Embryogenesis and oncogenesis (generation of cancer) share a number of features including cell proliferation, apoptosis, cell migration and invasion, formation of new blood vessels, and differential gene activity. Embryonic cells are relatively undifferentiated, and cancer cells appear to be undifferentiated or dedifferentiated. Homeotic gene expression directs early development, and mutant expression leads to loss of the differentiated state or an alternative cell identity. M. T. Lewis [(2000). Breast Can. Res. 2:158–169] suggested that breast cancer may be caused by the altered expression of homeotic genes. When he examined 11 such genes in cancers, 8 were underexpressed while 3 were overexpressed compared with controls. Given what you know about homeotic genes, could they be involved in oncogenesis?

Key Concepts

Homeotic Genes

Homeotic genes are crucial regulatory genes that control the body plan and the identity of body segments during embryonic development. They determine the formation of specific structures in the correct locations. Mutations or altered expression of these genes can lead to developmental abnormalities and have been implicated in oncogenesis, as they may disrupt normal cell differentiation and promote cancerous growth.

Cell Differentiation

Cell differentiation is the process by which unspecialized cells, such as embryonic stem cells, develop into specialized cells with distinct functions. In normal development, this process is tightly regulated, ensuring that cells acquire the appropriate identity and function. In cancer, however, cells may become dedifferentiated, losing their specialized characteristics, which can contribute to uncontrolled proliferation and tumor formation.

Gene Expression Regulation

Gene expression regulation involves the mechanisms that control the timing and level of gene activity in cells. This regulation is essential for normal development and cellular function, as it ensures that genes are expressed in the right cells at the right times. In cancer, dysregulation of gene expression can lead to the overexpression or underexpression of critical genes, including homeotic genes, which may drive the transformation of normal cells into cancerous ones.