Ligand-activated BMP signaling inhibits cell differentiation and death to promote melanoma
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
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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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 3

GDF6-dependent BMP activity in melanomas.

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GDF6-dependent BMP activity in melanomas. (A) Transverse sections of a ...
(A) Transverse sections of a Tg(mitfa:BRAFV600E);p53(lf) zebrafish bearing an invasive melanoma in the dorsal musculature. Top: H&E staining; bottom: p-SMAD1/5/8 staining. Scale bars: 500 μm (left) and 50 μm (enlarged insets on right). For p-SMAD1/5/8 staining, normal muscle (top) and a tumor region (bottom) are shown. Note that normal scale tissue (running vertically through the middle of the image) in the tumor region is p-SMAD1/5/8 negative. T, tumor; N, normal. (B) Heatmap of expression of BMP pathway genes (Reactome gene set R-HSA-201451.3; https://reactome.org/PathwayBrowser/) in zebrafish melanomas as compared with expression in melanocytes. Human orthologs of zebrafish genes are shown. (C) log2-transformed fold change of gene expression in zebrafish melanomas as compared with expression in melanocytes (y axis). Expression of BMP ligands in microarray analysis and RNA-seq analysis. Only BMP ligands with a significant dysregulation (adjusted P < 0.05) are shown. (D) Immunoblots of p-SMAD1/5/8 and total SMAD1/5/8 in A375 melanoma cells expressing an shRNA targeting EGFP or 2 independent GDF6-targeted shRNAs. (E) Aggregation plot of p-SMAD1/5/8 ChIP-seq enrichment at annotated transcriptional start sites (TSSs) in A375 melanoma cells expressing an shRNA targeting EGFP or the GDF6-targeted shRNA GDF6.1. The P value was calculated by 2-sample Kolmogorov-Smirnov (K-S) test after summing TSS proximal reads (–2kb to 2kb) for each gene (n = 49,344 TSSs). RPM, reads per million. (F) Tumor formation in mice injected with A375 cells (1 × 106 cells injected per mouse) treated with vehicle control or 25 mg/kg DMH1 every other day. Error bars represent the mean ± SEM. n = 8. (G) Tumor formation in mice injected with A375 empty or A375-SMAD1DVD cells expressing 2 independent GDF6-targeted shRNAs. Each mouse was injected with 1 × 107 cells. Error bars represent the mean ± SEM. n = 3. **P < 0.01 and ***P < 0.001, by 2-tailed Student’s t test (F) or 1-way ANOVA with Bonferroni’s test (G).