Pro-GA, as a cell membrane permeable GGCT inhibitor, might become a promising novel therapeutic agent against various cancers expressing high levels of GGCT such as breast, ovarian, cervical, lung, urinary bladder, colon cancers, osteosarcoma, esophageal squamous cell carcinoma, and glioma. The gene discussed is GGCT; the disease is esophageal squamous cell carcinoma.