Recently, evaluation of 89Zr-RG7356, an antibody directed against the constant part of CD44, was performed in mice bearing tumor xenografts with different levels of CD44 expression and RG7356 responsiveness, namely, MDA-MB-231 (CD44+, responsive), PL45 (CD44+, nonresponsive), and HepG2 (CD44−, nonresponsive) [42]. This evidence concerns the gene CD44 and neoplasm.