Discernment between candidate mechanisms for KRAS G13D colorectal cancer sensitivity to EGFR inhibitors
CELL COMMUNICATION AND SIGNALING
Authors: McFall, Thomas; Schomburg, Noah K.; Rossman, Kent L.; Stites, Edward C.
Abstract
Phase three clinical trial evidence suggests that colorectal cancers with the KRAS G13D mutation may benefit from EGFR inhibitors, like cetuximab, in contrast to the other most common KRAS mutations. A mechanism to explain why this mutation behaves differently from other KRAS mutations had long been lacking. Two recent studies have reproduced KRAS G13D specific sensitivity to cetuximab in cellular models, and both have implicated the tumor suppressor NF1 as a critical variable in determining sensitivity and resistance. One study proposes a mechanism that focuses on the inhibition of active, GTP-bound wild-type RAS, which is proposed to occur to a greater extent in KRAS G13D tumors due to the inability of KRAS G13D to bind NF1 well. The other study suggests NF1 can convert GTP-bound KRAS G13D to inactive, GDP-bound KRAS G13D. Here, we report an inability to reproduce cellular and biophysical studies that suggested NF1 has strong GTPase activity on KRAS G13D. We also report additional data that further suggests only WT RAS-GTP levels are reduced with EGFR inhibition and that KRAS G13D is impaired in binding to NF1. These new experiments further support a mechanism in which cetuximab inhibits wild-type (HRAS and NRAS) signals in KRAS G13D colorectal cancers.
Incidence of nephrotoxicity with prolonged aminoglycoside exposure in patients with cystic fibrosis
PEDIATRIC PULMONOLOGY
Authors: Saad, Anasemon; Young, McKenzie R.; Studtmann, Anna E.; Autry, Elizabeth B.; Schadler, Aric; Beckman, Elizabeth J.; Gardner, Brian M.; Wurth, Mark A.; Kuhn, Robert J.
Abstract
Cystic fibrosis (CF) patients, with Pseudomonas aeruginosa infection, often require repeated aminoglycoside courses for the management of acute pulmonary exacerbations (APEs). Acute kidney injury (AKI) due to aminoglycosides has been reported; little data exist regarding long-term nephrotoxicity with repeated exposure. The objective of this study was to describe the incidence of acute and chronic nephrotoxicity due to cumulative intravenous (IV) aminoglycoside exposure. This is a retrospective, observational study of pediatric and adult CF patients admitted to an academic medical center between January 1, 2006 and October 1, 2018 for APE management. Patients were eligible for inclusion if they received at least five courses of an IV aminoglycoside for at least 7 days each. Cumulative weight-based aminoglycoside dose was reported in milligrams per kilogram. For each admission, baseline and highest serum creatinine were collected to assess the incidence of AKI. The baseline and final estimated glomerular filtration rate (eGFR) were calculated to assess long-term effects on renal function. Sixty-six patients, representing greater than 700 courses, were included in the final analysis. The median cumulative weight-based aminoglycoside dose was 1183 mg/kg of tobramycin or tobramycin equivalent. Twenty percent of courses resulted in AKI; 86% were Stage 1. A repeated measure multivariate model showed colistin, piperacillin/tazobactam, vancomycin, and age were significant AKI risk factors. There was no correlation between cumulative aminoglycoside dose and change in eGFR. AKI from IV aminoglycoside exposure occurred in 20% of courses. Cumulative exposure to IV aminoglycosides in APE management was not correlated with long-term renal dysfunction.
COA
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