Consequently, telomerase assays were performed and revealed telomerase activity of autonomously proliferating cells in all HBCEC populations (Fig. 2C). The human embryonic kidney (HEK) 293T cell line served as a positive control and the buffer was used as a negative control. Together, these findings suggested a sustained expression of epithelial stem cell-like markers in HBCEC paralleled by only occasional senescence and a marked telomerase activity. Individually-derived HBCEC populations from cultured breast cancer biopsies were tested for their response to distinct

chemotherapeutic compounds and combinations. Thus, HBCEC populations (39d) from tumor biopsies of a 40 year-old (Fig. 3A) and HBCEC populations Ralimetinib (34d) a 63 year-old patient (Fig. 3B) were treated with 125 nM and 1 μM of Taxol, Epothilone A, Epothilone B, Epirubicin, Doxorubicin, and the combinations of Epirubicin/Taxol, Epirubicin/Epothilone A, and

Epirubicin/Epothilone B, respectively. Similar treatments were performed with the non-metastatic breast cancer cell line MCF-7 (Fig. 4A), with the H 89 cost highly metastatic MDA-MB-231 cell line (Fig. 4B) and with normal post-selection HMEC of passage 16 (Fig. 5), respectively. Incubation with a single dose of 1 μM (blue bars) and 125 nM (red bars) of Taxol, epothilones or the anthracyclins and combinations for 6d were less effective as compared to a sequential incubation, PLX3397 mw whereby the same compounds with the same concentrations of 1 μM (yellow bars) and 125 nM (turquoise bars) were replaced after 3d, resulting in a similar 6d (= 2× 3d) incubation period, respectively. Moreover, the lower concentrated drugs (125 nM) were less effective than the 1 μM dose of these compounds, respectively. In contrast, Epothilone A and B displayed different effects in both HBCEC populations. Thus, a sequential dose of these two compounds significantly increased the cytotoxicity in one population

(Fig. 3B), whereas little if any effects were observed in HBCEC from a different breast cancer patient, respectively Oxymatrine (Fig. 3A). Similarly, Epothilone A and B exhibited different effects on the two breast carcinoma cell lines (Fig. 4A, B). Moreover, the non-metastatic MCF-7 cell line displayed an overall increased sensitivity to the administered drugs or drug combinations as compared to the highly metastatic MDA-MB-231 cells (Fig. 4A, B). Normal post-selection HMEC (P16) demonstrated reduced cytotoxic effects of the chemotherapeutics as compared to the HBCEC cultures (Fig. 5). These differences in response to certain anti-cancer drugs could be explained by the reduced or ceased proliferative capacity of senescent post-selection HMEC (P16) in contrast to the continuous proliferation of HBCEC. Figure 3 Chemotherapeutic effects on HBCEC from breast cancer patients. HBCEC derived from a 40 year-old (HBCEC 366) (Fig. 3A) and a 63 year-old (HBCEC 367) (Fig.