Differentiation-suppressive polypeptide serrate-2 and methods of use

Patent Number: 7,138,276

Notch is a receptor for Delta and Serrate that is found in Drosophila and involved in controlling nerve cell differentiation during development. The human equivalent of Notch is called TAN-1, and is expressed on hematopoietic stem cells.

Other patents have used Notch ligand homologues to stimulate fetal hemoglobin synthesis as well as to expand multipotent stem cells without inducing differentiation

This patent has identified novel compositions of matter that act through the TAN-1 receptor, but appear to be distinct from the previously identified human Delta and human Serrate.

This patent has 5 independent claims. The first two cover inhibiting differentiation of undifferentiated cells by contacting the cells with a polypeptide that is represented as Sequence ID #2 and #3. Notice that in this patent the inventors only claimed “isolated” polypeptide, whereas in the 7,138,492 patent the polypeptides claimed were “isolated/or recombinantly expressed”. In any case, the third and forth independent claims are directed towards inhibiting proliferation of vascular endothelial cells by contacting cells with the isolated polypeptides represented in ID#2 and #3. The fifth independent claim covers inhibiting the proliferation of a vascular cells, purposely omitting the word “endothelial”. Dependent claims for the first and second independent claims define undifferentiated cells as cells that are not brain, nervous system, or muscle cells, and further define the undifferentiated cells as cells that are undifferentiated blood cells.

The patent has several examples supporting the claims. Most notably in our minds are the following:

1. Example 8: Effects of Human Serrate-2 Protein on Colony Formation of Blood Undifferentiated Cells. Bone marrow and cord blood purified CD34 cells were cultured in methylcellulose. The cells were culture with or without human Serrate-2 extracellular Ig chimera protein (EXS2Fc). The concept being that if the CD34+ cells differentiate they will form colonies which are visible. If they do not differentiate then the treated sample will have less colonies. The data showed that there were less colonies in the cells treated with EXS2Fc.

2. Example 9: Effect of Human Serrate-2 on Blood Undifferentiated Cell LTC-IC in Liquid Culture. This example measured the output of cells from a long term culture. The inventors suggest that because there was less cells output, there was less differentiation. But this does not actually demonstrate that the stem cell numbers expanded. We at StemCellPatents.com invite clarification for this example, because from what we see there is only inhibition of output but no evidence that the primitive stem cells are proliferating. Based on the data, if we understood it correctly, the other conclusion could be that the cells are dying.

View this patent on the USPTO website.