Correlation between MLH1 methylation and distant metastasis of solid pseudopapillary tumor of pancreas / 中华肝胆外科杂志

ABSTRACT

Objective:To investigate the significance of MLH1 protein expression and MLH1 gene methylation rate between metastatic solid pseudopapillary tumor of pancreas (SPT) and non-metastatic SPT, and to explore the correlation between MLH1 gene methylation and SPT metastasis.Methods:Twelve metastatic SPT patients admitted to Peking University People's Hospital, Rizhao Central Hospital and Chaoyang Central Hospital of Liaoning Province from January 2009 to May 2022 were studied retrospectively, including 3 males and 9 females, with a median age of 47 years old, ranging from 21 to 73 years old. Thirty non-metastatic SPT patients with clear diagnosis, clear medical history and complete follow-up data from pathological database of Peking University People's Hospital from January 2009 to May 2017 were selected as the control group, including 12 males and 18 females, with a median age of 42 years old, ranging from 34 to 69 years old. Clinical data such as gender, age and pathological data were collected. Immunohistochemical expression of MLH1 protein and methylation of MLH1 gene were detected by pathological paraffins.Results:There was no significant difference in general data between the two groups (all P>0.05). Among the 12 metastatic SPT patients, 4 cases metastasized to liver, 2 to spleen, 2 to lung, 2 to lymph nodes, 1 to mediastinum, and 1 to sacrum. Compared with the non-metastatic tissue, the MLH1 protein deletion in metastatic pancreatic lesions (metastatic SPT-P) and metastatic lesions (metastatic SPT-M) were increased [both 33.3%(4/12)], and the difference was statistically significant (both Chi square=5.00, both P=0.041). Compared with 0 (0/30) MLH1 gene methylation rate in non-metastatic SPT tissues, the methylation rate of MLH1 gene in metastatic SPT-M and metastatic SPT-P tissues [both 30% (3/10)] were higher, with statistical significance (both Chi square=0.96, both P=0.032). Conclusion:Compared with non-metastatic SPT, the loss rate of MLH1 protein expression and MLH1 gene methylation are increased in metastatic SPT. MLH1 methylation may occur before metastasis, which can be used as a predictor of SPT metastasis.