HBx induces tumor cell invasion in vivo and in vitro. (a and b) In vivo invasion. CMO and CMX (a) or HepG2 and 2.2.15 (b) were analyzed for their ability to invade the CAM of a chick embryo. The results are expressed as percentage of human DNA (left) or as number of intravasated cells (right). Experiments were carried out at least in quadruplicate. (c and d) In vitro invasion. The invasive capacity of CMO and CMX (c) or HepG2 and 2.2.15 (d) cells was tested using Matrigel-coated Transwells. Cells in the underside of the filter were stained, and eight independent fields were counted. The results are expressed as the mean value ± SE of three independent points.