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A Better Outlook for Breast Cancer Patients

Cancer patients could receive personalized treatment if patients susceptible to develop metastases could be identified early. At the Institut Curie in Paris, researchers have identified a new prognostic marker that is associated to patients' susceptibility to develop metastasis after a primary breast cancer tumor.1 Heterochromatin protein 1a (HP1a) is a protein necessary to normal cell division, but Geneviève Almouzni's team has now shown that it also favors tumor growth when overexpressed. The higher the level of HP1a, the greater the risk of breast cancer patients developing metastases and dying.
HP1a, as well as its two isoforms b and g, belongs to a family of proteins called epigenetic (non-genetic) factors, which take part in packing and folding DNA in the nucleus. During normal development, cells acquire a specific pattern of gene expression which is then recorded to be faithfully propagated in a given cell lineage. This record is ensured by epigenetic factors, such as the HP1 isoforms. Almouzni's team analyzed human cells and tissue samples to investigate the expression of the three forms of HP1, in particular during cell proliferation and tumorigenesis. They found that only HP1a is associated to cell proliferation and that large amounts of this protein may facilitate cell growth. Conversely, a reduction of HP1a (not b and g) causes serious defects in dividing cells, implicating HP1a in cell division.
Moreover, they observed that HP1a was expressed at higher levels in tumor breast cells than in healthy ones, and therefore further investigated HP1a levels in a major retrospective study on 86 samples from breast cancer patients diagnosed in 1995. Only samples from early-stage tumors with no detectable metastases were included since researchers wanted to find prognostic markers for metastasis development. Interestingly, high HP1a expression correlated with the development of metastases. “Further work is needed to confirm these results,” says team member Leanne De Koning. In particular, prospective studies will be used to compare the prognostic value of HP1a with standard markers.

Barbara Rush

Notes :

1. L. De Koning et al., “Heterochromatin protein 1alpha: a hallmark of cell proliferation relevant to clinical oncology,” EMBO Mol Med 1, 2009. 178-91.

Contacts :

Leanne de Koning,
Institut Curie, Paris.


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