Study On Genetic Instability Of KAI1,SFRP1 Gene In Chinese With Gastric Cancer

BackgroundThe malignant tumors have threatened human health and lives severely. One of the most important reasons is that the microinvasion or micrometastasis exists at the time of surgery and can not be controlled. Therefore it is very important to clarify the mechanism of invasion and metastasis, and quite significant to establish some definite molecular marker and target for the therapy.It has been investigated that the expression of anti-oncoprotein becomes low with the occurrence and metastasis of tumor, then the growth and metastasis of tumor cell are out of control. The main reason that the expression of anti-oncoprotein reduces is anti-oncogenes inactivity. To investigate the mechanism of genetic inactivity, scientists did lots of research on many anti-oncogenes such as P53, P16, et al, and found that the genetic instability, the representative of microsatellite instability and loss of heterozygosity, might be one important factor that leads to genetic mutation, the anti-oncogenes function maladjustment, and the tumor occurrence.Microsatellite instability (MSI) and loss of heterozygosity (LOH), the alteration in length and strength of short tandem repeat sequences are important molecular characteristics of many human tumors. Many researches indicated that MSI or LOH ofanti-oncogenes plays an important role in occurrence of sporadic tumor. MSI was first found in tumors of the hereditary non-polyposis colon carcinoma (HNPCC) syndrome, and then it is found in many other kinds of tumors, such as colon cancer, gastric cancer, carcinoma of endometrium, breast cancer, prostatic cancer and pancreatic cancer, et al. Many studies suggested that the occurrence of MSI increase the frequence of mutation, and moreover, it lead to mutation of genes which has great relationship with tumor which may be an important mechanism of tumor occurrence. According to Knudson's two-hit hypothesis of TSG (tumor suppressor gene) inactivation, the common chromosomal region of LOH is a potential site harbouring TSG, thus LOH is regarded as a valuable molecular genetic marker to find TSG.KAI1 (Kang AI 1) is a new gene found in recent years, which could suppress tumor metastasis either. Dong et al separated it out from prostatic cancer cell line and identified it as an anticancer gene because it could inhibit prostatic cancer cell metastasis but didn't affect its capable of causing tumors. It has been proved that in many tissue of cancer and many other cell line, there exist KAI1 gene's expression on molecular level. But the expression state in gastric carcinoma was rarely reported and of great controversial. The genetic instability of KAI1 gene in gastric cancer was rarely reported.SFRP1 (Secreted Frizzled Related Protein 1) is located on 8p11.2, which encodes a kind of secreted protein. It may directly or competely with receptor to combine to Wnt protein, which will intercept the the Wnt signal pathway. So far, dozens of highly occurring cancers ( e.g. galactophore cancer, prostate cancer, colon cancer and liver cancer) have been found disturbance of Wnt signaling. More and more scholars tend to accept that the genetics change of SFRP1 gene and expression inactivation of SFRP1 protein is a reason of the abnormal activation of Wnt pathway, which in turn triggers malignant tumor. However, few researches have been combined with clinical cases to analysis clinical significance of the genetic instability of SFRP1, as well as the the downregulation of SFRP1 protein expression.ObjectiveTo investigate MSI and LOH of locus D11S1344, D11S1326 of KAI1 gene, D8S505, D8S1722 and D8S1180 of SFRP1 gene, their effect on the expression of KAI1 and SFRP1, which would reveal the function mechanism of anti-oncogene and provide experimental basis for metastasis mechanism of cancer.Methods(1) Phenol-chloroform Method for extracting DNA from paraffin-embedded gastric cancer tissues. (2) Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and displaying band by ordinary silver stain to analyze the genetic instability of the locuses. (3) Expression of KAI1 and SFRP1 was detected by Envision immunohistochemistry. (4) Leica-Qwin computer imaging techniques was used to analyze Expression of KAI1 and SFRP1. (5) SPSS statistic software analyzed the relationship among experimental results.ResultsExpression of KAI1 protein and genetic instability of KAI1 gene in Chinese with gastric cancerâ‘ The expression rate of KAI1 protein was 55.4%(31/56). â‘¡With the infiltration of tumor, the frequency of KAI1 protein appeared decrease tendency (P<0.01). Moreover, the frequency in lymph node metastasis cases was(83.9%) significantly higher than those without (20.0%, P<0.01). Stage TNM I +II(82.8%) also exhibited higher frequency of KAI1 protein than stage TNM III+IV(25.9%, P<0.01).â‘¢However, none of 56 gastric cancers showed LOH or MSI at locus D11S1344 and D11S1326.Genetic instability of SFRP1 gene in Chinese with gastric cancerNone of 70 gastric cancers showed LOH or MSI at locus D8S505 , D8S1722 and D8S1180.Conclusionsâ‘ There is rare loss of hererozygosity or microsatellite instability in locus D11S1326 and D11S1344 of KAI1 gene in gastric carcinoma. The expression of KAI1 protein has great relationship with the infiltration of tumor, the lymph node metastasis and the prognosis of gastric carcinoma.So the level of KAI1 protein expression may be an important mark of metastasis possibility of cancer cells.â‘¡There is rare loss of hererozygosity or microsatellite instability in locus D8S505, D8S1722 and D8S1180 of KAI1 gene in gastric carcinoma. The genetic instability of SFRP1 gene may not be the major factor that affects the prognosis of gastric carcinoma. Among different malignant tumors, the mechanism of how the genetic instability of SFRP1 suppresses the cancer also could be distinct.