Key Laboratory of Nutrition and Metabolisms, Institute of Nutritional Sciences, SIBS, Chinese Academy of Sciences, Shanghai, China.
Gastroenterology. 2010 Feb;138(2):606-15. doi: 10.1053/j.gastro.2009.09.049. Epub 2009 Sep 26.
BACKGROUND & AIMS: Prolyl hydroxylase (PHD) hydroxylates hypoxia inducible factor (HIF) alpha, leading to HIFalpha degradation. The PHD family comprises PHD1, PHD2, and PHD3. The enzymatic activity of PHDs is O(2)-dependent, so PHDs are believed to be oxygen sensors as well as tumor suppressors. However, the expression pattern of PHDs in colorectal cancer and the correlation between their expression level and tumorigenesis is unclear.
We determined the expression of PHDs in 60 human primary colorectal carcinoma tissues, paired with normal colorectal tissues. PHD3 expression levels were knocked down using small interfering RNA (siRNA); cells were analyzed by immunoblotting, immunoprecipitation, and histochemical analyses. In vivo tumor growth was analyzed in nu/nu mice.
Expression of PHD3 is decreased in colorectal cancer tissues. Decreased expression of PHD3 is associated with higher tumor grade and metastasis. PHD3 inhibits phosphorylation of inhibitor of kappaB (IkappaB) kinase (IKK) beta and activation of (NF) kappaB, independent of its hydroxylase activity. PHD3 associates with IKKbeta but does not target it for destruction; instead, PHD3 blocks the interaction between IKKbeta and Hsp90 that is required for phosphorylation of IKKbeta. Knockdown of PHD3 increased resistance of colorectal cancer cells to the effects of tumor necrosis factor-alpha and tumorigenesis.
PHD3 appears to be a tumor suppressor in colorectal cancer cells that inhibits IKKbeta/NF-kappaB signaling, independent of its hydroxylase activity. Activation of NF-kappaB has been observed in colon cancer. Determination of PHD3 status could aid targeted therapy selection for patients with colorectal tumors that have increased NF-kappaB activity.
脯氨酰羟化酶（PHD）羟化缺氧诱导因子（HIF）α，导致 HIFα 降解。PHD 家族包括 PHD1、PHD2 和 PHD3。PHD 的酶活性是 O(2)依赖性的，因此 PHD 被认为既是氧传感器，也是肿瘤抑制因子。然而，PHD 在结直肠癌中的表达模式及其表达水平与肿瘤发生的相关性尚不清楚。
我们测定了 60 例人原发性结直肠癌组织和配对正常结直肠组织中 PHDs 的表达。使用小干扰 RNA（siRNA）敲低 PHD3 表达；通过免疫印迹、免疫沉淀和组织化学分析进行细胞分析。在 nu/nu 小鼠中分析体内肿瘤生长。
PHD3 在结直肠癌组织中表达降低。PHD3 表达降低与肿瘤分级和转移较高有关。PHD3 独立于其羟化酶活性抑制 IκB 激酶（IKK）β的磷酸化和（NF）κB 的激活。PHD3 与 IKKβ 结合，但不将其靶向破坏；相反，PHD3 阻断 IKKβ与 Hsp90 之间的相互作用，这是 IKKβ磷酸化所必需的。PHD3 敲低增加了结直肠癌细胞对肿瘤坏死因子-α和肿瘤发生的耐药性。
PHD3 似乎是结直肠癌细胞中的肿瘤抑制因子，可抑制 IKKβ/NF-κB 信号通路，而不依赖其羟化酶活性。NF-κB 的激活已在结肠癌中观察到。确定 PHD3 状态可以帮助选择靶向治疗患有 NF-κB 活性增加的结直肠肿瘤的患者。
