Sialyltransferase of the 13762 Rat Mammary Ascites Tumor

When compared to normal esophageal epithelium, marked alterations in keratin protein and cross-linked envelope expres sion were found in human esophageal carcinomas. Examination of the pattern of keratin proteins extracted from either several primary esophageal tumors or carcinomas xenotransplanted in nude mice revealed a dramatic reduction in the amount of keratin protein, especially in the Mr 52,000 to 61,000 range. In seven of eight of the primary tumors, the major M, 52,000 and M, 61,000 esophageal keratins were not detected, and the remaining tumor exhibited a marked reduction in these two keratins. The major M, 57,000 and minor M, 59,000 esophageal keratins were found in varying but reduced amounts in the different tumors. The major M, 57,000 keratin seemed to be the most conserved keratin of this intermediate-molecular-weight keratin class (M, 52,000 to 61,000). In contrast, the lower-molecular-weight ker atins (M, 46,000 to 50,500) were usually conserved in the carci noma cells and were present at levels approximating that of the nontransformed counterpart. The minor Mr 37,000 and 44,000 keratins from normal esophageal epithelium were retained in the tumor cells but often in reduced amounts. The expression of another differentiated function, cross-linked envelopes, in the carcinoma cells varied from unimpaired to severely restricted capacity to form envelopes. In conclusion, specific alterations in keratin protein and crosslinked envelope expression were found in human esophageal carcinomas.