Background: Expression of activin A is associated with lymph node metastasis and clinical stage in esophageal cancer. Methods: To clarify the aggressive behavior of tumors with high activin A expression, we used the β subunit of activin A to establish stable activin βA (Act-βA)- transfected carcinoma cells in two human esophageal carcinoma cell lines, KYSE110 and KYSE140. The biological behavior of these cells was compared with that in mock-transfected cells from the same cell lines. We focused our attention on cell growth and tumorigenesis, and proliferation and apoptosis. Results: Both Act-βA-transfected carcinoma cell lines showed a higher growth rate than the mock-transfected carcinoma cells. In an in vitro invasion assay and a xenograft analysis, the Act-βA-transfected carcinoma cells showed far higher proliferation in vitro and a higher potency for tumorigenesis in vivo, respectively. Moreover, in an analysis of apoptosis via Fas stimulation, the Act-βA-transfected carcinoma cells showed a higher tolerance to apoptosis compared with the mock-transfected carcinoma cells. Moreover, anti-activin-neutralizing antibody-treated squamous cell cancer cell lines inhibited their migration. Conclusions: Collectively, these data indicate that continuous high expression of activin A in esophageal carcinoma cells is not related to tumor suppression, but rather to tumor progression in vitro and in vivo. The inhibition of activin might be one of the methods to attenuate tumor aggressiveness.
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