Figure 3. DNA sequencing analysis of some MMR-target coding mononucleotide repeats, and IHC for MMR proteins in primary colorectal cancer tissues or spheroid samples in MSI-H and MSI-L/MSS colorectal cancer cases.

(A) DNA sequencing data that cover the mononucleotide repeat regions amplified from the spheroid-derived DNA samples for TGFBR2, BAX, IGF2R, and CASP5. For all markers, the reverse strands of the wild types (top panels), and homozygous (middle) and heterozygous (bottom) mutants are shown. No cases were found with IGF2R homozygous mutation. (B) Immunohistochemistry for mismatch repair (MMR) proteins, MLH1, MSH2, MSH6, and PMS2. The colorectal cancer (CRC) HC10T (top panels) shows a MMR-proficient (MMRp) example of the primary CRC section (Primary tumor), with expression of all MMR proteins. The CRC HC4T (bottom panels) shows a MMR-deficient (MMRd) case. Expression of MLH1 and PMS2 was not detected in the primary tumor tissue. Notably, IHC of spheroid cells derived from the same tumors mirrored the results with the whole tumor sections. Note that some staining of MLH1 and PMS2 in HC4T primary CRC sections is in the stromal cell nuclei.