Differential Effect of Novel Plant Cystatins on the Adhesive Behaviour of Normal and Cancer Breast Cells

In the present work, we have investigated a novel recombinant cystatin dgECP1 and its mutant form, dgECP1m1, focused on their impact on the adhesive behaviour of two breast cell lines: the cancerous, MDA-MB-231, and the normal, MCF-10A. DgECP1 cystatin is intriguing with its RGD motif, responsible for cell adhesion and typical for mammalian extracellular matrix proteins but uncommon for plant cystatins. The presence of the RGD sequence suggests the potential of the dgECP1 to influence the adhesion of cancer cells and, respectively, cancer metastasis. A mutant form of the dgECP1cystatin, dgECP1m1, where RGD is replaced with HGD tripeptide, was also investigated. We found that both phytocystatins exerted differential effects on the adhesion behaviour of normal and cancer cells. In the case of dgECP1 cystatins, the effect on cancer cell adhesion also depends on the mode of administration of the cystatin to cells. When dgECP1 is pre-adsorbed on a substrate, it improves the attachment of breast cancer cells and induces cell aggregation, which is more typical for normal breast cells, and oppositely suppressed adhesion of cancer cells when added to the medium. The mutant form, dgECP1m1, inhibited cancer cell adhesion independently on the way of administration. On the other hand, both plant cystatins only slightly reduced the adhesion of normal mammary cells pointing to the higher sensitivity of cancer cells to both cystatins. These preliminary results open the possibility of considering the plant cystatin dgECP1 for anti-cancer strategies.