The role of RNA Binding Proteins (RBPs) in breast cancer progression and metastasis

Metastasis is the process by which cancer spreads through the body and colonises distant, sometimes vital, organs and tissues. It is estimated that more than 90% of all cancer related mortalities are due to metastasis. In breast cancer in particular, despite great advances in detection and treatment of the disease over the past decades, related mortality rates have remained high due to recurrence of cancer as metastases in secondary organs and tissues, which often happens several years after the initial diagnosis and treatment. Importantly, no therapies are currently available for breast cancer patients to prevent the spread of cancer within the body.

To metastasise, cancer cells must acquire the capacity to invade into their surroundings, move through tissues and vasculature, and colonise distant sites in the body. This requires activation of cellular pathways that promote cell movement. While much has been revealed on molecular machineries that mediate cell movement, little is known about regulators of movement which become abhorrently activated during metastasis. Recent works by me and other have revealed that an unexpected group of cellular proteins, called RNA Binding Proteins (RBPs), can promote cancer cell movement and invasion, ultimately leading to metastasis. However, it is unclear how different RBPs function to promote the movement of cancer cells, and more importantly, whether they could be targeted to tackle metastasis.

My research aims to reveal which RBPs are involved in regulating different aspects of cancer cell movement, cancer invasion, and ultimately metastasis in breast cancer. I will use cutting edge methodologies that I have been developing and using during my previous work, to systematically assess which RBPs are linked to the movement and metastasis of breast cancer cells. I will then assess how these RBPs are promoting movement and metastasis at the molecular level. Ultimately, such molecular level understanding of the processes that control cancer cell movement and metastasis may be useful for designing novel drugs to intervene in the metastatic process.

My aim is to assess the mechanisms by which invasiveness and metastatic behaviour is regulated via different RNA Binding Proteins (RBPs) in breast cancer cells. While much has been revealed on molecular machineries that control cell motility, little is known about upstream regulators of motility which are deregulated during metastasis. Recent works by me and others have highlighted a crucial role for regulation of local mRNA translation in controlling cell protrusions and adhesions. Accordingly, various RBPs have been reported to localise to such motility related compartments and control cell-migration, invasion, and metastasis. However, it is unclear how different RBPs function to regulate cell motility, and whether their activity could be targeted to tackle cancer dissemination.

I will use sub-cellular fractionation coupled with proteomics to reveal RBPs that associate with specific motility related compartments in invasive breast cancer cells. Using RNAi in combination with morphology, migration, and invasion assays, I will reveal key RBPs that regulate breast cancer cell motility in-vitro. RBP roles in-vivo, in regulation of local invasion to lymph nodes and distant metastasis will then be assessed using orthotopic mouse models. Using fractionation coupled with RNAseq and pulse-labelling proteomics, I will investigate how loss of RBPs affects RNA localisation and local translation in motility associated cellular compartments where RBPs are localised. Through analysis of UTR sequence elements, along with methods to assess mRNA-protein binding, I will determine the mechanisms of interaction between RBPs and their local target mRNAs. Finally through mutagenesis, I will abrogate mRNA-RBP bindings and assess the impact on invasiveness and metastasis. Showing that specific RBP-mRNA interactions can impact on invasiveness and metastatic potential may lead to devising new therapeutic strategies to tackle cancer dissemination by disrupting such interactions.

Academia:
The findings of this research proposal are likely to be of interest to scientist across various different disciplines, both in basic and applied research fields, within the UK and abroad. In addition to cancer biologists, academics in basic research fields studying RNA biology are likely to benefit from the results of this research. Other target academics include developmental biologists and neurobiologist who study the role of RBPs in various different normal or pathological contexts. Many of the RBPs that seem to be associated with cell-motility are also known have roles in development and maintenance of the nervous system, with a number of them having been implicated in neuronal disorders, such as Fragile-X mental retardation and amyotrophic lateral sclerosis (ALS). Thus, findings of this proposal are likely to be of great interest to these scientists, as well as those within the immediate related fields of my research.

Industry:
Apart from benefiting academics, findings of this proposal may pave the way for pharmaceutical companies to devise novel therapeutic strategies that tackle cancer cell motility through the use of RNA therapeutics. Specifically, my research will reveal the molecular details of interactions between certain RBPs and their target mRNAs that mediate RBP effects on cancer cell motility. Such data can be used to design RNA mimicking compounds that can interfere with the RBP-mRNA interactions, in order to inhibit cancer cell movement. Efforts to target RBP-mRNA interactions through use of our findings may not be limited to cancer therapeutics, and could be also useful for pharmaceutical companies which are active in developing drugs for different neuronal disorders, since as mentioned above, a number of RBPs associated with motility also seem to be important players in certain neuronal disorders. Crucially, latest advances in RNA therapeutics, particularly the recent development of small molecules that sterically interfere with certain protein-RNA interactions, suggests that there is likely to be great potential for clinical targeting of RBPs in the near future.

General Public:
Ultimately, if this study contributes towards development of novel therapies that target breast cancer metastasis, the general public will be the main beneficiary in the long run. Metastasis remains the major cause of death due to breast cancer, and currently no specific therapies that target metastasis exists in the clinic. Also, as mentioned above, knowledge generated from this work may also lead to devising novel treatments for certain neuronal disorders, ultimately benefiting public health.