FIGURE 5.

KLK5 silencing inhibits tumor growth and progression in an orthotopic murine OSCC xenograft model. Cells (0.8 × 10⁶ in 30 μl of PBS) with diminished KLK5 expression (designated SCC25-KLK5-KD) or vector controls (SCC25-Vec) were injected into the lateral border of the base of the tongue and allowed to grow for 9 weeks. Following sacrifice, tumors were harvested, processed for histology, and stained with H&E. A and B, representative tumors formed from SCC25-Vec control cells are poorly circumscribed with invasive cords of tumor cells, characteristic of moderately differentiated OSCC. Magnification, ×200. C, section of SCC25-Vec tumor immunostained with anti-KLK 5 antibody (1:200) and peroxidase-conjugated secondary antibody. Magnification, ×400. D and E, representative tumors formed from SCC25-KLK5-KD cells with silenced KLK5 expression are well circumscribed with pushing tumor margins and keratin pearls (*), characteristic of well differentiated OSCC. Magnification, ×200. F, representative section of SCC25-KLK5-KD tumor immunostained with anti-KLK5 antibody. Magnification, ×400. G, quantitation of tumor area. Tumors formed from SCC25-Vec cells were ∼8-fold larger than SCC25-KLK5-KD tumors (p = 0.002).