Analysis of mammary tumour cell metastasis and release of bound n-acetylneuraminic acid.

A tumour model consisting of the highly metastatic mammary 13762 parental line, the non-metastatic and 6-thioguanine-resistant (TgR) variant line, and two TgR revertant lines (TgRrev, TgRrevM) that were occasionally metastatic, were used to determine whether the release of N-acetylneuraminic acid (NANA) was related to tumour metastasis. For comparative purposes, the occasionally metastatic R3230AC and the nonmetastatic DMBA8 tumour lines were studied. The NANA was considered to be in bound form, because acid hydrolysis was required to release it for high-pressure liquid chromatographic analyses. Sera of animals bearing the 13762 and R3230AC tumours had high levels of bound NANA. No differences were found in serum NANA levels in animals bearing metastatic or non-metastatic R3230AC tumours. Low levels of bound NANA were found in animals bearing the other tumour lines regardless of whether metastasis occurred or not. The experiments in vitro substantiated the in vivo findings. The phenotypic expression of bound NANA shedding did not correlate well with metastatic potential of the mammary tumour line. Our analyses suggest that this phenotypic marker cannot be used as a reliable indicator of metastasis.