Abstract 1232: Regulation of ARHI and p53 gene on the programmed cell death of oral cancer cells
Authors: Li Yi , Shi Shan-Wei , Li Chun-Jie , Han Bo , Li Long-Jiang 
Published: August 2015

Background: Oral cancer is one of the most common diseases which severely threaten human health. As a “gate-keeper” gene, p53 plays a significant role in promoting apoptosis of cancer cells. Meanwhile, it has been showed that ARHI (aplasia ras homologue member I) gene could regulate the autophagy of cancer cells to promote the programmed cell death. The present study was aimed to research the regulation of ARHI and p53 gene on the programmed cell death of oral cancer cells.

Study Design: Firstly, the expression of ARHI gene was tested in the normal tissues and oral cancer cells. Then, we transfected wild-type p53 and ARHI gene by the recombinant adenovirus into the oral cancer cell line (Cal-27) and evaluated the levels of apoptosis by cell morphology, flow cytometry and TUNEL assay. After that, the evaluations of autophagic levels were carried out by the transmission electron microscope, and by the expression of LC3B via immunofluorescence and western-blot. The functions of P53 and ARHI gene were evaluated by the key factors in PI3K-Akt pathway and the downstream proteins. Finally, we testified the results of cellular researches by a xenograft mouse model.

Results: The expressions of ARHI gene were lower in oral cancer cells than that in normal tissues. The mRNA and protein expressions of p53 and ARHI increased substantially in Cal-27 cells after gene transfections, and the expressions of bcl-2,bax, p21, stat3 were changed accordingly, which verified the activation of the two genes function. It was noteworthy that the expression of p53 gene could rise by the ARHI gene transfection while the expression of ARHI could not, which showed that ARHI could be the upstream factor of p53. It was found that the programmed cell death was promoted in Cal-27 cells 48 hours after the gene transfections, which was shown as the cytoplasmic condensation and nuclear shrinkage. In the same time, the proliferation rates of Cal-27 cells decreased, and apoptosis increased significantly. The autophagic progresses were increased initially, but were blocked in the following steps. The phosphorylation of Akt in sites of Thr308 and Ser473 were decreased after gene transfections. The phosphorylation of 4E-BP1 was decreased to enhance the binding rate between 4E-BP1 and eIF4E, and expressions of the downstream functional factors, such as c-myc, cyclin D1, bcl-2, FGF, VEGF, EGFR, were decreased. The tumor growth curves were decreased tremendously after intra-tumoral injection of p53 and ARHI recombinant adenovirus in the animal models, which were consistent with cellular studies.

Conclusion: P53 and ARHI could inhibit the phosphorylation of key factors in PI3K-Akt pathway, thus restraining the expressions of functional factors to promote programmed cell death in oral cancer.

Citation Format: Yi Li, Shan-Wei Shi, Chun-Jie Li, Bo Han, Long-Jiang Li. Regulation of ARHI and p53 gene on the programmed cell death of oral cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1232. doi:10.1158/1538-7445.AM2015-1232