Repression of rRNA gene transcription by endothelial SPEN deficiency normalizes tumor vasculature via nucleolar stress
Zi-Yan Yang, … , Tian Xiao, Hua Han
Zi-Yan Yang, … , Tian Xiao, Hua Han
Published August 22, 2023
Citation Information: J Clin Invest. 2023;133(20):e159860. https://doi.org/10.1172/JCI159860.
View: Text | PDF
Research Article Vascular biology

Repression of rRNA gene transcription by endothelial SPEN deficiency normalizes tumor vasculature via nucleolar stress

Abstract

Human cancers induce a chaotic, dysfunctional vasculature that promotes tumor growth and blunts most current therapies; however, the mechanisms underlying the induction of a dysfunctional vasculature have been unclear. Here, we show that split end (SPEN), a transcription repressor, coordinates rRNA synthesis in endothelial cells (ECs) and is required for physiological and tumor angiogenesis. SPEN deficiency attenuated EC proliferation and blunted retinal angiogenesis, which was attributed to p53 activation. Furthermore, SPEN knockdown activated p53 by upregulating noncoding promoter RNA (pRNA), which represses rRNA transcription and triggers p53-mediated nucleolar stress. In human cancer biopsies, a low endothelial SPEN level correlated with extended overall survival. In mice, endothelial SPEN deficiency compromised rRNA expression and repressed tumor growth and metastasis by normalizing tumor vessels, and this was abrogated by p53 haploinsufficiency. rRNA gene transcription is driven by RNA polymerase I (RNPI). We found that CX-5461, an RNPI inhibitor, recapitulated the effect of Spen ablation on tumor vessel normalization and combining CX-5461 with cisplatin substantially improved the efficacy of treating tumors in mice. Together, these results demonstrate that SPEN is required for angiogenesis by repressing pRNA to enable rRNA gene transcription and ribosomal biogenesis and that RNPI represents a target for tumor vessel normalization therapy of cancer.

Authors

Zi-Yan Yang, Xian-Chun Yan, Jia-Yu-Lin Zhang, Liang Liang, Chun-Chen Gao, Pei-Ran Zhang, Yuan Liu, Jia-Xing Sun, Bai Ruan, Juan-Li Duan, Ruo-Nan Wang, Xing-Xing Feng, Bo Che, Tian Xiao, Hua Han

×

Figure 10

An RNPI inhibitor induces tumor vessel normalization and enhances efficacy of cisplatin.

Options: View larger image (or click on image) Download as PowerPoint
An RNPI inhibitor induces tumor vessel normalization and enhances effica...
(A–D) Mice were inoculated with LLC cells and injected with LNP-pRNA or LNP-control (LNP-Ctrl) i.v. every 3 days from day 7 to day 21 after inoculation. (A) pRNA expression in TECs was determined by RT-qPCR. (B) Tumor growth was determined. (C and D) Tumor vessels were stained with immunofluorescence, and vessel perfusion was evaluated (Supplemental Figure 9, F–H) (n = 6). (E) Mice were inoculated with LLC cells and orally administered 50 mg/kg CX-5461 every 2 days from day 7 to day 14 after inoculation. Tumor sections were immunostained on day 14 after inoculation with anti-CD31 (n = 6), anti-CD31 plus anti–α-SMA (n = 6), anti-CD31 plus anti-NG2 (n = 3), and anti-CD31 plus anti-laminin (n = 3). Tumor vessels were reconstructed with CD31 immunofluorescence (60 μm thickness) (representing 3 independent experiments). Scale bars: 100 μm. (F) LLC tumor sections from mice treated with CX-5461 were stained with CD31 and VE-cadherin or CD31 and ZO-1 immunofluorescence and quantitatively compared (n = 5). Scale bars: 100 μm. (G) Vessel perfusion and leakage were assessed (n = 4). Scale bars: 100 μm. (H) Mice bearing LLC tumors were orally administered 50 mg/kg CX-5461 every 2 days and injected i.p. with CDDP every 3 days from day 7 to day 14 after inoculation. Tumors were dissected (Supplemental Figure 10D), and tumor sizes and weights were compared (n = 6). Data represent mean ± SEM. One-way ANOVA with Tukey’s multiple comparisons test was used for H, and unpaired 2-tailed Student’s t test was used for A–G.