Abstract
Abstract Ribonucleotide reductase subunit M2 (RRM2) is an essential regulator of DNA synthesis and replication that plays an active role in tumor progression. B-cell lymphoma-2 (Bcl-2) is an anti-apoptotic protein known to promote cell survival. Elevated levels of Bcl-2 have been observed in many cancer types that predict clinical drug resistance. Both RRM2 and Bcl-2 were identified as prognostic factors and indicators of poor patient outcome in several cancers. Therefore, we hypothesized that RRM2 and Bcl-2 proteins might have cooperative functions in cancer progression. We examined correlations of RRM2 and Bcl-2 protein in tissue samples of head and neck squamous cell carcinoma (HNSCC) and non small cell lung cancer (NSCLC) patients by using quantum dots (QDs)-immunofluorescence (IHF) which allows quantification of biomarkers simultaneously in the same tissue slide. A total of 19 cases in each of HNSCC and NSCLC were analyzed. Spearman's correlation coefficient was estimated to measure the relationship between these two proteins. Our data demonstrate highly significant positive correlation between RRM2 and Bcl-2 in both types of cancer (HNSCC: R=0.98, p-value <0.0001; NSCLC: R=0.85, p-value <0.0001). We further investigated the action mechanism of RRM2 and Bcl-2 in cancer progression and explored the role of RRM2 by utilizing siRNA-mediated gene silencing. siRNA knockdown of RRM2 strongly inhibited cell growth and led to apoptosis. Our results demonstrated that overexpression of Bcl-2 protected cells from apoptosis triggered by RRM2 knockdown, indicating that Bcl-2 is a key determinant in controlling intrinsic apoptosis. We further analyzed whether Bcl-2 was regulated by RRM2 at the transcriptional level or at the protein level by post-translational modification. RRM2 most likely regulates Bcl-2 not only at a transcriptional level but also at the post-translational level. We found that RRM2 and Bcl-2 proteins were co-localized and directly interacted. RRM2 depletion significantly increased the rate of Bcl-2 protein degradation, reducing its half-life from ∼9 hours to ∼2 hours. Our study offers a promising approach to Bcl-2 inhibition through targeting RRM2 with siRNA in HNSCC and NSCLC. A protein network-based functional mechanism is defined by which RRM2 regulates Bcl-2-mediated apoptosis. Our novel findings add to the emerging regulatory effects of RRM2 on tumor growth by modulation of Bcl-2. (This work is supported by grants from NIH U01CA151802, P50CA128613 and DOD W81XWH-07-1-0306). 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 2004. doi:1538-7445.AM2012-2004
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
