Abstract 4897: Involvement of Akt isoforms in chemoresistance of carcinoma endometrial cells

Abstract

Akt (also known as PKB) is a crucial survival kinase that is normally activated by growth factors, but in tumors, it is constitutively activated at a high frequency through oncogenic events affecting its upstream regulation. Since studies have demonstrated that the three Akt isoforms exhibit distinct physiological functions, we propose that Akt isoforms may contribute differently in chemoresistance of endometrial carcinoma cells. In order to determine the specific role of each Akt isoform, we have stably produced transfectants in which the expression of Akt is downregulated by specific shRNAs for Akt1, Akt2 and Akt3 using the KLE endometrial carcinoma cell line. This endometrial cell line is known to constitutively express the three Akt isoforms and to highly resist to chemotherapeutic treatment. In this study, we have demonstrated that the downregulation of Akt1 and Akt2 by RNA interference strongly sensitizes KLE cells to cisplatin, doxorubicin and taxol and affects cell proliferation. Moreover, cisplatin treatment of these cells induced the activation of pro-apoptotic factors such as the cleavage of caspase -3, -6, -9 and PARP and it also inhibited the expression of anti-apoptotic factors such as XIAP and Bcl-2. Alternatively, we used constitutively active Akt expression vectors for each isoform to produce stable transfectants using the chemosensitive Hec 1A endometrial cancer cell line, in which no Akt activity is detected. Constitutive Akt1 and Akt2 expression leads to an increase in cell proliferation, as well as resistance to apoptosis after chemotherapeutic treatment in these stable transfectants. Moreover, Akt isoforms contribute differently in other cancer cell processes, such as migration. We showed that Akt2 blocks cell motility, while the activation of Akt1 or Akt3 does not show any effect on our endometrial cancer cell model. Our findings highlight the contribution of Akt1 and Akt2 isoforms in the molecular mechanisms that govern chemoresistance of endometrial carcinoma. Furthermore, Akt isoform-specific transfectants will provide a solid model to determine the involvement of each Akt isoform in tumor progression and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4897. doi:1538-7445.AM2012-4897