ABSTRACT
BACKGROUND: Breast cancer stem cells, a subgroup of breast cancer cells, have self-renewal and multilineage differentiation potential and are characterized as resistance to chemotherapy, radiotherapy and hypoxia, and high propensity for invasiveness and metastasis, which play an important role in the recurrence and metastasis of breast cancer. The breast cancer stem cell theory can elucidate the pathogenesis of breast cancer to a certain extent, and has great values in the selection of treatment options, the discovery of new therapeutic targets and the prognosis of breast cancer.OBJECTIVE: To isolate the breast cancer stem/progenitor cells from basal-like breast carcinoma and study their self-renewal ability, phenotype and differentiation potential over long-term serum-free suspension culture in vitro. METHODS: Twenty patients with basal-like breast cancer, including 10 patients without any treatment and 10 with neoadjuvant chemotherapy (≥ 4 cycles), were enrolled. A 1 cm3 fresh tumor tissue sample from each patient was taken and immediately sent to the laboratory to mechanically isolate tumor cells. Then, the stem/progenitor cells of basal-like breast carcinoma were enriched in ultra low attachment plates in serum free media as nonadherent mammospheres. Serial sphere formation assay was performed to determine colony formation and self-renewal ability of mammosphere-derived cells. Differentiation was induced by culturing mammosphere-derived cells in DMEM-F12 supplemented with serum but without growth factors. The proportion of CD44+/CD24- and ALDH1+ cell population was evaluated by flow cytometry. RESULTS AND CONCLUSION: The mammospheres formed after inoculation of primary basal-like breast cancer cells isolated from the tumor tissues of breast cancer patients who did not receive neoadjuvant chemotherapy cultured in the serum-free medium with growth factors, while the mammospheres could be directly isolated from the tumor specimens of patients with neoadjuvant chemotherapy. The mammosphere-derived cells could be passaged continuously to form new mammospheres. With the increase of subculture frequency, the number of adherent cells was increased, but the number of new mammospheres decreased, and the spheres became smaller and easier to adhere. The mammosphere-derived cells could be induced to differentiate in the medium supplemented with serum. The CD44+/CD24- and ALDH1+ cells were enriched in mammosphere-derived cells, and these two phenotypic cells were decreased sharply in number or absent after cell differentiation. Most of the mammosphere-derived cells after chemotherapy had stronger potentials of self-renewal and differentiation, with higher proportion of CD44+/CD24- and ALDH1+ cells. In summary, cancer cells with self-renewal and multilineage differentiation potentials exist in the basal-like breast cancer tissues. Neoadjuvant chemotherapy can enrich breast cancer stem/progenitor cells to form spheroid-like cell clusters. Some differences in biological behaviors exist between the stem/progenitor cells from different breast cancer samples, which can vary with environmental factors.