Among the proteins present in the membrane of neutrophils, L-selectin, Lymphocyte function-associated antigen 1 (LFA-1), and β1 integrin were involved in tumor targeting by interacting with CD44, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) on the surface of circulating tumor cells, respectively. The gene discussed is CD44; the disease is neoplasm.