title: A-kinase anchor protein 4 (AKAP4) a promising therapeutic target of colorectal cancer.
abstract: BACKGROUND
  Colorectal cancer (CRC) ranks third among the estimated cancer cases and cancer related mortalities in the Western world. Early detection and efficient therapy of CRC remains a major health challenge. Therefore, there is a need to identify novel tumor markers for early diagnosis and treatment of CRC.
  
  
  METHODS
  A-kinase anchor protein 4 (AKAP4) gene and protein expression was monitored by quantitative polymerase chain reaction (qPCR), reverse transcription (RT)-PCR and Western blotting in normal colon tissue lysate, normal colon epithelial cells and in colon cancer cell lines viz., Caco-2, COLO205, COLO320DM, HCT-15, HCT116, HT-29, SW480, and SW620. The effect of AKAP4 on cellular growth, migration and invasion abilities was studied using gene silencing approach. The role of AKAP4 in various pathways involved in cell cycle, apoptosis, senescence was investigated in in vitro and in human xenograft mouse model.
  
  
  RESULTS
  Our studies showed that AKAP4 gene and protein expression was expressed in all colon cancer cells while no expression was detectable in normal colon cells. Ablation of AKAP4 led to reduced cellular growth, migration, invasion and increased apoptosis and senescence of CRC cells in in vitro assays and tumor growth in human xenograft mouse. Human colon xenograft studies showed a significant decrease in the levels of cyclins B1, D and E and cyclin dependent kinases such as CDK1, CDK2, CDK4 and CDK6. Interestingly, an up-regulation in the levels of p16 and p21 was also observed. Besides, an increase in the levels of pro-apoptotic molecules AIF, APAF1, BAD, BID, BAK, BAX, PARP1, NOXA, PUMA and cyt-C and Caspase 3, 7, 8 and 9 was also found in cancer cells as well as in xenograft tissue sections. However, anti-apoptotic molecules BCL2, Bcl-xL, cIAP2, XIAP, Axin2 and Survivin were down regulated in these samples. Our data also revealed elevated expression of epithelial marker E-cadherin and down regulation of EMT markers N-cadherin, P-cadherin, SLUG, α-SMA, SNAIL, TWIST and Vimentin. Further ablation of AKAP4 resulted in the down regulation of invasion molecules matrix metalloproteinase MMP2, MMP3 and MMP9.
  
  
  CONCLUSIONS
  AKAP4 appears to be a novel CRC-associated antigen with a potential for developing as a new clinical therapeutic target.
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. Nirmala.jagadish@yahoo.in.
authors.forename: Nirmala
authors.initials: N
authors.lastname: Jagadish
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. deepak0913@gmail.com.
authors.forename: Deepak
authors.initials: D
authors.lastname: Parashar
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. guptanamita65@yahoo.com.
authors.forename: Namita
authors.initials: N
authors.lastname: Gupta
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. sumita0913@gmail.com.
authors.forename: Sumit
authors.initials: S
authors.lastname: Agarwal
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. gplsapna@gmail.com.
authors.forename: Sapna
authors.initials: S
authors.lastname: Purohit
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. gplvikash@gmail.com.
authors.forename: Vikash
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. gpladiti@gmail.com.
authors.forename: Aditi
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. gplrukhsar@gmail.com.
authors.forename: Rukhsar
authors.initials: R
authors.lastname: Fatima
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. gplamosprashant@gmail.com.
authors.forename: Amos Prashant
authors.initials: AP
authors.lastname: Topno
authors.affiliation: Cell Death and Differentiation Research Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. cshahagpl@gmail.com.
authors.forename: Chandrima
authors.initials: C
authors.lastname: Shaha
authors.affiliation: Cancer Microarray, Genes and Proteins Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, 110 067, India. anil@nii.res.in.
authors.forename: Anil
authors.initials: A
authors.lastname: Suri
mesh_terms: D054758:A Kinase Anchor Proteins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000235:genetics; D017209:Apoptosis / Q000235:genetics; D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D018938:Caco-2 Cells; D049109:Cell Proliferation / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D051379:Mice; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D023041:Xenograft Model Antitumor Assays
chemical_list: D054758:A Kinase Anchor Proteins; C485480:AKAP4 protein, human; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins