Tumor microenvironment

Overview of the tumor microenvironment

Tumor Microenvironment

The tumor microenvironment (TME) is the environment surrounding a tumor within the body, consisting of various cell types, signaling molecules, and the extracellular matrix (ECM). The TME plays a crucial role in tumorigenesis, influencing tumor growth, progression, and response to therapy.

Components of the tumor microenvironment

Components

The TME is composed of a variety of cellular and non-cellular components:

• Cancer cells: The primary component of the tumor, these cells proliferate uncontrollably and can invade surrounding tissues.
• Stromal cells: These include fibroblasts, endothelial cells, and pericytes, which contribute to the structural framework of the tumor.
• Immune cells: The TME contains various immune cells such as macrophages, T cells, and natural killer cells, which can either attack the tumor or be co-opted to support tumor growth.
• Extracellular matrix (ECM): A complex network of proteins and polysaccharides that provides structural support and influences cell behavior.

Stromal cell in tumor microenvironment

Tumor Stroma

The tumor stroma is the supportive tissue around the tumor, consisting of the ECM and stromal cells. It plays a significant role in tumor progression by providing structural support and modulating the behavior of cancer cells.

Tumor stroma and extracellular matrix in hypoxia

Hypoxia

Hypoxia, or low oxygen levels, is a common feature of the TME. It results from the rapid growth of tumors outpacing their blood supply. Hypoxia can lead to the activation of hypoxia-inducible factors (HIFs), which regulate the expression of genes involved in angiogenesis, metabolism, and cell survival.

HIF regulates interactions of cancer cells with ECM

Immune Evasion

Tumors can evade the immune system through various mechanisms, including the expression of immune checkpoint molecules that inhibit T cell activation. The TME can also recruit regulatory T cells and myeloid-derived suppressor cells to suppress immune responses.

Immune checkpoints in breast cancer

Angiogenesis

Angiogenesis, the formation of new blood vessels, is critical for tumor growth and metastasis. The TME promotes angiogenesis through the secretion of growth factors such as vascular endothelial growth factor (VEGF).

Metastasis

The TME facilitates metastasis by providing pathways for cancer cells to invade surrounding tissues and enter the bloodstream or lymphatic system. The ECM and stromal cells can be remodeled to support this process.

Tumor-associated immune cells in the tumor microenvironment (TME) of breast cancer models

Related Pages

• Cancer
• Metastasis
• Angiogenesis
• Hypoxia-inducible factor
• Immune checkpoint