Human breast
cancers include cancer stem cell populations as well as non-tumorigenic
cancer cells.
Breast cancer stem cells possess self-renewal capability and thus are the root cause of recurrence and
metastasis of malignant
tumors.
Hypoxia is a fundamental pathological feature of solid
tumor tissues and exerts a wide range of effects on the
biological behavior of
cancer cells. However, there is little information on the role of
hypoxia in modulating the stemness of
breast cancer cells. In the present study, we cultured MDA-MB-231 cells in a
hypoxic gas mixture to simulate the hypoxic environment in tissues and to determine how
hypoxia conditions could affect the cell proliferation, apoptosis, cytotoxicity, and colony-forming ability. Expression of the stem cell phenotype CD24(-)CD44(+)ESA(+) was analyzed to assess the effects of
hypoxia on stemness transformation in MDA-MB-231 cells. Our results found that the cell toxicity of MDA-MB-231 cells was not affected by
hypoxia.
Hypoxia could slightly inhibit the growth of MDA-MB-231 cells, but the inhibitory effect is not significant when compared with normoxic control. Moreover,
hypoxia significantly blocked the apoptosis in MDA-MB-231 cells (P < 0.05). The proportion of CD24(-)CD44(+)ESA(+) cells in MDA-MB-231 cells was increased greatly after they were treated with
hypoxia, and cell colony-formation rate of MDA-MB-231 cells also increased significantly in
hypoxia-treated cells. These results encourage the exploration of
hypoxia as a mechanism which might not be underestimated in chemo-resistant
breast cancer treatment.