Dissecting non-canonical actions of insulin receptor isoforms in breast cancer progression and metabolic reprogramming

The IGF-I receptor (IGF-IR) and the Insulin receptor (IR) are master regulators of development, growth and metabolism. These receptors are overexpressed in most tumors and play a role in cancer progression and therapy resistance, especially in cancers associated with diabetes and obesity. We and others have identified a unique role in cancer progression for the IR isoform A (IR-A), the so-called 'fetal' isoform, which is a dual receptor for insulin and IGF-II. Recently, we found that the collagen receptor DDR1 interacts with IR-A and IGF-IR in a ligand dependent manner and enhances cancer cell proliferation and invasion in response to IGF-I/II. Activation of this loop feeds forward DDR1 expression. These findings identify a relevant modulator of the IGF axis and establish a novel connection between the IGF axis and the tumor microenvironment. We hypothesize a specific role of IR isoforms (IR-A and IR-B) in cancer metastatic behavior, due in part to intrinsic signaling differences, but also by more stable DDR1 - IR-A complexes mediated by IGF-II rich environment. DDR1 - IR-A complexes may contribute to biased IR-A signaling that favors cell stemness and invasion.

Our preliminary data also suggest unexpected implications of IR in the metabolic reprogramming of breast cancer cells. Therefore, we hypothesize that mechanisms regulating the relative abundance of the two IR isoforms may differentially affect the metastatic phenotype and the metabolic flexibility of cancer cells in response to different environmental cues and cancer stages. We aim to elucidate: a) the specific impact of the two IR isoforms in breast cancer growth, invasion and metastasis; b) the role of IR isoforms on metabolic reprogramming and metabolic flexibility; c) the implications of the functional crosstalk between IR isoforms and DDR1. On these bases, we aim to identify new combination target therapies.Using the CRISPR/Cas9 technology of genome editing, we will generate engineered breast cancer cells KO for the endogenous IR and expressing solely IR-A or IR-B with or without DDR1. Cells with disrupted IGF-IR and expressing solely IR-A or IR-B will be also obtained. These cells will be investigated for their biology, ability to invade and acquire stem-like phenotype, and to grow and metastasize in vivo.

Both in vitro and in vivo experiments will be designed to elucidate how IR isoforms overexpression and the IR - DDR1 crosstalk impact on the metabolic derangement of breast cancer cells, and to identify combination therapies that take into account these non-canonical actions of IR. We expect to elucidate whether the two IR isoforms have different roles in breast cancer invasion, metastasis and metabolism derangement, and to clarify the biological role of the IR - DDR1 crosstalk in this context. We expect to identify a rationale for novel combination therapies for advanced breast cancer. The final aim of our proposal is to open a new perspective regarding IRs overexpression in advanced breast cancer.

These data will provide a rationale and an experimental basis for new individually tailored combination therapies, and might prove to be relevant to other cancer histotypes as well.