Harnessing TNF-mediated cell death in cancer

Inflammation and cell death are ancient processes of fundamental biological importance that enable survival and adaptation during infection and injury. Tumour necrosis factor (TNF) is the prototypical proinflammatory cytokine that signals, through its type 1 receptor (TNF-R1), either cell survival, cell proliferation or cell death1. TNF stimulates an inflammatory response whose 'purpose' is to remove the source of the disturbance, allowing the host to adapt to an abnormal condition, and, ultimately, to restore functionality and homeostasis to the tissue. However, when deregulated, inflammation can drive chronic remodelling and tissue repair, which contributes to chronic inflammatory diseases, cancer and treatment failure.

The principle idea addressed by this application is that cell survival and adaptation mechanisms of tumours are supported, at least in part, by cancer-related inflammation, and that this can be successfully targeted by switching the TNF response from pro-inflammation to cell death. Despite clear evidence that TNF can signal cell survival and death, the mechanisms that can switch between the distinct biological outcomes remain elusive. This is important as its resolution, and putative therapeutic intervention, would allow the diversion of cancer-related inflammation into activation of cell death. Our starting point for this proposal is substantial new data on the regulation of TNF-signalling and cell death.

We identified that the Ub-receptor function of cIAP1 critically controls TNF signalling, selectively regulating the pro-death effects of TNF, without inhibiting the NFkB pathway. Our preliminary data indicate that a point mutation in the Ub-binding domain of cIAP1 switches the TNF response to cell death, and completely blocks tumorigenesis. Here, we propose to use mouse models, imaging, and biochemical approaches to decipher how the Ub-receptor function of cIAP1 regulates TNF-induced cell death, and whether switching the TNF response from pro-inflammation to cell death causes tumours to permanently regress.

Cytokines of the TNF-superfamily are classic inducers of programmed necrosis (necroptosis). Although anticancer therapies that trigger the necrotic death of tumour cells may be particularly attractive to overcome apoptosis resistance, because TNF-induced necroptosis also facilitates inflammation, and deregulated inflammation can also support tumorigenesis, it will be important to carefully examine the physiological and pathological consequence of stimulating TNF-induced necrosis. At present, there is no clear evidence to indicate whether necrosis is beneficial or harmful in cancers. Here we will determine the therapeutic opportunities and pathological consequences of manipulating TNF signalling in cancer.

Given that TNF plays an eminent role in diverse pathological processes at the core of human diseases, our findings will provide new avenues for therapeutic intervention strategies.

Deregulated cell death and inflammation can drive chronic remodelling and tissue repair, which can contribute to cancer and treatment failure. The principle idea addressed by this application is that cell survival and adaptation mechanisms of tumours are supported, at least in part, by cancer-related inflammation, and that this can be successfully targeted by switching the TNF response from pro-inflammation to activation of cell death, causing tumours to permanently regress.

Despite clear evidence that TNF can signal cell survival and death, the mechanisms that can switch between the distinct biological outcomes remain elusive. This is important as its resolution, and putative therapeutic intervention, would allow the diversion of cancer-related inflammation into activation of cell death. Our starting point for this proposal is substantial new data on the regulation of TNF-signalling and cell death.

We identified that the Ub-receptor function of cIAP1 critically controls TNF signalling, selectively regulating the pro-death effects of TNF, without inhibiting the NFkB pathway. Our preliminary data indicate that a point mutation in the Ub-binding domain of cIAP1, which abrogates its ability to bind to M1- and K63-linked Ub chains, switches the TNF response to cell death, and completely blocks tumorigenesis. Mechanistically, we find that the Ub-binding domain of cIAP1 regulates intracellular trafficking of TNF-R1, and the consequences of RIPK1 ubiquitylation. Our data are consistent with a scenario whereby Ub-binding of cIAP1 participates with ESCRT-0 in capturing and sorting ubiquitylated TNF-R1 and RIPK1 for recycling.

Here, we propose to use mouse models, imaging, and biochemical approaches to decipher how the Ub-receptor function of cIAP1 regulates TNF-induced cell death, and whether switching the TNF response from pro-inflammation to cell death is beneficial or harmful in cancer.

Impact and potential beneficiaries of this research:

-Scientific community:
The successful conclusion of the proposed project is expected to provide a better understanding of the molecular mechanisms that control Ubiquitin (Ub)-dependent regulation of signal transduction pathways that influence the ability of multi-cellular organisms to adapt to perturbations. As such our research addresses fundamental issues relevant to normal animal physiology and following exposure to stress. Further, as Ub-mediated regulation of cell death and tissue repair is involved in almost every aspect of life, the proposed project will also impact the health-care community. Of particular interest is the notion that cell death regulatory proteins also fulfill nonlethal functions in differentiation and tissue remodeling. It is now clear that the cell death machinery is involved in releasing signals to communicate with their cellular environment, to promote cell division, tissue regeneration, and wound healing. Unraveling the molecular details governing this process could lead to a better understanding of aging, tissue regeneration and cancer.

- Cancer patients:
One of the key problems in cancer is the adaptive nature of tumours. It is now recognised that the Ub system modulates key signal transduction pathways that have direct implications in the 'evolvability' of tumours. Hence, cancer treatments would be significantly more successful if it was possible to target Ub-dependent signalling events. Our research addresses a fundamental aspect of Ub-dependent tissue repair. Ultimately, this work will provide new insights into the mechanisms through which Ub-dependent signalling contributes to cancer, and how we can translate this information for patient benefit.

- Public sector, Academia/Pharma based drug development teams:
Given TNF's importance under physiological and pathological conditions, and its central role in chronic inflammatory diseases, inflammation-associated cancer, and cancer-related inflammation, the results of this project will be of significant interest not only for academic but also private drug development groups. The identification of the molecular mechanisms through which TNF signalling can be switched from pro-inflammation to cell death will open up new avenues for therapeutic intervention strategies. It is anticipated that a clinical trial could follow from this study within five years. This will have obvious benefits in health and well being affecting the public sector, and can be exploited by the industry for the development of novel technologies for prevention and therapy of liver cancer in the early phases of the disease.

- General public, schools:
The project is a clear-cut example of the development of suitable experimental models for understanding the mechanism of disease and to develop new methods for prevention and cure. Thus results arising from the project can be used to illustrate the process in education, leading to obvious cultural benefits by emphasizing the importance of scientific approaches in health care.