principles of cancer biology LC P II

Question 1

key steps of angiogenesis:

Answer 1

1. Vasodilation and Increased Permeability
2. Degradation of Extracellular Matrix (ECM);
   Proteases, such as matrix metalloproteinases (MMPs) and plasminogen activators, degrade the surrounding extracellular matrix (ECM), creating space
   Endothelial cells at the tip of growing vessels, called tip cells, lead the way by extending filopodia and sprouting into the surrounding tissue
3. Endothelial Cell Migration and Proliferation: Endothelial cells from pre-existing vessels migrate towards the angiogenic stimulus.
   Endothelial cells proliferate, forming a solid sprout. the sprouting endothelial cells are guided by various chemotactic signals, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and angiopoietins
4. Formation of Tube-Like Structures:
   migrate and proliferate, they organize into tube-like structures.
   Pericytes, which are contractile cells, are recruited to the newly formed vessels to provide structural support and stabilize the nascent vessels.
   mediated by signaling molecules such as PDGF-BB and Angiopoietin-1
5. Vessel Maturation and Remodeling
   newly formed blood vessels undergo maturation and remodeling to become functional.
   Pericytes play a crucial role in vessel stabilization and maturation by secreting extracellular matrix components and regulating vessel diameter.
   The basement membrane surrounding the vessels is reestablished
   mediated by signaling molecules such as PDGF-BB and Angiopoietin-1.
6. Vessel Regression or Stabilization
   normal physiological processes, angiogenesis is tightly regulated, and once the tissue is adequately vascularized, angiogenesis ceases, and vessels may regress.
   However, in pathological conditions such as cancer, angiogenesis may become dysregulated, leading to continued vessel growth and formation.

Question 2

What are endogenous pro & anti-angiogenic signals?

Answer 2

PRO - VEGF, PlGF, PDGF, TNFα, TGFβ, Ang1,2, IL8

anti - TSP1, angiostatin/endo, PEX (proteolysis of MMP2), interferons IFN

Question 3

What treatments are inhibitors of angiogensis?

Answer 3

Bevacizumab (Avastin), Metronomic chemotherapy, Thilomadine, angiostatin

Question 4

Initiation of Angiogenesis:

Answer 4

Hypoxia: Decreased oxygen levels trigger the release of hypoxia-inducible factors (HIFs), particularly HIF-1α.

Inflammation: Inflammatory cells release cytokines, growth factors, and chemokines that stimulate angiogenesis.

Tumor-Derived Factors: Tumor cells produce angiogenic factors to promote blood vessel growth to support tumor growth and metastasis.

Question 5

Angiogenic Mediators:

Answer 5

VEGF
VHL
Fibroblast Growth Factor (FGF):
FGFs, particularly FGF-2, promote endothelial cell proliferation and migration.
They also stimulate the expression of proteases involved in ECM degradation.

Angiopoietins:
Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2) regulate blood vessel maturation and remodeling.
Ang-1 stabilizes blood vessels by promoting pericyte recruitment and vessel maturation.
Ang-2 destabilizes vessels, allowing them to respond to angiogenic signals.

Platelet-Derived Growth Factor (PDGF):
PDGF stimulates pericyte recruitment to newly formed blood vessels.

Transforming Growth Factor-Beta (TGF-β):

Epidermal Growth Factor (EGF):
EGF stimulates endothelial cell proliferation and migration.
It also induces the expression of proteases involved in ECM degradation.

Question 6

how does TSP1 inhibit angiogenesis

Answer 6

Inhibits endothelial cell migration and angiogenesis by binding to CD36 receptors.

Question 7

What pathways does VEGF stimulate?

Answer 7

PI3K, BcL2

Question 8

what is vascular mimicry

Answer 8

Tumor-made channels for fluid transport independent of typical modes of angiogenesis

Question 9

what is the basics of the seed and soil hypothesis

Answer 9

the growth of metastatic tumors (the “seeds”) depends on the compatibility between the tumor cells and the microenvironment of distant organs (the “soil”).

The microenvironment includes various components such as blood vessels, extracellular matrix (ECM), immune cells, and stromal cells. The microenvironment of each organ is unique and provides specific signals and support for the growth of metastatic tumor cells.

Question 10

Tumor Cell Homing

Answer 10

Metastatic tumor cells selectively home to specific organs based on the interaction between tumor cell surface receptors and chemokines/adhesion molecules expressed in the target organ.

Question 11

Preparation of Metastatic Niche:

Answer 11

Before tumor cells arrive, the pre-metastatic niche is often created by primary tumor-derived factors, such as exosomes, cytokines, and growth factors, which prepare the distant organ for tumor cell colonization.

Question 12

Organotropism:

Answer 12

Certain types of cancer cells have a preference for specific organs, a phenomenon known as organotropism. For example, breast cancer cells tend to metastasize to bones, lungs, liver, and brain.

Clinical Implications:
Understanding the seed and soil interactions can help explain patterns of metastasis observed in cancer patients.
Targeting the components of the tumor microenvironment offers new therapeutic strategies for preventing or treating metastasis.
Biomarkers associated with the microenvironmental niche may serve as prognostic indicators or targets for personalized therapy.

Question 13

Biomarkers associated with the microenvironmental niche that serve as prognostic indicators or targets for personalized therapy

Answer 13

Hypoxia-Inducible Factor 1 (HIF-1):
High levels of HIF-1 expression are associated with poor prognosis in various cancers, as they promote tumor angiogenesis, metastasis, and resistance to therapy.

Vascular Endothelial Growth Factor (VEGF):
VEGF is a key angiogenic factor that promotes the formation of new blood vessels.
High levels of VEGF expression correlate with increased tumor angiogenesis and poor prognosis in many cancer types.
Anti-VEGF therapies, such as bevacizumab, inhibit angiogenesis and have been used to treat several cancers, including colorectal, lung, and kidney cancer.

Transforming Growth Factor-Beta (TGF-β):
TGF-β is a multifunctional cytokine that regulates cell proliferation, differentiation, and migration.

Matrix Metalloproteinases (MMPs):
MMPs are enzymes involved in ECM degradation and remodeling, facilitating tumor invasion and metastasis.
Elevated levels of MMP expression correlate with aggressive tumor behavior and poor prognosis.
MMP inhibitors have been investigated as potential anticancer agents.

Tumor-Infiltrating Immune Cells:
Tumor-infiltrating lymphocytes (TILs), particularly cytotoxic T cells, are associated with improved survival in many cancers.
Immunotherapies, such as immune checkpoint inhibitors (e.g., anti-PD-1/PD-L1 antibodies), harness the patient’s immune response to target cancer cells.

Cancer-Associated Fibroblasts (CAFs):
CAFs are stromal cells that promote tumor growth, invasion, and metastasis through paracrine signaling and ECM remodeling.
High levels of CAF infiltration are associated with poor prognosis in several cancers.

Extracellular Vesicles (EVs):
EVs, including exosomes, are small membrane vesicles released by tumor and stromal cells.
EVs play roles in cell-cell communication, immune modulation, and pre-metastatic niche formation.

Cancer Stem Cells (CSCs):
including self-renewal and tumor-initiating capacity

Question 14

cancer stem cells

Answer 14

CSCs are a subpopulation of tumor cells with stem cell-like properties, including self-renewal and tumor-initiating capacity

CSCs are resistant to conventional therapies and are associated with tumor recurrence and metastasis.

Targeting CSC-specific pathways is being explored as a strategy to prevent tumor relapse and metastasis.

Question 15

hemodynamic pattern of metastasis definition

Answer 15

hemodynamic pattern of metastasis refers to the routes through which tumor cells disseminate from the primary tumor to distant organs, facilitated by the bloodstream.

Question 16

two major hemodynamic patterns of metastasis

Answer 16

1. Hematogenous Metastasis:
   In hematogenous metastasis, tumor cells spread through the bloodstream to distant organs.
2. Lymphatic Metastasis:
   In lymphatic metastasis, tumor cells spread via the lymphatic system to regional lymph nodes and eventually to distant organs

Question 17

The process of hematogenous metastasis

Answer 17

Intravasation: Tumor cells invade nearby blood vessels (veins or capillaries) within or adjacent to the primary tumor.

Survival in Circulation: Tumor cells survive the mechanical and immune challenges within the bloodstream, aided by interactions with platelets and immune cells.

Arrest and Extravasation: Tumor cells adhere to the endothelium of blood vessels at distant sites and extravasate into the surrounding tissue.

Micrometastasis Formation: Once extravasated, tumor cells may form micrometastases in the new tissue microenvironment.

Hematogenous metastasis can occur in any organ but tends to prefer specific organs based on tumor type and the presence of suitable microenvironments.

Question 18

the process of lymphatic pattern of metastasis

Answer 18

Invasion of Lymphatic Vessels: Tumor cells invade lymphatic vessels within or near the primary tumor.

Transport in Lymphatic Circulation: Tumor cells travel through the lymphatic system, which consists of lymph nodes and lymphatic vessels.

Lymph Node Metastasis: Tumor cells may accumulate in regional lymph nodes, where they can form metastatic deposits.

Further Spread: Tumor cells from lymph nodes can disseminate to distant organs through hematogenous or lymphatic routes.
Lymphatic metastasis is common in cancers arising from epithelial tissues, such as breast, lung, and gastrointestinal cancers.

Question 19

genes associate with cancer metastasis

Answer 19

MEK, N-cadherin, SNAIL, Slug, TWIST, Zeb 1/2

Twist1 and Twist2,
Snail1 and Snail2 (Slug),
MMP-2 and MMP-9, MT1-MMP (MMP-14),
E-cadherin (CDH1): Loss of E-cadherin - mam carcinoma
N-cadherin (CDH2)- osteosarcoma and feline mammary carcinoma
VEGF-A - HSA , OSA
Angiopoietin-2 (ANGPT2),
PIK3CA (p110α) - mast cell tumors and canine melanoma.
PTEN: Loss of PTEN function leads to PI3K pathway activation - mast cell tumors and canine melanoma.
MEK,
BRAF,
CTNNB1 (β-catenin)
TGF-β - mammary carcinoma and feline injection site sarcoma
SMADs (SMAD2, SMAD3, SMAD4)
TP53 (p53) - OSA, fel mam carc
KRAS - Canine lung adenocarcinoma and colorectal cancer in horses
BRCA1/2
PD-L1 (CD274)
CTLA4
C-MET (MET)- oral melanoma and canine osteosarcoma

Question 20

Metastasis suppression genes

Answer 20

MKK4, KISS1 (loss in canine mammary met tumors), NME, BrMS1, Kai1/CD82, BRMS1, NM23

Question 21

The cancer stem cell theory

Answer 21

proposes that within a tumor, only a small subset of cells, termed cancer stem cells, possess the ability to self-renew and initiate tumor growth.

Cancer stem cells share characteristics with normal stem cells, including self-renewal and differentiation capabilities.

These cells are thought to be responsible for tumor initiation, progression, metastasis, and resistance to therapy

Question 22

Properties of Cancer Stem Cells:

Answer 22

Self-Renewal: Cancer stem cells have the ability to self-renew, generating identical daughter cells.

Differentiation: They can differentiate into various cell types within the tumor, contributing to tumor heterogeneity.

Tumorigenicity: Cancer stem cells are capable of initiating tumor formation when transplanted into immunocompromised mice at low cell numbers.

Quiescence: Some cancer stem cells may exist in a quiescent or slow-cycling state, making them resistant to chemotherapy and radiation therapy.

Resistance to Therapy: Cancer stem cells are thought to be responsible for tumor recurrence and resistance to conventional cancer therapies.

Question 23

What can be used to identify stem cells?

Answer 23

o High ALDH
o High ABCB1
o Also:
1. high CD44, low CD24
2. CD133: brain/colon/liver
3. CD34: myeloid
4. ESA: colon
5. Nestin: glioma
6. SOX2: glioma/lung

Question 24

ALDH and CSCs

Answer 24

• ALDH enzymes are involved in the detoxification of aldehydes and the oxidation of retinol to retinoic acid.
• High ALDH activity is a common marker of CSCs in various cancers, including breast, colon, and lung cancers.
• ALDH-positive CSCs often exhibit enhanced oxidative stress resistance and can utilize both glycolysis and oxidative phosphorylation for energy production.

Question 25

CSCs and treatment resistance 8 concepts

Answer 25

1. Quiescence and Slow-Cycling:
   CSCs often exist in a quiescent or slow-cycling state, which makes them less susceptible to traditional cancer treatments that target rapidly dividing cells.
2. Efflux Pump Expression:
   CSCs frequently overexpress ATP-binding cassette (ABC) transporters, such as ABCG2 (also known as breast cancer resistance protein, BCRP), which efflux chemotherapeutic drugs from the cells.
3. DNA Repair Mechanisms:
   CSCs often exhibit increased expression of DNA repair enzymes, which enhances their ability to repair DNA damage induced by chemotherapy and radiation therapy.
4. Anti-Apoptotic Pathways:
   CSCs have upregulated anti-apoptotic pathways, such as the Bcl-2 family of proteins, which protect them from apoptosis induced by cytotoxic agents.
5. Heterogeneous Expression of Surface Markers:
   CSCs are characterized by heterogeneity in surface marker expression, which enables them to evade targeted therapies that specifically target a subset of cells.
6. Metabolic Adaptations:
   CSCs often display metabolic plasticity and can switch between glycolysis and oxidative phosphorylation depending on microenvironmental conditions. SOX2, Nestin, CD133, CD44,
7. Tumor Microenvironment Interactions:
   CSCs interact with the tumor microenvironment, including stromal cells, immune cells, and extracellular matrix components, to promote tumor growth and survival.
8. Stemness Signaling Pathways:
   Signaling pathways associated with stemness, such as Wnt/β-catenin, Notch, and Hedgehog, are often dysregulated in CSCs.
   Activation of these pathways promotes CSC self-renewal, survival, and resistance to therapy.

Question 26

Cancer stem cell populations in lymphoma in dogs and impact of cytotoxic chemotherapy

Answer 26

Cells resistant to CHOP had increased expression of CSC markers
Had greater aldehyde dehydrogenase activity

Question 27

Analysis of radiosensitivity of cancer stem-like cells derived from canine cancer cell lines

Answer 27

CD133 gene expression
CSC resistant to irradiation compared to normal cells

Question 28

Identification of the JAK-STAT pathway in what canine tumors

Answer 28

canine splenic hemangiosarcoma, thyroid carcinoma, mast cell tumor, and anal sac adenocarcinoma

Significant correlations between JAK 1/2 or STAT3 and activated or downstream components were identified in all tumor types

pSTAT3 was correlated with development of metastasis in dogs with MCT, while increased JAK1 expression or activation may impact survival in dogs with MCT or HSA

Question 29

how does inflammation lead to cancer 6 steps

Answer 29

1. Initiation of Cancer:
   Chronic inflammation leads to DNA damage and genetic mutations, which can initiate the process of tumorigenesis.

Inflammatory cells, such as neutrophils, macrophages, and lymphocytes, produce reactive oxygen and nitrogen species (ROS/RNS) that cause DNA damage and mutations in epithelial cells.

2. Tumor Promotion:
   Inflammatory mediators, including cytokines, chemokines, and growth factors, promote cell proliferation, survival, and angiogenesis, facilitating tumor growth.

Tumor-promoting cytokines, such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 (IL-1), activate signaling pathways that promote cell proliferation and survival.

Chronic inflammation leads to the recruitment of immune cells, such as tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs), which create an immunosuppressive microenvironment that promotes tumor growth and progression.

3. Angiogenesis:
   Inflammatory mediators stimulate the production of angiogenic factors, such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF), promoting the formation of new blood vessels (angiogenesis) to supply nutrients and oxygen to the growing tumor.
4. Metastasis:
   Inflammation enhances the invasiveness and metastatic potential of cancer cells by promoting epithelial-mesenchymal transition (EMT).

Inflammatory cytokines and chemokines stimulate the recruitment of immune cells to the primary tumor site, which can facilitate the intravasation of cancer cells into the bloodstream and lymphatic vessels.
Inflammatory cells create a pre-metastatic niche in distant organs, facilitating the colonization and growth of metastatic cancer cells.

5. Immune Evasion:
   Inflammatory mediators contribute to immune evasion by promoting the expression of immune checkpoint molecules, such as programmed cell death ligand 1 (PD-L1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), on cancer cells.

Immunosuppressive cells, such as regulatory T cells (Tregs) and MDSCs, inhibit the activity of cytotoxic T cells, preventing them from attacking cancer cells.

6. Genomic Instability:
   Inflammatory responses can induce genomic instability by generating ROS/RNS and activating DNA damage pathways, increasing the likelihood of acquiring additional mutations and promoting tumor progression.

Question 30

What IL connects innate & adaptive immunity?

Answer 30

IL 12

Question 31

When are CD4/CD8 double negative? Double positive?

Answer 31

Neg when enter/in thymus and double positive-thymomas

Question 32

What metabolic pathway do most cancer cells use and why?

Answer 32

Aerobic glycolysis; Cancer cells need more than gluc/ATP which they get from this system; produce high levels of lactate and do not use mitochondria as much as normal

Question 33

Is MHC-I use endogenous or exogenous peptide pathway?

Answer 33

MHC-I uses endogenous so intracellular contents

Question 34

How are TH stimulated/activated?

Answer 34

APC-MHCII-activates Th2(by IL4)-IL4 -> activates CD4-make Ab and switching, IL2- more CD8;
APC MHCI-activates CTL, and Th1(by IL12)-> CD8, IL2, GMCSF, IFNy

Question 35

How does peripheral tolerance occur?

Answer 35

Escaped central tolerance; Deletion of clonal Tcells(lack of costimulatory), Anergy (lack of costim), Ignorance, Regulation(Treg)

Question 36

What are the positive markers/cell types for Treg

Answer 36

CD4, CD25, FoxP3

Question 37

What do Treg secrete?

Answer 37

TGFb, IL10

Question 38

How do tumors evade the immune system?

Answer 38

Decreased MHC-I expression (CD8 miss), Immunosuppressive cytokines (TGFb, IL10, TNFa), Increased Treg, Increase Myeloid derived suppressor cells, Fail to express costimulators, DC dysfunction, Direct death through FasL on tumor

Question 39

What evidence is there that the immune system is involved with tumors?

Answer 39

Spontaneous remission w/o tx; Paraneoplastic autoimmunity; CTL in tumor; Increased risk of tumors in immunosuppressed

Question 40

What is BCG and how does it affect the immune system?

Answer 40

From mycobacterium and releases IFNy and IL2

Question 41

NF-kB pathway

Answer 41

The canonical pathway is induced by TLRs, TNFRs, and IL-1R. Activation of this cascade leads to the phosphorylation and degradation of inhibitory protein IκB. NF-κB is activated by release from the IκB-containing complex, then translocating into nucleus.

The non-canonical pathway is dependent on the activation of NF-κB2 (p100)/ RelB complex by BAFFR, CD40, and RANK. This cascade induces phosphorylation of NIK, which subsequently phosphorylates IKKα. Then p52-RelB heterodimer is activated and translocate to the nucleus.