Study on Expression of Annexin A Family in Sporadic Colorectal ...

[Abstract]

The annexins are classically characterized as a family of proteins capable of binding to acidic phospholipids in a Ca2+-dependent manner and they appear to be widely distributed throughout nature. Up to this day, there are total of twelve annexins have been found in higher vertebrates and form the A family of the annexins. In most biological contexts studied, the annexins are highly abundant proteins, reaching the level as high as 0.5% to 2% of the total cellular proteins and all these proteins present a homologous core structure and a highly variable N-terminus. Based on their Ca2+-dependent interaction with phospholipids and membranes, many physiological functions have been described for the annexins including endocytosis, exocytosis, cell-cell or cell-matrix interaction, formation of ion channels, inhibition of phospholipase A2 and so on. Unfortunately, there has not been a definitive description of any physiological role played by these annexins in more than 20 years of study. Although any exact in physiological function has not been described for the annexins, there are great deals of evidence to suggest that they are involved in the pathogenesis of many different cancers. In many cancers, there is sharp up-regulation of annexins in both mRNA and protein levels. On the other hand, there is data indicating that down-regulation of annexins may play a significant role in tumorigenesis and metastasis of other types of cancer. However, the precise role played by the annexins in the pathogenesis of tumor is still unknown.Colorectal cancer (CRC) is the fourth commonest malignancies after lung, breast and prostate in the world and the distant metastatic disease is a frequent event which remains a major cause of cancer-related death, especially metastasis of the liver. The biological properties of metastasis can be quite different from those of the primary tumour and the conventional paradigm of hepatic metastasis in colorectal cancer is based on a multi-step tumor genesis model defined by a series of progressive somatic genetic alterations, which give malignant cells the ability to proceed through the many phases of metastasis. The molecular mechanisms involved in these events are diverse and complex, which limits our understanding and our effectiveness to develop novel therapies. Therefore, in our opinion, it is necessary to analyze the expression of A family members in colorectal cancer and their mechanism in T tumorigenesis.Above all, we succeeded in cloning full length sequence of human annexin A1, A2 and A5 coding regions of from human placenta by RT-PCR. Then we constructed and identified recombinant eukaryotic expression vectors of annexin A1, A2 and A5.With the help of the department of colorectal surgery of changhai hospital, 36 tumor samples with complete clinical data were selected. At the same time 35 normal tissues (obtained from patients with benign colorectal diseases) were chosen as normal control. We firstly detected p53 and Ki-67 in tumor tissues by immunoassaying and split all tumor samples into two groups separately according to the detection of p53 or Ki-67. Then the mRNA and protein levels of annexin A5 in each sample were analyzed by real-time quantitative PCR and immunohistochemistry. We found that there is an up-regulation of annexin A5 in colorectal cancer. We also found the up-regulation has a positive correlation with the mutation of p53 or Labeling Index (Ki-67) in tumor tissues. Besides, the mutation of p53 in tumor tissues has a negative correlation with Labeling Index (Ki-67). Our study indicates that annexin A5 might be used as an assistant clinicopathological biomarker in cancer diagnosis and the up-regulation of annexin A5 in colorectal cancer might be related to the malignant proliferation of tumor cells. Based on the study in tissues, we selected five human colon adenocarcinoma cell lines and analyzed their metastatic potentials by invasion/migration assay (higher metastatic potential: SW620, LoVo; generic metastatic potential: HCT116; SW480; lower metastatic potential: HT-29). Then we analyzed expression of annexin A1, A2 and A5 mRNA and protein levels in cell lines by real-time PCR and western blot. We found that the order of A1, A2, A5 expression level from high to low was separately HT-29 > SW620 > LoVo > HCT116 > SW480, SW480 > HT-29 > HCT116 > LoVo and SW620, LoVo > HT-29 and HCT116 > SW480 and SW620. Our results indicated that annexin A1 and A2 may play important roles in tumor metastasis and annexin A5 may not work in metastasis but apoptosis. We also imagine that different annexins may be complementary in functionWe analyzed expression of main members of annexin A family in spocitic colorectal cancer and their mechnium in tumorigenesis. Our work would make the groundwork for further researches on physiological functions of the annexins and their role in tumorigenesis.

Title: Study on Expression of Annexin A Family in Sporadic Colorectal Cancer and Their Mechanism in Tumorigenesis

Category: Cervix Cancer

Filename: Study on Expression of Annexin A Family in Sporadic Colorectal Cancer and Their Mechanism in Tumorigenesis.pdf

Pages: 194

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