Tumor‐associated and embryonic antigens in soluble fractions of a chemically‐induced rat colon carcinoma
Authors: Steele G. , Sjögren H. O. , Price M. R. 
Published: February 2007

Soluble intracytoplasmic protein fractions and solubilized tumor membrane preparations produced by 3 m KCl or papain treatment were isolated from a 1,2 dimethylhydrazine‐HC1 (DMH)‐induced rat colon carcinoma, DMH‐BU 1. Solubilized preparations were fractionated by DEAE cellulose and Sephadex G200 column chromatography. Crude extracts and fractionated materials were tested for their ability to inhibit the cytotoxicity of lymph‐node cells (LNC) from rats bearing isografts of an N‐methyl‐N‐nitro‐N‐nitrosoguanidine (NG)‐induced colon carcinoma, NG‐W1. Crude extracts and all but one of the fractions possessed common rat colon carcinomaassociated antigens. None of the soluble preparations altered the cytotoxicity of LNC immune to polyoma‐virus‐induced sarcoma on polyoma target cells. Crude extracts and fractions were tested for their ability to inhibit the in vitro cytotoxicity of LNC harvested from multiparous Wistar/Furth females on rat fetal lung and fetal colon target cells. In blocking assays performed by incubating the soluble preparations with LNC on the target cells for the duration of the test, crude extracts and seven of the 11 fractions significantly inhibited LNC cytotoxicity on rat fetal lung target cells. It is postulated that these fractions contain embryonic antigen (EA). Three of these seven fractions were tested for their ability to block at the target‐cell level and were found negative. However, upon adding to the fractions either FKe100 (presumptive fetalkidney‐specific antibody) or FGe100 (presumptive fetal‐gut‐specific antibody), blocking of LNC‐mediated cytotoxicity was demonstrated at the target‐cell level. Neither FKe100 nor FGe100 alone blocked when tested at the target‐cell level. Complexes which blocked the cytotoxicity of LNC from multiparous females on fetal colon target cells did not alter the cytotoxicity of polyoma sarcoma‐immune LNC on sarcoma target cells. A single fraction, No. 19, was incubated with FWe100 (fetal widespreade100, presumptive fetal kidney, fetal heart and fetal‐lung‐specific antibody) in an attempt to form antigenantibody complexes with most of the widespread EA. Formed complexes and excess FWe100 were separated from the remaining No. 19 antigen by ultrafiltration. The filtrate, S‐111, was expected to contain fetal‐gut‐specific antigen. From the retentate, containing FWe100‐widespread EA complexes and excess FWe100, high molecular weight and low molecular weight components were separated. The low molecular weight filtrate, S‐112, was expected to contain widespread EA. S‐111 and S‐112 were tested for their ability to inhibit the cytotoxicity of LNC from multiparous females on fetal lung and fetal colon target cells. S‐111 inhibited the LNC‐mediated cytotoxicity only against rat fetal colon target cells while S‐112 inhibited only multiparous rats' LNC cytotoxicity against fetal lung targets. Neither S‐111 nor S‐112 altered the cytotoxicity of polyoma sarcoma‐immune LNC on sarcoma target cells. It is postulated that fraction No. 19 contains both widespread EA (S‐112) and gut‐specific EA (S‐111).