Cancer Pharmacology and Translational Research
Our laboratory focuses on molecular pharmacology and experimental therapeutic research. There are three main projects that are currently being investigated in our lab. Our first project seeks to elucidate the molecular mechanisms of chemotherapeutic drug resistance. We propose to determine the biochemical and molecular mechanisms of cancer drug resistance in human tumor cells.
Hydroxyurea has been used in cancer treatment. The targeting enzyme of hydroxyurea is ribonucleotide reductase (RR). RR also is a rate-limiting enzyme for DNA synthesis that is responsible for the conversion of ribonuclotide diphosphate to the deoxyribonucleoside utilized in de novo DNA synthesis or DNA repair. Three subunits of RR have been identified as hRRM1(large subunit) and hRRM2 or p53R2 (small subunit). Our recent experiments have shown that hRRM2 and p53R2 both interact with p53 and play different roles in the cell cycle, DNA repair, and replication. Our current goals are to understand in detail the transcription regulation of RR and its role in cell cycle regulation. Using similar techniques to those necessary for this project, we also are examining the drug resistance mechanisms of purine/pyrimidine analogs on proteosome inhibitions, etc.
Our second project focuses on the development of novel chemotherapeutic agents useful for circumventing drug resistance in human cancer. We are currently examining the mechanisms of RR inhibition by a new RR inhibitor, Triapine, in cell-free studies. The in vitro expression and recombination of each subunit of RR has been used to evaluate the pattern of cytotoxicity and resistance of RR inhibitor and in combination with purine and pyrimidine nucleoside analogs. Another major investigation seeking to develop siRNA to inhibit RR is ongoing. Further structure analyses by EPR and crystallization are currently ongoing with colleagues at the University of California at Irvine (UCI).
Our third project focuses on preclinical therepeutic research and surrogate markers for enhancing cancer drug therapeutic effect. We are currently evaluating human samples collected from RR inhibitors studies and follow real-time PCR, microarray, and proteomic assay for cross-resistance, collateral sensitivity, and synergistic phenomena in RR inhibitors, and other drug combinations. Our results will aid in the development of drugs that will provide a high assurance of therapeutic benefit. Our laboratory efforts also focus on developing a pilot study in a pre-clinical setting and on conveying clinical samples to labs to answer more scientific questions. Overall, our laboratory focuses on experimental therapy and molecular pharmacology. Our mission is to better understand the molecular mechanisms of drug resistance in human cells. This understanding will help us develop new therapeutic agents and methods to overcome drug resistance.
Translational Research Program in Liver Cancers
Using microarray technique, we successfully identified that growth arrest DNA damage-inducible gene 45β (GADD45β) genee expression was down-regulated in human hepatocellular cancer. The GADD45β down-regulation strongly correlated with differentiation and a high nuclear grade of human hepatocellular cancer. Our laboratory transfected GADD45β into two human liver cancer cell lines, HepG2 and Hep3B, to restore gene expression. These transfectants presented p53-dependent apoptosis evident by flow cytometry. The p53 regulation and cell cycling involvement is currently under investigation. The preliminary results suggest that GADD45β is a p53 effector gene. The mutation of the p53 alters the GADD45β expression level in the cell and/or hepatocellular cancer tissues. The future planning in clinical applications is to overexpress GADD45β in human hepatocellular cancer by gene therapy techniques, which is one approach. Moreover, GADD45β apparently also regulated post-transcriptionally may potentially alter mRNA and/or protein stability. A better understanding of the molecular basis of hepatocellular cancer focusing on GADD45β may lead to the design of a new therapeutic target or agent that is currently being discussed.