Morán Alberto, Iniesta Pilar, de Juan Carmen, García-Aranda Cristina, Díaz-López Antonio, Benito Manuel
Departamento de Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
Cancer Res. 2005 May 1;65(9):3811-4. doi: 10.1158/0008-5472.CAN-04-4442.
Colorectal tumorigenesis is characterized by the sequential inactivation of a series of tumor suppressor genes (microsatellite-stable tumors) and genetic or epigenetic alterations in mismatch repair genes in nonpoliposic hereditary tumours and 13% to 15% of sporadic colorectal cancer [high microsatellite instability (MSI-H) tumors]. We hypothesized a molecular mechanism for MSI-H colorectal tumors related to matrix metalloproteinase 3 (MMP-3) promoter mutations, down-regulation of MMP-3 expression, and impairment of MMP-9 activation. We have now analyzed the 2.2-kb full MMP-3 promoter to assess the mutation distribution. The mutations found are restricted to the polymorphic region that includes the zinc-binding protein (ZBP-89) binding element. To show that these alterations were the cause of the low expression of this gene, we have generated three constructs with different MMP-3 promoters (wild type and two mutants) and we have expressed them in SW480 human colorectal cells. The basal transcriptional activity of wild-type MMP-3 promoter was much higher than the mutants activity. In addition, 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced transcriptional activity of wild-type MMP-3 promoter was 10-fold higher than the mutants activity. Dexamethasone inhibited the basal transcriptional activity of wild-type MMP-3 promoter and of the two mutants found in the MSI-H subgroup of colorectal tumors. Significantly, dexamethasone almost completely blunted the TPA-induced effect on wild-type MMP-3 promoter transcriptional activity and on the mutants, even below their basal activity. Our data show that mutations found in the polymorphic region of the MMP-3 promoter from MSI-H colorectal tumors impair its basal and induced transcriptional activity, which may contribute to their better clinical outcome.
结直肠癌的发生具有一系列抑癌基因的相继失活（微卫星稳定肿瘤）以及非息肉性遗传性肿瘤和13%至15%的散发性结直肠癌[高微卫星不稳定性（MSI-H）肿瘤]中错配修复基因的遗传或表观遗传改变的特征。我们推测MSI-H结直肠癌肿瘤存在一种分子机制，与基质金属蛋白酶3（MMP-3）启动子突变、MMP-3表达下调以及MMP-9激活受损有关。我们现在分析了2.2 kb的完整MMP-3启动子，以评估突变分布。发现的突变仅限于包含锌结合蛋白（ZBP-89）结合元件的多态性区域。为了证明这些改变是该基因低表达的原因，我们构建了三种具有不同MMP-3启动子（野生型和两个突变体）的构建体，并在SW480人结肠癌细胞中进行表达。野生型MMP-3启动子的基础转录活性远高于突变体的活性。此外，12-O-十四酰佛波醇-13-乙酸酯（TPA）诱导的野生型MMP-3启动子的转录活性比突变体的活性高10倍。地塞米松抑制野生型MMP-3启动子以及在MSI-H结直肠癌肿瘤亚组中发现的两个突变体的基础转录活性。值得注意的是，地塞米松几乎完全消除了TPA对野生型MMP-3启动子转录活性和突变体的诱导作用，甚至使其低于基础活性。我们的数据表明，在MSI-H结直肠癌肿瘤的MMP-3启动子多态性区域发现的突变损害了其基础和诱导的转录活性，这可能有助于其更好的临床结果。
