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Development of a small peptide, Foxy-5, mimicking the effects of Wnt-5a

The fact that Wnt-5a triggers several signalling pathways makes it difficult to identify a single intracellular signalling drug target suitable for reconstituting the effect of Wnt-5a in breast cancer cells that do not express the protein themselves.

Based on this, it is more logical to reconstitute the effect as early as possible in the signalling network activated by Wnt-5a.

In fact, the most effective target would be the receptor to which Wnt-5a binds at the cell surface.

Subsequently Foxy-5 has been documented not to affect proliferation or apoptosis of the mouse breast cancer cell line 4T1 derived from a spontaneous breast cancer in normal BALB/c mice. However, similar to previously published results on human breast cancer cells by Dr Andersson's group, Foxy-5 significantly inhibits 4T1 cell migration.


Foxy-5-induced inhibition of breast cancer cell migration

Following it was documented that Foxy-5 does not affect proliferation or apoptosis of the mouse breast cancer cell line 4T1 derived from a spontaneous breast cancer in normal BALB/c mice.

From a therapeutic point of view it would be much easier to direct a drug to a target on the surface of a cell than inside of a cell. Consequently, an attractive approach would be to administer Wnt-5a to breast cancer patients lacking the expression of this protein in their primary tumour, as revealed by a diagnostic histochemical analysis of their tumour biopsies.

The idea of administering Wnt-5a to a tumour-bearing individual in order to test its effect on tumour metastasis is, however, very unlikely to work. The reason being that Wnt-5a is a large protein and that it has a specific domain that binds to cell surface heparan sulfates which significantly limits the distribution of Wnt-5a in the body.

Therefore, we decided to develop a peptide that mimicked the effect of the intact Wnt-5a molecule on breast cancer cell migration. Based on sequence analysis of Wnt-5a, structural bioinformatics and computational chemistry design (performed through a collaboration with Dr. Villoutreix, INSERM, Paris), a short list of molecules were rationally proposed for in vitro assays. Two bioactive molecules were found and the smallest of these (12 amino acids long) was step-wise shortened from the N-terminal side. We found that when this peptide only contained 6 amino acids it had lost its bioactive properties. However, a chemical modification (formylation) restored its bioactive properties and made it more resistant to degradation in vivo. Thus, through a combined in silico-in vitro-in vivo work, Dr Andersson's research group found that this chemically modified 6-amino-acid peptide molecule could mimic the effects of Wnt-5a on breast cancer cell migration. This small compound was named Foxy-5.

However, similar to our previously published results on human breast cancer cells, Foxy-5 significant inhibits 4T1 cell migration.

The effects of Foxy-5 on tumour metastasis were tested in vivo in a mouse model (4T1 mice cells injected into the mammary pad of normal BALB/c mice). Inhouse results revealed that intraperitoneal injection of Foxy-5 reduced the metastatic burden in the lungs and in the liver by 70-90% in comparison to control animals. These results are extremely promising and Foxy-5 is currently in phase 1.

The Foxy-5 peptide is being tested in other situations including other types of cancer and non-cancer diseases. In parallel, we also work on making the Foxy-5 peptide more effective in the in vivo situation. One approach is to make modifications to the Foxy-5 peptide that will specifically target it to cancer tissues.

These research activities are ongoing in Tommy Andersson's laboratories. However, it would be premature to provide further details and evaluate the value of this explorative work.