Abstract
We examined the influence of surgical stress on hematogenous metastasis of malignant tumor cells. The study was performed by focusing on the involvement of inflammatory cytokines in the serum, raised acutely after surgery, and endothelial adhesion molecules in the metastatic process. Surgical stress, given to C57BL/6 mice before B16-BL6 melanoma inoculation, significantly enhanced the pulmonary metastasis. This enhancement was seen when the surgery lasted for more than 2 h. After the 2-h surgery, the enhancement of pulmonary metastasis was seen most remarkably when B16-BL6 was inoculated 24 h after surgery. The serum level of tumor necrosis factor alpha (TNF alpha) in the mice that underwent the 2-h surgery peaked 12 h after the surgery. In contrast, serum interferon gamma was not detectable. Administration of an anti-TNF alpha mAb before the surgery inhibited the enhanced metastasis by inhibiting the increased expression of vascular cell adhesion molecule 1 (VCAM-1) on lung vascular endothelium after the surgery. Pretreatment of B16-BL6 cells with an anti-very late activation antigen 4 (anti-VLA-4) mAb completely inhibited the enhanced metastasis after surgery. Administration of an anti-VCAM-1 mAb before surgery also inhibited the enhancement. These results indicate that serum TNF alpha, raised by surgical stress, is critically involved in the enhanced pulmonary metastasis of mouse melanoma by inducing VCAM-1 expression on lung vascular endothelium.