Department of Carcinogenesis, Science Park-Research Division, The University of Texas M.D. Anderson Cancer Center, Smithville, TX, USA.
J Natl Cancer Inst. 2010 Nov 3;102(21):1663-75. doi: 10.1093/jnci/djq392. Epub 2010 Oct 21.
The incidence of nonmelanoma skin cancer (NMSC) is equivalent to that of all other cancers combined. Previously, we mapped the 12-O-tetradecanoylphorbol-13-acetate (TPA) skin tumor promotion susceptibility locus, Psl1, to distal chromosome 9 in crosses of sensitive DBA/2 mice with relatively resistant C57BL/6 mice. Here, we used the mouse two-stage skin carcinogenesis model to identify the gene(s) responsible for the effects of Psl1.
Interval-specific congenic mouse strains (n ≥ 59 mice per strain) were used to more precisely map the Psl1 locus. Having identified glutathione S-transferase α4 (Gsta4) as a candidate tumor promotion susceptibility gene that mapped within the delimited region, we analyzed Gsta4-deficient mice (n = 62) for susceptibility to skin tumor promotion by TPA. We used quantitative polymerase chain reaction, western blotting, and immunohistochemistry to verify induction of Gsta4 in mouse epidermis following TPA treatment and biochemical assays to associate Gsta4 activity with tumor promotion susceptibility. In addition, single-nucleotide polymorphisms (SNPs) in GSTA4 were analyzed in a case-control study of 414 NMSC patients and 450 control subjects to examine their association with human NMSC. Statistical analyses of tumor studies in mice were one-sided, whereas all other statistical analyses were two-sided.
Analyses of congenic mice indicated that at least two loci, Psl1.1 and Psl1.2, map to distal chromosome 9 and confer susceptibility to skin tumor promotion by TPA. Gsta4 maps to Psl1.2 and was highly induced (mRNA and protein) in the epidermis of resistant C57BL/6 mice compared with that of sensitive DBA/2 mice following treatment with TPA. Gsta4 activity levels were also higher in the epidermis of C57BL/6 mice following treatment with TPA. Gsta4-deficient mice (C57BL/6.Gsta4(-/-) mice) were more sensitive to TPA skin tumor promotion (0.8 tumors per mouse vs 0.4 tumors per mouse in wild-type controls; difference = 0.4 tumors per mouse; 95% confidence interval = 0.1 to 0.7, P = .007). Furthermore, inheritance of polymorphisms in GSTA4 was associated with risk of human NMSC. Three SNPs were found to be independent predictors of NMSC risk. Two of these were associated with increased risk of NMSC (odds ratios [ORs] = 1.60 to 3.42), while the third was associated with decreased risk of NMSC (OR = 0.63). In addition, a fourth SNP was associated with decreased risk of basal cell carcinoma only (OR = 0.44).
Gsta4/GSTA4 is a novel susceptibility gene for NMSC that affects risk in both mice and humans.
非黑素瘤皮肤癌（NMSC）的发病率与所有其他癌症的发病率相当。先前，我们将 12-O-十四烷酰佛波醇-13-乙酸（TPA）皮肤肿瘤促进易感性位点 Psl1 映射到敏感 DBA/2 小鼠与相对抗性 C57BL/6 小鼠杂交的远端 9 号染色体上。在这里，我们使用小鼠两阶段皮肤致癌模型来鉴定负责 Psl1 作用的基因（s）。
区间特异性同源小鼠品系（每个品系≥59 只小鼠）用于更精确地映射 Psl1 基因座。确定谷胱甘肽 S-转移酶α4（Gsta4）为映射到限定区域内的候选肿瘤促进易感性基因，我们分析了 Gsta4 缺陷型小鼠（n = 62）对 TPA 皮肤肿瘤促进的易感性。我们使用定量聚合酶链反应、western blot 和免疫组织化学来验证 TPA 处理后 Gsta4 在小鼠表皮中的诱导，并进行生化测定将 Gsta4 活性与肿瘤促进易感性相关联。此外，在 414 例 NMSC 患者和 450 例对照的病例对照研究中分析了 GSTA4 的单核苷酸多态性（SNP），以检查它们与人类 NMSC 的关联。对小鼠肿瘤研究的统计分析是单侧的，而所有其他统计分析都是双侧的。
同源小鼠的分析表明，至少有两个基因座 Psl1.1 和 Psl1.2 映射到远端 9 号染色体，并赋予 TPA 皮肤肿瘤促进易感性。Gsta4 映射到 Psl1.2，与敏感 DBA/2 小鼠相比，在 TPA 处理后，抗性 C57BL/6 小鼠的表皮中高度诱导（mRNA 和蛋白）。TPA 处理后，C57BL/6 小鼠表皮中的 Gsta4 活性水平也较高。Gsta4 缺陷型小鼠（C57BL/6.Gsta4（-/-）小鼠）对 TPA 皮肤肿瘤促进更为敏感（每只小鼠 0.8 个肿瘤与野生型对照中的每只小鼠 0.4 个肿瘤相比；差异 = 0.4 个肿瘤/只；95%置信区间=0.1 至 0.7，P = 0.007）。此外，GSTA4 遗传多态性与人类 NMSC 的风险相关。发现三个 SNP 是 NMSC 风险的独立预测因子。其中两个与 NMSC 风险增加相关（比值比[OR] = 1.60 至 3.42），而第三个与 NMSC 风险降低相关（OR = 0.63）。此外，第四个 SNP 仅与基底细胞癌风险降低相关（OR = 0.44）。
Gsta4/GSTA4 是一种新的 NMSC 易感性基因，可影响小鼠和人类的风险。
