How Cancer Outsmarts the Immune System

A cancer cell is a metabolic anomaly. Unlike normal cells, which generate energy efficiently via aerobic respiration, most cancer cells prefer aerobic glycolysis—a pathway known as the Warburg effect. Although far less efficient at extracting energy from glucose, this process enables cancer to thrive by devouring glucose at a vastly higher rate. To compensate for their inefficiency, cancer cells ramp up the expression of GLUT1 glucose transporters. This adaptation enables cancer cells to siphon an enormous amount of glucose from the bloodstream, feeding their insatiable growth.

PET Scans: Technology Harnessing Cancer’s Glucose Hunger
The very characteristic that makes cancer so ravenous—its hunger for glucose—can be used for detection. Positron emission tomography (PET) scans exploit this feature. When patients are injected with radioactively labeled glucose, cancer cells eagerly absorb it. PET imaging then reveals “hot spots” where glucose uptake is highest, pinpointing zones of suspected cancer activity. This powerful, noninvasive technology has revolutionized oncological diagnostics.

The Immune System: Constant Vigilance
Our body’s immune system is a formidable barrier against developing cancer. Specialized cells, like natural killer cells, patrol the bloodstream, targeting bacteria, viruses, and any suspicious cells—including potential cancers. People with weakened immune systems, such as those with HIV or on immunosuppressive drugs, face a higher risk of cancer because this surveillance is compromised. Despite the immune system’s constant patrol, some cancer cells develop stealthy tactics to evade detection and destruction, especially as tumors grow and shield themselves within tissues.

Carcinogens: Origins of Cellular Mutation
Substances or exposures that cause cancer are known as carcinogens. The International Agency for Research on Cancer (IARC) classifies these into several groups:

Group 1: Carcinogenic to humans (e.g., arsenic, aflatoxin, ionizing radiation)
Group 2A: Probably carcinogenic
Group 2B: Possibly carcinogenic
Group 3: Not classifiable
Group 4: Probably not carcinogenic

Both synthetic chemicals and natural substances (such as mold toxins and wood dust) make this list. Even certain medications, like the chemotherapy drug cyclophosphamide, carry risks.

Radiation and Viral Carcinogenesis

Ionizing radiation damages DNA by breaking molecular bonds, leading to unstable, mutation-prone chromosomes. Exposure increases cancer risk in a linear dose-dependent fashion.
Non-ionizing radiation is generally less risky and usually dissipated without causing permanent damage.
Viruses like hepatitis B and C can lead to chronic infections, raising the risk of liver cancer worldwide. Helicobacter pylori, a bacterium persisting in the human stomach for millennia, is also linked to certain cancers.

Genetic Mutations: The Molecular Roots of Cancer
At the heart of cancer lies genetic chaos. Mutations affect two main gene types:

Oncogenes: Like an accelerator stuck to the floor, mutations can force endless cell growth.
Tumor suppressor genes: These function as cellular brakes. If they fail or are mutated, uncontrolled growth can occur.

Most cancers result from a collection of random mutations, each contributing to the rogue cell’s arsenal—immortality, endless division, and metabolic superpowers. Rarely, a single catastrophic mutation (as with the “Philadelphia chromosome” in certain leukemias) is enough to spark cancer.

The Somatic Mutation Theory
The currently dominant theory, known as the somatic mutation theory, clarifies how normal somatic cells (those not involved in reproduction) can—through accumulated genetic injuries—become cancerous. If DNA damage outpaces repair, and if critical genes controlling growth mutate, a cell can be set on the path to cancer. Most common cancers require the combination of multiple gene mutations—a genetic “perfect storm” rather than a single event.

Immunity and Memory
A healthy immune system not only fights cancer but also creates antibodies against infections. After exposure to diseases like measles, the immune system retains a memory. Should the infection return, it launches a rapid, specific response—often making reinfections rare.

Cancer is a story of paradoxes and patterns—a microcosm of life, chance, and survival. The more we unravel these mysteries, the more effective our defenses against one of humanity’s oldest and most complex adversaries become.

Source : The Cancer Code: A Revolutionary New Understanding of a Medical Mystery by Jason Fung

Goodreads : https://www.goodreads.com/book/show/52163526-the-cancer-code

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