BDNF and neoplasm: Psychological stress elevates norepinephrine/epinephrine that engage β2-adrenergic receptors (ADRB2) on tumour and immune cells, raising cAMP to activate PKA and Epac→Rap1/JNK: PKA-phospho-CREB transactivates BDNF promoter IV, while JNK/AP-1 and STAT3 signalling increase CD274 (PD-L1) transcription; ADRB2 blockade (e.g., propranolol) reverses these changes and attenuates CCL2-mediated myeloid influx.