Furukawa Toru, Sunamura Makoto, Motoi Fuyuhiko, Matsuno Seiki, Horii Akira
Department of Molecular Pathology, Tohoku University School of Medicine, Sendai, Japan.
Am J Pathol. 2003 Jun;162(6):1807-15. doi: 10.1016/S0002-9440(10)64315-5.
We previously found frequent loss of heterozygosity at 12q21 and 12q22-q23.1 in primary pancreatic cancers, and the DUSP6/MKP-3 gene residing in this region at 12q22 lost its expression in the great majority of pancreatic cancer cell lines. The DUSP6/MKP-3 protein is a dual-specificity phosphatase that dephosphorylates the active form of ERK, making a feedback loop to control ERK activity. Gain-of-function mutations of KRAS2 occur in the great majority of pancreatic cancer cells, and loss of expression of DUSP6/MKP-3 may synergistically promote constitutive activation of ERK and uncontrolled cell growth. To study loss of the feedback pathway and its impact on pancreatic cancer cell growth, we first investigated the expression of DUSP6/MKP-3 in primary pancreatic cancer tissues immunohistochemically; we found up-regulation in mildly as well as severely dysplastic/in situ carcinoma cells and down-regulation in invasive carcinoma, especially in the poorly differentiated type. Adenovirus-mediated reintroduction of DUSP6/MKP-3 into cultured pancreatic cancer cells induced strong expression of recombinant DUSP6/MKP-3 and reduction of phosphorylated ERK in a dose-dependent manner based on the multiplicity of infection and resulted in suppression of cell growth. Moreover, analyses by flow cytometry and immunocytochemistry revealed that the exogenous expression of DUSP6/MKP-3 induced apoptosis. These results show that DUSP6 exerts apparent tumor-suppressive effects in vitro and suggest that DUSP6 is a strong candidate tumor suppressor gene at 12q22 locus.
我们之前发现，原发性胰腺癌中12q21以及12q22 - q23.1区域频繁出现杂合性缺失，位于12q22该区域的双特异性磷酸酶6（DUSP6）/丝裂原活化蛋白激酶磷酸酶 - 3（MKP - 3）基因在绝大多数胰腺癌细胞系中失去表达。DUSP6/MKP - 3蛋白是一种双特异性磷酸酶，可使细胞外信号调节激酶（ERK）的活性形式去磷酸化，从而形成一个反馈环来控制ERK活性。绝大多数胰腺癌细胞中发生KRAS2功能获得性突变，而DUSP6/MKP - 3表达缺失可能协同促进ERK的组成性激活及细胞的失控生长。为了研究该反馈通路的缺失及其对胰腺癌细胞生长的影响，我们首先通过免疫组织化学方法研究了原发性胰腺癌组织中DUSP6/MKP - 3的表达；我们发现，在轻度以及重度发育异常/原位癌细胞中DUSP6/MKP - 3表达上调，而在浸润性癌中表达下调，尤其是在低分化型癌中。腺病毒介导的DUSP6/MKP - 3重新导入培养的胰腺癌细胞，基于感染复数以剂量依赖的方式诱导重组DUSP6/MKP - 3的强烈表达以及磷酸化ERK的减少，并导致细胞生长受到抑制。此外，通过流式细胞术和免疫细胞化学分析表明，DUSP6/MKP - 3的外源性表达诱导细胞凋亡。这些结果表明，DUSP6在体外发挥明显的肿瘤抑制作用，并提示DUSP6是位于12q22位点的一个强有力的候选肿瘤抑制基因。
