ERBB2 and gastric cancer: However, disadvantageous signalling as a consequence of transactivation has been identified such as progression from acute to chronic pain (μ opioid/EGFR in opioid-induced hyperalgesia [8]), proliferation of human hyperplastic prostatic cells (α1-AR/EGFR [9]), gastric cancer cell migration (CXCR4/EGFR [10]), poor patient prognosis and increased lymphatic spread in HER2+ breast cancer patients (cannabinoid receptor 2 (CB2R/HER2 [11]) and underlying tumour re-occurrence following anti-VEGF/VEGFR2 therapeutics (sphingosine 1-phosphate receptor/VEGFR2 [12]).