Growth of Transplantable Cancer in Rats previously injected with Placental Tissue

AN antigen in malignant and embryonic tissues capable of retarding the growth of a transplantable human tumour ( HS 1 ) in rats has recently been described by Buttle et al. 1 . Seven days after injecting a variety of human tumours and normal adult and fœtal human tissues into weanling rats, they challenged the animals with HS 1 and cortisone. Significant inhibition of tumour growth was produced by prior injection of homogenates of HS 1 , sarcomata and a variety of normal fœtal tissues, especially spleen, whereas normal adult plasma and muscle had little if any effect. Buttle et al. attributed these findings to a labile antigen, destroyed by freezing and thawing, present in high concentration in embryonic and malignant tissue, and related to a high rate of cellular division in those tissues.