CELF2 (CUGBP Elav-like family member 2), an RNA binding protein isoform of CELF, performs important functions in the development and activation of T cells [99] CELF2 acts as a tumor suppressor for a variety of cancers, (ovarian cancer, breast cancer, gastric cancer, glioma, hepatocellular carcinoma, including lung cancer and thus is considered as a biomarker in lung squamous cell carcinoma and breast cancer [100,101]. The gene discussed is CELF2; the disease is breast cancer.