Cancer Cytogenetics PDF

CYTOGENETICS CSU MLS 2ND YEAR PROF. KEITH TAGUINOD | S.Y 2024-2025 UNIT 9: CANCER CYTOGENETICS system....

CYTOGENETICS CSU MLS 2ND YEAR PROF. KEITH TAGUINOD | S.Y 2024-2025 UNIT 9: CANCER CYTOGENETICS system. cancer is fundamentally a genetic disease caused TOPIC OVERVIEW by mutations and alterations in the DNA that 9.1 Genetic Nature of Cancer affects normal cellular processes. Genetic changes 9.2 Genes and Cancer can occur in 2 major categories of genes: 9.3 Chromosomal Abnormalities in Cancer - Oncogene - mutated version of 9.4 Genetic Testing proto-oncogenes. When Proto-oncogenes 9.5 Diagnosis and Prognosis mutate , they turn into oncogene wherein their 9.6 Genetic Counseling functions are compromised; instead of 9.7 Gene Therapy regulating cell division and controlling cell 9.8 Cytogenetic Test Used in Cancer proliferation, uncontrolled cell growth and division occur. - Tumor Suppressor Genes - normal tumor 9.1 GENETIC NATURE OF CANCER suppressor genes prevent unregulated cell division. When normal tumor suppressor Cancer is a complex disease that results from the genes mutate, their functions are basic process of uncontrolled growth. compromised. Cell proliferation results in a mass that invades neighboring tissues and may metastasize to more Tumors different sites. Cancer is fundamentally a disease of the genome. A tumor is formed by the clonal expansion of a Mutations in genes that regulate cell growth, tumor precursor cell that has incurred genetic differentiation, and apoptosis can lead to uncontrolled cell proliferation and tumor damage. development. tumor is a mass or lump of tissues that may cancer is a genetic disease caused by changes in the DNA of the cell that lead to uncontrolled cell resemble swelling as the cells divide and grow growth. These changes can either be inherited or excessively. acquired during a person’s lifetime the hallmarks of cancer include the ability of cells usually, tumors are identified if its benign, to proliferate without control, evade apoptosis, invade surrounding tissues, and metastasize. malignant, or precancerous, by conducting Genetic changes such as mutations and biopsy. chromosomal abnormalities play a significant role in driving these processes. - a sample is aspirated through biopsy. In that - cells grow and divide uncontrollably as cell aspirated sample, the behavior of the cell division is not being regulated - cells evade apoptosis as they can avoid sample is observed and identified. programmed cell death, and since they are able to avoid cell death, they tend to survive longer than normal cells Types of Tumors - cancer cells or malignant tumors have the ability to infiltrate surrounding tissues as their shapes are irregular and they are not enclosed Benign Tumors - non-cancerous and non-life within a capsule. - cancer cells metastasize; they can spread threatening tumors. They are localized, throughout different parts of the body regular in shape, and they are enclosed within through the bloodstream and lymphatic a protein capsule. TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS - protein capsule acts as a barrier to prevent - these changes can occur spontaneously or be tumor cells from infiltrating other cells induced by external factors. Precancerous Tumors- are not cancerous, Germline mutations are responsible for 5% to but have the potential to become cancerous. 10% of cancer cases. It is important that these precancerous Sporadic cancer or somatic mutation are tumors are detected early, to have better caused by tobacco, over-exposure to UV management and won’t progress into cancer. radiation, and other toxins and chemicals Malignant Tumors - are cancerous tumors. not all mutations lead to cancer, examples They can metastasize, invade surroundings include single mutations; tissues, evade apoptosis, and grow single mutations are yet to cause cancer and uncontrollably. not enough to cause cancer, but there will be an increased risk of further changes in genetic composition because these single mutated cells will still undergo multiple divisions until it forms accumulation of mutated cells. - the accumulated mutations will cause abnormal patterns in the genes. Through these abnormal patterns, it will progress into cancer. - single mutations can be triggered by genetic Cancer arises from the accumulation of susceptibility and/or environmental factors genetic aberrations in somatic cells. (carcinogens, chemicals, UV radiation) - the interplay between the mutations in specific genes, genetic makeup of an individual, and environmental factors determine whether mutation will lead to Green - normal cells cancer. Purple - cells that acquired genetic mutation - when mutation occurs, the genetic makeup will modulate how the patient will be able to Mutation acquire cancer, while the environmental factors will increase the risk of developing The basic mechanism in all cancer is cancer. mutation. Mutation is a permanent alteration or change in DNA sequence. Historical Milestone in Cancer Cytogenetics the earliest systematic study of cell division in malignant tumors was made in the 1890s by TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS German pathologist David Von Hansemann. He 9.2 GENES AND CANCER suggested that the frequent occurrence of aberrant mitosis in carcinoma biopsy could be used as criterion for diagnosing the malignant state. Key Genes in Cancer - during his time, scientists’ interest was focused on researching about cancer; that’s are specific genes that paly critical role in the why it took a century before his theory was development, progression, and treatment of cancer followed up a century later, the investigation of Hansemann was forged into systematic somatic theory of Proto - Oncogenes cancer. This theory was presented by Theodore Boveri. He was able to suggest or hypothesize that Proteins encoded may function as growth chromosome abnormalities where the cellular factors or their receptors, signal transducers, changes occur will cause the transition from normal to malignant proliferation. transcription factors or cell cycle components. - during this time, he was not able to prove his these are normal genes that help in regulating theory because of technological difficulties. in the 1950s, development on cytogenetic cell division, and control cell proliferation techniques emerged (karyotyping and they are critical for normal cellular function chromosome staining). Leading to the discovery of chromosomal abnormalities. Through these such as cell cycle regulation and developments, a decade later, breakthroughs on differentiation cytogenetic also emerged; Discovery of chromosomal abnormalities in the when these genes are mutated and 1960s (Philadelphia chromosome) abnormally activated, they turn into Identification of structural abnormalities (1970s-1980s, e.g., Burkitt's lymphoma, APL) oncogenes which could lead to uncontrollable - regarded as pivotal decade because during growth and proliferation of cells which this decade, several chromosomal abnormalities were identified which were contributes to cancer development associated with different types of cancers examples of proto-oncogenes: Development of molecular cytogenetics (FISH, CGH, aCGH, etc.) ○ MYC gene - in its normal state, it - due to these developments, more precise understanding of chromosomal abnormalities promotes cell proliferation and associated to cancer were formulated; growth. It regulates cell cycle and cell - mechanisms and mutations were further observed, as molecular cytogenetic progression, and initiates apoptosis. techniques provide high-resolution tools to - When this gene undergoes mutation detect genetic changes. - the advancements of molecular cytogenetic or transformed into oncogene, its techniques paved the way for precision normal function will be compromised. medicine - with precision medicine, targeted - Once it turned into oncogene, there therapy arises. Targeted therapy is will be overexpression of MYC gene the medication used for cancer, it is only focused on attacking cancer resulting to uncontrollable growth cells. which could progress into cancer. - MYC oncogene is associated with Burkitts Lymphoma due to the TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS translocation between chromosomes 8 and 14. Tumor Suppressor Gene ○ BCR-ABL gene - usually when The product of tumor suppressor genes BCR-ABL genes are separated into normally block abnormal growth and two different genes, their normal malignant transformation and lead to function is to control cell growth and malignancy when the function of both alleles cell proliferation. is lost. - When there is a fusion that occurs Tumor suppressor genes are a family of between the two genes, and a hybrid normal genes that instruct cells to produce protein is produced, their function will proteins that restrain cell growth and division. be disrupted. Instead of controlling Since tumor suppressor genes code for cell growth and cell proliferation, the proteins that slow down cell growth and fusion gene promotes continuous cell division, the loss of such proteins allows a cell growth and proliferation, and to grow and divide in an uncontrolled fashion. inhibition of apoptosis. tumor suppressor genes acts as a break for Types of Proto-oncogenes: cell division and growth; it ensures that cells 1) Cellular Oncogenes (c-oncogenes) would divide uncontrollably 2) Normal Oncogenes (n-oncogenes) they also act as cell cycle checkpoint - when tumor suppressor genes detect damage or error during cell division, they would initiate apoptosis in the events where tumor suppressor genes have mutated or deleted, cells could grow uncontrollably and could evade apoptosis which could lead to tumor formation and progress into cancer examples of tumor suppressor genes: ○ TP53 (Tumor Protein 53) - often referred as the guardian of the genome; - it regulates the cell cycle, maintains genomic stability, and plays a key role in inducing apoptosis when DNA is damaged. TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS - mutation in TP53 are common in the Tumor Suppressor Genes Involved wide range of cancers including lung, in Human Neoplasm colon, and breast cancers - mutation or deletion of TP53 compromises its function; the loss of its function will allow damaged cells to continue to divide and grow uncontrollably because damaged cells bypass critical safety checks. That is why instead of undergoing cell death, it evades apoptosis and it continues to grow and proliferate, which eventually DNA Repair Genes lead to tumor formation progressing into cancer These are genes that fix any mistakes made ○ RB1 gene (Retinoblastoma 1 gene) when DNA is replicated. Mistakes that aren’t - encodes the retinoblastoma protein fixed become mutations, which may - retinoblastoma protein is involved in eventually lead to cancer. cell cycle regulations as it controls they have different repair pathways or cell growth and proliferation; mechanisms; each pathway or mechanism - also, it checks the cell from the handles specific DNA damage to ensure that transition of G1 phase into S phase of cells can continue dividing without the cell cycle introducing harmful mutations - mutations in RB1 gene are strongly when these repair systems are defective or associated with retinoblastoma which when genes are mutated, the likelihood of is a rare childhood cancer of the cancer development arises, since DNA retina. RB1 genes could also be damage persists and accumulates mutation associated with other cancers such as over time osteosarcoma Genetics disorders in which DNA repair - when there is a mutation in RB1 gene, process is defective exhibit risk for certain its function is compromised; the loss type of cancers: of RB1 gene function leads to - Xeroderma pigmentosum/pigmentosa uncontrolled cell growth and cell - Ataxia telangiectasia cycle progression which allows cell to - Bloom syndrome proliferate without renovation - Fanconi's anemia DNA repair genes are essential in maintaining genomic stability of DNA by correcting errors TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS that occured during DNA replication and from 9.3 CHROMOSOMAL ABNORMALITIES IN environmental damage CANCER Chromosomal abnormalities play a crucial role Different Pathways/Mechanisms of in the pathogenesis of cancer, influencing DNA Repair Genes tumor initiation, progression, and response to Mismatched Repair (MMR) treatment - fix replication errors such as nucleotide base mismatches Chromosome Defect - defective MMR gene is associated with Lynch Structural Abnormalities - there are Syndrome which is an inherited disorder that alterations in the chromosomal architecture increases the risk of colorectal and affecting the regulation and expression of endometrial cancer genes. Nucleotide Excision Repair (NER) ○ Translocation - they repair bulky lesions in the DNA - ex: Philadelphia Chromosome (BCR-ABL fusion gene) - bulky lesions can be caused by - translocation results in fusion genes ultraviolet radiation creating hybrid proteins with abnormal functions. - mutations in NER will cause Xeroderma - NOTE ! check in 9.2 under pigmentosum/pigmentosa proto-oncogenes ○ Inversion - a condition wherein individuals have - ex: Inversion of chromosome 16 (CBFB - MYH11 extreme sensitivity to sunlight and are fusion gene) - the fusion of these two genes disrupts at high risk for skin cancer normal blood cell development, Homologous Recombination Repair (HRR) leading to acute myeloid leukemia. ○ Insertion - responsible for the repair of the double strand - ex: insertion of segments in ALK gene braids of the DNA by making use of a - once there is a insertion in ALK gene, it will be associated to lung cancer template; - the insertion of a segment in a gene - to accurately repair the double strands of the would affect its normal function which could lead to uncontrolled cell DNA and to prevent mutations during repair, proliferation which could result to HRR will pattern the DNA to its sister cancer ○ Duplication chromatid - result in the presence of extra copies of - mutations in HRR will lead to genomic chromosomal segment, leading to over expression of oncogenes which could drive instability, and can result in increaded risk of uncontrolled growth of cancer cells breast, ovarian, and other typed of cancer ○ Amplification ○ Deletion - example of HRR include ERCE1 and ERCE2 genes Numerical Abnormalities - cells have abnormal number of chromosomes compared to the typical diploid number TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS Aneuploidy - can be classified into: BCR-ABL, which drives uncontrolled cell - Trisomy - Loss or gain of whole chromosome growth. - Monosomy - Loss or gain of whole chromosome set Numerical abnormalities, specifically Solid Tumors aneuploidies are associated with cancer; these are composed of dense mass of cells which Aneuploidy alters the number of are often surrounded by a supporting tissue chromosome, which causes gene dosage Types of Solid Tumors: ○ Carcinoma - arises from epithelial cells effect. - overall expression of genes is affected which ○ Sarcoma - arises from connective tissues ○ Central Nervous System Tumors lead to genomic instability ○ Germ Cell tumors - occurs in ovaries and Aneuploidy is more closely associated with testicles Wilms Tumor adverse outcomes, and it is more aggressive than structural abnormalities due to its role in This childhood kidney cancer is often genomic instability associated with deletions in the WT1 tumor suppressor gene on chromosome 11. NOTE ! review chromosomal abnormalities Wilms Tumor 1 Suppressor Gene (WT1) regulates the gene expression during kidney and gonadal development. It also controls cell Specific Chromosomal Aberrations in Cancer Types growth and differentiation. mutation and disregulatiom of WT1 causes Leukemias and Lymphomas uncontrolled cell growth which leads to tumor development and progression of cancer these are hematological malignancies Acute Myeloid Leukemia (AML) MYC Amplification Various chromosomal abnormalities are Amplification of the MYC oncogene is associated with AML, including t(15;17), observed in various cancers, including breast t(8;21), and inv(16). cancer and lymphoma. most lymphomas occur due to translocation Burkitt Lymphoma between two chromosomes leading to This aggressive lymphoma is often associated overexpression of genes with the t(8;14) translocation. P53 gene (TP53) : Guardian of Genome Philadelphia Chromosome (t(9:22)) Located in 17p13,1 and most common target A translocation found in chronic myeloid for genetic alteration in human cancer. A little leukemia (CML), leading to the fusion gene TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS over 50% of human tumors contain mutations RB Gene in this gene. Located in 13q14 position Homozygous loss (deletion or mutation) of RB protein inactivates E2F(transcription p53 occurs in virtually every type of cancer, factor) & thereby inhibits cell cycle at G1 including carcinoma of lung, colon and breast. phase. Li-Fraumeni Syndrome - Usually cyclin D rises in late G1 phase & later - a rare condition due to the mutation of tp53 inactivates RB to maintain the usual process gene of cell kinetics. - this syndrome has a significantly increased - Associated neoplasm: osteosarcoma, risk of developing various cancers including carcinoma of breast, colon, and lung cancer lung, colon, and breast cancer RB gene and RB1 gene is quite different from TP53 is one of the most important tumor each other. suppressor genes as it helps in preventing - RB gene - generic term used to describe the cancer by maintaining genomic stability. overall role of retinoblastoma TP53 also protects the cell by cell cycle - RB1 gene - is a tumor suppressor gene under arrest, DNA repair, and by triggering RB gene. apoptosis. when RB gene is mutated, its function will be the loss of TP53 function contributes to disrupted which will result to uncontrolled cell tumoregenesis which allows damaged cells to growth which will lead to the progression of proliferate uncontrollably. cancer - tumoregenesis - normal cells transform into cancer cells Examples of Rare Familial Cancer Syndromes Ewing’s Sarcoma (t(11;22)) a cancer affecting bone and soft tissue, which is characterized by a translocation between chromosomes 11 and 22. this translation results in the fusion EWS gene - chromosome 22; FLI1 gene - chromosome 11 the resulting fusion protein is an aberrant transcription factor that promotes tumor 9.4 GENETIC TESTING growth Sample Collection 1. Hematologic Malignancies - Bone Marrow TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 9 : CANCER CYTOGENETICS - PBS Replacing a faulty gene with a healthy copy 2. Solid Tumors Inactivating a disease-causing gene 3. Other Tissues Introducing a new or modified gene - Lymph Nodes - Spleen 9.8 CYTOGENETIC TEST USED IN CANCER - Other Tissues 1. Karyotyping Sample Transport and Storage 2. Fluorescence In-Situ Hybridization (FISH) Processed immediately 3. Chromosomal Microarray Analysis (CMA) Preservative solution, such as RPMI-1640 medium Samples should be transported to the laboratory in a timely manner, ideally at room temperature or on ice. For long-term storage, samples can be frozen. Cell Culture : To increase the number of dividing cells in the sample, making chromosome analysis easier. Chromosome Preparation : Mitotic arrest: cells are treated with a chemical Staining and Banding Analysis: Karyotyping: FISH, CGH 9.5 DIAGNOSIS AND PROGNOSIS Diagnosis Identification of Specific Cancer Types Determining disease stage Prognosis Predicting Treatment Response Estimating Risk of Recurrence 9.6 GENETIC COUNSELING Process 1. Gathering Family History 2. Assessing Genetic Risk 3. Explaining Genetic Testing 4. Supporting Decision-Making 5. Providing Emotional Support 9.7 GENE THERAPY TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A