Core Framework & Diagram How Does Inflammation Promote Cancer?
July 7, 20261 Min Read Chronic Inflammation and Cancer
July 8, 2026Inflammation is life's fire — but burning too long, it can cook normal cells into cancer cells
—— Why Rudolf Virchow saw the inflammation-cancer connection 170 years ago — and we're only now truly understanding what he meant.
I. Virchow's foresight: a correct intuition 170 years ago
In 1863, Rudolf Virchow — father of modern pathology, first to propose 'cellular pathology' — observed something that gave him pause when examining cancer tissue sections: inside cancer tissue, not only large numbers of proliferating cancer cells, but dense white blood cell infiltration. White blood cells are the immune system's soldiers — why would they gather in large numbers inside cancer tissue? Virchow proposed two possible explanations: either white blood cells were combating cancer (immune surveillance), or chronic inflammation itself caused the cancer. He leaned toward the latter — he noticed that high-incidence sites for cancer were often also common sites for chronic inflammation (lung cancer and chronic bronchitis, gastric cancer and gastric ulcers, liver cancer and chronic hepatitis).
Virchow's intuition was almost completely ignored for the following century. Twentieth-century cancer research focused on gene mutations (carcinogens, radiation) and cell-autonomous biological changes, not microenvironments and inflammation. Not until the late twentieth and early twenty-first century, with explosive development of molecular immunology, did Virchow's hypothesis begin receiving molecular-level confirmation, gradually evolving into today's formal recognition of 'inflammation as the seventh hallmark of cancer' (Hanahan & Weinberg's 2011 Cell classic review).
2. Mechanism one: ROS's 'random bombardment'
In chronic inflammation, activated neutrophils and macrophages produce large amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS) through 'oxidative burst' — originally to kill pathogens. But in chronic inflammatory environments, these highly reactive molecules continuously bombard host cell DNA — like throwing bombs indiscriminately into a crowded market. ROS's classic DNA damage product is 8-hydroxydeoxyguanosine (8-OHdG) — if not timely corrected by DNA repair systems, causes G→T transversions in the next replication round (a common carcinogenic mutation type). Research finds 8-OHdG levels in chronic inflammation patient tissue are three to ten times those of normal tissue; hepatitis B patients' hepatocyte 8-OHdG levels positively correlate with liver cancer incidence.
NF-κB is the 'master switch' connecting inflammation and cancer: in chronic inflammation, NF-κB is persistently activated, simultaneously activating pro-proliferative genes (Cyclin D1), anti-apoptotic genes (BCL-2, BCL-xL), pro-angiogenic genes (VEGF, IL-8), and more inflammatory cytokines (TNF-α, IL-6) — a self-amplifying positive feedback loop transforming inflammation's 'firefighting tools' into 'cancer-promoting engines.' Inflammatory factors (like TNF-α) also directly downregulate expression of some key DNA repair genes, further reducing repair efficiency — more damage, less repair, and mutation accumulation rate rises exponentially.
3. COX-2 and PGE2: inflammation makes cells 'unwilling to die'
Cell apoptosis (programmed death) is one cancer's natural barriers — when a cell's DNA is damaged beyond repair, tumor suppressor proteins like p53 command the cell to enter apoptosis, self-destructing to prevent cells with too many mutations from surviving and dividing. Chronic inflammation disrupts this safety valve. Cyclooxygenase-2 (COX-2) is massively upregulated in inflammation, converting arachidonic acid to prostaglandin E2 (PGE2). PGE2 through G-protein coupled receptors activates the PI3K/AKT signaling pathway, directly suppressing pro-apoptotic protein (like BAD) function while upregulating BCL-2 and other anti-apoptotic proteins — essentially telling damaged cells 'don't die,' letting them continue living, continue dividing, continue accumulating more mutations.
COX-2 is highly expressed in multiple cancers related to chronic inflammation: approximately eighty percent of colorectal cancers, approximately fifty percent of breast cancers, approximately sixty percent of non-small cell lung cancers. This is precisely why non-steroidal anti-inflammatory drugs (NSAIDs), especially COX-2 selective inhibitors (like celecoxib), show colorectal cancer risk reduction effects in epidemiological studies — not directly 'killing' cancer cells, but turning off the inflammation signal that makes cells 'unwilling to die.' The evidence for NSAID prevention of colorectal cancer is strongest (including RCT evidence in Lynch syndrome patients), but long-term cardiovascular and gastrointestinal side effects mean it hasn't become routine general population recommendation.
4. IL-6 and STAT3: inflammation-cancer axis's 'signal highway'
Interleukin-6 (IL-6) is one of the largest-produced cytokines in chronic inflammation, and the single most important signaling molecule connecting inflammation and cancer. IL-6 acts through the JAK/STAT3 signaling pathway; activated STAT3 enters the cell nucleus, simultaneously starting a large group of target genes: promoting cell proliferation (Cyclin D1, MYC); suppressing apoptosis (BCL-2, BCL-xL); promoting invasion and metastasis (MMP-9, VEGF); immune evasion (PD-L1); and stem cell maintenance (Oct4, Sox2).
The IL-6/STAT3 axis is persistently activated in multiple cancers and is an independent poor prognostic factor: in liver cancer, gastric cancer, colorectal cancer, and multiple myeloma, the STAT3 phosphorylation level in tumor tissue correlates negatively with tumor stage, metastasis risk, and overall survival. Chronic inflammation, obesity, and advanced age are all common causes of persistently high IL-6 — understanding this, controlling body weight and reducing chronic inflammation sources aren't only 'improving metabolic health,' but directly lowering IL-6/STAT3 axis persistent activation and molecularly reducing inflammation-related cancer risk.
5. Obesity: the largest-scale 'chronic inflammation-cancer' epidemiological evidence
Obesity (BMI > 30) is one of the strongest single modifiable risk factors for cancer beyond smoking. WHO data shows approximately four to six percent of global cancers are directly attributable to obesity. The association has been confirmed in thirteen cancer types: colorectal, breast (post-menopausal), endometrial, esophageal adenocarcinoma, kidney, liver, gallbladder, pancreatic, thyroid, ovarian, multiple myeloma, meningioma, and gastric cardia cancer.
Obesity's cancer-promoting mechanisms work primarily through three mutually reinforcing pathways: chronic low-grade inflammation — adipose tissue (especially visceral fat) is an active immune organ; hypertrophied fat cells release large amounts of adipokines (leptin pro-inflammatory, adiponectin reduced), and directly recruit macrophages to infiltrate adipose tissue, forming 'crown-like structures,' continuously secreting TNF-α, IL-6, IL-1β, causing systemic chronic low-grade inflammation; insulin/IGF-1 axis activation — obese individuals often have insulin resistance, causing persistently elevated insulin and IGF-1 levels, activating PI3K/AKT and MAPK pro-proliferative pathways; and abnormal estrogen secretion — aromatase in adipose tissue converts androgens to estrogen, with obese individuals (especially post-menopausal women) having elevated serum estrogen, the most important mechanism for elevated breast and endometrial cancer risk.
6. Managing chronic inflammation: the most powerful controllable cancer prevention strategy
Understanding chronic inflammation's cancer-promoting mechanisms directly points to an evidence-supported cancer primary prevention strategy set. Maintaining healthy body weight is the most important single intervention: reducing visceral fat, lowering TNF-α, IL-6, insulin/IGF-1, and estrogen levels, while simultaneously improving NK cell and CTL function — four benefits in one, covering all major pathways of inflammation-promoted cancer.
Regular exercise, not only a means to lose weight, itself has direct anti-inflammatory effects: myokines secreted by muscles after exercise (like IL-15) directly promote NK cell and CTL activation, suppress M2 macrophage polarization, and lower systemic inflammatory markers (hsCRP, IL-6, TNF-α). Treating known chronic inflammation sources is a precision intervention strategy: eradicating H. pylori (Taiwan Matsu region 15-year follow-up data: gastric cancer incidence decreased over fifty percent); standardized treatment of chronic hepatitis B and C (significantly reducing liver cancer risk); effectively controlling inflammatory bowel disease (reducing colorectal cancer risk).
Not smoking: tobacco is not only a direct carcinogen but also a 'chronic inflammation engine' that systematically activates NF-κB pathways and persistently elevates lung and systemic inflammatory markers. For high colorectal cancer risk populations (Lynch syndrome, familial adenomatous polyposis), using aspirin or celecoxib as chemoprevention under physician guidance is a strongly evidence-supported option.
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