Other potential causes of recurrence include epigenetic reprogramming by the stroma [200], autophagy [201], increased stress hormones and glucocorticoid receptor expression in metastases [202], transient angiogenic bursts [203], systemic response to surgery [204], use of opioids [205], sympathetic signaling [206] and depression through serotonin-induced RUNX2/PTHrP/RANKL signaling [207], among others. The gene discussed is PTHLH; the disease is major depressive disorder.