Ligand-activated BMP signaling inhibits cell differentiation and death to promote melanoma
Arvind M. Venkatesan, … , Michael Green, Craig J. Ceol
Arvind M. Venkatesan, … , Michael Green, Craig J. Ceol
Published December 4, 2017
Citation Information: J Clin Invest. 2018;128(1):294-308. https://doi.org/10.1172/JCI92513.
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Research Article Development Oncology

Ligand-activated BMP signaling inhibits cell differentiation and death to promote melanoma

Abstract

Oncogenomic studies indicate that copy number variation (CNV) alters genes involved in tumor progression; however, identification of specific driver genes affected by CNV has been difficult, as these rearrangements are often contained in large chromosomal intervals among several bystander genes. Here, we addressed this problem and identified a CNV-targeted oncogene by performing comparative oncogenomics of human and zebrafish melanomas. We determined that the gene encoding growth differentiation factor 6 (GDF6), which is the ligand for the BMP family, is recurrently amplified and transcriptionally upregulated in melanoma. GDF6-induced BMP signaling maintained a trunk neural crest gene signature in melanomas. Additionally, GDF6 repressed the melanocyte differentiation gene MITF and the proapoptotic factor SOX9, thereby preventing differentiation, inhibiting cell death, and promoting tumor growth. GDF6 was specifically expressed in melanomas but not melanocytes. Moreover, GDF6 expression levels in melanomas were inversely correlated with patient survival. Our study has identified a fundamental role for GDF6 and BMP signaling in governing an embryonic cell gene signature to promote melanoma progression, thus providing potential opportunities for targeted therapy to treat GDF6-positive cancers.

Authors

Arvind M. Venkatesan, Rajesh Vyas, Alec K. Gramann, Karen Dresser, Sharvari Gujja, Sanchita Bhatnagar, Sagar Chhangawala, Camilla Borges Ferreira Gomes, Hualin Simon Xi, Christine G. Lian, Yariv Houvras, Yvonne J. K. Edwards, April Deng, Michael Green, Craig J. Ceol

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Figure 6

GDF6 and BMP signaling repress SOX9 to promote melanoma cell survival.

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GDF6 and BMP signaling repress SOX9 to promote melanoma cell survival. ...
(A) GSEA showed that expression of an apoptotic gene set (MSigDB M10169) was negatively enriched in GDF6-overexpressing A375 cells. (B) Caspase-3/7 activity measured as relative luciferase units (RLU) in A375 cells upon GDF6 knockdown. Error bars represent the mean ± SEM. n = 3. (C) Fluorescent TUNEL staining of Tg(mitfa:BRAFV600E);p53(lf) (top) or Tg(mitfa:BRAFV600E);p53(lf);gdf6a(lf) (bottom) zebrafish melanoma sections. TUNEL (green), DAPI (blue), and a merged image of both channels are shown. Scale bars: 25 μm. Error bars represent the mean ± SEM. n = 100 fields. (D) TUNEL staining of mouse xenografts of A375 cells expressing SMAD1DVD upon GDF6 knockdown. Scale bar: 25 μm. Error bars represent the mean ± SEM. n = 100 fields. (E) Immunoblots showing expression of SOX9 and GAPDH in A375 empty or A375-SMAD1DVD cells expressing an shRNA targeting EGFP or the GDF6-targeted shRNA GDF6.1. (F) Caspase-3/7 activity measured as relative luciferase units (RLU) in A375-nonsilencing or A375-shSOX9 cells expressing an shRNA targeting EGFP or the GDF6-targeted shRNA GDF6.1. Error bars represent the mean ± SEM. n = 3. (G) Tumor formation in mice injected with A375-nonsilencing or A375-shSOX9 cells expressing 2 independent GDF6-targeted shRNAs. Each mouse was injected with 1 × 106 cells. Error bars represent the mean ± SEM. n = 3. ***P < 0.001, by 1-way ANOVA with Dunnett’s test (B), 2-tailed Student’s t test (C), or 1-way ANOVA with Bonferroni’s test (D, F, and G). ###P< 0.001, by 1-way ANOVA (G).