Fishers exact test showed no statistical selleck screening library differences in tumor incidence between mice inoculated with 1 104 or 2 103 cells. No statistical analysis was performed on data of the tumor latency and volume in mice inoculated with 1 104 or 2 103 cells because of the insufficient number of samples. Hematoxylin and eosin staining was per formed to demonstrate that the xenografts in immuno deficient mice were generated from the injected human HeLa cells. We found that the tumor result from SP cell injection was poorer differentiation. SP cells exhibit increased resistance against TSA Hela, SP and non SP cells were treated with varying con centrations of TSA. Even at 0. 01 umol/L TSA, the viabil ity of SP cells was clearly higher than that of non SP cells.

As doses of TSA increased, the growth of HeLa and non SP cells was obviously suppressed. The suppressive effect reached the peak when cells were treated with 0. 2 umol/LTSA. The SF of sorted SP cells was significantly higher than that of non SP and unsorted HeLa cells. However, TSA had no significant sup pressive effect on the growth of SP cells. These results demonstrate the apparent chemoresistance of HeLa stem like cells against anticancer drugs, which may contribute to tumor recurrence and MDR. The SF of HeLa, SP and non SP cells was calculated as follows SF experiment OD/ control OD. Radiation sensitivity To examine whether the SP cells from the HeLa cell line possess a radioresistant phenotype, we exposed SP, non SP and HeLa cells to X rays to determine their sensitiv ity to radiation.

After irradiation, we cultured the cells for 7 days, and then subjected them to an MTS assay. All the cell types showed sensitivities to X ray irradiation, and their cell proliferation rates decreased with increasing doses of radiation. Exposure to X rays at 1, 2, or 4 Gy, the SFs of SP, non SP and HeLa cells were resulted in signifi cant differences. As shown in Figure Drug_discovery 7, SP cells grew faster than non SP cells when they were exposed to different does X ray. SP cells showed great radioresistance than the other cells. On the 7th day after irradiation, the SFs of SP, Discussion Since the stem cell theory of cancer was proposed, it was first confirmed in the field of hematology. Isola tion of CSCs from solid tumors is usually performed by cell sorting based on the expression of putative surface biomarkers of stem cells. Recent studies of stem cells have shown that a small population of cells can specifically ex trude the DNA dye Hoechst 33342. Such cells show weak fluorescence in flow cytometry, and have been named as SP cells. Further studies reported that SP cells are found in several cancer cell lines, and demonstrate certain stem cell like phenotypic characteristics.