BJA/RCoA Project Grant
Preclinical identification of local anaesthetics that target colon cancer cells
Prof Tim Hales
Surgical excision is the primary treatment for many types of malignancy including breast, prostate and colon cancer. However, disruption of the tumour during surgery increases the likelihood of releasing malignant cells into the circulation, enabling spread through the body. A greater number of circulating cancer cells following surgery increases the likelihood of subsequent cancer recurrence and metastasis.
Several recent studies suggest that the use of local anaesthetics (LAs) during surgical tumour excision reduces subsequent cancer recurrence and metastasis. LAs are sometimes administered regionally during surgery to provide pain relief, an approach that reduces the requirement for general anaesthesia (GA) and opioid pain killing drugs. The traditional anaesthetic approach using a combination of GA and morphine like drugs (opioids) may suppress the patient's immune response prolonging the survival of circulating cancer cells. These cells may then reseed and/or metastasise to distant tissues (e.g. lung and or liver). The ability of LAs to reduce the requirement for GAs and opioid drugs may contribute to their beneficial effects during cancer surgery.
LAs also directly inhibit cancer cell invasion by inhibiting proteins known as voltage-activated Na+ channels (VASCs). Several studies demonstrate that breast, colon and prostate cancer cells express VASCs whereas equivalent non-cancerous tissues do not contain VASCs. It is possible that the therapeutic benefit of regional anaesthesia during cancer surgery could be due to absorption of low concentrations of LAs into the circulation. However, a more effective way of elevating circulating LA concentrations (to inhibit VASCs on cancer cells) would be to administer them directly onto the tumour and/or by intravenous (IV) infusion during the surgical procedure. In the case of colon cancer, direct intraperitoneal (IP) application may provide the greatest benefit. Importantly, our data demonstrate that the reversal of inhibition by LAs of VASCs on colon cancer cells is extremely slow and may provide ongoing protection against reseeding and metastasis during surgery. One potential criticism of this approach is the possibility of toxicity occurring through LA induced inhibition of VASCs in heart muscle due to absorption of high concentrations of LAs. Interestingly, LAs are routinely administered by continuous IV infusion for certain chronic pain conditions without adverse consequences. Initial data from our lab indicates that VASCs in cancer cells are sensitive to lower concentrations of LAs than are VASCs in the heart. We will use electrophysiological assays to establish the concentration-response relationship for the inhibition of VASCs expressed by cancer cells and heart tissue using clinically important LAs and other related VASC inhibitors. We will determine the dose dependence and time courses for the inhibitory effects of the LAs on the metastatic potential of colorectal cancer cells using an established invasion model. The results of this preclinical project will provide essential information for planning a future clinical study examining the benefit of direct LA application onto tumours prior to surgical excision. While the focus here is on colon cancer the results will be applicable to several malignancies including, prostate, breast and ovarian cancers, which also involve VASCs.
The role of the Nitric Oxide regulatory pathway in critical illness
Dr Simon Lambden
Nitric Oxide is an essential molecule found throughout the body that plays a critical role in many of the body's functions. In severe infection and sepsis, production of nitric oxide increases markedly. This is a major reason why affected people require admission to intensive care, develop failure of multiple organs, and often die as a consequence.
Nitric oxide is produced by an enzyme called nitric oxide synthase. The activity of this enzyme is regulated by another body substance called ADMA. ADMA reduces the activity of nitric oxide synthase and therefore produce less nitric oxide. Changes occur in this pathway during critical illness that affect nitric oxide production. As yet we do not understand how these changes contribute to the severity of disease. Our preliminary work has shown that a group of white blood cells called monocytes is responsible for a major portion of the change in nitric oxide production in severe illness; abnormalities of the interaction between ADMA, nitric oxide synthase and the enzyme that breaks down ADMA are responsible for this change. We want to further examine the role of ADMA in the abnormal production of nitric oxide seen in critical illness. We will combine studies in animals in the laboratory, and in septic patients on the intensive care unit to determine mechanisms involved in the control of nitric oxide production. In our animal model we will seek to determine how the enzyme that breaks down ADMA (known as DDAH) controls the production of NO by the monocytes as we know this play a vital role in the abnormal response to critical illness. By using animal models that have been genetically modified to not have DDAH in monocytes, we will see precisely how this enzyme plays its part in the response to infection. We will be able to compare changes in the ADMA level in both blood and within monocytes in these two groups to determine the role of this part of the pathway in the control of NO production.
We will also study patients admitted to the intensive care unit whom we expect to stay for longer than a week. We will collect detailed data on their clinical condition and severity of illness through a series of blood tests, observations and investigations. We will examine the changes in blood and monocyte ADMA levels over time, and see whether variation in the gene that controls production of the DDAH enzyme makes a difference in terms of both ADMA levels and outcome.
This study will add a great deal to our understanding of how the body responds abnormally to critical illness, and how this can contribute to their illness severity. If successful it will lead to larger studies in this area and help guide the identification of those patients likely to develop a severe response to illness. It may potentially result in the evolution of therapeutic interventions in the management of severe illness.
Please see the NIAA's position statement on the use of animals in medical research.
The role of HIV gp120-driven macrophage-sensory neuronal interactions in the pathogenesis of HIV-associated polyneuropathy and neuropathic pain
Prof Andrew Rice
People living with HIV experience chronic, long lasting pain caused by nerve damage, known as painful HIV-associated sensory neuropathy (HIV-SN). Now that most people living with HIV have a relatively normal life expectancy, because of the success of antiretroviral drugs in suppressing the immunodeficiency aspects of HIV infection and thus the onset of AIDS, the clinical focus has switched from saving lives to quality of life issues such as controlling symptoms like the severe neuropathic pain (related to nerve damage) associated with HIV-SN. HIV-SN is the most frequent manifestation of HIV in people who are otherwise well, afflicting about 40% of patients as reported in several different studies from around the world in both well- and poor-resourced healthcare settings. The associated pain is often severe and has a major impact on their quality of life and mental health. The focus of this proposal is to conduct laboratory research that will elucidate the cause of HIV-SN and the associated neuropathic pain, in particular we will:
- Reveal the time point in the natural history of HIV infection at which nerve damage occurs. This currently unknown and this research will give us clinically important information about when we need to intervene in the clinic in order to prevent/reverse nerve damage
- Elucidate how the virus interacts with nerves to cause the damage. On the basis of our previous research we have developed a hypothesis that this damage is not due to a direct interaction between the virus and nerve cells. Rather a type of immune cell called a macrophage, which is infected by HIV, appears to be the crucial intermediary step. Our evidence suggests that when stimulated by an HIV protein called gp120, certain macrophage receptors (CCR5) are activated which causes the macrophage to release a battery of chemicals called cytokines which known to be toxic to nerve cells. The major part of this programme of research will be to understand the mechanism of this process.
- Importantly, the final stage will be identifying therapeutic strategies that can attenuate this macrophage/cytokine-driven neurotoxicity. Crucially, we will evaluate the potential of drugs that are already available for use in humans such as the CCR5 antagonist Maraviroc, which is as an antiretroviral drug available in the clinic. Therefore if our hypothesis is correct we can rapidly move to clinical trials, conducted in our unit, in order to translate the benefits of research into the clinic for the benefit of patients.
