Growth and differentiation of human esophageal carcinoma cell lines

Human esophageal carcinoma cell lines (8 cell lines) differed from their normal counterpart in terms of their morphological appearance, growth properties, and the expression of certain differentiated functions, namely keratin proteins and cross-linked envelopes. In contrast to normal human esophageal keratinocytes, the carcinoma cells were pleomorphic and tended to pile up in an unorganized fashion. When grown under optimal growth conditions the carcinoma cells generally grew to a higher saturation density than their nontransformed counterpart; their generation times were variable. Transformed cells grew better under stringent growth conditions (e.g., decreased serum and no additional growth factors except hydrocortisone) than did nontransformed human esophageal keratinocytes but their growth was still restricted under these conditions. The carcinoma cells retained a requirement for a 3T3 feeder layer when grown at clonal densities (5 X 10(3) cells/60-mm dish) but could be passaged and maintained without a feeder layer if plated at higher than clonal densities (10(5) cells/60-mm dish). All cell lines grew in an anchorage-independent fashion in soft agarose although the colony forming efficiency and size of the colonies varied among the different cell lines. Not all anchorage-independent cell lines were tumorigenic. Tumorigenic potential was greatly augmented by the use of cell lines derived from soft agarose selected clones. Altered expression of keratin proteins and cross-linked envelopes was observed in the carcinoma cell lines and generally reflected those changes seen in primary esophageal carcinomas. In two cell lines (HCE-4 and HCE-6), the synthesis of the Mr 44,000 (analogous to Rheinwald's Mr 40,000 keratin) and 52,000 keratins was suppressed coincident with the appearance of the 67 Kd keratin in tumors derived from these cell lines. These keratin patterns were once again reversed in cell lines recultured from these tumors, suggesting that the expression of these specific keratins is subject to extrinsic growth regulation. Another feature of terminal differentiation in keratinocytes, cross-linked envelope formation, was found to be significantly altered (reduced) in most but not all human esophageal carcinoma cell lines.