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CTGF drives autophagy, glycolysis and senescence in cancer-associated fibroblasts via HIF1 activation, metabolically promoting tumor growth.

Capparelli C, Whitaker-Menezes D, Guido C, Balliet R, Pestell TG, Howell A, Sneddon S, Pestell RG, Martinez-Outschoorn U, Lisanti MP, Sotgia F - Cell Cycle (2012)

Bottom Line: In addition, loss of stromal Cav-1 results in the metabolic reprogramming of cancer-associated fibroblasts, with the induction of autophagy and glycolysis.Here, we show that CTGF exerts compartment-specific effects on tumorigenesis, depending on the cell-type.As loss of Cav-1 is a stromal marker of poor clinical outcome in women with primary breast cancer, dissecting the downstream signaling effects of Cav-1 are important for understanding disease pathogenesis, and identifying novel therapeutic targets.

View Article: PubMed Central - PubMed

Affiliation: The Jefferson Stem Cell Biology and Regenerative Medicine Center, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA.

ABSTRACT
Previous studies have demonstrated that loss of caveolin-1 (Cav-1) in stromal cells drives the activation of the TGF-β signaling, with increased transcription of TGF-β target genes, such as connective tissue growth factor (CTGF). In addition, loss of stromal Cav-1 results in the metabolic reprogramming of cancer-associated fibroblasts, with the induction of autophagy and glycolysis. However, it remains unknown if activation of the TGF-β / CTGF pathway regulates the metabolism of cancer-associated fibroblasts. Therefore, we investigated whether CTGF modulates metabolism in the tumor microenvironment. For this purpose, CTGF was overexpressed in normal human fibroblasts or MDA-MB-231 breast cancer cells. Overexpression of CTGF induces HIF-1α-dependent metabolic alterations, with the induction of autophagy/mitophagy, senescence, and glycolysis. Here, we show that CTGF exerts compartment-specific effects on tumorigenesis, depending on the cell-type. In a xenograft model, CTGF overexpressing fibroblasts promote the growth of co-injected MDA-MB-231 cells, without any increases in angiogenesis. Conversely, CTGF overexpression in MDA-MB-231 cells dramatically inhibits tumor growth in mice. Intriguingly, increased extracellular matrix deposition was seen in tumors with either fibroblast or MDA-MB-231 overexpression of CTGF. Thus, the effects of CTGF expression on tumor formation are independent of its extracellular matrix function, but rather depend on its ability to activate catabolic metabolism. As such, CTGF-mediated induction of autophagy in fibroblasts supports tumor growth via the generation of recycled nutrients, whereas CTGF-mediated autophagy in breast cancer cells suppresses tumor growth, via tumor cell self-digestion. Our studies shed new light on the compartment-specific role of CTGF in mammary tumorigenesis, and provide novel insights into the mechanism(s) generating a lethal tumor microenvironment in patients lacking stromal Cav-1. As loss of Cav-1 is a stromal marker of poor clinical outcome in women with primary breast cancer, dissecting the downstream signaling effects of Cav-1 are important for understanding disease pathogenesis, and identifying novel therapeutic targets.

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Figure 1. CTGF overexpression induces an autophagy/mitophagy program in fibroblasts. (A) Fibroblasts were stably-transfected with a CTGF or Lv-105 empty vector plasmid, using a lentiviral vector approach. Total proteins were isolated from transfected fibroblasts, and analyzed by immunoblotting to confirm CTGF expression. (B) Immunoblot analysis shows that CTGF overexpression induces the activation of autophagy/mitophagy in fibroblasts, as judged by increased expression levels of BNIP3, Beclin-1, Lamp-1 and LC3, as compared with control cells. The expression of β-actin was assessed for equal protein loading.
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Figure 1: Figure 1. CTGF overexpression induces an autophagy/mitophagy program in fibroblasts. (A) Fibroblasts were stably-transfected with a CTGF or Lv-105 empty vector plasmid, using a lentiviral vector approach. Total proteins were isolated from transfected fibroblasts, and analyzed by immunoblotting to confirm CTGF expression. (B) Immunoblot analysis shows that CTGF overexpression induces the activation of autophagy/mitophagy in fibroblasts, as judged by increased expression levels of BNIP3, Beclin-1, Lamp-1 and LC3, as compared with control cells. The expression of β-actin was assessed for equal protein loading.

Mentions: To investigate if CTGF plays a role in breast tumorigenesis, CTGF was stably overexpressed in stromal fibroblasts (Fig. 1A). Empty vector (Lv-105) control fibroblasts were generated in parallel. Then, CTGF overexpressing fibroblasts were analyzed by immunoblot blot analysis with a panel of autophagy/mitophagy markers. Figure 1B shows that CTGF overexpression induces the increased expression of LC3 and Beclin-1 (proteins involved in the formation and maturation of auto-phagosomes), Lamp-1 (a protein associated with auto-lysosomes and lysosomes) and BNIP3 (a mitophagy marker whose expression leads to reductions in mitochondrial mass and respiration).30 Therefore, CTGF expression is sufficient to induce autophagy and mitophagy in fibroblasts, downstream from a loss of stromal Cav-1.


CTGF drives autophagy, glycolysis and senescence in cancer-associated fibroblasts via HIF1 activation, metabolically promoting tumor growth.

Capparelli C, Whitaker-Menezes D, Guido C, Balliet R, Pestell TG, Howell A, Sneddon S, Pestell RG, Martinez-Outschoorn U, Lisanti MP, Sotgia F - Cell Cycle (2012)

Figure 1. CTGF overexpression induces an autophagy/mitophagy program in fibroblasts. (A) Fibroblasts were stably-transfected with a CTGF or Lv-105 empty vector plasmid, using a lentiviral vector approach. Total proteins were isolated from transfected fibroblasts, and analyzed by immunoblotting to confirm CTGF expression. (B) Immunoblot analysis shows that CTGF overexpression induces the activation of autophagy/mitophagy in fibroblasts, as judged by increased expression levels of BNIP3, Beclin-1, Lamp-1 and LC3, as compared with control cells. The expression of β-actin was assessed for equal protein loading.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3383589&req=5

Figure 1: Figure 1. CTGF overexpression induces an autophagy/mitophagy program in fibroblasts. (A) Fibroblasts were stably-transfected with a CTGF or Lv-105 empty vector plasmid, using a lentiviral vector approach. Total proteins were isolated from transfected fibroblasts, and analyzed by immunoblotting to confirm CTGF expression. (B) Immunoblot analysis shows that CTGF overexpression induces the activation of autophagy/mitophagy in fibroblasts, as judged by increased expression levels of BNIP3, Beclin-1, Lamp-1 and LC3, as compared with control cells. The expression of β-actin was assessed for equal protein loading.
Mentions: To investigate if CTGF plays a role in breast tumorigenesis, CTGF was stably overexpressed in stromal fibroblasts (Fig. 1A). Empty vector (Lv-105) control fibroblasts were generated in parallel. Then, CTGF overexpressing fibroblasts were analyzed by immunoblot blot analysis with a panel of autophagy/mitophagy markers. Figure 1B shows that CTGF overexpression induces the increased expression of LC3 and Beclin-1 (proteins involved in the formation and maturation of auto-phagosomes), Lamp-1 (a protein associated with auto-lysosomes and lysosomes) and BNIP3 (a mitophagy marker whose expression leads to reductions in mitochondrial mass and respiration).30 Therefore, CTGF expression is sufficient to induce autophagy and mitophagy in fibroblasts, downstream from a loss of stromal Cav-1.

Bottom Line: In addition, loss of stromal Cav-1 results in the metabolic reprogramming of cancer-associated fibroblasts, with the induction of autophagy and glycolysis.Here, we show that CTGF exerts compartment-specific effects on tumorigenesis, depending on the cell-type.As loss of Cav-1 is a stromal marker of poor clinical outcome in women with primary breast cancer, dissecting the downstream signaling effects of Cav-1 are important for understanding disease pathogenesis, and identifying novel therapeutic targets.

View Article: PubMed Central - PubMed

Affiliation: The Jefferson Stem Cell Biology and Regenerative Medicine Center, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA.

ABSTRACT
Previous studies have demonstrated that loss of caveolin-1 (Cav-1) in stromal cells drives the activation of the TGF-β signaling, with increased transcription of TGF-β target genes, such as connective tissue growth factor (CTGF). In addition, loss of stromal Cav-1 results in the metabolic reprogramming of cancer-associated fibroblasts, with the induction of autophagy and glycolysis. However, it remains unknown if activation of the TGF-β / CTGF pathway regulates the metabolism of cancer-associated fibroblasts. Therefore, we investigated whether CTGF modulates metabolism in the tumor microenvironment. For this purpose, CTGF was overexpressed in normal human fibroblasts or MDA-MB-231 breast cancer cells. Overexpression of CTGF induces HIF-1α-dependent metabolic alterations, with the induction of autophagy/mitophagy, senescence, and glycolysis. Here, we show that CTGF exerts compartment-specific effects on tumorigenesis, depending on the cell-type. In a xenograft model, CTGF overexpressing fibroblasts promote the growth of co-injected MDA-MB-231 cells, without any increases in angiogenesis. Conversely, CTGF overexpression in MDA-MB-231 cells dramatically inhibits tumor growth in mice. Intriguingly, increased extracellular matrix deposition was seen in tumors with either fibroblast or MDA-MB-231 overexpression of CTGF. Thus, the effects of CTGF expression on tumor formation are independent of its extracellular matrix function, but rather depend on its ability to activate catabolic metabolism. As such, CTGF-mediated induction of autophagy in fibroblasts supports tumor growth via the generation of recycled nutrients, whereas CTGF-mediated autophagy in breast cancer cells suppresses tumor growth, via tumor cell self-digestion. Our studies shed new light on the compartment-specific role of CTGF in mammary tumorigenesis, and provide novel insights into the mechanism(s) generating a lethal tumor microenvironment in patients lacking stromal Cav-1. As loss of Cav-1 is a stromal marker of poor clinical outcome in women with primary breast cancer, dissecting the downstream signaling effects of Cav-1 are important for understanding disease pathogenesis, and identifying novel therapeutic targets.

Show MeSH
Related in: MedlinePlus