THE REGULATORY MECHANISM OF HAEM OXYGENASE PROTECTION AGAINST PHOTOIMMUNOSUPPRESSION AND SKIN CANCER
Funder
National Health and Medical Research Council
Funding Amount
$439,500.00
Summary
Current dogma holds that UVA radiation adds to UVB damage in the skin. However we have identified a window of UVA doses, easily achievable from daytime sunlight exposure, that do not cause sunburn and are not immunosuppressive, but that significantly attenuate the damaging effects of UVB. In mice the mechanism partially depends on the UVA-upregulated cytokine interferon-gamma, and strongly on the UVA-inducible antioxidant enzyme haem oxygenase-1 (HO-1). This project aims to establish how the HO- ....Current dogma holds that UVA radiation adds to UVB damage in the skin. However we have identified a window of UVA doses, easily achievable from daytime sunlight exposure, that do not cause sunburn and are not immunosuppressive, but that significantly attenuate the damaging effects of UVB. In mice the mechanism partially depends on the UVA-upregulated cytokine interferon-gamma, and strongly on the UVA-inducible antioxidant enzyme haem oxygenase-1 (HO-1). This project aims to establish how the HO-1 gene is regulated by UVA. Available data from cultured human skin cells suggest that HO-1 is UVA-inducible in fibroblasts but not keratinocytes, whereas we found both cell types respond in mouse skin, keratinocytes most actively. We will ascertain whether a species difference, or an anomaly in cultured cells, underlies these discrepancies. With human skin grafted onto immunodeficient SCID mice, we will study impaired immune function, an important prerequisite for cancer, compared with mouse skin in vivo. Using molecular biology techniques with this model, we will monitor the activity of the transcription factor Bach 1, known to bind to the DNA of the HO-1 promoter region to repress the gene normally, but reversibly by haem-binding, and the corresponding activity of HO-1, during immunoprotective (UVA exposure, haem elevated) conditions. Immunoprotection may result from binding by Bach 1 of haem released from microsomal proteins by UVA, its release from DNA and thus derepression of HO-1. We will seek evidence of a role for skin cytokines in modifying Bach 1 binding, and for Bach 1 and HO-1 actions during photocarcinogenesis induction with chronic UV exposure. The significance of the outcome of the studies will be in understanding how a natural ameliorating pathway induced by UVA radiation could be utilised for superior photoprotection strategies for skin cancer susceptible humans.Read moreRead less
Characterisation Of The Anti-apoptotic Function Of P-glycoprotein And Transcriptional Regulation Of The MDR1 Gene.
Funder
National Health and Medical Research Council
Funding Amount
$469,500.00
Summary
The ability of tumor cells to survive treatment by chemotherapy is a major obstacle in curing patients with cancer. One mechanism by which cancer cells become multidrug resistant (MDR) is their acquired expression of a protein called P-glycoprotein (P-gp) that extrudes cytotoxic drugs out of the cancer cell. We have defined a novel role for P-gp in protecting cells against death induced by non-drug stimuli, where an efflux effect of P-gp would have no obvious benefit. This broader survival effec ....The ability of tumor cells to survive treatment by chemotherapy is a major obstacle in curing patients with cancer. One mechanism by which cancer cells become multidrug resistant (MDR) is their acquired expression of a protein called P-glycoprotein (P-gp) that extrudes cytotoxic drugs out of the cancer cell. We have defined a novel role for P-gp in protecting cells against death induced by non-drug stimuli, where an efflux effect of P-gp would have no obvious benefit. This broader survival effect of P-gp may be explained by its ability to regulate the activity of key enzymes (caspases) that exist within cells to induce cell suicide when appropriate. Many chemotherapeutic drugs activate caspases to kill target cells and as P-gp can inhibit caspase activation, it is therefore possible that P-gp affects the activity of anti-cancer drugs by both removing the drugs from the target cells and inhibiting the pathways through which the drugs can kill a cell. We have mutated P-gp to define the region that is necessary for its caspase regulatory function. We are now identifying the proteins that bind to this region so that we can determine how P-gp regulates caspase activation. In addition, we have defined the manner by which P-gp expression is kept low in normal cells and is upregulated following exposure of cells to chemotherapeutic drugs. The gene encoding P-gp (MDR1) is normally switched off due to the way it is packaged within a nuclear structure called chromatin. We have shown that treatment of cancer cell lines with chemotherapeutic drugs alters chromatin in such a way that the MDR1 gene is activated. We will identify the proteins and complexes involved in drug-mediated regulation of chromatin structure and determine if this phenomenon occurs within patients receiving chemotherapy. Our new findings may lead to novel treatment options for patients that have MDR cancers and may provide insight into possible new ways to inhibit the formation of P-gp-expressing MDR tumors.Read moreRead less
Mechanisms Of Action Of The Zinc Finger Protein LMO4 In Breast Oncogenesis
Funder
National Health and Medical Research Council
Funding Amount
$272,859.00
Summary
Breast cancer is the most common cancer to strike Australian women, affecting one in 12 women by age 75. Although treatment of breast cancer has substanially improved over the last few years, approximately 25% of women diagnosed with this cancer will die from the disease. A major objective of cancer research is the identification of genes involved in tumour development and definition of their precise role in both normal and cancer cells. The design of new effective therapeutic inhibitors of canc ....Breast cancer is the most common cancer to strike Australian women, affecting one in 12 women by age 75. Although treatment of breast cancer has substanially improved over the last few years, approximately 25% of women diagnosed with this cancer will die from the disease. A major objective of cancer research is the identification of genes involved in tumour development and definition of their precise role in both normal and cancer cells. The design of new effective therapeutic inhibitors of cancer requires an understanding of the basic molecular and cellular biology behind the genetic changes that contribute to cancer. The focus of our research is to understand normal cellular mechanisms that drive growth and differentiation of breast tissue, and those changes that lead to breast cancer. We are particularly interested in 'master regulators' that are located in the cell nucleus. Nuclear regulators have been implicated in many different types of cancer and leukaemias. We aim to identify the key regulators in breast tissue, characterising both their biological roles and mechanism of action, with the ultimate view of understanding how they divert a normal cell to a cancerous cell. This proposal centres on the characterisation of a specific nuclear regulatory molecule, LMO4, which we have demonstrated to be overexpressed in 56% of human primary breast cancers. Significantly, we have recently shown that overexpression of LMO4 predicts poor outcome in breast cancer patients. We have also shown that this protein interacts with the breast tumour suppressor protein BRCA1, as well as a number of other proteins. These studies will include defining LMO4 s role in governing cell growth in breast cancer cells and that of the proteins that bind to this regulator. We will also assess the role of LMO4 in controlling cell invasion and metastasis of breast cancer cells in mouse models since we have preliminary evidence that it may be a critical regulator of these processes.Read moreRead less
Analysis Of The Interaction Of The T-cell Oncoproteins Scl And Lmo2 In T Cell Acute Lymphoblastic Leukaemia
Funder
National Health and Medical Research Council
Funding Amount
$179,149.00
Summary
Leukaemic cells frequently contain alterations to the chromosomes which contribute to the generation of the leukaemia by causing the expression of cancer-promoting genes. In the case of T cell acute lymphoblastic leukaemia (T-ALL), the most frequent target of chromosomal alterations is the Stem Cell Leukaemia gene, or SCL. In leukaemic cells, the SCL protein is found to be associated with another protein, called Lmo2, the gene for which is also activated due to chromosomal alterations in T-ALL. ....Leukaemic cells frequently contain alterations to the chromosomes which contribute to the generation of the leukaemia by causing the expression of cancer-promoting genes. In the case of T cell acute lymphoblastic leukaemia (T-ALL), the most frequent target of chromosomal alterations is the Stem Cell Leukaemia gene, or SCL. In leukaemic cells, the SCL protein is found to be associated with another protein, called Lmo2, the gene for which is also activated due to chromosomal alterations in T-ALL. It is thought that these two proteins must bind each other to cause leukaemia, but this has never been proven. This project aims to test whether removal of SCL and Lmo2 is able to stop the progress of leukaemias which they initiate. We will do this by overexpressing SCL and Lmo2 to establish leukaemia in mice, then removing these genes to see if the leukaemia is cured. We will then test whether removal of the endogenous SCL protein is able to stop the onset and progress of leukaemias initiated by Lmo2. We will do this by removing SCL in mice which overexpress Lmo2. Lastly we will generate mutant SCL proteins which are unable to interact with Lmo2, and co-express these along with Lmo2 in mice to assess whether they are able to co-operate with Lmo2 in causing leukaemia. We predict these mutants which are unable to bind to Lmo2 will be unable to co-operate with it in causing leukaemia. This will identify regions of these proteins which can be used as targets for anti-leukaemia drug development.Read moreRead less