Molecular Research in The Department of Surgery
Molecular cancer research is best carried out by a critical mass of high quality biomolecular and biomedical researchers closely affiliated to clinical centres of excellence. This structure has been employed at the Institute of Molecular Medicine at St. James’s Hospital, where a molecular research team has been established under the Dept. Surgery in Cancer translational research laboratories.
The group have a strong interest in the molecular processes regulating the progression to oesophageal cancer. Other cancer types are also being investigated, including lung, colon and breast cancer. There is a particular focus on mechanisms regulating tumour growth in relation to obesity, metabolic syndrome and bioactive lipids. In addition, genomic and proteomic profiling studies are underway, to determine molecular signatures associated with response to treatment of patients undergoing multimodal chemo-radiation therapy.
Active research units within the Dept. Surgery
Obesity and Cancer
The World Cancer Report of 2003, the most comprehensive global assessment of cancer statistics to date, predicts a 50% worldwide increase in cancer incidence by 2020. Although several factors are contributory, the rising incidence of obesity is currently thought to be fuelling cancer rates, and is estimated to currently account for up to 14% of cancer deaths in men and 20% of cancer deaths in women, with this trend predicted to rise. Recent studies estimate that within the next 10-15 years three quarters of our population will be overweight or obese and that obesity will overtake smoking as the number one factor linked with cancer risk. In Ireland, the prevalence of obesity has increased by 67% in the last decade. Currently, 47% of the population are overweight or obese (13% obese, 34% overweight) and it is estimated that obesity rates will continue to rise by at least 1% per annum. Ireland has the fourth highest prevalence of overweight and obesity in men in the EU and the seventh highest prevalence among women. Parallel to this increase, we have seen a dramatic rise in the incidence of several cancers and Ireland has much higher incidence and mortality rates than our European counterparts. Obesity has been identified as a risk factor for many cancers including adenocarcinoma of the oesophagus and lung, colorectal, endometrium, breast (postmenopausal) and kidney (renal cell) cancer. However, the mechanisms by which obesity induces or promotes cancer are not fully understood.
Our research group in the Department of Surgery at St. James’s Hospital recently published the first Irish study on the link between obesity and cancer. We demonstrated that obesity is an independent risk factor for adenocarcinoma of the oesophagus with an 11 fold higher risk for obese versus normal weight individuals.
The aim of this research project is to study adipose (fat) tissue from patients undergoing surgery for oesophageal cancer, to investigate the mechanisms where obesity may contribute to the development and progression of this cancer. Abdominal adipose tissue has been identified as the essential fat source linking obesity and cancer, as it has been shown to produce a wide range of proteins that can lead to a state of chronic inflammation in obese individuals. Research is currently ongoing to examine immune cell populations within the fat, as well those inflammatory cells that leave the fat tissue and circulate in the blood where they may affect a growing tumour. We aim to study proteins made by fat in normal weight patients in comparison to overweight and obese patients, thereby identifying proteins potentially regulating tumour growth and survival. We also aim to examine the tumours of normal weight and obese cancer patients to investigate if the inflammatory white blood cells that are circulating in the blood infiltrate the growing tumour and whether this is affected by obesity. These experiments will provide us with valuable information about how the immune system can be altered in overweight and obese patients with oesophageal cancer and how the immune system may actually support tumour growth through a low level state of chronic inflammation. At the end of this project we will hope to identify possible novel targets and avenues for future therapies in the prevention and treatment of oesophageal cancer.
Genomic and Proteomic Signatures in Cancer
Presently, the five-year survival rate for those diagnosed with cancer of the oesophagus is less than 10%, and unfortunately incidence is increasing in the Western world. Oesophageal cancer most often arises from a pre-malignant condition known as Barrett’s oesophagus. Barrett’s oesophagus is characterised by a replacement of the normal oesophageal epithelial cells with cells more reminiscent of those that line the stomach. The development of Barrett’s oesophagus is closely related to chronic exposure of the oesophagus to gastric acids and bile (acid reflux) at the junction where the oesophagus meets the stomach.
Within the Dept. we have established large biobanks of blood and tissue specimens from patients with Barrett’s oesophagus and oesophageal cancer. We are employing a proteomic approach, utilizing state-of-the-art SELDI-TOF technology in collaboration with UCD, to investigate changes in serum protein patterns between patients with Barrett’s oesophagus and patients with oesophageal cancer.
The standard treatment for oesophageal cancer employs a multimodal approach, whereby patients receive a course of chemotherapy and radiotherapy (CRT) to shrink their tumours and limit its spread to distance sites, followed by surgery to remove the remaining tumour. Currently only a subset of patients (approx. 30%) has a beneficial response to pre-surgery CRT. The remaining patients receive no significant benefit from the CRT, yet are subjected to the side effects of treatment and increased time to surgery. We are examining blood taken from patients early-on in treatment and analysing the serum protein profiles, comparing those who respond to the pre-surgery CRT and those who do not. Identifying serum-based markers early in the course of treatment may allow us to identify those patients most likely to respond to CRT. Those unlikely to respond to CRT could potentially undergo surgery sooner, thereby improving prognosis.
A second research project in this field aims to identify a molecular genetic signature that can indicate patient response to radiation therapy. This involves identifying genes that are involved in the response to radiation, in particular, genes involved in promoting cell survival and cell death. The evasion of cell death is a hallmark of cancer and presents a major obstacle to successful treatment. We aim to identify genes that are involved in conferring resistance to radiation in tumour cells, and ultimately identify a gene profile that is indicative of patient response to therapy.
In addition, we are investigating the role of regulatory molecules called microRNAs in resistance to radiation-induced death. MicroRNAs, a relative new discovery, function to regulate genes within the cell. Mounting evidence points to a role for these molecules in important cellular processes, such as cell death. Recently, altered microRNA expression has been linked to a number of cancers and the evasion of cell death, however the expression and effects of miRNAs in radioresistance has yet to be studied. We aim to investigate whether these molecules are involved in the response to radiation and if so, identify a microRNA signature that is predictive of patient response to radiation therapy.
The data obtained in this project could ultimately be used in a diagnostic capacity, to determine pre-treatment, which patients are most likely to benefit from radiochemotherapy. It will also expand our knowledge of the critical mechanisms controlling tumour resistance to radiation therapy, and may identify novel targets for future therapies.
Inflammation and Cancer
Inflammation is one of the means by which our bodies help us to fight against infection. It is characterised by pain, swelling, redness, loss of function and heat. Although protective in the short term, in prolonged cases it can lead to conditions such as Rheumatoid arthritis and Crohn’s disease. The study of inflammation in cancer is warranted as it has been implicated in more than 20% of all cancer cases. Examples of this include Hepatitis infection with liver cancer and colon cancer through Inflammatory Bowel Disease (IBD). The symptoms of inflammation are due in part to our white blood cells travelling to the site of infection and secreting substances to help fight off the germs that are causing us harm. Our bodies secrete certain materials that attract our white blood cells to that specific infected area in the body. In the majority of instances when the infection has been cleared the area returns to normal, but in some cases the inflammation does not clear. Inflammation that does not resolve and remains chronic over time is thought to predispose cancer. A phrase often used to describe this type of inflammation is ‘a wound that does not heal’.
There has been an alarming increase in the incidence of adenocarcinoma of the oesophagus over the past 20 years in Western populations. Whilst the aetiology of oesophageal cancer remains largely undetermined there has been increasing interest in the role of gastro-oesophageal reflux disease (GORD) as a risk factor in its pathogenesis. Ongoing research in the group is focused on examining the expression of inflammatory markers in the progression from GORD, to Barrett’s oesophagus (a pre-malignant inflammation of the oesophagus defined by the presence of intestinal-like goblet cells), to adenocarcinoma of the oesophagus. The group are particularly interested in NF-κB (a pro-inflammatory factor), and have reported that oesophageal adenocarcinoma tumour tissues show high levels of activated NF-κB compared to non-tumour tissues from the same patients.
Inflammation and CancerA second study within the unit aims to examine the involvement of inflammation in the development of lung cancer. A variety of different white blood cell attractants such as (a) the IL-20 family, (b) the CXCL family, and (c) the pro-inflammatory cytokines, Tumour necrosis alpha (TNFα), and Interleukin-1 beta (IL-1β) will be examined for their role in the development of cancer. These proteins are released by our immune system and have various effects on our bodies, for instance the induction of inflammation. Also of interest in this project is tumour hypoxia, which refers to low oxygen conditions. The central area of many solid tumours is hypoxic, this allows the tumour to grow in size, and create new blood vessels (angiogenesis) which enables the tumour to spread to other sites in the body. In addition hypoxia has a role in inflammation. This project will also examine how these inflammatory proteins are regulated at the DNA level. In order to do this we will use drugs that can change the structure of our DNA (Epigenetics) and determine whether or not these drugs can be used in order to reduce the damaging effects of inflammatory responses.
A range of immortalised cell lines derived from human donors are used in this project to study cellular interactions in vitro. To closely examine the role of TNFα and IL-1β in the process of lung cancer, both have been inserted into a normal cell line. These normal cells are of bronchial epithelial origin. The cell line is now secreting the two pro-inflammatory cytokines continuously. Cells are growing under normal oxygen (21%) and low oxygen conditions (0.5%). This experiment will allow us to determine what effect hypoxia and inflammation are having on normal cell lines and we can also compare any changes to the lung cancer cell lines. Our ultimate aim is to change the normal cells into malignant cells. This will give us a valuable insight into the changes a normal cell undergoes on its journey to develop into a cancer cell. This work will possibly identify novel drug targets.
Angiogenesis and Cancer
Lung cancer is the leading cause of cancer-related mortality in Ireland.
Non-small cell lung cancer (NSCLC) accounts for approximately 80% of all lung cancers. Despite improvements in anti-cancer therapies such as chemotherapy, radiotherapy and surgery, the five-year survival for patients remains poor. Therefore, an increased understanding of the biology of this lung cancer subtype together with the development of more effective novel agents, may potentially lead to better treatment and overall survival for this patient group. Neuropilin-1 (NP1) is a novel receptor that binds vascular endothelial growth factor (VEGF), a potent growth factor for blood vessels that is required for a tumour to grow larger than 1-2cm in diameter. Preliminary data in our laboratory have shown that NP1 is present in lung cancer cells and is increased in patient lung tumour tissue compared to matched normal lung tissue. To date, little is known regarding the role of NP1 in lung cancer cell survival and growth.
We hypothesise that NP1 expression by lung tumour cells contributes to the survival and malignant behaviour of this cancer type, promoting resistance of these cells to conventional anti-cancer therapies. As a tumour grows, it develops areas of hypoxia (low oxygen levels) due to an inefficient blood supply. The response of a cell to hypoxia is due to a series of cell signalling events that determine whether the cell will die or survive. Unlike normal cells that usually die when exposed to hypoxic conditions, cancer cells often survive and continue to grow. Hypoxia is associated with increased production of VEGF by cancer cells and with tumour resistance to anti-cancer therapies such as chemotherapy and radiotherapy. We are interested in establishing the role of the NP1 receptor as a cell survival factor in lung cancer and envisage that blocking/inhibiting, or reducing the levels of the NP1 receptor in lung cancer cells, may ultimately inhibit cell survival signals thereby rendering the cancer cell more likely to die, particularly under hypoxic growth conditions.
In addition to further understanding the regulatory mechanisms by which NP1 mediates tumour cell survival in lung cancer cells under normoxic and hypoxic tumour growth, these findings may support the rationale for new targeted therapies in the treatment of lung cancer, either alone or in combination with chemotherapy. As a Translational Cancer Research Group, we aim to demonstrate direct clinical relevance VEGF and its receptors, VEGFR1, VEGFR2 and the Neuropilins in lung cancer through the use of retrospective patient tissue available to us as part of a lung cancer Biobank established within our group.
Bioactive Lipids, Thrombosis and Cancer
One research area within the Dept. is focusing on the role of two arachidonic acid metabolising enzymes; prostacyclin synthase (PGIS) and thromboxane synthase (TXS) in tumour cell survival mechanisms. These enzymes catalyse the generation of prostanoids, prostacyclin (PGI2) and thromboxane A2 (TXA2) respectively, and have been shown to be differentially regulated in a number of disease states. These prostanoids exert directly opposing effects on the vasculature; PGI2 is a dilator, which inhibits cell growth, and platelet activation/aggregation, whereas TXA2 has the opposite effects. The PGI2/TXA2 ratio is of particular importance in-vivo, with corresponding synthases shown to be differentially regulated in disease states. The role of these prostanoids and corresponding synthases have been investigated in a variety of cancer states, including breast, prostate, thyroid, lung, colorectal and bladder cancer. While PGIS has been shown to protect against tumour development, thromboxane synthase has been implicated as a survival factor in many cancers, and has been associated with a poor prognosis. We are examining the interactions between these pathways, platelet activation, apoptosis (programmed cell death) and angiogenesis (new blood vessel growth) in relation to their effects on tumour cell survival pathways.
Previous work carried out in our laboratory demonstrated TXS over-expression in non-small cell lung cancer (NSCLC) tumour samples, relative to matched normal controls. In contrast PGIS expression was reduced or lost in tumour samples, relative to matched controls. These findings implicate TXS as a potential survival factor in the disease, while PGIS may protect against tumour development. This hypothesis was supported by over-expression of these enzymes in a NSCLC cell line. While over-expression of PGIS inhibited tumour cell growth, increased apoptosis (programmed cell death) and reduced the invasive potential of the cells, over-expression of TXS resulted in directly opposing effects. Targeted inhibition of the TXS enzyme significantly reduced tumour cell growth and increased apoptosis in a panel of lung cancer cell lines, further implicating this enzyme as a survival factor and potential therapeutic target in the treatment of the disease. While thromboxane synthase and prostacyclin synthase have been shown to be involved in tumour survival and progression in a variety of cancer types, little is known of the role of these enzymes in oesophageal cancer. Further studies in this area aim to examine the expression and relative contributions of these opposing enzymes in oesophageal cancer.
Thromboembolic disease following clinically disordered coagulation is among the most frequent haematological complications encountered by oncologists, affecting 15% of all cancer patients. It is also the second leading cause of death for cancer patients. The balance between prostacyclin metabolite generation and platelet thromboxane synthesis is well known to influence thrombosis. Prostacyclin synthase and thromboxane synthase will be therefore be examined in relation to thrombosis within the patients’ tumour, using both fresh and retrospective tissue and blood samples (from both NSCLC and oesophageal cancer). In addition, due to the well-known link between thrombosis and angiogenesis, the link between PGIS and TXS expression, and tumour angiogenesis will also be examined.
This work is the first in its kind taking a translational approach to investigate expression of the TXS enzyme and the coagulation system in both lung and oesophageal cancer. Elucidation of the mechanisms regulating these pathways will potentially result in novel therapeutic strategies for intervention in these cancer states.