The phospho-c-Jun content in gastric mucosa cells under experimental gastric carcinogenesis

Tymoshenko M.O., Kravchenko O.O., Ostapchenko L.I.

M. Tymoshenko, O. Kravchenko, L. Ostapchenko

Taras Shevchenko Kyiv National University, Educational and Scientific Center “Institute of Biology”, Kyiv, Ukraine

Introduction: The protein c-Jun belongs to the subgroup of DNA binding transcription factors that form AP-1 dimers. c-Jun is unique in its ability to positively regulate cell proliferation through the repression of tumor suppressor gene expression and function, and induction of cyclin D1 transcription. c-Jun is phosphorylated on Ser63 and Ser73 following activation of signalling cascades, which made c-Jun maximally effective in stimulating transcription. However, the exact role of c-Jun in gastric oncogenesis is unknown. Aim: To determine the phosphorylated form of c-Jun content in the lysate of rat gastric mucosa cells in chemically induced gastric cancer development. Methods: The content of phospho-c-Jun was measured by Sandwich ELISA method using the assay kit PathScan Phospho-c-Jun (Ser63) (Cell Signaling Technology, USA) and represented in conventional unit of absorbancy on mg of the protein. The protein concentration was registered by Bradford’s method. Gastric carcinogenesis was initiated by 10-week replacement of drinking water by 0.01% solution of carcinogen N-methyl-N’-nitro-N-nitrosoguanidine (MNNG), at the same time the rats were redefined on diet containing 5% NaCl. The samplings of material were performed at the end of 4th, 6th, 8th, 10th, 12th, 18th and 24th week. The study protocol was approved by Ethical Committee permission of Educational and Scientific Center “Institute of Biology” (Kyiv, Ukraine). Results: At the end of the 4th week of MNNG and NaCl consumption the control reference of phospho-c-Jun content was observed. The gastric mucosa cells were characterized by increased content of phospho-c-Jun at 4 and 6.3 fold over the control at the end of 6th and 8th weeks, respectively, of the of MNNG and NaCl treatment. Also it was established that the MNNG and NaCl treatment for 10 weeks causes 1.9-fold increase in phospho-c-Jun content compared to the control. At terminal stages (12, 18 and 24 weeks) of the gastric carcinogenesis study there was a stable increase of phospho-c-Jun content on the average at 3.6-fold in comparison with reference values. Conclusions: The increased level of the phosphorylated form of c-Jun from 6th to 24th week of gastric cancer development was probably caused by activation of MAP-kinase cascade and inactivation of phosphatases that would lead to the intensification of target genes transcription responsible for cell proliferation.

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