Surgical stress promotes tumor growth in ovarian carcinoma

Abstract

Purpose: Surgical stress has been suggested to facilitate the growth of preexisting micrometastases as well as small residual tumor postoperatively. The purpose of this study was to examine the effects of surgical stress on ovarian cancer growth and to determine underlying mechanisms responsible for increased growth.

Experimental design: To mimic the effects of surgery, we did a laparotomy or mastectomy under isoflurane inhalation on athymic nude mice 4 days after i.p. tumor cell injection. Propranolol infusion via Alzet pumps was used to block the influence of sympathetic nervous system activation by surgical stress.

Results: In both HeyA8 and SKOV3ip1 models, the mice in the laparotomy and mastectomy groups had significantly greater tumor weight (P < 0.05) and nodules (P < 0.05) compared with anesthesia only controls. There was no increase in tumor weight following surgery in the beta-adrenergic receptor-negative RMG-II model. Propranolol completely blocked the effects of surgical stress on tumor growth, indicating a critical role for beta-adrenergic receptor signaling in mediating the effects of surgical stress on tumor growth. In the HeyA8 and SKOV3ip1 models, surgery significantly increased microvessel density (CD31) and vascular endothelial growth factor expression, which were blocked by propranolol treatment.

Conclusion: These results indicate that surgical stress could enhance tumor growth and angiogenesis, and beta-blockade might be effective in preventing such effects.

Figure 1

Effect of surgical stress on in vivo ovarian cancer growth. Quantification of tumor weights in control (anesthesia alone) mice and in surgically stressed mice (mastectomy or laparotomy) that were injected intraperitoneally with HeyA8, SKOV3ip1, or RMG-II ovarian cancer cells. Results represent the mean ± s.e.m.; n = 10 mice per group. *P < 0.05 compared with control group.

Figure 2

The effect of propranolol in the SKOV3ip1 model for surgical stress. (A) Tumor weight and (B) the number of nodules following treatment with the β-blocker propranolol (2 mg/kg/d) using osmotic minipumps. Results represent the mean ± s.e.m.; n = 10 mice per group. *P < 0.05 compared with control group; ^# P < 0.05 compared with each stress + PBS group.

Figure 3

Proliferation and angiogenesis in tumor tissues is increased in tumors harvested from animals exposed to surgical stress. (A) HeyA8 tumor samples from control (anesthesia alone) or surgically (mastectomy or laparotomy) stressed animals were stained for CD31, VEGF, and PCNA by immunohistochemistry. (B) RMG-II (ADRB-null) tumor samples from mice exposed to surgery did not show any differences in CD31, VEGF, and PCNA staining between control and laparotomy. All photographs were taken at original magnification ×100. The bars in the graphs correspond sequentially to the labeled columns of images at left. Error bars represent s.e.m. *P < 0.05

Figure 4

The effect of propranolol on angiogenesis in surgically stressed mice. SKOV3 tumor samples obtained from control or surgically stressed mice were treated with placebo (PBS pump) or propranolol pump and stained for CD31 (A) and VEGF (B) by immunohistochemistry. All photographs were taken at original magnification ×100. Error bars represent s.e.m. * P < 0.05.

Figure 5

Levels of cytokines/chemokines in mouse serum following surgical stress. Cytokine/chemokine concentrations were measured in mouse sera using xMAP technology with multiplexe cytokine Bio-Rad kit. Results represent the mean ± s.e.m.