Gervaz P, Efron J, Poza A A, Chun S W, Pham T T, Woodhouse S, Wexner S D, Carethers J M
Department of Colorectal Surgery, Cleveland Clinic Florida, Weston, Florida 33331, USA.
Dis Colon Rectum. 2001 Oct;44(10):1503-8. doi: 10.1007/BF02234606.
This study was designed to determine whether loss of heterozygosity and/or microsatellite instability correlate with HIV infection and tumor recurrence after chemoradiation therapy in patients with squamous-cell carcinoma of the anus.
The molecular mechanisms leading to the progression of HIV-related squamous-cell carcinoma of the anus are poorly understood. In particular, genetic alterations responsible for resistance to chemoradiation have important clinical and functional implications.
In a case-control study, we analyzed normal and tumor DNA samples of four patients with squamous-cell carcinoma of the anus who were successfully treated with chemoradiotherapy and four patients with radio-resistant squamous-cell carcinoma of the anus who required abdominoperineal resection for local recurrence. To determine the presence of microsatellite instability, we used the reference panel of five pairs of microsatellite primers recommended for colorectal cancer specimens. These include the microsatellite markers BAT25, BAT26, D5S346 (APC), D2S123 (hMSH2), and D17S250 (P53). In addition, we used microsatellite markers for loss of heterozygosity analyses that were tightly linked to tumor suppressor genes. These included D3S1611 (hMLH1), D17S513 (P53), D18S46 and 18qTA (DCC/SMAD4), D5S107 (APC), and CA5 (hMSH2).
There were two HIV-positive and two HIV-negative patients in each group. Three HIV-positive patients (one in the chemoradiotherapy group and two in the nonchemoradiotherapy group) demonstrated loss of heterozygosity. In the chemoradiotherapy group, one HIV-positive patient demonstrated loss of heterozygosity at the hMLH1 locus. In the nonchemoradiotherapy group, two HIV-positive patients exhibited a total of four instances of loss of heterozygosity. One tumor had loss of heterozygosity at hMSH2 and DCC/SMAD4; another tumor demonstrated loss of heterozygosity at hMSH2 and APC. Microsatellite instability-low was found in two HIV-positive patients. No instances of loss of heterozygosity and microsatellite instability were detected in HIV-negative patients.
Loss of heterozygosity and microsatellite instability, which reflect inactivation of tumor-suppressor genes and genomic instability, occur with increased frequency in HIV-associated squamous-cell carcinoma. These data demonstrate for the first time evidence of loss of heterozygosity at the APC and DCC/SMAD4 gene loci in anal carcinoma. Although the findings presented here need to be expanded in a larger study, the recurrent loss of heterozygosity at D2S123, which was demonstrated in HIV-positive patients with radio-resistant squamous-cell carcinoma of the anus, is notable.
本研究旨在确定杂合性缺失和/或微卫星不稳定性是否与肛门鳞状细胞癌患者接受放化疗后的HIV感染及肿瘤复发相关。
导致HIV相关肛门鳞状细胞癌进展的分子机制尚不清楚。特别是，与放化疗耐药相关的基因改变具有重要的临床和功能意义。
在一项病例对照研究中，我们分析了4例成功接受放化疗的肛门鳞状细胞癌患者以及4例因局部复发需要行腹会阴联合切除术的放化疗耐药肛门鳞状细胞癌患者的正常和肿瘤DNA样本。为了确定微卫星不稳定性的存在，我们使用了推荐用于结直肠癌标本的5对微卫星引物的参考面板。这些包括微卫星标记BAT25、BAT26、D5S346（APC）、D2S123（hMSH2）和D17S250（P53）。此外，我们使用与肿瘤抑制基因紧密连锁的微卫星标记进行杂合性缺失分析。这些包括D3S1611（hMLH1）、D17S513（P53）、D18S46和18qTA（DCC/SMAD4）、D5S107（APC）和CA5（hMSH2）。
每组中有2例HIV阳性患者和2例HIV阴性患者。3例HIV阳性患者（放化疗组1例，非放化疗组2例）出现杂合性缺失。在放化疗组中，1例HIV阳性患者在hMLH1位点出现杂合性缺失。在非放化疗组中，2例HIV阳性患者共出现4次杂合性缺失。1例肿瘤在hMSH2和DCC/SMAD4位点出现杂合性缺失；另1例肿瘤在hMSH2和APC位点出现杂合性缺失。2例HIV阳性患者检测到微卫星不稳定性低。HIV阴性患者未检测到杂合性缺失和微卫星不稳定性的情况。
杂合性缺失和微卫星不稳定性反映了肿瘤抑制基因的失活和基因组不稳定性，在HIV相关的鳞状细胞癌中出现频率增加。这些数据首次证明了肛门癌中APC和DCC/SMAD4基因位点杂合性缺失的证据。尽管此处呈现的研究结果需要在更大规模的研究中进一步扩展，但在耐放化疗的HIV阳性肛门鳞状细胞癌患者中出现的D2S123位点杂合性缺失反复出现这一情况值得关注。
