Once a tumor is initiated, however, complex interactions
between cancer cells and their surrounding environment—
known as the tumor microenvironment—can contribute
to disease progression.
The tumor microenvironment is a specialized niche
Single base changes
surrounding the cancer cells (see sidebar on Cancer
Growth: Local and Global Influences, p. 23). Bidirectional
communication between cancer cells and the tumor
microenvironment affect cell multiplication, tumor
heterogeneity, and tumor metastasis ( 27, 28). Furthermore,
the tumor microenvironment can shelter cancer cells from
the effects of radiation, chemotherapy, and immunotherapy
thereby rendering them resistant to treatment ( 29). Future
studies are likely to identify additional cellular and molecular
mechanisms by which the tumor microenvironment
interacts with cancer cells and may help us develop new
and improved therapeutics.
• Some mutations can lead to the generation of altered versions of normal proteins,
and these may cause cancer to develop.
• Deletion or insertion of a single base can result in new proteins or loss of protein function,
which can lead to cancer.
Extra copies of genes (gene amplification)
Higher quantities of certain proteins can result in enhanced cell survival
and growth, leading to cancer.
Loss of DNA can result in loss of genes necessary to stop or control the growth of cancer.
Exchange of DNA across different parts of the genome can lead to entirely
new proteins that can drive the development of cancer.
Mutations that alter the epigenome
Several proteins read, write, or erase the epigenetic marks on DNA or the
histones around which it is packaged. Mutations in the genes that produce
these proteins can lead to cancer.
Below are some of the types of genetic mutation known to lead to cancer.
Of note, genetic mutations do not always result in cancer.
Adapted from ( 1)