Cancer Biology

Introduction
In any multicellular organisms, the individual cells form a society that co-operates to ensure the health and survival of the organism. Within this organized society, certain fundamental processes such as cell birth, division, proliferation, differentiation and migration are carefully controlled and there is a balance between cell birth and cell death, so that any net cell gain or loss is appropriate.

Loss of adherence to the society’s rules can lead to uncontrolled proliferation, loss of the ability to die, or other abnormal proliferation resulting in a normal cell taking on a malignant phenotype.

1 . Normal Cell Division

In any multicellular organism, the cells may die for a number of reasons, making cellular proliferation an essential process to ensure the health of the individual. Reproduction of somatic cells occurs by mitosis (nuclear division) and cytokinesis (cytoplasmic division). The alternation between interphase and mitosis is referred to as the cell cycle.

During interphase, which is the longest phase, the chromatin shortens and thickens. In prophase, the first phase of mitosis, the chromosomes appear as two identical sister chromatids, and spindle fibres form and radiate from the centrioles at either pole of the cell. In metaphase, the spindle fibres pull the centromeres of the chromosomes which become aligned to the middle of the spindle, the equatorial plate. During anaphase, the centromeres split and the chromatids are pulled apart by contraction of the spindle fibres. In telophase, the final stage, a nuclear membrane is formed around each group of chromosomes and the cytoplasm divides to produce two identical diploid cell.  [...]