Polymerase activity, hormone regulation

Poly(ADP-ribose) polymerase may also have a role in regulating the activity of nuclear-acting hormone receptors it hinds directly to retinoid X receptors (Section 2.3.2.1) andinhihits the transcriptional activity of retinoid X receptor-thyroid hormone dimers, it also acts as a transcription factor in pancreatic /S-islet cells (Miyamoto et al., 1999). 

Over expression of tumor suppressor gene bcI-2 plays an important role in cellular resistance to apoptosis caused by various factors (77). Lin et al have shown that over expression of anti-apoptotic Bcl-2 and Bc1-Xl proteins may play a role in the development of resistance to cancer therapy 18). Functional over expression of Bcl-2 has been reported to confer an anti-apoptotic potential in a variety of cell types. The role of Bcl-2 in epithelial cell-cycle control and in interactions with other cell-cycle regulators is not clearly understood. Its expression has been correlated with the hormone- and chemo-resistant phenotype in advanced prostate cancer 19). Granville et al have shown that overexpression of Bcl-2 in HL-60 cells prevented apoptosis-related events including caspase 3 and 6 activation, poly (ADP-ribose) polymerase cleavage by photodynamic therapy (20). Over expression of HER2 in estrogen receptor (ER)-positive human breast tumors has been associated with resistance to endocrine therapy. 

---