Functional And Mechanistic Study Of LSD1 And G9a As A Therapeutic Strategy For Esophageal Cancer

Esophageal cancer is a common digestive tract tumor,which accounts for 2% of all malignant tumor types.Based on most recent cancer statistics,there are ? 300,000 people died from esophageal cancer every year worldwide.Since the mortality rate of esophageal cancer remains high,there is an urgent need to identify novel targets for esophageal cancer.In our study,we firstly screened epigenetic library and found that specific inhibitors of LSD1(SP2509)and G9a(BIX01294)could potently suppress cell growth of the majority of tested cancer cell lines.Further functional validation results revealed that the combination of these two compounds could synergisticly induce cell death of esophageal cancer cells.In addition,we demonstrated that the H3K4me2 and H3K9me2 levels were significantly increased upon treatment with LSD1 inhibitor,whereas the H3K9me2 levels were significantly decreased when treated with G9 a inhibitor.But when simultaneously inhibiting LSD1 and G9 a,the levels of H3K4me2 and H3K9me2 both were increased.Knockdown of LSD1 or G9 a could significantly suppress cell proliferation and promote cell death upon treatment with UNC0642 or SP2509 respectively.We found that the esopha geal cancer cells were arrested at S phase of cell cycle through downregulation of cyclin A and CDK2,and also induce potent cell apoptosis as evidenced by cleaved caspase3 and PARP.Notably,inhibition of LSD1 and G9 a could significantly suppress tumor cell growth of esophageal cancer xenografts in nude mice.Based on The Cancer Genome Atlas(TCGA)database,the RNA expression levels of LSD1 and G9 a are highly expressed in esophageal cancer tissues.Further,we performed immunohistochemical analysis on our esophageal cancer tissue microassay(TMA),which contains 114 cases of esophageal cancer tissues.We found that high expressed LSD1 and G9 a are positively correlated with poor prognosis in our esophageal cancer TMA.To explore potential molecular mechanism,we carried on RNA-seq analysis on esophageal cancer cells with or without inhibtion of either LSD1,or G9 a,or both by pharmacological or genetic inhibitory methods.ER-stress related pathways were significantly downregulated when inhibiting LSD1 and G9 a,which were functionally validated.Importantly,targeting ER-stress pathway could surpress esophageal cancer cell growth both in vitro and in vivo.Taken together,the findings of this study provide compelling evidence in support of LSD1 and G9 a as novel targets for treating esophageal cancer.