Management of metastatic disease is integral to cancer treatment. Evaluation of metastases often requires surgical removal of all anatomically susceptible lymph nodes for ex vivo pathologic examination. We report a family of novel ratiometric activatable cell-penetrating peptides, which contain Cy5 as far red fluorescent donor and Cy7 as near-infrared fluorescent acceptor. Cy5 is quenched in favor of Cy7 reemission until the intervening linker is cut by tumor-associated matrix metalloproteinases-2 and 9 (MMP2,9) or elastases. Such cleavage increases the Cy5:Cy7 emission ratio 40-fold and triggers tissue retention of the Cy5-containing fragment. This ratiometric increase provides an accelerated and quantifiable metric to identify primary tumors and metastases to liver and lymph nodes with increased sensitivity and specificity. This technique represents a significant advance over existing nonratiometric protease sensors and sentinel lymph node detection methods, which give no information about cancer invasion.
Increase in tongue weight and percentage of fat, and therefore tongue volume, may explain why patients with weight gain have higher rates of SDB. Tongue weight, fat, and volume may also correlate with and explain Mallampati grades.
In real time: Thrombin activation in vivo can be imaged in real time with ratiometric activatable cell penetrating peptides (RACPPs). RACPPs are designed to combine 1) dual‐emission ratioing, 2) far red to infrared wavelengths for in vivo mammalian imaging, and 3) cleavage‐dependent spatial localization. The most advanced RACPP uses norleucine (Nle)‐TPRSFL as a linker that increases sensitivity to thrombin by about 90‐fold (see figure).
Extracellular proteases including thrombin are involved in numerous biological processes and play major roles in a variety of human diseases. The spatial and temporal patterns of activation of proteases in vivo control their biological role in diseases and amenability to therapeutic targeting. Previously we developed activatable cell-penetrating peptides (ACPPs) to monitor matrix metalloproteinase (MMP) and elastase activity in tumors. Later ACPPs detect thrombin activation in atherosclerosis and brain injury. We have now modified the thrombin ACPP in two independent ways, 1) to provide a FRET-dependent emission ratiometric readout and 2) to accelerate the kinetics of cleavage by thrombin. Emission ratioing improves kinetic detection of enzyme activity, because it reflects the ratio of cleaved versus uncleaved probe but cancels out total probe concentration, illumination intensity, detection sensitivity, and tissue thickness. Because pharmacokinetic washout of the uncleaved probe is not necessary, yet the cleavage converts a diffusible substrate into an immobilized product, thrombin activity can be imaged in real time with good spatial resolution. Meanwhile, placement of norleucine-threonine (Nle-Thr) at the P4-P3 substrate positions accelerates the kinetics of thrombin cleavage by 1-2 orders of magnitude, while preserving selectivity against related proteases. The new ratiometric ACPPs detect localized thrombin activation in rapidly forming blood clots minutes after probe injection, and the signal is inhibited by thrombin specific inhibitors.Thrombin is a serine protease and a key regulator of blood coagulation. It is responsible for the proteolytic cleavage and activation of multiple coagulation factors including Factor V,
Objective (1) Obtain matrix-metalloproteinase (MMP) expression profiles for head and neck squamous cell carcinoma (HNSCC) specimens from the Cancer Genomic Atlas (TCGA). (2) Demonstrate HNSCC imaging using MMP-cleavable, fluorescently labeled ratiometric activatable cell-penetrating peptide (RACPP). Study Design Retrospective human cohort study; prospective animal study. Setting Translational research laboratory. Subjects and Methods Patient clinical data and mRNA expression levels of MMP genes were downloaded from TCGA data portal. RACPP provides complementary ratiometric fluorescent contrast (increased Cy5 and decreased Cy7 intensities) when cleaved by MMP2/9. HNSCC–tumor bearing mice were imaged in vivo after RACPP injection. Histology was evaluated by a pathologist blinded to experimental conditions. Zymography confirmed MMP-2/9 activity in xenografts. RACPP was applied to homogenized human HNSCC specimens, and ratiometric fluorescent signal was measured on a microplate reader for ex vivo analysis. Results Expression of multiple MMPs including MMP2/9 is greater in patient HNSCC tumors than matched control tissue. In patients with human papilloma virus positive (HPV+) tumors, higher MMP2 and MMP14 expression correlates with worse 5-year survival. Orthotopic tongue HNSCC xenografts showed excellent ratiometric fluorescent labeling with MMP2/9-cleavable RACPP (sensitivity = 95.4%, specificity = 95.0%). Fluorescence ratios were greater in areas of higher tumor burden (P <.03), which is useful for intraoperative margin assessment. Ex vivo, human HNSCC specimens showed greater cleavage of RACPP when compared to control tissue (P = .009). Conclusions Human HNSCC tumors show increased mRNA expression of multiple MMPs including MMP2/9. We used RACPP, a ratiometric fluorescence assay of MMP2/9 activity, to show improved occult tumor identification and margin clearance. Ex vivo assays using RACPP in biopsy specimens may identify patients who will benefit from intraoperative RACPP use.
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