Abstract 5480: Expression and function of EVI1 and EVI1s (Δ324) ovarian cancer
Authors: Jazaeri Amir A. , Ferriss James S. , Machida Yuichi , Dalton Susan , Bryant Jennifer L. , Dutta Anindya 
Published: February 2011

Objective: The MDS1 and EVI1 complex locus (MECOM) located at the 3q26 locus is amplified in many cancers and gives rise to a number of alternatively spliced transcripts and proteins including EVI1 and MDS1-EVI1 (ME). EVI1 functions as an oncogene in human and murine myeloproliferative disorders and myelogenous leukemias. Amplification and over expression of EVI1 and ME have been demonstrated in ovarian cancers, and these proteins have been proposed as potential therapeutic targets that may also play a role in chemoresistance. Our objective was to evaluate the expression and biological function of EVI1 and one of its splice isoform known as EVI1s or Δ324 in ovarian cancer.

Methods: Expression of EVI1 isoforms was evaluated in serous ovarian cancer samples, normal ovaries, benign ovarian neoplasms, and fallopian tube fimbria (emerging as the likely site of origin of many serous ovarian cancers) using realtime RT-PCR, and immunoblotting. Alterations in EVI1 and EVI1s expression were induced by retroviral transduction and isoform selective siRNA. Proliferation was measured using MTT and BrdU assays. Dose response to paclitaxel and cisplatin was measured following isoform selective knockdown of EVI1 and EVI1s using a histone release apoptosis ELISA.

Results: EVI1 and EVI1s transcripts were present in normal ovaries, fimbria, benign ovarian neoplasms, and papillary serous ovarian cancers, with highest expression of both isoforms noted in the ovarian cancer samples. There was no change in relative expression of EVI1s among the different tissue types examined. In contrast, EVI1 protein isoforms were essentially undetectable in normal ovarian tissues. While highest average expression of ME, EVI1, and EVI1s protein isoforms was observed in serous ovarian cancer samples, considerable variability was noted between different serous ovarian cancer samples. In addition, variable expression of the same EVI1 protein isoforms was also observed in normal fallopian tube fimbria and several benign ovarian neoplasms. Forced expression of EVI1 and EVI1s did not result in any increased proliferation in OVCAR8 ovarian cancers (that lack endogenous EVI1 expression) nor in HEK293T cells. Furthermore, no effects on proliferation were observed following knockdown of EVI1, EVI1s, or all EVI1 transcripts. In dose response assays there was no significant effect on cisplatin and paclitaxel induced apoptosis following EVI1 knockdown. Daunorubicin induced DNA damage as determined by phospho-H2AX expression was also unaltered following isoform selective EVI1 siRNA.

Conclusion: There is a lack of correlation between EVI1 transcript and protein isoforms in gynecologic tissues. Our results suggest that EVI1 protein expression in some serous ovarian cancers may be related to their derivation from fallopian tube origin, and that alteration of EVI1 and EVI1s protein levels doesn't influence ovarian cancer cell growth, apoptosis, or response to chemotherapy.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5480.