Inflammation and carcinogenesis – lecture 8 foundation week
Learning objective: how does inflammation contribute to carcinogenesis? How do infectious agents
(H pylori) promote cancer?
How does inflammation in cancer present?
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Inflammatory cells and mediators (chemokines, cytokines, prostaglandins) are found in
tissues.
Tissue remodelling is seen in chronic inflammatory responses.
Angiogenesis is like that seen in tissue repair.
Inflammatory cells are present in the microenvironment.
What are the hallmarks of cancer?
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Deregulating cellular energetics
Resisting cell death
Genome instability and mutation
Inducing angiogenesis
Activating invasion and metastasis
Tumour promoting inflammation
Enabling replicative immortality
Avoiding immune destruction
Evading growth suppressors
Sustaining proliferative signalling
How does inflammation lead to cancer?
1. Small tumour
 A few cells can survive with simple diffusion of o2 and nutrients
 But as demand grows, the cancer cells struggle to survive without enough oxygen
 So more genetic faults build up
 Cancer cells then release chemical signals that lead immune cells to invade the
tumour
2. Cytokines released from tumour triggers angiogenesis
 The tumour can now receive enough o2 and nutrients
 Cytokines allow for the growth of a “stroma” – which is where the tumour can
“nestle”
3. The inflammatory cells that were recruited now hit the tumour with free radicals, but this
further damages the cell’s DNA
4. Inflammation can also cause metastasis – stimulates enzyme production that help tumour
cells eat through the molecules which anchor them to their surroundings
When can inflammation play a role in IBD-associated cancer?
When can inflammation play a role in sporadic colon cancer?
In sporadic cancer there are more inflammatory chemicals like:
 Pro-inflammatory cytokines: il-6 and tnf-alpha
 Increased intestinal expression of cyclooxygenase 2 (COX2). COX 2 makes prostaglandins
from arachidonic acid
Which infectious agents are considered carcinogenic?
 Stomach: helicobacter pylori
 Liver: hep b, c, Opisthorchis viverrini, Clonorchis sinensis
 Cervix/uteri: HPV, HIV
 Anogenital: HPV, HIV
 Nasopharynx: EBV
 Oropharynx: HPV
 Kaposi’s sarcoma: herpes virus type 8
 Non-hodgkins lymphoma: H pylori, EBC, HCV
 Hodgkins lymphoma: EBV
 Bladder: schistosoma haematobium
Which bacteria are involved in cancer?
Salmonella typhi: gallbladder cancer
Helicobacter pylori: gastric cancer
Streptococcus gallolyticus: colon cancer
What proportion of people infected with H. pylori develop gastric cancer?
<2%
What are the “virulence factors” of H pylori? Molecules produced by infectious agents that allow
them to succeed
How does cancer usually develop in the stomach?
Normal gastric epithelium -> superficial gastritis ->
atrophic gastritis
Atrophic gastritis is a process of chronic
inflammation of the gastric mucosa of the stomach,
leading to a loss of gastric glandular cells and their
eventual replacement by intestinal
and fibrous tissues
In superficial gastritis: Acute gastritis
with superficial erosions. Mucosal
erythema and edema consistent with
acute gastritis. No correlation exists between microscopic inflammation (histologic
gastritis) and the presence of gastric symptoms (eg, abdominal pain, nausea, vomiting
Atrophic gastritis -> intestinal metaplasia -> dysplasia -> gastric adenocarcinoma