Kent A. Robertson, MD, PhD Associate Professor: Department of Pediatrics
Associate Professor: Department of Pediatrics
Associate Director: Stem Cell Transplantation
Clinical Section: Pediatric Hematology/Oncology
Assistant Member: Fred Hutchinson Cancer Research Center
Associate in Clinical Research: Fred Hutchinson Cancer Research Center
Pediatric Hematology/Oncology Fellowship: Fred Hutchinson Cancer Research Center and the University of Washington, Seattle, WA
Residency: University of Washington, Children's Orthopedic Hospital, Seattle, WA
Post-Doctoral Fellowship: McArdle Laboratory, University of Wisconsin
MD, PhD: University of Wisconsin Medical School, 1982
Current Research Interests:
The role of nuclear retinoic acid receptors, apoptosis, and base excision repair in myeloid leukemia and neuroblastoma cell differentiation.
Retinoic acid (RA) is a functional metabolite of vitamin A which is capable of inducing terminal differentiation in certain kinds of malignant cells by its interaction with nuclear retinoic acid receptors (RAR's). Our laboratory is interested in the mechanisms of RA induced differentiation of normal and malignant myeloid leukemia cells and neuroblastoma cells. A better understanding of these mechanisms will hopefully suggest a more rational approach for the use of RA clinically.
RA-induced myeloid differentiation involves growth inhibition with morphologic granulocytic differentiation and apoptosis or programmed cell death. To determine whether these processes are linked or can be separated, we transduced HL-60 myeloid leukemia cells with the bcl-2 oncogene, which is capable of blocking apoptosis, and found that we could separate granulocytic differentiation from apoptosis as the transduced HL-60 cells responded to RA with normal granulocytic differentiation but not apoptosis, thus producing long-lived granulocytes. Other experiments have shown that HL-60 cells are able to acquire resistance to RA induced differentiation by mutating the endogenous retinoic acid receptor (alpha) to produce a dominant negative receptor capable of interfering with normal receptor function and thus blocking the normal differentiation pathway.
Apurinc-apyrimidinic endonuclease (hAPE, ref-1) is an enzyme in the base excision DNA repair pathway and has been thought for many years to be a housekeeping gene with continuous baseline expression in all cells. In recent collaborative studies with Dr. Mark Kelley's laboratory, we have shown that APE appears to be down-regulated as myeloid cells undergo terminal differentiation with apoptosis. Moreover, HL-60 cells overexpressing bcl-2 and induced with RA will differentiate but do not down-regulate APE expression demonstrating an association between bcl-2 expression, apoptosis, and APE expression. In continuing studies our laboratories are characterizing the molecular biology and biochemistry of the relationship between APE expression and apoptosis and the potential impact this may have in cancer therapeutics.
We are also investigating the role of RA in neuroblastoma cell neuronal differentiation. We have recently characterized the RA-induced differentiation of the LA-N-5 neuroblastoma cell line as a model system for cholinergic neuronal development. Current studies are examining the impact of oxidative damage and the role of base excision DNA repair in neuronal development and response to injury. Other studies are approaching the role of retinoic acid receptors in RA-induced neuroblastoma cell differentiation to gain insight into better use of retinoids therapeutically.