Cancer and Embryology

Cancer is one of the most feared maladies among people in the United States, and it is almost definite that if someone lives long enough, cancer will inevitably set in. Changes in the DNA of somatic cells are the primary cause of cancer as a disease. Cancer cells originate as normal, healthy, and uniquely specialized cells from a tissue but through the influence of a carcinogenic agent or DNA mutation during aging begin to divide at a greater than normal rate. Continuous division leads to the formation of tumors (large masses of cells) which can be either benign or malignant. Benign tumors are not cancerous and are characterized by their resemblance to nearby cells, and localization to a specific organ tissue (in situ). The paper “Epithelial-Mesenchymal Transitions: Twist in Development and Metastasis” focuses on malignant (cancerous) tumors and some of their characteristics. Malignant tumors do not resemble their parent tissues at all and are unspecialized and often irregularly structured cells. Due to the fact that they express the gene for telomerase permanently, most do not have a controlled life span, but are immortal. Destructive and somewhat unavoidable, cancer has strong implications for the organism that it affects due to its genetic qualities.

The genetic implications of cancerous growth have parallels to growth of embryonic cells. Tumor suppressor genes are found in the genomes of individuals, and act as brakes on cell division when it begins to occur abnormally. Oncogenes have the capability to stimulate cell division, but are usually turned off in differentiated non-dividing cells. Mutation of both of these genes through repeated cell division or carcinogenic influences leads to development of cancer afflicted tissues. The growth process of cancer begins with the loss of tumor suppressor genes and the activation of oncogenes. Through further mutation a carcinoma develops when anti-metastasis gene action is lost. Eventually the cancer will spread through the lymphatic and circulatory systems to other organs of the body and begin to grow there. Embryonic-type cells are produced when each of these genetic changes occurs: they rapidly divide by mitosis and lack specialty.

Development is a process that an organism undergoes that characterizes each of the continuous life stages. The earliest stages of development of a plant or animal are considered embryonic. In sexual reproduction of eukaryotic organisms, when two gamete cells fuse, a diploid zygote is formed. Soon after fusion the fertilized egg cell begins to divide by the process of mitosis (a complex cell cycle that involves the division of the genome as well as the cytoplasm’s contents to form two identical daughter cells), doubling the number of cells present with each separation. Rapid proliferation of non-specific cells continues during the initial stages of embryogenesis through the blastula stage where specialization begins in the cells. The development of an organism begins with growth due to cell division and progresses from there with cell differentiation. It is the expression of specific genes, turned on by cytoplasmic determinants and signals released by neighboring cells that causes differentiation to occur in the rapidly dividing cells. From this point on an organism is no longer undergoing embryogenesis, as it has identifiable parts that perform specific functions. Never again in its life course will the individual ever naturally undergo unspecialized cell division.

Tissue development in both pre-natal growth and in the stem cells of the adult body is an accurate depiction of how cancerous tumors can develop and spread. Cancerous developments are corrupt forms of their natural counterparts and much of the gene regulation involved in cell differentiation is also found in cancerous growths. Both the initiation and maturation of cancerous growths follow the trends of undifferentiated cells in their invasion, spreading through the circulation, and metastasis in other areas of the body. Rapid cell division is common to both the embryogenesis of an organism and the growth of a cancerous tumor. Cells possess all of an organism’s particular genome, yet do not express any specific function while profusely multiplying. In no other stage of a cell’s life cycle does it display these tendencies. Cancer and its cellular properties do not show similarities with normal tissue cells but have more characteristics of a newly formed embryo in its primary growth stages.