2005 Abstracts: PDX-1 and p16 Expression Levels Are Elevated in Human Colon Cancer
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PDX-1 and p16 Expression Levels Are Elevated in Human Colon Cancer
Zhijun LI, Shihe Liu, Xiao-Ping Wang, F. Charles Brunicardi, Baylor College of Medicine, Houston, TX
Colon Cancer is the third most common cancer in the United States and accounts for an estimated 10.06% of all mortality caused by all cancer in 2004. It is important to identify colon cancer related oncogenes for potential new treatment strategies. The purpose of this study was to examine the transcription factor PDX-1 expression pattern in colon cancer samples at different stages and its association with other cell proliferation regulators.
Human colon cancer specimens, metastases, and matched benign tissues (n=16) were collected and fixed in 4% paraformaldehyde. The expression levels and distribution of PDX-1 was determined using immunohistochemistry analysis. Image was quantified using SimplePCI software. Tissue samples were homogenized and western blot analysis was performed. Total RNA was isolated using Ambion?RNAqueous?kit and cDNA was prepared using Invitrogen?SuperScript?III System. Human lung cancer cell (A549) and human pancreatic cancer cell (PANC-1 and MIA PaCa-2) were used as controls. Primers for p16, S100p, EGR-1 and PDX-1 were synthesized. RT-PCR analysis was carried out. The transcription level of the house keeping gene HPRT was used as an internal control. Gene expression pattern was analyzed using agarose gel electrophorasis and quantified with UVP?Bioimaging system? Immunohistochemistry analysis demonstrated that PDX-1 was highly expressed in colon cancer specimens and in matched benign tissues from the same patient. Immunostaining also indicated that the expression level of PDX-1 protein was associated with cell proliferation status. Compared with the levels of HPRT, RT-PCR results indicated an increase of PDX-1 transcription levels in the metastases, followed by a decreased level in cancer specimen and the lowest expression level in benign samples. Similar expression patterns were also found in p16 transcription levels. There was no significant variation in the expression levels of EGR1 among these groups. The highest expression level of S100p was found in the cancer specimen, with reduced amount in the metastastic samples and the lowest level in the benign specimens. Metastases also have higher expression levels of SSTR5 than both colon cancer and benign tissues, which is correlated with that of PDX-1 and p16 expression patterns. In addition, the highest level of somatostatin receptor 1 was found in the benign tissues, with the lowest levels in cancer specimens. There was no significant variation of SSTR2 expression among al
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