A proteomic investigation into the human cervical cancer cell line HeLa treated with dicitratoytterbium (III) complex

Lanthanides have been reported to induce apoptosis in cancer cell lines. Human cervical cancer cell line HeLa was found to be more sensitive to dicitratolanthanum (III) complex (LaCit₂]³⁻) than other cancer cell lines. However, the effect and mechanism of dicitratoytterbium (III) complex (YbCit₂]³⁻) on HeLa cells is unknown. Using biochemical and comparative proteomic analyses, YbCit₂]³⁻ was found to inhibit HeLa cell growth and induce apoptosis. Similar to the effects of LaCit₂]³⁻, proteomics results from YbCit₂]³⁻-treated cells revealed profound changes in proteins relating to mitochondria and oxidative stress, suggesting that mitochondrial dysfunction plays a key role in YbCit₂]³⁻-induced apoptosis. This was confirmed by the decreased mitochondrial transmembrane potential and the increased generation of reactive oxygen species in YbCit₂]³⁻-treated cells. Western blot analysis showed that YbCit₂]³⁻-induced apoptosis was accompanied by the activation of caspase-9 and specific proteolytic cleavage of PARP, leading to an increase in the pro-apoptotic protein Bax and a decrease in the anti-apoptotic protein Bcl-2. These results suggest a mitochondrial pathway of cell apoptosis in YbCit₂]³⁻-treated cells, which will help us understand the molecular mechanisms of lanthanide-induced apoptosis in tumor cells.