Abstract. Breast cancer represents the second leading cause of cancer-related deaths in the world. There is increasing evidence that perturbation of cell cycle regulation is an important contributing factor to various cancer progression stages. There are key checkpoints in the cell cycle involving various regulatory proteins. The relationship between these cell cycle regulatory proteins and cell cycle arrest by cyclooxygenase (COX) inhibitors during neoplastic progression remains largely unknown. Preclinical studies and epidemiological investigations have consistently shown that nonsteroidal anti-inflammatory drugs have some anti-proliferative and anti-oxidative stress response on various tumors. In this study, the effect of etodolac, a 1,8-diethyl-1,3,4,9-tetrahydropyrano (3,4-ß) indole-1-acetic acid on signaling pathways was investigated by examining the differential expression of various cell cycle regulatory protein genes. A human cell cycle gene array was used to profile the expression of 96 genes involved in the cell cycle regulation. Differentially expressed genes were highly altered by etodolac treatment. Twenty-six genes were up-and 20 down-regulated with 0.5 and 2 mM etodolac treatment, respectively. Seven genes (ATM, BAX, CCNA2, CDC27, RAD50 and p21) were prominently altered, and six (ATM, CCND2, CCNF, CDC20, CDK1A and RAD50) were commonly altered with both concentrations. This finding indicated that etodolac could play a critical role on cancer cells by inducing cell death.
IntroductionBreast cancer represents the second leading cause of cancerrelated deaths in the United States and other Western countries; accounting for about 30-40% of all newly diagnosed cancers (1,2). Hereditary breast cancer accounts for just 5-10% of cases. It is generally believed that a family history of breast cancer and hormonal imbalances also contributes to the development of breast cancer (3,4). The etiology of breast cancer remains unknown, however, a profound and diverse number of factors including developmental, genetic, nutrition, chemotherapy, hormones, the environment and other yet undetermined factors have been implicated as risk factors for mammary tumorigenesis (5-8).The malignant breast cell phenotype develops as a result of a multi-step process, requiring multiple genetic mutations (9-12). These mutations contribute to a cell that is increasingly characterized by uncontrolled proliferation, deregulated production of growth factors, non-responsiveness to extracellular anti-proliferative signals, anchorage independence, metastatic potential and resistance to antineoplastic agents. Recent advances in the molecular biology of breast cancer have identified various genes associated with tumorigenesis (13,14). The development and progression of neoplastic transformation and the experimental reversal of tumorigenicity are accompanied by complex changes in patterns of gene expression. Complicated events are required for normal cells to change their behavior and these events involve the interaction between genes and pos...