The study on the rarity of metastases in skeletal muscles and the significance of VCAM 1 in it

Objective: To establish an animal model for blood-borne metastasis of malignant tumors,and to evaluate the significance of vascular cell adhesion molecule (VCAM-1) in the rarity of metastases in skeletal muscles. Methods: 60 Wistar rats were chosen and randomly divided into two paired groups.30rats in the experimental group were injected with tumor cells (Walker 256,10⁴) through iliac artery,and paired rats in the control group were injected with the same tumor cells (10⁶,considering the damages in circulation) through tail veins.The animals in each group were sacrificed in batches (6rats each) 2hours、1day、7days、14days after the start of the procedures,or died naturally (6rats).The femur muscles and lungs were observed grossly and histiologically,the VCAM-1expressions in the microvessels in these organs were estimated meanwhile. Results: In the experimental group,tumor cells near the blood vessels in the femur muscles were rarely seen in rats (3rats in all) sacrificed 7days and 14days after the procedures,there was no definite metastase within parenchymal skeletal muscles but there are some metastases in soft tissues beside the skeletal muscles;In the control group,metastases began to form in lungs 7days after tail veins were injected with tumor cells,and were seen in the lungs of all the rats that were sacrificed 14days later or died naturally (17rats in all) (P <0.001).In the experimental group,an significant higher positive rate of VCAM-1in femur muscles were seen 7 days after iliac arteries were injected with tumor cells and thereafter (P <0.001).There was no significant difference between the positive rate of VCAM-1 in femur muscles in the experimental group and that in the lungs in the control group (P =0.5). Conclusion: The rarity of metastases in skeletal muscles,generally known in clinic,can appear in animal models.However,this rarity is not related to VCAM-1expressions in microvessels in skeletal muscles.