We studied antitumor effects of peptide extracts from plants on slowly growing mammary adenocarcinoma in CBRB-Rb(8.17)1Iem mice used as a model of breast cancer in humans. The antitumor effect of a single injection of the test peptides was evaluated by the delay of the appearance and growth of palpable breast cancer in mice over 4 weeks. Peptides from Hypericum perforatum and a mixture of Chelidonium majus L., Inula helenium L., Equisetum arvense L., and Inonotus obliquus exhibited maximum activity. Peptide extracts from Frangula alnuc Mill. and Laurus nobilis L. were less active. No antitumor effect of Camelia sinesis Kuntze was detected.

Galectins, beta-galactoside binding proteins, expressed selectively in human breast carcinoma are attractive targets to employ lectin-aimed therapeutics. We examined beta-galactoside binding potency of neoplastic cells using fluorescein-labelled synthetic glycoconjugates as probes for flow cytometry. As a result, surface beta-galactoside binding proteins/galectins were discovered on mouse mammary carcinoma cells in vitro and in vivo unlike non-malignant cells from the several tissues; and asialo-GM1 ganglioside carbohydrate part--containing probe was the most specific one. However, in liver and lung metastatic cells galectins seem to be expressed within cytoplasm and/or nuclei. Galectin expression correlated directly with aggressive tumour potential in the A/Sn transplantable model similar to findings in several human breast carcinoma cell lines. However, galectin expression was reduced during tumour progression in more aggressive forms of spontaneous BLRB mammary carcinomas like it was shown for human breast carcinoma specimens. Analysis of the histopathological data led, however, to the conclusion that galectin expression hardly might be a suitable marker of aggressiveness of heterogeneous mammary carcinomas as the observed level of galectin expression is influenced by the amount of the stroma in a tumour sample and/or probably, galectin expression inversely correlates with tumour aggressiveness during the initial and advanced steps of mammary tumour progression. We conclude that surface beta-galactoside binding proteins/galectins that are selectively expressed during mouse mammary carcinoma progression, similarly to human breast carcinomas, seem to be proper targets for asialo-GM1-vectored cytotoxics and our mouse model system might be a relevant instrument to further test novel modes of anti-breast cancer therapy.

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