Changes in tumor-specific antigen expression during passage in vitro and in vivo of newly derived methylcholanthrene-induced sarcomas of BALB/C mice

Homology of the B50 murine melanoma antigen to the Ro/SS-A antigen of human systemic lupus erythematosus and to calcium-binding proteins

B50 is a murine melanoma-associated antigen found in tight association with B700, a melanoma-specific antigen. B700-like molecules are produced by all melanomas tested to date, including those of murine, human, swine and hamster origin. We have used rabbit antibodies to B50 to determine whether B50 expression is also restricted to melanomas. The results demonstrate that B50 is a commonly occurring protein, or is immunologically cross-reactive to a commonly occurring protein; 29 of 29 cell lines tested bound anti-B50 antibodies. N-terminal amino acid sequence analysis indicates that B50 has significant homology to the Ro/SS-A antigen of human systemic lupus erythematosus and to calcium binding proteins; hence B50 is likely to be an RNA and/or calcium-binding protein.

Biochemical characterization and biologic activities of 82- and 86-kDa tumor antigens isolated from a methylcholanthrene-induced sarcoma, CII-7

Two tumor-specific antigens, with molecular weights of approximately 82 and 86 kDa, have been isolated and purified to apparent homogeneity from the methylcholanthrene-induced sarcoma, CII-7. The method of purification used was essentially that previously employed for the isolation of the 82- and 86-kDa antigens from the Meth A sarcoma and the 86-kDa antigen from mKSA sarcoma. Cytosolic fractions were subjected to hexylamine agarose chromatography, Sepharose S-300 filtration and hydroxylapatite chromatography. A final step, HPLC-DEAE chromatography, was necessary for the purification of the 82-kDa protein. Both isolated antigens retained their specific immunogenicity for CII-7 as determined by in vivo tumor rejection assays, and failed to influence the growth of other syngeneic sarcomas, CI-4, CII-10 and mKSA, which have their own unique TATA. The 82- and 86-kDa antigens appear to be distinct proteins that are well conserved in nature and may represent members of distinct families of TATA.

Characterization of a chemically homogeneous tumor antigen from a methylcholanthrene-induced sarcoma, Meth A

A tumor antigen isolated from the cytosol of a methylcholanthrene-induced sarcoma (Meth A) has been purified to homogeneity by the criteria of two-dimensional gel analysis and NH2- and COOH-terminal sequencing. The purified antigen has a mol. wt of 82,000 by SDS gel electrophoresis. However, the apparent mol. mass of the antigen was found to be 71,600 and 67,700 by gel filtration chromatography and sedimentation analysis, respectively. It is not a glycoprotein, possesses an acidic isoelectric point (6.0) and exists as dimeric and monomeric species. The dimer is not held together by disulfide bonds. The purified protein retains its ability to induce transplantation immunity in syngeneic hosts when challenged with Meth A sarcomas. Chemical analyses of the NH2- and COOH-termini gave the following sequences: NH2-PKPINVRVTTMDAELEFAIQPN and IDE(F,A)EM-COOH, respectively.

A mouse tumor-specific transplantation antigen is a heat shock-related protein

A tumor-specific transplantation antigen has been purified to homogeneity from the cytosol of a methylcholanthrene-induced tumor, Meth A. The purified antigen is highly immunogenic and specific against challenge with Meth A, providing greater than 95% inhibition of tumor growth in immunized syngeneic mice. Immunofluorescence analysis of Meth A showed that the antigen is a highly abundant cytosolic protein but that it is also present at the cell surface and, therefore, accessible to the host's immune system. The antigen consists of two polypeptide isoforms present in equimolar amounts, having similar masses (84 and 86 kDa), pI values (4.95 and 4.90), and amino acid compositions. Both are phosphoproteins, and neither is glycosylated. The NH2-terminal sequences of the two isoforms are identical except that each chain contains a portion of unique sequence. Comparison of the NH2-terminal and CNBr-fragment sequence data to the sequences of the yeast and Drosophila heat shock proteins (Hsp90 and Hsp83, respectively) reveals that 73 of 91 residues compared are identical. In addition, an anti-Meth A tumor antigen serum that defects the isoforms from a variety of tumors also immunoprecipitates proteins of identical mass and pI from both normal and heat-shocked mouse embryo cells.

The roles of two peritoneal T-lymphocyte populations in the in vivo rejection of methylcolanthrene-induced sarcoma

Two phenotypically distinct T-lymphocyte populations infiltrating the peritoneal site of active tumor rejection were found to have specific reactivity against methylcolanthrene (MCA)-induced sarcoma(s) in two separate biological assays. One, expressing a Lyt 1+2- phenotype, mediates specific delayed type hypersensitivity (DTH) reaction to the immunizing MCA tumor transplantation antigen, and the other, expressing a Lyt 1+2+ phenotype, transfers in vivo protection against the MCA tumor in Winn assay. This latter antitumor immunity was specific for individually distinct transplantation antigens of each MCA sarcoma line. In contrast, standard transplantation tests by direct (whole animal) challenge demonstrated considerable tumor cross-reactivity. These findings and the relative contributions of the two T-cell populations are discussed in terms of effector mechanism.

Isolation of a tumor-associated transplantation antigen (TATA) from an SV40-induced sarcoma. Resemblance to the TATA of chemically induced neoplasms

A tumor rejection antigen (TATA), obtained from the cytosol of a BALB/c mKSA sarcoma induced by SV40 virus, has been partially purified. This partially purified antigen is strikingly immunogenic against mKSA, providing more than 90% inhibition of growth at levels of 10-30 micrograms. This antigen preparation does not protect against challenge with another SV40-induced BALB/c sarcoma VLM which, however, shares a group-specific TATA with mKSA. The antigen also does not immunize against challenge with the methylcholanthrene-induced sarcomas of BALB/c mice, Meth A, CI-4, CII-7 and CII-10, each of which has its own unique TATA. Binding assays, using ELISA, failed to detect any SV40 antigen in the antigen preparation despite the fact that the large T antigen of SV40 (or fragments of it) constitutes the immunodominant TATA of mKSA.

Enhancement of tumor growth in mice: evidence for the involvement of host macrophages

Intratumor host cells of methylcholanthrene-induced fibrosarcoma(s) were shown to enhance the in vivo outgrowth of syngeneic homologous tumors (MC1A, Mc2A, Mc2B) but not two heterologous T-lymphomas (EL4 and TLX9) in the Winn adoptive transfer assay. This enhancing activity was not restricted only to the latent period of tumor growth but was also observed during the period of active in vivo tumor proliferation. Tumor enhancement was mediated by a population of cells adherent to nylon wool and glass and insensitive to irradiation (with 850 rads) or to treatment with anti-Thy 1.2 serum and complement. Macrophages from peritoneal exudates of normal mice, used as control host cell population, showed similar tumor-enhancing activity. These findings suggest that tumor infiltrating host cells, predominantly macrophages appear to be the cell type responsible for tumor enhancement and active promotion of tumor growth (in vivo).

Generation of crossreacting tumor antigens in ascitic derivatives from murine methylcholanthrene-induced sarcomas

Sarcomas induced by the chemical carcinogen 3-methyl-cholanthrene (MC) in pedigreed BALB/c strain mice were studied for the existence and characteristics of tumor-specific antigens that induce protective immune defenses in syngeneic mice (TATA). It was found that each of the neoplasms expressed a unique immunogenicity that was stable and heritable over a period of 125 transfers in vivo. Common or crossreacting TATA were not observed. When converted to an ascitic form, two of these sarcomas, CII-7 and CII-10, were found to be crossreactive, presumably sharing TATA with each other and with the MC-induced sarcoma Meth A. Two other neoplasms converted to the ascitic form, however, retained their unique TATA. Although the precise nature of unique and crossreacting TATA is not known, it is hoped that recent investigations in the purification of TATA of chemically induced neoplasms will shed light on the mechanisms responsible for the diversity of tumor-specific antigens.

Selective increased tissue histamine levels in tumour-bearing rodents

Histamine levels increased in the fundus of mice bearing a primary 3-methylcholanthrene-induced fibrosarcoma, and in the ventral skin, skeletal muscle and rumen of rats bearing a D.M.B.A. induced mammary adenocarcinoma; they did not increase in the tissues of mice bearing a McC3-1 fibrosarcoma (38th passage) or a Lewis lung carcinoma before the appearance of metastasis, but an increase in histamine levels was observed in dorsal skin, ventral skin and fundus, after the appearance of metastasis.

Purification and biochemical properties of tumor-associated transplantation antigens from methylcholanthrene-induced murine sarcomas

A tumor-associated transplantation antigen with an apparent molecular weight of 75,000 has been isolated from the cytosol of the BALB/c methylcholanthrene-induced sarcoma, Meth A. The antigen was purified either by preparative electrophoresis in the presence of NaDodSO4 or by immunoaffinity chromatography after hexylamine agarose chromatography, gel filtration, and hydroxylapatite chromatography. The 75-kilodalton (kDal) protein prepared by either of these methods effectively primed BALB/c mice to reject the Meth A tumor; such priming provided no protection against challenge by other independently derived sarcomas of BALB/c origin. A second protein, also 75 kDal, was isolated from the cytosol of the recently derived methylcholanthrene-induced sarcoma CI-4 by essentially the same chromatographic scheme. This protein also was immunogenic in the tumor rejection assay and provided protection only against CI-4 challenge. The antigens purified from the Meth A and CI-4 sarcomas appear to be closely related proteins. Both of them can be purified from the cytosol fraction and can be recognized by a rabbit antiserum prepared against the Meth A 75-kDal protein. The two proteins have approximately the same molecular weight, have similar but not identical amino acid compositions, and differ in their chromatographic behavior on hexylamine agarose and hydroxylapatite as well as in their isoelectric points. These results indicate that the individually specific transplantation antigens found in chemically induced sarcomas may be the products of a single multigene family or somatic derivatives of a single gene.

Tumor and histocompatibility antigen interaction: direct visualization by a double-label bridging technique for immuno-electron microscopy

The nature of the interaction between the Ib tumor-associated surface antigen (Ib-TASA) and the Dk and Kk (Dk/Kk) regions of the major histocompatibility complex on the surface of line Ib lymphocytes was evaluated by immuno-electron microscopy using a double-label bridging technique. Quantitation of antigenic sites by direct counts showed 44% of the Ib-TASA sites coincident with Dk/Kk antigens. This is greater than the predicted random interaction of two independent cell surface determinants suggesting an associative interaction, i.e. 'altered-self' antigen. The remaining 56% of the Ib-TASA sites were in a non-associative mode. On the basis of data presented here, we postulate that the interaction between 'self'- and 'non-self' antigens is not an 'all or none' phenomenon.

possible role of a retrovirus in the expression of tumor-specific antigens of the Meth A sarcoma

The serologically defined tumor-specific surface antigen (TSSA) of the chemically-induced BALB/c Meth A sarcoma, highly restricted to one of 20 sarcomas of BALB/c origin, has been detected on a Moloney murine sarcoma virus (Mo-MuSV)-transformed BALB/c 3T3 cell lines, designated IIA(v). The immunogenicity of the IIA(v) cell in tumor-rejection assays was specific for the Meth A sarcoma, supporting the evidence for a close relationship between the TSSA and the tumor-associated transplantation antigen (TATA) of this tumor. Infection of SC-I cells with retroviruses present in cultured filtrates of IIA(v) cells resulted in Meth A antigen expression. The retroviruses associated with Meth A antigen expression have been tentatively identified as replication and/or transformation-defective XC- MuLV. The possible roles of Mo-MuSV and cellular genes of the BALB/c strain of mice in the expression of the Meth A antigen are discussed.

High-frequency cotransfer of the transformed phenotype and a tumor-specific transplantation antigen by DNA from the 3-methylcholanthrene-induced Meth A sarcoma of BALB/c mice

We transformed BALB/3T3 mouse cells with cellular DNA extracted from the Meth A sarcoma, a 3-methylcholanthrene-induced tumor of BALB/c mice, and asked whether foci arising in the transfection possess the previously defined Meth A tumor-specific transplantation antigen (TSTA). Five of eight foci selected from one experiment possessed Meth A TSTA. DNA extracted from one of the five TSTA-positive clones was used in secondary rounds of transfection transformation. Four out of five foci tested from the secondary transfections possessed Meth A TSTA. These results suggest that in the Meth A sarcoma a transforming gene and a genetic determinant of TSTA are intimately related: they may be identical or very closely linked; alternatively, a particular transforming gene might induce the expression of a particular TSTA. Another possible explanation for these results is that the cotransfer of certain cellular genes by DNA transfection is considerably higher than predicted from the limited studies presently available.

Some immunogenic acid biochemical properties of tumor-associated transplantation antigens (TATA) obtained in soluble form or solubilized from two methylcholanthrene-induced sarcomas, Meth A and CI-4

The subcellular distribution of the tumor-associated transplantation antigens (TATAs) of two highly immunogenic methylcholanthrene-induced sarcomas, Meth A and CI-4, were compared. Most of the TATA of CI-4 was found in the soluble fraction (cytosol) of the cell while the TATA from Meth A was variably distributed between the membrane and cytosol. The soluble fraction TATAs from both tumors were very immunogenic and their strong immunity could not be influenced by administering antigen in a variety of protocols that altered the immune response in other systems. The soluble fraction and membrane-associated TATAs from both tumors could be specifically bound to liposomes in reconstitution experiments and the antigenicity of all of the TATAs was significantly enhanced when they were incorporated into these artificial membranes.

Expression of alien minor histocompatibility antigens distinct from tumor-specific transplantation antigen on a murine fibrosarcoma

The fibrosarcoma ST2, induced by 3-methylcholanthrene in BALB/c (H-2d) mice, also expressed alien histocompatibility antigens of the C3Hf and B10 background not encoded by the MHC. To examine the relationship between these alien, minor antigens and the tumor-specific transplantation antigen (TSTA) of the tumor, in vivo immunogenicity test were performed in BALB/c mice and in hybrids between BALB/c and C3Hf (H-2k), C3H.OH (H-2o2), C3H.SW (H-2b), BALB.K (H-2k), B10.BR (H-2k), and B10.D2 (H-2d) mice. A significant loss of TSTA immunogenicity was found in (BALB/c x C3Hf) and in (BALB/c x C3H.OH)F1 animals and, to a lesser extent, in (BALB/c x C3H.SW)F1 mice as compared to the immunogenicity of the tumor in BALB/c mice. Immunogenicity tests with ST2 in BALB/c x (BALB/c x C3Hf) or in BALB/c x (BALB/c x B10.D2) backcross mice, respectively, revealed that half of the BALB/c x (BALB/c x C3Hf) and 97% of the BALB/c x (BALB/c x B10.D2) animals were able to mount an immune response to ST2. To see whether the loss of TSTA immunogenicity in (BALB/c x C3Hf) was due to common determinants shared between TSTA and alien non-H-2 C3Hf antigens or to a genetically linked low responsiveness to TSTA introduced by C3Hf and C3H.OH strains, BALB/c mice were immunized with normal tissues of some BALB/c x (BALB/c x C3Hf) backcross, anti-ST2 resistant mice. Normal tissues of anti-ST2 resistant, dd and dk typed backcrosses were able to immunize BALB/c mice against a challenge of an otherwise lethal dose of ST2 cells. Some but not all BALB/c x (BALB/c x B10.D2) anti-ST2 resistant donors had tissues able to immunize BALB/c hosts aginst the ST2 growth. Since resistance to tumor growth and expression of minor "alien" antigens shared with the tumor segregate independently, we concluded that alien, minor C3Hf and B10 antigens of the BALB/c sarcoma ST2 are distinct from the TSTA of this tumor.