TrkB expression level correlates with metastatic properties of L1 mouse sarcoma cells cultured in non‐adhesive conditions

Objectives

Ability of a cell to survive without adhesion, and to overcome anoikis, is indispensable for malignant cell invasion and metastasis formation. It has previously been shown that TrkB ‐neutrophin growth factor receptor might be involved in suppression of apoptosis, induced by the lack of adhesion. The aim of our study was to analyse changes in expression of genes and proteins as well as in biological properties of cancer cells cultured without adhesion. A mouse sarcoma, stable, adherent L1 cell line, derived from a spontaneously arisen Balb/c mouse lung tumour, was established in vitro.

Materials and methods

L1 cells resistant to anoikis were established by culture of L1 cells without adhesion, followed by selection of clones with elevated expression levels of TrkB protein. Biological characteristics of the cells were studied by migration/invasion tests and colony forming assay. Gene expression analysis was performed by with the aid of cDNA Gene Expression Array and Real‐Time PCR. In vivo experiments were conducted in syngeneic Balb/c mice.

Results

Significant changes in gene expression, including higher expression level of TrkB, were found in cells that were able to survive without adhesion. Selected TrkB‐expressing clones were found to have higher clonogenicity and invasive potential, formed more colonies in mouse lungs, and induced larger tumours, when injected subcutaneously into Balb/c mice.

Conclusion

Lack of adhesion induced significant changes in the cancer cells’ behaviour, which may result from alterations in gene and protein expression levels, including changes in anoikis‐connected protein – TrkB.