Sevignani C, Wlodarski P, Kirillova J, Mercer W E, Danielson K G, Iozzo R V, Calabretta B
Department of Microbiology and Immunology, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
J Clin Invest. 1998 Apr 15;101(8):1572-80. doi: 10.1172/JCI919.
Distinct genetic abnormalities (loss-of-function mutations of APC and p53 and oncogenic activation of Ki-ras) are associated with specific stages of the sporadic, most common types of colorectal tumors. However, the inability to maintain primary colon epithelial cells in culture has hindered the analysis of the pathogenetic role of these abnormalities in colorectal tumorigenesis. We have now established primary cultures of epithelial cells from the colon crypts of p53-deficient mice; these cells are nontumorigenic as indicated by their failure to form colonies in soft agar and to grow as tumors in immunodeficient SCID mice and in immunocompetent syngeneic hosts. Upon ectopic expression of an activated Ki-ras gene, p53-deficient colon epithelial cells form colonies in soft agar and highly invasive subcutaneous tumors in both immunodeficient and immunocompetent mice. Ectopic expression of wild-type p53, but not of a DNA-binding-deficient mutant, markedly suppressed the colony-forming ability of the Ki-ras-transformed p53-deficient epithelial cells. Together, these findings establish a functional synergism in colorectal tumorigenesis dependent on the effects of an oncogenic Ki-ras in a p53-deficient background. This model of tumorigenic conversion of colon epithelial cells might be useful to identify genetic changes associated with disease progression and to evaluate the therapeutic response to conventional and novel anticancer drugs.
不同的基因异常（APC和p53的功能丧失突变以及Ki-ras的致癌激活）与散发性、最常见类型的结直肠肿瘤的特定阶段相关。然而，无法在培养中维持原代结肠上皮细胞阻碍了对这些异常在结直肠癌发生中的致病作用的分析。我们现在已经建立了来自p53缺陷小鼠结肠隐窝的上皮细胞原代培养物；这些细胞不具有致瘤性，这表现为它们在软琼脂中不能形成集落，并且在免疫缺陷的SCID小鼠和免疫健全的同基因宿主中不能作为肿瘤生长。在激活的Ki-ras基因异位表达后，p53缺陷的结肠上皮细胞在软琼脂中形成集落，并在免疫缺陷和免疫健全的小鼠中形成高度侵袭性的皮下肿瘤。野生型p53而非DNA结合缺陷突变体的异位表达显著抑制了Ki-ras转化的p53缺陷上皮细胞的集落形成能力。总之，这些发现确立了在结直肠癌发生中依赖于致癌性Ki-ras在p53缺陷背景下作用的功能协同作用。这种结肠上皮细胞致瘤转化模型可能有助于识别与疾病进展相关的基因变化，并评估对传统和新型抗癌药物的治疗反应。
