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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

Characterization of tumor cells and autophagosomes. (A) Tumor cells as visualized by their plasma membranes (left, PH domain of PLCd1 fused to GFP) or their nuclei (histone-mCherry fusion proteins). Scale bar: 10 μm. (B) Left: Autophagosomes in tumor cells as visualized by GFP::LGG-1, a representative maximum projection of a central tumor area is shown, scale bar: 10 μm. Top right: Quantification of numbers of autophagosomes per cell. Bottom right: Quantification of autophagosome size. Quantifications were performed by manual counting/measurements. (C) 3D reconstruction of cell shapes of those cells in the germline tumor expressing GFP::LGG-1. Top: Original microscopy 3D projection data, scale bar: 5 μm; bottom: 3D reconstruction performed in imod (see Methods). (D) Movement of autophagosomes inside tumor cells. Left: Stills from time-lapse recordings, the dashed lines mark the initial position of an autophagosome, scale bar: 5 μm. Right: Magnified data from autophagosome tracking using Endrov (see Methods). Autophagosome paths are shown as black lines. Note that the movement of the bottom autophagosome is due to the sample shifting (see Movie S1). All panels in Fig. 2 show animals at the d 3 of adulthood.
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f0002: Characterization of tumor cells and autophagosomes. (A) Tumor cells as visualized by their plasma membranes (left, PH domain of PLCd1 fused to GFP) or their nuclei (histone-mCherry fusion proteins). Scale bar: 10 μm. (B) Left: Autophagosomes in tumor cells as visualized by GFP::LGG-1, a representative maximum projection of a central tumor area is shown, scale bar: 10 μm. Top right: Quantification of numbers of autophagosomes per cell. Bottom right: Quantification of autophagosome size. Quantifications were performed by manual counting/measurements. (C) 3D reconstruction of cell shapes of those cells in the germline tumor expressing GFP::LGG-1. Top: Original microscopy 3D projection data, scale bar: 5 μm; bottom: 3D reconstruction performed in imod (see Methods). (D) Movement of autophagosomes inside tumor cells. Left: Stills from time-lapse recordings, the dashed lines mark the initial position of an autophagosome, scale bar: 5 μm. Right: Magnified data from autophagosome tracking using Endrov (see Methods). Autophagosome paths are shown as black lines. Note that the movement of the bottom autophagosome is due to the sample shifting (see Movie S1). All panels in Fig. 2 show animals at the d 3 of adulthood.

Mentions: Consistent with germline tumors containing cells expressing different fate markers,2,4 we also observed heterogenetity in nuclear shape, size and nucleolar structure as well as cell shape (Fig. 2A). Importantly, germline tumor cells show a heterogenous pattern of GFP::LGG-1 expression, with many cells showing elevated cytoplasmic expression and about 90% of them contain clearly discernible autophagosomes with rather uniform size of around 0.5 μm (Fig. 2B). Thus, unlike what has been reported for larval seam cells where only few autophagosomes can be detected, germline tumor cells show a distribution of autophagosome numbers with 4 or 5 autophagosomes per cell on average (Fig. 2B). Moreover, many cells expressing GFP::LGG-1 have elongated protrusions which are often connected to neighboring cells, thereby resembling neurons in their shape (Fig. 2C). By performing time-lapse microscopy of germline tumors, we also found that while most tumor cells show little intracellular autophagosome movement, in a few tumor cells with high levels of GFP::LGG-1, fast, random-walking autophagosomes can be observed (Fig. 2D; Movie S1).Figure 2.


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)

Characterization of tumor cells and autophagosomes. (A) Tumor cells as visualized by their plasma membranes (left, PH domain of PLCd1 fused to GFP) or their nuclei (histone-mCherry fusion proteins). Scale bar: 10 μm. (B) Left: Autophagosomes in tumor cells as visualized by GFP::LGG-1, a representative maximum projection of a central tumor area is shown, scale bar: 10 μm. Top right: Quantification of numbers of autophagosomes per cell. Bottom right: Quantification of autophagosome size. Quantifications were performed by manual counting/measurements. (C) 3D reconstruction of cell shapes of those cells in the germline tumor expressing GFP::LGG-1. Top: Original microscopy 3D projection data, scale bar: 5 μm; bottom: 3D reconstruction performed in imod (see Methods). (D) Movement of autophagosomes inside tumor cells. Left: Stills from time-lapse recordings, the dashed lines mark the initial position of an autophagosome, scale bar: 5 μm. Right: Magnified data from autophagosome tracking using Endrov (see Methods). Autophagosome paths are shown as black lines. Note that the movement of the bottom autophagosome is due to the sample shifting (see Movie S1). All panels in Fig. 2 show animals at the d 3 of adulthood.
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f0002: Characterization of tumor cells and autophagosomes. (A) Tumor cells as visualized by their plasma membranes (left, PH domain of PLCd1 fused to GFP) or their nuclei (histone-mCherry fusion proteins). Scale bar: 10 μm. (B) Left: Autophagosomes in tumor cells as visualized by GFP::LGG-1, a representative maximum projection of a central tumor area is shown, scale bar: 10 μm. Top right: Quantification of numbers of autophagosomes per cell. Bottom right: Quantification of autophagosome size. Quantifications were performed by manual counting/measurements. (C) 3D reconstruction of cell shapes of those cells in the germline tumor expressing GFP::LGG-1. Top: Original microscopy 3D projection data, scale bar: 5 μm; bottom: 3D reconstruction performed in imod (see Methods). (D) Movement of autophagosomes inside tumor cells. Left: Stills from time-lapse recordings, the dashed lines mark the initial position of an autophagosome, scale bar: 5 μm. Right: Magnified data from autophagosome tracking using Endrov (see Methods). Autophagosome paths are shown as black lines. Note that the movement of the bottom autophagosome is due to the sample shifting (see Movie S1). All panels in Fig. 2 show animals at the d 3 of adulthood.
Mentions: Consistent with germline tumors containing cells expressing different fate markers,2,4 we also observed heterogenetity in nuclear shape, size and nucleolar structure as well as cell shape (Fig. 2A). Importantly, germline tumor cells show a heterogenous pattern of GFP::LGG-1 expression, with many cells showing elevated cytoplasmic expression and about 90% of them contain clearly discernible autophagosomes with rather uniform size of around 0.5 μm (Fig. 2B). Thus, unlike what has been reported for larval seam cells where only few autophagosomes can be detected, germline tumor cells show a distribution of autophagosome numbers with 4 or 5 autophagosomes per cell on average (Fig. 2B). Moreover, many cells expressing GFP::LGG-1 have elongated protrusions which are often connected to neighboring cells, thereby resembling neurons in their shape (Fig. 2C). By performing time-lapse microscopy of germline tumors, we also found that while most tumor cells show little intracellular autophagosome movement, in a few tumor cells with high levels of GFP::LGG-1, fast, random-walking autophagosomes can be observed (Fig. 2D; Movie S1).Figure 2.

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