I believe prevention is a practical, non-invasive and dependable approach to control breast and other organ cancers. Knowledge of the mechanisms by which a promising chemopreventive agent interrupts cancer cell proliferation is very critical to design effective cancer prevention strategies. New model systems are essential bearing in mind the heterogeneity of the disease especially in breast cancer. For that reason, several outgrowths of premalignant stage of breast cancer would be best suited to examine the block of molecular and / or cellular events by chemopreventive agents, leading to an effective prevention strategy. My laboratory focuses on establishing model systems to investigate molecular mechanisms of prevention in breast and prostate cancers.
Model Systems for Breast Cancer Prevention
We have developed an in vitro model for mouse mammary epithelial tumor cells that allows cells to be synchronized by growth factor withdrawal. These cells are being examined for various components of Ras-Raf-Erk pathway (proliferation), PI3-Kinase-PDK-AKT pathway (survival) and for the role of caspases (apoptosis). We have established the effect of organoselenium compounds (such as Se-methylselenocysteine and methylseleninic acid) on several cell cycle regulatory molecules such as RB, PCNA, PKC, p21, p27, cyclin D1, cyclin E, cyclin A, cdk2, cdk4 and cdc2 protein phosphorylations, protein-protein interactions and kinase reactions in this model. More recently, my laboratory has identified osteopontin as one of the potential targets of selenium in mouse mammary tumorigenesis. We are currently extending these findings to human breast cells. Using cDNA microarray technology and 2D-gel electrophoresis coupled with phosphorylations of various proteins of these tools, I am asking important questions: (1) what genes are turned on or off in various stages of breast cancer? And which of these genes respond to selenium treatment? (2) How can this information be combined with genomics of normal mammary gland development? (3) What are the main protein-protein interactions during mammary carcinogenesis? And how do these interactions respond to selenium treatment during the stages of immortality, transformation and neoplasia.
In our laboratory we have the expertise to grow primary cells from mouse mammary gland and human breast tissue in collagen gel that provides a 3-dimensional environment to form tubular structures. In this model system, several biological markers including ER, PR, Ki67, SMA and Her-2/neu can be studied along with signal transduction pathways and apoptosis. Furthermore, we are using a unique approach of generating a xenograft model for premalignant breast disease; growing premalignant human breast cells in collagen gel prior to transplantation in nude mice mammary fat pads. These models offer the ability to investigate the interactions of the cellular and molecular components of the organ system with promising anti-cancer agents and / or potential growth inhibitors.
Strategies for Prostate Cancer Prevention
We are investigating relevant target molecules that can be modulated to impede growth of prostate cancer using chemopreventive agents. Our hypothesis is that selenium compounds in particular may act by modulating redox-sensitive signal transduction proteins thereby regulating proliferation and / or apoptosis of these cells. Using the 2D-gel electrophoresis technique we have identified several differentially expressed spots by mass spectroscopy. These proteins include cofilin-2, HnRNP and peroxiredoxins. In addition, we are investigating the active components of selenized-yeast that may be responsible for prevention of human prostate cancer. Our goal is to determine the molecular mechanisms by which selenium inhibits prostate cancer in the TRAMP model.