Oestrogens act as a driving force of both healthy and cancerous mammary cell growth by binding to receptors that include a type named GPER, which is generally located in cell membranes.

Recent studies have, however, revealed the unusual presence of this receptor in the nuclei of fibroblasts -- cells of the connective tissue -- surrounding mammary tumour cells.

Researchers at the University of Geneva (UNIGE), Switzerland, have discovered that this is in fact another version of GPER, a nuclear variant of this receptor, with different properties.

The fibroblasts carrying this variant promote the migration of neighbouring malignant cells, thus participating in the process of tumour metastasis.

This research, which may pave the way to a novel therapeutic strategy, is published in the journal Oncotarget.

Oestrogens play a crucial role in the genesis of the majority of breast cancers, promoting the survival, proliferation and invasiveness of tumour cells.

These hormones act by binding to their receptors, which fall into two groups, ER and GPER, whose properties differ.

The team of Didier Picard, professor at the Department of Cell Biology of the Faculty of Sciences of UNIGE, is interested in GPER receptors, whose effects on breast cancer are less well known than those of the ER family. "By analysing a breast tumour biopsy, our colleagues at the University of Calabria, who participated in this study, discovered GPER receptors in the nucleus of fibroblasts present around the malignant cells, whereas they had always been localised elsewhere before", says the biologist.

Fibroblasts, constituents of the connective tissue, are part of the microenvironment of the tumours.

"Knowing that cancer cells interact with neighbouring healthy cells to survive and grow, we wanted to find out whether the GPER receptors observed in the nucleus of these fibroblasts were involved in this process", explains Marco Pupo, first author of the study.

The researchers have discovered the existence of another version of GPER.

"This genetic variant results from a tiny change, a single nucleotide, in the gene that codes for the GPER receptor. This is sufficient to induce its relocation to the nucleus. We detected the presence of this same version of the gene in the fibroblasts of the eight other biopsies we analysed, from the University Hospital of Geneva", states Didier Picard.

Source:  University of Geneva