MAPK3 and neoplasm: To specify the role of SAP18 on ERK1/2 activation, a lentivirus-based SAP18 overexpression sequence was intrapleurally injected into WT tumor-bearing mice to overexpress SAP18, and lentivirus-based RNA interference against SAP18 was intrapleurally injected into CXCR2−/− tumor-bearing mice to knock down SAP18.