Determining the role of autophagy in mediating resistance to proteasome inhibition in multiple myeloma

Myeloma is a common bone marrow cancer with over 5,000 patients diagnosed annually in the UK. Patients with myeloma have cancerous cells in their bone marrow that grow in an uncontrolled fashion and secrete abnormal proteins into the bloodstream. Although new treatments have been developed for myeloma in the last 5 years, it remains an incurable disease, with nearly 3000 deaths yearly.

One of the main chemotherapy treatments used for treating myeloma are drugs called proteasome inhibitors (PIs). These drugs prevent the myeloma cells from breaking down toxic proteins present in the cell by blocking their internal degradation system - known as the proteasome. When patients are given these drugs, the toxic proteins build up in the myeloma cells causing them to become stressed and die. PIs have improved the survival of myeloma patients but there are a group of patients whose cancer is not killed by this treatment. Furthermore, in most patients the cancerous cells will grow back after a period of time and they will require more treatment. We therefore urgently need to find better treatments for these patients.

This project will investigate how myeloma cells become resistant to the PI drugs. We believe that in some cases, the myeloma cells are able to use a process called autophagy, to avoid being killed by the PI drugs. Autophagy is a process by which cells clean up waste products - in effect a recycling process that acts to break down unwanted proteins, thereby allowing the cell to remain healthy. Autophagy has been shown to become more active in cancers and help cancer cells to survive for longer. In myeloma when excess protein builds up, the autophagy process becomes more active in order to recycle waste proteins, and therefore avoid death. We know that there are different types of myeloma cancers based on genetic changes in the tumour. Initial research from our laboratory has shown that particular subtypes of myeloma with specific genetic features have a high level of autophagic activity, and appear to use the autophagy process to survive drug treatment with PI. Patients with these genetic features on average have shorter survival compared to patients who do not and this may be related to the resistance of their myeloma cells to PI drugs. Thus, if we can shut down the autophagy process using anti-autophagy drugs, this may improve the ability of PI drugs to kill the cancerous myeloma cells.

Carfilzomib is a new PI drug which is now available for treating myeloma and is widely used in clinical trials. We have tested the ability of Carfilzomib to kill myeloma cells in the laboratory. We have found that myeloma cells behave differently according to their genetic background, with some myeloma cells being killed by carfilzomib on its own whilst others are more likely to be killed when extra drugs are added to block the autophagy pathway. I believe that combining PI drugs with those that block autophagy will increase the effectiveness of our PI therapies, and improve the outlook for patients.

In this project, I aim to:
1. Assess the effect of blocking autophagy in myeloma cells
2. Investigate how myeloma cells survive treatment with PI drugs by studying changes in autophagy protein levels and proteins involved in cell death
3. Investigate whether combining PI drugs with anti-autophagy drugs can kill myeloma cells in a mouse myeloma model

Our goal is to determine if myeloma cells can be destroyed by PI drugs when we switch off autophagy. This is particularly important for those patients in whom the currently available drugs are ineffective. We would also like to identify potential biomarkers (proteins or genes that can be reliably measured) to predict which patients are likely to have better outcomes when given autophagy blocking drugs in combination with PI drugs. We can therefore give myeloma patients treatment they are most likely to benefit from rather than using the same chemotherapy regimens for everyone.

Multiple myeloma is a common haematological cancer with considerable genetic heterogeneity. This condition remains incurable, and disease resistance to proteasome inhibitors (PI) remains a major barrier to achieving durable remissions for patients. The work in this fellowship will investigate the role of autophagy in mediating resistance to proteasome inhibition therapy (carfilzomib) in multiple myeloma, and define distinct subgroups of patients who will benefit from dual targeting of autophagy and the proteasome.

Patient bone marrow samples and myeloma cell lines will be exposed to carfilzomib (second generation PI) and autophagy inhibitors (AI) and cellular cytotoxicity, autophagy protein levels and autophagic function will be assessed. Results will be analysed seeking correlations with genetic translocations and basal autophagic function and reserve. RNASequencing will be used to seek transcriptomic differences underlying divergent cytotoxicity responses in HMCL exposed to PIs +/- AIs. Efficacy of selected combination therapy with PI and AI will be further assessed using ex vivo and in vivo MM models. Patient samples from the NCRN Cardamon study (newly diagnosed MM patients treated with Carfilzomib based regimen) will be examined for relevant autophagic proteins and function identified from previous cell line work, correlating with disease response.

Results of this work will contribute to understanding the mechanisms underlying PI resistance, and the therapeutic potential of AI's in combination therapy with PI. Identification of key genes may provide predictive biomarkers for use in phase I combination studies of PI and autophagy modulators. Mechanistic insights will also identify potential novel therapeutic targets to aid future drug development.

Our research will be of interest to clinicians treating patients with multiple myeloma (MM) and haematologists using proteasome inhibitors (PIs) to treat a variety of haematological malignancies including B-cell non Hodgkin lymphomas. Oncologists using PIs in clinical trials and in in-vivo studies as potential therapies for solid organ tumours will also find our work of interest, as well as the wider scientific community working in the field of autophagy.

PIs are a major class of anti-MM drugs, but not all patients respond and most relapse. Attempts to improve outcomes of therapy by using multi-drug combinations have yielded only incremental benefits, largely because of disease heterogeneity and different pathways contributing to resistance. Uncovering mechanisms of drug resistance is therefore key to improving patient outcomes. Our research will improve our understanding of the mechanisms of PI resistance in MM, and so will identify potential therapeutic targets to aid future rational drug design. By identifying novel drug targets, new combination regimens could be developed to re-induce disease response in previously relapsed refractory patients, a group traditionally with poor outcomes. Unpicking the mechanistic basis of PI resistance in MM and the role autophagy plays will enable identification of novel biomarkers to predict disease response to combination PI and AI therapy. Using predictive biomarkers identified from our work will help haematologists to risk stratify patients at time of relapse, improving clinical outcomes with potential saving on precious healthcare resources, and enable clinicians to select patients likely to benefit from this regimen, whilst preventing unnecessary toxicity in those that do not.

Collaborations with industry to develop gene expression-based biomarkers may facilitate biomarker testing to become available on a commercial basis. Patient samples could be screened at relapse to identify presence of resistance signatures and help direct treatment in a targeted fashion. This would allow patients to be treated with drugs they are more likely to derive benefit from, improve survival, as well as time to next treatment therapy. This will ultimately benefit not only patients, but also their families and carers, increasing wellbeing and economic independence. Being able to predict what drugs patients are likely to respond to would revolutionise cancer treatment and would have a huge impact on patient care by ultimately personalising each patient's treatment based on their tumour's unique behaviour.

The research outputs from this fellowship align directly with the MRC's strategic plan to strengthen the research base in an important scientific area to directly impact positively upon human health. This clinical research training fellowship will provide me with skills to pursue a Clinician Scientist award and translate novel drug design from bench to bedside. By regularly interacting with researchers at UCL running early phase trials, I will gain experience in participation and running of clinical trials, as well as governance and regulatory practices relating to trial set up. Furthermore, the haematology department at UCL has a track record of mentoring academic clinicians to develop their academic careers, which I will have access to. The training environment at UCL and research skills I will gain from this fellowship will enable me to pursue a career as a clinical researcher who will be able to fast track novel agents into the clinic to help improve outcomes for patients with haematological malignancies.