Biochem/Physiol
Actions | PX-12 is a small molecule irreversible inhibitor of the redox protein thioredoxin. Thioredoxin is involved in the first unique step in DNA synthesis. Thioredoxin also provides control over a number of transcription factors affecting cell proliferation and death through the mechanism of redox regulation Trx regulates cell growth through the following steps: 1) Trx is reduced into its active state, Trx (red) by the enzyme thioredoxin reductase. 2) Trx enters the nucleus to regulate transcription factor activity (factors which affect DNA replication). 3) Trx is excreted out of cell where it works with other growth factors (GF) to stimulate cell growth. It has been shown that many cancer cells secrete thioredoxin; increased levels of thioredoxin protein have been reported in a wide range of human cancers including hepatoma, lung, squamous cervical carcinoma, primary gastric cancers, and colorectal carcinomas; thioredoxin stimulates the growth of a wide variety of human leukemia and solid tumor cell lines; thioredoxin, when it is over-produced, transforms normal cells into cancer cells; thioredoxin is a potent inhibitor of apoptosis and provides a survival as well as a growth advantage to tumors; elevated tumor thioredoxin levels have been associated with decreased patient survival in colon cancer and NSCLC; and elevated thioredoxin levels cause a decrease in sensitivity of cells to cancer drugs such as doxorubicin (14 fold), vincristine (8 fold), cisplatin (5 fold), and cytosine arabinoside (13 fold). Therefore PX-12, by limiting the over- of thioredoxin in human tumors, could reduce resistance to chemotherapy. |
