A novel role for nuclear EGFR in breast cancer progression and therapeutic resistance

Breast cancer is a major public health problem worldwide. In the United States alone, 178,480 new cases of breast cancer and 40,910 breast cancer deaths were expected in 2007. This unequivocally makes breast cancer the most common cancer in Western women, and second only to lung cancer in terms of cancer morbidity. Alarmingly, the incidence of breast cancer continues to rise with enormous physical, psychological, and social effects on the women who are faced with cancer diagnosis and treatment. During the last decade, great strides have been made in reducing breast cancer morbidity through increased mammography screening coupled with the advent of multi-agent chemotherapy and Tamoxifen. However, treatment of basal-like breast cancer (BLBC) remains especially challenging as these tumours lack the estrogen, progesterone, and HER2 receptors targeted by many traditional chemotherapeutic drugs. Moreover, the tumours readily develop resistance to new generation chemotherapeutic agents, such as Iressa. Further studies are desperately needed to uncover novel signalling cascades responsible for cancer progression that could ultimately be manipulated to combat this highly aggressive subset of breast cancer. The surface of cells are coated with receptors that “listen” to cues from the surrounding environment to direct cells to proliferate, synthesize and excrete proteins, or even undergo apoptosis (cell death). Traditionally, it was believed that these signals were sent to the cell nucleus exclusively through complex and elaborate cascades of intracellular messengers. However, it has recently emerged that cell receptors can become internalized and trafficked to the nucleus where they can act as transcription factors – in essence proteins that can turn on and off particular genes. This novel pathway has tremendous consequences for cancer biology as it offers a novel mechanism which cancerous cells could be exploiting to proliferate, metastasize (spread to other sites), to even combat the effects of chemotherapy. I have recently demonstrated that a fragment of the epidermal growth factor receptor (EGFR) translocates from the cell surface to the nucleus in BLBC cells. This is an exciting finding because EGFR is overexpressed in 50% of BLBCs, but more importantly, it could explain why these cells are resistant to Iressa, a chemotherapeutic that inhibits EGFR from sending messages via signal transduction cascades. Specifically, a fragment of the receptor could be cleaved to directly activate pro-survival genes in the nucleus. My research proposal is focused on gaining a more in depth understanding of this novel, cleaved form of EGFR, known as nuclear EGFR. Specifically, I am interested in determining the structure of nuclear EGFR and uncovering if it interacts with other proteins in the nucleus. In addition, I want to discover the specific pro-survival genes that are being induced by nuclear EGFR. This work will determine if targeting nuclear EGFR represents a viable strategy for combating cell proliferation, metastasis, and therapeutic resistance in a subset of cancer where treatment options are currently limited.

The role of toll-like receptors in autoimmunity in non-obese diabetic mice

More than 180 million people worldwide have either type 1 or type 2 diabetes. People with this condition are unable to maintain normal blood sugar levels due to a lack of, or insensitivity to, insulin, a hormone that regulates blood sugar levels. Whereas type 2 diabetes is usually caused by eating an unhealthy diet, type 1 diabetes is an autoimmune disease in which the affected person’s own immune system destroys the insulin-producing islet cells in the pancreas. Research shows that killer T cells (immune cells that normally attack virus-infected cells) cause type 1 diabetes by destroying islet cells. However, there has been little research completed to date regarding what causes T cells to attack the body’s cells. It has been hypothesized that sensors that recognize microbes like bacteria and viruses, called TLRs (toll-like receptors), may play a role. TLRs activate the immune system to fight off microbes; however, TLRs are also suspected of playing a role in the onset of type 1 diabetes. Andrew Lee is investigating whether a group of TLRs activate or accelerate the destruction of healthy cells in autoimmune diseases. Lee will also determine whether older, anti-malaria drugs and new designer DNA drugs can block these TLRs. Since symptoms of type 1 diabetes only appear when the pancreas is irreversibly damaged, this research could be used to identify people at risk of developing type 1 diabetes, and lead to new ways of preventing and treating the disease.

Autism Spectrum Disorders: Identification of Novel Microdeletion and Microduplication Syndromes and Clinical Endophenotypes

Autism spectrum disorders (ASDs) affect more than one in 250 people and are characterized by significant impairments in social interactions and communication as well as inappropriately focused behaviours and restricted interests. Research involving sibling, twin and family studies has revealed the predominant role of genetic factors in ASDs and also identified regions in chromosomes where genes conveying susceptibility to ASDs might be located. Furthermore, recent studies have shown that chromosome anomalies can be found in five to 28 per cent of persons with ASDs, depending on whether they have cognitive delay and/or physical anomalies. Noemie Riendeau is exploring the genomic changes and molecular genetics underlying ASDs, as well as their clinical presentation and associated genomic syndromes. She is using a genome screening method known as Comparative Genomic Hybridization (array-CGH) to detect small chromosomal imbalances called microdeletions and microduplications in people with autism. The hope is that identifying these imbalances will help pinpoint genomic regions where genes associated with Autism Spectrum Disorders (ASDs) are located. The research also investigates how these genomic changes correlate with the clinical phenotypes of the patients, especially those with dysmorphic features and/or intellectual disability, but also for those cases described as simple autism. By defining new microdeletion and microduplication syndromes, this research will contribute to a better understanding of the genetic basis of ASDs and potentially to improved methods for early detection and treatment.

Mechanism of Histone Variant H2A.Z Deposition by SWR1-Com

DNA, which is packaged into highly condensed structures in the cell, carries genetic information that is passed from one generation to the next. Chromatin is the first level of DNA packaging that eventually results in the formation of chromosomes – threadlike parts of a cell that carry hereditary information in the form of genes. Many debilitating and life-threatening diseases, such as cancer, neurodegenerative diseases including Alzheimer’s and Huntington’s, and inherited childhood syndromes, result not only from changes in the basic DNA sequence, but also from changes in the structure of chromatin. DNA is condensed into chromatin with the help of DNA-packaging proteins called histones. DNA wraps around eight core histones – two each of H2A, H2B, H3, and H4 – to assemble into chromatin. H2A.Z is a variant of the core histone H2A that is conserved through evolution. Structurally, H2A.Z is different toward the end of the protein. A large protein complex called SWR1-Com, which binds to H2A.Z but doesn’t bind H2A, deposits H2A.Z into chromatin. Alice Wang is researching the differences between the way H2A.Z and H2A are deposited into chromatin. She is specifically investigating whether the difference between H2A and H2A.Z lies in their different binding capabilities to SWR1-Com. The findings will help increase understanding of H2A.Z biology and how chromosomal neighbourhoods containing H2A.Z are made. Wang’s ultimate aims for the research is to contribute to development of therapies for diseases that result from changes in chromatin structure.

Palmitoylation in the Pathogenesis of Huntington Disease

Huntington disease (HD) is a devastating inherited neurological disease characterized by loss of motor control, cognitive decline and psychiatric disturbances, resulting in eventual death 15 to 20 years after symptoms first appear. In Canada, one in 10,000 people have Huntington disease, and have a 50 per cent risk of passing on the disease to their children. The underlying genetic cause of HD is an expansion of a specific portion of the HD gene, known as the CAG trinucleotide repeat, which results in an expanded stretch of an amino acids in the huntingtin protein. This expansion leads to cell death in specific parts of the brain through mechanisms that are the subject of intense investigation. When the HD gene is translated into huntingtin, the protein undergoes alterations at many sites. Palmitoylation is an example of such an alteration, which involves the addition of a small fatty-acid chain to a protein. Palmitoylation enhances the ability of a protein to associate with membranes (e.g. cell walls), and influences that protein’s trafficking and function. Most notably, palmitoylation is a reversible protein modification. Decreased palmitoylation may play a role in the cellular events underlying the development of HD. Fiona Young is investigating the role of palmitoylation in the development of Huntington Disease as well as in the context of the normal function of the huntingtin protein. The research could lead to new therapeutic approaches for Huntington disease that involve increasing palmitoylation of the huntingtin protein.

An investigation of the basis of aminoglycoside resistance in the Burkholderia cepacia complex

Cystic fibrosis and chronic granulomatous disease are both life-threatening genetic disorders. Cystic fibrosis is the most common life-shortening genetic disorder affecting Caucasians, with the median survival age being only about 37 years in North America. A genetic mutation results in the buildup of sticky, dehydrated mucus in the airways of the lungs, leading to an inability to clear many microorganisms. The resulting persistent infections gradually destroy lung function. Individuals with chronic granulomatous disease are also susceptible to chronic bacterial and other infections, because a genetic mutation impairs the protective functions of certain immune cells, causing them to be unable to effectively kill infectious organisms. A group of bacteria that commonly cause severe and fatal infections in these patients is the Burkholderia cepacia complex (BCC). These bacteria represent a significant threat because they are highly resistant to many antimicrobial drugs. Recently, researchers in Agatha Jassem’s lab discovered B. vietnamiensis bacteria, a member of the BCC, which are sensitive to a particular group of antibiotics called aminoglycosides. This presents an opportunity to undertake comparative studies between drug resistant and susceptible strains of the BBC. Jassem believes the outer cell wall permeability of the newly discovered B. vietnamiensis bacteria may be responsible for its susceptibility to the aminoglycosides group of antibiotics. To establish this, she is first evaluating the level of resistance of the B. vietnamiensis bacteria to a variety of antibiotics. Then, she is carrying out molecular studies of the outer cell wall of these bacteria to clarify the mechanisms that affect their permeability and thus their susceptibility or resistance to antibiotics. Ultimately, Jassem hopes her research will lead to the development of new therapies for treatment in cystic fibrosis and chronic granulomatous disease.

Characterizing the Molecular Mechanisms of Adaptor Proteins AP-3 and AP-1B Function: An Integrated Analysis

The cell consists of many different compartments, each of which carries out a special function. A network of transport pathways moves molecules between these compartments to reach their proper location. This process, called vesicular transport, is central to the cell’s ability to grow, divide and communicate with its external environment. Receptors are dependent on vesicular transport for reaching the cell surface, where they bind factors that are essential for the cell such as hormones and nutrients. An enormous number of human diseases, including cancer, diabetes and Alzheimer’s disease, result from defects in vesicular transport. A specialized group of proteins called adaptors coordinate the wide variety of transport events within the cell. Each adaptor recognizes its own set of molecules for transport and initiates the pathway that will take them to their final destination. Adaptors cannot work by themselves; many regulators cooperate with these complexes, guiding them to the correct location and activating them for cargo binding. Helen Burston is identifying the molecules that cooperate with Adaptor Protein Complex 3 (AP-3), an adaptor required for the formation and function of lysosomes, which are required for immunity, blood clotting, and brain function. This research will help develop a better understanding of defects in neurological function and immunity.

The role of imprinting in placentation and obstetrical complications

Up to one per cent of pregnancies in British Columbia end in stillbirth. Two conditions thought to contribute to the rate of stillbirths are pre-eclampsia and intrauterine growth restriction (IUGR). Pre-eclampsia – a form of pregnancy-induced high blood pressure – affects approximately five per cent of pregnancies, and can be life-threatening to both mother and fetus. IUGR – where the fetus is significantly undersized for its gestational age – also affects approximately five per cent of pregnancies, and is linked to health problems at birth and beyond. Abnormal placental development is thought to be responsible for many complications of pregnancy, including pre-eclampsia and IUGR. The causes underlying abnormal placental development are largely unknown. It may involve errors in DNA methylation, a mechanism used to regulate the activity of certain genes – particularly imprinted genes. Unlike the more common type of genetic inheritance where the outcome in the offspring will depend on whether a gene is dominant or recessive, imprinted genes are parent-of-origin-specific, meaning they are only expressed from either the maternal or paternal chromosome. The placenta has an overabundance of genes expressed in this way. Errors in DNA methylation and imprinting can result in changes in gene expression. Danielle Bourque’s project aims to determine if disruption of normal DNA methylation and imprinted gene expression leads to the abnormal placental development associated with pre-eclampsia or IUGR. The eventual goal is to develop a strategy to improve early diagnosis of pre-eclampsia and IUGR, which will lead to improved treatments and outcomes for both mother and baby.

Mechanisms of topical calcipotriol mediated tolerance induction

Autoimmune diseases such as type 1 diabetes, lupus, and multiple sclerosis are a serious health issue in North America, affecting more than 22 million people in the US alone. Unfortunately, current treatment options for individuals suffering from autoimmunity are limited, and patients are often faced with the prospect of life-long drug regimens designed to suppress their immune systems. While effectively managing autoimmune diseases, these drugs can also hamper the body’s ability to defend itself against infection and cancer, substantially reducing a patient’s quality of life. T regulatory cells (Tregs) are a class of immune cell that prevent the immune system from attacking the body. Because Tregs can prevent autoimmune disease, many attempts have been made at designing methods to generate them. As of yet, no practical and reliable means of producing Tregs has been achieved. Previous research demonstrates that Vitamin D may play a role in the Treg production process. Paxton Bach is investigating whether applying Vitamin D to the skin can be used to generate Tregs, and early results are promising. Ultimately, this research could lead to more effective, less invasive treatments for individuals living with autoimmune diseases around the world.

Functional characterization of the chorea-acanthocytosis gene VPS13A in the yeast Saccharomyces cerevisiae

Many diseases such as cancer, atherosclerosis (narrowing and hardening of the arteries) and neurodegenerative disorders stem from problems with the uptake, transportation, storage and recycling of molecules. Proper sorting is necessary for normal cell function since many molecules are only required in specific areas or compartments of the cell. In the case of neurodegenerative disorders, defective protein sorting in nerve cells can lead to brain tissue deterioration. Disease caused by abnormal protein sorting can be studied in very simple organisms such as yeast, and the findings directly applied to human cells. Dr. Leslie Grad is researching a yeast protein, Vps13, which is very similar to a protein encoded by the human gene VPS13A. Defects in this gene can lead to chorea acanthocytosis, a neurodegenerative disorder associated with abnormal red blood cells, epilepsy, and muscle and nerve cell degradation leading to premature death. The findings could provide insight into the complicated mechanisms that regulate sorting of molecules inside cells and explain the molecular function of Vps13. Ultimately, Dr. Grad hopes to apply his findings to human cells and contribute to the development of therapies for neurological disorders caused by abnormal protein sorting.