Background. The CC531 tumor cells are rat colon adenocarcinoma cells. They grow in vitro forming monolayers. Inoculated intra-peritoneally, intraportally or subcutaneously they form nodules within 14 to 21 days. The tissues surrounding tumor nodule become infiltrated by host mononuclear cells. In advances stages fibrous wall forms around the nodules and central parts become necrotic. Since these is a local cellular response to the CC531 line, the idea arouse to locally immunize tissues by inoculation of non-dividing metabolically inactive tumor cells. Immunization raises memory cells and the subsequently inoculated live CC531 cells should be destroyed in a host memory response mechanism. We described previously that cells as lymphocytes and monocytes or isolated tissue cells preserved in anhydric pulverized sodium chloride (NaCl) become metabolically inactive, however, they retain their molecular structure intact (Transplantation 2006; 81:1583-1588) and can be used as immunogens. Much the same applies to the isolated tumor cells.
Aim. To immunize tissue, prior to implantation of live CC531, with the NaCl mummified (non-diving, metabolically inactive) CC531 cells and observe kinetics of growth of the implanted live CC531
Material and methods. LEW inbred rats were used. In group 1, 107 live CC531 cells were injected subcutaneously into right paw. Follow up period was 14 and 21 days. In group 2, 107 CC531 cells preserved for 7 days in pulverized NaCl were desalinated and implanted subcutaneously as in group 1. Seven days later 107 live CC531 were implanted into the same paw. In both groups at the end of the 3rd week tissues with implanted tumor cells and regional lymph nodes were harvested. Specimens were stained with H-E and monoclonal antibodies against CC531 cells, MHC class II (OX6), mononuclear cells (ED1) and W3/13' (lymphocytes). Histological evaluation included: central necrosis area (compared to whole CC531 cell occupied area), density of host cells infiltrating tumor periphery (cells/sq.cm), thickness of fibrotic wall around tumor, number of CC531 cells in cortical area of lymph nodes
Results.Topical immunization of rat paw tissues with NaCl preserved CC531 tumor cells prior to inoculation of live CC531 cells brought about: 1. Dense host cellular infiltrates and focal tumor necrosis, 2. Infiltrates composed of host ED1, OX6 and W3/13 cells seen around and within tumor foci. 3. A 50-100 ยต tihick fibrous wall formed around tumor foci. 4.Only few metastatic CC531 cells seen in cortical areas of popliteal lymph nodes.
Conclusions. The NaCl-mummified CC531 tumor cells do not proliferate after implantation, and when implanted into recipients tissues, they evoke host immune reaction resulting in necrosis of subsequently implanted live CC531 cells.