On what principle is the nomenclature of cancers based? Explain and give example
ID: 268464 • Letter: O
Question
On what principle is the nomenclature of cancers based? Explain and give examples. Explain coupling of cell differentiation and cell division in normal and cancer cells. Explain what deficiency makes cancer cell growh anchorage-independent. What are th consequences? Explain how cancer cells become immortalized Explain the role of cell cycle check points in cancer. Explain how cancer cells can cause angiogenesis and the consequences of it. Explain the stages of metastasizing. What is the role of the immune system in cancer development? Explain. What can cause cancer? Explain What are carcinogens and precarcinogens? Explairn Explain he experiment that proves the existence of tumor suppressor genes What are caretaker genes and how can mutations in them cause cancer? What are gatekeeper genes and how can mutations in them lead to cancer? What are the main differences between benign and malignant tumors? Explain what are cancer treatment strategies based on, give 3 examples.Explanation / Answer
1. Human body is composed of two types of tissues: Parenchymal tissue and Mesenchymal tissue. Parenchymal tissue is nothing but epithelial tissue. Mesenchymal tissue is connective tissue, muscles and blood vessels of the body. Malignant tumors of the parenchymal tissues are known as carcinoma whereas tumors of mesenchymal origin are known as sarcoma.
eg.,
Smooth muscle tumor is known as Leiomyosarcoma.
2. Coordination of cell cycle arrest and differentiation is achieved by transcription factors in normal cells.
Example, transcription factor Prospero, a protein in Drosophila is responsible for controlling the cell-cycle arrest and inducing differentiation at the same time. Hence acts as an coupling agent between cell-cycle arrest and differentiation. Such a transcription factors coupling cell-cycle arrest and differentiation are found in mammalians.
Example., Neural basic helix-loop-helix (bHLH) transcription factors.
Such a temporal coupling is essential for normal growth and maintaining homeostasis.
However, in case of cancer progression such coupling of events is disrupted. For example, CDK inhibitory proteins (CKIs) are responsible for cell-cycle arrest and are highly expressed in differentiating cells. These CKIs bind to cyclin dependent kinases (CDKs) and inhibit their activities related to cell-cycle. In many cancer cells, p16INK4A , a CKIs is mutated and under expressed.
3. Cells normally attach to extracellular matrix (ECM) or other cells or tissue culture plates (in vitro) and it is necessary for their survival. This type of adherence is known as anchorage dependence. However, mesenchymal cells are not anchorage dependent and hence they can survive in suspension. In order for primary tumor cells to migrate from its original place they need to detach from other cells or ECM. In doing so, these cells possess a transition known as epithelial to mesenchymal transition in which cells transit from epithelial to mesenchymal behavior. Hence once the transition happens, they need not possess anchoragge dependency. Hence can migrate to other location, a phenomenon known as metastasis and turn to a stage known as cancer.
4. Telomeres are the repetitive DNA- protein complex present at the ends of the chromosomes. These telomeres shorten at each successive division and induces chromosomal instability. This leads to death of a normal cells.
In case of tumors, this telomere length is preserved by enzyme called telomerase. This happens due to genetic mutation in telomerase gene which leads to its reactivation and hence preservation of telomere length in cancer cells.
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