Vaccination with a synthetic nonapeptide expressed in human tumors prevents colorectal cancer liver metastases in syngeneic rats

Abstract

In previous studies, the antigen CSH-275 (RTNKEASIC) was found expressed in tissue specimens from colorectal cancer but not in normal colonic mucosa. It was also naturally expressed in the DHD-K12 experimental colorectal cancer in BDIX rats. In this study, we describe the effect of vaccination with the synthetic nonapeptide CSH-275 in preventing tumor growth in a model closely mimicking the clinical situation of liver metastases, after surgical resection of primary colorectal cancer. A vaccination protocol using CSH-275, conjugated with complete or incomplete Freund's adjuvant, was carried out to determine the effect in preventing the progression of liver metastases induced by DHD-K12 cells injected in the splenic vein (preventive vaccine). An additional vaccination procedure was carried out to determine the effect on s. Key words: cancer vaccine; peptide; liver metastasisThe identification of tumor antigens recognized by cellular or humoral effectors of the immune system has opened new possibilities for cancer therapy. One of the major applications of cancer antigens is the cancer vaccine. The molecular definition of several tumor antigens has opened the possibility of devising specific vaccination protocols based on the use of peptides, 1-5 and synthetic peptides may be particularly advantageous. 6 -8 A large number of clinical trials have demonstrated the feasibility of antitumor vaccinations and active immunotherapy with tumor-specific peptide vaccines. 4,9,10 Results are, however, variable: some tumors are easily rejected, whereas others escape destruction by the immune system. 11-14 This is probably due to the marked differences in the degree of immunogenicity between different tumors and the fact that colorectal cancer is regarded as refractive to conventional T-cell therapies. 15,16 Candidate immunodominant tumor antigens, providing the bases for antigen-specific vaccines, have been identified only for a limited number of tumors, such as melanoma and virus-associated tumors, 1,17,18 though a relevant number of tumor antigens have been characterized. 19,20 Moreover, in the majority of cases, tumor antigens are tumor-associated (TAA) rather than tumor-specific (TSA). 5,18,19 Therefore, the identification of specific epitopes remains one of the major problems in developing a vaccine approach, especially for epithelial tumors. 7,18 An ideal cancer vaccine should induce specific cytolytic immune activity against molecular targets expressed only on tumor cells, thus avoiding any damage to nonneoplastic cells.In previous studies, we demonstrated expression of the nonapeptide epitope CSH-275 (RTNKEASIC) in tissue specimens from colorectal cancer, while normal colonic mucosa was negative. CSH-275 expression was also correlated with the various stages of human colorectal cancer transformation. 21 Subsequently, the CSH-275 epitope was found to be constitutionally expressed in DHD-K12 tumor cells, 22 which is an immunogenic rat colorectal carcinoma cell line. 23 Injection of DHD-K12 cells in the splenic vein of syn...

Evaluation of antigen specific recognition and cell mediated cytotoxicity by a modified lysispot assay in a rat colon carcinoma model

“…The synthetic nonapeptide antigen, CSH-275, was previously used in a vaccination protocol and gave proof of the induction of an antitumour activity as elicited by the vaccination [17]. By the ELISPOT assay illustrated in Figure 1 we have further demonstrated the specific recognition of this nonapeptide, epitope constitutionally express in DHD-K12 cells…”

“…DHD-K12 cells naturally express a tumour-associated antigen that induces specific cytotoxic responses in immune competent syngeneic animals [16,17]. The synthetic nonapeptide antigen, CSH-275, was previously used in a vaccination protocol and gave proof of the induction of an antitumour activity as elicited by the vaccination [17].…”

“…The synthetic nonapeptide antigen, CSH-275, was previously used in a vaccination protocol and gave proof of the induction of an antitumour activity as elicited by the vaccination [17]. These data demonstrate that CSH-275 is full recognized by ex vivo lymphocytes from DHD-K12 primed rats and since CSH-275 is a major epitope identified on the TLP (Tumour Liberated Proteins) isolated from human lung, colon and breast cancer [18-20] it is evident the importance of this antigen as a potential target for new diagnostic and/or therapeutic approaches to human cancer.…”

“…The CSH-275 is present in tissue specimens from colorectal neoplasia but not in the normal mucosa of BDIX rats. The inoculation of CSH-275 peptide in tumour-harbouring rats induces a significant increase in CTLs activity against autologous DHD-K12 cells [17]. In addition, this nonapeptide is a major epitope identified on the Tumour Liberated Proteins (TLP) isolated from human colorectal cancer as well as in human lung and breast tumours [16-20].…”