The case study in cancer

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The Case Study in Cancer Rachel Candelaria BIO 111 Part I Ann is a 27-year-old nurse working at the local hospital in surgery. She had worked hard to move into the specialty, and she was enjoying her career, friends, and family. She and her partner had been living together for about a year, and she was content. As a nurse, Ann knew the importance of doing breast self-exams, and did them regularly. In the shower one morning, she felt a lump she wasn’t familiar with. Ann was a bit worried, even though there was no history of breast cancer in her family, so she made an appointment with her doctor. 1. If Ann has a tumor in her breast, is it necessarily cancerous? Differentiate between a benign tumor and cancer at the cellular level. No, if Ann has a tumor in her breast, it is not necessarily cancerous. A benign tumor refers to an abnormal growth of cells that do not invade nearby tissues and do not spread to other parts of the body. In contrast, cancer refers to the presence of malignant cells that can invade nearby tissues and spread to other parts of the body. At the cellular level, benign tumors typically consist of well-differentiated cells that resemble the normal cells of the tissue they originated from and have a more organized growth pattern. On the other hand, cancer cells are often less differentiated, have abnormal nuclei, and display uncontrolled growth and invasion capabilities (American Cancer Society, n.d.). Part II Ann’s doctor is worried enough to send her to a breast cancer specialist, just to be safe. Ann makes an appointment and is referred for a mammogram, which will image the soft tissue in the breast. After the mammogram and an exam, she meets with the surgeon, Dr. Hernandez. Dr. Hernandez is also concerned, as she felt and has images from the mammogram of a small tumor. She recommends a biopsy of the tumor as soon as possible. Ann goes in the same day for the quick surgical procedure where a needle is inserted and part of the tumor is taken for analysis. The tumor will be analyzed by a pathologist, a specialist in looking for disease in tissue samples. 1. The pathologist examines the cells taken from the tumor, particularly the number of cells in mitosis. Below are the results. In normal breast cells, one would expect 0-4 cells per 10 high-powered field of view (microscopy) undergoing mitosis. Cell Cycle Stage Number of Tumor Cells in 10 High-Power Fields Interphase 120 Prophase 7 Metaphase 2 Anaphase 10 Telophase 0

Based on the above results, what can you conclude about the tumor cells? Can you say definitively that they are cancerous? Be sure to support your answer with the data above. Based on the results provided, it can be concluded that the tumor cells are cancerous. The number of tumor cells in mitosis is significantly higher than what would be expected in normal breast cells. In normal breast cells, one would expect 0-4 cells per 10 high-powered field of view undergoing mitosis, but in this case, there are 19 cells undergoing mitosis out of 140 cells observed. This higher mitotic index indicates increased cell division and is a characteristic feature of cancer cells 2. The pathologist also looks for three receptors on the tumor cells: estrogen receptors, progesterone receptors, and HER2 receptors. a. What type of macromolecule class are cell receptors? What is the monomer? a. Cell receptors are classified as proteins and are considered a macromolecule class. The monomers of proteins are amino acids. b. What is the role of cell receptors in cellular function? Cell receptors play a crucial role in cellular function by acting as molecular switches that transmit signals from the external environment to the inside of the cell. They are involved in various cellular processes, including growth, division, differentiation, and response to external stimuli (Alberts et al., 2002). c. Ann’s tumor was positive for estrogen and progesterone receptors, but negative for the HER2 receptor. What is the role of estrogen receptors on a cell? Remember to cite your sources using APA Style. The role of estrogen receptors on a cell is to bind estrogen and mediate the cellular effects of estrogen signal transduction. When estrogen binds to its receptor, it can regulate gene expression and influence cell proliferation, differentiation, and survival (Zhao & Dahlman-Wright, 2010). Part III Dr. Hernandez sits down with Ann and her partner. The doctor is sorry to report that Ann has breast cancer; however, because it was caught early and responds to estrogen and progesterone, the prognosis is good. At this point it looks like the cancer is stage 1. However, as Ann is young, the doctor wants to perform a couple tests. The first test is a genetic sequencing test for BRCA1 and BRCA2, as well as testing for other genes known to increase the risk of cancer. The other test is an Oncotype DX test on the tumor cells. This is a gene expression test, where the results correlate with how aggressive the cancer cells are. Ann is overwhelmed, but wants to do everything she can to get rid of this disease. 1. As a result of your discussions, you know that mutations in BRCA1 and BRCA2 increase the risk of breast cancer. Because of this, a positive test for these mutations would mean different treatment for Ann, including removal of both her breasts

(bilateral mastectomy) as well as her ovaries to prevent ovarian cancer. Ann decides to have the test done, but she is a little hazy on the biology of DNA. a. Describe the basic structure and function of a gene. A gene is a segment of DNA that contains the instructions for the synthesis of a specific protein or RNA molecule. It consists of coding sequences (exons) that are transcribed and translated into functional proteins and non-coding sequences (introns and regulatory regions) that play a role in gene regulation (Alberts et al., 2002). b. At the molecular level, what is a mutation? Are all mutations harmful? What type of mutation does not lead to a change in protein structure? At the molecular level, a mutation refers to a change in the DNA sequence of a gene. Not all mutations are harmful, as some can have no effect or even produce beneficial changes. Silent mutations are mutations that do not lead to a change in the protein structure because they occur in non-coding regions or result in the same amino acid sequence due to the redundancy of the genetic code (Genetics Home Reference, 2021). c. The polymerase chain reaction (PCR) is a method that can be used to detect mutations. It uses machinery similar to your cells to replicate a specific DNA sequence, which in this case would be only the mutated gene. Describe the basic process of DNA replication in a cell. DNA replication in a cell involves several steps. It starts with the unwinding of the DNA double helix and the separation of the strands. DNA polymerase then synthesizes two new strands by adding complementary nucleotides to each separated strand. This process is semi-conservative, meaning each new DNA molecule contains one old strand and one new strand (Alberts et al., 2002). 2. Also, as a result of your discussion, you know that the expression of genes can change in cancerous cells versus noncancerous cells. The Oncotype test will look at the expression levels of several genes in her tumor cells by looking at the mRNA produced. a. What role does mRNA play in the flow of information in the cell? ( Hint : Remember the central dogma of molecular biology.) Please include the basic flow of information in the cell. a. mRNA (messenger RNA) plays a crucial role in the flow of genetic information in the cell. It carries the genetic code from DNA to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis. This process is known as transcription. The flow of information in the cell is described by the central dogma of molecular biology, which states that DNA is transcribed into mRNA, and mRNA is translated into protein (Alberts et al., 2002).

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b. Cancer cells and noncancerous cells may have almost identical DNA; however, gene expression can change. Explain the concept of differential gene expression using cancer versus noncancerous cells as an example. Differential gene expression refers to the phenomenon where different genes are expressed at different levels in different cell types or under different conditions. In the case of cancer cells versus noncancerous cells, differential gene expression can lead to the activation or inhibition of genes involved in cell proliferation, metastasis, or other cancer-related processes (Garraway & Lander, 2013). c. This Oncotype test uses microarray analysis to determine gene expression. Explain to Ann what a microarray is. A microarray is a laboratory tool used to measure the expression levels of thousands of genes simultaneously. It consists of a solid support, such as a glass slide or a silicon chip, onto which DNA or RNA molecules are immobilized. By hybridizing labeled cDNA or RNA samples to the microarray, researchers can determine the expression levels of specific genes based on the intensity of the hybridization signal (Schena et al., 1995). d. The results of Ann’s Oncotype test showed a decrease in the expression of BRCA1. How can this decrease lead to an increase in cell division? ( Hint : What is the normal role of BRCA1?) . The decrease in the expression of BRCA1 can lead to an increase in cell division because BRCA1 plays a role in DNA repair and cell cycle regulation. BRCA1 is involved in repairing DNA damage and maintaining genomic stability. When BRCA1 is defective or its expression is decreased, it can lead to errors in DNA repair and increased cell division, contributing to the development of cancer (Venkitaraman, 2014). 3. Both these tests take time and will inform Ann’s treatment plan for the best possible outcome. While she is waiting on results, Ann begins to research the main types of treatments that are available to treat breast (and many other) cancers. One of these is chemotherapy. There are many types of chemotherapy, but in general: a. How does chemotherapy work? Chemotherapy works by targeting and killing rapidly dividing cells, including cancer cells. It involves the administration of drugs that interfere with the cell's ability to divide and proliferate. These drugs can inhibit DNA replication, disrupt cell division, or induce cell death. The goal of chemotherapy is to destroy cancer cells and prevent them from spreading or growing (American Cancer Society, n.d.) b. What are some side effects of chemotherapy? Some side effects of chemotherapy include fatigue, nausea and vomiting, hair loss, changes in appetite, increased susceptibility to infections, and anemia. These side effects occur because chemotherapy drugs not only target cancer

cells but also affect normal cells that naturally divide rapidly, such as cells in the hair follicles, gastrointestinal tract, and bone marrow (American Cancer Society, n.d.). c. Based on your knowledge of chemotherapy and cell division, why do you think chemotherapy leads to these side effects? Chemotherapy leads to these side effects because it affects both cancerous and normal rapidly dividing cells. The drugs used in chemotherapy target various cellular processes involved in cell division, DNA replication, and protein synthesis. As a result, normal cells that rapidly divide, such as those in hair follicles and the gastrointestinal tract, are also affected, leading to side effects (American Cancer Society, n.d.). Part IV Dr. Hernandez calls Ann with the test results a couple weeks later. She is negative for the BRCA1 and BRCA2 mutations, which is good news. But her Oncotype score is borderline high, meaning the cancer is somewhat aggressive, and chemotherapy will decrease the chance that cancer recurs elsewhere in her body and increase her chances of survival long term. The surgeon recommends a medical oncologist to start chemotherapy, who in turn recommends a course of chemotherapy that includes paclitaxel, also known as Taxol. 1. What cell structure does Taxol target? Taxol targets microtubules, which are part of the cell's cytoskeleton. 2. What are the functions of this structure in the cell? Microtubules have multiple functions in the cell, including maintaining cell shape, cell division (formation of the mitotic spindle), intracellular transport, and movement of organelles (Alberts et al., 2002). 3. How does the targeting of this structure treat cancer? Taxol treats cancer by stabilizing microtubules, preventing their disassembly and disrupting the normal dynamics of the cytoskeleton. This interference with microtubule dynamics leads to cell cycle arrest and apoptosis (programmed cell death) in rapidly dividing cancer cells (Jordan & Wilson, 2004). Part V After four rounds of chemotherapy and a unilateral mastectomy, Ann was exhausted but relieved to be through the worst of treatment. Radiation was not necessary, and the cancerous cells had not spread to any of her lymph nodes. These were all good signs that the cancer was caught early and had not spread. Ann was back to work, and aside from some fatigue, things were slowly getting back to normal (or as normal as they ever would be again). Ann and her partner were to be married in a year. They figured if they could get through this, they could get through anything together. Ann was excited to get on with planning the rest of her life!

1. Why is it a good sign that cancerous cells had not spread to her lymph nodes? The fact that cancerous cells had not spread to her lymph nodes is a good sign because the presence of cancer cells in the lymph nodes indicates that the cancer has spread beyond the primary tumor site. Lymph nodes serve as filters for lymph fluid and are important sites for immune response. If cancer cells are present in the lymph nodes, it suggests that the cancer has the potential to spread further through the lymphatic system and potentially to distant organs (National Cancer Institute, n.d.). 2. What does metastatic mean in cancer diagnosis? Based on the above information, had Ann’s cancer metastasized? Support your answer. Metastatic in cancer diagnosis refers to the spread of cancer cells from the primary tumor site to distant organs or tissues. Based on the information provided, Ann's cancer had not metastasized because it had not spread to any lymph nodes or other distant sites. References: Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Molecular Biology of the Cell (4th ed.). Garland Science. American Cancer Society. (n.d.). Benign breast conditions: Not all lumps are cancer. Retrieved from https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast- conditions/benign-breast-conditions.html American Cancer Society. (n.d.). Chemotherapy for breast cancer. Retrieved from https://www.cancer.org/cancer/breast-cancer/treatment/chemotherapy-for-breast- cancer.html Genetics Home Reference. (2021). What are the different ways in which a genetic condition can be inherited? Retrieved from https://ghr.nlm.nih.gov/primer/inheritance/mutationsanddisorders Garraway, L. A., & Lander, E. S. (2013). Lessons from the cancer genome. Cell, 153(1), 17- 37. Jordan, M. A., & Wilson, L. (2004). Microtubules as a target for anticancer drugs. Nature Reviews Cancer, 4(4), 253-265. McCarthy, R. (2019). Pathology Student Mini-Web. Retrieved from http://pathologystudent.com/the-big-picture/cancer-picture/

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National Cancer Institute. (n.d.). Sentinel lymph node biopsy for breast cancer. Retrieved from https://www.cancer.gov/types/breast/patient/breast-treatment-pdq#_26 Schena, M., Shalon, D., Davis, R. W., & Brown, P. O. (1995). Quantitative monitoring of gene expression patterns with a complementary DNA microarray. Science, 270(5235), 467-470. Venkitaraman, A. R. (2014). Cancer susceptibility and the functions of BRCA1 and BRCA2. Cell, 108(2), 171-182. Zhao, C., & Dahlman-Wright, K. (2010). Estrogen receptor beta: An overview and update. The Journal of Steroid Biochemistry and Molecular Biology, 122(1-3), 279-285.

The case study in cancer

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