Question

Identify and briefly describe the three stages of tumor development. Include a description of the types of factors that contribute to each stage.

Answer 1

Answer:

Three stages of tumour development (Carcinogenesis) are: 1) Initiation, 2)Promotion, 3)Progression

1) Initiation: It involves the alteration, change, or mutation of genes arising spontaneously or induced by exposure to a carcinogenic agent. Genetic alterations will result in dysregulation of biochemical signaling pathways associated with cellular proliferation, survival and differentiation. Examples of carcinogenic agents are:- Radiation, Chemical carcinogens, UV light etc.

2) Promotion: It involves a relatively long and reversible stage, in which actively proliferating preneoplastic cells accumulate. Here, selective growth enhancement induced in the initiated cell and its progeny by continous exposure to a promoting agent. Examples of promoting agents are:- Phorbol esters, TPA, Estrogen, Excessive fat etc.

3) Progression: It is the final stage of neoplastic transformation, in which there is genetic, phenotypic changes and cell proliferation. There is a fast increase in tumor size, and cells may undergo further mutations with invasive and metastatic potential. Themain factor resposible for this stage is: Mutations.

(One more stage, Metastasis is the spread of cancer cells from the primary site to other parts of the body. It usually spread through the blood or the lymph system.)