ICAM1 and neoplasm: For example, Coxsackievirus A21 (CVA21) requires intercellular adhesion molecule-1 (ICAM-1) as its cellular entry receptor; in prior models, tumor cell susceptibility to CVA21 was directly correlated with surface ICAM-1 expression, demonstrating that adequate receptor density is necessary for efficient viral attachment, internalization, and oncolysis [133].