散发性结直肠癌22q13区域杂合缺失的精细定位分析

目的在染色体高频杂合缺失区22q13精细定位，以筛查可能与结直肠癌相关的肿瘤抑制基因。方法荧光标记的微卫星引物与83例结直肠癌的肿瘤和正常组织进行PCR反应。产物在ABI Prism 377自动荧光测序仪进行电泳、扫描以及杂合缺失分析。其结果与临床病理因素进行相关性检验。结果8个位点平均杂合缺失率为35．6％。发现两个高频缺失区域：一个在D22S1171和D22S274之间，约2．7厘摩（cM）；另一个在D22S1160和D22S1149位点之间，约1．8cM。D22S1171位点与肿瘤发生部位显著相关（P=0．020）；D22S114位点与肝转移显著相关（P=0．008）；D22S1160位点与淋巴结转移显著相关（P=0．016）；其余位点与临床病理因素无显著相关性（P〉0．05）。筛选发现ARHGAP8基因和PPARA基因可能是肿瘤抑制基因。结论散发性结直肠癌22q13区域存在两个高频杂合缺失区，分别约2．7cM及1．8cM。ARHGAP8基因和PPARA基因可能是22q13区域与散发性结直肠癌相关的肿瘤抑制基因。

Refined deletion mapping of loss of heterzygosity on 22q13 in sporadic colorectal carcinoma

OBJECTIVE: To screen the candidate TSGs on 22q13 involved in sporadic colorectal cancer. METHODS: The DNA samples of 83 cases with colorectal carcinoma and normal tissues were analyzed using eight fluorescent labeled polymorphic microsatellite markers by PCR. PCR products were eletrophoresed on an ABI 377 DNA sequencer. Genescan 3.7 and Genotype 3.7 software was used for LOH scanning and analysis. Comparison between LOH frequency and clinicopathological factors were performed by chia2 test. RESULTS: The prevalence of LOH was 35.58%, and the average hereditary distance was 1.9 cM. The highest frequency of LOH (D22S1160 locus) and the lowest (D22S1170 locus) were 64.71% and 20%, respectively. Two obvious LOH regions were detected: One between D22S1171 locus and D22S274 locus (about 2.7 cM); another between D22S1160 and D22S1149 locus (about 1.8 cM). Furthermore,significant differences were observed between the frequency of LOH on D22S1171 locus and tumors location (P=0.020), the frequency of LOH on D22S114 locus and liver metastasis (P=0.008), the frequency of LOH on D22S1160 locus and lymph node metastasis (P=0.016). No significant differences were found between LOH on other loci and those factors above. Gene function screening revealed that ARHGAP8 and PPARA gene were involved in carcinogenesis. CONCLUSIONS: Two obvious high frequency LOH regions are detected by refined deletion mapping. One locates between D22S1171 locus and D22S274 locus (about 2.7 cM); another locates between D22S1160 and D22S1149 locus (about 1.8cM), ARHGAP8 and PPARA gene may be TSGs which contribute to carcinogenesis and progression of sporadic CRC on 22q13 region.