MedicalResearch.com Interview with:
Dr. Hua Lu MS PhD
Department of Biochemistry & Molecular Biology
Reynolds and Ryan Families Chair in Translation Cancer
Tulane Cancer Center
Tulane University School of Medicine
New Orleans, Louisiana 70112
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: It has been well appreciated and acknowledged that p53 is the most important tumor suppressor in human body. However, approximately 50% of human cancers still sustain the wild type form of its gene, and also oddly, some cancers, such as breast cancer, which contain wild type p53, are often less sensitive to chemotherapy than those harbor mutated p53. Although a number of oncoproteins, including MDM2 and MDMX (MDM4), have been shown to be highly expressed and to inactivate p53 in those wild type p53-containing cancers, more molecules need to be discovered to keep p53 in control in order to let cancer cells to proliferate and growth.
Our study as described in our recent publication in Nature Communications unveils a new p53 target gene that encodes pleckstrin homology domain-containing protein (PHLDB3) as another p53 inhibitor in a negative feedback fashion. Interestingly and mechanistically, PHLDB3 can work with MDM2 by boosting its E3 ubiquitin ligase activity, consequently leading to degradation of p53. Biologically, PHLDB3 can promote cancer cell proliferation and growth in culture and in xenograft tumor models by in part inactivating p53 activity. More interestingly, PHLDB3 is highly amplified and expressed in a number of human cancers, such as pancreatic, prostate, colon and breast cancers. High expression of PHLDB3 is well correlated with the wild type status of p53 in certain portion of breast cancer. These findings uncover PHLDB3 as another
oncoprotein that can promote cancer growth by partially inactivate p53, and thus might serve as a potential target for future development of anti-cancer therapy. Our study also suggests that PHLDB3 has a p53-independent function important for cancer growth.
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