Also, no neuroendocrine differentiation was acquired in vitro based on chromogranin A. Interestingly, the colon cancer cell line and the parental primary tumor from patient 3 showed a loss of expression of DNA mismatch repair proteins MLH1 and PMS2 in the tumor cells, suggestive for microsatellite instability. The gene discussed is MLH1; the disease is malignant colon neoplasm.