TP53基因多型性對於膀胱癌的發生、侵襲性與預後的研究

TP53 Gene Polymorphism Modulates Bladder Cancer Incidence、Invasiveness and Prognosis

林鴻裕(Hung-Yu Lin)

指導教授 ： 黃俊雄

高雄醫學大學/醫學院/醫學研究所/博士(2012年)

https://doi.org/10.6832/KMU.2012.00011

摘要

p53是基因體的守護者。失去p53正常的功能使得基因體不穩定、無法有效引起細胞凋亡及消除細胞週期的抑制。p53變異是人類許多癌症中最常出現的突變類型。大約半數的惡性腫瘤，包括許多泌尿道腫瘤，都出現p53突變。在膀胱癌，p53的突變和腫瘤的分期與侵襲性有關，例如由表淺性的膀胱癌惡化成肌肉侵襲性的膀胱癌即有相關。
在碩士領域的研究上，為了確認TP53基因在膀胱尿路上皮癌的角色，我們利用聚合脢連鎖反應(PCR)/單股序列型態多形性(SSCP)和序列分析去分析南台灣地區泌尿道腫瘤組織中抗癌基因TP53的突變情形。結果發現 62.7% 膀胱尿路上皮癌的病人p53有突變情形且侵襲性腫瘤更容易有p53突變。除此之外，TP53基因Pro72對偶基因與高侵襲性和高分級腫瘤有相關。
　　而TP53基因 codon72多型性現象在20多年發現時，一直被認為是正常的變異。然而愈來愈多的證據顯示，其與各種不同癌症的發展、侵襲性與預後，乃至於化學藥物的反應性有關。由我們之前實驗室做大腸直腸癌的分析，可知同源性的Pro72對偶基因與大腸直腸癌的進展有關。而且 基因型Pro/Pro攜帶者會1.70 倍增加的危險性發展成侵襲性的腫瘤。
先前的研究已經證實p53多型性會導致蛋白質功能不同，對於癌症罹患風險與治療成效亦不同。目前對於codon 72 Arg72和Pro72的多型性對膀胱癌發生與預後的影響機轉卻仍鮮少研究提及。因此，我們先是對TP53基因codon72多型性對於各種癌症的發生、侵襲性與化學治療反應之間的矛盾做相關文獻回顧探討。結果顯示，是否codon 72的變異(Arg72 或 Pro72)是重要的或是主要的相關於各種癌症的發展、侵襲性、進展、預後和影響各種癌症化學治療的反應，到目前仍未定論且是相互矛盾的。
所以本研究第一部分，我們探討TP53基因codon72多型性，對於膀胱癌的發生、進展與預後的研究—應用結構方程模式分析膀胱癌的風險。結果為，Pro/Pro基因型的病人比非Pro/Pro 基因型的病人，有高達4.526 倍的危險發展成侵襲性腫瘤。然而，在此研究TP53基因codon72 多型性並無法預測膀胱癌的預後。同時，以結構方程模式(structure equation modeling)分析，去解決可能的使混淆作用的效果(confounding effects)是合理的。我們初步結果顯示TP53 基因codon72 多型性可能與膀胱癌的發生、進展有關但與預後無關。然而日後需更大型的研究來評估結構方程模式分析膀胱癌風險的效用為何。
而本研究第二部分，我們探討應用TP53基因codon72多形性做為膀胱癌的進展索引的研究。結果為，利用統計的觀念去計算陽性預測值(positive predictive value, PPV)和陰性預測值(negative predictive value, NPV)，去幫忙決定是否TP53基因codon72多型性，能夠被使用當做膀胱癌治療的指標。TP53基因codon72多型性與膀胱癌的進展，而非發生與預後有關。TP53基因codon72多型性的基因型Pro/Pro，顯示對於膀胱癌的進展有高的陰性預測值。因此，在臨床上可做為膀胱癌治療的進展指標。
　　然而最近幾年haplotypes的觀念逐漸升起也逐漸成形。一般認為，單一的SNP並無法完整的預測腫瘤的行為。在2007年Mechanic LE et al 分析非裔美國人的TP53經常的基因變異與肺癌危險性與預後之間的關係。結果發現，TP53 基因haplotypes可以調控肺癌的路徑，然而仍需更進一步的研究去證實。因此，本研究第三部分更進一步以haplotypes的觀念去調查TP53基因codon72 (rs1042522)多型性及其附近產生linkage disequilibrium(LD)的基因與膀胱癌的發生、進展和預後的相關性及所佔的角色。結果為，haplotype GGCC是保護的對偶基因，而CGCC是危險的對偶基因。而結果顯示，在決定TP53基因haplotype和膀胱癌發生和預後的相關性時，TP53基因codon72多型性可能扮演一個重要的角色。且進一步的功能上的分析，去確認是否TP53基因haplotype的變異和N-myc 和 NDRG蛋白質有互相影響也是需要的。
　　未來，我們期望由細胞及基因表現的的層級，來探討與證實TP53基因codon72多型性和Wrap53對膀胱癌的影響。期望能找出一種新的生物指標(biomarker)，對未來膀胱癌的發生、預測、病程惡化、化學及放射線治療成效、存活期評估、新治療藥物開發與新治療有所貢獻。

關鍵字

膀胱癌 ； TP53基因基因多型性

並列摘要

The TP53 gene is a tumor suppressor gene that acts as "guardian of the genome." Loss of p53 function confers genomic instability, impaired apoptosis and diminished cell cycle restraint. Alteration of p53 is the most common mutation in human cancer. Roughly half of all human malignancies, including many urological cancers, exhibit p53 mutations. In bladder cancer p53 mutations have been associated with higher tumor grade and advanced stage, as well as progression of superficial disease to muscle invasion.
In my preliminary study, to identify the role about TP53 gene responsive to urothelial carcinoma of urinary tract, we use PCR, SSCP and sequencing analysis to assess TP53 gene mutation in southern Taiwan bladder cancer patients. The analyzed results indicate that 62.7% of transitional cell carcinoma patients had p53 mutation. Invasive tumors are easy to be found to have p53 mutation. Besides, high grade and invasive tumor show obviously relatiohship with TP53 Pro 72 allele.
But, TP53 codon72 gene polymorphic phenomena discovered more than 20 years ago has been considered as the normal variation. However, more and more evidence demonstrated the positive relationship among TP53 condon 72 polymorphism and different kind of cancer development, progression and the prognosis, are concern as for the chemotherapeutic response. In our previous analysis for colon rectal cancer, we understood homologous Pro72 allele was relative to tumor progression. Moreover genotype Pro/Pro carrier meets the risk which 1.70 times increase to develop invasive tumor.
Previous studies indicate that the two polymorphic variants of TP53 are functionally distinct, and these differences may influence cancer risk or treatment. At present, still the few researchs mentioned regarding the mechanism about codon 72 Arg72 and the Pro72 pleomorphism to the urinary bladder carcinogenesis and the prognosis. Thus, we try to make the related literature review discussion about TP53 codon 72 gene polymorphism paradoxes in associated with various carcinoma incidences, invasiveness and chemotherapy responses firstly. The results showed that whether the variant (Arg72 or Pro72) is important or dominantly associated with cancer development、invasiveness、progression and prognosis or influences the chemotherapeutic response of various cancers is still uncertain and paradoxical.
Therefore, in this research first part, we discuss TP53 codon72 polymorphism in vulnerability, progression, and prognosis of bladder cancer with a implication of structural equation. In conclusion, a 4.526-fold risk was estimated for the patients with the Pro/Pro genotype than non-Pro/Pro genotype to develop invasive tumors. However, the extent of the TP53 codon72 polymorphism did not predict bladder cancer prognosis. Furthermore, using structural equation model to resolve possible confounding effects is reasonable. Taken together, the TP53 codon72 polymorphism may associate with bladder cancer incidence, progression, but not prognosis. Further study may need to evaluate the usefulness of the constructed model in risk assessment.
In this research second part, we study in using TP53 codon72 polymorphism as a progression index for bladder cancer in Taiwan. In conclusion, using statistical idea to calculate the positive predictive value (PPV) and negative predictive value (NPV) and determine whether TP53 Codon72 can be used as a bladder cancer management index is suitable. TP53 codon72 polymorphism is associated with bladder cancer progression rather than incidence and prognosis. Genotype Pro/Pro in TP53 codon72 polymorphism shows a high NPV for bladder cancer progression, thus it can be used clinically as a progression index in bladder cancer management.
Recently, the idea of haplotypes raised and formed gradually. Generally speaking, single nucleotide polymorphism (SNP) is unable to predict completely the tumor behavior. In 2007, Mechanic LE et al analyzes the risk and the prognosis between African Americans TP53 common genetic variation and lung cancer. The result discovered that TP53 haplotypes may regulate lung cancer pathways; however, it still needed the further research to confirm.
Therefore, the third part of this research is to use the idea of haplotype to investigate the role of polymorphisms that are predicted to be in linkage disequilibrium with codon72 (rs1042522) of TP53 in relation to bladder cancer incidence, progression and prognosis. The result indicated that haplotype GGCC was a protective allele and CGCC was a risk allele. In conclusion, the TP53 codon72 polymorphism may play a crucial role in determining the association between the TP53 haplotype and bladder cancer incidence and prognosis. To clarify whether these TP53 haplotypic variants interact with N-myc and NDRG proteins is also necessary.
In future, we expect to discuss and confirm the influence about TP53 codon 72 polymorphism and Wrap53 to the bladder cancer by cell and gene expression the level. We also expected that this research can discover one kind of new biomarker in the future to manage the cancer incidence, disease progression, chemo-radio therapy, survival rate, new drug development and new therapy strategies of bladder cancer.

並列關鍵字

bladder cancer ； TP53 gene polymorphism

參考文獻

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