The Anti-tumor Effects Of The 1,5-diarylpyrazole Class Of COX-2 Selective Inhibitors In Colon Carcinoma Cells And Its Mechanisms

Colon cancer remains a significant health concern in the modern world, and is one of the leading causes of cancer-related deaths in our country. Despite the development of new strategies of aggressive surgical and adjuvant therapy, little progress has been made in the successful management of advanced diseases. Therefore, much hope is currently placed on chemo-prevention. A dramatic recent development in oncology is the recognition that nonsteroidal anti-inflammatory drugs (NSAIDs) share the property of inhibiting the COX enzymes and can delay or prevent certain kinds of cancer, including colon cancer. Cyclooxygenases (COX) are key enzymes in the conversion of arachidonic acid (AA) to prostaglandins (PGs). In the classic hypothesis there are two isoforms of COX, COX-1 and COX-2, which are very similar in their structure but are very different in their expression pattern and function within organisms. COX-1 is constitutively expressed in many cells and tissues, and is thought to be responsible for maintaining gastric mucosal integrity. COX-2 is an inducible isoform, the expression of which is stimulated by a variety of agents such as cytokines, growth factors, and tumor promoters. We know that prolonged use of classical NSAIDs may result in untoward gastrointestinal side effects because they inhibit COX-2 and COX-1 simultaneously. The inhibition of COX-1 is thought to lead to bleeding or ulceration in the gastrointestinal tract. Thus, COX-2selective inhibitors are becoming a very promising target in this field. Epidemiological studies have demonstrated that chronic intake of aspirins and other NSAIDs can decrease the incidence of colon cancer by 40-50%. Experimental studies have shown that COX-2 inhibitors can inhibit the growth of colon adenoma and induce the carcinoma cells to undergo apoptosis, but its mechanism is still unclear. Therefore our experiments were designed to investigate the effects of Celecoxib (a selective COX-2 inhibitor) on the growth of human colon carcinoma cells and to explore its possible molecular mechanism and cellular signal transduction. Finally, we attempted to observe the inhibition effects of the new 1,5-diarylpyrazole class of COX-2 selective inhibitors synthesized in our laboratory on the growth of SW-1116 cells in vitro to study whether PC407, the most potent of the nine compound candidates, could induce colon carcinoma cell line SW-1116 to undergo apoptosis.1. The effects of celecoxib on the growth and apoptosis in human colon carcinoma cells SW-1116 and its possible mechanisms. COX-2 expression in the SW-1116 cells was evaluated by immunohistochemical staining. Inhibition of proliferation was measured by MTT assay. Morphological assessment of apoptosis was performed with fluorescence microscopy. The amount of apoptotic cells was measured by flow cytometry. The release of Cytochrome c and the activation of caspase-3 were demonstrated by western blot. The results showed that both aspirin and Celecoxib inhibited SW-1116 cells proliferation and induced them to undergo apoptosis, with celecoxib proving to be much more potent than aspirin. However the concentration of drugs needed for growth inhibition of cells was much higher than the one to inhibit COX-2 enzyme activity. This might suggest that the COX-2 independent effect exists in SW-1116 cells. The analysis of western blot showed it might induce cells to undergo apoptosis through induction of Cytochrome c release and caspase-3 activation.2. The effects of celecoxib on the growth and apoptosis in human colon carcinoma cells SW-480 and its possible mechanisms. COX-2 expression in the SW-480 cells was evaluated by immunohistochemical staining. Inhibition of proliferation was measured by MTT assay. Morphological assessment of apoptosis was performed by electron microscopy. The DNA content of cells was measured by flow cytometry. The DNA fragmentation was visualized by agarose gel electrophoresis. The release of Cytochrome c and the activation of caspase-3 were demonstrated by western blot. The results sho...