Fig. 2.

Down-regulation of 4.1B increases the metastatic potential of poorly metastatic #78 cells. (A and B) The average mass of the draining paraaortic/lumbar lymph nodes (A), and the percentage node area that had been infiltrated by tumor cells (B) were both significantly increased in mice bearing #78 orthotopic tumors expressing DL1 and DL2 shRNAs against 4.1B relative to those bearing #78 control tumors. (C) Paraaortic/lumbar lymph nodes from mice bearing #78 tumors expressing DL1 and DL2 were often completely infiltrated by tumor cells, with few apoptotic cells present (Lower). In contrast, nodes from mice bearing control #78 tumors (Upper) more commonly possessed areas of subcapsular invasion, where apoptotic cells were frequently observed (arrows). In most cases, the interior regions of these nodes were relatively uninvaded (*). Representative serial lymph node sections stained either by H&E (Left) or for apoptosis (Right) are shown at ×20 magnification.