David Sadava David M Hillis H Craig Heller

David Sadava, David M. Hillis, H. Craig Heller, May R. Berenbaum La nuova biologia. blu Anatomia e fisiologia dei viventi S

Cancer Biology

What is cancer? Cancer is a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues. Cancerous tumors are malignant, which means they can spread into, or invade, nearby tissues. Unlike malignant tumors, benign tumors do not spread into nearby tissues. 4

What is cancer? Carcinomas are formed by epithelial cells. Sarcomas are cancers that form in bones and soft tissues (muscle, fat, blood vessels, lymph vessels, fibrous tissue). Leukemias are the cancers that begin in the blood-forming tissues of the bone marrow. There also different types of brain and spinal cord tumors that are named based on the type of cell in which they formed. 5

What is cancer? Biological characteristics of cancer cells: • Grow under control • Ignore growth signals • Ignore stop signals • Become invasive • Able to evade the immune system • Less specialized than normal cells • Have unstable DNA 6

Cancer depends on mutations Cancer cells have more genetic changes (DNA mutations) than normal cells. Some mutations are in somatic cells (sporadic cancers) or in the germinal line of cells (hereditary cancers). 7

Gene control and cancer Oncogenes are genes that can potentially cause cancer. Tumor suppressor genes are also involved in controlling cell growth and division because they can protect a cell from one step of the path to cancer. DNA repair genes are involved in fixing damaged DNA. 8

What causes cancer? • Environmental factors— mutagens. Chemical compounds, tobacco smoke, ultraviolet rays • Hereditary factors • Causal factors— duplication DNA mistakes 9

What causes cancer? The human body has a lot of control systems to protect against inflammation. Some inflammation can last several days, but if the inflammation is caused by cancer cells, it persists and changes from acute to chronic inflammation. Many chronic inflammatory diseases can increase a person’s cancer risk. 10

What causes cancer? Genetic testing looks for specific inherited changes in a person’s chromosomes, genes or proteins. The test also determines whether family members have inherited the same mutation as a family member who is known to carry a cancer-associated mutation. For example, specific inherited mutations in BRCA 1 and BRCA 2 genes increase the risk of female breast and ovarian cancers. 11

Can viruses cause cancer? Viruses are able to cause cancer. They have oncogenes in their viral genome. A virus must enter a living cell and hijack its DNA in the host cell. RNA viruses transcribe the double strand DNA with the reverse transcriptase from a single strand RNA template. 12

How can we prevent cancer? Many things in our genes, lifestyle and environment may increase our risk of getting cancer. A healthy lifestyle could help prevent cancer, including: • no smoking • doing sport • reduce the use of alcohol • eat more fruits and vegetables • avoid HPV or hepatitis • protect skin from sun 13

How do we diagnose cancer? Diagnosis determines the type and size of a cancer and find out if it has spread. After diagnosis, it is possible to suggest treatments. 14

How is cancer treated? The main treatments include: • Surgery— open surgery or minimally invasive surgery makes it possible to remove a tumor in part or in whole • Radiation therapy— external and internal beams of iodine and cobalt serve to destroy the DNA in humoral cells • Chemotherapy— it works by stopping or slowing the growth of cancer cells 15

How is cancer treated? • Hormone therapy— some hormones stimulate cell growth; this therapy interferes with the receptors of these hormones. Tamoxifen is used for treating breast cancer. • Targeted therapy— aims at the changes in cancer cells. The Imatinib is used against a particular type of leukemia. • Immunotherapy— helps the immune system fight cancer • Stem cell transplant— is a procedure that restores blood-forming stem cells 16

How is cancer treated? Each therapy and drug must be tested prior to use. In vitro tests are made of single cells in the laboratory, outside living organisms. After a long time the drugs can be promoted to in vivo tests, using a whole, living organism. All these procedures are called preclinical development, a stage of research that begins before clinical trials (testing in humans). 17

What happens if a cancer returns after treatment? Cancer stem cells are cancer cells that can regenerate very fast. Such cells are hypothesized to persist in tumors as a distinct population and cause relapse and metastasis by giving rise to new tumors. A theory proposed to explain the metastatic preference of cancer cells for specific organs is called the “seed and soil” theory: interaction between the cells (seed) and the tissues (soil) determines the formation of a secondary tumor. 18

What happens if a cancer returns after treatment? Precision medicine is an emerging medical model and approach to disease treatment and prevention that takes into account individual variability in genes, environment, and lifestyle for each person. In this model, diagnostic testing is often used to select appropriate therapies based on a patient’s genetic content and other molecular and cellular analyses. 19