An energy-carrying molecule present in all cells. ATP fuels cellular processes, including biosynthetic reactions, motility, and cell division by transferring one or more of its phosphate groups to another molecule (a process called phosphorylation).

An intracellular degradation system involved in the disassembly and recycling of unnecessary or dysfunctional cellular components. Autophagy participates in cell death, a process known as autophagic dell death. Prolonged fasting is a robust initiator of autophagy and may help protect against cancer and even aging by reducing the burden of abnormal cells.

The relationship between autophagy and cancer is complex, however. Autophagy may prevent the survival of pre-malignant cells, but can also be hijacked as a malignant adaptation by cancer, providing a useful means to scavenge resources needed for further growth.

An organism’s ability to maintain its internal environment within defined limits that allow it to survive. Homeostasis involves self-regulating processes that return critical bodily systems to a particular “set point” within a narrow range of operation, consistent with the organism’s survival.

A type of white blood cell. Leukocytes are involved in protecting the body against foreign substances, microbes, and infectious diseases. They are produced or stored in various locations throughout the body, including the thymus, spleen, lymph nodes, and bone marrow, and comprise approximately 1 percent of the total blood volume in a healthy adult. Leukocytes are distinguished from other blood cells by the fact that they retain their nuclei. A cycle of prolonged fasting has been shown in animal research to reduce the number of white blood cells by nearly one-third, a phenomenon that is then fully reversed after refeeding.^[1]

The thousands of biochemical processes that run all of the various cellular processes that produce energy. Since energy generation is so fundamental to all other processes, in some cases the word metabolism may refer more broadly to the sum of all chemical reactions in the cell.

A gene that has the potential to cause cancer. A proto-oncogene is a normal gene that regulates cell growth and proliferation but if it acquires a mutation that keeps it active all the time it can become an oncogene that allows cancer cells to survive when they otherwise would have died.

An oncogene is a mutated form of a gene ordinarily involved in the otherwise healthy regulation of normal cell growth and differentiation. Activation of an oncogene, through mutation of a proto-oncogene, promotes tumor growth. Mutations in genes that become oncogenes can be inherited or caused by environmental exposure to carcinogens. Some of the most common genes mutated in cancer are the IGF-1 receptor and its two main downstream signaling proteins: Ras and Akt.

The purinergic receptors, also known as purinoceptors, are divided into two major families: the P1, or adenosine, receptors and P2 receptors, which bind ATP and/or UTP. In the 1970s, adenosine was found to stimulate cAMP formation in brain slices. Subsequently, physiological effects of adenosine on almost all tissues have been described. These receptors have been implicated in learning and memory, locomotor and feeding behavior, and sleep. More specifically, they are involved in several cellular functions, including proliferation and migration of neural stem cells, vascular reactivity, apoptosis and cytokine secretion.

Genes that suppress cell division or growth. Tumor suppressor genes encode proteins involved in aspects of cell growth regulation such as cell cycle arrest and apoptosis. Loss of tumor suppressor gene function promotes uncontrolled cell division and growth, which are hallmarks of cancer.