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Autophagy and modular restructuring of metabolism control germline tumor differentiation and proliferation in C. elegans.

Gomes LC, Odedra D, Dikic I, Pohl C - Autophagy (2016)

Bottom Line: To understand how autophagy plays this dual role in cancer, in vivo models are required.Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism.Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.

View Article: PubMed Central - PubMed

Affiliation: a Buchmann Institute for Molecular Life Sciences, Goethe University , Frankfurt (Main) , Germany.

ABSTRACT
Autophagy can act either as a tumor suppressor or as a survival mechanism for established tumors. To understand how autophagy plays this dual role in cancer, in vivo models are required. By using a highly heterogeneous C. elegans germline tumor, we show that autophagy-related proteins are expressed in a specific subset of tumor cells, neurons. Inhibition of autophagy impairs neuronal differentiation and increases tumor cell number, resulting in a shorter life span of animals with tumors, while induction of autophagy extends their life span by impairing tumor proliferation. Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism. Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.

No MeSH data available.


Related in: MedlinePlus

Stress-response related genes are upregulated in animals with germline tumors. (A) KEGG pathway enrichment analysis of gld-1 RNAi animals. Only upregulated pathways in gld-1 RNAi animals compared to young adults with P values lower than 0.01 are shown. (B) Top: Heatmap depicting expression profiles of autophagy-related genes in gld-1 RNAi animals compared to young adult controls. log2-fold changes are shown. Bottom: The autophagy pathway in C. elegans. Genes were classified in functional modules according to ref. 77. (C) Modulation of autophagy by RNAi in the RNAi-mediated germline tumor model. GFP::LGG-1 animals with the respective RNAi were treated as indicated for 24 h and lysed. Protein samples (25 µg) were separated by SDS-PAGE and immunoblotted with the indicated antibodies. Where indicated, RNAi(s) against 2 different genes cloned in the same vector were used only when more than 80% of the animals presented a germline tumor.
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f0003: Stress-response related genes are upregulated in animals with germline tumors. (A) KEGG pathway enrichment analysis of gld-1 RNAi animals. Only upregulated pathways in gld-1 RNAi animals compared to young adults with P values lower than 0.01 are shown. (B) Top: Heatmap depicting expression profiles of autophagy-related genes in gld-1 RNAi animals compared to young adult controls. log2-fold changes are shown. Bottom: The autophagy pathway in C. elegans. Genes were classified in functional modules according to ref. 77. (C) Modulation of autophagy by RNAi in the RNAi-mediated germline tumor model. GFP::LGG-1 animals with the respective RNAi were treated as indicated for 24 h and lysed. Protein samples (25 µg) were separated by SDS-PAGE and immunoblotted with the indicated antibodies. Where indicated, RNAi(s) against 2 different genes cloned in the same vector were used only when more than 80% of the animals presented a germline tumor.

Mentions: In gld-1 animals, changes in translation seem to be accompanied by transcriptional changes. Several gld-1 targets have been identified;25-27 some of them are transcriptional regulators, like pal-1/Caudal, whose translation is repressed by GLD-1.2 Additionally, GLD-1 can bind and protect its targets from nonsense-mediated mRNA decay (NMD), for instance the glucosamine 6-phosphate N-acetyltransferase gna-2 and the putative transposase Y75B12B.1.28 To confirm our data using integrated reporters (Figs. 1 and 2) and to gain deeper understanding of the transcriptional regulation in gld-1 tumors, we performed a comprehensive analysis of the transcriptome in wild-type and gld-1 RNAi animals. Genome-wide transcriptome analysis of tumor-containing gld-1 RNAi animals (third d of adulthood) was carried out and compared with wild-type animals of the same age as well as young adults. First, we analyzed the transcripts of the 2 targets protected from NMD. These are strongly downregulated when comparing gld-1 tumor animals with staged gravid adults and young adults (5.2- and 2.6-fold for gna-2, 3.5- and 2.0-fold for Y75B12B.1, respectively). Second, we performed a gene ontology (GO) analysis, which showed that genes related to stress response pathways (e.g., DNA repair, ubiquitin-mediated proteolysis) and autophagy (9 genes) are upregulated in gld-1 RNAi animals compared to young adults (Fig. 3A and B; Table S1), but not compared to wild-type adults of the same age (Table S2) since expression of these genes in the embryos seems to mask the differences between gld-1-depleted and older wild-type animals. All together, these findings are consistent with a transcriptional upregulation of autophagy-related genes followed by protein synthesis in tumor cells.Figure 3.


Autophagy and modular restructuring of metabolism control germline tumor differentiation and proliferation in C. elegans.

Gomes LC, Odedra D, Dikic I, Pohl C - Autophagy (2016)

Stress-response related genes are upregulated in animals with germline tumors. (A) KEGG pathway enrichment analysis of gld-1 RNAi animals. Only upregulated pathways in gld-1 RNAi animals compared to young adults with P values lower than 0.01 are shown. (B) Top: Heatmap depicting expression profiles of autophagy-related genes in gld-1 RNAi animals compared to young adult controls. log2-fold changes are shown. Bottom: The autophagy pathway in C. elegans. Genes were classified in functional modules according to ref. 77. (C) Modulation of autophagy by RNAi in the RNAi-mediated germline tumor model. GFP::LGG-1 animals with the respective RNAi were treated as indicated for 24 h and lysed. Protein samples (25 µg) were separated by SDS-PAGE and immunoblotted with the indicated antibodies. Where indicated, RNAi(s) against 2 different genes cloned in the same vector were used only when more than 80% of the animals presented a germline tumor.
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Related In: Results  -  Collection

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f0003: Stress-response related genes are upregulated in animals with germline tumors. (A) KEGG pathway enrichment analysis of gld-1 RNAi animals. Only upregulated pathways in gld-1 RNAi animals compared to young adults with P values lower than 0.01 are shown. (B) Top: Heatmap depicting expression profiles of autophagy-related genes in gld-1 RNAi animals compared to young adult controls. log2-fold changes are shown. Bottom: The autophagy pathway in C. elegans. Genes were classified in functional modules according to ref. 77. (C) Modulation of autophagy by RNAi in the RNAi-mediated germline tumor model. GFP::LGG-1 animals with the respective RNAi were treated as indicated for 24 h and lysed. Protein samples (25 µg) were separated by SDS-PAGE and immunoblotted with the indicated antibodies. Where indicated, RNAi(s) against 2 different genes cloned in the same vector were used only when more than 80% of the animals presented a germline tumor.
Mentions: In gld-1 animals, changes in translation seem to be accompanied by transcriptional changes. Several gld-1 targets have been identified;25-27 some of them are transcriptional regulators, like pal-1/Caudal, whose translation is repressed by GLD-1.2 Additionally, GLD-1 can bind and protect its targets from nonsense-mediated mRNA decay (NMD), for instance the glucosamine 6-phosphate N-acetyltransferase gna-2 and the putative transposase Y75B12B.1.28 To confirm our data using integrated reporters (Figs. 1 and 2) and to gain deeper understanding of the transcriptional regulation in gld-1 tumors, we performed a comprehensive analysis of the transcriptome in wild-type and gld-1 RNAi animals. Genome-wide transcriptome analysis of tumor-containing gld-1 RNAi animals (third d of adulthood) was carried out and compared with wild-type animals of the same age as well as young adults. First, we analyzed the transcripts of the 2 targets protected from NMD. These are strongly downregulated when comparing gld-1 tumor animals with staged gravid adults and young adults (5.2- and 2.6-fold for gna-2, 3.5- and 2.0-fold for Y75B12B.1, respectively). Second, we performed a gene ontology (GO) analysis, which showed that genes related to stress response pathways (e.g., DNA repair, ubiquitin-mediated proteolysis) and autophagy (9 genes) are upregulated in gld-1 RNAi animals compared to young adults (Fig. 3A and B; Table S1), but not compared to wild-type adults of the same age (Table S2) since expression of these genes in the embryos seems to mask the differences between gld-1-depleted and older wild-type animals. All together, these findings are consistent with a transcriptional upregulation of autophagy-related genes followed by protein synthesis in tumor cells.Figure 3.

Bottom Line: To understand how autophagy plays this dual role in cancer, in vivo models are required.Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism.Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.

View Article: PubMed Central - PubMed

Affiliation: a Buchmann Institute for Molecular Life Sciences, Goethe University , Frankfurt (Main) , Germany.

ABSTRACT
Autophagy can act either as a tumor suppressor or as a survival mechanism for established tumors. To understand how autophagy plays this dual role in cancer, in vivo models are required. By using a highly heterogeneous C. elegans germline tumor, we show that autophagy-related proteins are expressed in a specific subset of tumor cells, neurons. Inhibition of autophagy impairs neuronal differentiation and increases tumor cell number, resulting in a shorter life span of animals with tumors, while induction of autophagy extends their life span by impairing tumor proliferation. Fasting of animals with fully developed tumors leads to a doubling of their life span, which depends on modular changes in transcription including switches in transcription factor networks and mitochondrial metabolism. Hence, our results suggest that metabolic restructuring, cell-type specific regulation of autophagy and neuronal differentiation constitute central pathways preventing growth of heterogeneous tumors.

No MeSH data available.


Related in: MedlinePlus