Abstract
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.
Highlights
The shedding of cell-surface components may play an important role in the process of metastasis
We recently reported the isolation of a 6thioguanine-resistant cell line from the 13762 mammary adenocarcinoma that is much less tumourigenic and unable to metastasize in normal rats (Ramshaw et al, 1982)
HPLC analysis was used to quantitate the levels of bound N-acetylneuraminic acid (NANA) released in specimen hydrolysates. We show both in vitro and in vivo that shedding of bound NANA did not correlate to the metastatic potential of the mammary tumour lines
Summary
The shedding of cell-surface components may play an important role in the process of metastasis. Tumour cells seem to have an increased content of sialic acid on cell surface membranes (Alhadeff & Holzinger, 1982; Black, 1980; Huggins et al, 1980) and such bound sialic acid has often been detected in the serum of tumour-bearing hosts and in spent cell-culture medium (Bemacki & Kim, 1977; Grimm et al, 1976; Kloppel et al, 1977; Silver et al, 1979). From these studies it is suggested that shedding of bound sialic acid may relate to metastasis. In this report we have incorporated the above considerations to determine whether NANA shedding can be used as a phenotypic marker for tumour metastasis
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