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AMP-activated protein kinase is dispensable for maintaining ATP levels and for survival following inhibition of glycolysis, but promotes tumour engraftment of Ras-transformed fibroblasts.

Pelletier J, Roux D, Viollet B, Mazure NM, Pouysségur J - Oncotarget (2015)

Bottom Line: We report that MCT1 inhibition combined with Mct4 gene disruption severely reduced glycolysis and tumour growth without affecting ATP levels.We therefore propose that the intracellular acidification resulting from lactic acid sequestration mimicks AMPK by blocking mTORC1, a major component of an ATP consuming pathway, thereby preventing 'ATP crisis'.These findings demonstrated that blockade of lactate transport is an efficient anti-cancer strategy that highlights the potential in targeting Mct4 in a context of impaired AMPK activity.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research on Cancer and Ageing of Nice (IRCAN), University of Nice-Sophia Antipolis, CNRS UMR INSERM, Centre Antoine Lacassagne, Nice, France.

ABSTRACT
Lactic acid generated by highly glycolytic tumours is exported by the MonoCarboxylate Transporters, MCT1 and MCT4, to maintain pHi and energy homeostasis. We report that MCT1 inhibition combined with Mct4 gene disruption severely reduced glycolysis and tumour growth without affecting ATP levels. Because of the key role of the 5'-AMP-activated protein kinase (AMPK) in energy homeostasis, we hypothesized that targeting glycolysis (MCT-blockade) in AMPK- (Ampk(-/-)) cells should kill tumour cells from 'ATP crisis'. We show that Ampk(-/-)-Ras-transformed mouse embryonic fibroblasts (MEFs) maintained ATP levels and viability when glycolysis was inhibited. In MCT-inhibited MEFs treated with OXPHOS inhibitors the ATP level and viability collapsed in both Ampk(+/+) and Ampk(-/-) cells. We therefore propose that the intracellular acidification resulting from lactic acid sequestration mimicks AMPK by blocking mTORC1, a major component of an ATP consuming pathway, thereby preventing 'ATP crisis'. Finally we showed that genetic disruption of Mct4 and/or Ampk dramatically reduced tumourigenicity in a xenograft mouse model suggesting a crucialrolefor these two actors in establishment of tumours in a nutrient-deprived environment. These findings demonstrated that blockade of lactate transport is an efficient anti-cancer strategy that highlights the potential in targeting Mct4 in a context of impaired AMPK activity.

No MeSH data available.


Related in: MedlinePlus

Dual knockout of Ampk (Ampk−/−) and Mct4 (Mct4−/−) dramatically decreased xenograft tumour development(a) In vivo xenograft assays were performed by injecting s.c. into the back of athymic nude mice 1×106 viable and individual tumour Ampk+/+ (Ampk+/+) or Ampk−/− (Ampk−/−) MEFs expressing (Mct4+/+) or not (Mct4−/−) MCT4. Xenograft growth was determined by measuring the tumour volume. In vivo experiments were repeated twice. Five mice were studied per condition. (b) Immunohistological confirmation of the expression of Phospho-AMPK (P-AMPK) and Phospho-ACC (P-ACC) in the corresponding Ampk+/+ and Ampk−/− tumour xenografts (Magnification: 20×).
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Figure 5: Dual knockout of Ampk (Ampk−/−) and Mct4 (Mct4−/−) dramatically decreased xenograft tumour development(a) In vivo xenograft assays were performed by injecting s.c. into the back of athymic nude mice 1×106 viable and individual tumour Ampk+/+ (Ampk+/+) or Ampk−/− (Ampk−/−) MEFs expressing (Mct4+/+) or not (Mct4−/−) MCT4. Xenograft growth was determined by measuring the tumour volume. In vivo experiments were repeated twice. Five mice were studied per condition. (b) Immunohistological confirmation of the expression of Phospho-AMPK (P-AMPK) and Phospho-ACC (P-ACC) in the corresponding Ampk+/+ and Ampk−/− tumour xenografts (Magnification: 20×).

Mentions: We then investigated the behaviour of these cells in a tumour context. Ampk+/+ Mct4+/+ control MEFs showed rapid tumour growth, up to 200mm3 after 12 days (±3) and greater than 1000mm3 after 21 days of injection (Figure 5a). We observed a high latency in tumour growth with Ampk−/−Mct4+/+ MEFs as the tumours reached 200mm3 after 44 days (±6) post-injection. However, after this period, the rate of tumour growth was identical for Ampk+/+ and Ampk−/− MEFs (Figure 5a). Moreover, Ampk+/+ Mct4−/− MEF showed slowed tumourigenicity but not tumour growth as Ampk+/+ Mct4−/− MEFs exhibited a tumour volume of 200mm3 to 1000mm3 in 33 days (±6) and 40 days (±6), respectively (Figure 5a). Ampk−/−Mct4−/− MEF-derived tumours grew much slower (Figure 5a). The absence of AMPK activity in MEF-derived tumuors was confirmed (Figure 5b).


AMP-activated protein kinase is dispensable for maintaining ATP levels and for survival following inhibition of glycolysis, but promotes tumour engraftment of Ras-transformed fibroblasts.

Pelletier J, Roux D, Viollet B, Mazure NM, Pouysségur J - Oncotarget (2015)

Dual knockout of Ampk (Ampk−/−) and Mct4 (Mct4−/−) dramatically decreased xenograft tumour development(a) In vivo xenograft assays were performed by injecting s.c. into the back of athymic nude mice 1×106 viable and individual tumour Ampk+/+ (Ampk+/+) or Ampk−/− (Ampk−/−) MEFs expressing (Mct4+/+) or not (Mct4−/−) MCT4. Xenograft growth was determined by measuring the tumour volume. In vivo experiments were repeated twice. Five mice were studied per condition. (b) Immunohistological confirmation of the expression of Phospho-AMPK (P-AMPK) and Phospho-ACC (P-ACC) in the corresponding Ampk+/+ and Ampk−/− tumour xenografts (Magnification: 20×).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494908&req=5

Figure 5: Dual knockout of Ampk (Ampk−/−) and Mct4 (Mct4−/−) dramatically decreased xenograft tumour development(a) In vivo xenograft assays were performed by injecting s.c. into the back of athymic nude mice 1×106 viable and individual tumour Ampk+/+ (Ampk+/+) or Ampk−/− (Ampk−/−) MEFs expressing (Mct4+/+) or not (Mct4−/−) MCT4. Xenograft growth was determined by measuring the tumour volume. In vivo experiments were repeated twice. Five mice were studied per condition. (b) Immunohistological confirmation of the expression of Phospho-AMPK (P-AMPK) and Phospho-ACC (P-ACC) in the corresponding Ampk+/+ and Ampk−/− tumour xenografts (Magnification: 20×).
Mentions: We then investigated the behaviour of these cells in a tumour context. Ampk+/+ Mct4+/+ control MEFs showed rapid tumour growth, up to 200mm3 after 12 days (±3) and greater than 1000mm3 after 21 days of injection (Figure 5a). We observed a high latency in tumour growth with Ampk−/−Mct4+/+ MEFs as the tumours reached 200mm3 after 44 days (±6) post-injection. However, after this period, the rate of tumour growth was identical for Ampk+/+ and Ampk−/− MEFs (Figure 5a). Moreover, Ampk+/+ Mct4−/− MEF showed slowed tumourigenicity but not tumour growth as Ampk+/+ Mct4−/− MEFs exhibited a tumour volume of 200mm3 to 1000mm3 in 33 days (±6) and 40 days (±6), respectively (Figure 5a). Ampk−/−Mct4−/− MEF-derived tumours grew much slower (Figure 5a). The absence of AMPK activity in MEF-derived tumuors was confirmed (Figure 5b).

Bottom Line: We report that MCT1 inhibition combined with Mct4 gene disruption severely reduced glycolysis and tumour growth without affecting ATP levels.We therefore propose that the intracellular acidification resulting from lactic acid sequestration mimicks AMPK by blocking mTORC1, a major component of an ATP consuming pathway, thereby preventing 'ATP crisis'.These findings demonstrated that blockade of lactate transport is an efficient anti-cancer strategy that highlights the potential in targeting Mct4 in a context of impaired AMPK activity.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research on Cancer and Ageing of Nice (IRCAN), University of Nice-Sophia Antipolis, CNRS UMR INSERM, Centre Antoine Lacassagne, Nice, France.

ABSTRACT
Lactic acid generated by highly glycolytic tumours is exported by the MonoCarboxylate Transporters, MCT1 and MCT4, to maintain pHi and energy homeostasis. We report that MCT1 inhibition combined with Mct4 gene disruption severely reduced glycolysis and tumour growth without affecting ATP levels. Because of the key role of the 5'-AMP-activated protein kinase (AMPK) in energy homeostasis, we hypothesized that targeting glycolysis (MCT-blockade) in AMPK- (Ampk(-/-)) cells should kill tumour cells from 'ATP crisis'. We show that Ampk(-/-)-Ras-transformed mouse embryonic fibroblasts (MEFs) maintained ATP levels and viability when glycolysis was inhibited. In MCT-inhibited MEFs treated with OXPHOS inhibitors the ATP level and viability collapsed in both Ampk(+/+) and Ampk(-/-) cells. We therefore propose that the intracellular acidification resulting from lactic acid sequestration mimicks AMPK by blocking mTORC1, a major component of an ATP consuming pathway, thereby preventing 'ATP crisis'. Finally we showed that genetic disruption of Mct4 and/or Ampk dramatically reduced tumourigenicity in a xenograft mouse model suggesting a crucialrolefor these two actors in establishment of tumours in a nutrient-deprived environment. These findings demonstrated that blockade of lactate transport is an efficient anti-cancer strategy that highlights the potential in targeting Mct4 in a context of impaired AMPK activity.

No MeSH data available.


Related in: MedlinePlus