Transcription profiling of mouse whole skin from pRB deficient animals reveals that p107 acts as a tumor suppressor

The specific deletion of Rb gene in epidermis leads to altered proliferation and differentiation, but not to the development of spontaneous tumors. Our previous data have demonstrated the existence of a functional compensation of Rb loss by Rbl1 (p107) in as the phenotypic differences with respect to controls are intensified. However, the possible evolution of this aggravated phenotype, in particular in relationship with tumorigenesis, has not been evaluated due to the premature death of the double deficient mice. We have now investigated whether p107 can also act as a tumor suppressor in pRb-deficient epidermis using different experimental approaches. We found spontaneous tumor development in doubly-deficient skin grafts. Moreover, Rb-deficient keratinocytes are susceptible to Ha-ras-induced transformation, and this susceptibility is enhanced by p107 loss. Further functional analyses, including microarray gene expression profiling, indicated that the loss of p107, in the absence of pRb, produces the reduction of p53-dependent pro-apoptotic signals. Overall, our data demonstrate that p107 behaves as a tumor suppressor in epidermis in the absence of pRb and suggest novel tumor-suppressive roles for p107 in the context of functional p53 and activated Ras Experiment Overall Design: Pools from RNA whole skin extracts from 3 animals of same genotype were done and analyzed, per duplicate, in mouse microarrays. Comparison was performed between the 4 different genotypes.表皮特异性敲除Rb基因可导致细胞增殖与分化异常，但不会引发自发性肿瘤。我们既往的研究数据表明，当与对照组的表型差异加剧时，Rbl1（p107）可通过功能代偿弥补Rb的缺失。然而，由于双基因缺陷小鼠过早死亡，这种加重表型的潜在演化过程——尤其是其与肿瘤发生的关联——尚未得到评估。 本研究通过多种实验手段，探究了在pRb缺陷的表皮中，p107是否同样可作为肿瘤抑制因子发挥作用。我们在双基因缺陷的皮肤移植样本中观察到了自发性肿瘤的发生。此外，Rb缺陷的角质形成细胞易受Ha-ras诱导的恶性转化，而p107的缺失会进一步增强这种转化易感性。进一步的功能分析包括微阵列（microarray）基因表达谱分析，结果显示，在pRb缺失的背景下，p107的缺失会降低p53依赖的促凋亡信号通路活性。 综上，我们的研究证实，在pRb缺失的表皮组织中，p107可作为肿瘤抑制因子，并提示在功能完整的p53与激活型Ras的语境下，p107还具有全新的肿瘤抑制功能。 实验整体设计：将相同基因型的3只小鼠的全皮肤RNA提取物混合制备样本，每份样本设置双重复，进行小鼠微阵列（mouse microarrays）基因表达检测，并对4种不同基因型的样本开展比较分析。