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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 8. MDA-MB-231 cells overexpressing CTGF display the induction of autophagy/mitophagy, with HIF-1α activation. To study if CTGF expression has any compartment-specific effects, CTGF was overexpressed in MDA-MB-231 cells. (A) Immunoblot analysis was performed on total protein lysates to confirm CTGF overexpression. (B, C) MDA-MB-231 cells overexpressing CTGF show activation of an autophagy/mitophagy program. Immunoblot analysis on CTGF- and control-MDA-MB-231 cells reveals that CTGF significantly increases the expression levels of several proteins involved in mitophagy (BNIP3) and autophagy (Lamp-1, Beclin-1, cathepsin B and LC3) under (B) basal condition or (C) after 2h of nutrient starvation. (D) Immunblot analysis of total protein lysates from control and CTGF-MDA-MB-231 cells shows that CTGF expression induces the activation of HIF-1α in MDA-MB-231 cells. Two exposures are shown. For all, β-actin was used as control for equal protein loading. (E) ROS assay performed on control- and CTGF-MDA-MB-231 cells reveals that CTGF expression induces a 20% increase in ROS production.
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Figure 8: Figure 8. MDA-MB-231 cells overexpressing CTGF display the induction of autophagy/mitophagy, with HIF-1α activation. To study if CTGF expression has any compartment-specific effects, CTGF was overexpressed in MDA-MB-231 cells. (A) Immunoblot analysis was performed on total protein lysates to confirm CTGF overexpression. (B, C) MDA-MB-231 cells overexpressing CTGF show activation of an autophagy/mitophagy program. Immunoblot analysis on CTGF- and control-MDA-MB-231 cells reveals that CTGF significantly increases the expression levels of several proteins involved in mitophagy (BNIP3) and autophagy (Lamp-1, Beclin-1, cathepsin B and LC3) under (B) basal condition or (C) after 2h of nutrient starvation. (D) Immunblot analysis of total protein lysates from control and CTGF-MDA-MB-231 cells shows that CTGF expression induces the activation of HIF-1α in MDA-MB-231 cells. Two exposures are shown. For all, β-actin was used as control for equal protein loading. (E) ROS assay performed on control- and CTGF-MDA-MB-231 cells reveals that CTGF expression induces a 20% increase in ROS production.

Mentions: To evaluate if the role of CTGF in tumorigenesis is compartment-specific, we overexpressed CTGF in MDA-MB-231 cells (Fig. 8A). We next investigated whether CTGF also induces autophagy/mitophagy in epithelial cancer cells. Immunoblot analysis demonstrated that MDA-MB-231 cells overexpressing CTGF show the upregulation of several autophagy/mitophagy markers under basal condition (BNIP3, Lamp-1 and cathepsin B) (Fig. 8B) or upon nutrient-starvation (Beclin-1 and LC3) (Fig. 8C), indicating that CTGF can activate autophagy also in breast cancer epithelial cells. However, no changes in L-lactate production were observed in MDA-MB-231 cells overexpressing CTGF (data not shown).


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 8. MDA-MB-231 cells overexpressing CTGF display the induction of autophagy/mitophagy, with HIF-1α activation. To study if CTGF expression has any compartment-specific effects, CTGF was overexpressed in MDA-MB-231 cells. (A) Immunoblot analysis was performed on total protein lysates to confirm CTGF overexpression. (B, C) MDA-MB-231 cells overexpressing CTGF show activation of an autophagy/mitophagy program. Immunoblot analysis on CTGF- and control-MDA-MB-231 cells reveals that CTGF significantly increases the expression levels of several proteins involved in mitophagy (BNIP3) and autophagy (Lamp-1, Beclin-1, cathepsin B and LC3) under (B) basal condition or (C) after 2h of nutrient starvation. (D) Immunblot analysis of total protein lysates from control and CTGF-MDA-MB-231 cells shows that CTGF expression induces the activation of HIF-1α in MDA-MB-231 cells. Two exposures are shown. For all, β-actin was used as control for equal protein loading. (E) ROS assay performed on control- and CTGF-MDA-MB-231 cells reveals that CTGF expression induces a 20% increase in ROS production.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 8: Figure 8. MDA-MB-231 cells overexpressing CTGF display the induction of autophagy/mitophagy, with HIF-1α activation. To study if CTGF expression has any compartment-specific effects, CTGF was overexpressed in MDA-MB-231 cells. (A) Immunoblot analysis was performed on total protein lysates to confirm CTGF overexpression. (B, C) MDA-MB-231 cells overexpressing CTGF show activation of an autophagy/mitophagy program. Immunoblot analysis on CTGF- and control-MDA-MB-231 cells reveals that CTGF significantly increases the expression levels of several proteins involved in mitophagy (BNIP3) and autophagy (Lamp-1, Beclin-1, cathepsin B and LC3) under (B) basal condition or (C) after 2h of nutrient starvation. (D) Immunblot analysis of total protein lysates from control and CTGF-MDA-MB-231 cells shows that CTGF expression induces the activation of HIF-1α in MDA-MB-231 cells. Two exposures are shown. For all, β-actin was used as control for equal protein loading. (E) ROS assay performed on control- and CTGF-MDA-MB-231 cells reveals that CTGF expression induces a 20% increase in ROS production.
Mentions: To evaluate if the role of CTGF in tumorigenesis is compartment-specific, we overexpressed CTGF in MDA-MB-231 cells (Fig. 8A). We next investigated whether CTGF also induces autophagy/mitophagy in epithelial cancer cells. Immunoblot analysis demonstrated that MDA-MB-231 cells overexpressing CTGF show the upregulation of several autophagy/mitophagy markers under basal condition (BNIP3, Lamp-1 and cathepsin B) (Fig. 8B) or upon nutrient-starvation (Beclin-1 and LC3) (Fig. 8C), indicating that CTGF can activate autophagy also in breast cancer epithelial cells. However, no changes in L-lactate production were observed in MDA-MB-231 cells overexpressing CTGF (data not shown).

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