What Are Some of the Differences between Normal Cells and Cancer Cells - Lab Report Example

Cell Reproduction Lab Introduction Visual analysis of cells stained to observe mitosis, through either an optical or a fluorescent microscope, is a key procedure in cytopathology. Examining the surgically removed pathological, e.g., suspected cancer, tissue specimen with a microscope, and manually counting the number of cells exhibiting mitosis, that is the total number of cells in prophase, metaphase, anaphase and telophase gives the mitotic rate (MR). Interphase is not a stage of mitosis, although it is a phase of the cell cycle. Chromosomes are visible during prophase, metaphase and anaphase and are indistinct during interphase and telophase (Ackerley, 2007). Comparing the MR value the test specimen with a normal tissue sample can indicate the presence of malignancy. The higher the mitotic count, the more are the chances of the tumor having metastasized. When a high number of cells are dividing, it is likely that they will invade the blood or lymphatic vessels and thus spread around the body. Analysis questions Based on your data and observations, what are some of the differences between normal cells and cancer cells? Normal stomach cells divide more rapidly than either lung cells or ovarian cells as seen from the percentage of cells dividing. However, this might not be reflected in the cancerous cells of the same tissue. This is evident from the fact that the cancerous ovarian cells are dividing the fastest, that is, the ovarian cells have the highest mitotic rate in this case. In all the different tissue samples analyzed, the mitotic index (MI) of the normal cells are lower compared to the mitotic index of the corresponding cancerous tissue. For example, MI obtained for normal lung cell is 0.05 while that of the cancerous lung cell is 0.15. Similarly, MI of normal stomach cell is 0.2 while for cancerous stomach cell, it is 0.35. MI values of normal and cancerous ovarian cells are 0.05 and 0.45, respectively. Based on the MI values, the various cancers in the tissues analyzed could be graded as: Ovary > Stomach > Lung. Which type of cancer shows the most aggressive growth? Explain. Small-cell cancer, also called the oat cell carcinoma, is the most aggressive type of cancer. It is called as oat cell due to the flat cell shape and scanty cytoplasm. Oat cell carcinoma can occur in various locations, with the lung being the most common. The extrapulmonary locations of small cell cancers include the esophagus, stomach, pancreas, larynx, hypopharynx, salivary glands, nasal cavity and paranasal sinuses, thymus, small and large bowel, uterine cervix, endometrium, breast, prostate, urinary bladder, and skin (Ibrahim et al., 1984). Oat cell carcinoma spreads very rapidly throughout the body via the blood and lymphatic (node) systems. [http://www.fccc.edu/cancer/types/lung/small-cell.html]. Similar to normal cells, cancer cells require a blood supply in order to function. Malignant cells detach from the tumor, access the bloodstream and enter the general blood circulation through which they have access to every organ of the body. Similarly, they can also access all parts of the body through the lymphatic system which has its own channels throughout the body. According to the results of this study, lung cells have the lowest MI value among the different tissues examined. Also, the difference in MI between normal and cancerous lung is the least among the various tissues analyzed. This indicates that the cancerous lung cells in this case are not the aggressive, small cell type of cancer. When studying cell division in tissue samples, scientists often calculate a mitotic index, which is the ratio of dividing cells to the total number of cells in the sample. Scientists often calculate the mitotic index to compare the growth rates of different types of tissue. Which type of tissue would have a higher mitotic index, normal tissue or cancerous tissue? Explain. Cancer tissue will have a higher mitotic index compared to normal tissue. The reason is the very high rates of cell division exhibited by cancer cells. They grow unhindered and are not subject to the normal regulatory mechanisms of cell division such as dividing only when appropriate external signals such as protein (e.g., insulin-like growth factor) or steroid (e.g., estrogen) are present; or contact inhibition; or the presence of genetic damage. Generally, most normal human cells are not actively dividing, but are in the resting or Go phase, carrying out their normal functions. A higher mitotic index, that is, comparatively more number of cells actively dividing in relation to those “resting” would, therefore, indicate a higher rate active division. How can cancer cells be recognized? Cancer cells can be recognized by the higher mitotic index in comparison to a normal cell from a similar tissue. For this, the mitotic cell needs to be identified. Chromosomes are not visible in non-dividing cells, even with the aid of histological stain for DNA and electron microscopy. Chromosomes will become visible only when the condensation of the chromosome begins to occur, that is, at the prophase and later stages of cell division. The use of stains that bind to the chromosomes and visual analysis using an optical microscope enable mitotic cells to be studied. Conventional staining techniques are used to obtain consistently stained chromosomes. The commonly recommended stains are the Romanovsky dyes such as Giemsa or Leishmans stain because, with these stains, destaining of the slides can be easily done (Gustashaw, 1991). Generally 20 cells are analyzed which is enough to produce statistically significant data. Lab Results Number of cells in each phase of the cell cycle Interphase Prophase Metaphase Anaphase Telophase % of cells dividing % of cells at rest Normal lungs 19 1 0 0 0 5 95 Cancerous lungs 17 1 1 0 1 15 85 Normal stomach 16 1 1 0 2 20 80 Cancerous stomach 13 2 2 2 1 35 65 Normal ovary 19 0 0 1 0 5 95 Cancerous ovary 11 2 2 3 2 45 55 References Ackerley, S.K., 2007. Mitosis. Accessed on 18 May 2010 from http://www.uoguelph.ca/zoology/devobio/210labs/mitosis1.html Gustashaw, KM., 1991. Chromosome Stains. In The ACT Cytogenetics Laboratory Manual, Second Edition, edited by M. J. Barch. The Association of Cytogenetic Technologists, Raven Press, Ltd., New York. Accessed on 18 May 2010 from http://homepage.mac.com/wildlifeweb/cyto/index.html Ibrahim NB, Briggs JC, Corbishley CM., 1984. Extrapulmonary oat cell carcinoma. Cancer, 1984, 54(8):1645-61. http://www.fccc.edu/cancer/types/lung/small-cell.html Accessed on 18 May 2010. Read More