Cell Cycle & Cancer Development I PDF

BIOL 2006SEF CELLS IN HEALTH AND DISEASE TOPIC 3: CELL CYCLE AND CANCER DEVELOPMENT I Heidi Wong [email protected] Outline  Overview of Cancer  Causes and risk factors of cancer  Hallmarks of cancer  Laboratory Diagnosis of Cancer 2  Major Cause o...

BIOL 2006SEF CELLS IN HEALTH AND DISEASE TOPIC 3: CELL CYCLE AND CANCER DEVELOPMENT I Heidi Wong [email protected] Outline  Overview of Cancer  Causes and risk factors of cancer  Hallmarks of cancer  Laboratory Diagnosis of Cancer 2  Major Cause of Death in Hong Kong Centre for Health Protection, Department of Health https://www.chp.gov.hk/en/statistics/data/10/27/117.html# 3 Key Facts of Human Cancer There are > 200 types of cancers Account for ~ 20-30% of all deaths in well developed countries About 1 out of 3 people will be treated for cancer Since there are many different types of cancers, there will be no one “cure” or treatment Human life expectance increases, the incidence of cancer will continue to rise 10 million people die from cancer every year At least one third of common cancers are preventable Cancer is the second-leading cause of death worldwide 70% of cancer deaths occur in low-to-middle income countries Millions of lives could be saved each year by implementing resource, appropriate strategies for prevention, early detection and treatment 4 What is cancer? Cancer is a disease which occurs when changes in a group of normal cells within the body lead to uncontrolled, abnormal growth forming a lump called a tumor; this is true of all cancers except leukaemia (cancer of the blood). If left untreated, tumors can grow and spread into the surrounding normal tissue, or to other parts of the body via the bloodstream and lymphatic systems, and can affect the digestive, nervous and circulatory systems or release hormones that may affect body function. 5 What is Tumor (Neoplasm) 腫瘤? Neoplasia literally means “new growth.” Neoplasm: A disorder of cell growth that is triggered by a series of acquired mutations affecting a single cell and its clonal progeny. 6  Benign  when its microscopic and gross characteristics are relatively innocent,  remain localized and not spread to other sites  easily manageable with surgical removal  patients generally survive  may cause significant morbidity and sometimes even lethal Malignant  collectively referred to as cancers, derived from the Latin word for “crab”—that is, they adhere to any part that they seize in an obstinate manner, similar to a crab’s behavior  can invade and destroy adjacent structures and spread to distant sites (metastasize) to cause death 7 Comparison of Benign & Malignant Tumors 8 Invasion & Metastasis Abnormal cancer cells proliferate & spread to other parts of the body Invasion – direct migration & penetration into neighboring tissues Metastasis – cancer cells spread (metastasize) via lymphatic system & blood vessels 9  Multistep Carcinogenesis 1. Initiation: carcinogen (physical, chemical or biological agents) causes a permanent change in DNA 2. Promotion: the initiated cell is stimulated to grow by a promoter, examples of tumor promoters are alcohol, high estrogen, dietary fat, chronic irritation, ultraviolet light, and chemicals like dioxin, saccharin, polychlorinated biphenyl (PCBs) 3. Progression & Malignancy: Stepwise development of a pre-neoplastic cell as it acquires additional mutations (irreversible) leading to malignancy (invasive cancer) https://med.libretexts.org/Courses/American_Public_University/APUS%3A_An_Introduction_to_Nutrition_%28Byerley%29/APUS%3A_An_Introduction_to_Nutrition_1st_Edition/07%3A_ Nutrition_and_Cancer/7.02%3A_Carcinogenesis 10 The main steps in the formation of a metastasis 11 Fidler IJ (2003) Nat Rev Cancer 3(6):453-8  Metastasis: process by which a tumor cell leaves the primary tumor, travel to a distant site via the circulatory system and then establishes a secondary tumor. Vascularization of primary tumor  Tumor grows through the synthesis and secretion of pro-angiogenic factors by the tumor and surrounding stroma Invasion of the organ stroma through enhanced expression of enzymes (MMP9) Invasion of the lymphatic or vascular channels Tumors cells enter circulation  Must survive turbulence of circulation and evade both immune and non-immune mechanisms 12  Cells arrest in the capillary beds of distant organs Extravasation into distant organ Survival and proliferation in target organ  Depends on multiple interactions between tumor cell and organ microenvironment 13 Metastasis in not random Seed and soil hypothesis  1889: Stephen Paget analyzed autopsy records of 735 women with breast cancer  Metastasis to distant sites was not due to chance  Certain tumor cells (the “seed”) has an affinity for the milieu (the “soil”) of certain organs.  Metastases resulted when the seed and soil were compatible Metastasis is determined by purely mechanical mechanisms such as anatomical and hemodynamic factors of the vascular system (J. Ewing, 1929) Regional metastases can be attributed to anatomic and mechanical factors but distant organ metastases is specific (Sugarbaker, 1964)  Lymphatic drainage to regional lymph nodes  Organ-specific metastases:  Breast, prostate, and lung cancer metastasized to the bone  Colorectal cancer metastasized to the liver 14 Principles of the Seed and Soil Hypothesis Tumors are biologically heterogeneous and contain subpopulations of cells with different angiogenic, invasive, and metastatic properties Metastasis is a selective process for cells that succeed in invasion, embolization, survival in the circulation, arrest in a distal capillary bed, extravasation into the distant organ, and survival and proliferation in the distant organ The outcome of metastasis depends on multiple interactions between the metastatic subpopulation in the primary tumor and the host organ microenvironment 15 Top 10 Cancers in Hong Kong 16 https://www3.ha.org.hk/cancereg/top10incidence.html Causes and risk factors of cancer Cancers can be caused by a number of different factors and, as with many other illnesses, most cancers are the result of exposure to a number of different causal factors. Modifiable risk factors include: 1. Alcohol The evidence that all types of alcoholic drinks are a cause of a number of cancers is now stronger than ever before. Alcohol can increase the risk of six types of cancers, including colorectal, breast, mouth, pharynx and larynx (mouth and throat), oesophageal, liver and stomach The evidence suggests that in general, the most alcohol drinks people consume the higher the risk of many cancers, and that even moderate alcohol intake increases the risk of cancer. 17 2. Being overweight or obese Excess weight has been linked to an increased risk of developing different cancers, including colorectal and pancreatic cancers. In general, greater weight gain, particularly as adults, is associated with greater cancer risks because of inflammation, insulin resistance, hormone imbalance, weaken immune system function, lifestyle factors, etc. 3. Diet and nutrition Experts suggest that diets and nutritional intake, particularly diets high in red meats, processed meats, salted foods and low in fruits and vegetables have an impact on cancer risks, particularly colorectum, nasopharynx and stomach. 4. Physical activity Regular physical activity not only helps to reduce excess body fat and the cancer risks associated with this, but being physically active can help to reduce the risks of developing colon, breast and endometrial cancers. 18 5. Tobacco Tobacco smoke contains at least 80 different cancer-causing substances (carcinogenic agents). When smoke is inhaled the chemicals enter the lungs, pass into the blood stream and are transported throughout the body. This is why smoking or chewing tobacco not only causes lung and mouth cancers but is also related to many other cancers. The more a person smokes, the younger they start, and the longer they keep smoking, all further increase the risk of cancer. Currently tobacco use is responsible for around 22% of cancer deaths. 6. Ionizing radiation Manmade sources of radiation can cause cancer and are a risk for workers. These include radon, x-rays, gamma rays and other forms of high-energy radiation. Prolonged and unprotected exposure to ultraviolet radiations from the sun, sunlamps and tanning beds can also lead to melanoma and skin malignancies. Fair skinned people, individuals with a lot of moles or who have a family history of melanoma or non-melanoma skin cancer, are at highest risk. However, people of all skin tones can develop skin cancer, including individuals with darker skin. 19 7. Work place hazards Some people risk being exposed to a cancer-causing substance because of the work that they do. For example, workers in the chemical dye industry have been found to have a higher incidence than normal of bladder cancer. Asbestos is a well-known workplace cause of cancer - particularly a cancer called mesothelioma, which most commonly affects the covering of the lungs. 8. Infection Infectious agents are responsible for around 2.2 million cancer deaths annually. This does not mean that these cancers can be caught like an infection; rather the virus can cause changes in cells that make them more likely to become cancerous. Around 70% of cervical cancers are caused by Human papillomavirus (HPV) infections, while liver cancer and Non-Hodgkin Lymphoma can be caused by the Hepatitis B and C virus, and lymphomas are linked to the Epstein-Barr virus. Bacterial infections have not been thought of as cancer-causing agents in the past, but more recent studies have shown that people who have helicobacter pylori infection of their stomach develop inflammation of the stomach lining, which increases the risk of stomach cancer. 20 Non-modifiable risk factors include: 1. Age Many types of cancer become more prevalent with age. The longer people live, the more exposure there is to carcinogens and the more time there is for genetic changes or mutations to occur within their cells. 2. Cancer-causing substances (carcinogens) Substances which change how a cell behaves, increasing the chances of developing cancer. Genes are the coded messages inside a cell that tell it how to behave (i.e. which proteins to make), mutations or changes to the gene, such as damage or loss, can alter how that cell behaves making it more likely to be cancerous. 21 3. Genetics Some people are unfortunately born with a genetically inherited high risk for a specific cancer (genetic predisposition). This does not mean developing cancer is guaranteed, but a genetic predisposition makes the disease more likely. For example, women that carry the BRCA 1 and BRCA 2 breast cancer genes have a higher predisposition to developing this form of cancer than women with a normal breast cancer risk. 4. The immune system People who have weakened immune systems are more at risk of developing some types of cancer. This includes people who have had organ transplants and take drugs to suppress their immune systems to stop organ rejection, plus people who have HIV or AIDS, or other medical conditions which reduce their immunity to disease. 22 23  Hallmarks of cancer Mutations and epigenetic alterations impart to cancer cells a set of properties that are referred to collectively as cancer hallmarks. The hallmarks of cancer were originally six biological capabilities acquired during the multistep development of human tumors and have since been increased to eight capabilities and two enabling capabilities. The idea was coined by Douglas Hanahan and Robert Weinberg in their paper "The Hallmarks of Cancer" published January 2000 in Cell. 24  These hallmarks constitute an organizing principle for rationalizing the complexities of neoplastic disease. They include sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis.  Underlying these hallmarks are genome instability, which generates the genetic diversity that expedites their acquisition, and inflammation, which fosters multiple hallmark functions.  In addition to cancer cells, tumors exhibit another dimension of complexity: they incorporate a community of recruited, ostensibly normal cells that contribute to the acquisition of hallmark traits by creating the “tumor microenvironment.”  Recognition of the widespread applicability of these concepts will increasingly affect the development of new means to treat human cancer.  In an update published in 2011 ("Hallmarks of cancer: the next generation"), Weinberg and Hanahan proposed two new hallmarks: (1) abnormal metabolic pathways and (2) evasion of the immune system, and two enabling characteristics: (1) genome instability, and (2) inflammation. 25 1. Self-Sufficiency in Growth Signals Tumors have the capacity to proliferate without external stimuli. Gain-of-function mutations that convert proto-oncogenes to oncogenes. Oncogenes encode proteins called oncoproteins that promote cell growth in the absence of normal growth-promoting signals. 26  Cancers may secrete their own growth factors or induce stromal cells to produce growth factors in the tumor microenvironment. Cancer cells often acquire growth autonomy as a result of mutations in genes that encode components of signaling pathways downstream of growth factor receptors. RAS is the most commonly mutated oncogene in human tumors. RAS commonly is mutated in human cancers and normally flips between resting GDP-bound state and active GTP-bound state; mutations block hydrolysis of GTP to GDP, leading to unchecked signaling. 27  1 2 1. Binding of a growth factor to its specific receptor on the cell membrane 2. Transient and limited activation of the growth factor receptor, which in turn activates several signal transducing proteins on the inner leaflet of the plasma membrane 3 3. Transmission of the transduced signal across the cytosol to the nucleus by second messengers or a cascade of signal transduction molecules 4. Induction and activation of nuclear regulatory factors that initiate and regulate DNA transcription and the biosynthesis of other cellular components that are 4 needed for cell division, such as organelles, membrane components, and ribosomes 5. Entry and progression of the cell into the cell cycle, resulting ultimately in cell division 5 28 2. Insensitivity to Growth Inhibitory Signals: Tumor Suppressor Genes Tumor suppressor genes  Encode proteins that regulate cell cycle checkpoints  When a DNA damaged cell undergoes division  These proteins will halt its proliferation  Initiate DNA repair  If DNA repair is not possible, induce cell death by apoptosis Examples of Tumor suppressor genes In cancer: 1. Retinoblastoma (Rb) gene 2. p53 gene (Guardian of the genome)  Tumor suppressor genes are inactivated 3. APC gene 4. WT gene  Uncontrolled proliferation of mutated cells 5. BRCA 1 & BRCA 2 gene 29  3. Altered cellular metabolism In general, glucose uptake of malignant tumors is high, “glucose-hunger” Even in the presence of ample oxygen, cancer cells prefer lactic acid fermentation over oxidative phosphorylation (Warburg effect) Lactic acid fermentation rapidly yields metabolic intermediates that are required for the synthesis of macromolecules In normal cells, 38 ATPs are generated with one glucose molecule, whereas only 2 ATPs are generated in cancer cells Int. J. Mol. Sci. 2021, 22(12), 6173; https://doi.org/10.3390/ijms22126173 30  4. Evasion of apoptosis Apoptosis = Programmed cell death Evasion of apoptosis by cancer cell mainly involves acquired abnormalities that interfere with the intrinsic (mitochondrial) pathway of apoptosis. 1. The most common abnormalities involve loss of p53 1 function, either by way of TP53 mutations or overexpression of the p53 inhibitor MDM2. 2. Other cancers evade cell death by overexpressing anti- apoptotic members of the BCL2 family, such as BCL2, 2 BCL-XL, and MCL1, which protect cells from the action of BAX and BAK, the pro-apoptotic members of the BCL2 family. 3. Another group of factors that function as negative 3 regulators of the intrinsic pathway is known as inhibitor of apoptosis proteins (IAPs), which bind caspase-9 and prevent apoptosis 31 5. Limitless Replicative Potential (Immortality) Telomeres are chromosome ends Telomere shorten after multiple replication (60-70 cycles), at which point they reach a stage of senescence (unable to divide) Cancer cells involve the up regulation of telomerase, the enzyme that maintains telomeres So cell can now divide indefinitely without entering senescence 32  6. Sustained Angiogenesis Formation of new blood vessels --- Angiogenesis Cancer cells depend on the body for oxygen and nutrients A growing tumor requires access to oxygen, nutrients and waste disposal. Beyond a certain size, typically 1 mm, diffusion alone is insufficient for providing these necessities; the surface area to volume ratio becomes too low and the developing tumor begins to starve. In response, vascularization of tumors is essential for their growth and is controlled by the balance between angiogenic and antiangiogenic factors Hypoxia triggers angiogenesis through the actions of HIF-1α on the transcription of the proangiogenic factor VEGF 33  7. Invasion & Metastasis Invasion of adjacent tissue and metastasis, the major causes of cancer related morbidity and mortality 2 phases 1. Invasion of extracellular matrix (ECM) 2. Vascular dissemination, homing of tumor cells and colonization Four steps of invasion of ECM:  Loosening of cell–cell contacts,  Degradation of ECM,  Attachment to novel ECM components,  Migration of tumor cells 34 A. Loosening of intercellular junctions Normal cells are tightly bound to each other by Cadherins During invasion, production of cadherins is down-regulated Detachment of cancer cells from each other B. Degradation of ECM Tumor cells secrete proteolytic enzymes to degrade ECM proteins They also induce surrounding fibroblasts and inflammatory cells to secrete enzymes  Matrix metalloproteinases (MMPs)  Plasminogen activator  Collagenase C. Migration and Invasion Multistep processes involving many types of receptors and signaling molecules Cleavage products of matrix proteins and growth factors like insulin-like growth factors (IGF) act as chemotactic agents Amoeboid movement of cancer cells Make their way into vascular system 35  8. Evasion of Immune Surveillance Tumor cells can be recognized by the immune system as non-self and destroyed. The immune system is to constantly “scan” the body for emerging tumor cells and destroy them. Tumor antigens are protein molecules expressed on tumor cells. The different classes of tumor antigens include products of mutated genes, overexpressed or aberrantly expressed proteins, and tumor antigens produced by oncogenic viruses. Antitumor activity is mediated by predominantly cell- mediated mechanisms. Tumor antigens are presented on the cell surface by MHC class I molecules and are recognized by CD8+ CTLs. Tumor cells are killed by cytotoxic T Lymphocytes. https://www.researchgate.net/figure/Mechanism-of-neoantigen-induced-CD8-T-cell-mediated- antitumor-immunity-A-Neoantigens_fig3_373693165 36  Mechanism of immune evasion by tumor cells 1. Selective outgrowth of antigen-negative variants 2. Loss or reduced expression of MHC molecules 3. Inhibit T-cell activation by upregulating negative regulatory checkpoint 4. Secretion of immunosuppressive factors (e.g TGF- β, PD-1 ligands) 5. Induction of regulatory T cells (Tregs) If tumors grow in immunocompetent individuals, tumor cell are invisible to host immune system and activate mechanism that suppress host immunity. ----- TUMORS EVADE HOST IMMUNITY! Immunosuppressed patients have an increased risk for development of cancer, particularly types caused by oncogenic DNA viruses. 37 Laboratory Diagnosis of Cancer 1. Cytopathological examination Cytologic (Papanicolaou) smears provide method for the detection of cancer Widely used for discovery of carcinoma of the cervix Now it is used to investigate many other forms of suspected malignancy Exfoliative cytology: spontaneously exfoliated cells from the lining of an organ to body cavity, e.g pleural fluids, peritoneal fluids, joint fluids, urine, sputum, etc Fine-needle aspiration cytology: involves aspiration of cells from a mass, followed by cytologic examination of the cells after they have been spread out on a slide.  This procedure is used most commonly with readily palpable lesions affecting the breast, thyroid gland, lymph nodes, and salivary glands.  Modern imaging techniques permit extension of the method to deeper structures, such as the liver, pancreas, and pelvic lymph nodes. 38 2. Histopathological examination Based on microscopic features of the neoplasm Accurate diagnosis can be made in majority of the cases tissues obtained for diagnosis: needle biopsy, endoscopic biopsy, incision biopsy, excision biopsy 39 3. Immunohistochemistry a powerful technique adjunct to routine histologic examination. Detect specific proteins in tissue sections By using antibodies that recognize and bind to those proteins and makers that allow visualization of the antibody-antigen complex. Application:  Provide important information about the nature of the tumor, including its type and potential aggressiveness  Help differentiate between different types of tumors  Determine the extent of tumor involvement in the tissue 40 4. Flow Cytometry used routinely in the classification of leukemias and lymphomas. In this method, fluorescently labeled antibodies against cell surface molecules and differentiation antigens are used to obtain the phenotype of malignant cells 5. Tumor Markers Products of tumors that can be detected in the cells, blood, body fluids can be used to monitor the progression, or evaluate the effectiveness of treatment of cancer  Prostate-specific antigen (PSA) for prostate cancer  Cancer antigen 125 (CA125) for ovarian cancer  Alpha-fetoprotein (AFP) for liver and testicular cancers  Carcinoembryonic antigen (CEA) for lung, stomach, colon, ovarian and breast cancers  Carbohydrate antigen 19-9 (CA19-9) for pancreatic, gallbladder and stomach cancers 41 6. Molecular Diagnosis Molecular techniques:  Polymerase Chain Reaction (PCR): to detect and amplify specific DNA sequences associated with cancer  Fluorescence in situ hybridization (FISH): to detect genetic changes and chromosomal abnormalities  Gene sequencing: to identify mutations and other genetic changes  Next-generation sequencing (NGS): advanced method of reading DNA! Read genetic changes in short amount of time Applications:  Diagnosis of malignancy  Prognosis and behavior  Detection of minimal residual disease  Diagnosis of hereditary predisposition to cancer  Therapeutic decision-making 42 References Vinay Kumar, Abul K. Abbas, Jon C. Aster, Andrea T. Deyrup. (2022). Robbins & Kumar Basic Pathology (11th ed.). Elsevier. Hanahan D and Weinberg R A. (2000). The hallmarks of cancer. Cell. 100(1): 57-70. Hanahan D and Weinberg R A. (2011). Hallmarks of Cancer: The Next Generation. Cell. 144(5): 646-674. 43 Concept Check (T or F) 1. The major cause of death in Hong Kong is Cancer. 2. If left untreated, tumors can grow and spread into the surrounding normal tissue, or to other parts of the body via the nervous systems. 3. Tumor can be divided into benign and malignant. 4. Malignant tumor is easily manageable and with surgical removal. 5. Benign tumor resembles to tissue of origin. 6. Carcinogenesis is a single step process. 7. Examples of tumor promoters are alcohol, high estrogen, dietary fat, etc. 8. Smoking and alcohol consumption are Group 2A carcinogen. 9. Seed and soil hypothesis is concerned about Metastasis. 10. Asbestos is a well-known workplace cause of Adenocarcinoma of Lung. 11. 100% cervical cancers are caused by Human papillomavirus (HPV) infections. 12. Carcinogens are substances which change how a cell behaves, increasing the chances of developing cancer. 44 13. Insensitivity to Growth Inhibitory Signals is a hallmark of cancer, where cancer cells can ignore signals leading to uncontrolled proliferation of mutated cells. 14. Warburg effect is that cancer cells prefer oxidative phosphorylation over lactic acid fermentation. 15. Hypoxia triggers angiogenesis. 16. Cancer cells that avoid immune destruction can selectively outgrowth antigen-negative variants. 17. p53 gene is the example of oncogene. 18. Tumor cells secrete proteolytic enzymes to degrade extracellular matrix (ECM) proteins. 19. Glucose uptake of malignant tumors is low. 20. Carcinoembryonic antigen (CEA) is a tumor maker for lung, stomach, colon, ovarian and breast cancers 45