目的　探讨人乳腺癌细胞系亚群的异质性及对癌细胞生物学行为的影响及其临床意义。方法　应用Percoll不连续密度梯度离心分离乳腺癌细胞系MCF 7亚群 ,以流式细胞仪测定人乳腺癌细胞系各亚群的DNA含量、细胞周期时相分布 ,以MTT法测定各亚群对抗癌药物敏感性的差异。结果　乳腺癌细胞系各亚群间在DNA含量、细胞周期时相分布方面存在异质性 ,该异质性可导致各亚群细胞增殖能力和对抗癌药物敏感性方面的差异。结论　肿瘤细胞自身遗传不稳定性可使肿瘤细胞在其演进过程中失去单克隆性 ,并发生亚克隆性生长 ,从而导致肿瘤细胞的异质性 ,包括DNA含量、细胞周期时相分布的差异 ,并且最终导致细胞增殖能力、对抗癌药物敏感性等生物学表型的改变 Objective To investigate the heterogeneity of human breast cancer cell line subpopulation and its effect on the biological behavior of cancer cells and its clinical significance. Methods Percoll discontinuous density gradient centrifugation was used to isolate the breast cancer cell line MCF 7. The DNA content and the cell cycle distribution of each subgroup were determined by flow cytometry. The subpopulations were determined by MTT assay Differences in anti-cancer drug sensitivity. Results There was heterogeneity in DNA content and cell cycle distribution in breast cancer cell lines. The heterogeneity resulted in the differences of proliferative ability and anticancer drug sensitivity of each subpopulation. CONCLUSION: The genetic instability of tumor cells can make tumor cells lose their monoclonality and subclone growth during their evolution, resulting in the heterogeneity of tumor cells, including the content of DNA, the phase distribution of cell cycle, And eventually lead to cell proliferation, changes in biological phenotypes such as anti-cancer drug sensitivity