Melanoma and the “Magic Bullet” (Monoclonal Antibodies)
Author:Jim Breitfeller
This paper is dedicated to Leanne Schmall A patient who lost her battle with the Beast, Melanoma.
I. Introduction:
Paul Ehrlich - (March, 14 1854 –August, 20 1915)
Dr. Ehrlich can be called the “Father of Modern Immunology”. He was a German scientist in the fields of hematology, immunology, and chemotherapy, and Nobel laureate. He is noted for his research in autoimmunity, calling it "horror autotoxicus". He coined the term "chemotherapy" and popularized the concept of a "magic bullet". He is credited with the first observation of the blood-brain barrier and the development of the first antibacterial drug in modern medicine.1
The Magic Bullet concept was base on selective targeting a disease with a toxin/agent to kill off the disease without effecting the rest of the body. Using this concept in 1909, he and his student came up with a treatment for Syphilis.
One of his other works he is also famous for was called the “Side-Chain Theory” This proposed theory explaining the immune response in living cells.
The concept of a "magic bullet" was fully realized with the invention of monoclonal antibodies.
Today, we have a better understanding of our immune system but are still pushing back the frontier in this area, as we try to decode the Mystery of Melanoma Cancer.
II. The Immune System:
Before we begin to talk about the treatment of Melanoma, we need to gain some basic knowledge on the subject matter.
In the late 1960’s, a book, was published by F.M. Burnet, “Cellular Immunology and Self and Not-Self” It proposed that Immune system could detect and destroy tumors, a cancer immunosurveillance.
The key to a healthy immune system is that the immune system is able to recognize the body (Itself) from the (non-self) the foreign invaders, the cancer cells – tumors.
In the absence of ongoing inflammatory and immune responses, Dendritic Cells (DC’s) patrol through the blood, the adjacent tissues, lymph and lymphoid organs.
Dendritic cells (DCs) are immune cells and form part of our immune system. In the adjacent tissues, Dendritic Cells capture self and non-self antigens via specific receptors. Anything that can trigger this immune response is called an antigen. Antigens can be microbe , apart of a microbe, even a cell or tissue from transplant victims. Sometimes our immune system mistakes itself as non-self causing a response as an autoimmune response. Some examples of Autoimmune Diseases are Rheumatoid Arthritis, Multiple Sclerosis, and Lupus etc.1
Signals from pathogens or pathogen-induced tissue damage, often referred to as "danger
signals", induce Dendritic cells to enter a developmental program, called "maturation", which transforms Dendritic cells (DCs )into efficient antigen-presenting cells (APCs) and T-cell activators. Danger signals are generated when receptors on DCs recognizes an encounter with bacteria, bacterial products viruses, viral products ,cytokines, molecules on T-cells (CD40L) and molecules derived from self cells (tumor cell lysates). These are Tumor cells that have been destroyed and broken into pieces. Once they have come into contact with a presentable antigen, they become activated into mature dendritic cells and begin to migrate to the lymph node. Here they act as antigen-presenting cells: they activate T helper cells and T killer cells as well as B-cells by presenting them with antigens derived from the pathogen, alongside non-antigen specific costimulatory signals.1
T-helper cells (also known as effector T cells or Th cells) are a sub-group of lymphocytes (a type of white blood cell or leukocyte) that play an important role in establishing and maximizing the capabilities of the immune system.1
A cytotoxic T cell (also known as TC, CTL, T-Killer cell, cytolytic T cell, CD8+ T-cells or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) that are capable of inducing the death of infected cells or tumor cells; they kill cells that are infected with viruses (or other pathogens), or are otherwise damaged or dysfunctional.1
B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells). The principal functions of B cells are to make antibodies against antigens, perform the role of Antigen Presenting Cells (APCs) and eventually develop into memory B cells after activation by antigen interaction. B cells are an essential component of the adaptive immune system. The adaptive immune system is composed of highly specialized, system.
Mast cells/mastocyte is a reside in several types of tissues and contains many granules rich in histamine and heparin. It is best known for their role in allergy and hypersensitivity allergic reactions. Mast cells play an important protective role as well, being intimately involved in wound healing and defense against pathogens and processes that eliminate or prevent pathogenic problems1
Eosinophil granulocytes, usually called are eosinophils, are white blood cells that are one of the immune system components responsible for combating infection. Along with mast cells, eosinophils also control mechanisms associated with allergy and asthma. They are granulocytes that develop during Haematopoiesis in the bone marrow before migrating into blood.1
Hematopoiesis
Source: Wikipedia
All immune cells begin as immature stem cells in the bone marrow. They respond to different cytokines and other signals to grow into specific immune cell types, such as T cells, B cells.
Cytokines
Components of the immune system communicate with one another by exchanging chemical messengers called cytokines. These proteins are secreted by cells and act on other cells to coordinate an appropriate immune response. Cytokines include a diverse assortment of interleukins, interferons, and growth factors.1
Some cytokines are chemical switches that turn certain immune cell types on and off.
One cytokine, interleukin 2 (IL-2), triggers the immune system to produce T cells.
T-Cell final development occurs in the Thymus. The thymus is a multi-lobed organ that is composed of a cortical and medullary area. During the T-Cell development, the cell moves through the different lobes due to the different microenvironments. Most of the cells that enter the thymus never make out alive to become a mature Naïve T-cell. A naive T cell or Th0 cell is a T cell that has differentiated in bone marrow, and successfully undergone the positive and negative processes of central selection in the thymus. In the Negative process, the T cell goes through a rigorous selection to self antigen tolarence before it is released into circulation. Once in circulation, the cells are able to respond to novel pathogens that the immune system has not yet encountered.1
The NaiveCD4 + the helper T cell, when activated, the Helper T –cell secretes mostly IL-2 which promotes growth and proliferation, and activation of T-cells, helper T cells and Natural Killer Cells. Once the helper cells mulitply, they start secreting other cytokines base on their costimulatory signals., concentration of antigen, and exposure to their microenviroment. This attracts more immune cells and the assault on the foreign invader begins.1
Regulatory T-cells (Tregs) (suppressor T cells) are a specialized subpopulation of T cells that act to suppress activation of the immune system and thereby maintain immune system homeostasis and tolerance to self-antigens. Regulatory T cells play an important role in preventing autoimmunity by suppressing the response of other T-cells to self- and other antigens. Several types of Tregs have been identified, including both CD4+ and CD8+ expressing subsets. One of the best characterized subsets, natural Tregs express both CD4 and high levels of CD25. Anergic cells can act as regulatory T cells by competing at the sites of antigen presentation and adsorbing out stimulatory cytokines such as IL-2. (Lack of IL-2/costimulation)1
III. Immunomogy History:
In 1980, Dr. Steven A. Roesnberg and colleagues discovered novel novel method for killing metastatic cancer cells. They took lymphoid cells and exposed them to interluekin-2 (IL-2).These cells were able to lyse the tumor cells and kill them. The were a different population than the Natural Killer cells. They coined the term “Lymphokine-activated killer cells” (LAK) for short. However, LAK cells with high dose IL-2 were not shown to be effective in a randomized clinical trial when compared to IL-2 alone2
The Cells that were cultured from tumor infiltrating lymphocytes (TIL), had a better response to the tumors. We now come to know this therapy as Adaptive Cell Transfer Therapy.
During those Trials, Rosenberg and colleagues saw a correlation between younger cultures and where the originals TILs were harvested. The younger, the better the response was with the patient. TILs that were harvested from the lymph node did not respond as much, indicating that specific location plays a role in the overall scheme of things. One must also note that Dr. Rosenberg’s Patients are a certain genotype (HLA-A2 positive).
In 1988, a research paper came out authored by Dr. Kyogo Itoh , Platsoucas,and Balch entitled: “Autologous Tumor Specific Cytotoxic Lymphocytes in the Infiltrate of Human Metastatic Melanomas”4 Activation by Interleukin 2 and Autologous Tumor Cells, and Involvement of the T Cell Receptor.
In the report all twelve Metastatic Melanoma tumor cell suspensions activated by IL-2 , TILs were present to a large degree. This confirmed Rosenberg’s theory earlier. The TIL cell count increased to a maximum propagation in about 43 days. Tumors cells that were cultured with the TILs and the IL-2 were complete killed off. Lysing appeared five days into the experiment. The cytotoxic activity lasted for at least 59 days. In the control, without IL-2, the TILs eventually die off leaving the tumors cells enacted. These experiments and results lead to the Rosenberg’s trials.
T Cells Mobilized Graphics
Adapted from Understanding the Immune System How It Works NIH Publication No. 03–5423
In 1992, adoptive transfer of TILs in combination with IL-2 resulted in tumor regressions in approximately 30% of melanoma patients (Rosenberg SA), suggesting that the
immune system can play a critical role in the elimination of malignant cells.
Now with a basic understanding of the immune system, we need to know how the tumor escapes detection and destruction.
In a 1994 article entitled "Tolerance, Danger and the Extended Family", Dr. Polly Matzinger, layed out the idea that antigen-presenting cells (APC) respond to "danger signals" - most notably from cells undergoing injury. The immune system does not necessarily respond only to what is foreign but to anything that is dangerous. The danger model is based on the existence of the so-called second signal, in addition to the first signal directed at T-cells. The first signal comes from specific recognition of antigenic peptides presented within MHC molecules (APC). The second signal is either
mediated through co-stimulatory molecules on APCs or delivered by T-helper
cells.
The presence or absence of the second signal determines immune responsiveness or tolerance.
Table 1.)
The main rules to generate an immune response or tolerant stateCell Type / Absence of Second Signal / Second Signal
Naïve T-cells / undergo apoptosis / only by Dendritic cells (DCs)
Memory T-cells / undergo apoptosis / all APCs, monocytes, macrophages, B-cells or DCs
B-cells / undergo apoptosis / only by memory/effector T-cells
Effector T and B-cells / perform functions after antigen recognition regardless / undergo apoptosis or revert to a resting state after a reasonably short period of time
Source: T-Cell Stimulation by Melanoma RNA-Pulsed Dendritic Cells3
The Danger Model is not universally accepted . Some immunologists, following Janeway's ideas (1989) believe that the immune response is based upon by evolutionarily forces of "pattern recognition receptors". So what happens if it is a combination of both of the therories?
By trying to manipulate the immune system into specifically recognizing and killing tumor cells, there is a thin line between breaking tolerance and inducing autoimmune disease can be easily crossed. This must be taken into account when protocols for Clinical Trials are formulated. Tumor cells have a number of other direct strategies for hiding from or fighting against an immune response. Most solid tumor cells are able to hide from T-cells because they grow out of reach of secondary lymphoid organs, so naive T-cells remain unaware of the tumor's existence. Tumors also secrete proteins/peptides that act as mediators between the tumor and the host (body) communicating in the tumor microenvironment. This somehow (may block the receptors or the signals) allowing the tumor to go undetected by the immune system.
IV. Lymphatic System of the Immune System
Source: http://cksinfo.com/medicine/anatomy/page2.html
The Dendritic cells (DCs) can be described as the most potent antigen presenting cells (APCs). They are also the only cells capable of activating naïve T-cells and, thereby, of initiating adaptive immune responses. In addition to up-regulation of antigen-presenting and co-stimulatory molecules, maturation includes enhancing the ability of DCs to migrate out of the tissues and into secondary lymphoid organs, where interactions with T-cells take place.
IV. Immunosurveillance
Robert Schreiber’s group found evidence for immunosurveillance.
The “three Es hypothesis” comes from this idea, and has been proposed by Schreiber and colleagues in 2003.5 The idea is that immunosurveillance is one phase of a more comprehensive process immunoediting which can be broken up into three component phases: elimination, equilibrium and escape. In the elimination phase, immune cells recognize and eliminate the altered cells (Tumor Cells). Generally, this is sufficient. After, or simultaneous with, the elimination phase, is the equilibrium phase in which the tumor cells and the immune system exist in equilibrium of inaction: the tumor doesn’t grow and the immune system doesn’t attack it. This can continue for years, and the individual remains cancer free. Then, some tumors escape. This last phase, Escape Phase occurs when a tumor mutates sufficiently to evade elimination by the immune system and grows out. The interesting thing that Schreiber and colleagues propose is that the tumor by the selective process over time during the elimination and equilibrium phases, evolves until it can go undetected and escapes: that when immune system see the tumor cells, the immune system does not get a danger signal and the tumor cells proliferate. The result is cancer.