Enolase isozymes in differentiated and undifferentiated medullary thyroid carcinomas

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Abstract
Enolase isozyme composition was studied using both electrophoretic and chromatographic methods in rat medullary thyroid carcinomas (MTC), differing in their degree of differentiation. In well‐differentiated rat tumors (DMTC), both the α‐ and γ‐subunits of enolase were expressed, resulting in αα,αγ, and γγ isozymes. The relatively high amount of αγ and γγ isozymes (neuron‐specific enolase [NSE]) was indicative of the presumed neuroectodermal origin of these tumors. In contrast, highly undifferentiated or anaplastic tumors (AMTC) were characterized by a decrease in expression of the γ‐subunit. Hence, the majority of enolase isozymes were αα dimers, with only a few percent αγ hybrids remaining. These shifts from neuron‐specific to non‐neuronal isozymes in rat MTC were compared with human MTC and discussed with respect to neuronal differentiation and the clinical significance of NSE measurements in serum as a marker for amine precursor uptake and decarboxylation cell‐derived neoplasms.