CHMP1B Acts As A Novel Oncogene To Promote The Development Of Pancreatic Cancer

Pancreatic cancer is known as the "king of cancer",with the highest mortality rate among all malignant tumors,and the five-year survival rate of the cancer patients is only 8%.The pathogenesis of pancreatic cancer is complex.There are 37 key mutated genes,including K-RAS(about 90%),TP53,transforming growth factor-β,hedgehog and other genes which are involved in the occurrence of pancreatic cancer.There are 172 tumorigenic genes abnormal overexpression in pancreatic cancer,which play an important role in the genesis of pancreatic cancer.The mechanism of pancreatic cancer has not been elucidated yet;therefore,the mechanism of pancreatic cancer pathogenesis has become an urgent scientific problem in the tumor research field to be solved.CHMP1B(charged multivesicular body protein 1B)belongs to the chromatin modified protein/charged multivesicular protein family,and its function is poorly understood at present.CHMP1B is necessary for phagosome maturation and effective transfer of autophagosomes to vacuoles in plant cells.CHMP1B plays an important role in the development of Drosophila.In tumors,the function of CHMP1B is not clear.It has been reported that the expression level of CHMP1B in esophageal squamous cell carcinoma is significantly higher than that in adjacent tissues.CHMP1B is considered as a target gene in breast cancer and may be used as a marker for breast cancer diagnosis.The expression of CHMP1B in other cancers has not been reported.We analyzed the difference of CHMP1B expression level between the 33 kinds of common malignant tumor tissues and the normal human tissues by bioinformatics analysis method and the big cancer database,the cancer genome atlas(TCGA).We found that the expression level of CHMP1B in the pancreatic cancer tissues was 5 times higher than that in the normal human pancreatic tissues.In view of the facts that CHMP1B promotes the development of Drosophila,cancer belongs to the "Atavism phenomenon",and cancer cells highly express the carcinoembryonic antigens which are overexpressed during embryonic development,we hypothesize that CHMP1B may function as a oncogene to promote the development of pancreatic cancer,and design research strategy and approach.We first measured CHMP1B gene expression level in 5 human pancreatic cancer cell lines and the tumor tissues from 23 clinical pancreatic cancer patients by PCR,then established CHMP1B gene-overexpressed and-silenced pancreatic cancer cell lines and tumor-bearing mice.We studied the effect of CHMP1B on tumorigenesis of pancreatic cancer at the three aspects:the impact of CHMP1B on tumorigenicity and mobility of pancreatic cancer cells,tumor growth in mice,and preliminary exploration of the molecular mechanism of CHMP1B in the development of pancreatic cancer.Through a series of experimental studies,we found that:(1)bioinformatics analysis of 33 types of common malignant tumors in cancer database data TCGA showed that CHMP1B was highly expressed in two kinds of malignant tumors,and the expression level in the pancreatic cancer tissue was 5 times higher than that in the normal tissue.Statistical analysis showed that there was a significant difference between the two groups(P<0.001).(2)The expression level of CHMP1B in clinical pancreatic cancer tumor tissue samples was three times higher than that in the adjacent tissues,and there was also a significant difference between the two groups(P<0.01).(3)Cell phenotypic study showed that the clone numbers of CFPAC-1 cells with high expression of CHMP1B were three times higher than that of control cells with low expression of CHMP1B;on the contrary,the clone numbers of pancreatic cancer Patu8988 cells with CHMP1B gene silence were 2.5 times lower than that of control Patu8988 cells,suggesting that the overexpression of CHMP1B enhanced the tumorigenicity of pancreatic cancer cells.(4)In the tumor-bearing mice,the tumor volume of CFP AC-1 cells with overexpression of CHMP1B was significantly larger than that of CFPAC-1 cells low expression of CHMP1B,suggesting that over expression of CHMP1B promotes tumor growth in vivo.(5)The migration and invasion ability of CFPAC-1 cells with overexpression of CHMP1B was four times and three times higher than that of control CFPAC-1,respectively;on the contrary,the migration and invasion ability of Patu8988 cells in which CHMP1B gene was silenced were four times and three times lower than that of control Patu8988 cells,suggesting that overexpression of CHMP1B enhances the mobility of pancreatic cancer cells.Based on these results,we conclude that CHMP1B acts as an oncogene to promote the initiation and development of pancreatic cancer.In addition,we also carried out preliminary molecular mechanistic studies regarded to CHMP1B-mediated tumorigenesis.The results showed that:(6)DNA microarray analysis showed that CHMP1B regulated the gene expression of pancreatic cancer cells.CHMP1B overexpression up-regulated the expression of tumorigenic FSTL15,TMPRSS15,FGB,and many other oncogenic genes,but down-regulated the expression of SPOCK1,RASSF8,DOK5,and senral other genes;(7)CHMP1B overexpression caused the phosphorylation of oncogenic SRC protein and STAT3 protein in CFPAC-1.When CHMP1B gene was silenced,the phosphorylation level of SRC and STAT3 protein decreased significantly,suggesting that CHMP1B may promote the development of pancreatic cancer cells through activating the tumorigenic SRC and STAT3 signaling pathways.In conclusion,we first found that CHMP1B has the tumorigenic function and is a new oncogene.Our findings get new insight into the molecular mechanism of the initiation and development of pancreatic cancer,provide a new molecular marker for the diagnosis of pancreatic cancer,and offer a new target for the development of cancer-targeted therapeutics against pancreatic cancer.Therefore,this study has theoretical significance and potential application value.