Innovative Approaches for characterisation and treatment of Olfactory Neuroblastoma

Despite recent advances in cancer treatments, outcomes for patients with advanced olfactory neuroblastoma (ONB) remain poor. There is an increasing need to develop novel treatments as alternatives to conventional therapies. The current gold standard treatment is craniofacial surgery followed by radiotherapy and/or chemotherapy, but this is associated with significant long term side effects, particularly in young patients. Early stage disease responds well to treatment, but is associated with a high (60%) recurrence rate, while advanced and metastatic disease has a poor prognosis (5 year survival less than 25% in high grade disease; less than 5% with metastasis at diagnosis).

Cell signalling pathways (protein interaction cascades triggered by biological cues such as hormones) normally act to maintain cell health, but over activity of these pathways is reported in many cancers. Most pathways contain multiple feedback control loops and cross-react with other pathways, hence drugs designed to target a single pathway are usually met with rapid resistance. Two of these pathways 'mTOR/MAPK' and 'SHh" play a role in ONB; therefore combined targeted treatment against both simultaneously is a promising strategy

We are currently establishing specific drug combinations that are highly effective on cells in the lab, using measures of impaired cell health as our outcome. We are also using novel techniques to look at changes in gene expression in ONB, which might suggest alternative targets and prognostic biomarkers. Having established an effective treatment using cells, we will validate this on a mouse model, using bioluminescence techniques to measure tumour size and spread in response to treatment. Our ultimate goal is to establish a suitable treatment combination for human trial stage in ONB.

Olfactory neuroblastoma (ONB), a rare sinonasal tumour, is advanced at diagnosis in a third of patients, in whom prognosis is poor (disease free survival 1.5y). Paediatric disease is frequently aggressive, and the current gold standard treatment (surgery plus chemoradiotherapy) results in significant long-term sequelae. ONB has a strikingly high recurrence rate of 60%, meaning that alternative treatment options and prognostic biomarkers are urgently required.

The sparse data available on ONB suggests that the mTOR/MAPK and SHh signalling pathways play a role in tumourigenesis. In cancers, cross-talk between pathways provides a mechanism of drug resistance and treatment failure when single agent inhibitors are used against many different tumours. Targeting both pathways therefore makes rational sense.

Aims: i) Establish an inhibitor combination that causes simultaneous pathway inhibition in ONB; ii) RNA seq to identify novel targets and biomarkers; iii) Validate findings on fresh tissue and iv) Reproduce effective treatment in a nude mouse model.

Objectives: Using human ONB cell lines, we have established that inhibitors to both pathways reduce cell viability in a dose and time dependant manner. Comparison of multiple treatment combinations suggests novel S6K1 inhibitors plus growth factor receptor inhibition with SHh inhibitors is highly promising. Further outcome measures of efficacy will include western blot, RT-qPCR, apoptosis and cell cycle analysis. RNA seq (n=4 samples, 4 controls) will examine gene expression data, and significant candidates will be validated in overexpression/siRNA cell line studies and on both fresh and fixed tissue samples. In vivo assessment of the optimised drug combination in nude mice will validate the efficacy and assess tolerability.

Establishment of a safe, effective, targeted, combined therapy could then be proposed for clinical trials, ultimately aiming to treat both primary and recurrent / inoperable disease.

This project has the potential to impact on a number of different groups:

Patient benefits: Despite receiving current gold standard treatment (craniofacial resection plus radiotherapy plus chemotherapy in selected cases) survival rates for patients with advanced and metastatic disease remain poor. Even for patients who do undergo apparent successful surgical resection, this tumour is associated with significant recurrence rates, and many patients will eventually live with recurrent disease after a disease free interval. Since 33% of cases occur in patients under the age of 40, there is therefore a real need for treatment to:
- Form part of primary treatment with the aim of preventing future recurrence as an adjuvant treatment to surgical excision of the tumour (where possible).
- Prolong survival (and maintain quality of life for as long as possible) by slowing or stopping disease progression in advanced and metastatic disease.
We hope that this study will lead to future introduction of novel treatment options for patients with this recurring condition, and reduce the long term sequelae associated with current treatment options (which do not prevent recurrent disease in many cases). With this in mind, where possible we have chosen drugs already at stage III clinical trial, if not already in clinical practise (ie the safety and side effect profile is already established). This will reduce the time from bench to bedside and ensure that patients benefit directly from the results of this research with minimal delay.

Scientific / Medical community benefit: This work is also of interest to groups studying the same combination of signalling pathways in other tumours, and may suggest novel approaches for cancer where this treatment regimen has not been considered before.
- One of the novel aspects of this project is that we are working with S6K1 inhibitors, which despite great need are not yet in clinical use. Targeting this region has the potential to avoid some of the feedback loops associated with drug resistance to inhibitors that act higher up the signalling pathway. We hope to demonstrate the novel candidates we are working with are both safe and effective, with a view to ultimately establishing first in human trials. Since many cancers and other diseases exhibit aberrations in mTOR signalling, these drugs may be of future widespread importance.
This work is at an early stage, and for novel treatments 5-10 years of trials are needed before the drugs can enter mainstream use. However, aside from the S6K1 inhibitors, the drugs used in this project are already at stage 3 trials if not already in use for another clinical indication. They have established safety margins, and side effect profiles, and it would therefore be possible to instigate human trials of these drugs as treatment for ONB on a much faster timescale.

Commercial sector benefit: The drug development market is a highly competitive one, with some global pharmaceutical companies involved in developing similar agents. This project has potential to support the development of a drug by a UK based company, which may ultimately be used around the world.

NHS benefit: At present ONB patients require lifelong surveillance with annual MRI scan and outpatient endoscopy due to high recurrence rates. A treatment that reduced or removed this recurrence rate would therefore have an economic benefit to the NHS (and also to the patients quality of life).

Personal benefits: On a personal level this project is giving me the chance to improve my understanding of signalling pathways and the different techniques required to investigate them. It will give me a range of transferable skills, and allow me to establish a network of contacts to advise me in my future career as an academic surgeon. My ultimate aim is to translate basic science into therapeutic agents that can be used in the clinical ENT setting.