Expression of 11β-hydroxysteroid dehydrogenase enzymes in human osteosarcoma: potential role in pathogenesis and as targets for treatments

Osteosarcoma (OS) is a primary malignant tumour of bone occurring predominantly in children and young adults. Despite chemotherapy, relapse is common and mortality remains high. Non-transformed osteoblasts are highly sensitive to glucocorticoids, which reduce proliferation and induce apoptosis. Previously, we observed that OS cells, but not normal osteoblasts, express 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2). This enzyme inactivates cortisol (active) to cortisone (inactive) and expression of 11 beta-HSD2 renders OS cells resistant to glucocorticoids. By contrast, the related enzyme 11 beta-HSD1 converts cortisone to cortisol and reduces OS cell proliferation in vitro. Some synthetic glucocorticoids (e.g. dehydrodexamethasone (DHD), inactive counterpart of dexamethasone (DEX)) have been reported to be activated by 11 beta-HSD2. We therefore investigated expression and enzymatic activity of 11 beta-HSD isozymes in human OS tissue, determined whether 11 beta-HSD expression has prognostic value in the response to therapy, and evaluated the potential use of synthetic glucocorticoids to selectively target OS cells. OS samples expressed both 11 beta-HSD1 and 11 beta-HSD2. 11 beta-HSD1 expression in pretreatment biopsy specimens positively correlated with primary tumour size. Expression and activity of 11 beta-HSD1 in post-treatment biopsies were unrelated to the degree of tumour necrosis following chemotherapy. However, high 11 beta-HSD2 expression in post-treatment biopsies correlated with a poor response to therapy. OS cells that expressed 11 beta-HSD2 inactivated endogenous glucocorticoids; but these cells were also able to generate DEX from DHD. These results suggest that OS treatment response is related to 11 beta-HSD2 enzyme expression. Furthermore, OS cells expressing this enzyme could be targeted by treatment with synthetic glucocorticoids that are selectively reactivated by the enzyme. Endocrine-Related Cancer (2012) 19 589-598