Projects

Our current projects are:

► Colorectal Cancer Biomarker Studies and Clinical Trials  - details here
► Cancer Pharmacology and Cachexia - details here
► Do Tumour-Derived Cytokines Repress Drug Clearance in the Liver? - details here
► Ethnic Differences in Drug Clearance - details here
► Cancer Cachexia, Cytokines and Altered Metabolic Pathways? - details here
► Molecular Analysis of Nuclear Receptors PXR, RXR and HNF4 - details here
► Role of PXR in Protecting Cells Against Radiation Damage in Radiotherapy - details here

Colorectal Cancer Biomarker Studies and Clinical Trials

S Clarke, H Dhillon, C Gebbie, L Jankova, J Reid, G Robertson, L Truong, M Tsoli, J Vardy, C Xu, [M Molloy, M Mackay & Baker - APAF; P Chapuis, L Bokey, O Dent, C Chan, C Fung & B Lin - Depts of Surgery & Pathology, CRGH].

In collaboration with the Australian Proteome Analysis Facility, many potential protein biomarkers have been identified that will provide better assays for diagnosis and prognosis as well as help to predict the response of colorectal cancer patients to anti- cancer agents. Such biomarkers will guide the development of individualised treatment regimes which will take into account the variability in efficacy and toxicity to drugs experienced by many cancer patients. In addition some biomarkers will be used to identify patients at risk of developing the muscle wasting associated with the cancer cachexia syndrome. Medium throughput mass spectrometry-based assays have been developed to assess the utility of these proteins before high through-put screening using the Concord Colorectal tissue and data banks collected by Departments of Surgery and Pathology, CRGH. Immuno-staining for the presence of specific proteins in colorectal tumours using tissue microarrays have enabled validation of potential biomarkers for colorectal cancer.

Concord has become a major Australian centre for clinical trials in colorectal cancer patients with particular emphasis on the angiogenesis inhibitor bevacizumab. In nutritional cancer research, we have evaluated the prognostic value of nutritional assessments and demonstrated that patients with advanced colorectal cancer and a poor nutritional status have a shorter survival than well nourished patients. Studies into the cognitive function and fatigue in cancer patients after chemotherapy will be carried out by oncologist Janette Vardy. In psycho-oncology research, among other projects, we are assessing whether education and counselling might improve end of life decision making.

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Cancer Pharmacology and Cachexia

The focus of the cancer pharmacology laboratory is to explain inter-patient differences in response and toxicity to anti-cancer drugs. The treatment of cancer patients with drugs is difficult due to the fine balance between killing tumour cells and causing toxicity to normal cells. Therefore the huge variability between patients in clearance of anti-cancer agents has a significant impact on the success of chemotherapy. Anti-tumour action may be lost if the drug is cleared too rapidly, while slow drug excretion may lead to extreme toxicity. A better understanding of the source of this variability should lead to improvements in the manner in which chemotherapy is administered and would represent a welcome advance for cancer patients. Cancer cachexia is experienced by up to 80% of all cancer patients and involves muscle wasting and depletion of fat reserves. It is directly responsible for the death of 30% of cancer patients. A better understanding of the complex factors responsible for cancer cachexia would help to identify those patients who will be susceptible to developing cachexia as well as better management of this debilitating condition.

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Do Tumour-Derived Cytokines Repress Drug Clearance in the Liver?

S Clarke, M Kacevska, P Polly , A Painter, A Mahns, G Robertson, R Sharma, A Ritau, V Phan, Prof A McLachlan, Faculty of Pharmacy, USyd.

The rate of breakdown and elimination of drugs from the body is largely determined by the levels of enzymes called cytochrome P450s (CYPs) in the liver as well as specific drug transporters which move drugs in and out of cells. In humans CYP3A4 is responsible for the disposal of more than half of all drugs including many important anti-cancer agents. Clinical studies carried out by our group found that CYP3A4 levels are reduced in some cancer patients, leading to greater toxicity. The source of repressed hepatic CYP3A4 levels appears to be linked to tumour-derived cytokines. Therefore a major goal of our research is to study the links between cytokines released by tumours and down- regulation of drug clearance pathways in the liver. Ultimately we hope to be able to predict which patients will suffer toxicity and to develop anti-inflammatory treatments that will normalise drug handling and improve patients’ response to anti-cancer drugs.

As it is difficult to study these processes in the livers of patients, we created a transgenic mouse model of human CYP3A4 regulation. Using these mice we have carried out experiments to analyse the signalling pathways and molecular mechanism involved in mediating the inflammatory response of the liver to tumours. We have found that this process is linked with the growth of several different cancers, including melanoma, breast, colon and sarcoma, indicating that this may be a general feature of many different cancers. In addition to repression of CYP3A metabolism, hepatic drug transporters for several important anti-cancer drugs are also switched off in the presence of cancer, leading to even slower clearance of drugs from the body and greater toxicity. The use of mouse tumour models has enabled us to perform pre-clinical testing of anti-cytokine interventions aimed at normalising drug clearance. In preliminary experiments we have found that using antibodies to IL-6 has partially restored the levels of CYP3A.

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Ethnic Differences in Drug Clearance.

S Clarke, V Phan, A Rittau, C Xu, [Prof A McLachlan – Faculty of Pharmacy, University of Sydney, Prof Micheline Piquette-Miller, University of Toronto]

Compared to Caucasions, cancer patients from an Asian background have greater difficulty tolerating chemotherapy and suffer from more adverse events due to toxicity. Clinical studies are being carried out in breast and lung cancer patients to examine the genetic differences (single nucleotide polymorphism or SNPs) in genes involved in drug metabolism which may be related to altered clearance of anti-cancer drugs. Pharmacokinetic analysis of commonly used chemotherapy drugs such as paclitaxel and doxorubicin are being developed to determine the rate at which they are eliminated from the body. The inter-patient and ethnic differences in drug clearance will be correlated with genetic differences and toxicity.
Cancer Pharmacology Laboratory L to R (top to bottom): Anneliese Rittau, Anthony Corradin, Angie Shum, Michael Evtushenko, Melissa Moore, Stephen Clarke, Graham Robertson, Arran Painter Maria Tsoli, Lucy Jankova, Patsy Polly, Viet Phan, Phillipa Camilleri, Marko Matic, Ryland Taylor, Cathy Xu.

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Cancer Cachexia, Cytokines and Altered Metabolic Pathways?

S Clarke, D Gardon, L Jankova, M Kacevska, P Polly, G Robertson, M Tsoli, R Taylor, A Corradin, M Matic, P Camilleri, A Shum. [M Molloy - APAF; Edna Hardeman - CMRI Westmead; P Glare – Palliative Care, RPAH; F Sladek Uni of California, Riverside]

Cancer cachexia is a complex condition involving disturbances in energy balance and metabolism in several organs of the body. The release of cytokines into the blood by tumours is a likely link between tumour cells and the major metabolic tissues of the body – muscle, fat and liver. Mouse tumour models have been used to study the regulation of metabolic pathways during the development of cachexia. As these pathways are primarily controlled by nuclear receptors, we have profiled the expression of all 50 nuclear receptors, their cofactors and a representative set of their target genes in liver as well as a subset in muscle and fat. This has given valuable insights into the alterations in many metabolic pathways due to the impact of tumour-derived cytokines on nuclear receptor expression. Such changes may contribute to aberrant energy balance leading to cancer cachexia.

The morphology of muscle fibres and fat deposits has been examined to characterise the changes that occur during cachexia. These changes in muscle and fat cells reflect alterations in metabolism and the molecules that control energy balance in the body.

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Molecular Analysis of Nuclear Receptors PXR, RXR and HNF4

A Corradin, A Mahns, M Matic, P Polly, G Robertson, [F Sladek - University of California Riverside]

To understand the regulation of genes involved in drug clearance pathways, we are carrying out detailed molecular studies into the nuclear receptors PXR, its binding partner RXRa and HNF4a. An important step is to identifying which domains of the PXR protein are necessary for interactions with other molecules in liver cells after PXR is activation by drugs. We are especially interested in defining specific interactions with other protein co-factors which move PXR into the nucleus and form the active multi-protein complex required to switch on target genes. Specific modifications of the PXR RXRa and HNF4a proteins, such as phosphorylation, are likely to play a critical role in modulating such interactions with other proteins. We anticipate that this information will help to understand how different diseases which have a marked inflammatory component, such as cancer, impact on nuclear receptors by altering their phosphorylation state.

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Role of PXR in Protecting Cells Against Radiation Damage in Radiotherapy

S Clarke, A Painter, G Robertson, M Tsoli, [M Jackson, N Suchowerska -Radiation Oncology, RPAH]

In addition to direct damage to the genetic material of rapidly dividing cancer cells, radiotherapy can cause damage to other components of both normal and malignant cells such as cell membranes. Cholesterol embedded in membranes can be chemically altered by radiation to forms that can be extremely toxic to cells. The nuclear receptor PXR has evolved to protect cells from such endogenously generated toxic molecules in addition to foreign chemicals. We have investigated the contribution of PXR to the activation of detoxification pathways that may reduce the efficacy of radiotherapy. Activation of PXR with the potent ligand rifampicin enhanced the survival of colon cells exposed to clinically relevant doses of radiation. At the same time several PXR target genes involved in detoxification pathways are induced by radiation. In addition variable levels of PXR was observed in colorectal tumours from different patients. These exciting results indicate that PXR may be involved in tumour response to radiotherapy.

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