IDENTIFICATION AND VALIDATION OF NOVEL DRUG TARGETS FOR TREATMENT OF MULTIPLE MYELOMA
Currently, Multiple Myeloma (MM) is a treatable but incurable disease. The introduction of proteasome inhibitors and immunomodulatory drugs (IMIDs) constitutes a major advancement in expanding life expectancy, where remissions may be induced with combinations of steroids, chemotherapy, proteasome inhibitors (eg bortezomib) and IMIDs such as thalidomide derivatives, as well as stem cell transplantation. Radiation therapy can be used to reduce pain from bone lesions.
However, MM remains incurable because most patients eventually relapse or become refractory to current treatments. Due to heterogeneity within the cancer cell microenvironment, cancer cell populations employ a dynamic survival strategy to chemotherapeutic treatments, which frequently results in a rapid resistance to therapy. In addition to resistance conferring genetic alterations within new tumor cell populations arising from selection during drug treatment, there is also evidence for non-mutational mechanisms of drug resistance, involving epigenetic changes, and the generation of populations of “cancer stem cells”, which are intrinsically more refractory to the effects of a variety of anticancer drugs.
The aims of this research theme are to identify and validate novel drug targets and treatment concepts that address the current problems in MM therapy.
PROJECTS:
Disrupting ER homeostasis to induce apoptosis in multiple myeloma
PI: John Christianson, Ludwig Institute of Cancer Research, Oxford
The haematological malignancy multiple myeloma (MM) is typified by excessive proliferation of clones producing excessive amounts of non-functional immunoglobulin, which interfere with normal haematopoietic functions in bone marrow. The plasma cells from which MM arises are highly optimised protein factories, assembling antibodies in the endoplasmic reticulum (ER) at rates nearing ~ 1 x 103/cell/sec. These extraordinary rates of biosynthesis can only be maintained because of robust, adaptive quality control (QC) machinery that safeguards the integrity of secretory cargo by concomitantly promoting maturation while eliminating any aberrant forms that arise. Together, these tandem activities enable the ER to maintain homeostasis while accommodating elevated rates of protein flux. With a hypersecretory phenotype, MM is a disease tacitly relying on the QC machinery maintaining ER homeostasis in order to remain malignant. It is for this reason that strategies to disrupt ER homeostasis have proved therapeutically beneficial for the treatment of MM. The proteasome inhibitor class of small molecules (e.g. bortezomib, carfilzomib) exemplifies this strategy; blocking protein degradation which elevates ER stress to levels sufficient enough to activate cell death pathways and abate proliferation. After prolonged exposure however, patients become refractory to treatment with these compounds, likely due to cellular adaptation through enhancement of alternative protein degradation pathways. Thus, identifying cellular targets and processes in MM linked with ER homeostasis, which are non-redundant and thus more difficult to bypass and/or adapt to for viability (i.e. an Achilles heel), remains an important endeavour to find new therapeutic opportunities. Our laboratory has sought to define the extensive network of ER-resident ubiquitination machinery, their functions and relationship to organelle homeostasis. Of particular interest will be ubiquitin-related candidates sensitising proteasome inhibitor-resistant model cell lines, as they may reflect alternative entry points for apoptotic induction. The mechanisms responsible for maintaining homeostasis in the ER represent potentially valuable targets for therapeutic strategies to induce stress and cause cell death in MM. From our insight into the ubiquitination mechanisms at the ER, we anticipate that essential components will emerge from MM model cell lines, whose disruption will lead to ER stress and cell death.
Modulating the ubiquitin-proteasome system as a therapeutic strategy in multiple myeloma
PI: Benedikt Kessler, Target Discovery Institute, NDM, Oxford
Supported by EPSRC, CRUK/Forma Therapeutics
Inhibitors of the proteasome such as Bortezomib, Carfilzomib and Izazomib have been approved by the FDA and are used in the clinic to treat patients with multiple myeloma. Under current development are small molecule inhibitors against ubiquitin/SUME E1, E3 enzymes as well as deubiquitylating enzymes (DUBs), all of which have the potential to be effective against multiple myeloma, especially in relapsed patients. Multiple myeloma cells seem to be particularly vulnerable to interferences within protein turnover pathways. This is because a considerable proportion of secreted proteins are misfolded and need to be eliminated via the unfolded protein response and the ubiquitin system. In our laboratory, we are specifically exploring the role of DUBs in controlling protein turnover and metabolism in cancer cells. In particular, we have available a panel of small molecule inhibitors (through a collaboration with CRUK/Forma Therapeutics) with selectivity against DUBs. We intend to study their potency against a panel of cancer cell types, in particular multiple myeloma cells. We shall test cell type-specific sensitivity for these small molecules, and then subsequently study the role of the targeted DUBs in multiple myeloma cell viability. For instance, small molecule inhibitors against USP7 have already been shown to effectively kill multiple myeloma cells, including subtypes that have adapted to grow in otherwise toxic concentrations of proteasome inhibitors. We plan to study the roles of USP7 and other DUBs and their cellular ubiquitome in multiple myeloma cells using quantitative mass spectrometry, small molecules and genetic knockdown approaches.
Catalysing new drug targets for Myeloma through open science, and deep partnerships with industry, patient groups and academics across the globe.
PIs: Chas Bountra and all PIs at the SGC
Supported by SGC and IMI
Our primary objective in the SGC is to help our academic and industry colleagues discover and develop new drugs for patients. We have chosen to do this in four ways: (1) Pool expertise, infrastructures and resources: we are now working closely with nine large pharmaceutical companies, six patient organisations (including Myeloma UK), several SMEs and >200 academic labs dispersed across the globe. (2) Catalyse innovation by generating high quality novel reagents for novel drug targets, or targets considered to be undruggable. (3) Make all these reagents freely available to the global biomedical community, to enable ‘crowd sourcing’ of science and thereby de-risking of such targets. (4) Release all data, knowledge and reagents immediately, in order to minimise wastage of resources in other labs. As part of the Oxford Centre for Translational Myeloma Research we will: (1) Produce ‘Target Enabling Packages’ (TEPs: purified human proteins, biophysical and biochemical assays, three dimensional structures, chemical starting points for drug discovery, CRISPr reagents, antibodies) for novel genes or targets linked with Myeloma. We are already working with academic and industry scientists to prioritise such novel genes in cancer, inflammatory and metabolic diseases. We will help evaluate the potential of all cancer TEPs, and likely some of those linked with inflammatory and metabolic diseases in Myeloma. Cryo EM capabilities will allow us to explore integral membrane protein drug targets, more quickly than previously possible. (2) Generate novel, potent, selective, and cell penetrant inhibitors for high priority drug targets. We are routinely producing chemically similar but inactive molecules as controls for ex vivo work, and multiple chemotypes of inhibitors, for each drug target. Such target focussed toolkits are enabling superior ‘drug target discovery’. To date we have produced >60 novel inhibitors for novel epigenetic proteins, and >10 novel kinase inhibitors. In future we will produce several more of these, but also inhibitors for yeats, nudix, deaminase and ubiquitin proteins. Several of these are likely to have potential in Myeloma. Furthermore, from our pharma network we have acquired >20 inhibitors, some of which have previously been evaluated in patients. We are studying the effects of these in patient derived immune and cancer cells. We will assess all such novel inhibitors, in appropriate cellular Myeloma assays in order to identify new drug targets.
Drug Target Identification and Biomarker Profiling in Multiple Myeloma Using Chemoproteomics
PI: Kilian Huber, Target Discovery Institute, SGC, NDM, Oxford
Supported by Myeloma UK
Understanding the molecular targets of drugs and compounds discovered in phenotypic screens is a key parameter for drug discovery and personalized medicine. Many effective cancer therapeutics act by interfering with multiple protein targets some of which are referred to as “on-targets” required for cancer cell killing whereas “off-targets” can cause side effects by perturbing homeostasis in normal tissue. Uncovering the tumour-specific targets can thus enable the development of novel, more potent and selective treatments and prevent toxic side effects. As every cell expresses thousands of proteins, drug target identification represents a formidable challenge and requires systems-level approaches capable of surveying entire cellular proteomes. Our laboratory uses a suite of chemoproteomic approaches including drug affinity chromatography as well as thermal stability profiling to reveal the direct physical interactions between small molecules and proteins in cells and patient samples.
Identification of epigenetic mechanisms as target to treat drug resistance in multiple myeloma
PI: Udo Oppermann, Botnar Research Centre, NDORMS, Oxford
Supported by Oxford NIHR BRC
Epigenetic mechanisms comprise posttranslational chromatin modifications controlling gene expression programs, chromatin organisation and ultimately cellular phenotypes. The discovery that epigenetic and chromatin effector proteins are frequently dysregulated in cancer has led to the introduction of epigenetic therapies into the clinic, including e.g. inhibitors against histone methyl transferases (“writers”), demethylases or deeacetylases (“erasers”) and acetyl-lysine recognition (“reader”) domains. Our research aims to evaluate the therapeutic potential of epigenetic inhibitors using unique chemical and antisense toolkits that target epigenetic effector proteins.
We suggest that targeting the epigenetic and chromatin environment is not only a viable therapeutic concept in MM, but also has the potential to overcome acquired drug resistance which is observed in the vast majority of myeloma patients. Furthermore, we aim to understand the complex regulatory mechanisms within the network of MM cancer cells and the immune and stromal environment in the bone marrow with a view to modulate the pro-inflammatory tumor environment towards a milieu that allows selective tumor cell eradication.
Targeted delivery of drugs to bone-tissue to increase efficacy and reduce adverse effects in Multiple Myeloma
PIs: Oppermann, Russell, Ramasamy, Ebetino, Boeckmann
Supported by the Rosetrees Trust, Oxford NIHR BRC
The development of a bone-targeted drug for use in MM would represent a potential medical breakthrough for the treatment and management of MM and perhaps also for other haematopoietic or primary bone tumours. First, the future drug would augment existing drug treatments by addressing simultaneously the detrimental hallmarks of these tumour types, namely infiltration of bone tissue by cancer cells and induction of excessive bone resorption, which in turn leads to increased skeletal complications, including bone destruction, fractures and pain. Second, a tissue- targeted strategy will lower systemic drug levels, resulting in significantly fewer occurrences of adverse side effects, an important factor that in clinical practice often limits efficient treatments. Third, the ability to selectively and directly modulate and reshape the tumour microenvironment (including bone tissue, osteoclasts, osteoblasts and immune cells), addresses the challenges in MM therapy, where relapse and development of therapy resistance are thought to be critically dependent on the complex changes occurring in the cancer microenvironment.
In this project we are developing bone-tissue specific molecules for treatment of MM by combining highly active anti-cancer molecules with inert bisphonate molecules via a cleavable linker moiety. The well-studied bone tissue specificity of bisphosphonates provides an excellent vehicle to enrich anti-cancer molecules at their intended target sites.
