Molecular genetics of DNA repair in humans

My major research interest is the molecular biology and molecular genetics of DNA repair in humans. I established my research program and pursued this interest over the years with extramural funding from the National Institutes of Health and from foundations. My laboratory has made significant contributions to the understanding of the molecular genetics of human nucleotide excision repair. We characterized mutations in the essential nucleotide excision repair gene XPA in genomic DNAs from cell lines established from patients and contributed to a compendium of mutations in human DNA repair genes. More recently, we have identified polymorphisms in XPA and performed preliminary characterizations of these polymorphic alleles. Publications from this project during the past five years include:

1. Cleaver, JE and JC States, "The DNA Damage Recognition Problem in Human and other Eukaryotic Cells: the XPA Damage Binding Protein", Biochem. J., 328: 1-12 (1997)
2. States, JC, ER McDuffie, SP Myrand, McDowell, M. and JE Cleaver "Distribution of Mutations in the Human XPA Gene and Their Relationships to the Functional Regions of the DNA Damage Recognition Protein", Human Mutation 12: 103-113 (1998)
3. Cleaver, JE, Thompson LH, Richardson, AS, States, JC, "Distribution of Mutations in the Excision Repair Complementation Groups of Xeroderma Pigmentosum, Cockayne syndrome and Trichothiodystrophy - a summary", Human Mutation 14: 9-22 (1999).
4. Mellon, I, Hock, T, Reid, R, Porter, PC and States, JC "Polymorphisms in the human xeroderma pigmentosum group A gene and their impact on cell survival and nucleotide excision repair", DNA Repair 1: 531-546 (2002)

DNA repair and chemoresistance

Elevated DNA repair plays a significant role in chemoresistance. Elevated DNA repair gene expression correlates with resistance to platinum-based chemotherapy in ovarian, gastric and lung cancer. I collaborated with Dr. Eddie Reed (NCI) to show that ovarian tumors overexpressing XPA did not have alterations in the XPA genes and likely had altered the regulation of XPA (States & Reed, 1996). My laboratory continued to work on XPA regulation in cisplatin-resistant ovarian cancer. I recently obtained funding from the Elsa U. Pardee Foundation to continue these studies. We plan to publish our results identifying a transcription factor that is responsible for suppressing XPA expression and sensitizing ovarian cancer cells to platinum-based therapies. I have submitted grant applications to both the National Institutes of Health and the Department of Defense for additional support to continue these studies. I am developing a collaboration with Dr. Robert Edwards (Gynecologic Oncology) to translate these findings by determining the correlation of the presence of this factor in ovarian tumor tissues with responsiveness to platinum-based chemotherapy. I collaborated with Dr. David Bregman (Albert Einstein College of Medicine) to show that suppression of DNA repair gene expression by antisense transfection sensitizes ovarian cancer cells to platinum- chemotherapeutics. This work provides preliminary data supporting development of anti-DNA repair gene ribozymes as potential gene therapy to sensitize chemoresistant tumors to platinum-based therapies. A medical student currently is preparing and testing anti-XPA ribozyme vectors as a summer research project in my laboratory. His results will provide preliminary data to support grant applications to be submitted over the coming year. The collaborative work with Dr. Bregman was recently published:

1. Lu, Y, Mani, S, Kandimalla, ER, Yu, D., Agrawal, S, States, JC and Bregman, DB "Targeting the Cockayne syndrome group B protein with antisense oligonucleotides sensitizes ovarian carcinoma cells to cisplatin, oxaliplatin, or ionizing radiation", Internatl. J. Oncol. 19:1089-1097 (2001).

Arsenic carcinogenesis

Arsenic is a human carcinogen and recently was approved as a chemotherapeutic agent. I became interested in arsenic because it was reported to interfere with DNA repair. Our work has led us to discover that arsenic disrupts cell cycle control and induces mitotic arrest and apoptosis in SV40 immortalized cells. Our investigations have led us to hypothesize that p53 plays a significant role in modulating arsenic toxicity. Understanding how arsenic induces apoptosis in mitotically arrested cells will also provide important information on how arsenic acts as a chemotherapeutic. We are preparing a manuscript to report our findings that p53 expression prevents arsenic induced mitotic arrest. Publications from this project during the past five years include:

1. Waalkes, MP, Fox, DA, States, JC, Patierno, SR and McCabe, MJ Jr, " Metals and Disorders of Cell Accumulation: Modulation of Apoptosis and Cell Proliferation ", Toxicolog. Sci. 56: 255-261 (2000).
2. McCabe, MJ, Jr, Singh, K, Reddy, SA, Chelladurai, B, Pounds, JG, Reiners, JJ, Jr and States, JC "Sensitivity of Myelomonocytic Leukemia Cells to Arsenite-induced Cell Cycle Disruption, Apoptosis and Enhanced Differentiation on the Inter-Relationship between Arsenic concentration, duration of treatment and cell cycle phase", J. Pharmacol. Exp. Therap. 295: 724-733 (2000).
3. States, JC, McCabe, MJ, Jr., Pounds, JG, Reiners, JJ, Jr., Kaplan, DJ, Mathieu, P and Sowder, HG Arsenite Disrupts Mitosis and Induces Apoptosis in Phenotypically p53 Negative Human Skin Fibroblasts", International Conference on Heavy Metals in the Environment August 6-10, 2000, Ann Arbor, MI, manuscript #1025
4. States, JC, Reiners, JJ, Jr., Pounds, JG, Kaplan, DJ, Beauerle, BD, McNeely, SC, Mathieu, P and McCabe, MJ, Jr "Arsenite Disrupts Mitosis and Induces Apoptosis in SV40-Transformed Human Skin Fibroblasts", Toxicol Appl Pharmacol 180: 83-91 (2002)

Metabolically activated carcinogens

Most chemical carcinogens in the environment require metabolic conversion to DNA reactive electrophiles that are the ultimate carcinogens. Consequently, exposure to reactive metabolites occurs at low doses and at low dose rates. I designed and developed an in vitro cell culture model to study DNA damage by carcinogens metabolically activated in situ (States et al 1993). We observed that DNA damage by reactive benzo[a]pyrene metabolites at near physiological doses and dose rates was non-random and that transcriptionally active genes were selectively attacked. We have endeavored to determine the structural basis for the non-randomness of DNA damage by chemicals. We have found that the relative amounts of the two major DNA adducts formed on naked DNA is dependent on both the dose and the conformation of the DNA. We have published these results in abstract form and are preparing the manuscripts for publication.

1. Jiang, G, Skorvaga, M, Van Houten, B and States, JC. Incision Of BPDE-DNA-Adducts With Thermal-Resistant Uvrabc Excision Nuclease From B.Caldotenax. Toxicological Sciences 60(1): 32 (2001)
2. Jiang, G, McNeely, S, Skorvaga, M, Van Houten, B and States, JC. DNA Adduct Conformation Depends On DNA Conformation. Toxicological Sciences 66: 884 (2002)