Module 2

Neoplasm

New growth

Neoplasia - altered cell differentiation and growth

Normal tissue renewal and repair requires:

Proliferation, Differentiation, Apoptosis

Proliferation

A process of cell division

An adaptive process for new cell growth to replace old cells or when additional cells are needed

Differentiation

Process by which cells become more specialized with each mitotic division

Apoptosis

Eliminates senescent (old), damaged, or unwanted cells through a process of controlled cell death

Proto-oncogenes

Encode proteins that signal for the cell to proliferate through a tightly regulated process

Tumor suppressor genes

Encode proteins that inhibit cell growth and signal (when necessary) for apoptosis

Cell cycle

Process by which a cell duplicates its genetic information and divides between two genetically identical daughter cells

4 phases: G1 (gap 1), S phase, G2 (gap 2), M phase

G1 (gap 1)

DNA synthesis stops while the cell enlarges and both RNA and protein synthesis begins

S phase

DNA synthesis occurs, producing two separate sets of chromosomes, one for each daughter cell

G2 (gap 2)

DNA synthesis again stops while RNA/protein synthesis continues

1st 3 phases - interphase

Checkpoints

Located at the end of the 1st 3 phases

Means of molecular surveillance used to ensure the cell is ready to proceed to the next phase

If not, the cycle is halted and allowed to complete its replication or even repair any DNA damage (when detected), thereby ensuring all the genetic information is passed on correctly

M phase

Consists of mitosis (dividing up the DNA) and cytoplasmic division

Continually dividing cells or resting state (G0)

G0 - occurs when nutrients or growth factors are unavailable or when highly specialized cells first leave the cell cycle (neurons may permanently stay there)

Cell proliferation

Process of increasing cell numbers by mitotic cell division

• Gametes (ovum and sperm), haploid so only 1 set of chromosomes from 1 parent (after fusion, diploid cell containing both sets of chromosomes)

• Somatic (non-reproductive)

Cell differentiation

Process by which cells become more specialized in both their structure and function

When specialized cells are unable to divide, rely on progenitor/parent cells of the same lineage that are still about to divide

Stem cells

Remain incompletely differentiated and dormant until they are needed (unlike progenitor cells)

When needed, they begin to divide, producing not only other stem cells, but also cells capable of carrying out functions of the needed differentiated cell

When a stem cell divides, 1 daughter cell retains the stem cell characteristics, while the other daughter cell becomes a progenitor cell until it reaches a state of terminal differentiation

2 Important properties of stem cells

Self-renewal, Potency

Self-renewal

Means the stem cell can undergo numerous mitotic divisions while maintaining an undifferentiated state

Potency

Describes the differentiation potential of stem cells

Pluripotent stem cells - (master cells) can potentially differentiate into any cell type

Multipotent stem cells - can differentiate into only a few select types

Unipotent stem cells - restricted to a single cell type but can maintain self-renewal

The 2 types of stem cells are classified as

Embryonic stem cells - major role in developing embryo, give rise to 3 main germ layers (endoderm, mesoderm, ectoderm) which in turn develop into all the organ systems of the body

Adult stem cells - significant roles in homeostasis, contributing to tissue regeneration and replacement of cells lost to apoptosis