is a form of cancer treatment that uses the power of the body’s own immune system to prevent, control, and eliminate cancer.
Immunotherapy can:
Educate the immune system to recognize and attack specific cancer cells
Boost immune cells to help them eliminate cancer
Provide the body with additional components to enhance the immune response
Cancer immunotherapy comes in a variety of forms, including targeted antibodies, cancer vaccines, adoptive cell transfer, tumor-infecting viruses, checkpoint inhibitors, cytokines, and adjuvants. Immunotherapies are a form of biotherapy (also called biologic therapy or biological response modifier (BRM) therapy) because they use materials from living organisms to fight disease. Some immunotherapy treatments use genetic engineering to enhance immune cells’ cancer-fighting capabilities and may be referred to as gene therapies. Many immunotherapy treatments for preventing, managing, or treating different cancers can also be used in combination with surgery, chemotherapy, radiation, or targeted therapies to improve their effectiveness.
You can get more information from the website:cancerresearch.org and immuno-oncology and the latest trends in immunotherapy video
OVERVIEW
The human body has many natural immune mechanisms for cancer cell recognition and elimination. Normal function of these effector mechanisms helps prevent tumor growth and metastasis. Unfortunately, counter mechanisms can also be established that allow malignant cells to evade this destruction by the immune system.
The discovery and development of immuno-oncology therapy represents a milestone in the treatment of cancer. Unlike traditional therapies that focus on attacking the tumor cells themselves, immuno-oncology is a revolutionary treatment approach which focuses on remobilizing the patient's own immune system to recognize and eliminate cancer cells.
Normal Immune Response There are two main components of the immune response: innate and adaptive immunity. These are complementary networks of self-defense against non-self, foreign threats to the human body.
Innate immune response
An antigen-independent response that is immediate and has no immunologic memory
Natural killer (NK) cells, dendritic cells (DCs), innate lymphoid cells (ILCs), and phagocytes (macrophages and neutrophils) are the primary innate immune cell types.
NK cells can elicit a cytolytic response to stressed cells such as tumor and virus infected cells.
Macrophages are primarily responsible for phagocytosis of foreign organisms and other target cells including tumor cells.
Adaptive immune response
An antigen-dependent and antigen-specific response with the capacity for immunologic memory
T cells and B cells are the primary adaptive immune cell types.
Macrophages, B cells, and DCs activate T cells via antigen cross presentation (AP).1
Unlike T cells, B cells can recognize free antigen directly, without the need for antigen presenting cells (APCs).
B cells are converted to plasma cells to kill organisms via secreted antibodies, which is referred to as antibody-dependent cell-mediated cytotoxicity.1
Role of the Immune System in Cancer
Tumor development can potentially be controlled by cytotoxic innate and adaptive immune cells; however, as the tumor develops from neoplastic tissue to clinically detectable tumors, cancer cells evolve different mechanisms that mimic peripheral immune tolerance in order to avoid tumoricidal attack. The innate and adaptive immune response has the ability to detect and eliminate these early tumor cells that are no longer recognized as normal self (abnormal) via tumor antigens.
Potential malfunctions in immunity leading to tumor progression include:6
Failure of tumor antigen recognition
DCs and T cells may treat antigens as self rather than foreign
T cells may not properly localize to tumors
T cells may not effectively infiltrate the tumor microenvironment
Factors in the tumor microenvironment might suppress effector cells
Steps in the Cancer Immunity Cycle / Opportunities for Anti-Cancer Therapeutics
Release of Cancer Antigens
Damage- or Pathogen- associated molecular pattern (DAMP/PAMP) molecules released from microbes or infected, stressed or dying cells (including cancer cells) activate innate immune cells which are capable of rapidly responding to the threat.
These same danger signals activate and mature DCs, the first step in the adaptive immune response.
Cancer Antigen Presentation
Antigen presentation to T cells by activated and mature DCs or APCs.
Mature DCs capture and process proteins from the threat (antigens for the adaptive immune system to recognize) and migrate to draining lymph nodes.
Major histocompatibility complex (MHC) proteins on the surface of mature DCs present the captured antigens to the T-cell receptor (TCR) on T cells.
T-cells secrete other cytokines to further control the immune response and activate B-cells that multiply and mature into antibody-producing plasma cells.
Priming and Activation of T Cells
If an immunogenic stimulus is present, effector T-cell responses against the tumor-specific antigens are activated.
In the absence of a stimulus, immature DCs will present the antigens to T cells and induce T-cell tolerance.
Trafficking of T Cells to Tumors
The trafficking of activated T cells and other immune cells to the tumor is a highly regulated and dynamic process, involving a series of distinct processes, which include rolling, adhesion, extravasation, and chemotaxis.
Overcoming barriers that restrict T-cell infiltration to the tumor site is critical.
Infiltration of T Cells into Tumors
T-cells, as well as macrophages and monocytes, must infiltrate the tumor microenvironment.
Recognition of Cancer Cells by T cells
The T-cell receptor (TCR) specifically recognizes and binds to the corresponding tumor antigen.
Response may be reduced if the cancer cell:
Has lost expression of the tumor antigen
Has downregulated their expression of MHC class I molecules
Expresses surface molecules (ie, PD-L1) that engage receptors on activated T cells (ie, PD-1), leading to T-cell exhaustion
Killing of Cancer Cells
Killing of the cancer cell releases additional tumor-associated antigens.
Stimulators include IFN-γ and T-cell granule content.
Inhibitors (checkpoints) include PD-1/PDL-1/B7.1, BTLA, VISTA, LAG3, TIM-3, TIGIT, IDO, Arginase, MICA:MICB, B7-H4, and TGFβ.
Immunosuppression and Immunotherapy Resistance
For tumors to grow, mechanisms must be in place to evade the immune response that might recognize and eliminate the tumor cells.
Suppression, evasion, and appropriation of natural immune effector mechanisms for tumor detection and elimination contribute to tumor growth and metastasis.
Suppression of these mechanisms prevents the natural antitumor immune response.
Evasion of these mechanisms occurs via changes in the tumor cells that prevent recognition by immune cells, such as
Loss of cell surface tumor antigens
Loss of sensitivity to complement, T-cell, or natural killer (NK)-cell induced lysis
Appropriation of normal immune functions occurs within the tumor microenvironment
Many tumor-cell–intrinsic and –extrinsic factors contribute to immune evasion and immuno-oncology therapy resistance.
Intrinsic Mechanisms of Resistance
Intrinsic mechanisms are those that involve the tumor cell itself.
Mechanisms of primary resistance include alteration of signaling pathways (ie, JAK, MAPK, PIK3, WNT), lack or loss of tumor-specific antigens, alteration in antigen-presenting machinery, constitutive PD-L1 expression, and loss of human leukocyte antigen (HLA) expression.
Mechanisms of acquired resistance include loss of target antigen or HLA expression at recurrence, altered IFN signaling, loss of T-cell functionality, and loss of sensitivity to complement-induced, T cell-induced, or natural killer (NK) cell-induced lysis.
Extrinsic Mechanisms of Resistance
Extrinsic mechanisms involve components of the tumor microenvironment other than the tumor cell.
Extrinsic mechanisms of primary and adaptive resistance to immunotherapy include absence of T cells, inhibitory immune checkpoints, and immunosuppressive cells.
Therapeutic Potential The introduction of immune checkpoint inhibitors in oncology has increased the potential for durable responses and shifted therapeutic attention to extending the tail of the survival curve. However, not all patients respond to currently available immunotherapy agents (ie, PD-1/PD-L1 and CTLA-4 antibodies). The potential to address a range of additional immune mechanisms of resistance and to activate an immune response at additional points along the immune cycle makes continued research in immuno-oncology vital to the evolution of cancer therapy. Novel immuno-oncology targets and pathways include OX40 and CD40. Due to the multiple mechanisms of immune-suppression, combination immuno-oncology regimens may also help address patient needs. One additional emerging anti-tumor strategy utilizing the immune system is the concept of T-cell redirecting bispecific antibodies (TRBAs). These types of bispecific antibodies can simultaneously bind to a target on T cells and a target on malignant cells, inducing activation and cytotoxic activity of T cells enabling tumor cell death. The ongoing research into immuno-oncology therapies is opening up exciting new avenues, exemplified by the impressive therapeutic response observed with checkpoint inhibitors targeting PD-1/L1 and CTLA-4.
