In breast cancer, CAFs activate the PI3K/AKT pathway via the G protein‐coupled estrogen receptor (GPR30) to upregulate HMGB1 secretion; HMGB1 then induces tumor cell autophagy through the MEK/ERK pathway in a paracrine manner, strengthening tamoxifen resistance [101]. Here, HMGB1 is linked to breast carcinoma.