研究背景: ICAT (inhibitor of b-catenin and TCF) 和HBP1 (HMG-box transcription factor 1) 抑癌基因分別位於染色體1p36.2和7q31的區域。ICAT和HBP1兩個蛋白質屬於Wnt/b-catenin訊號傳遞路徑的成員，經由拮抗b-catenin/TCF (T-cell factor) 複合體的共同活化作用而抑制Wnt/b-catenin訊號傳遞路徑的功能。因此，本研究假設若ICAT或HBP1有變異的情形發生，可能會造成Wnt/b-catenin訊號傳遞路徑的過度活化而導致腫瘤發生。材料與方法: 我們分析了95位非小細胞肺癌 (non-small cell lung cancer, NSCLC) 病人的ICAT和HBP1蛋白表現、mRNA表現及啟動子過度甲基化情形，並將變異結果和臨床病歷資料做相關的統計分析。我們使用免疫組織染色法 (immunohistochemistry, IHC)，觀察病人ICAT和HBP1蛋白，再以反轉錄-聚合酵素鏈反應 (Reverse-transcriptase polymerase chain reaction, RT-PCR) 分析組織細胞中ICAT和HBP1基因mRNA轉錄是否異常，續以聚合酵素鏈反應為基礎的甲基化分析 (methylation-specific PCR, MSP) 偵測ICAT和HBP1基因的啟動子過度甲基化頻率。結果: 本研究發現95位NSCLC病人中ICAT和HBP1蛋白低表達頻率分為別26% (25/95) 和31.6% (30/95)，ICAT和HBP1 mRNA低表達頻率分別為37.9% (36/95) 和33.7% (32/95)，而ICAT和HBP1基因啟動子甲基化頻率分別為36.8% (35/95) 和45.3% (43/95)；ICAT和HBP1蛋白質/mRNA、mRNA/啟動子甲基化、蛋白質/啟動子甲基化表現彼此間都呈現統計上的顯著相關性 (P<0.05)；我們也發現，原本有HBP1基因變異的肺癌細胞株在經過去甲基化藥物5’-aza-2’-deoxycytidine的處理之後，會使肺癌細胞株HBP1基因啟動子去甲基化與mRNA蛋白質表現量上升。另外，將ICAT和HBP1變異情形和臨床病理資料作統計相關性分析，結果發現，HBP1 mRNA低表達多發生在抽菸 (P=0.035) 及鱗狀上皮細胞肺癌病人 (P=0.021)。為了探討ICAT和HBP1變異是否會引發Wnt/-catenin訊號傳遞路徑的過度活化而導致其目標基因過度表現，因此本研究亦檢測了50位NSCLC病人之Wnt/-catenin目標基因 MMP7 (matrix metallopeptidase 7) 的表現與ICAT和HBP1蛋白失去活性的相關性，研究結果顯示-catenin過度表現同時MMP7 mRNA亦過度表現的病人之間達統計上相關性 (P=0.008)，這些病人中同時有HBP1蛋白失去活性的病例之間統計上亦達邊緣顯著相關 (P=0.069)。結論: 由本研究結果顯示，ICAT和HBP1發生變異，確實在肺癌形成過程中扮演一個重要的角色，其變異主要機制為啟動子過度甲基化。因為ICAT和HBP1變異會失去拮抗b-catenin/TCF複合物活化下游基因的能力，而導致細胞中b-catenin/TCF目標基因，如：MMP7過度表現，進一步導致肺腫瘤的發生或轉移。本研究亦為在癌症病人中首篇完整探討ICAT和HBP1蛋白表現、RNA表現、DNA啟動子過度甲基化的研究論文。

1. Department of Health.Statistics of causes of death (2006).
2. Chen CJ, You SL, Lin LH, Hsu WL, Yang YW. Cancer epidemiology and control in Taiwan: a brief review. Jpn J Clin Oncol 2002;32 Suppl:S66-81.
3. Tammemagi CM, Neslund-Dudas C, Simoff M, Kvale P. Smoking and lung cancer survival: the role of comorbidity and treatment. Chest 2004;125:27-37.
4. Honma H. [Classification of lung cancer by disease stage, symptom type and histological type]. Naika 1966;18:832-6.
5. Borczuk AC, Gorenstein L, Walter KL, Assaad AA, Wang L, Powell CA. Non-small-cell lung cancer molecular signatures recapitulate lung developmental pathways. Am J Pathol 2003;163:1949-60.
6. De Vuyst P, Dumortier P, Jacobovitz D, Emri S, Coplu L, Baris YI. Environmental asbestosis complicated by lung cancer. Chest 1994;105:1593-5.
7. Samet JM. Environmental causes of lung cancer: what do we know in 2003? Chest 2004;125:80S-3S.
8. Wright K, Wilson P, Morland S, Campbell I, Walsh M, Hurst T, Ward B, Cummings M, Chenevix-Trench G. beta-catenin mutation and expression analysis in ovarian cancer: exon 3 mutations and nuclear translocation in 16% of endometrioid tumours. Int J Cancer 1999;82:625-9.
9. Gazzeri S, Brambilla E, Caron de Fromentel C, Gouyer V, Moro D, Perron P, Berger F, Brambilla C. p53 genetic abnormalities and myc activation in human lung carcinoma. Int J Cancer 1994;58:24-32.
10. Naylor SL, Johnson BE, Minna JD, Sakaguchi AY. Loss of heterozygosity of chromosome 3p markers in small-cell lung cancer. Nature 1987;329:451-4.
11. Hart MJ, de los Santos R, Albert IN, Rubinfeld B, Polakis P. Downregulation of beta-catenin by human Axin and its association with the APC tumor suppressor, beta-catenin and GSK3 beta. Curr Biol 1998;8:573-81.
12. Polakis P. Wnt signaling and cancer. Genes Dev 2000;14:1837-51.
13. Shiina H, Igawa M, Shigeno K, Terashima M, Deguchi M, Yamanaka M, Ribeiro-Filho L, Kane CJ, Dahiya R. Beta-catenin mutations correlate with over expression of C-myc and cyclin D1 Genes in bladder cancer. J Urol 2002;168:2220-6.
14. Sunaga N, Kohno T, Yokota J. [Wnt signaling abnormalities in human lung cancer]. Nippon Rinsho 2002;60 Suppl 5:733-6.
15. Brabletz T, Jung A, Dag S, Hlubek F, Kirchner T. beta-catenin regulates the expression of the matrix metalloproteinase-7 in human colorectal cancer. Am J Pathol 1999;155:1033-8.
16. Tago K, Nakamura T, Nishita M, Hyodo J, Nagai S, Murata Y, Adachi S, Ohwada S, Morishita Y, Shibuya H, Akiyama T. Inhibition of Wnt signaling by ICAT, a novel beta-catenin-interacting protein. Genes Dev 2000;14:1741-9.
17. Daniels DL, Weis WI. ICAT inhibits beta-catenin binding to Tcf/Lef-family transcription factors and the general coactivator p300 using independent structural modules. Mol Cell 2002;10:573-84.
18. Lavender P, Vandel L, Bannister AJ, Kouzarides T. The HMG-box transcription factor HBP1 is targeted by the pocket proteins and E1A. Oncogene 1997;14:2721-8.
19. Shih HH, Tevosian SG, Yee AS. Regulation of differentiation by HBP1, a target of the retinoblastoma protein. Mol Cell Biol 1998;18:4732-43.
20. Xiu M, Kim J, Sampson E, Huang CY, Davis RJ, Paulson KE, Yee AS. The transcriptional repressor HBP1 is a target of the p38 mitogen-activated protein kinase pathway in cell cycle regulation. Mol Cell Biol 2003;23:8890-901.
21. Berasi SP, Xiu M, Yee AS, Paulson KE. HBP1 repression of the p47phox gene: cell cycle regulation via the NADPH oxidase. Mol Cell Biol 2004;24:3011-24.
22. Fong CT, Dracopoli NC, White PS, Merrill PT, Griffith RC, Housman DE, Brodeur GM. Loss of heterozygosity for the short arm of chromosome 1 in human neuroblastomas: correlation with N-myc amplification. Proc Natl Acad Sci U S A 1989;86:3753-7.
23. Tanaka K, Yanoshita R, Konishi M, Oshimura M, Maeda Y, Mori T, Miyaki M. Suppression of tumourigenicity in human colon carcinoma cells by introduction of normal chromosome 1p36 region. Oncogene 1993;8:2253-8.
24. Genuardi M, Tsihira H, Anderson DE, Saunders GF. Distal deletion of chromosome Ip in ductal carcinoma of the breast. Am J Hum Genet 1989;45:73-82.
25. Fang W, Piao Z, Simon D, Sheu JC, Huang S. Mapping of a minimal deleted region in human hepatocellular carcinoma to 1p36.13-p36.23 and mutational analysis of the RIZ (PRDM2) gene localized to the region. Genes Chromosomes Cancer 2000;28:269-75.
26. Sekiya T, Nakamura T, Kazuki Y, Oshimura M, Kohu K, Tago K, Ohwada S, Akiyama T. Overexpression of Icat induces G(2) arrest and cell death in tumor cell mutants for adenomatous polyposis coli, beta-catenin, or Axin. Cancer Res 2002;62:3322-6.
27. Reifenberger J, Knobbe CB, Wolter M, Blaschke B, Schulte KW, Pietsch T, Ruzicka T, Reifenberger G. Molecular genetic analysis of malignant melanomas for aberrations of the WNT signaling pathway genes CTNNB1, APC, ICAT and BTRC. Int J Cancer 2002;100:549-56.
28. Koike M, Takeuchi S, Yokota J, Park S, Hatta Y, Miller CW, Tsuruoka N, Koeffler HP. Frequent loss of heterozygosity in the region of the D7S523 locus in advanced ovarian cancer. Genes Chromosomes Cancer 1997;19:1-5.
29. Zenklusen JC, Weitzel JN, Ball HG, Conti CJ. Allelic loss at 7q31.1 in human primary ovarian carcinomas suggests the existence of a tumor suppressor gene. Oncogene 1995;11:359-63.
30. Zenklusen JC, Thompson JC, Troncoso P, Kagan J, Conti CJ. Loss of heterozygosity in human primary prostate carcinomas: a possible tumor suppressor gene at 7q31.1. Cancer Res 1994;54:6370-3.
31. Zenklusen JC, Bieche I, Lidereau R, Conti CJ. (C-A)n microsatellite repeat D7S522 is the most commonly deleted region in human primary breast cancer. Proc Natl Acad Sci U S A 1994;91:12155-8.
32. Zenklusen JC, Thompson JC, Klein-Szanto AJ, Conti CJ. Frequent loss of heterozygosity in human primary squamous cell and colon carcinomas at 7q31.1: evidence for a broad range tumor suppressor gene. Cancer Res 1995;55:1347-50.
33. Koike M, Tasaka T, Spira S, Tsuruoka N, Koeffler HP. Allelotyping of acute myelogenous leukemia: loss of heterozygosity at 7q31.1 (D7S486) and q33-34 (D7S498, D7S505). Leuk Res 1999;23:307-10.
34. Tevosian SG, Shih HH, Mendelson KG, Sheppard KA, Paulson KE, Yee AS. HBP1: a HMG box transcriptional repressor that is targeted by the retinoblastoma family. Genes Dev 1997;11:383-96.
35. Sampson EM, Haque ZK, Ku MC, Tevosian SG, Albanese C, Pestell RG, Paulson KE, Yee AS. Negative regulation of the Wnt-beta-catenin pathway by the transcriptional repressor HBP1. Embo J 2001;20:4500-11.
36. Howe LR, Brown AM. Wnt signaling and breast cancer. Cancer Biol Ther 2004;3:36-41.
37. Tseng RC, Chang JW, Hsien FJ, Chang YH, Hsiao CF, Chen JT, Chen CY, Jou YS, Wang YC. Genomewide loss of heterozygosity and its clinical associations in non small cell lung cancer. Int J Cancer 2005;117:241-7.
38. Kase S, Sugio K, Yamazaki K, Okamoto T, Yano T, Sugimachi K. Expression of E-cadherin and beta-catenin in human non-small cell lung cancer and the clinical significance. Clin Cancer Res 2000;6:4789-96.
39. Lee MN, Tseng RC, Hsu HS, Chen JY, Tzao C, Ho WL, Wang YC. Epigenetic inactivation of the chromosomal stability control genes BRCA1, BRCA2, and XRCC5 in non-small cell lung cancer. Clin Cancer Res 2007;13:832-8.
40. Dinse GE, Lagakos SW. Nonparametric estimation of lifetime and disease onset distributions from incomplete observations. Biometrics 1982;38:921-32.
41. Morin PJ. beta-catenin signaling and cancer. Bioessays 1999;21:1021-30.
42. Fearnhead NS, Britton MP, Bodmer WF. The ABC of APC. Hum Mol Genet 2001;10:721-33.
43. Satoh S, Daigo Y, Furukawa Y, Kato T, Miwa N, Nishiwaki T, Kawasoe T, Ishiguro H, Fujita M, Tokino T, Sasaki Y, Imaoka S, Murata M, Shimano T, Yamaoka Y, Nakamura Y. AXIN1 mutations in hepatocellular carcinomas, and growth suppression in cancer cells by virus-mediated transfer of AXIN1. Nat Genet 2000;24:245-50.
44. Gasparian AV, Laktionov KK, Belialova MS, Pirogova NA, Tatosyan AG, Zborovskaya IB. Allelic imbalance and instability of microsatellite loci on chromosome 1p in human non-small-cell lung cancer. Br J Cancer 1998;77:1604-11.
45. Yee AS, Paulson EK, McDevitt MA, Rieger-Christ K, Summerhayes I, Berasi SP, Kim J, Huang CY, Zhang X. The HBP1 transcriptional repressor and the p38 MAP kinase: unlikely partners in G1 regulation and tumor suppression. Gene 2004;336:1-13.