(Impact Journals, 2017) Martín Sánchez, Esperanza; Mendaza Lainez, Saioa; Ulazia Garmendia, Ane; Monreal Santesteban, Iñaki; Blanco Luquin, Idoia; Córdoba Iturriagagoitia, Alicia; Vicente García, Francisco; Pérez Janices, Noemi; Escors Murugarren, David; Megías, Diego; Ciencias de la Salud; Osasun Zientziak; Gobierno de Navarra / Nafarroako Gobernua
The CHL1 gene encodes a cell-adhesion molecule proposed as being a putative
tumour-suppressor gene in breast cancer (BC). However, neither the underlying
molecular mechanisms nor the clinical value of CHL1 downregulation in BC has
been explored. The methylation status of three CpG sites in the CHL1 promoter
was analysed by pyrosequencing in neoplastic biopsies from 142 patients with
invasive BC and compared with that of non-neoplastic tissues. We found higher
CHL1 methylation levels in breast tumours than in non-neoplastic tissues, either
from mammoplasties or adjacent-to-tumour, which correlated with lower levels of
protein expression in tumours measured by immunohistochemistry. A panel of five BC
cell lines was treated with two epigenetic drugs, and restoration of CHL1 expression
was observed, indicating in vitro dynamic epigenetic regulation. CHL1 was silenced
by shRNA in immortalized but non-neoplastic mammary cells, and enhanced cell
proliferation and migration, but not invasion, were found by real-time cell analysis.
The prognostic value of CHL1 hypermethylation was assessed by the log-rank test
and fitted in a Cox regression model. Importantly, CHL1 hypermethylation was very
significantly associated with shorter progression-free survival in our BC patient series,
independent of age and stage (p = 0.001). In conclusion, our results indicate that
CHL1 is downregulated by hypermethylation and that this epigenetic alteration is an
independent prognostic factor in BC.
