Transforming growth factor- beta is a polypeptide growth factor. The protein functions by induction of oncogenic transformation in specific cell culture system of rat kidney fibroblasts. It belongs to a big family, which is formed of 40 structurally related regulatory proteins. It plays a vital role in processes that contribute to normal development. This includes cell growth and differentiation. Transforming growth factor-beta is also known to have a role in tumorigenesis. Reactive oxygen species are constantly generated which are constantly eliminated by scavenging systems. Both reactive oxygen species and transforming growth factor-beta have role in cellular senescence. 

Transforming growth factor-beta is known to demonstrate dual function in tumor progression by acting as a tumor suppressor in early carcinogenesis stages and also exerts a prooncogenic role in the latter stage of the disease. Epithelial mesenchymal transition is induced by transforming growth factor-beta, which further contributes in tumor invasion.

A study conducted by Krstic et al, demonstrates the implications of interplay between transforming growth factor-beta and oxidative stress on tumorigenesis and progression of cancer. Both exhibit a contradictory role in progression of cancer. Transforming growth factor-beta controls production of reactive oxygen species by downregulation of anti-oxidative systems while reactive oxygen species influence transforming growth factor-beta signalling and expression. 

The collaboration of reactive oxygen species and transforming growth factor-beta is complicated. Their varied effects on tumor progression needs to be understood for using them in combination in therapies for cancer.