Characteristics of Transplantable Tumors Induced in the Rat by N-2-Fluorenylacetamide: Elevations in Tissue and Serum Sialic Acid23

Abstract

The correlation between levels of sialic acid and sialic acid-containing glycolipids (gangliosides) in tumors and serum with the growth characteristics of the tumors was investigated in transplantable hepatomas and squamous cell carcinomas initiated with the carcinogen N-2-fluorenylacetamide and propagated in vivo and in tissue culture. Tumor lines varied in histologic classification, growth rats, and ability to form pulmonary metastases. There was neither a correlatlon between growth rats and histologic classification nor between either of these two parameters and the ability to metastasize. Total and ganglioside sialic acid levels were elevated in carcinogen-treated liver and in transplantable hepatomas when contrasted with normal liver. Levels of sialic acid showed a weak correlation with the growth rats of hepatomas. Gangliosides from nonmetastatic hepatoma lines exhibited less N-acetylneuraminic acid-galactose-glucose-N-acylsphingosine (Gm₃) and an increased ratio of total monosialogangilosides to disialogangilosides than did metastatic lines. Ganglioside patterns of metastatic hepatoma lines more closely resembled the ganglioside patterns of normal liver than did those of the non metastatic lines. Concomitant elevations of lotal and ganglioside sialic acid levels were observed in sera of animals bearing subcutaneous implants. Serum levels of total sialic acid did correlate with total sialic acid levels found in the lumor tissues. The levels of serum sialic acid were not correlated directly wllh levels of serum sialyltransferase activity. Elevations of bolh tissue and serum ganglioside sialic acid were consistent fealures of liver tumorigenesis in the rat after N-2-fluorenylacetamide administration. They appeared, furthermore, to be early events not directly related to tumor cell differentiation or metastasis.