Figure 3
From: Understanding the mechanisms of aromatase inhibitor resistance
Mechanisms of oestrogen-stimulated growth (whereby androgen is aromatised into oestrogen, which interacts with and activates oestrogen receptor (ER) to stimulate proliferation and growth), aromatase inhibitor (AI)-induced response (whereby AIs block aromatization of androgens into oestrogens) and multiple potential mechanisms of resistance to AIs. Blocks represent sites of specific interactions: A, ineffective inhibition of aromatase; B, alternative sources of oestrogen/oestrogenic hormones (ES); C, inherent oestrogen insensitivity (non-functional ER); D, ligand-independent activation of oestrogen signalling pathways; E, oestrogen signalling disconnected from tumour proliferation and growth; F, enhanced cell survival. Abbreviations: A, androgen precursor; CSF, cell survival factor; E, oestrogen; ER, oestrogen receptor; ER-P, activated (phosphorylated) ER; GF, growth factor; Prolif, proliferation; Resp, response.