Regulation of Cellular senescence by members of the TNF receptor family

CD40 is a member of the superfamily of proteins named TNFR’s, it is known to be expressed on a range of tumour cells. CD40 signalling causes apoptosis within CD40 positive cell lines such as colorectal and bladder cancer cells. Ligation of CD40’s conjugate ligand however has been shown to be ‘quality’ specific as to whether the ligand is presented on the membrane of a cell (mCD40L) or CD40 soluble agonistic mAb (G28-5).

While cell death is a well-documented effect of CD40 signalling, its ability to regulate a senescence associated phenotype is relatively unknown and contrasting the effects of G28-5 and mCD40L in the regulation of senescence has never been studied. This thesis aimed to investigate whether CD40 signalling is able to regulate senescence within colorectal and bladder cancer cells and whether CD40L delivery by mCD40L or G28-5 affect senescence regulation.

This study confirmed previous findings showing CD40 signalling is able to make CD40 positive cancer cells pro-apoptotic. Immunoblotting demonstrated that following CD40-CD40L ligation there was an increase in P-p53, p21 and −H2AX, but no expression of p16, four senescence associated proteins. Different levels of senescence associated protein expression were shown to be a result of the quality of signal be that G28-5 or mCD40L. The research has also for the first time by flowcytometry shown an increase in SA-β-galactosidase following ligation of the G28-5, however it was found that β-galactosidase was only detected in the less CD40 susceptible cancer cells demonstrating b-gal and apoptosis detection are mutually exclusive.

Altogether this study has shown that senescence associated phenotype can be regulated by CD40 receptor signalling in colorectal and Bladder cancer cells. In addition, while functional experiments would be required, it has attempted to describe a pathway by which CD40 may regulate senescence in CD40 positive cancer cells, demonstrating once again why signal quality is an important factor when signalling CD40.