Cancer cells need food to survive and grow. They're very good at getting it, too, even when nutrients are scarce. Many scientists have tried killing cancer cells by taking away their favourite food, a sugar called glucose.
This treatment approach not only fails to work, it backfires - glucose-starved tumours actually get more aggressive.
In a study published in the journal Cell, researchers discovered that a protein called PKC-zeta is responsible for this paradox. The research suggests that glucose depletion therapies might work against tumours as long as the cancer cells are producing PKC-zeta, a critical regulator of tumour metabolism
According to this study, when PKC-zeta is missing from cancer cells, tumours are able to use alternative nutrients. What's more, the lower the PKC-zeta levels, the more aggressive the tumour.
"We found an interesting correlation in colon cancers -- if a patient's tumour doesn't produce PKC-zeta, he has a poorer prognosis than a similar patient with the protein. We looked specifically at colon cancer in this study, but it's likely also true for other tumour types," said Jorge Moscat, a professor at Sanford-Burnham. Maria Diaz-Meco.
PKC-zeta keeps tumours addicted to glucose, and under control Although most cancer cells love glucose, tumours lacking PKC grow even better in the absence of this nutrient.
Using human tumour samples and a mouse model of colon cancer, Moscat and his team determined this growth-without-glucose paradox is because PKC-deficient tumours are able to reprogramme their metabolism to use glutamine, another nutrient, instead.
Without PKC-zeta around to keep them addicted to glucose, these tumours kick-start a new metabolic pathway. This altered metabolism helps PKC-zeta -deficient cancer cells survive in conditions that would otherwise be lethal.