One of the main characteristics of cancer is the uncontrolled division and growth of cells. Because tumour cells divide very frequently, tumour growth can be selectively stopped by inhibiting cell division. Commonly-used cancer drugs act by effectively âfreezingâ cell activity right in the process of division. This is done by interfering with mitosis â the point in the cell cycle where the nuclear chromosomes have been duplicated and separated to form two daughter cells. Unlike normal cells, some cancer cells eventually bypass this frozen state in a process known as mitotic slippage. However, the resulting cells now contain too many sets of chromosomes. Researchers still donât know what happens to these drug-treated cancer cells as a result of mitotic slippage â whether they are able to start dividing again, whether they remain in an arrested state indefinitely, or whether they die. Jenna Riffell is investigating the fate of cancer cells after drug treatment. She is identifying chemical compounds that can stimulate drug-treated cancer cells to undergo mitotic slippage, and monitoring what happens to these cells. Her hypothesis is that the rate of mitotic slippage can be increased with chemicals, and will prompt growth arrest or cell death. If proven successful, this approach could be used for the development of future cancer therapies. In addition, Riffellâs work will be useful for studying the underlying biochemical mechanisms of cell division.
Program: Trainee
RNA interference analysis of human embryonic stem cells in a microfluidic device
Embryonic stem cells (ESCs) are considered the pinnacle stem cell due to their unlimited capacity to self-renew. Since ESCs can differentiate to produce precursors to almost all types of cells (pluripotency), they may hold the key to curing diseases that are caused by the loss of function among specific cell types such as Parkinsonâs disease, Alzheimerâs disease, spinal cord injuries, and type 1 diabetes. In order to understand differentiation and self-renewal, researchers compare gene activity between ESCs that have undergone differentiation and those that have not. Scientists can also intentionally turn off (silence) specific genes to see if there is an effect on cell pluripotency. Conventional techniques are time consuming and only allow for the analysis of large numbers of cells at any given time. The cells in these populations are rarely homogeneous as the environments around them are not precisely controlled. To address these issues, researchers have developed a cutting edge technology called microfluidics. Microfluidic technology involves constructing small chips with thousands of fluid-filled chambers that can each contain a single cell. This reduces the number of cells used and the cost of each experiment, and allows thousands of experiments to be performed on a single chip simultaneously. Darek Sikorski is constructing a microfluidic device for the purpose of sustaining and examining the behaviour of ESCs. Once validated, this will allow for large-scale experiments to be performed where specific genes are silenced in each cell, allowing for the analysis of thousands of genes at once. This technology has the potential to greatly accelerate research into how ESCs grow, communicate and differentiate. Ultimately, this could lead to ways to use ESC lines to produce specialized tissues that can cure certain diseases.
YB-1 is associated with breast cancer relapse because it induces tumour-initiating cells
In 2007, an estimated 22,300 Canadian women were diagnosed with breast cancer, and 5,300 women died of the disease. To kill cancer cells, breast cancer patients undergo combinations of surgery, drug therapies, chemotherapy, and radiation. In spite of these aggressive treatments, certain cancer cells may not be completely eradicated and tumours may start growing again (relapse). In the event of breast cancer relapse, the prognosis is generally much worse than it was at the initial onset of the disease, and available drugs eventually become ineffective. It has been discovered that in breast cancer, only a small group of cells â called breast cancer tumour-initiating cells â can keep growing for a long period of time, while the other “”regular”” cancer cells cannot sustain themselves long term. With a better understanding of these aggressive tumour-initiating cells, researchers could design new drugs that target this special group of cells, and focus less on the cancer cells that will eventually stop growing on their own. Preliminary evidence suggests that tumour-initiating cells require a protein called YB-1 in order to grow and form tumours. Studies also show that patients whose breast cancers produce YB-1 have a higher chance of relapsing. Karen To is investigating whether she can stop the growth of tumour-initiating cells by blocking the production of YB-1. If this particular factor is proven essential for the growth of the tumour-initiating cells, drugs could then be designed to remove this protein. Toâs research will contribute to the understanding of the small group of breast cancer cells responsible for maintaining tumour growth. Ultimately, this knowledge could lead to improved ways to treat this devastating disease.
Cross-species characterization of proteins involved in genomic stability
Cell division is required for the development, growth, renewal and repair of all organisms, including humans. During cell division, the cellâs genomic information â stored in the chromosomes â is replicated (copied) so that each of the resulting daughter cells receives a complete set of genetic material. Proper segregation of chromosomes to daughter cells during cell division is critical to their continued survival, and chromosome missegregation has been observed in a majority of cancers. However, the connection between the increased rate of chromosome missegregation observed in cancer, and the development of the cancer itself, remains unclear. Because chromosome segregation is a fundamental mechanism in all organisms, bakerâs yeast can be used as a model to study this process. Many yeast genes and proteins involved in chromosome segregation appear to be conserved across evolution between yeast and humans. One such protein in yeast is Ctf4, which has a human counterpart called Wdhd1. Ctf4 plays a critical role in ensuring faithful chromosome segregation during cell division, though its biochemical function is not fully understood. The yeast CTF4 gene also appears to interact genetically with a number of yeast genes whose human counterparts are known to be mutated in cancer. Derek van Pel is further characterizing both the human and yeast proteins’ roles in this chromosome segregation. He is using biochemical techniques to isolate any other proteins within the cell with which these proteins interact. Such interactions will then offer clues to the function of these proteins. Derekâs research will shed light on the role of Ctf4/Wdhd1 in ensuring proper chromosome segregation, and possibly the role of this process in cancer development. Understanding these genetic interactions may also lead directly to new therapeutic avenues for cancer.
Microfluidic instrumentation for microRNA expression profiling in hematopoietic stem cells
MicroRNAs (miRNAs) are small RNA molecules that regulate the expression (activation) of genes. Recent studies of miRNA expression implicate these molecules in early development, brain development, cell proliferation and cell death. They are also implicated in disease states, such as chronic lymphocytic leukemia. Determining how, when, and where miRNAs are produced and function in cells and tissues would have profound impact on medical disciplines ranging from embryology to cancer diagnosis and therapy. The genes expressed in miRNA differ between developing and mature tissues, and comparing normal tissues to tumour tissues also reveals different miRNA expression profiles. Further studies looking at differentially expressed miRNAs could help identify those miRNAs involved in human cancer development. Unfortunately, traditional expression profiling techniques are laborious, costly, slow, or lack the sensitivity to effectively screen populations of cells and quantify miRNA content. A promising approach to overcome these limitations is the use of microfluidics technology. This technology involves constructing small chips with thousands of fluid-filled chambers, which can each contain a single cell. This reduces the number of cells used and the cost of each experiment, and allows thousands of experiments to be performed on a single chip simultaneously. Adam White is developing a microfluidic device capable of inexpensive miRNA expression profiling of many single cells at the same time. Upon successful development of this new microfluidic tool, he will work with other scientists to look for differentially expressed miRNAs in blood related cancers such as acute myeloid leukemia. The development of a microfluidic device for single cell analysis of miRNA would greatly accelerate the identification of those miRNAs involved in cancer development, and ultimately improve methods of cancer diagnosis and treatment.
Improved characterization of orthologs to facilitate cross-species analysis of innate immune system gene responses
The innate immune system is the body’s first line of defense to protect us from disease-causing microbes in our environment. However, the innate immune system can also generate other unintended and serious effects such as prolonged â and sometimes fatal â inflammation. The study of human systems such as the innate immune system is assisted by examining similar systems in other organisms, known as model organisms. Researchers link equivalent genes in the model organism to human genes, so that knowledge can be transferred from the model organism to humans. However, identifying equivalent genes between species can be a difficult task. The Brinkman laboratory at Simon Fraser University has developed a software program called Ortholuge that can detect pairs of genes that are likely to be âorthologsâ â genes in different species that are similar to each other because they originated from a common ancestor. Orthologs are of significant interest when inferring function in humans based on different species, or when linking equivalent genes between species for large scale comparative analyses. Matthew Whiteside is working to improve the accuracy and speed of Ortholuge, adding functionality to the program that will resolve some of the more complex gene relationships. He will then use the software to perform a large-scale study of the innate immune system in humans, mice and animals important in agriculture, such as cattle. Whitesideâs work will be the first large-scale cross-species comparative analysis of the innate immune system. He hopes that this study will provide fundamental new insights regarding the evolution of innate immune system. This analysis may also highlight important innate immunity genes that are conserved between the species, with potential for identifying new therapeutic targets for immune diseases.
Protein tyrosine phosphatase A (PtpA) dependent mycobacterial manipulation of host response to infection
Tuberculosis (TB) is currently the worldâs leading cause of mortality due to a single infectious agent. It has been estimated that approximately one-third of the worldâs population is infected with Mycobacterium tuberculosis, the bacteria that causes TB. Approximately two million people die of TB annually, and about eight million new cases arise each year. In addition to the emergence of multi-drug resistant strains of the disease, TB develops much more readily in people with HIV infection, and is a leading cause of AIDS-related death. There is an urgent need for novel therapeutics and drug targets in order to control the global spread of TB. In order to evade attack by the host immune system, M. tuberculosis secretes a protein called Protein tyrosine phosphatase A (PtpA). PtpA interacts with multiple proteins in the host that are normally essential for the destruction of bacterial pathogens. However, the exact role of these interactions in relation to the survival of M. tuberculosis within cells is not yet completely understood. Dennis Wong is defining the role of TB-Host interactions and identifying the molecular events that are disrupted by PtpA to promote TB infection. Understanding the mechanisms by which PtpA promotes the survival of M. tuberculosis will provide important insights regarding the pathogenesis of TB and the response of the host immune system to infections. As PtpA is a potential drug target, the new knowledge may contribute to the development of novel therapeutics against one of the deadliest diseases in the world.
The mechanism of U4/U6 Di-small nuclear ribonucleoprotein formation: a modification/interference analysis
Proteins, the molecules that carry out many cellular functions, are synthesized according to information contained in DNA sequences. Converting information from DNA into a protein requires an intermediate step in which the DNA sequence is copied into a molecule called RNA. In humans there is an essential biochemical process called RNA splicing, in which non-coding portions of the sequence are removed and the remaining protein-coding portions are joined together to form a template for protein synthesis. Ninety percent of human genes are subject to splicing, so it is not surprising that errors in this process have been linked to a wide array of diseases, including retinitis pigmentosa, spinal muscular atrophy, cystic fibrosis, myotonic dystrophy, Alzheimer’s disease and cancer. Splicing is catalyzed by the spliceosome, a large and dynamic complex that consists primarily of five small nuclear ribonucleoproteins (snRNPs) designated U1, U2, U4, U5, and U6. During spliceosome assembly, the snRNPs interact with each other in a step-wise, ordered way. One of the first steps in assembly involves U4 and U6 pairing to form a particle called the U4/U6 di-snRNP. Although the di-snRNP complex is essential for spliceosome assembly and function, the mechanism by which it forms is poorly understood. Tara Wong is investigating the process by which U4 and U6 undergo essential conformational changes necessary for spliceosome assembly. She is using chemical modification/interference experiments to determine how free U4 and free U6 snRNPs interact to form the U4/U6 di-snRNP. This knowledge will be fundamental to understanding spliceosome assembly and function, and should ultimately lead to a better understanding, and treatment of splicing related diseases.
The immunomodulatory effects of host defence peptides on dendritic cells
Modern day vaccines are effective at preventing infections such as tetanus, influenza, polio and many others. To ensure full protection from illness, some vaccines require more than one immunization. This is commonly known as a booster shot. In developed countries, getting vaccinated usually means nothing more than going to the clinic. In developing countries the process is not so straight forward. Limited access to, and availability of vaccines makes widespread immunization a difficult process. The fact that people may have to return for a booster shot only compounds the problem. For all of the above reasons, there is clearly a need for improved vaccines in developing countries. Our laboratory is studying ways to create effective single-dose neonatal vaccines for developing countries. This means the vaccine would be given shortly after birth, and there is no need for a booster shot to ensure complete protection. Such a vaccine would alleviate the previously described difficulties. Specifically, our lab is developing more effective vaccine adjuvants. An adjuvant is simply any component added to a vaccine that will interact with the immune system to improve protection. We believe that a class of proteins known as host defence peptides (HDPs) will act as effective vaccine adjuvants. HDPs are short proteins, found almost ubiquitously in nature (microorganisms, insects, plants and mammals for example). Historically, the function of HDPs has been primarily to kill invading bacteria and viruses. Recent research conclusively shows that some HDPs are capable of altering the way in which immune system responds to an infection. My research will focus on how HDPs interact with and important type of immune cell known as a dendritic cell. Dendritic cells (DCs) circulate in the body in an “”immature”” form. When they encounter anything foreign (for example, bacteria or viruses), they become “”activated,”” capture the invader, and alert the immune system so it can mount a full response. They are now said to be “”mature.”” For this reason, DCs are a very unique type of cell. They are part of the front line of defence, yet they are also critical in generating the full immune response, which develops shortly after. We believe that HDPs will influence DCs in such a way that they will promote an efficient immune response in the context of vaccination. I hypothesize that HDPs impact DC function, activation, and maturation by altering specific genes and proteins important to DCs. This hypothesis has lead me to develop five goals to guide my research. I will provide an overview of these goals: 1) Bioinformatics. My preliminary experiments have tracked how HDPs influence the expression of 16,000 genes in mouse DCs. Such a large amount of data needs to be handled by a computer. Using specially designed programs, I am able to sort through the vast amounts of data and determine the broad trends occurring in response to HDPs. Furthermore, I am able to look at how small groups of genes behave in the context of their larger gene families; 2) IRAK-4. Results show that one peptide altered the behaviour of an important protein called IRAK-4. IRAK-4 is known to be important for specific immune responses. I will further analyze how this protein functions in the presence and absence of HDPs and other immune stimuli in DCs. I will also determine how proteins related to, and dependent on IRAK-4 will behave in response to HDPs; 3) Lyn Kinase. Another interesting finding was the altered production of Lyn, another protein important for proper DC function. I will continue analyzing the behaviour of Lyn in DCs in response to HDPs. I will also study the consequences of Lyn deficiency and determine its effects on HDP function. 4) DC Type. There are different types of DCs depending on where in the body you look, each performing similar, yet distinct functions. Currently it is not known how different types of DCs respond to HDPs. A lot of DC research is done with mouse DCs because they are relatively easy to generate compared to their human counterparts. The comparative responses of human and mouse DCs to HDPs are not well understood. For these reasons, I will be experimenting in multiple DC types, and in both human and mouse DCs. 5) In vivo peptide effects. Using the previously described experiments as a guide, I will examine how HDPs affect whole mice. We have access to mice deficient in all of the genes listed above, and this will be useful in determining the role of specific genes on the scale of a whole animal. At the completion of this project, I will have gained a comprehensive understanding of how HDPs influence DCs, with the goal of using this information to provide better vaccine adjuvant candidates aimed at developing countries.
Vascular dysfunction of the arteries in a mouse model of Marfan syndrome
Marfan syndrome is an inherited disorder of the connective tissue that causes abnormalities of the eyes, cardiovascular system, and musculoskeletal system. Its most serious and deadly complication is ballooning and rupture of the aorta, the major blood vessel that carries blood from the heart to the arteries and organs. The syndrome is caused by a defect in the gene that makes fibrillin-1 protein. Fibrillin-1 is essential in the formation of elastic fibres in arteries and in maintaining the functional and structural integrity of blood vesselsâ endothelial and smooth muscle cells. Defects in this gene result in abnormalities in the way vessels contract and relax, increasing the susceptibility to ballooning and rupture of the aorta. Huei-Hsin Clarice Yang is studying the effect of Marfan syndrome on endothelial and smooth muscle cells in the aorta and the small arteries. She is expanding on previous research that found that smooth muscle in the Marfan-affected aortas is unable to relax normally. Her work focuses on the mechanisms that contribute to this dysfunction within smooth muscle cells and in the epilethial cells that regulate vascular contraction and relaxation. Yangâs work will provide valuable insight into how Marfan syndrome causes decreased contracting and relaxing abilities of the arteries. Ultimately, this knowledge could lead to innovative therapies to prevent or treat aortic rupture and to halt the vascular deterioration process in patients with Marfan syndrome