Professor Richard Clarkson

Publication

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Research

Targeting metastatic disease

The spread of malignant tumours around the body, termed metastasis, is the principal cause of death in patients with solid tumours. The Clarkson lab has identified two intra-cellular mechanisms that appear to contribute to this process in models of breast cancer.  Now situated in the European Cancer Stem Cell Research Institute, the research group has focused its attentions on identifying molecular strategies to target these mechanisms and thus prevent malignant disease progression.

The first of these pathways affects the viability of cancer stem cells through regulation of TRAIL mediated apoptosis, targeting an innate inhibitor of this pathway, cFLIP.  Inhibition of this mechanism sensitizes these cells to cytotoxic agents. The second pathway focuses on Bcl-3 which impinges on the ability of tumour cells to migrate through tissues and has a direct effect on the ability of tumours to metastasise.  Ongoing studies are aimed at characterizing these mechanisms in more detail, determining their efficacy in primary cancer tissues obtained from local cancer clinics and establishing their involvement in the biology of cancers arising from a variety of tissue types including breast, ovarian, prostate and pancreatic.

Targeting apoptosis and the cancer stem cell

The Clarkson lab has a long-standing interest in how genes that have presumptive roles in the removal / reorganization of supernumerary cells from adult tissues could play a role in breast and other forms of cancer.

Having initially focused on identifying genes that control apoptosis in mouse mammary tissues (Clarkson, 2003) the lab subsequently used conditional transgenics to modify gene activity in normal and cancer cells in vitro and in vivo to observe the effects of these changes on tumour behaviour with mammary (breast) cancer as the primary model.

Much of the ongoing work in the lab stems from two microarray-based studies of mammary involution and epithelial apoptosis (Clarkson 2000; 2003; 2006). Thus, in a global analysis of the mammary transcriptome during the pregnancy cycle it was deduced from gene expression profiles that two distinct cell-death pathways were sequentially activated during involution, the first characterized by the activation of members of the TNF superfamily, a cytokine activated pathway implicated in extrinsic (death receptor mediated) apoptosis and the second associated with remodeling enzymes. We also identified a possible molecular link between these two phases of involution, involving the transition from LIF-STAT3 to OSM-STAT1 signalling in mammary epithelial cells (Tiffen, 2008).

However, in a recent study using a conditional inhibitor of caspase activity (baculovirus p35 protein) in murine mammary tissues, the Clarkson lab provided evidence to support the proposal that apoptosis was redundant during mammary involution (Kreuzaler, 2011).

The identification of TNF-related signaling components in the mammary gland led to the investigation of the role of TNFR-associated inhibitory molecule c-FLIP in the maintenance of breast stem cancer cells (Piggott, 2011, French, 2015).  More recently the lab showed that this c-FLIP/TRAIL axis was perturbed in ER-positive breast tumours that develop acquired resistance to endocrine therapy, making the cancer stem cells hypersensitive to TRAIL mediated killing (Piggott, 2018). This has led the group to propose that clinically approved TRAIL agonists could be an effective second line therapy for breast cancer patients who relapse on endocrine therapy.

In a separate microarray study, conditionally active forms of two STAT transcription factors, STAT3 and STAT5 were used to identify the genes responsible for their known roles in mammary cell apoptosis and differentiation respectively (Clarkson, 2006). This has led to the identification of a number of gene targets that are likely to play important roles in the maintenance of tissue homeostasis in the mammary gland, one of which, Bcl3, is the subject of ongoing studies within the lab due to its surprising role in disease progression in vivo (Wakefield, 2013; Turnham, 2020).  The lab has shown that Bcl3 plays a novel and non-redundant role in the migration and metastasis of breast tumour cells and colorectal cancer stem cells (Legge, 2019) mediated through Bcl3-NF-kB complexes (Yeo, 2017, Turnham, 2020).

Pharmacological targeting of cancer stem cells

Based on the evidence of Bcl3 and c-FLIP involvement in cancer stem cell maintenance and metastasis the Clarkson lab has collaborated with Prof Andrea Brancale and Prof Andrew Westwell of the Cardiff University School of Pharmaceutical Sciences to develop novel pharmacological agents targeting these intra-cellular pathways.  Thus, using state-of-art molecular modelling and in silico compound screening they have identified potent first-in-class inhibitors of both Bcl3 and c-FLIP (Soukupova, 2021, French, 2021, manuscript in preparation). These agents are currently undergoing further pre-clinical evaluation to determine their suitability for clinical trials in breast, colorectal and other cancer patients. The candidate small-molecule inhibitor of Bcl3 is in late-stage pre-clinical development, having completed toxicology in several species and with large scale API awaiting formulation.

Future work in the Clarkson lab will increasingly focus on the mechanisms underlying the dissemination of cancer stem cells and the propagation of metastatic disease, and working with their collaborators (below) to continue to develop novel therapeutic strategies that target these cancer stem cell-related pathways.

Current grant support

• Cancer Research Wales
• Sêr Cymru – Welsh Government
• Health Care Research Wales
• Pancreatic Cancer Research Fund

Collaborators

• Andrew Westwell, Andrea Brancale – School of Pharmacy, Cardiff University
• Jen Morton – Beatson Institute, Glasgow
• Erin Hertlein – OSUCCC, James, OHIO State University
• Blake Peterson – OHIO University, College of Pharmacy
• Rob Jones MRCP, PHD – Phase 1 clinical trial lead, Velindre Cancer Centre, Cardiff
• Stephen Paisey, Chris Marshall - Wales Research and Diagnostic Positron Emission Tomography Imaging Centre (PETIC), Medical School, Cardiff University
• Matthias Eberl – Dept Infection, Immunity and Biochemistry, Cardiff School of Medicine
• Julia Gee – School of Pharmacy, Cardiff University
• Peter Barrett-Lee - Medical Director, Velindre Cancer Centre, Cardiff
• Dr Philippa Young - Consultant Radiologist, Cardiff Breast Clinic
• Dr Luke Piggott - Debiopharm, Switzerland

Staff members

• Gillian Seaton

Postgraduate research students

• Anna Richards
• Kok Yung Lee

Supervisions

Our research group has collaborated with leading researchers from the School of Pharmacy to develop pharmacological inhibitors of cancer stem cells.  These rare cells within solid tumours are responsible for the spread of cancers around the body (metastasis) and for disease relapse and tumour recurrence after traditional therapies.  Our lab investigates the cell biology of these cancer cells and the molecular/cellular pathways influencing their behaviour and viability.  We particularly focus on the induction of apoptosis and the ability of these cells to disseminate and colonise distal sites within the body.

Techniques:  Cell and tissue culture, mouse biology and cancer xenografts, apoptosis assays.  Trasncriptomics, RNAseq, siRNA, inducible shRNA and fluorescence/luminescence of cancer cells by confocal microscopy and timelapse fluorescence.