SPP1 and head and neck cancer: In the published literature, Osteopontin splice variants have been evaluated in 15 types of malignancies (breast cancer, colon cancer, esophageal cancer, gastric cancer, glioma, head and neck cancer, liver cancer, lung cancer, mesothelioma, ovarian cancer, cervical cancer, pancreatic cancer, prostate cancer, soft tissue sarcoma, and thyroid cancer).