Sindhu Chandran

The Akt pathway in human breast cancer: a tissue-array-based analysis.

The Akt pathway, an important regulator of cell proliferation and survival, is deregulated in many cancers. The pathway has achieved considerable importance due to the development of kinase inhibitors that are able to successfully reduce tumor growth. This study was conducted to determine the status of the Akt pathway in human breast cancers and to study the relationship between the different component proteins. Expression levels of PTEN, phosphorylated forms of the constituent proteins (Akt, FKHR, mTOR, and S6) and cyclin D1 were evaluated by immunohistochemistry, on consecutive sections from a tissue microarray containing 145 invasive breast cancers and 140 pure ductal carcinomas in-situ. Aberrant expression was correlated statistically with tumor characteristics and disease outcome. The Akt pathway was found to be activated early in breast cancer, in the in-situ stage. In all, 33, 15, 32, and 60% of ductal carcinoma in-situ showed overexpression of Akt, FKHR, mTOR, and cyclin D1. PTEN loss did not correlate statistically with expression of AKT or any of the other proteins with the exception of S6, indicating that Akt activation was not a result of PTEN loss. Expression levels of PTEN and S6 were significantly different in in-situ and invasive cancers, indicating association with disease progression. Loss of PTEN was noted in 11% of in-situ as compared to 26% of invasive cancers, while S6 overexpression was seen in 47% in-situ and in 72% invasive cancers. High-grade carcinomas were associated with PTEN loss, while low-grade carcinomas with good prognostic features showed cyclin D1 overexpression and were associated with longer disease free survival. Additionally, cancers with mTOR overexpression showed a three times greater risk for disease recurrence. Overall, a large proportion of in-situ and invasive breast cancers overexpressed cyclinD1 and S6. Our results may have significant implications in the development and application of targeted therapy.

Eculizumab for the treatment of de novo thrombotic microangiopathy post simultaneous pancreas-kidney transplantation--a case report.

A 34-year-old female recipient of a simultaneous pancreas-kidney transplant presented 7 days posttransplant with acute renal allograft dysfunction, thrombocytopenia, and microangiopathic hemolytic anemia. Renal biopsy revealed acute antibody-mediated rejection (AMR) and acute thrombotic microangiopathy (TMA). Clinical and laboratory manifestations, which had only partly responded to treatment with daily plasma exchange and intravenous immunoglobulin, resolved rapidly and completely to eculizumab (Soliris, Alexion Pharmaceuticals, Inc., Cheshire, Conn), a complement factor C5 antibody. De novo posttransplant TMA is a rare and serious complication that can lead to graft loss in up to one third of cases. This is the first report of successful treatment of de novo TMA with eculizumab, which has previously shown benefit in recurrent atypical hemolytic uremic syndrome as well as in refractory acute AMR. Targeted complement inhibition offers the promise of a safe and effective therapeutic strategy in de novo TMA, especially in light of recent evidence suggesting that genetic mutations in complement regulatory proteins may predispose transplant recipients to this serious disease.

Imatinib in the treatment of nephrogenic systemic fibrosis.

Nephrogenic systemic fibrosis is a disabling progressive condition that is being reported with increased frequency in patients with kidney disease. Treatment is extremely limited and largely supportive. We report a case of severe nephrogenic systemic fibrosis in a dialysis patient exposed to multiple doses of gadolinium who improved clinically and histologically with treatment with imatinib.

Ciprofloxacin prophylaxis in kidney transplant recipients reduces BK virus infection at 3 months but not at 1 year.

Background BK polyomavirus (BKV) infection remains a significant cause of nephropathy and graft loss. Fluoroquinolones inhibit BKV replication in vitro, and small studies suggest in vivo benefit. A strategy of fluoroquinolone prophylaxis directed specifically against BKV has not been formally tested against a control group in kidney transplant recipients. Methods We retrospectively compared the impact of a change in antibiotic prophylaxis practice from no BKV prophylaxis (Group 1, n=106, July–December 2009) to BKV prophylaxis with ciprofloxacin 250 mg twice daily for 30 days (Group 2, n=130, January–June 2010) on the rate of BKV infection during the first 12 months after kidney transplantation. Results Baseline demographics, transplant characteristics, induction immunosuppression, and 1-year incidence of acute rejection were similar between groups. Group 1 had fewer patients on maintenance corticosteroids (65.1% vs. 83.2%, P=0.002). At 3 months, Group 1 had a significantly higher risk of developing BK viremia (0.161 vs. 0.065, P=0.0378) and viruria (0.303 vs. 0.146, P=0.0067) compared with Group 2, but this difference disappeared at 12 months for both viremia (0.297 vs. 0.261, P=0.6061) and viruria (0.437 vs. 0.389, P=0.5363). Adjusting for the difference in steroid use did not change the results. There was a trend toward higher incidence of biopsy-proven BKV nephropathy in Group 1 (4.7% vs. 0.8%, P=0.057). Conclusion Thirty-day ciprofloxacin prophylaxis in kidney transplant recipients is associated with a lower rate of BKV infection at 3 months but not at 12 months. The long-term effectiveness and optimal duration of fluoroquinolone prophylaxis against BKV infection remain unknown.

Phosphopeptide screen uncovers novel phosphorylation sites of Nedd4-2 that potentiate its inhibition of the epithelial Na+ channel.

The E3 ubiquitin ligase Nedd4-2 regulates several ion transport proteins, including the epithelial Na+ channel (ENaC). Nedd4-2 decreases apical membrane expression and activity of ENaC. Although it is subject to tight hormonal control, the mechanistic basis of Nedd4-2 regulation remains poorly understood. To characterize regulatory inputs to Nedd4-2 function, we screened for novel sites of Nedd4-2 phosphorylation using tandem mass spectrometry. Three of seven identified Xenopus Nedd4-2 Ser/Thr phosphorylation sites corresponded to previously identified target sites for SGK1, whereas four were novel, including Ser-293, which matched the consensus for a MAPK target sequence. Further in vitro and in vivo phosphorylation experiments revealed that Nedd4-2 serves as a target of JNK1, but not of p38 MAPK or ERK1/2. Additional rounds of tandem mass spectrometry identified two other phosphorylated residues within Nedd4-2, including Thr-899, which is present within the catalytic domain. Nedd4-2 with mutations at these sites had markedly inhibited JNK1-dependent phosphorylation, virtually no ENaC inhibitory activity, and significantly reduced ubiquitin ligase activity. These data identify phosphorylatable residues that activate Nedd4-2 and may work together with residues targeted by inhibitory kinases (e.g. SGK1 and protein kinase A) to govern Nedd4-2 regulation of epithelial ion transport.

Neural Precursor Cell-expressed Developmentally Down-regulated Protein 4-2 (Nedd4-2) Regulation by 14-3-3 Protein Binding at Canonical Serum and Glucocorticoid Kinase 1 (SGK1) Phosphorylation Sites

Background: Coordinate regulation by kinases and 14-3-3 proteins regulates sodium transport through phosphorylation and inhibition of E3 ligases. Results: Phosphorylation at similar but distinct target motifs can either inhibit or stabilize E3 ligases. Conclusion: E3 ligases integrate multiple kinase inputs to regulate sodium transport and protein stability. Significance: These findings broaden our knowledge of how E3 ligases and sodium transport are regulated by phosphorylation. Regulation of epithelial Na+ channel (ENaC)-mediated transport in the distal nephron is a critical determinant of blood pressure in humans. Aldosterone via serum and glucocorticoid kinase 1 (SGK1) stimulates ENaC by phosphorylation of the E3 ubiquitin ligase Nedd4-2, which induces interaction with 14-3-3 proteins. However, the mechanisms of SGK1- and 14-3-3-mediated regulation of Nedd4-2 are unclear. There are three canonical SGK1 target sites on Nedd4-2 that overlap phosphorylation-dependent 14-3-3 interaction motifs. Two of these are termed “minor,” and one is termed “major,” based on weak or strong binding to 14-3-3 proteins, respectively. By mass spectrometry, we found that aldosterone significantly stimulates phosphorylation of a minor, relative to the major, 14-3-3 binding site on Nedd4-2. Phosphorylation-deficient minor site Nedd4-2 mutants bound less 14-3-3 than did wild-type (WT) Nedd4-2, and minor site Nedd4-2 mutations were sufficient to inhibit SGK1 stimulation of ENaC cell surface expression. As measured by pulse-chase and cycloheximide chase assays, a major binding site Nedd4-2 mutant had a shorter cellular half-life than WT Nedd4-2, but this property was not dependent on binding to 14-3-3. Additionally, a dimerization-deficient 14-3-3ϵ mutant failed to bind Nedd4-2. We conclude that whereas phosphorylation at the Nedd4-2 major site is important for interaction with 14-3-3 dimers, minor site phosphorylation by SGK1 may be the relevant molecular switch that stabilizes Nedd4-2 interaction with 14-3-3 and thus promotes ENaC cell surface expression. We also propose that major site phosphorylation promotes cellular Nedd4-2 protein stability, which potentially represents a novel form of regulation for turnover of E3 ubiquitin ligases.

Complications of Ultrasound-Guided Renal Transplant Biopsies

Renal transplant biopsies to diagnose transplant pathology are routinely performed using ultrasound guidance. Few large studies have assessed the rate and risk factors of major biopsy complications. This study is a single‐center 5‐year retrospective cohort analysis of 2514 biopsies. Major complications occurred in 47 of 2514 patients (1.9%) and included hospitalization, transfusion of blood products, operative exploration and interventional radiology procedures. The complication rate among “cause” biopsies was significantly higher than in “protocol” biopsies (2.7% vs. 0.33%, p < 0.001). Complications presented on postbiopsy days 0–14, with the majority diagnosed on the same day as the biopsy and manifested by hematocrit drop, although the presence of such delayed presentation of complications occurring >24 h after the biopsy on days 2–14 is previously unreported. Specific patient characteristics associated with increased risk of a complication were increased age and blood urea nitrogen, decreased platelet count, history of prior renal transplant, deceased donor transplant type and use of anticoagulant medications but not aspirin.

Polyclonal Regulatory T cell Therapy for Control of Inflammation in Kidney Transplants

Early subclinical inflammation in kidney transplants is associated with later graft fibrosis and dysfunction. Regulatory T cells (Tregs) can reverse established inflammation in animal models. We conducted a pilot safety and feasibility trial of autologous Treg cell therapy in three kidney transplant recipients with subclinical inflammation noted on 6‐month surveillance biopsies. Tregs were purified from peripheral blood and polyclonally expanded ex vivo using medium containing deuterated glucose to label the cells. All patients received a single infusion of ~320 × 106 (319, 321, and 363.8 × 106) expanded Tregs. Persistence of the infused Tregs was tracked. Graft inflammation was monitored with follow‐up biopsies and urinary biomarkers. Nearly 1 × 109 (0.932, 0.956, 1.565 × 109) Tregs were successfully manufactured for each patient. There were no infusion reactions or serious therapy‐related adverse events. The infused cells demonstrated patterns of persistence and stability similar to those observed in non‐immunosuppressed subjects receiving the same dose of Tregs. Isolation and expansion of Tregs is feasible in kidney transplant patients on immunosuppression. Infusion of these cells was safe and well tolerated. Future trials will test the efficacy of polyclonal and donor alloantigen‐reactive Tregs for the treatment of inflammation in kidney transplants.

Effect of ciprofloxacin combined with sulfamethoxazole-trimethoprim prophylaxis on the incidence of urinary tract infections after kidney transplantation.

Background Urinary tract infections (UTIs) are common after kidney transplantation, with limited data to guide antibiotic prophylaxis. Methods Retrospective single-center study comparing sulfamethoxazole-trimethoprim 800/160 mg (SMZ/TMP) daily for 30 days followed by Monday, Wednesday, Friday for an additional 5 months (Group 1) versus SMZ/TMP Monday, Wednesday, Friday for 6 months plus ciprofloxacin 250 mg twice daily for 30 days (Group 2) on UTI incidence after kidney transplantation. Results There were 106 and 130 patients in Groups 1 and 2, respectively. Demographics and transplant characteristics were well matched, except for more patients in Group 2 on corticosteroid maintenance. At 1 year, more patients in Group 1 developed UTIs (23.6% vs. 10.8%; P=0.01) and the mean time to first UTI was shorter (96.6±79.5 vs. 168±89.7 days; P=0.01). UTIs caused by Enterococcus species were higher in Group 2 (28.6% vs. 4%; P=0.047) with enteric gram-negative bacilli accounting for the remaining infections. There was a similar incidence of enteric gram-negative antibiotic resistance to SMZ/TMP (75% vs. 80%; P=1.00) and ciprofloxacin (16.7% vs. 30%; P=0.39) in Groups 1 and 2. For Groups 1 and 2, the proportion of first UTIs requiring hospitalization was 48.9% vs. 40.6%, respectively (P=0.62). Female gender was a UTI risk factor (hazard ratio, 3.5; 95% confidence interval, 1.78–6.8; P=0.0003). Conclusions The addition of a 30-day course of ciprofloxacin lowered the incidence of UTI; randomized prospective studies are needed to confirm the safety and efficacy of this approach.

Prediabetic living kidney donors have preserved kidney function at 10 years after donation.

Background Potential living kidney donors with prediabetes are often excluded from donation because of concerns about the development of type 2 diabetes mellitus (DM) and progression to end-stage renal disease (ESRD). This strategy may be unnecessarily restrictive. Previous studies of living kidney donors have not specifically examined subsets with prediabetes. Methods We ascertained the vital status and development of ESRD in 143 living kidney donors from 1994 to 2007 with predonation impaired fasting glucose (IFG). We then compared the development of DM, the estimated glomerular filtration rate, and the level of albumin excretion in 45 of these IFG donors to 45 matched controls with normal predonation fasting glucose. Results The majority (57.8%) of IFG donors had reverted to normal fasting glucose at a mean follow-up of 10.4 years. Compared with donors with normal fasting glucose, a higher proportion of IFG donors had developed DM (15.56% vs. 2.2%, P=0.06). Predonation characteristics including age, sex, and body mass index did not correlate with the risk of developing DM. At follow- up, estimated glomerular filtration rate by the Modification of Diet in Renal Disease equation (70.7±16.1 mL/min/1.73 m2 vs. 67.3±16.6 mL/min/1.73 m2, P=0.21) and albumin excretion (urine albumin/ creatinine 9.76±23.6 mg/g vs. 5.91±11 mg/g, P=0.29) were similar in IFG and normal glucose donors. Conclusion Carefully screened prediabetic living kidney donors often revert to normal fasting glucose and do not seem to have a significantly increased risk of impaired kidney function in the short term.