Histology, proliferation and apoptosis of tumor xenograft characteristics in nude (<i>nu/nu</i>) mice.

<p>Fixed HT-29 human colon tumor xenografts from nude (<i>nu/nu</i>) mice were sectioned at 5 µm. Panel (a) shows a representative H&E section of the tumor xenografts as a typical undifferentiated carcinoma with viable solid sheets of tumor cells (area marked by black dotted line) and clearly delineated subcutis margin (red arrow); key characteristics include grey distending tumor cell cytoplasm (black arrow) and the necrotic area (black donut). Representative immunohistochemical staining of PCNA is shown in panel (b) with proliferating cells seen as dark brown stained cells. TUNEL staining is shown in panel (c) with apoptotic cells observed as dark spots (red arrow). The bar graph in panel (d) shows the ratio of the indices (mean ± SE) of proliferating (PCNA-positive) and apoptotic (TUNEL-positive) cells for each diet: acrylamide at 0 (control), 0.5, 1.0 and 2.0 mg/kg diet.