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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

Modulation of autophagy affects tumor growth. (A) N2 L1 or L3 (in the case of let-363 RNAi) larvae treated with the indicated dsRNA(s) till the fourth d of adulthood and stained with the DNA-intercalating dye DAPI (4′,6′-diamidino-2-phenylindole). Left: Representative animals. Right: Enlargement of the head region (boxed areas on the left). Dashed lines indicate the outline of the animal, white lines indicate the gonadal basement membrane. Scale bars: 20 μm. (B) Cell density visualized by fluorescent histone reporters (H1 and H2B-mCherry fusion proteins) in central (left) and proximal (right) parts of gld-1 RNAi-induced germline tumors in wild type and atg-7(bp411) animals. 3D projections are shown. Scale bar: 10 μm. (C) Quantification of cells per area and apoptotic corpses per gonad turn. n = 5 animals each; *** P ≤ 0.001. (D) Gonad turn nuclei and apoptotic corpses in wild-type and atg-7(bp411) animals treated with gld-1 RNAi. 3D projections. Note the chromatin threads that can be observed on goad surfaces in atg-7(bp411) (surface projection, right). Scale bar: 5 μm. (E) Quantification of animals with cell clusters, indicative of high tumor cell density. Animals were treated with the respective RNAis and tumor arms were imaged and scored at d 3 of adulthood for the appearance of bright nuclei clusters (as indicated by red arrows in panel [B]).
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f0005: Modulation of autophagy affects tumor growth. (A) N2 L1 or L3 (in the case of let-363 RNAi) larvae treated with the indicated dsRNA(s) till the fourth d of adulthood and stained with the DNA-intercalating dye DAPI (4′,6′-diamidino-2-phenylindole). Left: Representative animals. Right: Enlargement of the head region (boxed areas on the left). Dashed lines indicate the outline of the animal, white lines indicate the gonadal basement membrane. Scale bars: 20 μm. (B) Cell density visualized by fluorescent histone reporters (H1 and H2B-mCherry fusion proteins) in central (left) and proximal (right) parts of gld-1 RNAi-induced germline tumors in wild type and atg-7(bp411) animals. 3D projections are shown. Scale bar: 10 μm. (C) Quantification of cells per area and apoptotic corpses per gonad turn. n = 5 animals each; *** P ≤ 0.001. (D) Gonad turn nuclei and apoptotic corpses in wild-type and atg-7(bp411) animals treated with gld-1 RNAi. 3D projections. Note the chromatin threads that can be observed on goad surfaces in atg-7(bp411) (surface projection, right). Scale bar: 5 μm. (E) Quantification of animals with cell clusters, indicative of high tumor cell density. Animals were treated with the respective RNAis and tumor arms were imaged and scored at d 3 of adulthood for the appearance of bright nuclei clusters (as indicated by red arrows in panel [B]).

Mentions: A balance between self-renewal and differentiation of stem cells is critical for proliferation control and maintenance of a stem cell pool in mammalian tissues.36 Hence, we tested whether autophagy downregulation impinges on this balance in gld-1 germline tumors. Contrary to the effect of autophagy depletion on neuronal differentiation, simultaneous knockdown of gld-1 and autophagy-related genes leads to a higher number of germ cells, indicative of increased tumor growth (Fig. 5A). In accordance, invasion of the head and vulva region by the tumor occurred earlier in autophagy-deficient animals than in controls (Tables S1 and S2). Moreover, quantitative analysis of gld-1 RNAi-induced tumors shows that nuclei density increases by ∼40% in the central and proximal part of the tumor in atg-7(bp411) animals (Fig. 5B and C), and large and dense accumulations of nuclei can be observed under these conditions (Fig. 5B, red arrows; Fig. 5E). Also, a large number of chromosome threads that emerge from apoptotic corpses can be observed. These show a ∼3-fold increase in atg-7(bp411) animals (Fig. 5C), particularly in the gonad turn (Fig. 5D) but also in the proximal part of the tumor (Fig. 5B and data not shown). However, upregulation of apoptosis cannot compensate for the strong upregulation of proliferation since the tumor apoptosis rate is very low (0.7 ± 0.1% apoptotic cells in atg-7(bp411) vs. 0.3 ± 0.1% in wild-type animals with gld-1 induced tumors).Figure 5.


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)

Modulation of autophagy affects tumor growth. (A) N2 L1 or L3 (in the case of let-363 RNAi) larvae treated with the indicated dsRNA(s) till the fourth d of adulthood and stained with the DNA-intercalating dye DAPI (4′,6′-diamidino-2-phenylindole). Left: Representative animals. Right: Enlargement of the head region (boxed areas on the left). Dashed lines indicate the outline of the animal, white lines indicate the gonadal basement membrane. Scale bars: 20 μm. (B) Cell density visualized by fluorescent histone reporters (H1 and H2B-mCherry fusion proteins) in central (left) and proximal (right) parts of gld-1 RNAi-induced germline tumors in wild type and atg-7(bp411) animals. 3D projections are shown. Scale bar: 10 μm. (C) Quantification of cells per area and apoptotic corpses per gonad turn. n = 5 animals each; *** P ≤ 0.001. (D) Gonad turn nuclei and apoptotic corpses in wild-type and atg-7(bp411) animals treated with gld-1 RNAi. 3D projections. Note the chromatin threads that can be observed on goad surfaces in atg-7(bp411) (surface projection, right). Scale bar: 5 μm. (E) Quantification of animals with cell clusters, indicative of high tumor cell density. Animals were treated with the respective RNAis and tumor arms were imaged and scored at d 3 of adulthood for the appearance of bright nuclei clusters (as indicated by red arrows in panel [B]).
© Copyright Policy - open-access
Related In: Results  -  Collection

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f0005: Modulation of autophagy affects tumor growth. (A) N2 L1 or L3 (in the case of let-363 RNAi) larvae treated with the indicated dsRNA(s) till the fourth d of adulthood and stained with the DNA-intercalating dye DAPI (4′,6′-diamidino-2-phenylindole). Left: Representative animals. Right: Enlargement of the head region (boxed areas on the left). Dashed lines indicate the outline of the animal, white lines indicate the gonadal basement membrane. Scale bars: 20 μm. (B) Cell density visualized by fluorescent histone reporters (H1 and H2B-mCherry fusion proteins) in central (left) and proximal (right) parts of gld-1 RNAi-induced germline tumors in wild type and atg-7(bp411) animals. 3D projections are shown. Scale bar: 10 μm. (C) Quantification of cells per area and apoptotic corpses per gonad turn. n = 5 animals each; *** P ≤ 0.001. (D) Gonad turn nuclei and apoptotic corpses in wild-type and atg-7(bp411) animals treated with gld-1 RNAi. 3D projections. Note the chromatin threads that can be observed on goad surfaces in atg-7(bp411) (surface projection, right). Scale bar: 5 μm. (E) Quantification of animals with cell clusters, indicative of high tumor cell density. Animals were treated with the respective RNAis and tumor arms were imaged and scored at d 3 of adulthood for the appearance of bright nuclei clusters (as indicated by red arrows in panel [B]).
Mentions: A balance between self-renewal and differentiation of stem cells is critical for proliferation control and maintenance of a stem cell pool in mammalian tissues.36 Hence, we tested whether autophagy downregulation impinges on this balance in gld-1 germline tumors. Contrary to the effect of autophagy depletion on neuronal differentiation, simultaneous knockdown of gld-1 and autophagy-related genes leads to a higher number of germ cells, indicative of increased tumor growth (Fig. 5A). In accordance, invasion of the head and vulva region by the tumor occurred earlier in autophagy-deficient animals than in controls (Tables S1 and S2). Moreover, quantitative analysis of gld-1 RNAi-induced tumors shows that nuclei density increases by ∼40% in the central and proximal part of the tumor in atg-7(bp411) animals (Fig. 5B and C), and large and dense accumulations of nuclei can be observed under these conditions (Fig. 5B, red arrows; Fig. 5E). Also, a large number of chromosome threads that emerge from apoptotic corpses can be observed. These show a ∼3-fold increase in atg-7(bp411) animals (Fig. 5C), particularly in the gonad turn (Fig. 5D) but also in the proximal part of the tumor (Fig. 5B and data not shown). However, upregulation of apoptosis cannot compensate for the strong upregulation of proliferation since the tumor apoptosis rate is very low (0.7 ± 0.1% apoptotic cells in atg-7(bp411) vs. 0.3 ± 0.1% in wild-type animals with gld-1 induced tumors).Figure 5.

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