HIF-1 alpha-independent hypoxia-induced rapid PTK6 stabilization is associated with increased motility and invasion

© 2014 Landes Bioscience. PTK6/Brk is a non-receptor tyrosine kinase overexpressed in cancer. Here we demonstrate that cytosolic PTK6 is rapidly and robustly induced in response to hypoxic conditions in a HIF-1-independent manner. Furthermore, a proportion of hypoxic PTK6 subsequently re-localized to the cell membrane. We observed that the rapid stabilization of PTK6 is associated with a decrease in PTK6 ubiquitylation and we have identified c-Cbl as a putative PTK6 E3 ligase in normoxia. The consequences of hypoxia-induced PTK6 stabilization and subcellular re-localization to the plasma membrane include increased cell motility and invasion, suggesting PTK6 targeting as a therapeutic approach to reduce hypoxia-regulated metastatic potential. This could have particular significance for breast cancer patients with triple negative disease

WSB-1 regulates the metastatic potential of hormone receptor negative breast cancer

© 2018 Cancer Research UK. Background: Metastatic spread is responsible for the majority of cancer-associated deaths. The tumour microenvironment, including hypoxia, is a major driver of metastasis. The aim of this study was to investigate the role of the E3 ligase WSB-1 in breast cancer biology in the context of the hypoxic tumour microenvironment, particularly regarding metastatic spread. Methods: In this study, WSB-1 expression was evaluated in breast cancer cell lines and patient samples. In silico analyses were used to determine the impact of WSB-1 expression on distant metastasis-free survival (DMFS) in patients, and correlation between WSB1 expression and hypoxia gene expression signatures. The role of WSB-1 on metastasis promotion was evaluated in vitro and in vivo. Results: High WSB1 expression was associated with decreased DMFS in ER-breast cancer and PR-breast cancer patients. Surprisingly, WSB1 expression was not positively correlated with known hypoxic gene expression signatures in patient samples. Our study is the first to show that WSB-1 knockdown led to decreased metastatic potential in breast cancer hormone receptor-negative models in vitro and in vivo. WSB-1 knockdown was associated with decreased metalloproteinase (MMP) activity, vascular endothelial growth factor (VEGF) secretion, and angiogenic potential. Conclusions: Our data suggests that WSB-1 may be an important regulator of aggressive metastatic disease in hormone receptor-negative breast cancer. WSB-1 could therefore represent a novel regulator and therapeutic target for secondary breast cancer in these patients

Investigating the role of WSB-1 in breast cancer

Breast cancer is the second most represented cancer type worldwide and will affect 1 in 8 women in the UK. Overall patient survival can reach 90% when the disease is diagnosed early but rapidly drops as the tumour progresses and metastasises. The steps required for tumour formation are known but numerous factors are involved and the specific mechanisms controlling this phenomenon are still poorly understood. WSB-1 is a hypoxia-responsive E3 ubiquitin ligase which was found to be upregulated in metastatic tissues, compared to normal or non invasive tissues. In addition, studies demonstrated that WSB-1 was involved in pancreatic cancer, neuroblastoma, and osteosarcoma progression. However, its role in breast cancer has not been particularly studied.The objective of this thesis is to study the role of WSB-1 in breast cancer. Initially, level of WSB1 in patients' tumour cDNA samples was evaluated according to known clinical and biological variables. Impact of high WSB1 levels on patients' distant metastasis-free survival, relapse-free survival and overall survival was also investigated. Then, the effect of WSB-1 knockdown on protein levels of epithelial to mesenchymal transition markers, as well as several matrix metalloproteinases (MMP) transcript and protein levels, and activity was examined. Consequence of these modifications on cell motility (migration, invasion) was studied, using single cells, cellular monolayers and spheroids. Finally, affinity purification followed by mass spectrometry was used to identify novel WSB-1 partners.Overall, in MDA-MB-231 cells, WSB-1 appeared to drive metastasis formation by upregulating MMPs expression and activity, promoting EMT and inducing invasiveness. WSB-1 had a more conflicting effect in MCF7 cells. In fact, WSB-1 effect appeared to be depending on the ER- and ER+ status.Together, these results validated WSB-1 as an important player in breast cancer development, particularly in metastasis formation