Identification of therapeutic sensitivities and pathways driving adrenocortical carcinoma

Tumours of the adrenal cortex are relatively common with a prevalence of 1-10%. Most of these are benign, however, in rare case adrenocortical carcinoma (ACC) can develop which is aggressive and has a poor 5 year prognosis. Understanding pathways that drive ACC progression is essential to the development of more effective treatments and for the prediction of individual outcomes. Next generation sequencing studies have revealed recurrent alterations present in human disease. These studies have identified mutations in the WNT signalling pathway, including activating mutations in CTNNB1, to be one of the most frequent alterations. Studies in mice have shown that activating mutations in Ctnnb1 can give rise to tumour formation in the adrenal cortex, highlighting the value of this model to study adrenal tumourigenesis. We have identified HOXB9 as a gene expressed in the early stages of adrenal cortex development and upregulated in adrenal tumours driven by activating Ctnnb1 mutations in mice. Human ACC tumours also show upregulation of HOXB9 expression that correlates with WNT signalling dysregulation and decreased survival frequency suggesting a role for this gene in carcinogenesis. In preliminary studies, we have generated transgenic mice with elevated Hoxb9 expression in developing and adult adrenal cortical cells. Mice that contain this transgene and an activating Ctnnb1 mutation showed acceleration of tumourigenesis characterised by increased cell proliferation and tumour weight and in the appearance of cells with a neoplastic undifferentiated spindle shaped phenotype. These studies indicate that HOXB9 can cooperate with the WNT signalling pathway to drive adrenal tumour progression.
The aim of this project is to investigate the cellular and molecular mechanisms and pathways by which HOXB9 drives tumour progression. Using in vitro and in vivo approaches we will determine the role of this gene in adrenocortical tumour cell proliferation and survival, cell fate and differentiation. We will identify the molecular pathways associated with HOXB9, including its interaction with the WNT signalling pathway.
An additional aim of this project is to characterise the drug sensitivities associated with the WNT signalling pathway in adrenocortical carcinoma. Using various ACC models with dysregulated WNT signalling we will investigate the effect of drugs targeting this pathway on cell survival in vivo and in vitro. Using high throughput drug library screens we will identify combinations therapies that will increase the effectiveness of these targeted compounds. In a complementary approach, we will use RNA interference screens to identify the key nodal points in the WNT signalling pathway that when inhibited achieve a therapeutic response in ACC.
The ultimate goal of the studies proposed is to identify novel pathways and drug sensitivities in adrenocortical carcinogenesis that will provide important information that will aid in the development of clinical therapies to treat this rare and aggressive disease.

Rare adrenocortical carcinoma (ACC) is an aggressive disease with poor 5 year prognosis. Recent sequencing studies have revealed recurrent alterations in the WNT signalling pathway to be one of the most frequent alterations in ACC. Studies in mice have shown that an adrenal cortical specific activating mutation in Ctnnb1 can give rise to tumour formation, highlighting the value of this model to study adrenal carcinogenesis. We have identified HOXB9 as a gene upregulated in adrenal mouse tumours driven by an activating Ctnnb1 mutation and in human ACC samples where high levels correlate with WNT signalling dysregulation and decreased survival frequency.
The aim of this project is to investigate the cellular and molecular pathways by which HOXB9 drives tumour progression. We have generated transgenic mice with elevated Hoxb9 expression in adrenal cortical cells. Mice that contain this transgene and an activating Ctnnb1 mutation showed acceleration of tumourigenesis. We will fully analyse the adrenal tumour phenotype of these mice. We will use adrenocortical cell lines to confirm the functional role of HOXB9 in processes such as cell proliferation, survival, migration and invasion. We will also identify the molecular pathways associated with HOXB9, including its interaction with the WNT signalling pathway.
An additional aim of this project is to characterise the drug sensitivities associated with the WNT signalling pathway in ACC. Using various ACC models with dysregulated WNT signalling we will investigate the effect of drugs targeting this pathway on cell survival in vivo and in vitro. Using high throughput drug library screens we will identify combination therapies that will increase the effectiveness of these targeted compounds. We will also use RNA interference screens to identify the key nodal points in the WNT pathway that when inhibited achieve a therapeutic response in ACC.

This project grant will generate important novel data on the pathways driving adrenocortical carcinogenesis and on the drug sensitivities of adrenal tumours with dysregulated WNT signalling. This information will be of great interest to researchers and clinicians in the field of cancer biology in the UK and worldwide. These clinically relevant studies will help design novel therapies and may provide biomarkers for disease progression and response to treatment, which is sorely needed in this aggressive disease with limited therapeutic options.