

Service and its association with matching into a primary care residency

BACKGROUND AND OBJECTIVES

There is a shortfall in the primary care workforce, and an effort is needed in learning more about what motivates students to work as generalists. There is enthusiasm about service as a potential motivator. The objective is to determine whether there is an association between high participation in service and selection of a primary care residency.

METHODS

This is a retrospective cohort analysis. The service award was used to delineate two groups, recipients and non-recipients, with the recipients considered high service participators. This was associated with residency match data using test of proportions to examine relationships between service and selection of a primary care residency and other secondary factors.

RESULTS

Of award recipients, 57.3% matched in primary care, compared to 52.8%, though this did not reach statistical significance. Service was linked with induction into Alpha Omega Alpha honor society (23.3% versus 14.6%) and induction into the Gold Humanism Honor Society (22.6%. versus 10.4%), with statistical significance.

CONCLUSION

This was an unsuccessful attempt to find a link between service and a primary care career choice, though there is a trend in the direction. The association with induction into the humanism honor society suggests that service is linked with development and/or retention of positively viewed qualities in medical students.

Opsismodysplasia: Phosphate Wasting Osteodystrophy Responds to Bisphosphonate Therapy

We present two siblings affected with opsismodysplasia (OPS), a rare skeletal dysplasia caused by mutations in the inositol polyphosphate phosphatase-like 1 gene. The skeletal findings include short stature with postnatal onset micromelia, marked platyspondyly, squared metacarpals, delayed skeletal ossification, metaphyseal cupping, and postnatal micromelia. Respiratory compromise, delayed ambulation, and progressive lower extremity deformities are described. The severity of findings is variable. Renal phosphate wasting is associated with severe bone demineralization and a more severe phenotype. This report represents the first described cases of opsismodysplasia treated with intravenous bisphosphonate (pamidronate). Surgical management for lower extremity deformities associated with OPS is also reviewed.

LEVEL OF EVIDENCE

IV Case series.

Single-staged treatment using a standardized protocol results in functional motion in the majority of patients with a terrible triad elbow injury

BACKGROUND

Terrible triad injuries of the elbow, defined as elbow dislocation with associated fractures to the radial head and coronoid, are associated with stiffness, pain, and loss of motion. Studies to date have consisted of small sample sizes and used heterogeneous surgical techniques, which render comparisons difficult and unreliable.

QUESTIONS/PURPOSES

In a group of patients treated under a standard surgical protocol, we sought to determine the early dislocation rate, the range of motion in those not undergoing secondary procedures, the frequency and types of secondary surgical interventions required, the difference in motion between those undergoing secondary surgery and those who did not, and the frequency of heterotopic ossification and patient-reported stiffness.

METHODS

Patients underwent a surgical protocol that involved fixing the coronoid, fixing the radial head if possible, otherwise performing radial head arthroplasty, and repairing the lateral ligamentous structures. Patients were excluded if ipsilateral upper extremity fractures from the humerus to the distal forearm were present. Fifty-two patients had a minimum followup of 6 weeks and were included for the early dislocation rate, and 34 of these (65%) had a minimum of 6 months followup and were included for the rest of the data. Eighteen of the 52 (35%) were considered lost to followup because they were seen for less than 6 months postsurgically and were excluded from further analysis. Chart review was performed to determine the presence of early dislocation within the first 6 weeks after surgery, range of motion in patients not requiring a secondary procedure, the frequency and types of secondary procedures required, the range of motion before and after a secondary procedure if it was required, and postoperative stiffness. Postoperative radiographs were analyzed to determine the presence and severity of heterotopic ossification.

RESULTS

One of 52 patients sustained a dislocation within the first weeks of surgery (1.9%). Those not undergoing a secondary procedure were able to achieve a flexion arc of 110° and a supination-pronation arc of 148°. Nine of 34 patients (26%) underwent a secondary surgical procedure with stiffness, heterotopic ossification, and ulnar neuropathy being the most common surgical indications. Before secondary surgical procedures, patients had a flexion arc of 57° and a supination-pronation arc of 55°, which was less than those only requiring primary surgery alone (p < 0.001). After secondary surgery, patients were able to achieve a flexion arc of 96° and a supination-pronation arc of 124°, which was not different from those who did not undergo reoperation (p = 0.09 and p = 0.08, respectively). Twenty-eight of 34 patients demonstrated evidence of heterotopic ossification on radiographs, whereas 20 patients, including all nine undergoing secondary procedures, reported stiffness at the elbow.

CONCLUSIONS

Using a standardized surgical protocol, a low early dislocation rate was observed, although stiffness remains a challenge. Many patients who initially do not attain functional range of motion can usually attain this after secondary procedures aimed at removing the heterotopic ossification.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See guidelines for authors for a complete description of levels of evidence.

Seliciclib inhibits renal hypertrophy but not fibrosis in the rat following subtotal nephrectomy

BACKGROUND

5/6 subtotal nephrectomy (SNx) is a non-immune stimulus used to induce renal fibrosis. The ability of seliciclib, a cyclin-dependent kinase inhibitor, to reduce kidney hypertrophy and extracellular matrix (ECM) deposition has been examined in the SNx rat.

METHODS

Wistar rats were subjected to SNx under isoflurane anaesthesia. The acute effect of seliciclib 28 mg/kg (5 days) on compensatory renal growth (CRG), kidney protein and DNA was determined. In chronic studies albuminuria, hypertension and GFR were monitored. Ki67, apoptag and α-smooth muscle actin were determined by immunohistochemistry together with Masson's trichrome staining. The effect of a maximum non-hypotensive dose of seliciclib 28 mg/kg (8 weeks) was determined.

RESULTS

Acutely, the remnant kidney developed CRG. Seliciclib 28 mg/kg inhibited both CRG by 45% and increased kidney protein by 48% without affecting increased kidney DNA. Chronically, SNx rats developed albuminuria, hypertension, low GFR with increased tubulointerstitial cell proliferation, apoptosis, myofibroblast accumulation and enhanced ECM deposition. Seliciclib 28 mg/kg (8 weeks) had no effect on either renal function or renal pathology. Plasma concentrations of seliciclib exceeded 5 µM throughout the study.

CONCLUSIONS

Despite inhibition of early renal hypertrophy, a maximum non-hypotensive dose of seliciclib 28 mg/kg had no impact on the progression of kidney fibrosis in the SNx rat.

PI3K/mTOR inhibition upregulates NOTCH-MYC signalling leading to an impaired cytotoxic response

PI3K, mTOR and NOTCH pathways are frequently dysregulated in T-cell acute lymphoblastic leukaemia (T-ALL). Blockade of PI3K and mTOR with the dual inhibitor PI-103 decreased proliferation in all 15 T-ALL cell lines tested, inducing cell death in three. Combined PI3K/mTOR/NOTCH inhibition (with a γ-secretase inhibitor (GSI)) led to enhanced cell-cycle arrest and to subsequent cell death in 7/11 remaining NOTCH mutant cell lines. Commitment to cell death occurred within 48-72 h and was maximal when PI3K, mTOR and NOTCH activities were inhibited. PI-103 addition led to upregulation of c-MYC, which was blocked by coincubation with a GSI, indicating that PI3K/mTOR inhibition resulted in activation of the NOTCH-MYC pathway. Microarray studies showed a global increase in NOTCH target gene expression upon PI3K/mTOR inhibition. NOTCH-MYC-induced resistance to PI3K/mTOR inhibition was supported by synergistic cell death induction by PI-103 and a small molecule c-MYC inhibitor, and by reduction of the cytotoxic effect of PI-103+GSI by c-MYC overexpression. These results show that drugs targeting PI3K/mTOR can upregulate NOTCH-MYC activity, have implications for the use of PI3K inhibitors for the treatment of other malignancies with activated NOTCH, and provide a rational basis for the use of drug combinations that target both the pathways.

Patterns of differentiated thyroid cancer in Baluchistan Province of Pakistan: some initial observations

The incidence of thyroid cancer is increasing in several countries. The main objective of this retrospective study was to find and describe province-specific estimates of incidence in males and females by age groups for differentiated thyroid cancer (DTC). This study reports on 87 cases of DTC from Baluchistan province of Pakistan treated with post operative radioiodine at the Center for Nuclear Medicine and Radiotherapy (CENAR) Quetta from January 2003 to December 2009. The patient data has been collected from CENAR Quetta. Patients with DTC were confirmed by clinical examination, thyroid scintigraphy (Thyroid scan), blood tests (T3, T4, TSH) and histopathalogy tests and then treated with radioiodine. The Median age of the patients was 35.5 years (Range 12-70 years). The final histological diagnosis was papillary carcinoma in 71 (81.6 %) cases, follicular carcinoma in 6 (6.9%) cases while 10 (11.5%) cases presented with mixed papillary and follicular carcinoma. About 53 % cases were found in females with age 21-40 years. No strike predominance was observed in any age group for males. Four patients presented with recurrence while six patients showed metastasis in cervical lymph nodes. The small annual incidence did not follow any definite pattern. DTC has a small incidence in Baluchistan due to lack of education and health care facilities. The incidence of DTC is higher in females when compared with males as per this study. This preliminary study will provide an insight to incidence of DTC, its treatment facilities and future planning strategies in Baluchistan, Pakistan.

Conservatively managed patients with stage 5 chronic kidney disease--outcomes from a single center experience

BACKGROUND

Limited survival data are available on chronic kidney disease stage 5 (CKD 5) patients who opt for conservative management rather than dialysis.

AIM

To measure survival in such patients and investigate potential factors predicting survival.

DESIGN

Retrospective survival analysis of a cohort of conservatively managed CKD 5 patients from a single center.

METHODS

Survival was measured in 69 conservatively managed patients from the time they were first known to have CKD 5. Comorbidities, residual renal function and other laboratory parameters (calcium, phosphate, parathyroid hormone, albumin and hemoglobin) and blood pressure were recorded.

RESULTS

Overall median patient survival from the time of first known CKD 5 was 21 months. Patients known to a nephrologist before reaching CKD 5 survived longer (median 32 months) than those presenting with CKD 5 (15 months, P = 0.025). Serum albumin >35 g/l was associated with greater survival, but other biochemical parameters, comorbidity grade and age did not predict survival.

CONCLUSION

These survival data provide useful information for nephrologists counseling CKD 5 patients considering whether to pursue dialysis or conservative management. Risk factors that correlate with survival in the dialysis population may not predict survival in conservatively managed CKD 5 patients.

The management of CKD: a look into the future

The increasing global prevalence of chronic kidney disease (CKD) and end-stage renal disease with the associated spiraling cost has profound public health and economic implications. This has made slowing the progression of CKD, a major health-care priority. CKD is invariably characterized by progressive kidney fibrosis and at present, treatment aiming to slow the progression of CKD is limited to aggressive blood pressure control, with few therapies targeting the fibrotic process itself. In this review, we explore the potential of experimental therapeutic strategies, based on preventing or reversing the pathophysiologic steps of kidney remodeling that lead to fibrosis.

The role of geranylgeranylated proteins in human mesangial cell proliferation

The Rho family of guanine 5'-triphosphatases (GTPases) play a key role in regulating cell proliferation, tubulointerstitial fibrosis, and glomerular hemodynamics. The post-translational prenylation of RhoGTPases by the addition of a geranylgeranyl moiety is critical for cellular localization and signaling activity. This study investigates the effects of (i) inhibiting geranylgeranylation (GG) in human mesangial cell (HMC) proliferation and apoptosis, using GGTI 298, a specific inhibitor of GG and (ii) lovastatin, an HMG-coacetyl A-reductase inhibitor, which depletes the availability of prenylation substrates. HMC proliferation was assessed using an assay of viable cell number and measuring bromodeoxyuridine (BrdU) incorporation. Hoechst 33342 staining was used to determine apoptosis. Extracellular signal-regulated protein kinase (Erk)1/2 and Akt activation were analysed by Western blotting. Rho activation was determined using the Rhotekin pull-down assay. Immunocytochemistry was performed to study the effects on the actin cytoskeleton and RhoA localization. GGTI 298 (10-20 muM) and lovastatin (5-10 muM) potently inhibited platelet-derived growth factor and serum-stimulated HMC proliferation and induced apoptosis. These effects of lovastatin were attenuated by co-incubation with geranylgeranylpyrophosphate. C3 exoenzyme, a clostridial toxin that specifically targets Rho also inhibited BrdU incorporation and promoted apoptosis. GGTI 298 increased cytosolic expression of RhoA, prevented RhoA activation, and inhibited the activation of Erk1/2 and the survival protein Akt. GGTI 298, lovastatin, and C3 exoenzyme inhibit HMC proliferation and promote apoptosis. Inhibiting GG increases cytosolic RhoA expression, disrupts the actin cytoskeleton, and inhibits RhoA activation. These results suggest that targeting geranylgeranylated proteins with statins or GGTI 298 is a promising therapeutic strategy in human mesangioproliferative renal disease.

A selective inhibitor of the p110delta isoform of PI 3-kinase inhibits AML cell proliferation and survival and increases the cytotoxic effects of VP16

Current therapy for acute myeloid leukaemia (AML) is suboptimal with a high incidence of relapse. There is strong evidence that constitutive phosphoinositide 3-kinase (PI3K) activity plays a significant role in the pathophysiology of AML. PI3K products are derived from the activity of a number of PI3K catalytic isoforms (class I, II and III) but the relative contribution of these enzymes in AML remains unknown. As non-isoform-selective inhibitors of PI3K such as LY294002 may produce unwanted toxicity to normal tissues, we have investigated the role of the leukocyte-restricted p110delta PI3K isoform in 14 cases of AML. p110delta was detected in all cases whereas the expression levels of the other class I PI3Ks varied more widely, and were often undetectable. The p110delta-selective compound IC87114 inhibited constitutive phosphorylation of the PI3K target Akt/PKB and reduced cell number to a mean of 66+/-5% (range 14-88%). In eight cases, the combination of IC87114 and VP16 (a topoisomerase II inhibitor) was synergistic in reducing viable cell number, and was associated with a reduction in constitutive NF-kappaB activity. IC87114 did not have direct adverse effects or enhance the activity of VP16 on the proliferation and survival of normal haemopoietic progenitors. Overall, our results identify the p110delta isoform as a potential therapeutic target in AML and support a clinical approach to use isoform-selective over broad-spectrum PI3K inhibitors.

Distinct functions for Ras GTPases in the control of proliferation and apoptosis in mouse and human mesangial cells

In previous work, we have demonstrated that Ras GTPases regulate proliferation in a range of human renal cells. The present work compares human and mouse mesangial cell (HMC and MMC) responses to specific knockdown of Ras genes with antisense oligonucleotides (AS-oligos), and examines the role of the p21 (cip1) and p27 (kip1) cyclin-dependent kinase inhibitors in these responses in mouse cells. HMC and MMC were lipofectin transfected with ras-targeted AS-oligo at 200-400 nM for 18 h followed by growth of cells in 20% serum for 18-72 h. Cell proliferation was assessed with an MTS assay and bromodeoxyuridine (BrdU) uptake. Apoptosis was quantified using nuclear stain with Hoechst 33342 dye. In MMC, Ha-ras AS-oligo caused an increase in apoptosis from <2% to 10-15% of cells after 18 h in serum (P<0.01). Control, Ki-ras and N-ras AS-oligos had minimal effects on apoptosis. BrdU uptake studies showed that BrdU+ve MMC were increased by 20-40% (P<0.05) after Ha-ras AS-oligo at 24 h; other ras AS-oligos were inactive. HMC number was reduced by 40-80% (P<0.01) at 48-72 h by both Ha-ras and Ki-ras AS-oligos. These actions were associated with reductions in BrdU+ve cells. In HMC, the ras AS-oligos did not induce apoptosis. p21(-,-) MMC showed exaggerated apoptotic responses to Ha-Ras AS-oligo. In mouse cells, Ha-Ras expression appears necessary to prevent apoptotic cell death; Ras expression does not appear necessary for cells to progress through the cell cycle. In human cells, Ras does not appear necessary to prevent apoptosis but Ha-Ras and Ki-Ras appear to be required for cell cycle progression.

PI3-kinase/Akt is constitutively active in primary acute myeloid leukaemia cells and regulates survival and chemoresistance via NF-kB, MAPkinase and p53 pathways

The phosphoinositide 3-kinase (PI3-kinase) signalling pathway plays a key role in the regulation of cell survival and proliferation. We show that the PI3-kinase/Akt pathway is constitutively active in primary acute myeloid leukaemia (AML) cells and that blockade by the selective inhibitor LY294002 reduces survival of the total blast population (mean 52%). The ERK/MAPK module is also constitutively active and treatment with the MAPKK inhibitor U0126 reduces cell survival by 22%. In 10 of 18 samples, PI3-kinase contributes to MAPK activation as incubation with LY294002 leads to a marked reduction in its phosphorylation. PI3-kinase inhibition reduces survival of the CD34+38- AML progenitor subset by 44%, whereas MAPKK inhibition has little effect. Reporter assays in primary AML cells show that blocking PI3-kinase leads to a marked reduction of constitutive NF-kappaB activity and promotes p53-mediated transcription. This is associated with a synergistic interaction between LY294002 and Ara-C. An inducible activated form of Akt protects normal myeloid cells from Ara-C and etoposide-mediated apoptosis. These results show that blocking PI3-kinase has direct antileukaemic effects and potentiates the response to conventional cytotoxics via a number of targets including NF-kappaB, p53 and MAPK. Inhibitors of PI3-kinase and Akt may be useful in the treatment of AML.

Growth factor withdrawal from primary human erythroid progenitors induces apoptosis through a pathway involving glycogen synthase kinase-3 and Bax

The prevention of apoptosis is a key function of growth factors in the regulation of erythropoiesis. This study examined the role of the constitutively active serine/threonine kinase glycogen synthase kinase-3 (GSK3), a target of the phosphoinositide-3-kinase (PI3K)/Akt pathway, in the regulation of apoptosis in primary human erythroid progenitors. GSK3 phosphorylation at its key regulatory residues S21 (alpha isoform) and S9 (beta isoform) was high in steady-state culture, disappeared on growth factor withdrawal, and returned in response to treatment of cells with either erythropoietin or stem cell factor. Phosphorylation correlated with a PI3K-dependent reduction of 25% to 30% in measured GSK3 activity. LY294002, a specific inhibitor of PI3K, induced apoptosis in growth factor-replete erythroid cells to a degree similar to growth factor deprivation, whereas the Mek1 inhibitor U0126 had no effect, implicating PI3K and not mitogen-activated protein kinase in survival signaling. Growth factor-deprived erythroblasts, which undergo apoptosis rapidly, were protected from apoptosis by both lithium chloride, a GSK3 selective inhibitor, and inhibition of caspase activity. However, the clonogenic potential of single cells, which more accurately reflects cell survival, was maintained by lithium chloride, but not by caspase inhibition. Furthermore, lithium chloride, but not caspase inhibition, prevented the appearance of the conformational form of Bax associated with apoptosis induction. In summary, GSK3 activity is suppressed by erythropoietin and stem cell factor in human erythroid progenitor cells, and increased GSK3 activity, brought about by growth factor withdrawal, may regulate commitment to cell death through a caspase-independent pathway that results in a conformational change in Bax.

The PI3 kinase, p38 SAP kinase, and NF-kappaB signal transduction pathways are involved in the survival and maturation of lipopolysaccharide-stimulated human monocyte-derived dendritic cells

As a dendritic cell (DC) matures, it becomes more potent as an antigen-presenting cell. This functional change is accompanied by a change in DC immunophenotype. The signal transduction events underlying this process are poorly characterized. In this study, we have investigated the signal transduction pathways involved in the lipopolysaccharide (LPS)-induced maturation of human monocyte-derived DCs (MoDCs) in vitro. We show that exposure of immature MoDCs to LPS activates the p38 stress-activated protein kinase (p38SAPK), extracellular signal-regulated protein kinase (ERK), phosphoinositide 3-OH kinase (PI3 kinase)/Akt, and nuclear factor (NF)-kappaB pathways. Studies using inhibitors demonstrate that PI3 kinase/Akt but not the other pathways are important in maintaining survival of LPS-stimulated MoDCs. Inhibiting p38SAPK prevented activation of the transcription factors ATF-2 and CREB and significantly reduced the LPS-induced up-regulation of CD80, CD83, and CD86, but did not have any significant effect on the LPS-induced changes in macropinocytosis or HLA-DR, CD40, and CD1a expression. Inhibiting the NF-kappaB pathway significantly reduced the LPS-induced up-regulation of HLA-DR as well as CD80, CD83, and CD86. Inhibiting the p38SAPK and NF-kappaB pathways simultaneously had variable effects depending on the cell surface marker studied. It thus appears that different aspects of LPS-induced MoDC maturation are regulated by different and sometimes overlapping pathways.

Prenylation inhibitors in renal disease

Members of the superfamily of Ras GTPase signalling proteins (monomeric G proteins) require post-translational carboxy-terminal prenylation to function. Prenylation is the covalent attachment of a hydrophobic prenyl group (either farnesyl or geranylgeranyl), which localises the GTPase to cell membranes. Ras proteins exert substantial control on cell proliferation and gene-transcription events, and prenylation inhibitors are now included in clinical trials for cancer. Many renal diseases are highly proliferative and are driven by a range of profibrotic cytokines. We hypothesise that inhibition of prenylation could be of substantial therapeutic benefit in such diseases, providing greater selectivity against abnormal cytokine-driven proliferation and fibrogenesis than current treatments available to nephrologists.

Resistance to the cytotoxic effects of tumor necrosis factor alpha can be overcome by inhibition of a FADD/caspase-dependent signaling pathway

Tumor necrosis factor (TNF) alpha initiates the activation of a pro-apoptotic pathway involving the recruitment of the death domain containing protein FADD and the subsequent activation of specific proteases (caspases). Many cells are resistant, however, to the cytotoxic effects of TNFalpha due to the concurrent activation of pro-survival pathways involving the transcription factor NFkappaB and TRAF2. Here we show that the TNFalpha-activated FADD/caspase pathway can also exert an unexpected pro-survival effect. Inhibition of this pathway in NIH3T3 fibroblasts or U937 leukemic cells by peptide caspase inhibitors or expression of dominant-negative FADD leads to rapid death following treatment with TNFalpha, whereas control cells are TNFalpha-resistant. FADD/caspase-inhibited cells die by a non-apoptotic mechanism caused by increased production of reactive oxygen species which precedes loss of the mitochondrial membrane potential. Cytotoxicity can be prevented by preincubation with antioxidants including reduced glutathione or by expression of a dominant-negative Rac GTP-binding protein. These results indicate that caspase activation in response to TNFalpha has anti-necrotic as well as pro-apoptotic effects and extend our understanding of the biological role of these proteases.

Caspase-mediated proteolysis and activation of protein kinase Cdelta plays a central role in neutrophil apoptosis

Neutrophils undergo constitutive apoptosis when aged ex vivo. Recent studies have indicated roles for Fas/CD95 and the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase system in this process. We have investigated the role of protein kinase C (PKC) in neutrophil death. We show that there is proteolysis and activation of the novel isoform PKCdelta in aged neutrophils and that this process is accelerated by the addition of an agonistic Fas antibody. PKCdelta proteolysis occurs before the onset of any detectable features of apoptosis and pharmacologic inhibition of this enzyme inhibits neutrophil apoptosis. PKCdelta cleavage and activation is dependent on caspase-8/FADD-like interleukin-1beta converting enzyme (FLICE)-mediated processing of caspase-3/CPP32. Neutrophil survival is prolonged by the addition of broad spectrum (BD.fmk) or caspase-8 targeted (zIETD.fmk) peptide caspase inhibitors. Inhibition of PKCdelta does not prevent apoptosis triggered by factor withdrawal in immature hematopoietic cells, including normal human CD34(+) progenitors indicating that within a given lineage, the mechanisms of apoptosis may be differentiation-stage-specific. Ex vivo aging of neutrophils leads to the increasing production of reactive oxygen species and this is attenuated in cells treated with either caspase or PKCdelta inhibitors. Proteolytically activated PKCdelta acts as a molecular link between the Fas/CD95 receptor and the NADPH-oxidase system and plays a central role in regulating the process of neutrophil apoptosis.

Stent placement for treatment of mesenteric artery stenoses or occlusions

PURPOSE

To evaluate stent placement in the treatment of mesenteric ischemia.

PATIENTS AND METHODS

Twelve patients (eight women, four men; mean age, 63 years) with chronic mesenteric ischemia underwent stent placement for stenoses or occlusions during a 5.5-year period. Nine patients with 10 stenoses (three celiac arteries, seven superior mesenteric arteries) and three patients with three chronic occlusions (two superior mesenteric arteries, one aortosuperior mesenteric artery bypass graft) were treated.

RESULTS

Initial technical success was achieved in 11 of the 12 patients (92%), including all three patients with chronic occlusions. There were no technical complications. There was one postprocedural death (<30 days) due to bowel ischemia and infarction, despite a technically successful procedure. Clinical follow-up was available in all 12 patients, with a mean follow-up of 15.7 months (range, 0-38.5 months). Primary and primary-assisted patency up to 18 months was 74% (standard error [SE], 13%) and 83% (SE, 11%), respectively. Secondary patency was 83% (SE, 11%) at 3 years. All three patients (100%) with chronic occlusions had relief of clinical signs and symptoms at a mean follow-up of 22 months (range, 13-38.5 months).

CONCLUSIONS

Stent placement is safe and clinically effective as an adjunctive therapy to angioplasty or as a primary method of treatment for chronic mesenteric ischemia in patients with focal visceral artery stenoses or occlusions.

Phosphoinositide 3-kinase induces scattering and tubulogenesis in epithelial cells through a novel pathway

Hepatocyte growth factor/scatter factor (HGF/SF) treatment of the Madin-Darby canine kidney epithelial cell line causes scattering of cells grown in monolayer culture and the formation of branching tubules by cells grown in collagen gels. HGF/SF causes prolonged activation of both the mitogen-activated protein (MAP) kinase extracellular signal-regulated kinase 2 (ERK2) and the phosphoinositide 3-OH kinase (PI 3-kinase) target protein kinase B (PKB)/Akt; inhibition of either the MAP kinase pathway by the MAP kinase/ERK kinase inhibitor PD98059 or the PI 3-kinase pathway by LY294002 blocks HGF/SF induction of scattering, although in morphologically distinct ways. Expression of constitutively activated PI 3-kinase, Ras, or R-Ras will cause scattering, but activated Raf will not, indicating that activation of the MAP kinase pathway is not sufficient for this response. Downstream of PI 3-kinase, activated PKB/Akt and Rac are both unable to induce scattering, implicating a novel pathway. Scattering induced by Ras or PI 3-kinase is sensitive to PD98059, as well as to LY294002, suggesting that basal MAP kinase activity is required, but not sufficient, for the scattering response. Induction of MDCK cell tubulogenesis in collagen gels by HGF/SF is inhibited by PD98059; expression of activated Ras and Raf causes disorganized growth in this system, but activated PI 3-kinase or R-Ras causes branching tubule formation similar to that seen with HGF/SF treatment. These data indicate that multiple signaling pathways acting downstream of Met and Ras are needed for these morphological effects; scattering is induced primarily by the PI 3-kinase pathway, which acts through effectors other than PKB/Akt or Rac and requires at least basal MAP kinase function. Elevated PI 3-kinase activity induces tubulogenesis, but total inhibition and excess activation of the MAP kinase pathway both oppose this effect.

A truncated isoform of the human beta chain common to the receptors for granulocyte-macrophage colony-stimulating factor, interleukin-3 (IL-3), and IL-5 with increased mRNA expression in some patients with acute leukemia

We report here a naturally occurring isoform of the human beta chain common to the receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 (GMRbetaC) with a truncated intracytoplasmic tail caused by deletion of a 104-bp exon in the membrane-proximal region of the chain. This beta intracytoplasmic truncated chain (betaIT) has a predicted tail of 46 amino acids, instead of 432 for betaC, with 23 amino acids in common with betaC and then a new sequence of 23 amino acids. In primary myeloid cells, betaIT comprised approximately 20% of the total beta chain message, but was increased up to 90% of total in blast cells from a significant proportion of patients with acute leukemia. Specific anti-betaIT antibodies demonstrated its presence in primary myeloid cells and cell lines. Coexpression of betaIT converted low-affinity GMRalpha chains (KD 2.5 nmol/L) to higher-affinity alphabeta complexes (KD 200 pmol/L). These could bind JAK2 that was tyrosine-phosphorylated by stimulation with GM-CSF. betaIT did not support GM-CSF-induced proliferation when cotransfected with GMRalpha into CTLL-2 cells. Therefore, it may interfere with the signal-transducing properties of the betaC chain and play a role in the pathogenesis of leukemia.

Lack of correlation between activation of Jun-NH2-terminal kinase and induction of apoptosis after detachment of epithelial cells

Detachment of epithelial cells from the extracellular matrix leads to induction of programmed cell death, a process that has been termed "anoikis." It has been reported recently that detachment of MDCK cells from matrix results in activation of Jun-NH2-terminal kinases (JNKs) and speculated that these stress activated protein kinases play a causal role in the induction of anoikis (Frisch, S.M., K. Vuori, D. Kelaita, and S. Sicks. 1996. J. Cell Biol. 135:1377-1382). We report here that although JNK is activated by detachment of normal MDCK cells, study of cell lines expressing activated signaling proteins usually controlled by Ras shows that stimulation of JNK fails to correlate with induction of anoikis. Activated phosphoinositide 3-OH kinase and activated PKB/Akt protect MDCK cells from detachment-induced apoptosis without suppressing JNK activation. Conversely, activated Raf and dominant negative SEK1, a JNK kinase, attenuate detachment-induced JNK activation without protecting from apoptosis. zVAD-fmk, a peptide inhibitor of caspases, prevents MDCK cell anoikis without affecting JNK activation. p38, a related stress-activated kinase, is also stimulated by detachment from matrix, but inhibition of this kinase with SB 203580 does not protect from anoikis. It is therefore unlikely that either JNK or p38 play a direct role in detachment-induced programmed cell death in epithelial cells.

Granulocyte-macrophage colony stimulating factor receptor alpha and beta chain complexes can form both high and intermediate affinity functional receptors

Scatchard analysis of primary human haemopoietic cells using iodinated GM-CSF suggests that there are low, intermediate and high affinity classes of the GM-CSF receptor. To investigate the molecular basis of this, we generated a clone of transfected NIH3T3 cells that constitutively expressed the human granulocyte-macrophage colony stimulating factor receptor (GM-CSF R) beta chain and inducibly expressed the human GM-CSF R alpha chain. In the cells fully induced to express the alpha chain the overall level of expression of the alpha and beta chains at the cell surface was comparable with that found in primary haemopoietic cells and cell lines. When cells were partially induced to express the alpha chain, the alpha:beta ratio determined by antibody binding was approximately 1:1 and Scatchard analysis revealed a single class of intermediate affinity receptors (Kd = 614+/-88 pM). In cells with fully induced alpha chain expression, the alpha:beta ratio was approximately 3:1 and there was a switch to a dual high and low affinity receptor with K(d)s of 67+/-32 pM and 1.7+/-0.56 nM respectively. The change from intermediate to high affinity was not associated with changes in alphabeta stoichiometry as detected by cross-linking with radiolabelled GM-CSF and gel electrophoresis. Both the high and intermediate affinity receptors were able to activate the STAT 5 and the MAP kinase pathways, although there was a difference in the ligand dose-response curves which was compatible with the different affinities of the receptors. It is proposed that the switch from an intermediate to high affinity receptor was due to the availability of free alpha chains presenting ligand to the alphabeta chain complexes at the surface of the cell membrane.

Matrix adhesion and Ras transformation both activate a phosphoinositide 3-OH kinase and protein kinase B/Akt cellular survival pathway

Upon detachment from the extracellular matrix, epithelial cells enter into programmed cell death, a phenomenon known as anoikis, ensuring that they are unable to survive in an inappropriate location. Activated ras oncogenes protect cells from this form of apoptosis. The nature of the survival signals activated by integrin engagement and usurped by oncogenic Ras are unknown: here we show that in both cases phosphoinositide 3-OH kinase (PI 3-kinase), but not Raf, mediates this protection, acting through protein kinase B/Akt (PKB/Akt). Constitutively activated PI 3-kinase or PKB/Akt block anoikis, while inhibition of PI 3-kinase abrogates protection by Ras, but not PKB/Akt. Inhibition of either PI 3-kinase or PKB/Akt induces apoptosis in adherent epithelial cells. Attachment of cells to matrix leads to rapid elevation of the levels of PI 3-kinase lipid products and PKB/Akt activity, both of which remain high in Ras-transformed cells even in suspension. PI 3-kinase acting through PKB/Akt is therefore implicated as a key mediator of the aberrant survival of Ras-transformed epithelial cells in the absence of attachment, and mediates matrix-induced survival of normal epithelial cells.

Role of phosphoinositide 3-OH kinase in cell transformation and control of the actin cytoskeleton by Ras

The pathways by which mammalian Ras proteins induce cortical actin rearrangement and cause cellular transformation are investigated using partial loss of function mutants of Ras and activated and inhibitory forms of various postulated target enzymes for Ras. Efficient transformation by Ras requires activation of other direct effectors in addition to the MAP kinase kinase kinase Raf and is inhibited by inactivation of the PI 3-kinase pathway. Actin rearrangement correlates with the ability of Ras mutants to activate PI 3-kinase. Inhibition of PI 3-kinase activity blocks Ras induction of membrane ruffling, while activated PI 3-kinase is sufficient to induce membrane ruffling, acting through Rac. The ability of activated Ras to stimulate PI 3-kinase in addition to Raf is therefore important in Ras transformation of mammalian cells and essential in Ras-induced cytoskeletal reorganization.

Networks of interaction of p120cbl and p130cas with Crk and Grb2 adaptor proteins

P120cbl, the product of the c-cbl proto-oncogene, has previously been shown to become tyrosine phosphorylated following EGF stimulation of cells, and to bind constitutively to the SH3 domain of the adaptor protein Grb2. Here we show that another adaptor protein, Crk, binds through its SH2 domain to tyrosine phosphorylated p120cbl. In addition, Crk becomes phosphorylated on tyrosine and serine following EGF treatment of PC12 and other cell lines. In unstimulated cells, while Grb2 is not bound to any tyrosine phosphoprotein, Crk is bound via its SH2 domain to tyrosine phosphorylated p130cas, the Crk-associated v-Src substrate. Following EGF treatment, Crk dissociates from p130cas, possibly due to a higher affinity of Crk SH2 for p120cbl compared with p130cas. Interaction between Grb2 and p120cbl increases threefold following EGF treatment of cells; in vitro, this induction of Grb2 association with unphosphorylated p120cbl can be mimicked by the addition of tyrosine phosphorylated Shc, suggesting a transfer of information between the SH2 and SH3 domains of Grb2. These data indicate that adaptor proteins can exchange binding partners in response to stimuli, and that different adaptor proteins can bind to the same partners by different mechanisms.