Inhibition of gastric cancer cell adhesion in nude mice by inraperitoneal phospholipids

Adhesion of tumor cells to mesothelial cells or extracellular matrix components is a pivotal step in developing peritoneal dissemination after gastric cancer. As phospholipids were found to reduce adhesion formation, especially at sites of peritoneal lesions, we assessed the inhibition of attachment of NUGC-4 gastric cancer cells by local treatment with phospholipids to the peritoneum in nude mice. Gastric cancer cells (1xl0(6)) suspended in either normal saline (controls) or phospholipid suspension 75 mg/kg body weight (PL75) or 150 mg/kg (PL150) were injected intraperitoneally into 90 female BALB/c nu/nu mice. The treatment groups were subdivided into animals with defined peritoneal lesions and animals without lesions. After 30 days the extent of peritoneal carcinosis and the Peritoneal Cancer Index were evaluated. Statistical analysis was performed with two factorial ANOVAs. The level of significance was adjusted according to Bonferrorni (alpha = 0.00278). During a 90-day observation period the survival rate was determined using the log rank test. After 30 days the intraperitoneal tumor volume was reduced by PL150 up to 0.6 ml (SEM 0.16) and 0.48 ml (SEM 0.09) in mice with peritoneal lesions compared to 0.9 ml (SEM 0.2) and 0.9 ml (SEM 0.1) in the control group (P = 0.04). The mean area of tumor adhesion amounted to 145 mm(2) (SEM 17) (P = 0.08) and 164 mm(2) (SEM 32.8) (P = 0.049) with peritoneal lesions after treatment with PL150 [controls: 216 mm(2) (SEM 28.5) and 245 mm(2) (SEM 29.3)]. The peritoneal cancer index was 16.4 (SEM 1.7) in the control group and 9 (SEM 1.68) with PL150 (P = 0.0002). In the subgroup with peritoneal lesions, the respective values were as follows: controls: 20.8 (SEM 0.85); PL 150:14.3 (SEM 1.07) (P = 0.0001). We found a prolonged survival rate after treatment with PL150. However, this effect was not significantly different to that seen in the control group. Treatment with PL75 had no significant influence. Phospholipids may be an efficacious and economic tool for reducing peritoneal tumor cell adhesion and consequently the development of peritoneal carcinosis after resection of gastric cancer.