Vaccination with soluble low-molecular weight tumor-associated proteins suppresses chemically-induced mammary tumorigenesis in rats.

This study attempted to elucidate whether the soluble tumour-associated proteins (TAA) of 66 kDa and 51 kDa molecular weight could suppress chemically induced mammary tumorigenesis. An intragastric dose of dimethylbenzanthracene (DMBA) was administered to rats and some were simultaneously immunised with the TAA. A single dose of DMBA resulted in 38% of the rats developing mammary tumours. However, simultaneous vaccination with the TAA preparation was significantly tumour-suppressive: mortality declined from 50% to 0% (p < 0.05); survival was extended from 9.4 weeks to 13.0 (p < 0.05), and 83% of the animals remained tumour free, compared to 13% of the control animals (p < 0.05). In 33% of the immunised animals the malignant tumours regressed completely. Such vaccination was also effective, although to a lesser extent, when the carcinogen dose was doubled. Then, 33% of the immunised and 22% of the control animals remained tumour-free, the latent period of malignant transformation was extended from 10.0 to 11.7 weeks, the initial tumour-free period lasted 9.3 weeks instead of 8.3 weeks and 10% survived compared to 50% of the controls. Vaccination with the soluble low molecular-weight TAA had distinct tumour-suppressive effects on mammary gland tumorigenesis.