Temporal dynamics of Wnt-dependent transcriptome reveal an oncogenic Wnt/MYC/ribosome axis
Babita Madan, … , Enrico Petretto, David M. Virshup
Babita Madan, … , Enrico Petretto, David M. Virshup
Published October 9, 2018
Citation Information: J Clin Invest. 2018;128(12):5620-5633. https://doi.org/10.1172/JCI122383.
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Research Article Cell biology Oncology

Temporal dynamics of Wnt-dependent transcriptome reveal an oncogenic Wnt/MYC/ribosome axis

Abstract

Activating mutations in the Wnt pathway drive a variety of cancers, but the specific targets and pathways activated by Wnt ligands are not fully understood. To bridge this knowledge gap, we performed a comprehensive time-course analysis of Wnt-dependent signaling pathways in an orthotopic model of Wnt-addicted pancreatic cancer, using a porcupine (PORCN) inhibitor currently in clinical trials, and validated key results in additional Wnt-addicted models. The temporal analysis of the drug-perturbed transcriptome demonstrated direct and indirect regulation of more than 3,500 Wnt-activated genes (23% of the transcriptome). Regulation was both via Wnt/β-catenin and through the modulation of protein abundance of important transcription factors, including MYC, via Wnt-dependent stabilization of proteins (Wnt/STOP). Our study identifies a central role of Wnt/β-catenin and Wnt/STOP signaling in controlling ribosome biogenesis, a key driver of cancer proliferation.

Authors

Babita Madan, Nathan Harmston, Gahyathiri Nallan, Alex Montoya, Peter Faull, Enrico Petretto, David M. Virshup

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Figure 7

Wnt-regulated cell-cycle changes are only partially influenced by MYC.

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Wnt-regulated cell-cycle changes are only partially influenced by MYC. (...
(A) Robust changes in the expression of representative cell-cycle genes over 7 days of PORCN inhibition in HPAF-II orthotopic xenografts. The dotted line is at 1.5-fold (log2, 0.58). (B) Significant decrease in proliferating cells over time. Ki67-positive cells (left) were quantitated (right) on an entire section that was scanned and analyzed using NIS-Elements software. Two-tailed Mann-Whitney U test was used to calculate significant differences. (C) CCND1 protein changes more robustly compared with mRNA. Blots from Figure 4C were reprobed as indicated. CCND1 mRNA decreases 33% (see A and D), while CCND1 protein decreases approximately 65% after 56 hours treatment in both HPAF-II and CRC PDX models. Each lane is from an independent tumor. Ratios of CCND1 levels to β-actin levels for each lane are indicated. ETC-159 treatment reduces levels of pRb (S780) in both HPAF-II tumors and CRC PDX. Note the actin blots are the same as in Figure 4C. (D) Changes in the expression of CCND1 after 56 hours in CRC PDX model. (E) Representative cell-cycle genes whose expression is influenced by MYC overexpression. Relative expression is plotted (TPM) (left panel) or as log2 fold change (right panel). (F) Representative cell-cycle genes whose expression is independent of MYC overexpression. Relative expression is plotted as TPM (left panel) or as log2 fold change (right panel). (G) MYC stabilization only partially rescues proliferation upon PORCN inhibition. Ki-67 staining quantitated as in B. Two-tailed Mann-Whitney U test was used to calculate significant differences.