Most cancer cells utilize aerobic glycolysis for their energy
needs (Warburg effect), despite the fact that this pathway is an
inefficient way to generate adenosine 50-triphosphate (ATP) when
oxygen is abundant [1–3]. It is still not well understood as why
such a less efficient metabolism is selected by proliferating cancer
cells. One reasonable explanation would be that inefficient ATP
production happens only when energy resources are scarce, such
as in areas of the tumor where low blood flow leads to low nutrient,
hypoxic and an acidotic conditions [4]. However, some cancer
cells appear to rely on glycolytic metabolism even before they are
exposed to such harsh conditions [5–8]. Some consider that the
adoption of aerobic glycolysis by cancer cells is driven by tumor
hypoxia [9] while others consider that aerobic glycolysis might
be multi-factorial and driven by oncogenes, tumor suppressors,
mtDNA mutations and other factors [9–11].
In this study, we aimed to address whether the Warburg effect
might be a consequence of damage which occurs in hypovascularized
regions of tumors that create hypoxia, glucopenia and acidosis.
We demonstrate here that cancer cells that recover from
such damages exhibit mitochondrial structural changes including
development of a primordial type as evidenced by ballooning
and remodeling of cristae. These changes are associated with
decreased copy number of mtDNA, increased expression of glycolytic
enzymes, activation of glycolytic system of energy production,
increased ATP synthesis, increased tolerance to damage as well as
rapid in vitro and in vivo proliferation. We also show that cells that
recover from damage endured in vivo are also highly glycolytic and
exhibit a high rate of cell proliferation. These findings suggest a
role for damage-recovery in the adoption of ‘‘Warburg effect’’ by
the tumor cells. Furthermore, these data indicate that cancer cells
that emerge after recovery from damage, display new metabolic
characteristics consistent with a higher degree of malignant behavior
as evidenced by damage tolerance and increased rate of cell
proliferation.
Most cancer cells utilize aerobic glycolysis for their energy
needs (Warburg effect), despite the fact that this pathway is an
inefficient way to generate adenosine 50-triphosphate (ATP) when
oxygen is abundant [1–3]. It is still not well understood as why
such a less efficient metabolism is selected by proliferating cancer
cells. One reasonable explanation would be that inefficient ATP
production happens only when energy resources are scarce, such
as in areas of the tumor where low blood flow leads to low nutrient,
hypoxic and an acidotic conditions [4]. However, some cancer
cells appear to rely on glycolytic metabolism even before they are
exposed to such harsh conditions [5–8]. Some consider that the
adoption of aerobic glycolysis by cancer cells is driven by tumor
hypoxia [9] while others consider that aerobic glycolysis might
be multi-factorial and driven by oncogenes, tumor suppressors,
mtDNA mutations and other factors [9–11].
In this study, we aimed to address whether the Warburg effect
might be a consequence of damage which occurs in hypovascularized
regions of tumors that create hypoxia, glucopenia and acidosis.
We demonstrate here that cancer cells that recover from
such damages exhibit mitochondrial structural changes including
development of a primordial type as evidenced by ballooning
and remodeling of cristae. These changes are associated with
decreased copy number of mtDNA, increased expression of glycolytic
enzymes, activation of glycolytic system of energy production,
increased ATP synthesis, increased tolerance to damage as well as
rapid in vitro and in vivo proliferation. We also show that cells that
recover from damage endured in vivo are also highly glycolytic and
exhibit a high rate of cell proliferation. These findings suggest a
role for damage-recovery in the adoption of ‘‘Warburg effect’’ by
the tumor cells. Furthermore, these data indicate that cancer cells
that emerge after recovery from damage, display new metabolic
characteristics consistent with a higher degree of malignant behavior
as evidenced by damage tolerance and increased rate of cell
proliferation.
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