Activin A is a member of the transforming growth factor β (TGF-β) superfamily and is a strong differentiation factor of embryonic stem (ES) cells. It is unknown whether activin A has any correlation with carcinoma cell differentiation. We investigated the expression of activin-βA (Act-βA) which is a subunit of activin A, its receptor type I and IIb (ActRI, ActRIIb) and its inhibitor, inhibin-α (Inh-α), which is a subunit of inhibin A in esophageal carcinoma by reverse transcription polymerase chain reaction (RT-PCR) method. Act-βA was overexpressed in carcinoma tissues significantly (p=0.030). On the other hand, Inh-α, ActRI and ActRIIb were neither overexpressed, nor suppressed. In immunohistochemistry and in situ hybridization analysis, Act-βA expression was mainly derived from carcinoma cells. The mRNA expression of Act-βA was not associated with carcinoma cell differentiation but lymph node metastasis (n0, 1, 2 vs. n3, 4; p=0.013) and clinical stage (I, II, III vs. IV; p=0.026). Moreover, patients with high mRNA expression of Act-βA had a tendency to show poor prognosis compared to those with low mRNA expression (p=0.064). The finding indicated that activin A expression might not be associated with carcinoma cell differentiation but tumor aggressiveness such as lymph node metastasis in esophageal carcinoma.

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