Fig. 2. Variant MSH3 expression and its consequences in tumor tissues.

A Microsatellite instability and EMAST in normal colon and tumor tissues. Two markers with mononucleotide repeats, 5 markers with dinucleotide repeats, and 7 EMAST markers were tested for instability in tumor DNA compared to normal colon DNA. Red arrows indicate new alleles found within tumor DNA. B IHC staining of MSH3 in normal colon and tumor tissues. The upper left and right images show normal colon and tumor tissue, respectively, that are positive for MSH3 IHC staining. The bottom left and right images show normal colon and tumor tissues from the index patient. Note that MSH3 is present in the cytoplasm and cell membrane in both the normal colon and tumor cells. Intense staining of MSH3 is seen in the cell membrane of some tumor cells. Scale bars are 10 micrometers. C Loss of MSH6 and reduced MSH2 in the patient’s MSH3 variant tumor cells. The consecutive FFPE slides were IHC stained with anti-MSH2, anti-MSH6, and anti-MSH3 antibodies. In some but not all tumor glands, simultaneous loss of MSH6 and reduced MSH2 was observed (areas circled in red). Scale bars are 10 micrometers.