1D). Although the amount of vimentin may vary throughout different HBCEC cultures, cytokeratin levels were always detected

at 95% or higher. Moreover, while the expression of intermediate filaments (Fig. 1C and 1D) was obtained from primary tumor cells after 34d, longer term culture remained stable displaying a similar pattern of intermediate filaments (data not shown). Together, these data suggested an almost exclusively epithelial-like cell population of HBCEC. To evaluate cell surface markers during Duvelisib long term culture of the breast tumors, an HBCEC population after 176 days was analyzed for CD24, CD44 and CD227, respectively, and compared to a tumor culture of the same patient after 462 days (Fig. 2A). Thus, CD24 was expressed in 89% of 176d HBCEC and in 86% of 462d HBCEC. Moreover, CD44 appearance was detectable in 94% of 176d HBCEC and in 99% of 462d HBCEC, suggesting little if any changes of both, CD24 and CD44 during long term tumor culture (Fig. 2A). In contrast, expression of the CD227 (MUC1) surface protein significantly CH5183284 chemical structure increased from 52% in 176d HBCEC to 88% in 462d HBCEC (Fig. 2A). Figure 2 Surface marker expression, SA-β-gal staining and telomerase activity in HBCEC. A. Determination of the percentage of cell surface marker expression in HBCEC at different ages. Expression of the surface marker proteins CD24, CD44, CD227 was maintained

during long term culture of HBCEC. Whereas CD24 and CD44 were similarly expressed after 176d and 462d, CD227 increased from 52% to 88% in HBCEC 462d. The flow cytometry measurements varied by about 8%. B. SA-β-gal staining of primary HBCEC and HMEC cultures. Staining for SA-β-gal of a HBCEC population after 722d in culture revealed little if any positive cell. Proteasome inhibitors in cancer therapy normal HMEC in passage 16, however, displayed already predominantly enlarged

senescent cells after 32d, demonstrated by the dark-green stain (bar = 200 μm). C. Telomerase (TRAP-)assay of crotamiton primary cultures from breast cancer biopsies. Telomerase activity was analyzed according to the Telomeric Repeat Amplification Protocol (TRAP). HBCEC populations demonstrated telomerase activity independent of the age of the culture and the harvest method. The human embryonic kidney (HEK) 293T cell line was used as a positive control and 1× CHAPS buffer served as a negative control. Quantification was performed using densitometric analysis. Further characterization of the HBCEC cultures was performed to determine aging cells in a senescence-associated β-galatosidase (SA-β-gal) assay as compared to normal post-selection human mammary epithelia cells (HMEC) (Fig. 2B). Thus, SA-β-gal staining of primary cultures from breast cancer biopsies after 722d demonstrated majorly small young cells and only occasional positively-stained senescent cells in contrast to normal post-selection HMEC (P16) after 32d with almost exclusively large SA-β-gal positive senescent cells (Fig. 2B).