CMIP Is An Oncogene In Human Gastric Cancer Cells

Gastric cancer is the second leading malignant tumor.The early clinical symptoms are not obvious;so many patients with gastric cancer are easy to be misdiagnosis and missed diagnosis.The majority of patients with gastric cancer were diagnosed at an advanced stage.Surgical resection followed by adjuvant chemotherapy and radiotherapy is still the main treatment for gastric cancer patients.Recurrence,distant metastasis and resistance to drug treatment are the main barrier to survival of patients with advanced stage gastric cancer.At present,personalized treatment for malignant tumors has become hot,and some targeted therapies have begun to be applied in clinical practice.Specific antibody drug Herceptin for human epidermal growth factor receptor-2(HER-2)has been used for gastric cancer patients with positive HER-2 expression.However,there are still few targets for the treatment of gastric cancer,and targeted therapy drugs still need to be further developed.Further research is necessary and urgent.Therefore,further study of the molecular mechanisms of gastric cancer may improve the diagnosis and treatment of gastric cancer,and improve the survival rate and quality of life in gastric cancer patients.In a previous study,c-Maf was discovered as an oncogene transduced in the avian AS42 retrovirus,which was discovered to be overexpressed in multiple myeloma and angioimmunoblastic T-cell lymphoma.c-Maf inducing protein(CMIP)is an adaptor protein with two isoforms,which is involved in the c-Maf signaling pathway.The two isoforms of CMIP were observed to be expressed in the human brain.One of the isoforms is a short protein that participates in several cell-signaling pathways and was reported to be associated with minimal change nephrotic syndrome(MCNS).The second isoform of CMIP is a longer protein,for which there is limitedfunctional information at present.In kidney-associated diseases,CMIP regulates the behavior of podocytes.Recent researchs demonstrated that CMIP was associated with reading and language related traits,which also contributed to classical Hodgkin lymphoma.However,the relationship between CMIP and human gastric cancer has not yet been reported.Therefore,the present study examined the role of CMIP in human gastric cancer,IHC analyses were performed on 100 gastric cancer tissue specimens and 100 normal gastric tissue specimens.The positive rate of CMIP protein expression was 72% in the gastric cancer tissues,whereas 48% of the normal gastric tissues positively expressed CMIP(P<0.001).The association of CMIP expression with gastric cancer prognosis was evaluated.Positive expression of CMIP was associated with tumor size(P=0.013),lymph node metastasis(P=0.002),histological grade(P=0.010)and clinical stage(P=0.029)in gastric cancer.Patients with primary tumors expressing CMIP protein had a significantly poorer RFS and OS compared with those without CMIP protein expression(P=0.001 and P=0.002,respectively).Furthermore,using Western blot analysis,cell counting,Cell Counting Kit?8,colony formation,wound healing and Transwell assays,together with flow cytometry,CMIP depletion by RNA interference was observed to reduce the capacity of gastric cancer cells to proliferate and migrate in vitro(P<0.05).In conclusion,CMIP demonstrated an oncogene role in human gastric cancer cells.MicroRNAs(mi RNAs)are non?coding RNAs consisting of 20?25 nucleotides,which were identified to serve important roles in the initiation,development,growth,proliferation and metastasis of human cancer,including gastric cancer.For investigating the downstream pathway,Target Scan release 7.1 was used to identify the potential miRNAs for CMIP?targeting.The TargetScan analysis indicated that CMIP may be a target gene of miR?101?3p.RT?qPCR was performed to detect the miR?101?3p expression levels in gastric cancer tissues and normal gastric tissues(P<0.05).The results indicated that miR ? 101 ? 3p was significantly downregulated in gastric cancer tissues.A dual luciferase reporter assay indicated that CMIP may be a direct target of miR?101?3p in gastric cancer MKN?28 cells.Tofurther investigate the effects of miR?101?3p,Western Blot was performed to detect the protein expression of CMIP in MKN-28 cells treated with the miR?101?3p mimic.The results showed that overexpression of miR?101?3p reduced the protein level of CMIP(P<0.05).To obtain further insight into the role of CMIP in MKN?28 cell invasion and metastasis,the expression of several mRNAs(including cell cycle control and DNA damage repair genes MDM2,CHEK2 and RB1,apoptosis and cell senescence genes BAX,BAD and CFLAP and signal transduction molecules and transcription factors MAPK,FOS and NFKB1)was assessed using RT ? qPCR in siCMIP ? transfected MKN ? 28 cells,compared with si ? NC transfected cells(data not shown).Two downregulated genes(MDM2 and MAPK)were identified in siCMIP ? transfected MKN?28 cells.The results demonstrated that mRNA levels of MDM2 and MAPK were downregulated following CMIP knockdown in gastric cancer MKN ? 28 cells(P<0.05).In conclusion,the present study demonstrated a tumor?promoting function of CMIP in the MKN?28 cell line.MiR-101-3p,MDM2 and MAPK were involved in the promoting role of CMIP in gastric cancer.In patients with gastric cancer,expression of CMIP was associated with poorer clinical parameters,RFS and OS.These results suggest that CMIP may be a novel therapeutic target for gastric cancer;however further studies are required to investigate this.