Protective tumor immunity induced by potassium chloride extracts of guinea pig hepatomas

Undefined-antigen vaccines

Our knowledge of the immune system and how it interacts with tumor cells continues to grow. With each advance in basic science comes a new opportunity to develop an effective treatment strategy. Many such opportunities have arisen in the past few decades and this chapter has attempted to describe how these new advances have been combined with a variety of undefined cellular antigen preparations in an attempt to develop effective cancer vaccines. None of the strategies described in this chapter have been sufficiently effective to become part of standard therapy. However, the approaches tested have generally been well-tolerated by patients with advanced cancer and the evidence of immunologic activity and examples of impressive clinical activity in a wide variety of malignancies, suggests that these strategies can be the building blocks upon which new advances are added and effective treatments developed.

Effect of a synthetic adjuvant for inducing anti-tumour immunity

An acylated derivative of muramyl dipeptide (MDP), 6-O-(2-tetradecyl-hexadecanoyl)-muramyl-dipeptide (B30-MDP) is a strong adjuvant effective in inducing cell-mediated immunity. We used B30-MDP as an adjuvant for induction of anti-tumour immunity. Guinea-pigs which were injected repeatedly with a mixture of X-ray-treated leukaemic cells and B30-MDP dissolved in phosphate buffered saline resisted a challenge of leukaemia cells and showed no sign of leukocytosis. The immunity induced was tumour-specific and retained for more than 100 days. These results suggest that B30-MDP is useful as a simple but potent immunotherapeutic tool.

Changing tumour antigen expression in metastatic hepatocellular carcinoma cells of the guinea pig

Hepatocellular carcinoma cells (Line-10), obtained from ascitic fluid after diethylnitrosamine treatment of Sewall Wright strain-2 guinea pigs, produce solid (primary) tumours, lymph-node and lung metastases and malignant ascites when reinjected into animals of the same strain. Monoclonal antibodies were raised against the tumour cells by immunizing BALB/c mice with viable ascitic hepatocellular Line-10 tumour cells. Three hybridomas producing anti-Line-10 monoclonal antibodies were selected for further studies (10TL1, 10TL40 and 10TL43) and compared with monoclonal antibodies against intermediate filament keratins. The anti-Line-10 monoclonal antibodies did not cross react with Line-1 hepatocellular carcinoma cells, nor with normal guinea pig hepatocytes. When ascitic Line-10 cells form high papillary projections on the peritoneal surface, they significantly reduced their antigen expression of 10TL40 and of 10TL43 defined antigens, while the expression of 10TL1 defined antigens remained unaltered. Invading Line-10 cells in the deep submesothelial stromal tissue, however, lost reactivity with MoAb 10TL43 but not with the MoAb's 10TL40 and 10TL1. The antigens on lung- and lymphnode metastases remained largely unaffected. The reactivity with MoAb's 10TL40 and with 10TL43 was also lost upon prolonged culturing of Line-10 cells. The reactivity of Line-10 and Line-1 cells with all monoclonal antibodies against keratin filaments remained unaltered. Line-1 cells could be distinguished from Line-10 cells by the absence of any reactivity with the MoAb's 10TL1, -40, -43, but also by the fact that 100% of the Line-1 cells were positive with antibodies against keratins 5/8, 18, and 7.(ABSTRACT TRUNCATED AT 250 WORDS)

A synthetic adjuvant effective in inducing antitumor immunity

Guinea pigs which were injected repeatedly with a mixture of a 3M KCl extract of line 10 tumor and 6-O-(2-tetradecyl-hexadecanoyl)-muramyl-dipeptide (B30-MDP) rejected a tumor graft of line 10. Such an adjuvant effect of B30-MDP was also demonstrated when X-ray-treated line 10 cells were mixed with B30-MDP dissolved in phosphate-buffered saline and inoculated into the animals.

Postoperative immunization with peanut agglutinin-binding glycoprotein from Lewis lung carcinoma in mice

The effects of postoperative immunization with purified tumor-associated antigens on the development of lung metastases following excision of the Lewis lung carcinoma (3LL) were investigated. Soluble tumor-associated antigens were isolated from 3LL cells by detergent solubilization and purified by affinity chromatography on peanut agglutinin (PNA)-agarose. The immunization with subcutaneous injections of PNA-binding glycoproteins (PNA receptors) at the early phase following excision of primary footpad tumors of 3LL resulted in a significant decrease in incidence and size of lung metastases. The delayed immunization, however, failed to suppress the development and growth of metastatic lung tumors after surgery. The suppression in postoperative development of lung metastases was found to depend on the scheduling of immunization following local tumor excision. Splenectomy performed simultaneously with amputation of the tumor-bearing leg completely abolished the decrease in the development and growth of postoperative lung metastases in immunized mice. The involvement of the lymphoid system in the control of metastatic tumor growth was also confirmed in an in vivo tumor neutralization assay utilizing the spleen cells.

The effect of immunotherapy with extracted tumor antigens on sinecomitant immunity

The fate of hosts after tumor resection depends upon the level of their sinecomitant immunity, which can destroy residual neoplastic cells. In addition, active specific immunotherapy can stimulate the resistance of mice incompletely resected of large tumors and therefore destined to develop recurrent disease. The studies presented herein, assessing host resistance by in vivo tumor challenge and an in vitro growth inhibition assay (GIA) measuring the effect of splenic lymphocytes on 3H-thymidine incorporation into monolayers of sarcoma cells, revealed an antagonistic relationship between sinecomitant immunity and tumor antigen immunotherapy. Treatment of hosts bearing high levels of endogenous sinecomitant immunity with Fraction 15 pI 5.95 partially purified from 3 M KCl extracts by preparative isoelectric focusing, decreased their resistance to tumor challenge and the capacity of their spleen cells to perform in the in vitro GIA. When sinecomitant immunity was not demonstrable, therapy with tumor antigen induced host resistance. If therapy was delayed until sinecomitant immunity had naturally waned, hosts displayed improved resistance toward secondary challenge. These findings suggest that not only does antigen therapy effect tumor resistance by a mechanism independent of sinecomitant immunity, but also these two mechanisms are mutually antagonistic. Therefore, the design of active specific immunotherapy protocols utilizing tumor antigens may depend on the level of the host endogenous sinecomitant resistance.

Purification of immunoprotective tumor antigens by preparative isotachophoresis

Tumor-specific transplantation antigens (TSTA) were purified from 3 M KCl and butanol extracts of C3H/HeJ 3-methylcholanthrene-induced fibrosarcomas by preparative isotachophoresis (pITP). Fractions from pITP which reacted with antisera to TSTA preparations in an enzyme-linked immunospecific assay were tested in vivo for induction of resistance to the growth of transplanted tumor cells. Isotachophoresis of crude 3 M KCl extracts yielded TSTA that was immunogenic at doses between 17 and 124 micrograms. Isotachophoresis of TSTA partially purified from crude 3 M KCl or butanol extracts by preparative isoelectric focusing (pIEF) of 3 M KCl and butanol extracts yielded TSTA that was immunogenic over a two-fold log dose range. As little as 10 ng purified TSTA reduced tumor growth by 50%. Tumor growth reduction was specific, and immunized animals survived longer than non-immunized controls. A purification of 10,000-fold over crude 3 M KCl extracts and 2,500-fold over crude butanol extracts was obtained. These results suggest that TSTA from murine tumor cells is preparatively purified by following extraction with pIEF and then pITP.

Immunogenicity of cellular and acellular antigen preparations from a methylcholanthrene-induced mouse sarcoma

Inbred mice were immunized with various cellular and subcellular preparations from a syngeneic, methylcholanthrene-induced sarcoma to induce transplantation immunity against a subsequent challenge of viable cells from the same tumor. Only with conventional immunization procedures using radiation-attenuated tumor cells or viable tumor cells in admixture with bacillus Calmette-Guérin was transplantation immunity obtained. Neither native soluble tumor extracts prepared using several extraction methods, nor cross-linked preparations of these extracts gave rise to transplantation immunity. With few exceptions, however, the immunizing preparations resulted in the production of tumor-specific humoral antibody. The manner in which tumor antigens are presented to the host as well as the experimental system (animal strain; tumor) used appear to play an important role in the development of transplantation immunity against tumors.

Solubilization and partial characterization of a tumor-rejection antigen from an ultraviolet light-induced murine tumor

Tumor rejection antigen (TRA) of an ultraviolet-light-induced murine skin tumor was solubilized, fractionated and partially characterized. Subcellular fractions were prepared by differential centrifugation of tumor cells that had been ruptured via nitrogen cavitation. Only the 110,000-g membrane fraction induced significant tumor protection, as determined by in vivo immunization and challenge assays. Extraction of the membrane fraction with 3 M KCI resulted in solubilization of material that could induce in vivo tumor-rejection immunity. Both the membrane fraction and soluble extract had a limited effective dose range. The KCI extract was separated on a Sepharose, CL-6B column in the presence of 6 M guanidine-HCI. Only one of five fraction pools (molecular weight range of 76,000-127,000 daltons) was immunogenic. It contained at least eight protein bands by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), but no lipid components. This immunogenic Sepharose fraction was chromatographed on a Sephadex G-150 column. Each of the four Sephadex fraction pools was immunogenic. One protein component was common to each of those fractions. It migrated as a single 76,000-dalton band on SDS-PAGE and contained [14C]-leucine and [3H]-glucosamine that had been incorporated during cell growth. These results suggest that the TRA of this tumor is a 76,000-dalton glycoprotein.

Reproducibility and relation to specific and non-specific anti-tumor resistance of the tumor "sneaking through" phenomenon

The reproducibility and immunological specificity of the tumor "sneaking through" phenomenon and enhancement of tumor growth were studied in syngeneic and random-bred Syrian hamsters by means of a quantitative modification of the transplantation test. After primary challenge the phenomenon was neither observed in normal animals nor in animals effectively immunized against tumor. However, it was regularly observed in some "immune" animals after secondary challenge. In primary challenge of animals "sneaking through" phenomenon was most often observed in animals pretreated with large doses of heat-inactivated tumor cells. This characteristic could not be transferred with serum of pretreated animals. In contrast to specific tumor immunity, the "sneaking through" pbenomenon appeared to be immunologically non-specific. This was observed in cross-transplantation tests with tumor cells bearing different TSTAs. Thus, TSTA is not an inducer and apparently not a target for a response leading to enhancement of tumor growth in pretreated hamsters. Experiments demonstrating enhanced tumor growth in pretreated animals at the same time demonstrate two other possibly more essential findings: (1) normal animals are naturally resistant to transplantation of 1 to about 1 x 10(3) (or more) tumor cells; and (2) this resistance can be totally abrogated by the pretreatment of normal animals with tumor cell preparations. The preliminary data demonstrate that abrogation of natural anti-tumor resistance in adult hamsters subsequently inoculated with SV40 leads to rapid development of primary tumors in such animals. The development of specific anti-tumor immune response in animals treated with inactivated tumor cell preparations was also studied. Significant non-specific inhibition of sponse in Syrian hamsters treated with inactivated syngeneic tumor cells was observed. The data obtained are considered to demonstrate two anti-tumor defense systems in the animal, i.e., non-specific natural resistance and specific anti-tumor immunity. The first seems to be responsible for elimination of low numbers of tumor cells in the normal organism and also to be esseitial for effective induction and functioning of the specific anti-tumor immunity.

Dissociation of anti-tumor immune responses in rats immunized with solubilized tumor-associated antigens from a methylcholanthrene-induced fibrosarcoma

Soluble tumor antigens were prepared from chemically-induced rat fibrosarcoma KMT-17 cells by various methods [Na-deoxycholate (DOC), 3 M-KCI extraction, and crude membrane preparations by mechanical disruption]. Soluble tumor antigens prepared by DOC extraction (DOC-STA) could be detected by a radioisotopic footpad assay (FPA) and they showed the strongest antigenic activity in KMT-17 immune rats. Anti-tumor immune responses in rats previously immunized with DOC-STA were measured by FPA, Winn assay, and transplantation resistance. Significant responses detected by the FPA and Winn assay were demonstrated in rats immunized with DOC-STA. However, rats previously immunized with DOC-STA showed a significant enhancement of tumor growth when challenged with KMT-17 cells. This enhancement was specific for the tumor line used. Normal rats which received adoptive transfer of thymus and spleen cells from rats immunized with DOC-STA produced specific enhancement of tumor growth as compared with non-treated rats. Administration of cyclophosphamide before immunization with DOC-STA abrogated the enhanced tumor growth in the host. These results suggest that immunization with soluble tumor antigens specifically enhanced tumor grwoth by the induction of immunosuppressor cells. Dissociation between the anti-tumor immunity detected by the FPA and Winn assay and the enhanced tumor growth detected by transplantation resistance in rats immunized with DOC-STA is discussed.

Induction of tumor resistance with BCG-associated tumor antigen

Soluble material enriched in tumor-associated antigen was prepared by affinity chromatography from a KCl extract of the chemically-induced D-23 rat hepatoma. Microgram quantities of the above material bound spontaneously to living BCG when the two were incubated briefly in vitro. When injected into normal syngeneic rats, the BCG-associated tumor antigen induced a measure of resistance against challenge with D-23 tumor cells. Peritoneal exudate cells (PEC) obtained from such actively immunized subjects were able to suppress the growth of D-23 tumor cells at a test site in muscle. In contrast, immunization with either BCG alone, tumor protein alone, or tumor protein admixed with BCG in circumstances designed to impede association of the protein, failed to provoke the formation of tumor suppressor PEC. The results encourage of the belief that binding of tumor antigen to BCG favors the induction of a cell-mediated tumor suppressive response.

Immunogenicity of solubilized tumor antigen extracted from P1798 murine lymphoma cells or isolated from tumor-bearer ascites fluid and reactivity with anti-thy-1.2 antiserum

Solubilized antigen was prepared from P1798 lymphoma cells by sonication, 3 M KCI extraction, or isolated from the ascites fluid of syngeneic tumor-bearing BALB/c mice. Antigen was detected and quantitated by its ability to block activity of anti-P1798 serum raised in syngeneic mice, as assayed by cytotoxic and indirect immunofluorescence tests. It was established that the reaction was immunologically specific as the P1798 antigen did not inhibit the binding to L1210 lymphoma cells of antisera raised against L1210 in syngeneic DBA/2 or allogeneic BALB/c mice. Vaccination of BALB/c mice with different subcellular fractions of sonicated antigen or with ascites fluid resulted in protection against a live P1798 challenge with results comparable to those obtained using iodoacetamide-modified tumor cells. Solubilized antigen prepared by each of the three methods eluted from a Bio-Gel A5m agarose column exclusively in an early peak that had a molecular weight estimated to be greater than 2 X 10(6). This column-fractionated antigen was shown to cross-react with antiserum raised against Thy-1.2 antigen, which is present on P1798 cells. The purified P1798 antigen sedimented at 200,000 g and was shown to protect syngeneic mice in immunoprophylactic tests.

Influence of cell-free tumour-associated antigen preparations on the development of immunity to chemically induced rat tumours

Inbred rats were treated with extranuclear tumour membrane fractions or 3 M KCl-solubilized extracts of two antigenically distinct 3-methylcholanthrene-induced sarcomas, Mc7 and Mc57. The rats developed tumour-specific humoral antibody responses, but were not immune to tumour challenge. Moreover, they were unresponsive to subsequent immunization with irradiated tumour grafts, this effect being immunologically specific for the tumour from which the cell-free extracts was derived. In vitro studies revealed a depressed state of cell-mediated tumour immunity in animals inoculated with cell-free tumour extracts, and this was associated with the presence of serum inhibitory factors and suppressor lymphoid cells which abrogated the cytotoxic effect of sensitized lymphoid cells in vitro. It is postulated that the development of an inappropriate immune response due to the effect of tumour antigen during the induction phase of tumour immunity may be relevant to the immunobiology of tumour-bearing hosts.