Perspective Chapter: Topoisomerase 1 and Colo Rectal Carcinoma

Topoisomerase 1 is the main enzyme playing an important role in relaxing. The supercoiled DNA strands allow the replication fork to transcribe the DNA to RNA and finally control protein production in active and replicating cells. Blocking this essential machinery is a cornerstone mechanism in treating tumors, such as liver, breast, and metastatic colorectal carcinoma. Irinotecan is a topoisomerase inhibitor that blocks the replication ending in DNA break and tumor cell death. This chemotherapy has been successfully used in combination to overcome metastatic colorectal carcinoma. The topoisomerase-1 inhibitor makes a protein DNA complex stuck with the replicating fork creating a single DNA break, unlike topoisomerase-2, which is responsible for double DNA break. This inhibitor is exposed to drug resistance with complex machinery. Drug resistance can occur as a result of altered DNA methylation, changes in topoisomerase expression, histone recombination, or drug export pump. High expression of topoisomerase-1 is a marker of the number of tumors suggesting multiple roles of topoisomerase-1.