The Role of the Glucocorticoid System in Anchorage-independence during Progression of Squamous Cell Carcinoma

Background: Topical and systemic corticosteroids are widely used for the treatment of mucocutaneous disorders including those with malignant potential. We have shown previously that normal keratinocytes regulate the local concentration of active steroids, as well as synthesize hydrocortisone de novo following stimulation with ACTH. The role of locally produced hydrocortisone in tumour progression is unclear. Objective: To examine the ability of endogenously-produced and exogenously-administered hydrocortisone on the capacity of human keratinocytes to promote the formation of anchorage-independent multicellular aggregates (MCAs) in vitro. Methods: The human keratinocyte cell line HaCaT derived from irradiated facial skin and c-Ha-ras-transfected HaCaT cell clones (I-7, II-3, RT-3) demonstrate increasing tumorigenic and metastatic potential in vivo and are ideally suited to studies of keratinocyte tumour progression. The formation of multicellular aggregates (MCAs) in vitro was used as a paradigm of metastatic potential in vivo. Results: Non-tumorigenic (HaCaT), benign (I-7), malignant with low metastatic potential (II-3) and malignant with high metastatic capacity (RT-3) keratinocytes secreted basal levels of cortisol, activated cortisone and differentially synthesized cortisol de novo in the presence of ACTH; malignant cells (II-3 and RT-3) produced the highest levels of the steroid. When the cells were cultured in the absence of a substrate, RT-3 cell in particular were highly effective in forming MCAs and hydrocortisone further promoted MCA formation. Stimulation of the endogenous glucocorticoid system by ACTH caused an increase in MCA formation by II-3. Conclusions: The data demonstrate that stimulation of the endogenous glucocorticoid system promotes anchorage independence of malignant keratinocytes in vitro.