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, 25 (6), 822-30

Mutant Gq/11 Promote Uveal Melanoma Tumorigenesis by Activating YAP

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Mutant Gq/11 Promote Uveal Melanoma Tumorigenesis by Activating YAP

Fa-Xing Yu et al. Cancer Cell.

Abstract

Uveal melanoma (UM) is the most common cancer in adult eyes. Approximately 80% of UMs harbor somatic activating mutations in GNAQ or GNA11 (encoding Gq or G11, respectively). Herein, we show in both cell culture and human tumors that cancer-associated Gq/11 mutants activate YAP, a major effector of the Hippo tumor suppressor pathway that is also regulated by G protein-coupled receptor signaling. YAP mediates the oncogenic activity of mutant Gq/11 in UM development, and the YAP inhibitor verteporfin blocks tumor growth of UM cells containing Gq/11 mutations. This study reveals an essential role of the Hippo-YAP pathway in Gq/11-induced tumorigenesis and suggests YAP as a potential drug target for UM patients carrying mutations in GNAQ or GNA11.

Figures

Figure 1
Figure 1. Activation of YAP by mutant Gq/11 in UM cell lines
(A) Effects of UM-associated mutant Gq/11 on YAP/TAZ activity. HEK293A cells were transfected with different Gq/11 plasmids together with FLAG-YAP, and following 12 hr serum starvation, cells were harvested and YAP/TAZ activation status was analyzed by immunoblotting using the indicated antibodies. YAP phosphorylation was assessed using gels containing phos-tag, which slows down migration of phosphorylated YAP during electrophoresis. Endogenous TAZ protein levels were determined with a TAZ specific antibody. For the Gq plasmids, two concentrations of plasmids were used in transfection and the expression levels of transfected Gq were determined by immunoblotting. (B) A table summarizing Gq/11 or BRAF mutation status, YAP phosphorylation, YAP localization, and responses to serum of multiple UM cells. Nuc, Nucleus; Cyto, cytoplasm; wt, wild type; the number of “+” indicate the strength; *, information from Griewank et al., 2012. (C) YAP phosphorylation and response to serum in representative UM cell lines. UM cells were cultured with or without 10% FBS for 16 hr. (D) YAP localization and response to serum in representative UM cell lines. Cells were maintained in the presence or absence of 10% FBS for 16 hr, and after fixation, YAP localization was determined by immunostaining. The green and blue colors represent YAP and DNA staining, respectively. Scale bars represent 5 µm. See also Figure S1.
Figure 2
Figure 2. YAP nuclear localization correlates with Gq/11 mutations in UM specimens
(A) Representative images for YAP localization in UM specimens. Immunofluorescence staining was performed for YAP (Green) and DNA (Blue, DAPI). Shown are three representative samples of wild type (left panels) and Gq/11 mutant (right panels). Scale bars represent 10 µm. (B) Correlation between YAP nuclear localization and Gq/11 mutation in UM specimens. The subcellular localization of YAP were scored from 1 to 5, with “1” representing exclusive nuclear localization and “5” representing for exclusive cytoplasmic localization. Student t test (two-tailed, 95% confidence intervals) was used for statistical analysis, and error bars represent standard deviation (SD). See also Table S1.
Figure 3
Figure 3. Down-regulation of mutant Gq in UM cells inactivates YAP
(A) Tumor formation ability of 92.1 (GqQ209L) cells with or without Gq knockdown. Control or Gq knockdown 92.1 cells were grafted into nude mice subcutaneously, and tumor formation was monitored. Knockdown efficiency is shown in (B). Error bars represent SD. (B) The effect of Gq knockdown on YAP phosphorylation. Stable 92.1 cells expressing control shRNA (shCTL) or two Gq targeting shRNAs (shGq#1 and shGq#2) were established. Gq knockdown efficiency and YAP phosphorylation in these cells were assessed by Western blotting. pYAP indicates Western blotting with an antibody that specially recognizes the S127 phosphorylated YAP. The same experiment was performed in Mel270 (GqQ209P) cells. (C) The effect of Gq knockdown on YAP-TEAD interaction. Immunoprecipitation of YAP from control or Gq knockdown cell lysates was performed, and TEAD1 co-precipitated was determined by immunoblotting. IP denotes immunoprecipitation. (D, E) The effect of Gq knockdown on YAP subcellular localization. Control or Gq knockdown 92.1 cells were serum starved for 16 hr and fixed, and YAP localization was determined. Scale bars represent 5 µm. (F) The effect of Gq knockdown on PKA-induced YAP phosphorylation (inactivation). Control or Gq knockdown cells were treated with Forskorlin (10 µM) and IBMX (100 µM) for 1 hr, and then YAP phosphorylation was determined. Both Forskolin and IBMX increase cAMP and activate PKA, which stimulates YAP phosphorylation.
Figure 4
Figure 4. YAP is required for mutant Gq/11-induced tumorigenises
(A) Knockdown of YAP and/or TAZ in melan-a cells expressing GqQ209L. (B) The effect of YAP and/or TAZ knockdown on anchorage independent growth of melan-a cells expressing GqQ209L. Different melan-a cell lines were cultured in soft agar, and colony formation was assessed. GFP and GqQ209L denote melan-a cells stably expressing GFP control and GqQ209L, respectively. shRNA knockdown of YAP and/or TAZ are indicated, Y/T stand for combination of YAP and TAZ shRNAs. (C) Tumorigenicity of the GqQ209L expressing melan-a cells following YAP knockdown. The same cell lines used in (B) were grafted into nude mice subcutaneously, and tumor formation was monitored. (D) Inducible knockdown of YAP in 92.1 or OCM1 cells. Cells were treated with Dox (2.5 µg/ml) for 3 days, and YAP knockdown was assessed by immunoblotting. (E) The effect of YAP knockdown on cell migration. Migration potential of 92.1 or OCM1 cells following YAP knockdown was assessed using a transwell assay. (F–H) Tumorigenicity of Gq (92.1) mutant and BRAF (OCM1 and OCM8) mutant UM cells following YAP knockdown. Control or YAP knockdown 92.1 (F), OCM1 (BRAF) (G) or OCM8 (H) cells were grafted into nude mice subcutaneously, and tumor formation was monitored. Student t test (two-tailed, 95% confidence intervals) was used for statistical analysis, and error bars represent SD. See also Figure S2.
Figure 5
Figure 5. YAP inhibitor suppresses tumor growth of Gq/11 mutated UM cells
(A) Sensitivity of Gq/11 mutant and BRAF mutant UM cells to Verteporfin, a YAP inhibitor. Gq mutant cells or BRAF mutant cells were treated with 0.2 µg/ml or 1 µg/ml of verteporfin for 48 hr, and cell lysates were assessed for PARP1 cleavage (the black arrow indicate the position of cleaved PARP1, an indicator of cell death. (B) Sensitivity of Gq/11 mutant and BRAF mutant UM cells to U0126, a MEK inhibitor. UM cells were treated with 5 µM and 25 µM of U0126 for 36 hr, and then cell apoptosis was assessed by PARP1 cleavage. (C–D) Effects of Verteporfin treatment on tumor growth of 92.1 cells in an orthotopic UM mouse model. Prior to injection into the suprachoroidal space of the eye, 92.1 cells were mixed with nanoparticles containing verteporfin or buffer (control, CTL). After injection, verteporfin was delivered systematically to mice (treated) via intraperitoneal injection. Tumor formation was monitored by OCT, and tumors were harvested and sectioned for histological analysis. Representative sections of the eye showed the presence of large pigmented melanoma xenografts filling the eyes of all vehicle-treated animals (left panels in C), whereas tumors in the vertepofin treatment group (right panels in C) were smaller as indicated by black arrows. The tumor areas from 5 injected eyes were quantified and are shown in (D). (E, F) Effect of Verteporfin treatment on tumor growth of OCM1 cells. Similar experiments were performed as (C, D) using OCM1 cells. Student t test (two-tailed, 95% confidence intervals) was used for statistical analysis, and error bars represent SD. Scale bars represent 100 µm. See also Figure S3.

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