The Cell Cycle and Cancer
I. Purpose
I will compare and contrast the similarities and differences between normal cell tissue and cancer cell tissue by identifying the various stages of the cell cycle and determining the percentage of cells dividing and cells at rest through a virtual lab. I will observe the differences in the cell cycle for a normal lung, a cancerous lung, a normal stomach, a cancerous stomach, a normal ovary and a cancerous ovary.
II. Background
Cancer may develop when the cell cycle is not being regulated. The cell divides uncontrollably which may be very dangerous for a person's health. Uncontrolled cell division can be caused by a mutation that does not allow the proteins that regulate the cell cycle to work properly. A mutation of tumor suppressor genes usually makes tumor suppressor proteins that destroy cancerous cells. Cancer cells can continue to multiply and form a tumor if the tumor suppressors do not perform their function. Some characteristics that cancerous cells have are that they do not die, they divide uncontrollably even when they touch other cells, and they do not function like a healthy cell would. The statistics in 2007 shown by the American Cancer Society and National Cancer Society reveal that 160,390 people died from lung cancer, 15,280 from ovarian cancer and 11,210 people died from stomach cancer. Cancer is caused by both environmental and genetic factors. Some of the risk factors for lung cancer are: smoking cigarettes, secondhand smoking, and exposure to certain organic chemicals and radiation. Stomach cancer is more common after the age of thirty-five and men are at a higher risk than women. Eating foods that have been preserved by salting, pickling, or drying is another risk factor. It is more likely for women to develop ovarian cancer when they have never had children, when they have had breast cancer and as they get older.
III. Hypothesis
I believe that during the cell cycle, the percentage of cells dividing will be greater for cancerous cells than for healthy cells because cancer cells divide uncontrollably since they are not being regulated. If I am correct, I will see the percentage of cells dividing be greater for various cancerous cells than for healthy cells as measures by percentage of cells observed in interphase or in mitosis.
IV. Materials
- Cancerous Ovary Tissue Sample on Slide with Cover Slip
- Normal Ovary Tissue Sample on Slide with Cover Slip
- Cancerous Lung Tissue Sample on Slide with Cover Slip
- Normal Lung Tissue Sample on Slide with Cover Slip
- Cancerous Stomach Tissue Sample on Slide with Cover Slip
- Normal Stomach Tissue Sample on Slide with Cover Slip
- Microscope
V. Procedure
- Watch the video about the cell cycle and learn about cancer.
- Click on the microscope to begin learning about the phases of mitosis.
- Click and drag the label for the corresponding cells of the cell cycle under the microscope.
- Open the Data Table and begin to record the number of cells in each phase of mitosis in the tissue sample.
- Determine the percentage of cells dividing and the percentage of cells at rest.
- After counting all the cells in a particular sample, record the information for the rest of the tissue slides (normal and cancerous lung, stomach, and ovary)
VI. Data
The data table below lists the number of cells per area present in various phases of the cell cycle observed in three different types of tissue in both normal and cancerous cells.
Below is a graph of the data I collected
VII. Journal Questions
- Some of the differences between normal and cancerous cells are that cancer cells have a lack of contact inhibition which leads to uncontrollable dividing. Normal cells stop dividing once they contact other cells. Another difference is that cancer cells do not die, they continue dividing and they are not being regulated which is very dangerous. As I observed, cancer cells divide more than healthy cells.
- The tissue that would have a higher mitotic index is the cancerous tissue because the cancer tissue can be found with more cells in mitosis than any normal tissue. The cancerous tissues have less cells at rest than the normal tissues because cancer cells have a mutation which keeps them from being regulated in the cell cycle, causing them to divide at a higher rate.
- I would expect for skin to have the highest mitotic index because the body has to continuously replace dead skin cells. The other body tissues do not need for their cells to be replaced that often.
VIII. Conclusion
In this experiment, I hypothesized that the percentage of cells dividing would be greater for cancerous cells than for normal cells because cancer cells are not regulated which causes their mitotic index to increase. The information I gathered showed that the percentage of cells dividing for cancerous lung, stomach, and ovary tissues ranged from 10%-40% more than the normal tissues. This experiment could be improved by adding more cancer tissues to test, and therefore, have more available data to obtain more detailed and accurate results. A commonality that I observed was that the percentage of cells going through the cell cycle for a normal and cancerous stomach only increased 10% meanwhile for a normal and cancerous ovary, it increased 40% for the tissue with cancer. These results show that a cancer cell divides at a higher rate probably because the gene mutations do not allow the proteins that regulate the cell cycle to perform their function properly. Since cancerous cells divide uncontrollably, the cancerous tissue may keep growing and expand to other areas of the body.