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Dystrophin is a tumor suppressor in human cancers with myogenic programs.

Wang Y, Marino-Enriquez A, Bennett RR, Zhu M, Shen Y, Eilers G, Lee JC, Henze J, Fletcher BS, Gu Z, Fox EA, Antonescu CR, Fletcher CD, Guo X, Raut CP, Demetri GD, van de Rijn M, Ordog T, Kunkel LM, Fletcher JA - Nat. Genet. (2014)

Bottom Line: Here we report that intragenic deletion of the dystrophin-encoding and muscular dystrophy-associated DMD gene is a frequent mechanism by which myogenic tumors progress to high-grade, lethal sarcomas.Dystrophin inhibits myogenic sarcoma cell migration, invasion, anchorage independence and invadopodia formation, and dystrophin inactivation was found in 96%, 100% and 62% of metastatic GIST, embryonal RMS and LMS samples, respectively.These findings validate dystrophin as a tumor suppressor and likely anti-metastatic factor, suggesting that therapies in development for muscular dystrophies may also have relevance in the treatment of cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Many common human mesenchymal tumors, including gastrointestinal stromal tumor (GIST), rhabdomyosarcoma (RMS) and leiomyosarcoma (LMS), feature myogenic differentiation. Here we report that intragenic deletion of the dystrophin-encoding and muscular dystrophy-associated DMD gene is a frequent mechanism by which myogenic tumors progress to high-grade, lethal sarcomas. Dystrophin is expressed in the non-neoplastic and benign counterparts of GIST, RMS and LMS tumors, and DMD deletions inactivate larger dystrophin isoforms, including 427-kDa dystrophin, while preserving the expression of an essential 71-kDa isoform. Dystrophin inhibits myogenic sarcoma cell migration, invasion, anchorage independence and invadopodia formation, and dystrophin inactivation was found in 96%, 100% and 62% of metastatic GIST, embryonal RMS and LMS samples, respectively. These findings validate dystrophin as a tumor suppressor and likely anti-metastatic factor, suggesting that therapies in development for muscular dystrophies may also have relevance in the treatment of cancer.

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Loss of dystrophin 427kDa expression in most metastatic GIST, RMS and LMS. Western blotting with DYS1 demonstrates dystrophin expression in the normal tissue and benign tumor counterparts for GIST, RMS and LMS (a to d); low-risk GIST is a clinically indolent precursor to malignant GIST. Loss of dystrophin 427kDa expression is demonstrated in most metastatic GIST (b), RMS (c) and LMS (d). Patient 116 samples (d) are five successive LMS metastases, resected during an 8 year interval in the same patient.
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Figure 3: Loss of dystrophin 427kDa expression in most metastatic GIST, RMS and LMS. Western blotting with DYS1 demonstrates dystrophin expression in the normal tissue and benign tumor counterparts for GIST, RMS and LMS (a to d); low-risk GIST is a clinically indolent precursor to malignant GIST. Loss of dystrophin 427kDa expression is demonstrated in most metastatic GIST (b), RMS (c) and LMS (d). Patient 116 samples (d) are five successive LMS metastases, resected during an 8 year interval in the same patient.

Mentions: DMD is the longest known human gene15, composed of 79 coding exons spanning 2.2 megabases of the genome, with various transcriptional start sites18. Multiplex ligation-dependent probe amplification (MLPA) copy number assessment for each of the DMD coding exons revealed intragenic DMD deletions in 24 of 56 high-grade myogenic cancers (43%) (Fig. 3, Supplementary Fig. 4 and Supplementary Table 3), all of which were predicted to abrogate expression of the largest dystrophin isoform (427kDa), encoded by DMD exons 1–79. By contrast, intragenic DMD deletions were not found in 20 benign tumor counterparts for GIST, RMS and LMS (11 low-risk GISTs, 2 rhabdomyomas and 7 leiomyomas), despite high levels of dystrophin expression (Supplementary Table 3). The dystrophin 427kDa isoform was expressed strongly in normal tissue and benign counterparts for GIST, RMS and LMS (Fig. 4), but was undetectable or weakly expressed in 96% of metastatic GISTs (26 of 27), irrespective of whether they contained KIT or PDGFRA mutations (Fig. 4b and Supplementary Table 4). Similarly, dystrophin 427kDa expression was undetectable or weak in 100% of metastatic embryonal RMS (eRMS) (9 of 9), and 62% of metastatic LMS (8 of 13) (Fig. 4c,d and Supplementary Table 4). Dystrophin 427kDa was also downregulated in 75% of primary “high-risk” GISTs (i.e., GISTs having histologic criteria predictive of metastasis), consistent with the SNP evidence that DMD dysregulation is positively selected for in clinically-aggressive primary tumors, even prior to metastasis (Fig. 4b). Expression of 427kDa dystrophin was not detected in 46 non-myogenic sarcomas (Supplementary Table 5). By contrast, expression of dystrophin isoform Dp71 (71kDa), encoded by exons 63–79, is preserved in cancers with DMD deletions (Fig. 5). Dp71 is also expressed in non-myogenic sarcomas (Supplementary Fig. 5), in keeping with reports that Dp71 expression is ubiquitous in nonneoplastic tissues, other than skeletal muscle19. DMD Dp71 knockdown in DMD-deleted RMS cells inhibited cell growth (Supplementary Fig. 6), indicating that dystrophin 71kDa has essential roles in myogenic cancer cells. These findings account for obligate dystrophin 71kDa expression in myogenic cancers, and explain why DMD genomic deletions rarely extend to the coding sequence for this isoform (Fig. 3).


Dystrophin is a tumor suppressor in human cancers with myogenic programs.

Wang Y, Marino-Enriquez A, Bennett RR, Zhu M, Shen Y, Eilers G, Lee JC, Henze J, Fletcher BS, Gu Z, Fox EA, Antonescu CR, Fletcher CD, Guo X, Raut CP, Demetri GD, van de Rijn M, Ordog T, Kunkel LM, Fletcher JA - Nat. Genet. (2014)

Loss of dystrophin 427kDa expression in most metastatic GIST, RMS and LMS. Western blotting with DYS1 demonstrates dystrophin expression in the normal tissue and benign tumor counterparts for GIST, RMS and LMS (a to d); low-risk GIST is a clinically indolent precursor to malignant GIST. Loss of dystrophin 427kDa expression is demonstrated in most metastatic GIST (b), RMS (c) and LMS (d). Patient 116 samples (d) are five successive LMS metastases, resected during an 8 year interval in the same patient.
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Related In: Results  -  Collection

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Figure 3: Loss of dystrophin 427kDa expression in most metastatic GIST, RMS and LMS. Western blotting with DYS1 demonstrates dystrophin expression in the normal tissue and benign tumor counterparts for GIST, RMS and LMS (a to d); low-risk GIST is a clinically indolent precursor to malignant GIST. Loss of dystrophin 427kDa expression is demonstrated in most metastatic GIST (b), RMS (c) and LMS (d). Patient 116 samples (d) are five successive LMS metastases, resected during an 8 year interval in the same patient.
Mentions: DMD is the longest known human gene15, composed of 79 coding exons spanning 2.2 megabases of the genome, with various transcriptional start sites18. Multiplex ligation-dependent probe amplification (MLPA) copy number assessment for each of the DMD coding exons revealed intragenic DMD deletions in 24 of 56 high-grade myogenic cancers (43%) (Fig. 3, Supplementary Fig. 4 and Supplementary Table 3), all of which were predicted to abrogate expression of the largest dystrophin isoform (427kDa), encoded by DMD exons 1–79. By contrast, intragenic DMD deletions were not found in 20 benign tumor counterparts for GIST, RMS and LMS (11 low-risk GISTs, 2 rhabdomyomas and 7 leiomyomas), despite high levels of dystrophin expression (Supplementary Table 3). The dystrophin 427kDa isoform was expressed strongly in normal tissue and benign counterparts for GIST, RMS and LMS (Fig. 4), but was undetectable or weakly expressed in 96% of metastatic GISTs (26 of 27), irrespective of whether they contained KIT or PDGFRA mutations (Fig. 4b and Supplementary Table 4). Similarly, dystrophin 427kDa expression was undetectable or weak in 100% of metastatic embryonal RMS (eRMS) (9 of 9), and 62% of metastatic LMS (8 of 13) (Fig. 4c,d and Supplementary Table 4). Dystrophin 427kDa was also downregulated in 75% of primary “high-risk” GISTs (i.e., GISTs having histologic criteria predictive of metastasis), consistent with the SNP evidence that DMD dysregulation is positively selected for in clinically-aggressive primary tumors, even prior to metastasis (Fig. 4b). Expression of 427kDa dystrophin was not detected in 46 non-myogenic sarcomas (Supplementary Table 5). By contrast, expression of dystrophin isoform Dp71 (71kDa), encoded by exons 63–79, is preserved in cancers with DMD deletions (Fig. 5). Dp71 is also expressed in non-myogenic sarcomas (Supplementary Fig. 5), in keeping with reports that Dp71 expression is ubiquitous in nonneoplastic tissues, other than skeletal muscle19. DMD Dp71 knockdown in DMD-deleted RMS cells inhibited cell growth (Supplementary Fig. 6), indicating that dystrophin 71kDa has essential roles in myogenic cancer cells. These findings account for obligate dystrophin 71kDa expression in myogenic cancers, and explain why DMD genomic deletions rarely extend to the coding sequence for this isoform (Fig. 3).

Bottom Line: Here we report that intragenic deletion of the dystrophin-encoding and muscular dystrophy-associated DMD gene is a frequent mechanism by which myogenic tumors progress to high-grade, lethal sarcomas.Dystrophin inhibits myogenic sarcoma cell migration, invasion, anchorage independence and invadopodia formation, and dystrophin inactivation was found in 96%, 100% and 62% of metastatic GIST, embryonal RMS and LMS samples, respectively.These findings validate dystrophin as a tumor suppressor and likely anti-metastatic factor, suggesting that therapies in development for muscular dystrophies may also have relevance in the treatment of cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Many common human mesenchymal tumors, including gastrointestinal stromal tumor (GIST), rhabdomyosarcoma (RMS) and leiomyosarcoma (LMS), feature myogenic differentiation. Here we report that intragenic deletion of the dystrophin-encoding and muscular dystrophy-associated DMD gene is a frequent mechanism by which myogenic tumors progress to high-grade, lethal sarcomas. Dystrophin is expressed in the non-neoplastic and benign counterparts of GIST, RMS and LMS tumors, and DMD deletions inactivate larger dystrophin isoforms, including 427-kDa dystrophin, while preserving the expression of an essential 71-kDa isoform. Dystrophin inhibits myogenic sarcoma cell migration, invasion, anchorage independence and invadopodia formation, and dystrophin inactivation was found in 96%, 100% and 62% of metastatic GIST, embryonal RMS and LMS samples, respectively. These findings validate dystrophin as a tumor suppressor and likely anti-metastatic factor, suggesting that therapies in development for muscular dystrophies may also have relevance in the treatment of cancer.

Show MeSH
Related in: MedlinePlus