Cancer Therapies

Question 1

Classical treatments for Cancer

Answer 1

1. surgery
2. Chemotherapy
3. Radiotherapy: High energy particles or waves

Question 2

Chemotherapies

Answer 2

Cytotoxic agents that block cell proliferation and induce cell death by targeting (ex) mitosis, inducing DNA damage, preventing DNA duplication, or activating immune system

Question 3

Anti-mitotic chemotherapies

Answer 3

Vinca alkaloids: Vincristine/vinblastin

• inhibit microtubule assembly/polymerization
• arrest mitosis in metaphase

Taxane: Paclitaxel

• stabilize microtubules and prevent from disassembling
• block mitosis progression and trigger apoptosis

Question 4

Chemotherapies inducing DNA damage

Answer 4

Topoisomerase:

• Regulates DNA supercoiling/unwinding of DNA
• Topoisomerase 1: ssDNA breaks and repair
• Topoisomerase 2: dsDNA breaks and repair
• They cut and pass DNA strands through

DNA intercalating agents can act as topoisomerase inhibitors by preventing religation –> mutagenesis or recombination –> activation of apoptotic program

Question 5

Chemotherapies inhibiting DNA synthesis

Answer 5

Anti-metabolites:

• purine and pyrimidine analogs create stereo-hinderance in growing DNA chain, block growth
• 5’ fluorouracil inhibits enzymes necessary to generate thymidine
• Methotrexate interrupts folate metabolism. Folate is necessary for DNA synthesis and repair

Question 6

Chemotherapy downsides

Answer 6

• Non-specific: intestinal toxicity, anemia, risk of infections, hair loss, hand-foot syndrome (PPE)
• Relapse common

Question 7

resistance

Answer 7

• p53 mutations highly implicated in the development of resistance

Question 8

BCR-ABL

Answer 8

• Blocking in Chronic myeloid leukemia was the 1st targeted therapy
• BCR-ABL caused by Philadelphia chromosome
• Activates MYC, Raf, AKT
• Gleevec prevents ATP from binding to BCR-ABL
• Patients relapse, due to mutations which change shape of ATP binding pocket, other inhibitors lead to stabilization.

Question 9

B-cell receptor signaling dependencies

Answer 9

B- Cell lymphomas
Chronic Lymphocytic Leukemia

Bruton’s Tyrosine Kinase is an important downstream mediators of B-Cell receptor signaling. Ibrutinib is an irreversible BTK inhibitor, but resistance appears after 1-2 years through C481S mutation in BTK

Question 10

Common genomic lessions in melanoma progression

Answer 10

• NRAS
• BRAF
• CDKN2A
• PTEN
• AKT
• TP53

Question 11

Vemurafenib

Answer 11

• Inhibits BRAF (V600E, 90% of BRAF mut in melanoma)

- Resistance acquired by expressing a different splicing variant

Question 12

Identification of mechanisms of resistance

Answer 12

• library sequencing of mutated protein
• sequencing resistant patients
• generating resistant cells, using high doses of the drug
• Genetic screen to predict resistance to therapy

Question 13

CRISPR Genetic Screens

Answer 13

• Cas9 induces dsDNA breaks
• Cas9 induces DNA repair by NHEJ or HDR, but host repair organisms either generate small indels, or integrate homologous donor DNA

Question 14

PI3K-AKT-mTOR as a target

Answer 14

• PI3K inhibitor idelasilib inhibits a specific isoform PI3Kδ
• mTOR: mammalian target of rapamycin, there are mTORC1 inhibitors and mTORC1/2 dual inhibitors, rapamycin is the original inhibitor

Question 15

Cell cycle can be inhibited by specific inhibitors of CDK4/6, for example

Answer 15

resistance occurs through mutation of inhibitor binding domain, or upregulation of other cyclins.

Question 16

Nutlins

Answer 16

MDM2 inhibitors, prevent MDM2 from inhibiting p53.

Question 17

Players in immunotherapy

Answer 17

• B cells
• T cells
• NK cells
• Macrophages
• Dendritic Cells

Question 18

B cells

Answer 18

• Upon double signal (Helper T cell signal + BCR activation) become plasma cell and release Antibodies
• Activated B cells proliferate and undergo affinity selection, and class switching.
• Dormant B cells reside in dark zone of Be cell follicle.

Question 19

Lymphoma

Answer 19

B or T cell proliferation in the lymphoid organs

Question 20

Leukemia

Answer 20

High levels of undifferentiated B and T cells circulating in the blood

Question 21

NK Cells

Answer 21

Kills cells with different or missing MHC Class I. Includes: transplanted cells, cells under viral infection, transformed cells

Question 22

Macrophages

Answer 22

APC of the innate immune system

Question 23

Dendritic cells

Answer 23

APC, mediator of innate and adaptive immune responses

Question 24

MHC I antigen presentation pathway

Answer 24

Endogenous antigen is processed by proteasome, imported to Endoplasmic reticulum where it binding to MHC Class I, which is exported to cell surface.

All cells have MHC I

Question 25

MHC II antigen presentation pathway

Answer 25

Exogenous antige and endogenous antigen are broken down in endocytic route. Meet MHC II in endoplasmic reticulum (?) and are exported to the membrane

Question 26

Advantages of the adaptive immune system

Answer 26

Stronger reaction to specific threats. Has long term memory.

Question 27

Mediators of the innate immune system

Answer 27

1. Macrophages: Pathogen uptake and elimination 2. Inflammatory cytokines: Inflammatory reaction and shock 3. Interferons: Attack on virus, autoimmunity. PAMPs activate TLR, which lead Dendritic cells to potentiate T cells through antigen presentation and cytokine release., as well as activate innate immune system through release of inflammatory cytokines (2) and interferons (3).

Question 28

Adaptive immune response through helper T cells:

Answer 28

MHC I activation: secrete INF-γ, stimulate killer T (CD8+) directly. MHC II activation: secrete IL-4, which activates B cells, leads to antibody production, leads to opsonization, activation of NK cells through FC receptor

Question 29

Rituximab

Answer 29

An anti-CD20 antibody for B-cell lymphoma. - Activates NK cells through Fc receptors, leading to tumor killing. - Activates complement - Induces apoptosis directly (through grouping of surface CD20?)

Question 30

Immune tolerance

Answer 30

- T-reg cells protect the body from auto-immune disease, release IL10/TGF-β, and inhibit T-cell activation - Autoimmunity occurs when T-reg activity is decreased. - Self tolerance occurs largely through recognition of MHC complexes, tumors cannot be transplanted into allogeneic host.

Question 31

Tumor microenvironment

Answer 31

- Also composed of immune infiltrate and cancer-associated fibroblasts

Question 32

Immune desert tumors

Answer 32

- Tumors that don't present antigens - Characterized by high mutation rates or high chromosomal changes. - May hide antigen presentation by suppressing or mutating MHC I (β2m subunit), mimic function of T regs by releasing inhibitory cytokines (IL-10, TGFβ) - Copy number changes are not immunogenic. - Strategy: mutate proteins to be recognized as non-self antigen, activate immune response, use immune cells without TGFβ receptor

Question 33

TGFβ

Answer 33

Immune cells with TGFβ receptor apoptose upon TGFβ binding | - Strategy for Immune desert: make immune cells without TGFβ receptor

Question 34

Checkpoint inhibitors

Answer 34

- anti-CTLA4 - anti- PD1 - anti-PDL1

Question 35

CTLA-4

Answer 35

Blocks T cell activation by blocking B7 coactivation

Question 36

PDL-1

Answer 36

expressed by tumor cells and DC to prevent killing. Neutralizes T cells.

Question 37

CAR

Answer 37

Engineered with synthetic receptor domain (single chain variable fragments), costimulatory domains (CD28) and signaling domain (CD3ζ) - T cells are processed ex-vivo with gammaretroviral vector encoding CAR gene.