Interfacial chemistry: gold's enigmatic surface.


protection against cancer. In fact, when Nras-expressing senescent cells were not cleared (for example, in mice lacking CD4 T cells), numerous tumours appeared, whereas clearance of senescent cells robustly prevented tumour development. The authors also studied mouse models of liver inflammation and toxicity — known risk factors for liver cancer in humans. Again, in the absence of the adaptive immune system, cells that had undergone senescence following inflammation and liver toxicity were not cleared, and this was associated with increased tumorigenesis. Kang et al. further extrapolated their findings to human disease, by analysing the livers of patients infected with hepatitis C virus (HCV) whose immune systems were either intact or compromised owing to concomitant infection with HIV. In agreement with their mouse data, the authors found that senescent cells were cleared in patients infected with HCV alone but not in those infected with both HCV and HIV. Similarly, HCV-infected patients with cirrhosis who were being treated with immunosuppressants had senescent cells in their livers, but this was not the case in untreated patients. As the authors note, HIV infection and immunosuppressant therapy are associated with increased risk of liver cancer. It has been shown that clearance of senescent cells by the immune system is also important for the resolution of fibrotic scars in liver. Together with Kang and co-workers’ data, this suggests that the clearance of these cells could indeed prove generally beneficial for tissue repair, as previously proposed. This paper clearly shows that cell clearance is essential for the maximum tumoursuppressive effects of senescence. But this brings us to a conundrum: why do senescent cells, which cannot proliferate, pose a cancer risk? Two possible answers come to mind. First, it is conceivable that rare senescent cells exist at an intermediate — still un defined — state that has the potential to resume proliferation and initiate cancer. Second, the proliferative factors secreted by senescent cells for their tissue-repair function may be usurped by neighbouring cancerous cells to enhance their proliferation. Future work will undoubtedly resolve this issue and will continue to enrich the fascinating link between senescence and cancer. ■

DOI: 10.1038/479482a

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Cite this paper

@article{Madix2011InterfacialCG, title={Interfacial chemistry: gold's enigmatic surface.}, author={Robert J. Madix and Cynthia M Friend}, journal={Nature}, year={2011}, volume={479 7374}, pages={482-3} }