Figure 11. Neratinib enhances the ability of [regorafenib + sildenafil] to suppress the growth of colorectal tumors.

A. and B. Female-derived CT26 mouse colorectal / male-derived PAN02 mouse pancreatic carcinoma cells (2 × 10⁴) were implanted into rear flanks of female BALB/c and male C57/BL6 mice, respectively. Tumors were permitted to form until the mean tumor volume was ~40 mm³. Animals were then segregated into groups with near identical mean volumes and the animals then treated for three days with the indicated therapeutic agents: vehicle control (cremophore); regorafenib (20 mg/kg QD Days 1–3); [regorafenib (20 mg/kg QD Days 1–3 and sildenafil (5 mg/kg QD Days 1–3)]; neratinib (15 mg/kg QD Days 1–3); or the three drugs in combination. Tumor volumes were measured prior to drug administration and every three days after the initiation of therapeutic interventions. (n = 10 mice per group +/−SEM). Before, during and after drug treatment tumors are calipered as indicated in the Figure and tumor volume was assessed up to 24 days later. When the volume of the tumor reached >1,500 mm³, animals were humanely sacrificed. * p < 0.05 less growth than tumors treated with [regorafenib + sildenafil]. C. Normal tissues were fixed in formalin on Day 24. Tissues were embedded in paraffin wax and five-micron sections taken. Sections were deparaffinized and H&E stained. Images of the normal tissues were taken at 40X magnification.