The investigation of ING4 gene expression level and p53 gene mutations in pancreatic cancer tissues

Preamble: Pancreatic cancer is one of the intractable malignant tumors with a 5-year survival rate is under 1% and characterized by rapid metastatic progression and resistant to medical treatments and management. p53 is a tumor suppressor gene and mutated in more than 50% of pancreatic cancers. p53 protein is involved in several central cellular processes and ING family proteins are the proteins involved in the regulation of p53 activity such as the cell cycle control, DNA repair mechanism and programmed cell death. ING proteins sustain the stability by extending the half-life of p53 protein by competing with MDM2 for the same binding site on p53. It also enhance p53 acetylation at Lys-382 is an important processes in p53 protein oligomerization. The ING family proteins stimulates the expression of p21 by binding to p21 promoter. Like other ING family members, ING4 is involved in suppression of cell proliferation and chromosome stability by means of their PHD binding domains and also involved in cell migration through liprin ?1 and angiogenesis by way of NF-?B. Because of high mutation rate of p53 in pancreatic cancers and the role of ING4 on p53 stabilty and importance of cell migration and angiogenesis in metastasis of pancreatic cancer, p53 mutations and ING4 gene expressions and mutations have been studied. Material and methods: The pancreatic cancer tissues obtained were used for DNA and mRNA population extraction. p53 genomic DNA was analysed using appropriate primers for known mutations on the DNA fraction. The mRNA population obtained was converted to cDNA to study for ING4 variants again using appropriate primers. All PCR products were analyzed using agarose and acrylamide gel elctrophoresis followed by nucleotide sequence analysis. Results and Discussion: Our study has shown a decrease in gene expression of ING4 and its three splice variants of ING4 cDNA samples. Expected p53 gene mutations have not been observed as assessed by DNA sequencing analysis. Differing mobilites of p53 banding pattern were attributed to secondary structures that may cause to truncated mRNA synthesis which may results in disregulation of cell cycle and proliferation. Mutation in ß-actin gene may cause the cell cytoskeleton disruption and enhanced mobility in some pancreatic cancer tissues. Decreased expression of ING4 mRNA variants which were resulted due to alternative splincings (_v2 and _v4) involved in limited NLS regions of the gene that which restricts nuclear migration and cytoplasmic accumulation of ING4 proteins without triggering p53 and p21, in turn, disfunction of apoptosis and enhancing metastasis in addition to the loss of NLS accelerates the ubiquitination of ING4 in the cytosol and again uninduction of p53 translation. An initial onset of type2 diabetes mellitus in pancreatic cancer patients suggests the importance of cAMP and PI-3K pathways through histone acetylase, histone deasetylase and IGF, MAPK and p38. Thus, not all type2 diabetes susceptible to pancreatic cancer and along with genetic predisposition and habitual environment, studying the cellular locations and functions of ING4 splicing variants in pancreatic cancer due to different cellular functions of ING4 splicing variants, will explain beter the role of ING4 in pancreatic cancer.