MBB 446 Lecture 2 Flashcards
About _______ Canadians will develop cancer in their lifetimes and ______ will die of the disease;
- 1 in 2
2. 1 in 4
Define cancer
a group of diseases characterized by the uncontrolled growth and spread of abnormal cells
How many different types of cancer are there?
More than 200 (Cancer can develop from almost any type of cell in the body..)
How do cells acquire hallmarks of cancer?
As normal cells evolve progressively to a neoplastic state, they acquire these hallmark capabilities.
What are the original 6 core hallmarks of cancer?
- Sustaining proliferative signaling
- Evading growth suppressors
- Activating invasion and metatasis
- Enabling replicative immortatlity
- Inducing angiogenesis
- Resisting cell death
Proliferation of normal cells requires what 4 things to be overcome?
- Requires growth signals
- DNA checkpoints
- Activating apoptosis (suicide)
- Reproductive quota
What phase are most adult cells in?
Most adult cells are NOT actively dividing: they are QUIESCENT = in the G0 (inactive) part of the cell cycle
Genes involved in tumorigenesis include those whose products do what 3 possible things?
- directly regulate cell proliferation (either promoting or inhibiting);
- are involved in the repair of damaged DNA
- control programmed cell death or apoptosis
Depending on how they affect each process, these genes can be grouped into two general categories:
- proto-oncogenes (growth promoting).
2. tumor suppressor genes (growth inhibitory)
Mutant alleles of proto-oncogenes are called ______.
oncogenes
Tumor suppressor genes may be divided into what two groups?
- Promoters
2. Caretaker genes
What are promoters?
Mutation of these genes leads to transformation by directly releasing the brakes on cellular proliferation (e.g. the traditional tumor suppressors p53 and RB)
What are caretaker genes?
They are responsible for processes that ensure the integrity of the genome, such as those involved in DNA repair. Cells with mutations in caretaker genes are said to have a “mutator phenotype”.
Cells with mutations in caretaker genes are said to have what kind of phenotype
Mutator phenotype
How does Hallmark 1: Sustaining proliferative signaling achieved through manipulation of growth signals? Describe the role of growth cells in normal cells vs. tumor cells
- Normal cells: require growth signals (GS) before they start dividing. These signals are transmitted into the cell by transmembrane receptors that bind distinctive classes of signaling molecules.
- Tumor cells: generate their own growth signals, thereby reducing their dependence on stimulation from their normal tissue microenvironment
Describe the ways by which tumour cells sustain proliferative signaling
- Signal transduction
- Oncogenes
- a) Growth factor
b) Growth factor receptors
c) Oncoproteins (signal transducers, nuclear regulatory proteins, and cell cycle regulators)
What are the 3 common strategies for achieving growth signal autonomy? What are the oncogene products (oncoproteins) associated with each?
- Strategy: Alteration of extracellular growth signals
- Oncogene products (oncoproteins): Growth factors
- Strategy: Alteration of transcelluar transducers of those signals
- Oncogene products (oncoproteins): Growth factor receptors
- Strategy: Alteration of intracellular circuits that translate those signals into action
- Oncogene products (oncoproteins):
a) Signal transduction proteins
b) Nuclear regulatory proteins
c) Cell cycle regulators
What are two examples of growth factors?
- platelet-derived growth factor (PDGF)
2. transforming growth factor α (TGF-α)
Many cancer cells acquire the ability to synthesize GFs to which they are responsive, creating a _______.
positive feedback signaling loop
Draw diagram show casing positive feedback signaling loop of growth factors in tumor cells
N/A Lecture 2 Slide 16
3 examples of growth factor receptors?
- ERBB1 (EGFR)
- ERBB2 (HER2)
- ALK
What can receptor over-expression cause?
may enable the cancer cell to become hyperresponsive to ambient levels of GF that normally would not trigger proliferation
Draw diagram showcasing overexpression of receptors
N/A Lecture 2 Slide 17
What can alterations in components of the downstream cytoplasmic circuitry that receives and processes the signals emitted by GF receptors cause?
can release a flux of signals into cells, without ongoing stimulation by their normal upstream regulators
Draw pathway of some common oncoproteins
N/A Lecture 2 Slide 18
What is hallmark 2?
Hallmark 2. Insensitivity to anti-growth signals (i.e. Evading growth suppressors)
Describe where the checkpoints usually are and their fxn?
G1, G2 and M-phase checkpoints sense DNA damage and induce a cellular response, typically cell cycle arrest
What does disruption of checkpoint fxn lead to?
mutations that induce carcinogenes
Contrast oncogenes and tumor suppressor genes
Whereas oncogenes drive the proliferation of cells, the products of most tumor suppressor genes apply brakes to cell proliferation, and abnormalities in these genes lead to failure of growth inhibition, another fundamental hallmark of carcinogenesis.
What is the “guardian of the genome”?
P53
___% of all sporadic cancers have a p53 mutation
50-75%
What is Li-Fraumeni syndrome?
25-fold greater chance of developing a malignant tumor by age 50
Draw a diagram depicting DNA damage in a normal cell vs. p53 mutated cell
N/A Lecture 2 Slide 21
Who is the “governor of proliferation (cell cycle)”
Retinal blastoma (RB)
Fxn of RB in normal cell?
Normal growth factor signaling leads to RB hyperphosphorylation and inactivation, thus promoting cell cycle progression.
What happens when RB is hypophosphoryated?
When hypophosphorylated, RB exerts antiproliferative effects by binding and inhibiting E2F transcription factors that regulate genes required for cells to pass through the G1-S phase cell cycle checkpoint.
Draw a diagram of normal cell with normal growth factor signaling vs. cell with growth inhibitors
N/A Lecture 2 Slide 22
Describe Knudson’s two hit hypothesis for retinoblastoma
- Sporadic Rb: Two hits required
2. Inherited Rb: First hit is inherited, only one additional hit required
Draw a diagram showcasing a sporadic Rb and inherited RB
N/A Lecture 2 Slide 23
What is hallmark #3?
Hallmark 3. Evading death (apoptosis)
What is apoptisis
Apoptosis – programmed cell death, is a self-destruct mechanism, triggered in normal cells in response to either external death-inducing signals or signals of intracellular origin.
What are 6 mechanisms of evading apoptosis?
- Loss of p53, leading to reduced function of pro-apoptotic factors such as BAX.
- Reduced egress of
cytochrome c from mitochondria as a result of upregulation of anti-apoptotic factors such as BCL2, BCL-XL, and MCL-1. - Loss of apoptotic peptidase activating factor 1 (APAF1).
- Upregulation of inhibitors of apoptosis (IAP).
- Reduced CD95 level.
- Inactivation of death-induced signaling complex.
Draw a diagram of typical apoptosis pathway
N/A Lecture 2 Slide 26
What is hallmark #4
Hallmark 4. Limitless replicative potential
What is the replicative potential of normal cells?
- have a finite replicative potential (around 60-70 doublings).
- DNA telomeres (chromosome ends), shorten progressively with each replication
How do cancer cells acquire limitless replicative potential
Cancer cells acquire lesions that inactivate senescence signals and reactivate telomerase
What is telomerase
an enzyme that can prolong the telomeres and help maintain telomeric DNA at lengths sufficient to avoid triggering senescence or apoptosis.
Draw a diagram showcasing how cancer cells are able to evade senescence and mitotic crisis
N/A Lecture 2 Slide 29
What are cancer stem cells
those cells within a tumor that can self-renew and drive tumorigenesis
How do cancer stem cells “self-renew”?
Each time a stem cell divides at least one of the two daughter cells remains a stem cell
Two possible ways by which stem cells arise?
- from transformed tissue stem cells with intrinsic “stemness”
- from proliferating cells that acquire a mutation that confers “stemness
- In both instances, the CSC undergo asymmetric cell divisions that give rise to committed progenitors that proliferate more rapidly than the CSC
Effectiveness of conventional chemotherapy on CSC?
CSC are resistant to conventional chemotherapy
Draw diagram of pathway of normal stem cell vs. cancer stem cell
N/A Lecture 2 slide 30
What is hallmark #5
Hallmark 5. Sustained angiogenesis
What is angiogenesis?
the formation of new blood vessels from pre-existing vessels
How does angiogenesis differ in normal tissue vs. tumour?
Normal tissue - as part of physiologic processes such as wound healing, angiogenesis is turned on, but only transiently
Tumour - an “angiogenic switch” is almost always activated and remains on, causing normally quiescent vasculature to continually sprout new vessels that help sustain expanding neoplastic growths
Why is inability to induce angiogenesis so limiting?
Even if a solid tumor possesses all of the genetic aberrations that are required for malignant transformation, it cannot enlarge beyond 1 to 2 mm in diameter unless it has the capacity to induce angiogenesis.
What two factors regulate angiognesis?
- p53 induces synthesis of the angiogenesis inhibitor thombospondin-1
- RAS, MYC, and MAPK signaling all upregulate VEGF expression and stimulate angiogenesis.
What are the inhibitors of angiognesis
- Thrombospondin-1
2. The statins: angiostatin, endostatin, canstatin, turnstatin
What are the activators of angiognesis
- VEGFs
- FGFs
- PDGFB
- EDF
- LPA
What is hallmark #6?
Hallmark 6. Tissue invasion and metastasis
What are metastases?
Distant settlements of tumor cells
metastases - are the cause of ___% of human cancer deaths
90%
What does the ability to metastasize and the potential target locations depend on?
- Additional gene expression alterations acquired by different cell sub-populations in the primary tumor
- To acquire metastatic capabilities, cancer cells typically develop alterations in their shape as well as in their attachment to other cells and to the extracellular matrix (ECM).
- Tumor cells and stromal cells secrete proteolytic enzymes (e.g. matrix metalloproteases, cathepsins) that degrade basement membranes and ECM, release growth factors and generate chemotactic and angiogenic fragments from cleavage of ECM glycoproteins.
Describe how a tumor cell leads to metastasis
Cancer cell dissociates from Primary Tumor
- Tumor cell undergoes EMG
- Intravasation
Enters blood stream
3. Circulating tumor cell (CTC)
Cancer cells leaves bloodstream and colonizes secondary location
- Extravasation
- Tumor cell undergoes MET
- Tumor cell proliferates at secondary location and forms a metastases
What are epithelial markers seen during metastasis
- E-cadherin
- Claudin
- Occludin
What are signals seen during metastasis
TGF-B, FGF, HGF, PDGF, IGF, VEGF, Estrogen, Notch, Wnt, EGF
What are transcriptional factors seen during metastasis
ZEB1/ZEB2, Snai1, Snai2, Twist1/Twist2
What are post-transcriptional mechanisms seen during metastasis
- Inc RNA
2. Inc miRNAs
What are mesenchymal markers seen during metastasis
- N-cadherin
- P-cadherin
- Vimentin
- Fibronectin
What is EMT cycle?
Epithelial-mesenchymal transition (EMT) cycle
What is MET cycle?
Mesenchymal epithelial transition cycle
Draw a diagram showing the EMT and MET cycle
N/A Lecture 2 Slide 34
What are the 4 “new” hallmarks of cancer? Which are emerging hallmarks and which are enabling characteristics
Emerging hallmarks (2)
- Deregulating cellular energetics
- Avoiding immune destruction
Enabling hallmarks (2)
- Genome instability and mutation
- Tumor-promoting inflammation
What is immune surveillance
a normal function of the immune system is to constantly “scan” the body for emerging malignant cells and destroy them
What is cancer immunoediting?
the ability of the immune system to change 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
What are the 4 mechanisms of immune evasion by tumors?
- Selective outgrowth of antigen-negative variants
- Secretion of immunosuppressive factors by cancer cells (TGF-β galectins, sugar-rich lectin-like factors IL-10, prostaglandin E2, certain metabolites derived from tryptophan, and VEGF)
- Engaging of normal pathways of immune regulation that serve as “checkpoints” in immune responses, e.g. tumor cells may upregulate the expression of PD-L1 and PD-L2, cell surface proteins that activate the programmed death-1 (PD-1) receptor on effector T cells and inhibit T cell activation.
- Induction of regulatory T cells (Tregs)
What is the stimulatory factor of release of cancer cell antigens?
Immunogenic cell death
What is the inhibitory factor of release of cancer cell antigens?
Tolergenic cell death
What are the stimulatory factors of cancer antigen presentation in the cancer-immunity cell?
- TNF-a
- IL-1
- ATP
- TLR
What are the inhibitory factors of cancer antigen presentation in the cancer-immunity cell?
- IL-10
- IL-4
- IL-13
What are the stimulatory factors of priming and activation in the cancer-immunity cell?
- IL-2
- IL-12
- GITR
What are the inhibitory factors of priming and activation in the cancer-immunity cell?
- Prostaglandins
- PD-L1/PD-1
- PD-L1/B7.1
What are the stimulatory factors of trafficking of T cells to tumours in the cancer-immunity cell?
- CX3CL1
- CXCL9
- CXCL10
- CCL5
What are the stimulatory factors of “infiltration of T cells into tumors” in the cancer-immunity cell?
- LFA1/CAM1
2. Selectins
What are the inhibitory factors of “infiltration of T cells into tumors” in the cancer-immunity cell?
- VEGF
2. Endothelin B receptor
What is the stimulatory factor of “recognition of cancer cells by T cells” in the cancer-immunity cell?
T cell receptor
What are the inhibitory factor of “infiltration of T cells into tumors” in the cancer-immunity cell?
Reduced pMHC on cancer cells
What is the stimulatory factor of “killing of cancer cells” in the cancer-immunity cell?
- IFN-gamma
2. T cell granule content
What are the inhibitory factor of “killing of cancer cells” in the cancer-immunity cell?
- Arginase
- TGF-beta
- VISTA
What are the 7 steps in the cancer-immunity cycle?
- Release of cancer cell antigens
- Cancer antigen presentation
- Priming and activation
- Trafficking of T cells to tumors
- Infiltration of T cells into tumors
- Recognition of cancer cells by T cells
- Killing of cancer cells
What are therapies that affect step 1 of the cancer immunity cycle, “release of cancer cell antigens”
- Chemotherapy
- Radiation therapy
- Targeted therapy
What are therapies that affect step 2 of the cancer immunity cycle, “cancer antigen presentation”
- Vaccines
- IFN-alpha
- GM-CSF
- Anti-CD40 (agonist)
- TLR agonists
What are therapies that affect step 3 of the cancer immunity cycle, “priming and activation”
- Anti-CTLA4
- Anti CD137 (agonist)
- Anti-OX40 (agonist)
- Anti-CD27 (aongist
- IL-2
- IL-12
What are therapies that affect step 4 of the cancer immunity cycle, “trafficking of T cells to tumours”
None
What are therapies that affect step 5 of the cancer immunity cycle, “infiltration of T cells into tumors”
Anti-VEGF
What are therapies that affect step 6 of the cancer immunity cycle, “recognition of cancer cells by T cells”
CARs
What are therapies that affect step 7 of the cancer immunity cycle, “killing of cancer cells”
- Anti-PD-L1
- Anti-PD-1
- IDO inhibitors
3 ways tumor cells inhibit tumor immunity
- Tumor cells actively inhibit tumor immunity by engaging normal pathways of immune regulation that serve as “checkpoints” in immune responses.
2, Tumor cells may upregulate the expression of PD-L1 and PD-L2, cell surface proteins that activate the programmed death-1 (PD-1) receptor on effector T cells and inhibit T cell activation.
3, Tumor cells may downregulate the expression of co-stimulatory factors on APCs, such as dendritic cells; as a result, the APCs fail to engage the stimulatory receptor CD28 and instead activate the inhibitory receptor CTLA-4 on effector T cells. This not only prevents sensitization but also may induce long-lived unresponsiveness in tumor-specific T cells.
Draw a diagram showing the activation of immunoregulatory pathways
N/A Lecture 2 Slide 40
What is hallmark 8?
Hallmark 8. Altered tumour metabolism
What are tumor cells primary fuel source?
- Burn glucose as fuel, preferentially (Even in the presence of O2, cancer cells can limit their nrg metabolism largely to glycolysis (which is usually used by normal cells only in anaerobic conditions), leading to a state that has been termed “aerobic glycolysis”.
What technique allows us to visualize tumour cell’s large glucose usage?
Diagnostic imaging (18F –deoxyglucose PET/CT imaging)
Why is it advantageous for a cancer cell to rely on seemingly inefficient glycolysis (which generates 2 molecules of ATP per molecule of glucose) instead of oxidative phosphorylation (which generates up to 36 molecules of ATP per molecule of glucose)?
Aerobic glycolysis provides rapidly dividing tumor cells with metabolic intermediates that are needed for the synthesis of cellular components, whereas mitochondrial oxidative phosphorylation does not.
How does the Warburg effect work?
Metabolic reprogramming is produced by signaling cascades downstream of GFRs, the very same pathways that are deregulated by mutations in oncogenes and tumors suppressor genes in cancers.
Draw diagram of quinescent cell vs. growing cell (normal or tumour)
N/A Lecture 2 Slide 43
What is autphagy?
Self + eating
Draw a diagram of autophagy
N/A Lecture 2 Slide 44
- Vesicle nucleation
- Vesicle elongation
- Docking and fusion (of autophagosome and lysosome)
- Vehicle breakdown and degradation
Describe autophagy’s role in cancer development and progression.
Early stages
- senescence
- genomic stability
- reduction of inflammation
- removal of damaged organelles
- reduction of oxidative stress
- p62 degradation
Late stages
- resistance to therapy
- tumor relapse
- dormancy
- tumor metastasis
- fuels tumor metabolism
- tumor progression: resistance to hypoxia, nutrient deprivation
We have so far reviewed the hallmarks of cancer as _____ _______ capabilities that allow cancer cells to survive, proliferate, and spread; These functions are acquired in different tumor types via distinct mechanisms and at various times during the course of multistep _____.
We have so far reviewed the hallmarks of cancer as ACQUIRED FXNAL capabilities that allow cancer cells to survive, proliferate, and spread; These functions are acquired in different tumor types via distinct mechanisms and at various times during the course of multistep TUMORIGENESIS.
The acquisition of the hallmarks of cancer are made possibly via what two ENABLING CHARACTERISTICS
- Tumor-promoting inflammation
2. Genomic instability
What is hallmark #9
Cancer-enabling inflammation
What are the 6 cancer-enabling effects of inflammatory cells and resident stromal cells
- Release of factors that promote proliferation (e.g. EGF, proteases that can liberate growth factors from the ECM)
- Removal of growth suppressors
- Enhanced resistance to cell death (e.g. integrins released by macrophages inhibit anoikis)
- Inducing angiogenesis (e.g. release of VEGF)
- Activating invasion and metastasis (proteases released from macrophages foster tissue invasion by remodeling the ECM, while factors such as TNF and EGF may directly stimulate tumor cell motility. TGF-β may promote EMT)
- Evading immune destruction (immune-suppressive roles of microenvironment).
What is hallmark #10?
Genomic instability: Enabler of Malignancy
Each person experiences and repairs about ____ mutations, per day
40,000
Unlike RNA and protein, DNA must maintain its ____ over a lifetime
Unlike RNA and protein, DNA must maintain its INTEGRITY over a lifetime
What are the 5 causes of Genome damage?
- Inherited germline mutations: Genetic predisposition (Rb, p53, APC, CDKN2A, BRCA1/2)
- Environment (Carcinogens; UV & other irradiation; chemotherapeutic agents)
- Loss of function in genome maintenance/repair (BRCA, XRCC, MSH, p53)
- Infections (Viral: HPV - cervical cancer; Bacterial: H. pylori - stomach cancer)
- Spontaneous de-amination, ROS, replicative accidents (anaphase bridges)
Slide 49
N/A
Which hallmark is first acquired in hereditary cancers?
Genome instability and mutation
Which hallmark(s) is first acquired in hereditary cancers?
- Sustaining proliferative signaling
- Evading growth suppressors
What is one therapeutic approach to each of the 10 hallmarks?
- Sustaining proliferative signaling
- EGFR inhibitors - Enabling replicative immortality
- Telomerase inhibitors - Inducing angiogenesis
- Inhibitors of VEGF signaling - Activating invasion and metastasis
- Inhibitors of HGF/c-Met - Resisting cell death
- Proapoptotic BH3 mimetics - Evading growth suppressors
- Cyclin-dependant kinase inhbitors - Genomic instability
- PARP inhibitors - Tumour-promoting inflammation
- Selective anti-inflammatory drugs - Avoiding immune destruction
- Immune activating anti-CTLA4 mAb - Deregulating cellular energetics
- Aerobic glycolysis inhibitors
Resistance is _____, _____ and under-sampled in clinic
multifactorial, heterogenous
From the following 6 acquired capabilities/hallmarks of cancer, give an example of a mechanism of how it may have been achieved
- Self-sufficiency in growth signals
- Insensitivity to anti-growth signals
- Evading apoptosis
- Limitless replicative potential
- Sustained angiogenesis
- Tissue invasion and metastasis
- Acquired capability: Self-sufficiency in growth signals
- Ex of mechanism: Activate H-Ras oncogene - Acquired capability: Insensitivity to anti-growth signals
- Ex of mechanism: Lose retinoblastoma suppressor - Acquired capability: Evading apoptosis
- Ex of mechanism: Produce IGF survival factors - Acquired capability: Limitless replicative potential
- Ex of mechanism: - Acquired capability: Sustained angiogenesis
- Ex of mechanism: Produce VEGF inducer - Acquired capability: Tissue invasion and metastasis
- Ex of mechanism: Inactivate E-cadherin
What are the 6 acquired cancer hallmarks
- cancer cells stimulate their own growth;
- they resist inhibitory signals that might otherwise stop their growth;
- they resist their own programmed cell death (apoptosis);
- they stimulate the growth of blood vessels to supply nutrients to tumors (angiogenesis);
- they can multiply forever;
- they invade local tissue and spread to distant sites (metastasis).
What are the 2 emerging hallmarks?
- Abnormal metabolic pathways
2. Evading the immune system
What are the 2 enabling hallmarks
- Chromosome abnormalities and unstable DNA
2. Inflammation
AACR 2017 Hallmarks: Hanahan and Weinberg
What are the emerging hallmarks discussed?
- “Shunted Terminal Differentiation” – to maintain cells in a stem and progenitor like state, is this a distinct capability?
- Lineage switching: NSCLC: in face of EGFR inhibitors, cells switch from epithelial to neuroendocrine phenotype
AACR 2017 Hallmarks: Hanahan and Weinberg
What are the emerging characterisitics discussed?
- Non-mutational epigenetic changes (plasticity)
- Not traceable to cancer cell alterations but rather due to epigenetic changes - the microbiome
- Most research has focused on the intestinal microbiota Bacteria can influence other hallmark traits by damaging DNA, modulating inflammatory responses
Stage IV cancer;; can the hallmarks help us?
N/A
Hanahan: Hypothesis: all of the 8 hallmarks are therapeutically targetable;; can we fine-tune co- targeting hallmarks to thwart adaptive resistance? What is the concern
- Concern is toxicity
- Can we target the right combination of hallmarks?
