Iwaya K, Tsuda H, Fujita S, Suzuki M, Hirohashi S
Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Lab Invest. 1995 Jun;72(6):707-14.
Nuclear accumulation of p53 protein in breast cancer cells is generally accepted as a marker for the presence of p53 gene mutation and as an indicator of poor prognosis. Mutation in the p53 gene has been shown to cause conformational change in the p53 protein, which gives rise to a complex with heat shock protein 70 (hsp70).
To clarify whether the p53 protein that accumulates in the nuclei of human cancer cells is bound to hsp70 in vivo, we compared the immunohistochemical localization of both p53 and hsp70 in 65 surgically resected cases of primary breast cancer. In four cases showing both nuclear accumulation of p53 protein and mutation of the p53 gene, identified by single-strand conformation polymorphism and direct sequence analysis, the presence of the p53-hsp70 complex was examined by coimmunoprecipitation assay. In 12 human cancer cell lines showing nuclear accumulation of the p53 protein, the presence of the p53-hsp70 complex was also examined by immunoprecipitation with two anti-p53 Ab after labeling with [35S]methionine.
Among the 65 cases, p53 and hsp70 immunoreaction in cancer cell nuclei was detected immunohistochemically in 16 (25%) and 23 (35%) cases, respectively. The localizations of the two proteins were significantly correlated, but there was a discrepancy in the localization patterns in 23 cases. Although the p53-hsp70 complex was detected in all of the four cases in which the p53 mutation was identified, the expression levels of hsp70 detected by coimmunoprecipitation assay were much weaker than those of p53 protein. In all of the 12 cancer cell lines with nuclear accumulation of p53, no distinct 70-kDa bands were immunoprecipitated with the p53 protein.
In human breast cancer tissue, only part of the pool of p53 is bound to hsp70.
乳腺癌细胞中p53蛋白的核内积聚通常被认为是p53基因突变存在的标志物以及预后不良的指标。已表明p53基因的突变会导致p53蛋白的构象变化，进而产生与热休克蛋白70（hsp70）的复合物。
为了阐明在人类癌细胞核中积聚的p53蛋白在体内是否与hsp70结合，我们比较了65例手术切除的原发性乳腺癌病例中p53和hsp70的免疫组化定位。在通过单链构象多态性和直接序列分析鉴定出的4例显示p53蛋白核内积聚且p53基因发生突变的病例中，通过共免疫沉淀试验检测p53-hsp70复合物的存在。在12个人类癌细胞系中，p53蛋白存在核内积聚，在用[35S]甲硫氨酸标记后，也通过用两种抗p53抗体进行免疫沉淀来检测p53-hsp70复合物的存在。
在65例病例中，分别通过免疫组化在16例（25%）和23例（35%）癌细胞核中检测到p53和hsp70免疫反应。两种蛋白的定位显著相关，但在23例病例中定位模式存在差异。虽然在所有4例鉴定出p53突变的病例中都检测到了p53-hsp70复合物，但通过共免疫沉淀试验检测到的hsp70表达水平比p53蛋白的表达水平弱得多。在所有12个p53核内积聚的癌细胞系中，用p53蛋白免疫沉淀未得到明显的70 kDa条带。
在人类乳腺癌组织中，只有一部分p53与hsp70结合。
