Immunisation with a nonapeptide expressed in human tumors is able to reduce tumor growth in a rat experimental model.

P. Sinibaldi Vallebona1, G. Rasi2, P. Bernard2, P. Pierimarchi2, F.G uadagni3, E. Garaci1

1University of Tor Vergata, Roma,Italy 2Istitute of Neurobiology and Molecolar Medicine, CNR, Italy 3Cancer Istitute Regina Elena, Rome, Italy

AIM The nonapeptide RTNKEASIC was shown to be expressed both on human colorectal cancer and Non Small Cell Lung Cancer (NSCLC) and on experimental colorectal cancer in syngeneic BD-IX rats. Aim of the study was to verify if the immunisation with this peptide is able to induce a cellular immune response (CTL) and to rise an antitumoral activity. METHODS DHD-K12 cells were injected subcutaneously in the cervical region of 12 BDIX rats. Synthetic peptide was injected intradermally into 6 sites on the animal's back in Freunds Complete Adjuvant (FCA) for the first immunisation and in Freunds Incomplete Adjuvant (FIA) for the further booster. Immunisation was repeated every 7 days for 8 times, starting the day after tumor injection. Control group was injected with FCA or FIA without peptide. Tumor growth was checked once a week. CTL activity was measured by a 4hr-LDH assay. RESULTS Tumor were detectable in all animals after 14 days and a significant reduction was observed up to day 119 (p< 0.001). The tumor size (mm3) ranged from 0.083 ± 0.14 vs 0.262 ± 0.23 (day 14) to 6.952 ± 5.49 vs 17.407 ± 1.4 (day 119). CTL activity was also significantly (p < 001)enhanced over the control 42 days after first immunisation. CONCLUSIONS The peptide RTKNEASIC is able to induce both CTL and anti-tumor activity in this experimental model. This is relevant to the future cancer vaccine development since this peptide was shown to be an epitope expressed in human NSCLC and in colorectal cancer.

KEY WORDS: colorectal cancer, BD-IX rats, DHD-K12 cells.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Immunotherapy.