Cancer progression: Is inhibin α from Venus or Mars?

The inhibin field has been perplexed by the information that inhibin α is a tumour suppressor in mice yet is elevated in women with ovarian cancer. Furthermore, we have consistently observed a down-regulation or loss of inhibin α in prostate cancer patient samples and cell lines. However, our latest data have prompted us to re-evaluate the role of inhibin α in prostate and other cancers. Using the analogy of TGF-β as a springboard for our hypothesis, we offer a unifying model whereby the previously conflicting observations in mice, men and women can be explained. We propose that initially inhibin α is tumour-suppressive and is expressed in benign and early-stage primary cancers. Tumour-suppressive inhibin α is then silenced as the tumour progresses but is reactivated as a pro-metastatic factor in advanced, aggressive cancers.