Elevated matriptase activity enhances peritoneal dissemination in an orthotopic xenograft model. (A) Experimental timeline: Stable ES-2 Vec and Mat cell lines expressing luciferase were injected i.p. into female nude mice (5 × 10⁶ cells per mouse, n = 5 mice/group) and tumor burden was monitored by IVIS imaging (Xenogen) at days 1, 4, and 8 after sorting into cohorts of similar tumor burden. (B) Images of the peak luciferase activity levels of individual mice in the Vec and Mat cohorts. (C) Mouse diaphragms were fixed with paraformaldehyde, paraffin-embedded, and stained with H&E. Representative images of ES-2 Vec and Mat tumor-bearing diaphragms were taken at 4× (scale bar = 1,000 μm; left panels), 10× (scale bar = 500 μm; middle panels), and 20× (scale bar = 200 μm; right panels) magnification to show areas of tumor (T), necrotic tissue (N), and smooth muscle cells (SM). Images show expansive areas of invasive fronts (Vec) and infiltrated areas of tumor lesions that have seeded dispersed areas of tissue (Mat). (D) Morphological analysis of ascites fluid recovered from ES-2-Mat tumor-bearing mice was analyzed using cytospins stained with Kwik-Diff (no ascites was recovered from ES-2-Vec bearing mice). A representative whole scan at 4× magnification (scale bar = 1,000 μm and 10× image; scale bar = 500 μm) is shown.