Research projects

Isolation and characterisation of GBM cancer stem cells

Contributors: Kate Broadley, Kathryn Farrand, Mr Martin Hunn, Dr Patries Herst, Dr Ian Hermans, Dr Melanie McConnell

Cancer cells grow under conditions of metabolic and energetic stress. During chemotherapy and radiotherapy treatments of cancer patients, these cells are subjected to further stress, yet some are able to survive and go on to cause relapse and metastasis. This is thought to be due to the presence of cancer stem cells, which are drug and radiation resistant.

Dr Melanie McConnell's Cell Survival Group has established various methodologies to allow identification of cancer stem cells and to characterise their function. They are using different cancer models to study the different properties of cancer stem cells – self-renewal and resistance to radiation and chemotherapy using glioblastoma multiforme (GBM) cells; drug resistance in melanoma cells; and metastasis using breast cancer cells.

They have used stem cell culture, stem cell gene markers and drug resistance to identify a population of cells in GBM tumours that are highly tumourigenic and potentially immune suppressive. Neurosurgeon and Malaghan Clinical Research Fellow Mr Martin Hunn has shown that these cells can be recognised by the immune system and protect against tumour development.

Using dendritic cell immunisation to sensitise malignant glioma to chemotherapy

Contributors: Mr Martin Hunn, Kathryn Farrand, Kate Broadley, Dr Melanie McConnell, Dr Ian Hermans

One of the long term aims of the Vaccine Research Group is to develop effective and safe immunotherapies for high grade glioma (brain cancer). Complementing the phase I GBM clinical trial is a basic research programme involving Mr Martin Hunn that is investigating the possibility of directing anti-tumour immune responses specifically against GBM.

Current work is focused on developing a murine model of glioma in which to assess the efficacy and safety of vaccination strategies directed at drug-resistant tumour stem cells, to support the translation of this novel immunotherapy into clinical trial. Mr Hunn has shown that the GBM cells can grow as detached 'neurospheres' in appropriate culture media and that these spheres show increased expression of stem cell-related genes and initiate tumours earlier compared to parental tumour cells.

Mr Hunn will also undertake an in vitro assessment of the immune responses of patients with recurrent GBM who are being treated with the dendritic cell vaccine in the phase I clinical trial.

Immunotherapeutic targeting of melanoma stem cells

Contributors: Carole Grasso, Kate Broadley, Prof Mike Berridge, Dr Melanie McConnell, collaborating with Prof Jonathan Cebon (Ludwig Institute, Australia)

As part of a Melanoma Research Alliance-funded collaborative international programme aimed at using immunotherapy to target melanoma stem cells, Prof Mike Berridge, Dr Melanie McConnell and colleagues have explored the role of the putative tumour stem cell surface marker, CD133, in defining tumour-initiating (stem-like) cells in primary human metastatic melanomas.

The tumour-forming capabilities of two distinct populations of malignant melanoma cells, CD133+ and CD133-, were determined by serial passage in NOD/SCID immunocompromised mice. Unexpectedly both populations of cells were shown to initiate and sustain tumour growth with similar frequency, suggesting that CD133 is not a defining marker of stem cells for human malignant melanoma. CD133 negative cells were shown to express CD133 mRNA and intracellular protein, suggesting a failure of exocytosis independent of tumour-forming ability.

Current research is focused on searching for other potential melanoma stem cell markers.

Unleashing the power of the immune system on metastatic breast cancer

Contributors: Dr Melanie McConnell, Dr Troels Petersen, Dr Heli Matilainen, Ching-Wen Tang, Prof Mike Berridge

The Malaghan Institute's breast cancer programme, supported by BCRT, aims to develop functional vaccination strategies that induce a patient's immune cells to seek out and destroy the cells responsible for the initiation and spread of tumours. During the first year of this project a preclinical model of metastatic breast cancer has been established.

Research has also been undertaken to investigate the tumour-forming ability of cells grown under conditions that generate tumourspheres, cell clusters that in other tumour models exhibit cancer stem cell-like properties. Surprisingly, cells from breast cancer tumourspheres did not express stem cell-like gene expression markers and did not produce more aggressive tumours. Furthermore, cells from tumourspheres showed lower lung metastases, suggesting they are not stem cell-like. This led researchers to focus on the metastatic cells in the lungs of tumour-bearing mice and to use these cells in vaccination approaches.

An important outcome of this work has been the demonstration that breast cancer cells are immunogenic and generation of immune responses can protect against tumour growth and metastasis.

Sirtuins, stress and survival: A problem in anti-tumour therapy

Contributors: Susanna Brow, Kate Broadley, Dr Patries Herst, Dr Melanie McConnell

A fundamental aspect of cancer cell survival is the ability of cancer cells to change the metabolic pathways to cope with cellular stress. Understanding the survival mechanisms is key to designing effective anti-tumour therapeutics.

The sirtuin family (SIRT1-SIRT7) are NAD+-dependent enzymes with deacetylase activity, ADP-ribosyl transferase activity, or both. Based on NAD+- dependence, SIRT1 in particular has been postulated to be a metabolic sensor, relaying information on the metabolic status of the cell to the regulators of gene expression.

SIRT1 inhibition has the potential to bring specificity to cancer treatment, if in fact normal cells are less reliant on SIRT1-mediated survival pathways. In particular, where a conventional approach such as chemotherapy causes a stress response and induces survival pathways in the target cell, combining SIRT1 inhibition with that approach will potentially allow greater efficacy of cancer cell drug targeting.

The Cell Survival Group is investigating whether SIRT1 inhibition reduces cancer cell survival when combined with cytotoxic drugs, radiation or oxidative stress.

SIRT1 and stress responses in MND

Contributors: Susanna Brow, Dr Melanie McConnell

A new research programme, supported by the Motor Neurone Disease Association of NZ and the estates of Ellen, Sinclair, Barbara and Alison Wallace, has recently been initiated at the Malaghan Institute to identify specific targets of the stress response protein SIRT1 that are relevant to the survival of neurons in individuals with motor neurone disease (MND).

The ability to cope with stress is a fundamental aspect of cell survival. Stresses such as protein misfolding, oxidative stress, inflammation and dysfunctional mitochondrial metabolism occur normally during the aging of a cell, but are abnormally accelerated in MND.

SIRT1 is a key mediator of stress responses and has been shown to be upregulated in neurons. However little is known about its expression in neighbouring astrocytes, which play a critical role in signalling to neurons to keep them alive.

Dr Melanie McConnell's Cell Survival Group is addressing this question by treating normal astrocyte cells with stresses that induce a MND phenotype, before and after SIRT1 activation. Careful examination of the precise effects of SIRT1 activation in these cells will aid in the development of approaches to reduce or prevent neurodegeneration.