Ran GTPase as a potential novel therapeutic target in EMT transdifferentiation and breast cancer stem cell (BCSC) survival during metastatic development

Breast cancer is the leading cause of cancer death in women worldwide. Accumulating evidence suggests that local disease recurrence and metastatic lesions, the major causes of patient mortality, are due to a subset of aggressive cells termed cancer stem cells (CSCs). CSCs have self-renewal and differentiation ability and are defined phenotypically by their ability to form new tumours following injection into host mice. Several studies have demonstrated that BCSCs have the capacity to disseminate and have been shown to be a key cause of metastatic colonisation in distant tissues. BCSCs have recently been shown to exist in mesenchymal-like (epithelial-mesenchymal transition (EMT)) and epithelial-like (mesenchymal-epithelial transition (MET)) states. Moreover, mesenchymal-like BCSCs are localised to the tumour invasive front and are CD44high/ CD24low, whereas epithelial-like BCSCs are aldehyde dehydrogenase (ALDH) positive and localised in the centre of the tumour.

Ran is a Ras-related GTPase that is critical for mitosis, apoptosis and nucleo-cytoplasmic transport. We identified Ran as a novel mediator of cancer metastasis. We and others have shown that cancer cells are more susceptible to Ran silencing than normal cells. Overexpression of Ran in tumour tissue is also significantly associated with poor patient outcomes in breast, lung, ovarian and renal cell cancers. We have also demonstrated that Ran expression can predict patient survival in breast cancer subtypes such as HER-2, ER and lymph node involvement. In addition, we and others have shown that Ran overexpression may play a role in the metastatic development of breast cancer, highlighting a novel role of Ran in cancer progression.

We hypothesise that Ran is a key molecule in driving EMT and BCSC survival during breast cancer metastasis. Moreover, we hypothesise that Ran-driven EMT induces many of the defining features of stem cells, including self-renewal ability, enabling the cells to both physically disseminate from the primary tumour and generate a self-renewal capacity.

Research plans

Aim 1: The role of Ran signalling in EMT regulation
1. Assessment of modulated Ran expression upon cell adhesion, migration/invasion and colony:
2. Investigate Ran activates molecules of the RhoA GTPase/FAK effector pathway by TGF-β1- dependent pathways:
3. Investigate the collaboration between Wnt signalling and Ran-dependent EMT
4. Assessment the clinical associations between Ran, TCF-4, TGF-β1, Slug Snail, Twist, Vimentin and E-cadherin proteins expression and patient outcome:

Aim 2: The role of Ran signalling in breast cancer stem cell maintenance
(Objectives are
1. Characterisation of breast cancer stem cells:
2. Characterisation of Ran-dependent stem cell-like properties of CD44high/CD24low cells:

Aim 3: Investigate the selective targeting of Ran inhibitor, Rani peptide (Rani), on human-derived BCSCs in vitro.