Using advanced laser imaging to reveal new targets for cancer therapies

Researchers have shown for the first time that a crucial interface in a protein that drives cancer growth could act as a target for more effective treatments. The study was led by the Science and Technology Facilities Council (STFC) Central Laser Facility (CLF) and used advanced laser imaging techniques to reveal new structural details of the mutated protein which help it to evade drugs that target it.It is published in Nature Communications and lays the groundwork for future research into more effective, long-lasting cancer therapies. The Epidermal Growth Factor Receptor (EGFR) is a protein that sits on the surface of cells and receives molecular signals that tell the cell to grow and divide. In certain types of cancer, mutated EGFR stimulate uncontrolled growth, resulting in tumours.Various cancer treatments block and inhibit mutant EGFR to prevent tumour formation, but these are limited as eventually cancerous cells commonly develop further EGFR mutations that are resistant to treatment. Until now, how exactly these drug-resistant EGFR mutations drive tumour growth was not understood, hindering our ability to develop treatments that target them. Advanced laser imaging In this latest study, scientists at CLF obtained super-resolution images of a drug-resistant EGFR mutation known to contribute to lung cancer. This was achieved using an advanced laser imaging technique called Fluorophore Localisation Imaging with Photobleaching, or FLImP. FLImP analysis revealed structural details as small as two nanometres and showed for the first time with this level of precision how molecules in the drug-resistant EGFR mutation interact. Additional analysis by the Biomolecular & Pharmaceutical Modelling Group at University of Geneva (UNIGE) used computer simulations that combined with the FLImP analysis were able to provide atomistic details of the mutant EGFR complexes. From this, the team were able to compare the structural details of the mutated and healthy EGFR to identify interfaces between interacting molecules in the drug-resistant mutation critical for tumour growth. Professor Marisa Martin-Fernandez, Leader of the Octopus Group at CLF, which led the study, explains: “This finding is the culmination of years of research and technological development at CLF and our partner institutions and we’re extremely excited about its potential to inform the course of cancer research going forward. If this interface proves to be an effective therapeutic target, it could provide an entirely new approach to much needed pharmaceutical development.” EGFR mutation blocks cancer growth The team then introduced additional mutations to the drug-resistant EGFR in in cultured lung cells and in mice that interfered with the newly discovered interfaces. In these experiments, one of the additional EGFR mutations was shown to block cancer growth, with mice developing no tumours, further indicating that the ability of this EGFR mutation to promote cancer indeed depends on these interfaces. Dr Gilbert Fruhwirth, Leader of the Imaging Therapies and Cancer group at King's College London who validated results in live animals, adds: "This research has become possible through the combination of a variety of different imaging technologies, ranging from single molecules to whole animals, and demonstrates the power of imaging to better understand the inner workings of cancer. We are extremely pleased about this successful collaboration and look forward to develop this pharmaceutical opportunity further as part of this team.” Diana Spencer caught up with Professor Marisa Martin-Fernandez, Octopus Group Leader at the STFC Central Laser Facility at the Rutherford Appleton Laboratory in South Oxfordshire, to find out more about the finding and the techniques used. Professor Marisa Martin-Fernandez. © STFC Central Laser Facilities. DS: Why is imaging so important in cancer research? MMF: Imaging technology at facilities like Central laser Facility (CLF) enables you to evaluate both the pathophysiological effects of disease and the effects of treatments in a real setting. From morphological changes in cells and tumours to changes to macromolecular structure. Our ability to image across these scales is paramount and will play an important role in our understanding of cancer formation, development, and treatment in the coming years. DS: What are the advantages of Fluorophore Localisation Imaging with Photobleaching (FLImP) over other imaging techniques? MMF: FLImP uniquely reveals the fingerprints of large cancer-driving macromolecular structures at an unprecedented resolution, crucially in the cellular context. Because, outside the cell, these structures are unable to form, they have not been studied by other means. We are incredibly proud of FLImP at CLF and would love for more drug discovery researchers to utilise the technology here in the future. DS: What is the potential of the technique? MMF: FLImP is great for structural investigations of protein complexes on the cell surface. Now with AlphaFold and/ or cryoEM we can readily formulate cell-free hypotheses on structure/ function relationships driving diseases like cancer, and use FLImP to test these hypotheses in the physiological context of the cell. DS: What could FLImP reveal in the future? MMF: In principle, any changes in the structure of large membrane protein complexes during the onset of disease or under treatment. One could imagine FLImP could stratify cohorts and assess treatment suitability and/ or inform if/ when the treatment has been successful at the molecular level prior to the onset of morphological changes. DS: Are there other studies ongoing? MMF: We are currently studying a portfolio of non-small cell lung cancer mutations to assess the general applicability of our findings. We also plan to extend our studies to glioblastoma multiforme and to tumours driven by wild type EGFR overexpression. DS: How could this latest finding change how we treat lung and other cancers? MMF: Our work has revealed unsuspected weaknesses in lung cancer that could potentially be exploited to develop new treatments. We hope that this ‘Achilles heel’ gives us an advantage that will open the way to overcome drug resistance. The next step is for pharmaceutical research teams to take up the gauntlet and test how we could target this weakness to deliver clinical results.