Targeted disruption of SNARE mediated secretion for the treatment of neuroendocrine cancers

Supervisors: Professor Bazbek Davletov (BMS and CMIAD) and Dr Elizabeth Seward (BMS and CMIAD)

Application deadline: Friday 14 December 2012.

Project description

Neuroendocrine tumors (NETs) are neoplasms that arise from cells of the endocrine (hormonal) and nervous systems. Neuroendocrine cells are present not only in endocrine glands that secrete hormones, but also diffused in all body tissues. NETs include certain tumors of the gastrointestinal tract and of pancreatic islet cells, adrenomedullary tumors, certain thymus, pituitary and lung tumors. Peripheral nervous system tumors also include Schwannoma and neuroblastoma. Despite differing embryological origin, NETs have common phenotypic characteristics. NETs show tissue immunoreactivity for markers of neuroendocrine differentiation (pan-neuroendocrine tissue markers) and may secrete various peptides and hormones. 70-85% pancreatic neuroendocrine tumours secret hormones that cause symptoms.In about 90% of cases of neuroblastoma, elevated levels of catecholamines or their metabolites are found in the urine or blood. Secretory activity of the tumor cells may be used for initial diagnosis. Surgery is a curative treatment for some neuroendocrine tumors but the majority of NETs are currently untreatable. For example two-thirds of high-risk neuroblastoma cases do not respond adequately to high-dose chemotherapy and are progressive or refractory. Relapse after completion of frontline therapy is also common.

In this project the therapeutic potential of newly engineered proteins designed to block excessive secretion and to stop growth of NETs will be investigated. One defining feature of NETs is an abundance of so-called neuronal SNARE proteins which are responsible for robust secretion of hormones[1]. Thirty eight distinct SNAREs have been identified in mammalian cells, some of which are involved in common intracellular trafficking events found in all cells and are required to maintain cellular homeostasis and for growth, while others are expressed only in professional secretory cells and are specifically required for the fusion of secretory granules with the plasma membrane. It is well known that certain bacterial enzymes target neuronal SNAREs to block release of neurotransmitters from mature neurons. One member of these bacterial neurotoxins is botulinum molecule type A, the active ingredient of BOTOX[2]. BOTOX is used widely to locally paralyze muscles allowing both medical (e.g. spasm treatments) and cosmetic (wrinkle removal) benefits.

Here we propose to systematically investigate responsiveness of human NET cells to SNARE-targeting enzymes which have been engineered in our laboratories to interfere with NETs’ growth and function. The pharmacology of synthetic molecules will initially be assessed using a range of biochemical and single cell assay techniques applied to well established human neuroblastoma and adenoma cell lines. Fluorescent based assays and patch clamp electrophysiology will be used to monitor NET cell viability, vesicle trafficking and hormone secretion. If we can decrease hormone secretion and cell survival of NET cell lines, we will test ex-vivo the possibility of using type the engineered molecules to decrease cell growth and hormone secretion from primary tumours obtained from NET patients. Ultimately, this work will open a new avenue for using engineered proteins to treat chemotherapy-resistant neuroendocrine tumours.

References:

• Jahn, R. and R. H. Scheller (2006).
  "SNAREs--engines for membrane fusion."
  Nat Rev Mol Cell Biol 7(9): 631-643.
• Davletov, B., M. Bajohrs, et al. (2005).
  "Beyond BOTOX: advantages and limitations of individual botulinum neurotoxins."
  Trends Neurosci 28(8): 446-452

Contact details:

Professor Bazbek Davletov

Email: B.Davletov@sheffield.ac.uk

Web: http://www.sheffield.ac.uk/bms/research/davletov

Dr Elizabeth Seward

Email: E.P.Seward@sheffield.ac.uk

Web: http://www.shef.ac.uk/bms/research/seward