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A drosophila model for EGFR-Ras and PI3K-dependent human glioma.

Read RD, Cavenee WK, Furnari FB, Thomas JB - PLoS Genet. (2009)

Bottom Line: This network acts synergistically to coordinately stimulate cell cycle entry and progression, protein translation, and inappropriate cellular growth and migration.In particular, we found that the fly orthologs of CyclinE, Cdc25, and Myc are key rate-limiting genes required for glial neoplasia.Moreover, orthologs of Sin1, Rictor, and Cdk4 are genes required only for abnormal neoplastic glial proliferation but not for glial development.

View Article: PubMed Central - PubMed

Affiliation: Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America. rread@salk.edu

ABSTRACT
Gliomas, the most common malignant tumors of the nervous system, frequently harbor mutations that activate the epidermal growth factor receptor (EGFR) and phosphatidylinositol-3 kinase (PI3K) signaling pathways. To investigate the genetic basis of this disease, we developed a glioma model in Drosophila. We found that constitutive coactivation of EGFR-Ras and PI3K pathways in Drosophila glia and glial precursors gives rise to neoplastic, invasive glial cells that create transplantable tumor-like growths, mimicking human glioma. Our model represents a robust organotypic and cell-type-specific Drosophila cancer model in which malignant cells are created by mutations in signature genes and pathways thought to be driving forces in a homologous human cancer. Genetic analyses demonstrated that EGFR and PI3K initiate malignant neoplastic transformation via a combinatorial genetic network composed primarily of other pathways commonly mutated or activated in human glioma, including the Tor, Myc, G1 Cyclins-Cdks, and Rb-E2F pathways. This network acts synergistically to coordinately stimulate cell cycle entry and progression, protein translation, and inappropriate cellular growth and migration. In particular, we found that the fly orthologs of CyclinE, Cdc25, and Myc are key rate-limiting genes required for glial neoplasia. Moreover, orthologs of Sin1, Rictor, and Cdk4 are genes required only for abnormal neoplastic glial proliferation but not for glial development. These and other genes within this network may represent important therapeutic targets in human glioma.

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Coactivation of EGFR and PI3K inhibits cell cycle exit in glia.Larval brain fragments of the indicated genotypes were injected into the abdomens of wild-type adult hosts and grown for 3 weeks. CD8GFP (green) labels all transplanted glia within each graft. Actin (red, phalloidin) reveals abdominal anatomy. (A, B) Representative frozen sections of whole abdomens with wild-type (A) or dEGFRλ;dp110CAAX (B) transplants, shown at the same scale. 50 µm optical projections; 100 µm scale bars. (C–F) Transplants shown at higher magnification. dEGFRλ;dp110CAAX transplants (D–F) are rich with glial cell nuclei (Repo, in blue) relative to wild-type transplants (C). Asterisks indicate trachea embedded in dEGFRλ;dp110CAAX transplants (D,E), visible as hollow actin-positive (red) tubules running through tissues. Arrowheads in (F) indicate dEGFRλ;dp110CAAX glial cells invading an ovary, distinguished by its characteristic actin staining (red). 1–1.5 µm optical sections; 20 µm scale bars. Genotypes: All hosts were w1118 virgin females. Transplanted glia as follows: (A) and (C) UAS-CD8GFP/+; repo-Gal4/+, (B), (D), (E), and (F) UAS-dEGFRλ UAS-dp110CAAX/+; UAS-CD8GFP/+; repo-Gal4/+.
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pgen-1000374-g003: Coactivation of EGFR and PI3K inhibits cell cycle exit in glia.Larval brain fragments of the indicated genotypes were injected into the abdomens of wild-type adult hosts and grown for 3 weeks. CD8GFP (green) labels all transplanted glia within each graft. Actin (red, phalloidin) reveals abdominal anatomy. (A, B) Representative frozen sections of whole abdomens with wild-type (A) or dEGFRλ;dp110CAAX (B) transplants, shown at the same scale. 50 µm optical projections; 100 µm scale bars. (C–F) Transplants shown at higher magnification. dEGFRλ;dp110CAAX transplants (D–F) are rich with glial cell nuclei (Repo, in blue) relative to wild-type transplants (C). Asterisks indicate trachea embedded in dEGFRλ;dp110CAAX transplants (D,E), visible as hollow actin-positive (red) tubules running through tissues. Arrowheads in (F) indicate dEGFRλ;dp110CAAX glial cells invading an ovary, distinguished by its characteristic actin staining (red). 1–1.5 µm optical sections; 20 µm scale bars. Genotypes: All hosts were w1118 virgin females. Transplanted glia as follows: (A) and (C) UAS-CD8GFP/+; repo-Gal4/+, (B), (D), (E), and (F) UAS-dEGFRλ UAS-dp110CAAX/+; UAS-CD8GFP/+; repo-Gal4/+.

Mentions: Since repo>dEGFRλ;dp110CAAX animals die in 5–7 days, we assessed the proliferative potential of mutant glia using an abdominal transplant assay, a classic test of tumorigencity in flies [37]. Brain fragments from repo>dEGFRλ;dp110CAAX and wild-type larvae were transplanted into young adults. Wild-type transplants grew and survived over 1–6 weeks, but produced few glia (Figure 3A and 3C). dEGFRλ;dp110CAAX mutant glia survived and proliferated into massive tumors that filled the hosts' abdomens, often causing premature death (Figure 3B). Tumors were composed of small glial cells with little cytoplasm (Figure 3D–F). Tumors also contained trachea embedded throughout their mass (Figure 3D and 3E and Video S1), suggesting that tumors stimulated growth of new trachea or enveloped existing trachea, perhaps in a process akin to tumor angiogenesis. The leading edges of the tumors harbored individual cells invading nearby tissues, such as the ovary (Figure 3F and Video S2), which is consistent with the ectopic expression of active dMMP1 observed in dEGFRλ;dp110CAAX glia in the larval brain (Figure S3). However, some tissues, such as the gut, did not contain metastases, implying some degree of selective invasion. Thus, once unconstrained by the larval life cycle, dEGFRλ;dp110CAAX glia fail to exit the cell cycle, continue to proliferate, and form highly invasive tumors, all properties of human cancer cells.


A drosophila model for EGFR-Ras and PI3K-dependent human glioma.

Read RD, Cavenee WK, Furnari FB, Thomas JB - PLoS Genet. (2009)

Coactivation of EGFR and PI3K inhibits cell cycle exit in glia.Larval brain fragments of the indicated genotypes were injected into the abdomens of wild-type adult hosts and grown for 3 weeks. CD8GFP (green) labels all transplanted glia within each graft. Actin (red, phalloidin) reveals abdominal anatomy. (A, B) Representative frozen sections of whole abdomens with wild-type (A) or dEGFRλ;dp110CAAX (B) transplants, shown at the same scale. 50 µm optical projections; 100 µm scale bars. (C–F) Transplants shown at higher magnification. dEGFRλ;dp110CAAX transplants (D–F) are rich with glial cell nuclei (Repo, in blue) relative to wild-type transplants (C). Asterisks indicate trachea embedded in dEGFRλ;dp110CAAX transplants (D,E), visible as hollow actin-positive (red) tubules running through tissues. Arrowheads in (F) indicate dEGFRλ;dp110CAAX glial cells invading an ovary, distinguished by its characteristic actin staining (red). 1–1.5 µm optical sections; 20 µm scale bars. Genotypes: All hosts were w1118 virgin females. Transplanted glia as follows: (A) and (C) UAS-CD8GFP/+; repo-Gal4/+, (B), (D), (E), and (F) UAS-dEGFRλ UAS-dp110CAAX/+; UAS-CD8GFP/+; repo-Gal4/+.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2636203&req=5

pgen-1000374-g003: Coactivation of EGFR and PI3K inhibits cell cycle exit in glia.Larval brain fragments of the indicated genotypes were injected into the abdomens of wild-type adult hosts and grown for 3 weeks. CD8GFP (green) labels all transplanted glia within each graft. Actin (red, phalloidin) reveals abdominal anatomy. (A, B) Representative frozen sections of whole abdomens with wild-type (A) or dEGFRλ;dp110CAAX (B) transplants, shown at the same scale. 50 µm optical projections; 100 µm scale bars. (C–F) Transplants shown at higher magnification. dEGFRλ;dp110CAAX transplants (D–F) are rich with glial cell nuclei (Repo, in blue) relative to wild-type transplants (C). Asterisks indicate trachea embedded in dEGFRλ;dp110CAAX transplants (D,E), visible as hollow actin-positive (red) tubules running through tissues. Arrowheads in (F) indicate dEGFRλ;dp110CAAX glial cells invading an ovary, distinguished by its characteristic actin staining (red). 1–1.5 µm optical sections; 20 µm scale bars. Genotypes: All hosts were w1118 virgin females. Transplanted glia as follows: (A) and (C) UAS-CD8GFP/+; repo-Gal4/+, (B), (D), (E), and (F) UAS-dEGFRλ UAS-dp110CAAX/+; UAS-CD8GFP/+; repo-Gal4/+.
Mentions: Since repo>dEGFRλ;dp110CAAX animals die in 5–7 days, we assessed the proliferative potential of mutant glia using an abdominal transplant assay, a classic test of tumorigencity in flies [37]. Brain fragments from repo>dEGFRλ;dp110CAAX and wild-type larvae were transplanted into young adults. Wild-type transplants grew and survived over 1–6 weeks, but produced few glia (Figure 3A and 3C). dEGFRλ;dp110CAAX mutant glia survived and proliferated into massive tumors that filled the hosts' abdomens, often causing premature death (Figure 3B). Tumors were composed of small glial cells with little cytoplasm (Figure 3D–F). Tumors also contained trachea embedded throughout their mass (Figure 3D and 3E and Video S1), suggesting that tumors stimulated growth of new trachea or enveloped existing trachea, perhaps in a process akin to tumor angiogenesis. The leading edges of the tumors harbored individual cells invading nearby tissues, such as the ovary (Figure 3F and Video S2), which is consistent with the ectopic expression of active dMMP1 observed in dEGFRλ;dp110CAAX glia in the larval brain (Figure S3). However, some tissues, such as the gut, did not contain metastases, implying some degree of selective invasion. Thus, once unconstrained by the larval life cycle, dEGFRλ;dp110CAAX glia fail to exit the cell cycle, continue to proliferate, and form highly invasive tumors, all properties of human cancer cells.

Bottom Line: This network acts synergistically to coordinately stimulate cell cycle entry and progression, protein translation, and inappropriate cellular growth and migration.In particular, we found that the fly orthologs of CyclinE, Cdc25, and Myc are key rate-limiting genes required for glial neoplasia.Moreover, orthologs of Sin1, Rictor, and Cdk4 are genes required only for abnormal neoplastic glial proliferation but not for glial development.

View Article: PubMed Central - PubMed

Affiliation: Molecular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California, United States of America. rread@salk.edu

ABSTRACT
Gliomas, the most common malignant tumors of the nervous system, frequently harbor mutations that activate the epidermal growth factor receptor (EGFR) and phosphatidylinositol-3 kinase (PI3K) signaling pathways. To investigate the genetic basis of this disease, we developed a glioma model in Drosophila. We found that constitutive coactivation of EGFR-Ras and PI3K pathways in Drosophila glia and glial precursors gives rise to neoplastic, invasive glial cells that create transplantable tumor-like growths, mimicking human glioma. Our model represents a robust organotypic and cell-type-specific Drosophila cancer model in which malignant cells are created by mutations in signature genes and pathways thought to be driving forces in a homologous human cancer. Genetic analyses demonstrated that EGFR and PI3K initiate malignant neoplastic transformation via a combinatorial genetic network composed primarily of other pathways commonly mutated or activated in human glioma, including the Tor, Myc, G1 Cyclins-Cdks, and Rb-E2F pathways. This network acts synergistically to coordinately stimulate cell cycle entry and progression, protein translation, and inappropriate cellular growth and migration. In particular, we found that the fly orthologs of CyclinE, Cdc25, and Myc are key rate-limiting genes required for glial neoplasia. Moreover, orthologs of Sin1, Rictor, and Cdk4 are genes required only for abnormal neoplastic glial proliferation but not for glial development. These and other genes within this network may represent important therapeutic targets in human glioma.

Show MeSH
Related in: MedlinePlus