<i>PIK3CA</i> is upregulated in non-proliferating tumor cells <i>in vivo.</i>

<p>A to C. Double immunostaining of p110α (green, FITC) and Ki67 (red, Texas Red) in human ovarian cancer B. High magnification of a region from A with low expression of p110α. p110α is expressed at low levels and localizes to the cytoplasm of Ki67-positive tumor cells. C. High magnification of a region from A with high expression of p110α. p110α is expressed at high levels and localizes to the plasma membrane in Ki67-negative tumor cells. D and E. Immunohistochemical localization of Ki67 allows for clear identification of areas of proliferating and areas of non-proliferating tumor cells <i>in vivo</i> in 2008 ovarian xenograft tumors. E. High magnification of area from D showing the boundary between a proliferating and a non-proliferating region. F to H. Strong expression and cell membrane localization of p110α is only found in Ki67-negative areas. F. Section adjacent to D, stained with antibody against human p110α (1:250 dilution). G. High magnification of area from F showing the boundary between proliferating and non-proliferating region. H. High magnification of area from G showing membrane localization of p110α in the non-proliferating region. I. Immunostaining of human cytokeratin identifies tumor cells in proliferating and non-proliferating areas in the 2008 xenograft model. The line traces the boundary between the two areas, as defined by Ki67 staining in adjacent section (see J). Both proliferating and non-proliferating regions are positive for human cytokeratin (FITC, green), indicating tumor cells. Cell nuclei were counterstained with DAPI. J to L. Double p110α and Ki67 immunostaining maps <i>PIK3CA</i> activation in proliferating or non-proliferating areas in 2008 xenograft tumors. J. Ki67 (red, Texas Red) and p110α (FITC, green) exhibit reciprocal expression. K and L. High magnification of proliferating region (I) and non-proliferating region (H) from J.