[Tumor-regressive potency of soluble factors released from tumor-immune cells]

Liposome-encapsulated soluble factors, which were prepared from activated peritoneal exudate cells or spleen cells by stimulation with tumor-associated antigens and Con A, successfully regressed line 10 tumors transplanted into strain 2 guinea pigs. By intralesional administration of these soluble factors, a tumor-regressive potency of 40-50% was attained. No direct cytotoxic activity of these factors was indicated against line 10 tumor cells in vitro. It is therefore postulated that liposome-encapsulated soluble factors activate immune cells which have accumulated around tumor cells which eventually leads to regression tumor.