Figure 4 Isolation of putative progenitor cells from primary cultures and cell lines. A. Breast primary cultures
were sorted into CALLA single-positive, EPCAM single-positive, double-positive (DP) or double-negative (DN) populations, and expressed as a percentage of total cells. B. TEM analysis revealed a high content of lipofuscin bodies in the DN population sorted from a tumour culture (arrows). C. The DN:DP ratio increased in three types of aggressive tumour (high grade, ER-negative or HER2-positive) relative to non-tumour or non-aggressive PI3K Inhibitor Library price tumour cultures. D. The DN:DP ratio in metastatic MDA-MB-231 cells exceeded that in non-tumourogenic MCF-10A cells. E. Activity of the stem cell marker ALDH was
similar in non-tumour versus pooled tumour cultures (left), but significantly higher in non-tumour and low grade tumour cultures compared to high grade tumour cultures (p < 0.001; right). Given DN differences in aggressive HG or ER-negative tumours versus aggressive HER2-positive tumours, we performed ultrastructural analysis on DN populations from one non-tumour and one tumour culture (grade 2 IDC, ER+, HER2+). Although both populations had many similarities (data not shown), unique to the tumour DN population was the presence of abundant lipofuscin bodies (Figure 4B, arrows). These markers of cellular ageing were also observed in unsorted normal and pre-invasive tumour cultures (data not 4EGI-1 datasheet shown). Since both DN and DP populations are putative progenitor/stem cells [3, 4], we questioned whether population ratios better reflected tumour progression than changes in single populations (Figure 4C). Increased DN:DP ratios were observed in all aggressive Gemcitabine chemical structure tumour cultures (HG, ER- or HER2+) relative to non-tumour or non-aggressive tumour cultures. A DN:DP increase was also noted in metastatic MDA-MB-231 cells versus normal
MCF-10A cells (Figure 4D). For these experiments, MDA-MB-231 and MCF-10A cells were switched from their normal media and conditioned to grow in MEGM (as used for primary cultures). Although this was not their preferred Ilomastat medium, the cells grew well and we did not observe any morphological differences as a result of media switching (Additional file 3). We also analyzed ALDH activity to estimate progenitor cell numbers. A low percentage of cells were ALDH-positive (Figure 4E, left). However ALDH activity in LG tumour cultures was significantly higher than that in non-tumour cultures (Figure 4E, right). Interestingly, ALDH activity dropped significantly from LG to HG cultures, to lower than that in non-tumour cultures (p < 0.001). This mirrored observed reductions in both DP and DN populations in HG versus LG tumour cultures (Figure 4A).