Significantly, abnormal expression of multiple RGS proteins, such as RGS17 in hepatocellular carcinoma, lung cancer, and prostate cancer, RGS5 in ovarian cancer and squamous cell carcinoma, and RGS6 in breast cancer and urinary bladder cancer, has been documented in relation to tumor progression [31–34]. Here, PITX2 is linked to squamous cell carcinoma.