Ectopic hCGβ expression by epithelial cancer: Malignant behaviour, metastasis and inhibition of tumor cell apoptosis

Ectopic expression of the β-subunit of human chorionic gonadotropin (hCG) is now a recognized phenomenon in 20-40% of all common epithelial carcinoma arising from mucosal epithelia such as bladder, cervix, lung and naso-pharynx. Recent studies have shown that it acts as an autocrine growth factor by inhibiting apoptosis. Structural homology and in vitro studies suggest that it may achieve this by inhibition of the transforming growth factor β (TGFβ) receptor complex. Such a molecular mechanism would go some way to explaining ectopic hCGβ's association with poor prognosis and tumors that will rapidly progress to metastasis.