Anatomy, Physiology & Genetics (APG)
Uniformed Services University of the Health Sciences
4301 Jones Bridge Road
Bethesda, Maryland 20814
Meera Srivastava, Ph.D.
- Indian Institute of Technology, New Delhi, India, 1982
Molecular and genetic approaches to understanding the role of ANX7 in Breast and Prostate Tumorigenesis The ANX7 gene codes for a Ca2+-activated GTPase, which has been implicated in both exocytotic secretion in cells and control of growth. Evidence for a tumor suppressor function for ANX7 comes from our experiments in which transfection of ANX7 expression caused inhibition of colony forming units. When we overproduced this protein in prostate cancer cells, it reversed their malignant properties and forced them to stop dividing at G2 phase resulting in apoptosis. Introduction of adenovirus containing ANX7 completely eradicated the tumor in nude mice experiments. Total disruption of Anx7 resulted in embryonic lethality in mice, whereas animals heterozygous for Anx7 expression display defects in growth control, Ca2+ signal transduction, endocrine functions and increased incidence of spontaneous tumors. Using a prostate tissue microarray containing 305 patient specimens, we found profound loss of ANX7 protein expression associated with metastases and hormone insensitive local recurrent cancers. In addition, we found that allelic loss of the ANX7 gene occurs on 10q21 in over one third of primary carcinoma of the prostate and breast. In breast carcinomas, ANX7 expression is significantly associated with the presence of metastatic disease and HER2 negative tumors. Currently, we are using genomic, proteomic, yeast two hybrid system to study protein-protein interaction and promoter regulation approaches to identify the ANX7 signaling pathway and its role in cancer in order to develop novel therapeutic tools for prostate and breast cancer.
Nucleolin's role in cell proliferation and cancer
I cloned the human cDNA and gene for the major nucleolar protein called "nucleolin" involved in ribosome biogenesis and localized it to chromosome 2q12-qter. Since Myc directly transactivates the nucleolin gene and nucleolin is the second best androgen regulated gene in prostate cancer, we are focusing our studies in the altered regulation of nucleolin and myc in prostate cancer using molecular and biological approaches.
Molecular basis of vectorial electron transport processes within cells
In early studies on chromaffin granules, which classically secrete catecholamines in response to a calcium pulse, attention was focused on the principal membrane protein cytochrome b561. This cytochrome is responsible for the unique process of vectorial electron transport across the membrane, and transfers electrons from ascorbic acid to dopamine beta hydroxylase (DBH) for the biosynthesis of norepinephrine from dopamine within the vesicle. I cloned the gene for this enzyme and interpreted the sequence in terms of a proposed transmembrane conformation. Cytochrome b561 was differentially expressed in cancer cell lines and was androgen regulated in prostate cancer xenograft model. This new knowledge of the structure of human cytochrome b561 gene, its promoter and its differential expression in cancers provided new insights into the cytochrome b561's role in cancer and is the focus for future research.