The metabolic theory in detail: understanding Laurent Schwartz's model

The starting point: the cell in energy "distress"

At the heart of the theory lies the mitochondrion, the cell's energy factory. Schwartz proposes that the onset of cancer often begins with mitochondrial stress.

1. The initial insult and the glycolytic switch

A normal cell uses its mitochondria to burn glucose with oxygen (respiration), producing a great deal of energy (ATP) and little waste. Schwartz posits that various insults (chronic inflammation, chemical carcinogens, viruses, radiation, or even excess sugar) eventually damage the respiratory function of the mitochondrion.

Faced with this potential energy "failure", the cell has only one option in order to survive: to switch to an archaic but robust back-up mode, fermentative glycolysis. This is the famous "Warburg effect". The cell begins to consume glucose in large quantities and to ferment it, even when oxygen is present.

2. The vicious circle of acidity and selective pressure

This is where Schwartz's model becomes particularly interesting. This metabolic switch is not neutral:

• Fermentation produces large amounts of lactic acid (lactate).
• The cell must expel this acid in order not to die, thereby acidifying its immediate microenvironment.

According to Schwartz, this extracellular acidity acts as a powerful selective filter (a Darwinian pressure). Normal cells cannot tolerate this acidic milieu and either die or become quiescent. Only those cells able to mutate so as to withstand the acid survive.

Thus the "abnormal" metabolism creates the very conditions that select for genetic mutations (such as the loss of the p53 gene, the guardian of the genome). In this view, the genetic mutations are real, but they are the adaptive response to an initial metabolic problem, rather than the primary cause appearing out of the blue.

3. The blocking of differentiation

A normal cell is born, fulfils its function (differentiates), then dies (apoptosis). A cancer cell, by contrast, remains locked in an immature state and divides without end.

Schwartz links this to energy: differentiation requires a stable and complex mitochondrial energy supply. A cell running solely on "back-up mode" (glycolysis) simply does not have the energy "bandwidth" or the redox signals needed in order to differentiate. It remains stuck in "survival/proliferation" mode.

Osmotic pressure: a physical perspective

An original aspect of Schwartz's theory is that it incorporates basic physics. A cancer cell is often a turgid cell, swollen with water, with a high internal pressure.

• Glycolysis accumulates osmolytes (molecules that draw in water) within the cell.
• This high internal pressure physically forces cell division (mitosis).
• For Schwartz, treating cancer also means "deflating" the cell, reducing this osmotic pressure by normalising the metabolism.

Why is this theory attractive and pertinent?

It explains the partial failure of targeted therapies

If cancer is a purely genetic disease, each mutation calls for a different drug. But tumours mutate constantly, developing resistance. If the underlying problem is metabolic (a "failure" common to all tumour cells), then a universal metabolic approach could in theory circumvent the genetic resistances.

It rehabilitates simple molecules

If the aim is to "repair" mitochondrial respiration or to reduce acidity, complex gene therapies are not necessarily required. Simple molecules capable of accepting electrons (such as methylene blue) or of altering the pH could have a surprising efficacy.

The limitations and grey areas yet to be explored

Of course, this theory is not accepted by everyone, and there remain areas to be clarified by research:

• The chicken or the egg? Modern molecular biology shows that certain genetic mutations (oncogenes) can trigger the metabolic switch directly. The relationship is probably bidirectional (genetics ↔ metabolism), whereas Schwartz places a great deal of emphasis on the primacy of metabolism.
• Mitochondrial complexity: not all tumours have defective mitochondria to the same degree. Some tumours even make very good use of their mitochondria. The model no doubt applies better to certain cancers than to others.

Why is it not the dominant paradigm?

That is the central question. If this theory is coherent, why is it not at the heart of worldwide research?

The answer is probably systemic and economic as much as scientific:

• The inertia of research: for the past 40 years, research funding has been massively directed towards genetics. Changing paradigm takes time.
• The lack of profitability: validating this theory would often entail using old, non-patentable molecules (methylene blue, lipoic acid, hydroxycitrate). The pharmaceutical industry, the principal driver of costly clinical trials, has no financial interest in proving that a combination of generic molecules costing 10 euros a month can stabilise a cancer. This is not a conspiracy, it is an economic reality of the market: without a patent, there is no return on investment to fund phase 3 studies.

Conclusion

The metabolic theory set out in detail by Schwartz is a robust and stimulating intellectual construction. It offers a different reading grid that does not deny the observed facts (mutations, tumours), but connects them in a different way. It opens the door to adjuvant metabolic treatments which, in an ideal world, would deserve to be tested with the same rigour and the same budgets as the new gene therapies.