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BackgroundUnderstanding the pathways that drive adrenocortical carcinoma (ACC) is essential to the development of more effective therapies. This study investigates the role of the transcription factor HOXB9 and other HOX factors in ACC and its treatment.MethodsWe used transgenic mouse models to determine the role ofHoxb9in adrenal tumour development. Patient transcriptomic data was analysed for the expression of HOX genes and their association with disease. Drug response studies on various adrenocortical models were done to establish novel therapeutic options.ResultsOur human ACC dataset analyses showed high expression ofHOXB9, and other HOX factors, are associated with poorer prognosis. Transgenic overexpression ofHoxb9in the adrenal cortex of mice with activatedCtnnb1led to larger adrenal tumours. This phenotype was preferentially observed in male mice and was characterised by more proliferating cells and an increase in the expression of cell cycle genes, includingCcne1. Adrenal tumour cells were found to be dependent on HOX function for survival and were sensitive to a specific peptide inhibitor.ConclusionsThese studies showHoxb9can promote adrenal tumour progression in a sex-dependent manner and have identified HOX factors as potential drug targets, leading to novel therapeutic approaches in ACC.

// Jeffrey C. Francis 1 , Amy Capper 1 , Jian Ning 2 , Eleanor Knight 2 , Johann de Bono 3 and Amanda Swain 1, 2 1 Division of Cancer Biology, The Institute of Cancer Research, London SW3 6JB, UK 2 Tumour Profiling Unit, The Institute of Cancer Research, London SW3 6JB, UK 3 Division of Clinical Studies, The Institute of Cancer Research, London SM2 5NG, UK Correspondence to: Amanda Swain, email: amanda.swain@icr.ac.uk Keywords: aggressive invasive prostate cancer; prostate cancer mouse models; cell lineage plasticity; epithelial to mesenchymal transition Received: May 18, 2017 Accepted: July 03, 2017 Published: January 10, 2018 ABSTRACT Aggressive lethal prostate cancer is characterised by tumour invasion, metastasis and androgen resistance. Understanding the mechanisms by which localised disease progresses to advanced lethal stages is key to the development of effective therapies. Here we have identified a novel role for the transcription factor, SOX9, as a driver of aggressive invasive prostate cancer. Using genetically modified mouse models, we show that increased Sox9 expression in the prostate epithelia of animals with Pten loss leads to a highly invasive phenotype and metastasis. In depth analysis of these mice and related in vitro models reveals that SOX9 acts a key regulator of various processes that together promote tumour progression. We show that this factor promotes cell lineage plasticity with cells acquiring properties of basal stem cells and an increase in proliferation. In addition, increased SOX9 leads to changes in cytoskeleton and adhesion, deposition of extracellular matrix and epithelia to mesenchyme transition, properties of highly invasive cells. Analysis of castrated mice showed that the invasive phenotype driven by SOX9 is independent of androgen levels. Our study has identified a novel driver of prostate cancer progression and highlighted the cellular and molecular processes that are regulated by Sox9 to achieve invasive disease.

Germline mutations in the tumour suppressor BRCA2 predispose to breast, ovarian and a number of other human cancers. Brca2-deficient mouse models are used for preclinical studies but the pattern of genomic alterations in these tumours has not yet been described in detail. We have performed whole-exome DNA sequencing analysis of mouse mammary tumours from Blg-Cre Brca2(f/f) Trp53(f/f) animals, a model of BRCA2-deficient human cancer. We also used the sequencing data to estimate DNA copy number alterations in these tumours and identified a recurrent copy number gain in Met, which has been found amplified in other mouse mammary cancer models. Through a comparative genomic analysis, we identified several mouse Blg-Cre Brca2(f/f) Trp53(f/f) mammary tumour somatic mutations in genes that are also mutated in human cancer, but few of these genes have been found frequently mutated in human breast cancer. A more detailed analysis of these somatic mutations revealed a set of genes that are mutated in human BRCA2 mutant breast and ovarian tumours and that are also mutated in mouse Brca2-null, Trp53-null mammary tumours. Finally, a DNA deletion surrounded by microhomology signature found in human BRCA1/2-deficient cancers was not common in the genome of these mouse tumours. Although a useful model, there are some differences in the genomic landscape of tumours arising in Blg-Cre Brca2(f/f) Trp53(f/f) mice compared to human BRCA-mutated breast cancers. Therefore, this needs to be taken into account in the use of this model.