动物造模,结肠癌 z-bo 2022-02-03 462

　　The gene knockout mouse model uses transgenic technology to artificially knock out related genes that inhibit tumorigenesis, development and metastasis, and eliminates homologous recombination and Cre/loxP-induced conditional knockout system methods. Currently, gene knockout colorectal cancer models are associated with multiple adenomatous polyposis (APC) family genes and hereditary non-polyposis colorectal cancer germline mismatch repair genes MSH2 and MLHI. The genetically engineered mouse model developed has been widely used in the study of hereditary non-polyposis colorectal cancer (HNPCC) and familial polyadenocarcinoma, and plays an important role in colorectal cancer metastasis and drug treatment experiments.

　　[Forming mechanism]

　　1, Min (multiple enteric neuropathy) mice Min mice are Apc gene mutant mice with multiple intestinal adenomas, and are considered to be an ideal model for familial adenomatous polyposis (FAP). The ape gene is an important tumor suppressor gene in the Wnt pathway. It is not only an important signaling pathway in animal embryonic development, but also plays an abnormal role in the development of colorectal tumors. The main genetic feature of Min mice is that one of the two chains of the Apc gene has a nonsense mutation at the 850th codon, that is, there is an inversion (T→A) at the 2549th base, that is, this is the code Sub-code. (TTG) is converted to a stop codon (TAG), the protein is truncated, and the tumor suppressor gene Apc cannot function effectively. Recently, it was also discovered that Min1 mice have genetic sites that control the number of tumors, such as Mom1, Mom2, and Mom7. Among them, Mom1 is located at the far end of chromosome 4 and is highly homologous to human chromosome 1 lp35-36. In human colorectal cancer, this area is usually an area of loss of heterozygosity. Some Min mice with Mom2 gene have the property of suppressing intestinal tumors.

　　2, HNPCC mouse model HNPCC is a hybridization loss caused by the inactivation of APC gene, and the mutation of mismatch genes (MLH-1, MLH-2, MLH-6, PMS-1, PMS-2) leads to genetic instability. The reason HNPCC gene is characterized by unstable short tandem repeats, also called microsatellites, which are involved in the formation of advanced tumors. When you use gene knockout technology to knock out the MLH-1 or MLH-2 genes in homozygous mice, lymphocytes become tumors. It also tends to be gastrointestinal tumors and can be used as a good model for studying HNPCC.

　　3. With the advent of new technologies, mouse models with FAP restrictions can activate or inactivate somatic genes in specific tissues at a specific time. For example, in Apc model mice, after adenovirus infects the colon and expresses Cre recombinase, the Apc gene can be deleted to inhibit the conditional expression of B-catenin and cause the formation of gastrointestinal polyps.

　　[Model Features]

　　1. Min mice ① Min mouse intestinal tumors are prone to loss of Apc heterozygosity, that is, normal Apc + Apc alleles are missing, which can also be seen in microadenoma (a lesion that cannot be easily detected by the naked eye in the early stage of adenoma). .. Induced by the pro-inflammatory agent dextran sodium sulfate (DSS), tumors can form rapidly in the large intestine of Min mice (within 4 weeks). The amount and rate of formation are better than untreated Min. The mouse is here (2) The advantage of Min mice is that the genetic background of the occurrence and development of adenomas is the same, and there is no genetic heterogeneity in colon tumors. (3) The natural survival time of Min mice is usually 120 days or less, and is often accompanied by the characteristics of chronic anemia, such as an increase in reticulocytes and a decrease in the number of red blood cells. Can use anemia characteristics to screen Apc (Mir/+) mice (accuracy rate can reach 100%). Homozygous Apc (Min/Min) mice are extremely lethal, difficult to reproduce, and some occur in the uterus of female mice. Abnormal development, miscarriage and death. The smallest mice are also common in melena, rectal prolapse, splenomegaly, and hyperlipidemia. In addition, some female Min mice may develop breast tumors. Recently, it has also been reported that Min mice are susceptible to gastric cancer under the treatment of carcinogen AOM. Therefore, if the Min mouse is modified, it may be a good model for studying various diseases.

　　2, MLH-1-/- mice are a mouse model of hereditary non-polyposis colorectal cancer, which is prone to gastrointestinal tumors. MLH-2-/-gene-deficient homozygous mice are prone to lymphoma and intestinal tumors due to inactivation of the APC gene.

　　3. Mouse model with FAP restriction. The restricted mouse model can mimic FAP syndrome well. It is characterized by spontaneous tumors, is highly predictable and predictable, and is not immunogenic. It can grow in immune-competent mice.

　　[Model Evaluation and Application] The gene knockout models established so far are mainly aimed at the APC family genes and germline mismatch modifier genes of hereditary non-polyposis colorectal cancer. However, the tumor development of these mice is completely different from HNPCC colorectal cancer, so it is not suitable for the screening and treatment of anti-tumor drugs. Its applicability needs further research, and the model needs to be continuously optimized. In the transgenic animal tumor model, the development of the tumor is theoretically the same as the primary tumor. Any animal can be modeled, but the current research on oncogenes and tumor suppressor genes themselves needs to be explained in detail. Therefore, the model is not ideal enough to be popularized in the short term. Currently, it can only be used as a development direction. With the in-depth study of tumor etiology and the wide application of transgenic technology, this method has gradually matured.