Our research interests include 'Oxidative Stress Signaling, Cell Survival and Death, Chemoprevention, Oncogenesis and Bioreductive Drug Activation and Drug Development'.  Oxidative stress is associated with degenerative diseases of hepatic, renal, cardiovascular and nervous tissues, apoptotic cell death, aging, cellular transformation and neoplasia.  The initial response of cells to oxidative stress is to turn on signal(s) that lead to the coordinated activation of a battery of more than hundred defensive genes that protect against oxidative stress and neoplasia and promote cell survival.  Included in this battery of gene products are antioxidant enzymes [quinone oxidoreductases (NQO1 and NQO2)], antioxidants, and tumor suppressor p53.  We have identified antioxidant response element (ARE) and NF-E2 related transcription factors (Nrf2, Nrf1 and Nrf3) that regulate expression and induction of defensive genes in response to oxidants, antioxidants and xenobiotics.  We further determined that Nrf2 is retained in the cytoplasm by a repressor protein called INrf2 (Keap1).  INrf2 has been cloned and sequenced in our laboratory.  The studies also suggested that INrf2:Nrf2 complex serves as sensors of chemical/radiation-induced oxidative stress.  We have identified kinase(s) and redox factors that mediate signal transduction from ROS to the cytosolic Nrf2/INrf2 complex leading to the release of Nrf2 from INrf2, nuclear localization of Nrf2 and coordinated activation of ARE-containing defensive genes.  Currently, we are utilizing molecular biological and biochemical techniques to identify and study the role of the various regulatory molecules in transduction of a signal from ROS to the ARE, which then regulates the induction of a battery of defensive genes.

Knockout mouse models have been, and are being, generated in our laboratory to study the in vivo role of proteins responsive to oxidative stress in cancer.  We have generated knockout mice that do not express NQO1 and NQO2.  Both NQO1-null and NQO2-null mice have myelogenous hyperplasia in the bone marrow and show increased susceptibility to chemical-induced skin tumors.  We are testing whether NQO1-null and NQO2-null mice demonstrate an increased susceptibility to developing myeloid leukemia.  In addition, we are performing microarray and proteomic analyses to identify the growth/proliferation/differentiation genes/proteins that might be the targets leading to myelogenous hyperplasia of bone marrow, myeloid leukemia and increased sensitivity to chemically-induced skin cancer in NQO1-null and NQO2-null mice.

Bioreductive chemotherapy is based on reductive activation of drugs by enzymes, identification of tumors rich in those enzymes, and differences in oxygen and pH between normal and tumor tissues.  Recently, we have identified and cloned the cytosolic glucose regulatory protein (GRP58) that plays a significant role in activation of antitumor drug mitomycin C leading to DNA cross-linking and cell death.  GRP58 found overexpressed in many tumors qualifies for selective activation of drugs in tumors.  Recent studies have also shown that significant percentage of human individuals with chemotherapy-induced secondary leukemia carry both mutant NQO1 P187S alleles and are deficient in NQO1 protein.  However, it is unknown if the absence of NQO1 contributed to chemotherapy-induced leukemia.  Our current goals are to determine the mechanism of the role of GRP58 in mitomycin C-induced DNA cross-linking and study the in vivo role of GRP58 in mouse development and anti-tumor drug toxicity.  In addition, investigate the in vivo role of NQO1 in chemotherapy-related secondary leukemia.