Key molecular events that contribute to formation of adrenocortical cancer are IGF2 overexpression, TP53-inactivating mutations, and constitutive activation of the Wnt/b-catenin signalling pathway via activating mutations of the b-catenin gene.
The genetic predisposition to adrenocortical cancer in children has been well established in the Li-Fraumeni and Beckewith-Wiedeman syndromes due to germline p53 mutation located at 17p13 and dysregulation of the imprinted IGF-2 locus at 11p15, respectively.
IGF-II mRNA levels were more than 10-fold higher in hormonally active adrenocortical carcinomas than in normal adult adrenals, and increased IGF-II-like immunoreactivity was detectable in these carcinomas.
IGF2 promotes growth of adrenocortical carcinoma cells, but its overexpression does not modify phenotypic and molecular features of adrenocortical carcinoma.
We have previously demonstrated that estrogen receptor (ER) alpha (ESR1) increases proliferation of adrenocortical carcinoma (ACC) through both an estrogen-dependent and -independent (induced by IGF-II/IGF1R pathways) manner.
The xenografts precisely reproduced the dysregulation of the insulin-like growth factor (IGF) system [overexpression of the IGF-II and IGF-binding protein-2 (IGFBP-2) genes] typical of adrenocortical carcinoma.
We previously demonstrated that, in adrenocortical carcinoma (ACC), ERα is upregulated and that estradiol activates the IGF-II/IGF1R signaling pathways defining the role of this functional cross-talk in H295R ACC cell proliferation.
Previous studies have identified overexpression of insulin-like growth factor 2 (IGF-2) and constitutive activation of β-catenin as key factors involved in the development of adrenocortical carcinoma.
It is evident, therefore, that high levels of IGF-II in combination with overexpression of the IGF-I-receptor can provide a significant growth advantage for adrenocortical carcinoma cells and thus contribute to the highly malignant phenotype of this rare type of cancer.