SPP1 and lung cancer: Furthermore, we found that GAMs highly express SPP1. SPP1 (also called Osteopontin) is a secreted protein that has been postulated to increase tumor cell invasion in vivo and migration in vitro, and was found to be highly expressed in different types of cancers, such as lung cancer, ovarian cancer, and also glioma [56,57,58,59,60,61].