CD28 and neoplasm: The 2nd generation CAR had a co-stimulatory domain belonging to molecules of CD28 family, such as CD28 and Inducible T cell costimulator (ICOS), or TNF receptor family (4-1BB, OX-40 and CD27), whereas the 3rd generation made use of multiple co-stimulatory domains in tandem (i.e., CD28 in combination with 4-1BB), which in some cases increased the expansion and anti-tumor activities [42].