ICAM1 and neoplasm: However, during tumor development, many tumors downregulate and/or modify surface receptor expression and the tumor endothelium, inhibiting immune cell intravasation into the tumor [ex: reduced CXCL9/10 expression within the tumor (28) or suppression of adhesion molecules such as VCAM-1 and ICAM-1 within the endothelium (29)] (30–36).