Altered metabolism in cancer cells is suspected to contribute to chemoresistance but the precise mechanisms are unclear. Here we show that intracellular ATP levels are a core determinant in the development of acquired cross-drug resistance of human colon cancer cells that harbor different genetic backgrounds. Drug-resistant cells were characterized by defective mitochondrial ATP production, elevated aerobic glycolysis, higher absolute levels of intracellular ATP and enhanced HIF-1α-mediated signaling. Interestingly, direct delivery of ATP into cross-chemoresistant cells destabilized HIF-1α and inhibited glycolysis. Thus, drug-resistant cells exhibit a greater “ATP debt” defined as the extra amount of ATP needed to maintain homeostasis of survival pathways under genotoxic stress. Direct delivery of ATP was sufficient to render drug-sensitive cells drug resistant. Conversely, depleting ATP by cell treatment with an inhibitor of glycolysis, 3-bromopyruvate, was sufficient to sensitize cells cross-resistant to multiple chemotherapeutic drugs. In revealing intracellular ATP levels are a core determinant of chemoresistance in colon cancer cells, our findings may offer a foundation for new improvements to colon cancer treatment.

Breast cancer brain metastasis is resistant to therapy and a particularly poor prognostic feature in patient survival. Altered metabolism is a common feature of cancer cells but little is known as to what metabolic changes benefit breast cancer brain metastases. We found that brain-metastatic breast cancer cells evolved the ability to survive and proliferate independent of glucose due to enhanced gluconeogenesis and oxidations of glutamine and branched chain amino acids, which together sustain the non-oxidative pentose pathway for purine synthesis. Silencing expression of fructose-1,6-bisphosphatases (FBPs) in brain metastatic cells reduced their viability and improved the survival of metastasis-bearing immunocompetent hosts. Clinically, we showed that brain metastases from human breast cancer patients expressed higher levels of FBP and glycogen than the corresponding primary tumors. Together, our findings identify a critical metabolic condition required to sustain brain metastasis, and suggest that targeting gluconeogenesis may help eradicate this deadly feature in advanced breast cancer patients.

We show that the friction force varies with the sliding velocity in a manner that depends on the chemical nature of the interface. Surfaces terminated with the hydrogen acceptor and donor moieties capable of forming H-bond networks exhibit a friction that decreases with sliding velocity, a behavior that is opposite to that of surfaces where no such networks can form. We explain the results with a model where the domains of glassy H-bond networks are disrupted at a critical applied stress leading to slippage.