Figure 2: SWNTs can localize at telomeres and inhibit telomerase activity in living cancer cells.

(a) SWNTs localizes at telomere in K562 and HeLa cells evidenced by the co-localizations with telomere marker TRF1 protein. K562 and HeLa cells were incubated with SWNT-PEG-FITC (green) for 24 h and co-stained with anti-TRF1 antibody (red). White rectangles in merged pictures were enlarged as shown in right, yellow dots indicated the co-localization signals. Scale bar equals 10 μM. (b) Telomerase activity inhibition induced by carboxylated SWNTs in human K562 and HeLa cells. Cells were treated with increasing concentrations of carboxylated SWNTs for 6 days, CHAPS extract was prepared and equivalent amounts of protein (500 ng) were subjected to a standard TRAP assay. The position of the internal standard was indicated as IS. (c) Telomerase activity was quantitated as the percent of the corresponding control sample containing no CNTs. The mean of three independent experiments with comparable results was shown. Error bars indicate±s.d. (d) SWNT-COOH treatment does not induce the change of localization of hTERT in K562 cells. After treatment with SWNT-COOH for 1 week, K562 cells were stained with anti-hTERT antibody (red) and the nucleus were visualized with DAPI staining (blue), and the merged image is shown in right. Scale bar equals 20 μM. (e) SWNT-COOH doses not induce the change of expression of hTERT, hTEP1 and hTR at mRNA levels by using semi-quantitative RT–PCR assay. β₂-M was used as loading control. (f) SWNT-COOH doses not induce the alternation of expression of hTERT and hTEP1 at protein levels. After 1 week of treatment, the protein was extracted and subjected to western blotting, then probed with anti-hTERT and anti-hTEP1 antibodies. β-actin was used as loading control.