Cell biology and Immune Response to cancer

Resisting cell death

(LOSS of FUNCTION OF BRAKES) mutations in tumor suppressors render tumor-suppressing proteins inactive thus preventing regulation via apoptosis

Tumoricidal cells

- NK cells - Cytotoxic T cells (CD8+) - macrophages - neutrophils - CD4+ T cells----> B cells - APCs (

Tumor-promoting inflammation

- Provides a milieu favoring cell proliferation - Increased free radicals promote DNA damage - Cytokines in chronic inflammation promote angiogenesis Increase metastatic potential - increased angiogenesis= increased immune cells in the area - tumor does not want to be recognized by immune cells

Evasion of growth suppressors

- cancers grow in clumps - normal inhibitory molecules grow in a flat layer, but cancer cells will layer on top of each other because they are insensitive to inhibitory signals

HLA

Human Leukocyte Antigen. Same as MHC.

Tumor-specific antigens (TSAs)

protein on the membrane of cancer cells that distinguishes the malignant cell from a benign cell of the same tissue type

CD4+ helper T cells

stimulate or "help" B cells to make antibodies in repsonse to antigenic challenge also stimulate CD8+ cells

Explain ways in which dominant and recessive syndromes are associated with cancer.

- A lot of inherited mutations are in DNA repair genes - Autosomal dominant inheritance pattern because you only need to inherit one copy because it is easy to acquire the second mutation via exposure or mutation over time

Tumor escape mechanisms

- high mutation rate - loss of function mutations in tumor suppressor genes prevent cells from undergoing apoptosis even if the signal is received (BcL2) - increased survival because tumor cells do not need a favorable extracellular environment to proliferate (STAT3) - express suppressive cytokines (IL6, IL10, TGF-beta, GM-CSF) that block the immune system from killing tumor cells - express immune check pionts to block T cells - reduced tumor antigens - reduce immune function via PGE2 - attract suppressive cells like Treg and IL-10 secreting B cells this is amplified by transformed fibroblasts that release CCL2 and CXCL2

Evading immune surveillance and destruction

- immune surveillance is happening all the time and it must work because not everyone gets cancer - It is now evident that tumors engineer microenvironments to evade immune surveillance and attack, particularly by modulating certain immune-checkpoint pathways. - For example upregulation of PD-L1 may allow cancers to evade the host immune system.

What happens during escape phase?

- once all of the tumor cells that release highly immunogenic antigens are eliminated, the only ones left are the ones producing poorly immunogenic tumor antigens - immune response is thus dampened - less activation of APCs therefore less activation of T cells and fewer tumor cells are destroyed - tumor cells also overexpress immune checkpoint proteins and block T cells from killing it

what happens during the elimination phase?

- tumor cells release highly immunogenic antigens - antigens travel to and activate APC (macrophages, dendritic cells, B cells) - APCs activate NK cells that migrate to the tumor and release granzyme B that lyses more tumor cells releasing more antigens and feeding the loop - APCs also activate T cells by presenting tumor antigens on MHC II - activated T cells migrate to the tumor and release proinflammatory cytokines and proliferate to kill tumor cells

tumor promoting cells

- tumors will recruit these cells by secreting chemokines - regulatory T-Cells - tumor associated macrophages and neutrophils - immature dendritic cells

PI3K

-PI3K -> PIP3 ->Akt/PKB or Rho-GEFs -results in inhibition of Bad, protein synthesis, cell proliferation and cell cycle progression

Chediak-Higashi syndrome

-genetic defect causes impairment of NK cells and an associated increase in certain types of cancer

cancer immunoediting

the ability of the immune system to shape and mold the immunogenic properties of tumor cells in a fashion that ultimately leads to the *Darwinian selection of subclones* that are best able to avoid immune elimination.

Warburg effect

-use of glycolysis under normal oxygen conditions (aerobic glycolysis) -allows products of glycolysis to be used for rapid cell growth -activated by oncogenes and mutant tumor suppressors

Criteria for Lynch Syndrome

1. At least 3 relatives are affected by histologically verified CRC or cancer of the endometrium, small bowel or urinary tract; at least one of them is a first degree relative of the other two 2. At least 2 of the above persons are first degree relatives from two different generations 3. At least 1 of the above persons has cancer diagnosed at age under 50 years

Immunoediting

1. elimination 2. equilibrium 3. escape

stages of tumor growth and metastasis

1. single cell develops altered growth properties which could be corrected by DNA repair 2. altered cell proliferates forming a mass of localized tumor cells, or benign tumor 3. tumor cells become more invasive spreading to underlying tissue (now malignant) 4. malignant tumor metastasizes by dislodging from the tumor and spreading to other sites in the body by blood or lymph

Hallmarks of Cancer

1. sustaining proliferative signaling 2. reprogramming energy metabolism 3. resisting apoptosis 4. genomic instability 5. inducing angiogenesis 6. tumor-promoting inflammation 7. enabling replicative immortality 8. evading immune destruction 9. Evading growth suppressors ALL CONTRIBUTING TO: invasion and metastasis

Transformation

the change that a normal cells undergoes as it becomes malignant which is normally mediated by DNA alterations or the uptake and incorporation of foreign DNA into the genome

Explain how the downregulation and subsequently decreased expression of Class I MHC on cancerous cells influences an immune response

A low MHC class I level favours NK cells as effectors, whereas a high level of MHC class I favours T cells as effectors. MHC-I presents endogenous antigens, a process important for reporting intracellular changes, for example caused by viral infections or malignant transformation, to the immune system in order to initiate a CD8+ T-cell response

PD-L1

A protein created by the cancer cells to turn off CTLs

dentritic cells

APCs that are the most potent stimulators of T cell responses Process and present tumor antigens to T cells

AFP (alpha-fetoprotein)

Alpha-fetoprotein (AFP) is a protein produced primarily by the liver in a developing baby (fetus). AFP is produced whenever liver cells are regenerating. With chronic liver diseases, such as hepatitis and cirrhosis, AFP may be chronically elevated. Very high concentrations of AFP may be produced by certain tumors. This characteristic makes the AFP test useful as a tumor marker. Elevated serum concentrations of AFP have been principally associated with primary liver cell cancer (82 percent) and with ovarian and testicular tumors which contain yolk sac tumor cell elements

indirect immunofluorescence

An immunofluorescent diagnostic technique in which the fluorochrome is not attached to the primary antibody that recognises the target antigen, but to a secondary antibody that binds the primary antibody.

Double strand break repair

Broken DNA initiates homologous recombination between sister or nonsister chromatids that results in rejoining of the broken DNA ends.

Immunotherapy in cancer

Cancer immunotherapy is a strategy that harnesses the body's immune system to combat tumors Many oncologists say those efforts are paying off, as two different techniques show signs of helping some patients. One involves antibodies that release a brake on T cells, giving them the power to tackle tumors. Another involves genetically modifying an individual's T cells outside the body to make them better able to target cancer, and then reinfusing them so they can do just that.

Genes associated with cancer control, cell proliferation, and survival

Category I Category II Category III

Discuss the role of genetic mutations in the progression of cancer from an isolated tumor to invasive and metastatic tumor

Decreased cell-cell adhesion Degradation of basement membrane by MMPs Intravasation Migration Epithelial to mesenchymal transition Intravasation Extravasation (requires adherence to endothelium) Re-Colonization (often mesenchymal to epithelial transition)

Epithelial markers

E-cadherin Claudins Cytokeratins

Rb

tumor suppressor, which plays a pivotal role in the negative control of the cell cycle and in tumor progression. It has been shown that Rb protein (pRb) is responsible for a major G1 checkpoint, blocking S-phase entry and cell growth

mutation in the promoter of p21

tumor supressor no halt at G1 to check and fix DNA

Claudins

Form the backbone of tight junctions, charged amino acids in extracellular loop, pores allow passage of certain ions, scaffold binding site claudin-1 disease recurrence in colorectal cancer; alteration in claudins are an early event in esophageal adenocarcinoma

Describe the mechanisms by which somatic cells are recognized by one's own immune system.

Human leukocyte antigens (HLA) are a group of identification molecules located on the surface of all cells in a combination that is almost unique for each person, thereby enabling the body to distinguish self from nonself.

IL-6 in cancer

IL-6 acts intrinsically on tumor cells through numerous downstream mediators to support cancer cell proliferation, survival, and metastatic dissemination. Moreover, IL-6 can act extrinsically on other cells within the complex tumor microenvironment to sustain a pro-tumor milieu by supporting angiogenesis and tumor evasion of immune surveillance

escape

tumor variants evade and overwhelm the immune system and become clinically detectable

CD8+ T lymphocytes (cytotoxic T cells)

tumors have shown to induce tumor-specific CTLs that recognize tumor antigens presented by MHC I on tumor cells

TGF-beta in cancer

In early stages of cancer, TGF-β exhibits tumor suppressive effects by inhibiting cell cycle progression and promoting apoptosis. However, in late stages TGF-β exerts tumor promoting effects, increasing tumor invasiveness, and metastasis

lymphoma

Lymphoma is a cancer of the lymphatic system, which is part of the body's germ-fighting network. The lymphatic system includes the lymph nodes (lymph glands), spleen, thymus gland and bone marrow. Lymphoma can affect all those areas as well as other organs throughout the body

immune checkpoints

Molecules that either stimulate or inhibit T cells - Critical for maintaining self-tolerance and modulating duration/amplitude of immune responses to minimize collateral damage

mesenchymal markers

N- cadherin Snail-1 Zeb-1

N-cadherin

N-cadherin is a hallmark of epithelial-to-mesenchymal transition, resulting in the acquisition of an aggressive tumour phenotype. EMT is the loss of epithelial cadherin (E-cadherin) expression and the concomitant up-regulation or de novo expression of neural cadherin (N-cadherin). This so-called "cadherin switch" is associated with increased migratory and invasive behaviour

EFGR

The epidermal growth factor receptor protein (TKR) is involved in cell signaling pathways that control cell division and survival.

p21 gene

turned on by p53; the products of this gene halt the cell cycle by binding to cdk's which allows time for DNA repair

why do oncofetal antigens produce an immune response?

Often oncofetal antigens are immunogenic since they are not expressed widely in the adult animals and the immune system is not tolerant and they can elicit self-immunity under some circumstances.

point mutation in KRAS making it constitutively active

Oncogene if always on KRAS contributes to anti-apoptosis, proliferation, angiogenesis, and metastasis

Translocation of BCR-ABL

Oncogene translocation of BCR to ABL to make 1 protein that turns off apoptosis

matrix metalloproteins (MMPs)

Secreted by macrophages during the proliferative phase of wound healing. Degrade and remodel extracellular matrix proteins (e.g. collagen and fibrin) at the site of injury . To date, 23 MMP genes have been identified in humans and many are implicated in cancer. ECM degradation by MMPs not only enhances tumour invasion, but also affects tumour cell behaviour and leads to cancer progression

Deregulation of metabolism

The metabolic profile observed in cancer cells often includes increased consumption of glucose and glutamine, increased glycolysis, changes in the use of metabolic enzyme isoforms, and increased secretion of lactate.

genetic changes during cancer development

the induction of cancer is a multistep process of clonal evolution driven by a series of somatic mutations that progressively convert the normal cell into a cancerous cell ex. -Morphologic stages of colon cancer have been correlated with a sequence of gene changes involving the inactivation or loss of three tumor-suppressor genes (APC, DCC, p53) and the activation of one cellular proliferation oncogene (K-ras)

p53

This tumor suppressor gene causes cell cycle arrest in G1, providing time for DNA repair. If repair is successful, cells re-enter the cycle. If unsuccessful, apoptosis

NK cells

Tumor cells that try to evade recognition of neo-antigens by downregulating MHC Class I expression are attacked and killed by NK cells recognize and destroy altered self cells- detect decreased levels of MHC or target cells tagged with antibodies

Antibody-dependent cell-mediated cytotoxicity (ADCC)

antibodies attached to target cell cause destruction by macrophages, eosinophils, and NK cells NK cells and macrophages express FcRs that enable them to bind antibodies bound to tumor cells

Angiogenesis in cancer

Tumors secrete growth factors that stimulate new vessel growth which fuels and promotes faster growth. VEGF

Oncofetal antigens

Type of tumor antigen that are found on both the surfaces and the inside of cancer and fetal cells. Means the cell has shifted to an immature metabolic pathway. Can be used as tumor markers in order to indicate tumor recurrence. Not 100% reliable. ex. CEA, AFP

replicative immortality

Upregulation of telomerase --> add more telomeric DNA to the ends of chromosomes --> unlimited replicative potential --> cellular immortality Too low levels --> chromosomal instability --> Increase chance of cancer

TSA vs TAAs

While tumor-specific antigens (TSA) are exclusively expressed in tumor cells, tumor-associated antigens (TAA) are present on not only tumor cells but also some normal cells.

Zeb-1

ZEB1 downregulates E-cadherin and induces epithelial to mesenchymal transition in breast and other carcinomas. ZEB1 contributes to bone-specific metastasis of breast carcinomas by inactivating BMP signaling through the induction of the expression of BMP-inhibitors.

equillibrium

a balance is reached when tumor cell proliferation equals the death caused by immunity cancer cells maintained chronically or immunologically are sculpted to produce tumor variability - tumor does not grow and most of the time remains subclinical

Leukemia

a malignant progressive disease in which the bone marrow and other blood-forming organs produce increased numbers of immature or abnormal leukocytes. These suppress the production of normal blood cells, leading to anemia and other symptoms

CAR-T cells

a specific type of adaptive immune cell, T cells, are removed from the patients blood and modified in the laboratory to help them fight cancer these modified cells are then transfused back into the patient where they target and destroy cancer

B cells

adaptive immune cells that is an APC and produces antibodies which target cancer cells for ADCC

Lynch syndrome

an autosomal dominant disease caused by abnormal nucleotide mismatch repair. Mutations in MSH2 (codes for MutS) and MLH1 (MutL) are most common.

IL-10

anti-inflammatory cytokine that is secreted by B cells and protects tumor cells by suppressing other immune cells immunosuppressive cytokine produced by tumor to reduce DC activity and inhibit T cell activation

Tumor-associated antigens (TAAs)

antigens found with elevated levels on tumor cells, but are also expressed at lower levels on healthy cells

transcriptional heterogeneity

cancer cells in the same clump are not all the same

E-cadherin

cell adhesion molecule that plays an important role in contact-mediated growth inhibition of epithelial cells; also binds and sequesters β-catenin, a signaling protein that functions in the WNT pathway Germline loss-of-function mutations in the E-cadherin gene (CDH1) associated with autosomal dominant familial gastric carcinoma Loss of expression seen in many sporadic carcinomas; associated with loss of contact inhibition, loss of cohesiveness, increased invasiveness, and increased WNT signaling

Sustaining proliferative signaling

cells do not require external signals to continue growing and dividing GAS ON - constitutively on proteins at anywhere in the cycle - too much ligand binding to the receptor - too much receptor leading to amplification of the signal All this leads to self sufficiency= cells telling themselves to proliferate

myeloid-derived suppressor cells (MDSC)

cells present in tumor microenvironment that inhibit T cell responses by producing arginase, INOS, and Tregs

Cytokeratin

commonly used immunohistochemical marker of epithelial-derived tissues. Cytokeratins are proteins of cytoskeletal intermediate filaments, and their main function is to enable cells to withstand mechanical stress

Oncogenes

encode proteins capable of inducing cellular transformation. Oncogenes derived from viruses are v-onc and oncogenes derived from normal cells (proto-oncogenes) are called c-onc

direct immunofluorescence

fluorophore is conjugated directly to the antibody molecule that recognizes and binds the molecule of interest

Category I genes

genes that induce cellular proliferation- we call some of them proto-oncogenes because they drive cells into cycle (GAS PEDAL)

Category III genes

genes that regulate programmed cell death (aka apoptosis)

Category II genes

genes that suppress or inhibit cellular proliferation- we call some of them tumor suppressor genes because they stop the cell from cycling (BRAKE PEDAL)

PDL-1 Inhibitors

if PD-1 is blocked by a checkpoint antibody, the T cell will NOT be turned off thus the T cell will remain active and kill the tumor

Treg cells in cancer

involved in maintaining immune homeostasis: they protect hosts from developing autoimmune diseases and allergy, whereas in malignancies, they promote tumor progression by suppressing effective antitumor immunity inhibit T cell responses

BMPs (embryogenesis vs tumor)

tumor suppressor embryogenesis: contributes to apoptosis and tumors: regulation of PTEN (apoptosis), transcription of p21 (cell cycle regulator), and caspase (apoptosis)

PTEN gene

tumor suppressor phosphatase-dependent and phosphatase-independent (scaffold) activities in the cell and governs a variety of biological processes, including maintenance of genomic stability, cell survival, migration, proliferation and metabolism.

Loss of function mutation in Rb

tumor suppressor if inactive, Rb cannot bind transcription factor, thus it can transcribe S- phase genes

Loss of function mutation in PTEN

tumor suppressor no maintenance of genomic stability, cell survival, migration, proliferation and metabolism.

Checkpoint inhibitors

molecules that are used by the immune system to turn 'off' killer T cells cancer cells use these molecules to stop 'killer' T cells from attacking. Scientists know that cancer cells are sneaky and thus stop them from using this trick

Knudson hypothesis (2 hit theory)

most loss-of-function mutations that occur in tumor suppressor genes are recessive in nature. Thus, in order for a particular cell to become cancerous, both of the cell's tumor suppressor genes must be mutated. = LOSS OF HETEROZYGOSITY

Mutations and genomic instability

no one mutation causes cancer - it requires several consecutive mutations - genomic instability can be on the level of point mutations or double stranded DNA break level

Proto-oncogenes

normal cellular genes that are important regulators of normal cellular processes, they promote growth. alterations in the expression of these cells result in oncogenes

Macrophages

often cluster around tumors; their presence is often correlated with tumor regression activated macrophages secrete TNF-alpha a cytokine with potent anti tumor activity

constitutive activation of PI3K

oncogene - no inhibition of bad protein synthesis - unregulated cell proliferation and cell cycle progression

Hedgehog/gli

oncogene embryogenesis: growth and differentiation of mesoderm, hematopoiesis tumors: gli activates cyclin D= increase cell cycling

PARS (embryogenesis vs tumor)

oncogene embryogenesis: growth factor, cell differentiation, embryonic asymmetry, microtubule formation tumors: the proliferation of cancer

EMT (embryogenesis vs tumor)

oncogene embryogenesis: it allows gastrulation and neurulation tumors: metastasis

Amplification of EFGR gene

oncogene mutations in the EGFR gene cause epidermal growth factor receptor proteins to be made in higher than normal amounts contributing to the promotion of cell growth and division

NOTCH (embryogenesis vs tumor)

oncogene or tumor supressor embryogenesis: involved in differentiation and activation of transcription factor tumors: can function as an oncogene or tumor suppressor

WNT (embryogenesis vs tumor)

oncogene- APC embryogenesis: B-catenin is a transcription factor affecting tooth development, CNS, and limb polarity tumors: constitutive activation of B-catenin causes overexpression of Cyclin D

Loss of function mutation in P53

p53 is a tumor suppressor gene, thus, a lost of function mutation would prevent cell cycle arrest at the G1 checkpoint this prevents DNA repair and apoptosis of DNA damage beyond repair contributing to further mutations

epithelial-mesenchymal transition (EMT)

polarized epithelial cell, which normally interacts with basement membrane via its basal surface, to undergo multiple biochemical changes that enable it to assume a mesenchymal cell phenotype, which includes enhanced migratory capacity, invasiveness, elevated resistance to apoptosis, and greatly increased production of ECM components. The completion of an EMT is signaled by the degradation of underlying basement membrane and the formation of a mesenchymal cell that can migrate away from the epithelial layer in which it originated.

elimination

potential cancer cells are created but they don't reach a clinical status because the immune system recognizes them and eliminates them

IFN-gamma

produced by CD4+, CD8+ and NK to activate macrophage

TNF-alpha

promotes inflammation produced by Tcells, DC and macrophage

PGE-2 in cancer

prostaglandin supports tumor growth by promoting angiogenesis, stimulating tumor-cell proliferation, and protecting tumor cells from apoptosis.

PDL-1

protein expressed by self cells when PD-1 on the T cell is bound by PDL-1 on the tumor/self cell, this connection tells the tumor to stop its attack

SNAIL-1

zinc finger transcriptional repressor which downregulates the expression of ectodermal genes within the mesoderm involved in lymph node metastasis and recurrence