Lectures 13-17 Study Guides PDF

Lecture 13 Immune-Based Therapy and Keytruda Origins: Bessie Dashiell's case inspired Dr. William Coley to explore cancer treatments. Observation: Post-infection immune responses could regress tumors. Modern extension: Keytruda (anti-PD-1 antibody) enhances immune response to target tumors. Mechani...

Lecture 13 Immune-Based Therapy and Keytruda Origins: Bessie Dashiell's case inspired Dr. William Coley to explore cancer treatments. Observation: Post-infection immune responses could regress tumors. Modern extension: Keytruda (anti-PD-1 antibody) enhances immune response to target tumors. Mechanism of Action: PD-1: Regulates immune self-tolerance; tumors exploit it to avoid immune attack. Anti-PD-1: Restores immune function, making tumors more susceptible to immune clearance. Side Effects: Overactive immune responses can result in autoimmunity (e.g., lupus). Provenge Therapy: Dendritic cell-based immunotherapy for prostate cancer. Extends survival by an average of 4.1 months. Procedure involves antigen loading and reinfusion of dendritic cells. Apoptosis and p53 Apoptosis Basics Definition: Programmed cell death, a vital mechanism to eliminate damaged cells. Trigger Events: DNA damage Loss of cell adhesion in cancer Aberrant cell states (e.g., hypoxia, oncogene signaling) Key Features: Cell shrinkage Chromatin condensation Membrane blebbing Formation of apoptotic bodies Role of p53 Discovery: Found through co-immunoprecipitation with viral proteins. Frequently mutated in cancers (~50% of cases). Functions: Stabilized under cellular stress (e.g., DNA damage). Activates cyclin inhibitor p21 for cell cycle arrest or apoptosis. Short-lived protein in healthy cells (degraded within 20 minutes). Mutational Impact: Missense mutations often disrupt DNA-binding domain. Creates dominant-negative proteins that interfere with normal p53 function. Elephant Cancer Resistance: Elephants have 40 copies of the p53 gene, enhancing their anti-cancer mechanisms. Mechanics of Apoptosis Caspase Cascade: Apoptosis is executed by caspases (proteolytic enzymes). Pathway is tightly regulated to prevent unintended cell death. Apoptosis vs. Necrosis: Apoptosis: Controlled, avoids inflammation. Necrosis: Uncontrolled, causes inflammation and damage to surrounding tissue. Assays for Detection: DNA fragmentation Membrane integrity loss Caspase activation markers Key Connections p53 and Cancer Resistance: Amplification of Mdm2, a p53 regulator, leads to its degradation in some cancers. Mutations enable cells to evade apoptosis, promoting cancer progression. Therapeutic Implications: Drugs targeting apoptotic resistance (e.g., reactivating p53) show promise in cancer therapy. Questions for Review How does Keytruda differ from Provenge in its approach to immunotherapy? Why are most p53 mutations missense, and what functional consequences do they have? Describe the differences between apoptosis and necrosis. How does phosphorylation affect the activity of p53 and Mdm2 during cellular stress? Discuss the significance of p53's short half-life in normal cells. Lecture 14 CAR T-Cell Therapy Overview: CAR T-Cell Generations: 1st Gen: CD3 signaling domain to activate TCR. 2nd Gen: Added costimulatory domain for proliferation. 3rd Gen: Included survival domain for enhanced persistence. Procedure: Gene therapy conducted ex vivo on patient’s T cells. Cells engineered to target CD19 antigen on B cells, both normal and cancerous. High remission rates observed (e.g., 27/30 patients achieved cancer disappearance). Applications: Effective in treating blood cancers like leukemias and lymphomas. Used for relapsed/refractory patients after chemotherapy or stem cell transplant. Side Effects: Cytokine release syndrome (due to rapid T-cell activation). Immune-related complications. Ras Protein and Tyrosine Phosphorylation Networks Ras Overview: Role: A GTPase involved in signal transduction pathways regulating cell growth and survival. Common Mutation: Glycine 12 → Valine; disrupts GTP hydrolysis, leading to constitutive activation. Significance: Most commonly mutated oncogene in human cancers. Mechanism of Ras Activation: Growth factors bind to receptors, initiating tyrosine phosphorylation. SH2 Domains: Bind phospho-tyrosines and link receptors to Ras. Ras activates multiple downstream pathways critical for tumor progression. Ras-Activated Pathways 1. MAP Kinase Pathway: Amplifies Ras signals to promote transcription and translation. Drives inappropriate mitosis and cell cycle progression. 2. Lipid Signaling Pathway: Activates Rho GTPases (e.g., Rho, Rac, Cdc42). Functions: Rho: Enables F-actin assembly for cell migration and adhesion. Akt: Promotes cell growth, survival, and escape from apoptosis. 3. Cell Migration Pathway: Facilitates cytoskeletal reorganization for cell motility. Allows cancer cells to invade and escape their tissue of origin. Ras and Cancer Progression Activates 11+ pathways, contributing to: Inappropriate Mitosis: Via MAPK and Akt signaling. Escape from Senescence: Evades growth suppression. Apoptosis Resistance: Akt signaling prevents programmed cell death. Loss of Cell Adhesion: RalA/B signaling promotes tissue invasion. Cell Migration: Drives metastatic potential. Immune Evasion: Shields tumors from immune detection. Angiogenesis: Induces blood vessel formation for nutrient supply. Immediate Early Genes (IEGs) What Are IEGs? Genes rapidly activated upon growth factor stimulation. Do not require new protein synthesis for activation. Functions: Include transcription factors (e.g., Myc), glucose transporters, and signaling/migration factors. Key to initiating cell cycle entry from quiescence (G0). Detection: Microarray studies show time-dependent expression post-serum stimulation. Key Questions to Consider How do CAR T-cells target and destroy cancerous B cells? What makes Ras mutations so potent in driving oncogenesis? Explain the role of SH2 domains in signal transduction. How does Ras contribute to the hallmarks of cancer (e.g., metastasis, apoptosis resistance)? Discuss the role of Immediate Early Genes in growth factor signaling. Lecture 15 Gamma Knife Radiotherapy Purpose: Uses Cobalt-60 gamma radiation for precise targeting of tumors. Multiple beams (192 in modern versions) converge at a single point to minimize damage to surrounding tissues. Applications: Ideal for treating inoperable brain cancers. Also known as stereotactic radiotherapy. Multi-Step Tumor Progression Steps in Cancer Development: Inappropriate Mitosis: Activation of cell cycle. Escape from Senescence: Avoidance of growth arrest. Resistance to Apoptosis: Loss of cell death mechanisms. Loss of Cell Adhesion: Enables escape from tissue origin. Acquisition of Migration: Allows invasion and metastasis. Immune Evasion: Avoids detection by immune system. Angiogenesis: Formation of new blood vessels for nutrient supply. Insights into Progression: Cancer development is a slow, multi-event process. Colon cancer progression: APC Mutation: An early event affecting tissue architecture. Aberrant Morphologies: Dysplasia, hyperplasia, neoplasia. Removal of benign polyps can reduce cancer risk by 80%. Bcl-2 and Apoptosis Role of Bcl-2: Discovery: Found in translocations promoting high expression in B-cell lymphomas. Oncogenic Activity: Weak oncogene; prolongs B-cell lifespan (21 days vs. 7 days in normal cells). Results in triple the normal B-cell population. Mitochondrial Role in Apoptosis: Cytochrome C: Normally in mitochondrial intermembrane space; part of electron transport chain. Released during apoptotic signaling, activating caspases. Bcl Protein Family: Regulate mitochondrial membrane channels controlling Cytochrome C release. Types: Pro-Apoptotic (e.g., Bim): Open channels to promote cell death. Anti-Apoptotic (e.g., Bcl-2): Close channels to promote survival. Balance between these proteins dictates cell fate. The Wheel of Death: Cytochrome C + Apaf-1: Forms a 7-spoked apoptosome. Activates caspases, initiating the apoptotic cascade. Key Concepts in Tumorigenesis Genetic and Tissue-Level Evidence: Multiple mutations (~6) are needed for epithelial cancer development. Tissue changes (e.g., benign adenomas) precede malignancy. Familial Syndromes: APC Mutation in Familial Polyposis: Thousands of polyps by age 20; median cancer age ~46 years. Darwinian Evolution of Cancer: Selection pressures favor mutations that promote survival and growth. Study Questions How does Gamma Knife therapy minimize damage to healthy tissues? Describe the sequence of events in multi-step tumor progression. Explain the role of APC mutations in colon cancer development. How does Bcl-2 contribute to apoptosis resistance in cancer? What is the significance of the “Wheel of Death” in apoptosis? Lecture 16 Tumor Progression and Darwinian Selection Cancer Cells Compete for Resources: Clonal populations evolve through mutations that provide survival advantages. Analysis estimates ~6 cancer-causing events (mutations) are required for epithelial cancers. Features of progression: Consistent mutation rate across populations. Similar estimates for various cancers. Indicates ~1 mutation per 1,000,000 cell divisions over 10–15 years. Genomic Instability: Promotes diverse genotypes within a tumor, driving progression. Fluorescence-activated cell sorting (FACS) reveals varying gene expression and growth potential among cancer cells. Cooperation Between Oncogenes and Tumor Suppressors Transformation in Humans vs. Rodents: Human cells require overcoming 5+ pathways for oncogenesis. Examples: Mitogenic and mutagenic agents collaborate (e.g., ethanol and smoking increase oral cancer risk 100x). Mitogenic Agents and Chronic Inflammation Examples of Cancer Promotion: Kostmann Syndrome: Mutant neutrophils die; immune system cycles rapid cell divisions, leading to acute myelogenous leukemia (AML). Menstrual Cycles and Breast Cancer: More cycles correlate with higher risk. Hormone-driven proliferation during cycles is a key factor. Hepatitis B/C and Liver Cancer: Promotes mitogenic cell division without being directly mutagenic. Chronic infection increases liver cancer risk 100x. Role of NSAIDs: Suppress inflammation and reduce carcinoma incidence. Long-term aspirin use decreases: Lung cancer: 32% reduction. Breast cancer: 30% reduction. Colorectal cancer: 65% reduction. Stomach cancer: 60% reduction. However, ~20,000 annual deaths are related to NSAID-induced gastrointestinal complications. Inflammation and Cancer Mechanism: Inflammation fosters interaction between stromal and pre-cancerous epithelial cells. Mitogens in inflammation promote cell division, increasing mutation rates and oncogenesis. Examples: Hepatitis-associated liver cancer: hepatocyte death and division cycle promotes mutations. Chronic inflammatory states often precede carcinomas. Genetic and Environmental Interplay Dose-Response Curves: Different thresholds for mutagenic vs. mitogenic agents. Birth Control Pills and Cancer Risk: Minimal effect on DNA synthesis; natural hormones drive most risk. Protective for ovarian, endometrial, and colon cancers. Slight increase in breast cancer rates. Key Concepts in Cancer Development Darwinian Selection in Tumors: Progressive mutations drive clonal expansion. Genomic Instability: Increases tumor heterogeneity and adaptability. Mitogenic-Driven Oncogenesis: Chronic stimulation of cell division underlies many cancers. Chronic Inflammation: Creates an environment conducive to tumor growth. Study Questions Explain the significance of genomic instability in cancer progression. How do mitogenic agents like ethanol and smoking collaborate to promote cancer? What is the role of inflammation in cancer initiation and progression? Discuss the benefits and risks of NSAID use in cancer prevention. How does the interplay of hormones and cell division influence breast cancer risk? Lecture 17 Cachexia: Wasting Syndrome Definition: A paraneoplastic syndrome (systemic effects distant from the tumor). Impact: Occurs in ~80% of cancer patients, responsible for ~20% of cancer-related deaths. Characterized by severe weight and muscle loss. Cause: Tumors secrete Impl2, an inhibitor of IGF-1. Treatment: Overexpression of IGF-1 can reverse effects. Rational Cancer Treatment Traditional vs. Rational Approaches: Traditional (e.g., chemotherapy): Targets general cell division and cell cycle progression. Effective but with significant side effects (e.g., secondary cancers from alkylating agents). Rational Treatment: Targets specific molecular changes in cancer cells. Results in improved specificity and reduced side effects. Case Studies in Rational Treatment: Breast Cancer: Molecular profiling (microarrays) identifies genetic subtypes. “Good” genetic signatures do not benefit from aggressive chemotherapy. B-cell Lymphomas: Microarrays distinguish subtypes with different prognoses. Treatment tailored to subtype (e.g., anti-NF-κB therapy for PMBL and ABC DLBCL). Molecular Profiling in Cancer Microarrays: Analyze gene expression to classify cancer subtypes. Guide personalized treatment strategies. RNA Sequencing (RNA-seq): Emerging as a more detailed replacement for microarrays. Differentiation-Based Treatment Principle: Instead of killing cancer cells, induce them to differentiate, exiting the cell cycle. Example: Acute promyelocytic leukemia (APL) treated via differentiation therapy targeting PML-RAR fusion. Exploiting Aberrant Cancer Behaviors Example: Liver Cancer Without G2/M Checkpoint: DNA-damaging agents (radiation or chemotherapy) cause lethal fragmentation in dividing cancer cells. Normal cells arrest and repair damage. Small Molecule Drugs and Monoclonal Antibodies Small Molecules: Inhibit intracellular oncogenes. Over 3,000 in development. Can penetrate plasma membranes to target internal processes. Monoclonal Antibodies: Target extracellular proteins. Used for surface markers or secreted factors. Cancer Treatment Development Process Laboratory Testing: Assess efficacy in tissue culture (e.g., Bcr-Abl inhibitors for leukemia). Animal Models: Ensure drug stability and activity in vivo. Clinical Trials: Phase I: Test toxicity and safe dosing in small groups. Phase II & III: Evaluate efficacy, statistical significance, and survivor benefits in larger groups. Resistance and Adaptation Mechanisms of Resistance: Protein mutations or gene amplification circumvent drug efficacy. Chronic Cancer Management: Cancer viewed as a chronic condition. Aim to extend remission and manage relapses. Key Examples of Targeted Therapy Abl Kinase in Leukemia: Bcr-Abl fusion drives cancer progression. Drugs target this fusion without harming non-transformed cells. Study Questions What is cachexia, and how does it relate to IGF-1 levels? Compare and contrast traditional chemotherapy with rational cancer treatment. How does molecular profiling improve cancer treatment strategies? Explain the role of differentiation therapy in cancer management. What challenges are associated with small molecule inhibitors in cancer therapy?