Inside "Tumor-Host Interactions":

@CancerQuest on Twitter:

Related to this page:

Test your knowledge on Tumor-Host Interactions

Was this page helpful? | What did you like most? How can we make it better?

CancerQuest > Introduction to Cancer Biology > Introduction to the Tumor-Host Interactions > Inflammatory Cells and Cancer

Inflammatory Cells and Cancer

The role of the immune system in cancer is a double-edged sword. While there is evidence that it can be beneficial (for example, immunosuppressed patients, or those with weak immune systems, have a higher incidence of cancer), in many cases the immune system clearly promotes tumor growth ⁽¹⁾ The role of immune cells in cancer is well documented. Innate immune cells (cells such as macrophages that do not produce antibodies but are capable of ingesting foreign organisms) are prominent in pre-malignant and malignant tissues, and are believed to contribute to tumor formation through the release of molecules that regulate cell growth and migration, alterations of the ECM, and angiogenesis ⁽²⁾ In addition, many cancers (gastric, cervical, colon, liver) are associated with infection and correlate with the activity of the normal host immune response. Chronic inflammatory conditions make people more likely to develop certain cancers; for example, patients with Crohn's disease have a higher incidence of colorectal cancer. A greater understanding of the ways by which the inflammatory response initiates cancer may lead to potent new cancer treatments ⁽¹⁾

In other cases the tumor itself attracts immune cells which can then impact tumor progression. Tumor cell damage and hypoxia attract macrophages from the blood into the tissue surrounding a tumor. In most cases, high tumor associated macrophage (TAM) counts are correlated with reduced survival. Many tumors secrete factors that prevent macrophages from alerting other immune cells to the presence of cancer cells, resulting in an inability of the immune system to recognize the tumor. Macrophages themselves secrete factors that enhance tumor cell proliferation, invasion, and promote angiogenesis. In addition, TAMs release oxygen free radicals and other mutagenic compounds that may create mutations in surrounding cells. The ability of TAMs to stick to tumor cells allows macrophages to carry tumor cells into the circulation and thus aid in the spread of the cancer (metastasis) ^{(3) (4) (2)}

References for this page:

1. Kopfstein, L., and G. Christofori. 2006. Metastasis: cell-autonomous mechanisms versus contributions by the tumor microenvironment. Cell Mol Life Sci. 63:449-68. [PUBMED]
2. Tlsty, T.D., and L.M. Coussens. 2006. Tumor stroma and regulation of cancer development. Annu Rev Pathol. 1:119-50. [PUBMED]
3. Condeelis, J., and J.W. Pollard. 2006. Macrophages: obligate partners for tumor cell migration, invasion, and metastasis. Cell. 124:263-6. [PUBMED]
4. Laconi, E. 2007. The evolving concept of tumor microenvironments. Bioessays. 29:738-44. [PUBMED]