The Huntington disease protein accelerates breast tumour development and metastasis through ErbB2/HER2 signalling.
Bottom Line: In agreement, mutant huntingtin accelerates epithelial to mesenchymal transition and enhances cell motility and invasion.Finally, we report that in HD, the dynamin dependent endocytosis of the ErbB2/HER2 receptor tyrosine kinase is reduced.This leads to its accumulation and to subsequent increases in cell motility and proliferation.
Affiliation: Institut Curie, Paris, France; CNRS UMR 3306, Orsay, France.Show MeSH
Related in: MedlinePlus
Mentions: To test this hypothesis, we analysed primary tumour sections by immunohistochemistry (Fig 3A). Lowered levels of the cell–cell adhesion proteins E-cadherin and β-catenin were observed in the MMTV-PyVT/HdhQ111/Q111 tumours, while the mesenchymal marker α-smooth muscle actin (α-SMA) was increased. We then analysed extracts from MMTV-PyVT/HdhQ7/Q7 and MMTV-PyVT/HdhQ111/Q111 tumours by immunoblotting (Fig 3B). The MMTV-PyVT/HdhQ111/Q111 tumours had lower levels of the tight junction protein zonula occludens 1 (ZO1), E-cadherin and β-catenin, and an increased level of the mesenchymal marker vimentin compared to MMTV-PyVT/HdhQ7/Q7 tumours. Similarly, E-cadherin, β-catenin and vimentin levels were affected in MMTV-ErbB2/HdhQ111/Q111 tumours as compared to MMTV-ErbB2/HdhQ7/Q7 tumours (Supporting Information Fig S2C). We next derived primary tumour cells from the MMTV-PyVT/HdhQ7/Q7 and MMTV-PyVT/HdhQ111/Q111 tumours (PyVT/HdhQ7/Q7 and PyVT/HdhQ111/Q111, respectively). Doubling-time measurements showed no significant difference between wild-type (PyVT/HdhQ7/Q7) and polyQ-huntingtin-expressing cells (PyVT/HdhQ111/Q111) (12.38 ± 0.25 h and 12.65 ± 0.22 h, respectively, PLSD Fisher test p-value = 0.4357). However, further confirming the microarray data, polyQ-huntingtin expression led to a mesenchymal-like phenotype in the PyVT/HdhQ111/Q111 cells, which became scattered and elongated compared to phenotype of the PyVT/HdhQ7/Q7 cells (Fig 3C). Also, the observations done on tumours with respect to the levels of ZO1, E-cadherin, β-catenin and vimentin were confirmed in an immunoblot analysis of extracts from PyVT/HdhQ7/Q7 and PyVT/HdhQ111/Q111 tumour cells (Fig 3D). Immunostaining confirmed that E-cadherin and β-catenin production were substantially lower in polyQ-huntingtin-expressing cells (Fig 3E). Furthermore, β-catenin exhibited membrane localization in PyVT/HdhQ7/Q7 cells and diffuse cytoplasmic localization in PyVT/HdhQ111/Q111 cells, which is consistent with decreased cellular adhesion. In summary, mutant huntingtin expression in primary tumour tissue and in tumour-derived cells affects the levels of known cell adhesion markers and mesenchymal markers. Furthermore, when mutant huntingtin is expressed, tumour cells in culture adopt an altered morphology resembling a mesenchymal phenotype.
Affiliation: Institut Curie, Paris, France; CNRS UMR 3306, Orsay, France.