L28 Cancer Immunology PDF

Suggested Reading for L28: Basic Immunology, Chapter 10 (section on tumors) MICRG 1553 Immunology Kathryn Leyva, Ph.D. Learning Objectives 1. Compare/contrast the different types of tumor antigens discussed and understand their role in cancer development & treatment....

Suggested Reading for L28: Basic Immunology, Chapter 10 (section on tumors) MICRG 1553 Immunology Kathryn Leyva, Ph.D. Learning Objectives 1. Compare/contrast the different types of tumor antigens discussed and understand their role in cancer development & treatment. a. Understand the difference between tumor-specific vs tumor-associated antigens b. Explain the mechanism of action of imatinib, trastuzumab, and pertuzumab c. Understand how the HPV vaccine protects against virally-induced cancer 2. Describe the four main immune mechanisms of tumor rejection. a. CTLs, NK cells, macrophages, and antibodies b. Understand that CTL activity is most effective in tumor eradication. 3. Understand immunoediting of cancer cells leading to immune evasion. 4. Explain the four ways discussed in which tumor cells can evade the immune system. 5. Understand the types of immunotherapies for treating cancers discussed, including knowing how each works to modulate the immune system: a. Therapeutic cancer vaccines b. Oncolytic viral therapy c. Adoptive T cell therapy d. Immune checkpoint inhibitors 2 Cell Cycle and Cancer  The cell cycle is a series of events in which the cell increases in size, duplicates its cellular contents and DNA, and then divides into two daughter cells.  Checkpoints regulate normal progression of the cell cycle!  Cancer can occur when mutations accrue in the DNA, allowing for progression of the cell cycle  Genomic instability, including without mutations or other chromosomal regulation at alterations, is a hallmark of the checkpoints! carcinogenesis.  Mutations are passed on to  Genomic instability creates daughter cells. mutations! 3  Driver Mutations  Mutations that dysregulate the cell cycle are called driver mutations, as they “drive” the cell to cancer.  Mutations in two classes of genes cause cell cycle dysregulation: 1. Tumor suppressor genes: encode for proteins that inhibit progression through the cell cycle.  Mutations in tumor suppressor genes result in defective proteins that are unable to suppress (halt) cell cycle progression when needed. 2. Proto-oncogenes: encode for proteins that promote progression through the cell cycle.  Mutated proto-oncogenes = oncogenes, resulting in constitutive activation of signaling proteins in growth pathways.  Other mutations that occur are often referred to as passenger mutations, as they don’t affect the cell cycle, but lead to antigenic differences between normal and cancerous cells. 4 Tumor Antigens  Cancer cells produce proteins that the immune system may recognize as foreign = tumor antigens.  Two main categories of tumor antigens: 1. Tumor-specific antigens (TSAs)  Unique to tumor cells. Includes:  Gene mutations that create neoantigens.  Neoantigens = new proteins expressed by cancer cells because of DNA mutations.  Incorporation of oncogenic viruses. 2. Tumor-associated antigens (TAAs) 5 TSAs: Oncogenes https://clincancerres.aacrjournals.org/content/13/4/1089.figures-only  Proto-oncogenes mutated to become oncogenes produce proteins that are different from normal proteins = tumor-specific antigens. The  Ex: Philadelphia chromosome: t(9;22) resulting signaling in a fused bcr-abl gene. pathways in this figure are FYI  Abl is a tyrosine kinase that, when fused with Bcr (FYI: breakpoint cluster region) becomes constitutively active!  Results in activation of signaling pathways, FYI: This translocation occurs in ~90% of patients leading to increased proliferation, survival, & with CML (a type of leukemia; see next slide). motility. 6 Clinical Application: CML File:Time cover on Glivec 28 May 2001.png  Treatments for chronic myelogenous leukemia (CML) include inhibiting bcr-abl activity.  One drug, imatinib (Gleevec), is a specific bcr-abl tyrosine kinase inhibitor. Blocking the kinase activity inhibits tumor cell proliferation.  This is targeted therapy; the bcr-abl fusion protein is only found in cancerous cells, so the drug does Video: Imatinib MOA https://www.youtube.com/ not affect normal cells. watch?v=gin_pSgpPhk  FYI: there are other bcr-abl inhibitors approved for imatinib-resistant CML. 7 TSAs: Oncogenic Viruses  Products of oncogenic viruses can be tumor- specific antigens, eliciting specific anti-tumor immune responses.  Ex: Human papillomavirus (HPV) antigens causing carcinogenesis.  The viral E6 & E7 proteins inactivate the cell cycle regulatory proteins p53 & pRb.  Results in increased proliferation, inhibition of apoptosis, & accumulation of mutations that can lead to cancer. https://www.cell.com/trends/microbiology/fulltext/S0966-842X%2817%2930177-4 8 Clinical Application: HPV Vaccines  HPV vaccines are composed of purified L1 capsid protein of HPV.  The most recent HPV vaccine is Gardasil®9; it is a 9-valent vaccine using L1 protein from 9 HPV strains, 7 of which are responsible for ~90% of all cervical cancers.  Vaccine induces protective immunity against these 9 strains, thus preventing most cases of cervical cancer! https://www.lsbio.com/research- areas/infectious- disease/papillomaviridae 9 Tumor Antigens  Two main categories of tumor antigens: 1. Tumor-specific antigens (TSAs) 2. Tumor-associated antigens (TAAs)  Normal proteins that are inappropriately expressed by tumor cells. a. De-repressed expression = aberrantly expressed normal protein. b. Overexpression of an oncogenic protein (often due to misregulation). c. Increased number of cells leading to increased protein expression (we won’t cover this one). 10 TAAs: De-Repressed Antigens  Repression is a mechanism used to decrease or inhibit the expression of a gene. Removal of repression is called de-repression.  Some cancers inappropriately express genes that normally would not be expressed by that tissue. These are tumor-associated antigens.  Ex: MAGEA3 = melanoma antigen gene  Normally only expressed in the testes; expression is off in somatic cells  Inappropriately expressed in several types of cancer cells Testes Somatic Cell Cancer Cell https://atlasgeneticsoncology.org/gene/41247/magea3-(melanoma-antigen-family-a-3) 11 TAAs: Overexpression of Proteins  Some cancers result in overexpression of normal, cellular proteins; are tumor- associated antigens.  Ex: Her2/neu receptor, an EGF receptor, that is overexpressed on various cancer cells, including breast cancer.  Increased growth factor signaling, resulting in increased proliferation. Clinical Application: Pertuzumab (Perjeta®) & Trastuzumab (Herceptin®) are two monoclonal antibodies that bind to Her2/neu, preventing receptor dimerization and downstream signaling (and possibly increases receptor internalization, too). 12 EGF = epidermal growth factor  Immune Surveillance  The concept of immune surveillance states that a physiological function of the immune system is to recognize and destroy clones of transformed cells before they grow into tumors and to kill tumors after they are formed.  The existence of immune surveillance has been demonstrated by the increased incidence of some types of tumors in immunocompromised experimental animals and humans.  Innate & adaptive immune Red arrows = malignant cells; Blue arrows = immune cells (lymphocyte-rich) IHC showing influx of CD8+ T cells responses occur against tumor cells. IHC = immunohistochemistry 13  Immune Responses to Tumors Tumor-specific CTLs are directed against tumor antigens presented in Class I MHC molecules. CTL activity is the most important immune mechanism for fighting tumors (see next slide)! TNF = tumor necrosis factor; IFN- = interferon-gamma, CTL = cytotoxic T cell 14 Principal Mechanism for Tumor Eradication  The principal mechanism of immune protection against tumor cells is killing of tumor cells by CD8+ cytotoxic T cells (CTLs)!  Tumor antigens are picked up by conventional DCs at the tumor site.  Activation of CTLs in secondary lymphatics.  Tumor-specific effector CTLs migrate back to the site and kill tumor cells. 15  Immune Responses to Tumors NK cells, are capable of Tumor-specific CTLs are destroying tumor cells and are a directed against tumor antigens first-line defense against many presented in Class I MHC tumors. They are effective against molecules. CTL activity is the tumors that have reduced levels most important immune of Class I MHC or are bound with mechanism for fighting anti-tumor antibodies (see bottom tumors (see next slide). left fig). Video: ADCC of tumor cells by NK cells https://www.youtube.com/watch?v=zYh_BpwV6Fo Macrophages are strongly activated by IFN- and kill Antibodies enhance tumor tumors with ROS and by cell destruction by serving secreting TNF. Macrophages as opsonins, by activating also process and present complement, and tumor antigens to T cells. inducing ADCC. ROS = reactive oxygen species; TNF = tumor necrosis factor; CTL = cytotoxic T cell 16 IFN- = interferon-gamma; ADCC = antibody-dependent cellular cytotoxicity Evasion of Immune Responses https://science.sciencemag.org/content/331/6024/1565/F3  Why do immunocompetent individuals get cancer?  Many cancers undergo “immunoediting” to evade anti-tumor immune responses.  Immunoediting describes the process how cancer cells respond to the immune response.  The immune system selects for resistance in cancer.  Immune cell killing is a selective pressure that results in the survival and growth of tumor cells with reduced immunogenicity!  These cells “escape” immune attack and can grow. Optional video on immunoediting – does go into more detail than we will cover: https://www.youtube.com/watch?v=W1z-xSqoKqU 17 Tumor Evasion Mechanisms 1. Tumor cell secretion or expression of immunosuppressive molecules:  Some tumor cells secrete immunosuppressive cytokines.  TGF- (transforming growth factor-beta)  Some tumor cells express ligands that bind to T cell inhibitory receptors (cover in more detail on slide 26).  PD-L1 (programmed death-ligand 1) or PD-L2 2. Activity of suppressor cells Treg cells or other suppressor cells 3. Antigenic loss  Tumor cells that stop expressing tumor antigens prevents T cell recognition of tumor cells. 4. Reduced expression of Class I MHC molecules  Tumor cells that reduce expression of Class I MHC inhibit T cell recognize of tumor antigens. 18 Cancer Immunotherapy  Variety of options to treat cancer: surgery, radiation, and anti-neoplastic agents.  Cancer treatments aimed at stimulating the body’s own immune response to tumor cells can be more specific and less damaging to normal cells.  Cancer immunotherapy = therapies aimed to modulate the immune system response to cancer. 1. Therapeutic cancer vaccines 2. Oncolytic immunotherapy 3. Adoptive T cell therapy 4. Antibody-based therapies 5. FYI: There are others that we won’t discuss:  Cytokines  Non-specific therapies (e.g. BCG vaccine) Optional videos on cancer immunotherapies: https://www.youtube.com/watch?v=jDdL2bMQXfE https://www.youtube.com/watch?v=-NNjDjXSJt0 19 Therapeutic Cancer Vaccines  Dendritic cell-based vaccination:  Dendritic cells (DCs) from the patient are isolated & are incubated (pulsed) with tumor antigens.  Antigen-pulsed DCs are placed back in the patient to activate tumor- specific T cells. Clinical Application: Sipuleucel-T (Provenge®) is an FDA-approved vaccine for treatment of advanced prostate cancer. Patient’s DCs are incubated with a recombinant fusion protein of GM-CSF and the tumor-associated antigen PAP (prostatic acid phosphatase). Provenge MOA 20  Oncolytic Viral (OV) Therapy of  Genetically-engineered oncolytic viruses:  Modified viruses that only replicate in cancer cells plus synthesize the cytokine GM-CSF.  The infected cancer cells lyse, releasing tumor- specific antigens + GM-CSF to stimulate dendritic cells (DCs).  DCs activate T cells against tumor antigens to & GM-CSF promote an anti-tumor immune response. Clinical Application: Imlygic (talimogene laherparepvec or T-VEC), a genetically modified herpesvirus, is the first FDA-approved OV therapy for the treatment of unresectable cutaneous, subcutaneous, & nodal lesions in patients with melanoma Modified from Haitz et al. (2020). Journal of the American Academy of Dermatology 83(1):189-196. recurrent after initial surgery. Videos on OV therapy: https://www.youtube.com/watch?v=C8-OFTwuALE https://youtu.be/zwlCkVnUgWQ 21 Adoptive T Cell Therapy  Transfer of tumor-specific T cells: a. TIL therapy: tumor-infiltrating lymphocytes (TILs) are isolated from the tumor, cultured with IL-2, then infused back into the patient. b. Genetically-engineered T cells: T cells are isolated from the blood, genetically modified with a tumor- specific TCR or CAR, cultured with IL-2, then infused back into the patient. TCR = T cell receptor CAR = chimeric antigen receptor https://link.springer.com/article/10.1007/s00281-018-0703-z/figures/1 https://www.frontiersin.org/journals/oncology/articles/ 10.3389/fonc.2020.01243/full 22 Clinical Application: CAR-T Cell Therapy  KymriahTM (tisagenlecleucel) was the first FDA-approved CAR-T cell therapy for the treatment for some forms of B cell leukemia.  Kymriah is composed of anti- CD19 scFV + CD3 + a costimulator (FYI: Kymriah uses 4- 1BB which is analogous to CD28)  The CAR binds directly to CD19 on the B cell! https://ardigen.com/future-perspectives-for-car-t-cell-therapies/ Shannon L. Maude et al. Blood 2015;125:4017-4023  CARs allow for MHC-independent antigen recognition Videos on CAR-T cell therapy https://www.youtube.com/watch?v=OadAW99s4Ik and activation of T cells! https://youtu.be/tYbREMOveWk 23 Antibody-Based Therapies A. Immune checkpoint inhibitors: blocking T cell inhibitory pathways  T cells express inhibitory receptors to limit (stop) immune responses after activation 1. CTLA-4: binds B7 expressed by APCs to inhibit T cell activation in the secondary lymphatics 2. PD-1: binds PD-L1/L2 expressed by many cells to inhibit effector T cell function in the periphery http://www.nature.com/nrc/ journal/v12/n4/fig_tab/nrc3 239_F3.html 24 Antibody-Based Therapies A. Immune checkpoint inhibitors: blocking T cell inhibitory pathways  Immune checkpoint inhibitors are antibodies that block inhibitory receptors/ligands; stimulate antitumor responses by enhancing T cell activation - i.e., reduces the inhibition of T cells.  These therapies enhance the patient’s own immune response to tumors! Clinical Application: several monoclonal antibodies are on the market. Anti-CTLA4 mAbs: Ipilimumab (Yervoy®) Anti-PD-1 mAbs: Pembrolizumab (Keytruda) Nivolumab (Opdivo) Anti-PD-L1 mAbs: Atezolizumab (Tecentriq®) Optional video on checkpoint inhibitors: https://www.youtube.com/watch?v=v9NBUeU3PG0 25 Antibody-Based Therapies B. Anti-tumor monoclonal antibodies (review L19). These monoclonal antibodies function to:  Induce antibody-dependent cellular cytotoxicity (ADCC)  Activate complement  Block growth or activation signals  Deliver radiation, toxins, or chemotherapy drugs to tumor cells (immunoconjugates)  Many monoclonal antibodies have been developed for treating various cancers. https://www.researchgate.net/figure/a-b-Mechanisms-of-anti-tumor- activity-by-antibodies-Monoclonal-antibodies-recognize_fig11_24376712 26 Summary  TSA vs. TAA antigens – know the examples discussed in class and how they are classified  TSA = tumor-specific antigens (mutations; antigens from oncogenic viruses)  TAA = tumor-associated genes (overexpression or aberrant expression of normal self proteins)  Immune mechanisms for tumor rejection – know how each functions in elimination of tumors  CTLs = principal mechanism for eradication of tumor cells!  Antibodies  NK cells  Macrophages  Tumor immunoediting: immune cell killing selects for cancers that have reduced immunogenicity  Tumor evasion – know the three mechanisms discussed (see slide 19)  Immunotherapies: be able to describe the mechanism of action of each of these therapies:  Therapeutic cancer vaccines  Oncolytic viral therapy  Adoptive T cell therapies  Immune checkpoint inhibitors 27  Midwestern Wellness Support Professional school can be difficult, we have resources Midwestern University Student Counseling Academic Live Care Please email to request an appointment: https://midwestern.myahpcare.com/telehealth [email protected] To register: Use your midwestern.edu email Service Key: ALC In the Moment Mental Health Counseling When making appointments, there will be a 24/7 live telephonic counseling when you need to speak to price listed. 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