MLH1 and neoplasm: In addition, we performed MLH1 immunohistochemical staining in mouse tumor tissue from each group (ADV-MLH1 + CDDP-treated mice, ADV-NC + CDDP-treated mice) and observed that the ADV-MLH1 + CDDP-treated mouse tumor tissue was MLH1 positive, while the ADV-NC + CDDP-treated mouse group was MLH1 negative (Fig. 5d).