台灣南部地區攝護腺癌分子流行病學之研究

在台灣, 攝護腺癌的發生率呈逐年增加的趨勢，在民國91年, 攝護腺癌已成為台灣地區主要癌症死亡原因的第八位，共導致750人死亡。相較於其他常見的癌症, 國內有關攝護腺的分子流行病學相關研究缺乏，為公共衛生的重要課題，因此我們應投注更多的努力以研究攝護腺癌的危險因子和基因易感性, 進而預防攝護腺癌的發生! 攝護腺癌確定的危險因子包括:年齡, 種族, 及家族史。攝護腺癌的發生率在不同種族間有顯著的差異性, 非裔美國人最高,白種人次之, 亞洲人最低。這表示, 不同種族間基因的變異, 環境暴露與生活形態因子可能在攝護腺癌的發生扮演重要的角色。然而文獻上少有研究報告台灣地區國人護腺癌的危險因子, 文獻回顧僅得在北台灣一較小規模研究(攝護腺癌個案組90位, 對照組180位)。因此, 本研究第一部份, 我們在台灣南部進行一個案對照研究, 探討國人攝護腺癌的相關危險因子。在2000年12月至2003年9月期間, 我們從高雄醫學大學附設中和紀念醫院與高雄榮民總醫院共收集了195位新診斷,病理證實的攝護腺癌個案; 另收集了291年齡配對(?b2歲), 血清PSA 小於4 ng/ml的健康男性對照組。我們也收集173位有明顯攝護腺肥大症狀、肛門指診, 超音波顯示攝護腺有明顯肥大, 若PSA>4 ng/ml則經切片排除惡性的攝護腺肥大組作進一步比較。以結構式問卷調查其社會人口學特徵、生活型態、飲食習慣、環境暴露…等因子。以卡方檢定及邏輯回歸分析探討攝護腺癌的危險因子。在以多變項邏輯式回歸分析比較個案組與健康對照組之後; 發現顯著的危險因子與保護因子分別為: 有規律運動習慣會有較低的攝護腺癌危險性(OR=0.32, 95% CI = 0.20-0.52)、有喝牛奶及豆奶習慣者有較低的攝護腺癌危險性(OR=0.38, 95% CI = 0.24-0.58 及OR=0.51, 95% CI = 0.31-0.85)；而有食用速食麵習慣者會有2.47倍攝護腺癌危險性(95% CI = 1.24-4.94)；我們也發現許多飲食因子與攝護腺癌有關: 在20-40歲期間每天食用綠色蔬菜與新鮮水果一次以上相較食用頻率少於一次者, 有較低的低攝護腺癌危險性(OR = 0.18, 95% CI = 0.08-0.36; OR=0.37, 95% CI=0.23-0.59, respectively)。而每週食用一次以上保存肉類食品, 相較於每月食用一次以下: 會升高3.81倍危險性(95% CI=1.54-9.42), 煙燻食品會有3.08倍危險性(95% CI = 1.08 – 8.75), 豆類發酵製品會有11.07倍危險性(95% CI = 5.24 – 23.39), 鹽漬食品會有5.68倍危險性 (95% CI=2.58 – 12.52)。本研究發現某些生活型態與飲食因子可能和攝護腺癌的危險性有關，大型的研究來確認與進一步探討其生物學上的機轉是需要的。在本研究的第二、第三及第四部分, 我們探討基因多型性對國人攝護腺癌危險性之作用。首先, 由於雄性素(androgen)在正常與癌化的攝護腺細胞的生長扮演主要的角色, 在雄性素受體基因(AR gene)上的CAG重複序列長度(CAG repeat length)被認為和雄性素受體的活性成相反的關係。雄性素受體活性的升高可能和攝護腺癌危險性有關, 而且雄性素受體基因的CAG重複序列長度的變異可能與攝護腺癌種族間的差異性有關。故在本研究的第二部分我們探討雄性素受體基因多型性對台灣攝護腺癌危險性的可能角色。　共有66位攝護腺癌個案與104位對照組作比較研究。雄性素受體基因CAG重複序列多型性是以聚合酶鏈鎖反應及直接定序(PCR-based direct sequencing)的方法測定。以邏輯式回歸方法分析雄性素受體基因CAG重複序列數目對攝護腺癌之危險性, 雄性素受體基因CAG重複序列數目與疾病分期, 病理分級的相關性也加以研究, 我們先將雄性素受體基因CAG重複序列數目當作連續變項加以分析, 再將區分為較短的組別與較長的組別作類別變項分析(n < 23 vs n ?d23)。我們也對雄性素受體基因CAG重複序列數目的極端值分佈分組加以分析這些相關性( n ?T 20 vs n ?d 26 and n = 21-25 vs n ?d 26)。我們的結果顯示: 雄性素受體基因CAG重複序列數目在個案組(23.2 ?b3.0, range 15-31)與對照組(22.9?b3.1, range 15-31)的平均值與分佈範圍是相似的。雄性素受體基因CAG重複序列在不同疾病分期(disease stage: P = 0.30), 病理分級(histological grade: P = 0.49)或發病年齡(age at diagnosis: P = 0.51)並無差異。在調整其他共變數如年齡, body mass index, 教育程度, 抽煙, 喝酒習慣後, 雄性素受體基因CAG重複數目並不會顯著影響攝護腺癌的危險性(OR=0.97, 95% CI = 0.72-1.31, P=0.84)。在以類別變項分析方面: 具有較短的AR CAG repeats (n<23)與較長的AR CAG repeat (n ?d23)相比, 並不會增加攝護腺癌的危險性(OR=0.45, 95% CI=0.29-1.05)。再以AR-CAG 極端短的組別(extreme short group: n ?T 20)與中間長短的組別(intermediate group: n = 21-25)與極端長的組別(n ?d 26)比較, 結果仍然是不顯著的 (n ?T 20 vs n>26: OR=1.00, 95% CI=0.34-3.00; n=21-25 vs n ?d 26: OR=0.82, 95% CI=0.37-1.81)。本部分研究的結果並不支持雄性素受體基因CAG重複序列基因多型性(AR-CAG repeat polymorphism)在攝護腺癌的危險性有重要的角色。更大型的研究以闡明基因變異在台灣地區攝護腺癌危險性的影響是必須的。維他命D缺乏(Vitamin D deficiency)已被假設為攝護腺癌的一個危險因子。在in vitro的研究發現維他命D及其類似物(analogue)對人類攝護腺癌細胞具有抑制生長與促進分化的作用。維他命D抗腫瘤的作用主要是經由維他命D受體(vitamin D receptor, VDR)所媒介。近來許多分子流行病學研究顯示在維他命D受體基因(VDR gene)的基因多型性可能和攝護腺癌的危險性及病理分級有關。然而, 這種發現仍完是未一致的。在本研究的第三部分, 我們探討在台灣族群維他命D受體基因上的BsmI, ApaI, TaqI基因多型性與攝護腺癌危險性的相關性。在200年12月至2003年2月, 共收集了160位攝護腺癌個案與205位年齡配對的對照組, 以PCR-RFLP的分法分析維他命D受體基因型。本研究結果顯示ApaI, TaqI 基因多型性與攝護腺癌危險無相關。然而, 在對照組中, 其BsmI “BB” 或 “Bb”基因型(15.6%)的頻率顯著高於個案組(8.1%)。在校正年齡之後, 個案帶有BsmI “BB”或”Bb”基因型者, 相較於但有”bb”基因型者, 有較小(兩倍低)的攝護腺癌危險性(OR = 0.50, 95% CI=0.25-0.98, P=0.045)。這個降低攝護腺癌危險性的作用在年齡低於中位數72歲的個案顯的更為顯著(P=0.017)。另外, 這相關性在較高的疾病分期(T3/T4/N1/M1)與病理分級分化不好者(Gleason score ?d 7)更明顯 (“BB” and “Bb” vs “bb”: OR=0.25； 95% CI=0.07-0.83；P=0.024 and OR=0.25, 95% CI= 0.07-0.85; P=0.026, respectively)。這部分我們的研究結果顯示維他命D受體BsmI基因多型性可能在攝護腺癌的發生扮演一重要的角色。腫瘤抑制基因(Tumor suppressor gene) p53與其下游的作用子p21被認為在人類癌症的發生扮演主要的角色。在p53 基因codon 72及p21基因codon 31的基因多型性變異被發現和癌症的易感性有關, 但少有研究探討他們在攝護腺癌危險性的作用。在本研究第四部分我們探討p53 codon 72及p21 codon 31 基因多型性與攝護腺癌危險性的相關。總共有200位攝護腺癌個案, 181位有症狀的攝護腺肥大(benign prostatic hyperplasia, BPH)病人 (AUA symptom score ?d 8分, 攝護腺體積大於20克) 及247位年齡配對健康男性對照組被研究。整體而言, 我們發現p53 基因多型性與攝護腺癌無顯著相關性。然而, 對於p21 基因多型性, p21 Ser/Ser, Ser/Arg 及Arg/Arg的基因分佈頻率在個案組為52 (26.0%), 85 (42.5%), 63 (31.5%), 在攝護腺肥大為48 (26.5%), 82 (45.3%), 51 (28.2%); 在對照組為76 (30.8%), 119 (48.2%), 52 (21.2%)。在個案與對照組比較, 帶有Arg/Arg 基因型較帶有Ser/Ser 基因型者, 在校正其他的共變量(covariates)後, 有1.78倍高的發生攝護腺癌危險性( 95% confidence interval (CI) = 1.06-3.01)。這顯著的相關性在較年輕的個案(?T72 years)更為顯著: odds ratio (OR) = 2.13, 95% CI = 1.16-3.92, 個案有99位, 對照組有126位; 而且我們也發現p21 coden 31基因多型性也與侷限性攝護腺癌(OR= 1.96, 95% CI = 1.15-3.35) 中度分化的攝護腺癌(OR=2.04, 95% CI =1.17-3.53)有關。另外, p21其帶Arg/Arg 基因型者與帶Ser/Ser 基因型這相比, 有較高的危險性發生較大攝護腺體積(>50 ml)的攝護腺肥大: OR=2.29, 95% CI=1.07-4.98。我們的研究發現顯示p21 codon 31基因多型性可能和攝護腺肥大與攝護腺癌的發生有關。關鍵字: 攝護腺癌,攝護腺肥大, 危險因子, 基因多型性, 雄性素受體, 維他命D受體, p53, p21, 台灣

關鍵字

p21 ； p53 ；維他命D受體；雄性素受體；攝護腺癌；攝護腺肥大；危險因子；台灣；基因多型性

並列摘要

The incidence of prostate cancer in Taiwan has been rapidly increasing in the past years. It became the 8th most common cause of cancer deaths and resulted in 750 deaths in 2,002. Because of lack of molecular epidemiologic studies in Taiwan, more efforts should be directed to identify its risk factors and to investigate the effects of genetic components (e.g. genetic susceptibility) on prostate cancer risks. Definite risk factors for prostate cancer were age, race and family history. Since the incidence different between Afican American, Caucasian and Aisan populations, the genetic alteration, environment and lifestyle factors between different population may also play an important part. However, rare study reported about the risk factors of prostate cancer in Taiwan. Literature review showed only one study with limited case number (case = 90, control = 180) about risk factors in northern Taiwan. So, in the first part of our study, we conduct a hospital-based case-control study to further investigate the risk factors of prostate cancer in southern Taiwan. In total, 195 prostate cancer patients and 291 age-matched male controls were recruited from Kaohsiung Medical University Hospital (KMUH) and Kaohsiung Veterans General Hospital (KVGH) between December 2000 and September 2003, we also recruited 173 benign prostatic hyperplasia (BPH) patients for further comparison. In-person interview with a structure questionnaire to access the social-demographic characteristics, environmental, lifestyle and selected foods factors… etc. Logistic regression was used to determine the relative risk of specific risk factors on prostate cancer risk. The significant risk factors and protective factors for prostate cancer in our study were as follows: those with regular exercise had lower risk for prostate cancer (OR=0.32, 95% CI = 0.20-0.52), the milk and soybean milk intake could reduce risk for developing prostate cancer (OR=0.38, 95% CI = 0.24-0.58 and OR=0.51, 95% CI =0.31-0.85, respectively) and those who consumed instant noodle had increased risk of prostate cacner (OR = 2.47, 95% CI = 1.24-4.94)。In addition, we found several dietary factors between 20 to 40 years were associated with prostate cancer risk. Compared to men with lower intakes, men who ate green vegetables ?d 1 time per day and fresh fruit ≥ 1 times per day had 0.18 (95% CI = 0.08-0.36) and 0.37 (95% CI= 0.23 -0.59) -fold risks, respectively, of developing prostate cancer compaered to less than one time per day. Men who ate preserved meat, smoked food, fermented bean products and salted food ?d 1 time per week had 3.81 (95% CI = 1.54-9.42), 3.08 (95% CI = 1.08-8.75), 11.07 (95% CI = 5.24-23.39) and 5.68 (95% CI = 2.58-12.32)-fold increased risks, respectively, for developing prostate cancer compared to men with lower intake frequencies (< one time/month) . From the preliminary results, we concluded that some lifestyle and dietary factors may associated the prostate cancer risk in Taiwan, further large-scale studies to confirm these risk factor and clearify the biological mechanisms were necessary. In the second , third and fourth parts of our study, we investigate the effect of genetic polymorphisms, including androgen receptor gene receptor, vitamin D receptor, p53 codon 72 and p21 codon 31 polymorphisms on prostate cancer risk in Taiwan. Androgen plays a major role in the development of both normal and malignant prostate cell through modulation the androgen receptor (AR). The length of polymorphic CAG trinucleotide repeats in the polyglutamine region of the androgen receptor gene (AR) has been suggested to be inversely correlated with the transactivation function of the androgen receptor (AR). An increase in androgen activity may be associated with prostate cancer, and ethnic variations in CAG repeat length may explain part of prostate cancer risks in different populations. In the second part of this study, we investigated the potential role of AR polymorphism in prostate cancer risk in Taiwanese. Sixty-six pathologically-confirmed prostate cancer patients and 104 controls were studied. CAG repeat polymorphism was genotyped by a PCR-based direct sequencing method. Logistic regression was used to determine the relative risk of AR gene CAG number on prostate cancer risk. The associations of AR-CAG polymorphism with disease stage, pathologic grade and age at diagnosed were assessed. AR-CAG repeat number was first treated as continuous variable, then was divided into short and long groups (n<23 vs. n≧23) for categorical analysis. The extreme groups of AR-CAG distribution were also analyzed for these associations (n≦20 vs. n≧26 and n=21-25 vs. n≧26). Our results showed the mean number of CAG repeats in patients and controls was similar: 23.2 ±3.0 (range=15-31) and 22.9 ±3.1 (range=15-31), respectively. No association was found between AR-CAG repeat polymorphism and disease stage (p = 0.30), histological grade (p = 0.49) or age at diagnosis (p = 0.51). After adjusting for other covariates (age, body mass index (BMI), education level, smoking and alcohol status), the number of AR-CAG repeats was not significantly associated with prostate cancer risk (OR= 0.97, 95% confidence interval (95% CI) = 0.72 to 1.31, p = 0.84). In categorical analysis, men with short CAG repeats (n <23) did not have increased risk for prostate cancer (OR=0.45, 95% CI = 0.29-1.05) compared with those with long CAG repeats (n≧23). Non-significant differences on prostate cancer risk were also found while comparing the extreme short group (n≦20) and the intermediate group (n=21-25) to the extreme long group (n≧26) (n≦20 vs. n≧26: OR=1.00, 95% CI = 0.34-3.00; n=21-25 vs. n≧26: OR=0.82, 95%CI = 0.37-1.81). Our results in this part do not support an important effect of AR-CAG repeat polymorphism on prostate cancer risk. We proposed a large-scale study is needed to clarify genetic components of prostate cancer risk in the Taiwanese population. Vitamin D deficiency has been hypothesized as one risk factor for prostate cancer. In vitro studies have revealed that vitamin D and vitamin D analogues have antiproliferative and differentiation effects on human prostate cancer cells. The antineoplastic actions of vitamin D appear to be mediated primarily through the vitamin D receptor (VDR). Recent molecular epidemiological studies have shown that the inherited polymorphisms of VDR gene may be linked to prostate cancer risk and its aggressive phenotypes. However, the findings remain inconclusive. In the third part of this study, we investigated the association of the BsmI, ApaI and TaqI polymorphisms of VDR gene with prostate cancer risk in a Taiwanese population. In total, 160 prostate cancer patients and 205 age-matched male controls were studied between December, 2000 and February, 2003. No significant associations were found between the ApaI and TaqI polymorphisms and the risk of prostate cancer. However, the control group was found to have a significantly higher frequency of the BsmI “BB” and “Bb” genotypes (15.6%) than prostate cancer patients (8.1%). After adjustment for age, patients with BsmI “BB” or “Bb” genotypes were associated with a two-fold decreased risk (OR = 0.50; 95% CI = 0.25-0.98; P = 0.045) for developing prostate cancer than those with “bb” genotypes. This effect was particularly significant among men below the median age of 72 years (P = 0.017). Moreover, stronger associations were found in the advanced stages (T3/T4/N1/M1) and poorly differentiated disease (Gleason Score ?d 7) (“BB” and “Bb” vs. “bb”: OR = 0.25; 95%CI = 0.07-0.83; P = 0.024 and OR = 0.25; 95% CI = 0.07-0.85; P = 0.026, respectively). Our findings suggest that the VDR BsmI polymorphism may play a significant role in the development of prostate cancer. The tumor suppressor gene p53 and its downstream effector of p21 are thought to play major roles in the development of human malignancy. Polymorphic variants of p53 at codon 72 and p21 at codon 31 have been found to be associated with cancer susceptibility, but rare studies have investigated their effect on prostate cancer risk. In the fourth part of this study, we investigated the association of p53 codon 72 and p21 codon 31 polymorphisms with prostate cancer risk in a Taiwanese population. In total, 200 prostate cancer patients, 247 age-matched male controls and 181 non age-matched symptomatic benign prostatic hyperplasia (BPH) (AUA symptom score ?d 8 and prostate volume >20gm) recruited from two medical centers in southern Taiwan were genotyped. Overall, we found no significant association between p53 polymorphism and risk of prostate cancer. However, for p21 polymorphism, the frequencies of p21 Ser/Ser, Ser/Arg and Arg/Arg were 52 (26.0%), 85 (42.5%), 63 (31.5%) in case patients, 48 (26.5%), 82 (45.3%), 51(28.2%) in BPH patients, and 76 (30.8%), 119 (48.2%), 52 (21.1%) in controls, respectively. Among the prostate cancer cases and controls, subjects with Arg/Arg genotype were found to have a 1.78-fold increased risk [95% confidence interval (CI) =1.06-3.01] of developing prostate cancer compared with those having the Ser/Ser genotype, after adjusting for other potential covariates. This significant association was slightly stronger [odds ratio (OR) = 2.13; 95% CI =1.16–3.92] in younger men (?T 72 years) (n = 99 and 126 for cases and controls, respectively) and correlated with localized disease stage (OR = 1.96, 95 % CI = 1.15-3.35) and moderately differentiated prostate cancer (OR = 2.04, 95% CI = 1.17-3.53). In addition, the Arg/Arg genotype was associated with BPH risk in those with large prostate volumes (>50 ml) compared with those having the Ser/Ser genotype [OR = 2.29, 95% CI =1.07-4.98]. Our findings suggest that the p21 codon 31 polymorphism may be associated with the development of prostate enlargement and cancer. Keywords: prostate cancer, benign prostatic hyperplasia (BPH), risk factors, genetic polymorphism, androgen receptor gene, vitamin D receptor, p53, p21, Taiwan

並列關鍵字

Taiwan ； p21 ； androgen receptor gene ； risk factors ； vitamin D receptor ； genetic polymorphism ； prostate cancer ； benign prostatic hyperplasia (BPH) ； p53