Résumé
Purpose To investigate the effect of protein tyrosine phosphatase receptor type D (PTPRD) on the characteristics of breast cancer stem cells. Method PTPRD expression in breast cancer cell line MDA-MB231 was down-regulated by small interference RNAs (siRNAs). Self-renewal ability of breast cancer stem cells (BCSCs) was detected by mammosphere formation assay. The holocolony forming ability was detected by colony formation assay. The proportion of CD44+/CD24- BCSCs was detected by flow cytometry. The ability of tumorigenesis of breast cancer cells in mice was sdudied with mouse tumorigenesis test. Separation of CD44+/CD24- stem cell population and non-stem cell population was isolated by immunomagnetic beads. Expression of PTPRD in stem cell and non-stem cell population was detected by Western blot and immunofluorescent. Results Down-regulation of PTPRD promoted the expression of stem cell markers ALDH1 and OCT-4. The expression of PTPRD in breast cancer stem cells was lower than than in non-stem cells (P<0.05). After PTPRD was down-regulated, the number of mammosphere (147±3.51) was significantly higher than that of the control group (106±12.5) (P<0.05), the proportion of holoclone [(35.9±3.4) ％] was significantly higher than that of the control group [(11.2±5.3) ％] (P<0.05), the proportion of CD44+/CD24- cells[(2.88±1.2) ％]was significantly higher than that of the control group [(0.6±0.4) ％], the in vivo tumorigenicity was significantly enhanced in nude mice (P<0.05). Conclusion The expression of PTPRD is lower in BCSCs. PTPRD may inhibit the self-renewal ability of breast cancer stem cells.
Résumé
This study was aimed to sort the side population (SP) cells from human multiple myeloma cell lines, then detect the biological characteristics of those SP cells. After Hoechst33342 staining, intracellular Hoechst33342 fluorescence staining differences of myeloma cell lines observed by the fluorescence microscopy. The fluorescence-activated cell sorting (FACS) technology was used to isolate SP cells and main population (MP) cells; proliferative capacity in vitro was determined by cell growth curve; the cell colony forming ability was compared by colony forming test. The CD138 expression was detected by flow cytometry. The expression of ABCG2 mRNA was detected by reverse transcription PCR; CCK-8 assay and colony forming test were used to evaluate the effect of bortezomib on the cell proliferation, vitality and colony forming ability of the two populations. The results showed that the myeloma cell lines had a small proportion of SP cells, especially, RPMI 8226 cells accounted for the highest proportion of SP cells (7.10 ± 2.69)%, which have also been confirmed under the fluorescence microscope; the proliferative activity and cell colony forming ability of SP cells were significantly higher than those of MP cells (P < 0.05). The expression levels of CD138 in SP and MP cells were not significantly different (P > 0.05). RT-PCR results showed that SP cells expressed the drug-resistance gene ABCG2, but MP cells hardly express these genes. The inhibition rate of bortezomib on SP cells was significantly lower than that on MP cells (P < 0.05), however, the difference was not significant (P > 0.05) at bortezomib 40 nmol/L. Bortezomib could reduce colony formation in the both two cell populations, but more severe reduction appeared in the MP cells. It is concluded that the myeloma cell line contain a small amount of SP cells with the cancer stem cell characteristics.