Activation mechanisms of clinically distinct B-Raf V600Eand V600K mutants

Dear Editor,B-Raf,the main effector of Ras in the mitogen-activated protein kinase(MAPK)pathway,is among the most highly mutated kinases in human cancer[1].About 40%-60%of melanoma patients harbor B-Raf mutations,of which∼90%involve V600E and V600K.B-RafV600E is more frequent(60%-80%)than B-RafV600K(10%-30%).Substitution of a Val codon by Glu requires a single nucleotide change,whereas Val to Lys requires two[2].This is in line with melanoma patients harboring the V600K mutation,who usually suffer from higher sun exposure that may induce increased DNA damage[3].Since both mutations occur at the same position of the kinase domain and are mutated to charged residues,it was believed that the B-Raf V600E and V600K mutantswould share a similar behavior,and in clinical trials,patients with V600E and V600K mutations have been recruited into the same cohort.

Suspension electrospinning of decellularized extracellular matrix: A new method to preserve bioactivity

Decellularized extracellular matrices (dECM) have strong regenerative potential as tissue engineering scaffolds;however, current clinical options for dECM scaffolds are limited to freeze-drying its native form into sheets. Electrospinning is a versatile scaffold fabrication technique that allows control of macro- and microarchitecture. It remains challenging to electrospin dECM, which has led researchers to either blend it with synthetic materials or use enzymatic digestion to fully solubilize the dECM. Both strategies reduce the innate bioactivity of dECM and limit its regenerative potential. Herein, we developed a new suspension electrospinning method to fabricate a pure dECM fibrous mesh that retains its innate bioactivity. Systematic investigation of suspension parameters was used to identify critical rheological properties required to instill “spinnability,” including homogenization, concentration, and particle size. Homogenization enhanced particle interaction to impart the requisite elastic behavior to withstand electrostatic drawing without breaking. A direct correlation between concentration and viscosity was observed that altered fiber morphology;whereas, particle size had minimal impact on suspension properties and fiber morphology. The versatility of this new method was demonstrated by electrospinning dECM with three common decellularization techniques (Abraham, Badylak, Luo) and tissue sources (intestinal submucosa, heart, skin). Bioactivity retention after electrospinning was confirmed using cell proliferation, angiogenesis, and macrophage polarization assays. Collectively, these findings provide a framework for researchers to electrospin dECM for diverse tissue engineering applications.