Monday April 26,1999
Announcements:

Lecture notes:

1. Profound abnormalities in the plasma membrane.
   
   a. increased permeability

b. increased transport

c. missing, altered, or new membrane proteins.

d. diminished capacity for adhesion and recognition at the level of the plasma membrane.

2. Profound changes in the cytoplasm
   
   a. cytoskeleton becomes disorganized
   
   b. changes in enzyme activity
   
   c. increased reliance on glycolysis
3. Abnormal growth and division patterns
   
   a. Inhibitions on overcrowding are missing.
   
   b. Cells don't stop dividing (the average cell can divide about 50 times then it dies)
   
   c. Cells don't differentiate into the recognizable tissues of that organ.
   
   d. Cells often don't perform the functions of that cell type.
   
   e. Most "solid tumors" can vascularize themselves by secreting a growth factor to cause nearby blood vessels to branch into the tumor.
4. Cancer cells can move!
   
   a. Because they don't adhere well, they can break away and travel in blood and lymph.
   
   b. Some can move like macrophages through tissue.
   
   c. Some secrete "collagenase"

There are 6 known ways that cekks can be transformed into cancer cells.

1. Chemical carcinogens
2. Radiation
3. Oncogenes (onco - means cancer)
4. Absence of a tumor supressor gene
5. Lack of DNA repair enzymes
6. Altered apoptosis genes (controlled cell death)

Some cancers need a two step process

1. Initiation (a change in DNA)
2. Promotion (uncontrolled growth and metastasis of cells)

• Killer T-cells can recognize some cancer cells - sometimes.
• Some tumors cells have unique antigens for which we can make antibody.
• Fully understanding the immune system will help some day in using it to prevent or treat cancers.

Oncogenes: are a family of genes that are carried by some animal viruses that have the potential to transform cells.

• Over 50 have been identified so far.
• They are all (so far) mutated forms of normal genes. (The normal gene is called the proto-oncogene)
• They are all (so far) growth or regulatory genes.

They have variable activity (ability to transform cells):
a.src transforms almost all cells.
b. SV⁴⁰ transforms 1 in 10,000.

Proto-oncogenes can be changed into oncogenes by radiation or chemical carcinogens.

Oncogenes can transform cells by "expressing" its products too much or inappropriately

Known: Epstein-Barr virus can cause Burkitt's Lymphoma (a cancer of the jaw in children in Africa - something else is
involved,too)

HTLV-1 causes a rare leukemia

"Suspected": Hepatitis B - liver cnacer

Papilloma virus - penile and cervical cancers

Herpes Simplex virus - cervical cancer