Showing papers by "Davide Ruggero published in 2017"

Noninvasive Measurement of mTORC1 Signaling with 89 Zr-Transferrin

Abstract: Purpose: mTOR regulates many normal physiological processes and when hyperactive can drive numerous cancers and human diseases. However, it is very challenging to detect and quantify mTOR signaling noninvasively in clinically relevant animal models of disease or man. We hypothesized that a nuclear imaging tool measuring intracellular mTOR activity could address this unmet need.Experimental Design: Although the biochemical activity of mTOR is not directly amenable to nuclear imaging probe development, we show that the transferrin receptor can be used to indirectly measure intracellular changes in mTOR activity.Results: After verifying that the uptake of radiolabeled transferrin (the soluble ligand of the transferrin receptor) is stimulated by active mTORC1 in vitro, we showed that 89Zr-labeled transferrin (Tf) can measure mTORC1 signaling dynamics in normal and cancerous mouse tissues with PET. Finally, we show that 89Zr-Tf can detect the upregulation of mTORC1 by tumor cells to escape the antitumor effects of a standard-of-care antiandrogen, which is to our knowledge the first example of applying PET to interrogate the biology of treatment resistant cancer.Conclusions: In summary, we have developed the first quantitative assay to provide a comprehensive measurement of mTOR signaling dynamics in vivo, in specific normal tissues, and during tumor development in genetically engineered animal models using a nuclear imaging tool that is readily translatable to man. Clin Cancer Res; 23(12); 3045-52. ©2016 AACR.

Abstract B11: Oncogenic KRAS regulates 4E-BP1, a repressor of cap-dependent translation, independently of growth factor activity

Abstract: Oncogenic mutations in K-Ras often occur at high frequencies in human cancer resulting in the sustained activation of the ERK1/2 mitogen-activated protein kinase (MAPK) signaling pathway. However, the unique dependencies on upstream or downstream oncogenic signaling amongst the mutant K-Ras proteins remains elusive and often masked by the remaining wild-type allele, other Ras isoforms, or additional secondary genetic alterations. Thus, we employed an isogenic mouse embryonic fibroblast (MEFs) system devoid of H-, N-, and K-Ras alleles and reconstituted with a single Ras isoform to examine the dependencies of growth factors on K-Ras mediated control of translational regulation. Although oncogenic K-Ras G12D and G12V mutant MEF lines proliferated at twice the rate of K-Ras4b wild-type MEF cells, growth factor deprivation led to a cytostatic effect on the proliferation of all MEF lines. Analysis of signaling downstream of K-Ras revealed that phosphorylation of 4E-BP1, eIF4E, and ERK1/2 occurred in a growth factor-independent manner, which stood in contrast to the substantive effects of growth factor inhibition on AKT, p70S6K, and ribosomal protein S6 phosphorylation. Moreover, growth factor deprivation resulted in a marginal decrease of global protein synthesis with negligible effects on cap-dependent translation initiation in all K-Ras MEF cell lines. Taken together, these data suggest that oncogenic K-Ras signaling regulates 4E-BP1 phosphorylation independently of growth factor and mTORC1/2 effects. Citation Format: Jillian M. Silva, Rachel K. Bagni, Davide Ruggero, Frank McCormick. Oncogenic KRAS regulates 4E-BP1, a repressor of cap-dependent translation, independently of growth factor activity. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr B11.