The Cell Cycle and Cancer

Some thoughts about cell division… Do all cells divide at the same speed? What factors affect mitosis? How do cells die? All cells do not divide at the same speed. The rate of cell division depends on many things such as signalling from the brain, hormones, genes being turned on and off. Skin cells and hair cells divide based on how fast they are worn out. If a cut happens, signalling molecules will tell them to start dividing faster as part of the repair process. Liver cells can spend up to a year in interphase before going through division and brain cells exist for a lifetime in a non-dividing state. What other factors impact mitosis? Altitude, antibiotics, Chemotherapy, Radiation, Sunlight Cells do not live forever. They can only divide a certain number of times until they receive a message or instructions to die. Cell division is necessary for cells to be replaced after they die. 3 million cells die every minute. We undergo cell division as part of regeneration, a process essential for repairing damaged tissue.

How do Cells Die? Necrosis Apoptosis Premature cell death due to unexpected and accidental cell damage. This is an unregulated cell death. Causes: toxins, radiation, trauma, lack of oxygen due to the blockage of blood flow. A cell also dies as a normal part of the functioning of healthy multicellular organisms. This is a regulated or controlled cell death of cells that are no longer useful. Removes cells that have lost their ability to perform efficiently. The material of the cell is recycled by the body.

What happens when damage to a cell impairs its ability to commit apoptosis and it starts to divides uncontrollably? Answer: Cancer

Cancer Uncontrolled cell division Caused by changes in the DNA instructions controlling cell division Loss of a cell’s ability to undergo apoptosis (becomes “immortal”) On/off switch is broken Continually reproducing Can lead to formation of a lump or tumour. A tumour is a mass of cells that continue to divide without any benefit to the body.

Normal Cells vs Cancer Cells In small groups (5-7 minutes) Compare Normal Cells to Cancer Cells Come up with similarities and differences Record on whiteboards

Normal Cells Cancer Cells Make exact copies of themselves through mitosis Certain appearance. Variability in appearance. Reproduce for certain number of controlled cell divisions (on-off switch functional) Uncontrolled cell division (on-off switch NOT functional). Normal cells respond to signals from nearby cells (cell communication). Do not interact with other cells or respond to signals. Behave independently. Stick together to form masses of cells as appropriate. Do not stick to other cells. Can spread to other parts of the body. Self-destruct when too old or too damaged (apoptosis) Grows into tumours. Cell death can be via forced medical technologies (eg. Chemotherapy, radiation, etc)

Cell Cycle Checkpoints Checkpoints are where the cell assesses if conditions are favorable for cell division. When the environment is not favorable (eg. Lack of nutrients, damage to cell’s DNA), a protein called p53 can stop the cell cycle and cause the cell to die. When the proteins that regulate the cell cycle are mutated or absent, cells can divide uncontrollably, leading to cancer.

Tumours Tumours need nutrients and O2 to survive and to go through the cell cycle. Therefore, they need access to the body’s blood supply. Send out chemical signals to normal cells in surrounding area and these normal cells encourage the blood vessels to expand into the tumour mass.

Types of Tumours Benign Tumours Malignant Tumours Harmless masses of cells Localized to a specific area – does not interfere with surrounding cells Cancerous masses of cells Interferes with the work of surrounding cells or destroys those cells. These cells can break away and spread to other parts of the body and start a new tumour (metastasis)

Causes of Cancer Mutagens Carcinogens Random changes that can occur when DNA is replicated; can be genetically inherited Any environmental factor that can cause a mutation Tobacco products X-ray exposure UV radiation from sun or tanning beds Viruses (eg. HPV) Certain toxic chemicals (eg. BPA or PVC in plastics) Poor lifestyle choices (eg. Poor diets can reduce amount of cancer-fighting antioxidants in your body)

Cancer Video: TED.com “How do cancer cells behave differently from healthy ones?” (George Zaidan) https://www.youtube.com/watch?v=BmFEoCFDi-w

Cancer Screening Screening is an early detection tool that improves chances of treatment and survival rates in most cases. Can be done by yourself, your family doctor or a specialist. Examples: Breast self-exams PAP smears (to check for signs of cervical cancer) Testicular exams Blood tests for increased PSA (prostate-specific antigen) levels for prostate cancer.

Cancer Diagnosis Signs of cancer can include increased fatigue, unexplained weight loss, swelling/pain in the tumour area or can go undetected. Examples of technologies: Endoscopy (insertion of a viewing instrument into body) X-ray Ultrasound (using sound waves to detect tumours) CT/CAT scan and MRI Sample removal/biopsies for microscopic examination

Cancer Treatment Options Chemotherapy Radiation therapy Surgery Biophotonics Clinical drug trials Holistic Whiteboard information: What is it? How does it work? (Brief) 2 pro’s 2 con’s 1-1.5 minute presentation