Abstract IA15: The consequences of pRb inactivation: insights from a proteomic analysis of Rb loss

Abstracts: AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; February 28 - March 2, 2016; Orlando, FL The retinoblastoma tumor suppressor protein associates with chromatin and regulates gene expression. The transcriptional signatures associated with RB1/Rb mutation are thought to give a picture of the cellular changes that occur when pRB is lost. We used proteomic profiling to examine the changes caused by the ablation of Rb in mouse lung and colon tissues, and compared these with transcript profiles. While the transcription of classic E2F target genes increased similarly in Rbko lung and colon, effects on protein levels were context-dependent. Proteomic changes were identified that were similar between Rb-mutant tissues but, unexpectedly, the major feature of these changes was a decrease in proteins that function in mitochondria. Consistent with this, mutation of RB1 in cultured human cells reduced the number of mitochondrial number and caused mitochondrial dysfunction. Rbko cells had reduced oxygen consumption rate, reduced reserve capacity, an accumulation of depolarized mitochondria and displayed an altered flux of Carbon through the TCA cycle that was evident both in vivo and in vitro. These defects impair cell proliferation under conditions of mitochondria stress. Collectively, these results suggest that the most consistent changes in the proteome of Rbko tissues may not stem from changes in the levels of cell proliferation proteins, but from changes in mitochondrial function. Analysis of transcripts that are induced in Rbko tissues without a corresponding change in protein levels suggests that there may be a mechanism of post-transcriptional control that coordinately suppresses E2F-induced mRNAs. Citation Format: Brandon N. Nicolay, Paul S. Danielian, Filippos Kottakis, John D. Lapek, Jr., Ioannis Sanidas, Wayne O. Miles, Mantre Dehnad, Katrin Tschop, Jessica J. Gierut, Amity L. Manning, Robert Morris, Kevin Haigis, Nabeel Bardeesy, Jacqueline A. Lees, Wilhelm Haas, Nicholas J. Dyson. The consequences of pRb inactivation: insights from a proteomic analysis of Rb loss. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr IA15.