Directed Therapies of Cancer Flashcards
What is the difference between chemotherapy and directed therapy?
chemotherapy is usually cytotoxic and kills normal and cancer cells, whereas directed therapy is usually cytostatic and normal cells survive therapy
How do directed therapies generally work?
- target a protein on tumor cells not found in normal cells
- target a protein that is mutated in cancer cells
- target overexpression of protein in cancer cells
- target DNA changes that are not found in normal cells
What are the uses of genetic/molecular/protein alterations in precision medicine?
- biomarkers for early diagnosis/screening of cancer
- biomarkers for monitoring response to treatment
- biomarkers for prognosis and to guide therapy
- biomarkers to identify those at risk for cancer (lifestyle changes and genetic counseling)
- identify targets for drug therapy
- identify targets for enhancing the delievery for cytotoxic drugs
- therapy for traditionally non-responsive cancers
- identify individuals who may benefit from therapies that may only work in a select group of patients
What are the types of target therapies?
- proteasome inhibitors
- signal transduction inhibitors
- apoptosis inducers
- gene expression modulators
- angiogenesis inhibitors
- cancer vaccines
- gene therapy
- monoclonal antibodies-toxic molecule delivery
- immunotherapies
- hormone therapies
What is Multiple Myeloma?
cancer of B-cells (plasma cells), monclonal plasma cells (PC) secrete monoclonal Ig infiltrate the bone bone marrow which results in organ dysfunction (CRAB= hyperCalcemia, Renal insufficiency, Anemia, Bone lesions) -> debilitation -> death
What are the target drugs used for Multiple Myeloma?
- PROTEASOME INHIBITORS
- IMMUNOMODULATING AGENTS
- HISTONE DEACETYLASE INHIBITORS (DACis)
- monoclonal antibodies
- chimeric antigen receptor (CAR) T cells
- selective inhibitors of nuclear export
- alkylators
- glucocorticoids
What is the use of 26S proteasome?
a large multi-protease complex that controls degradation of more than 80% of cellular proteins which is crital for cellular protein homeostatis
What drugs are Proteasome inhibitors for multiple myeloma?
- bortezomib (Velcade)
- ixazomib citrate (Ninlaro)
- carfizomib (Kyprolis)
What is the mechanism of action of Bortezomib (VELCADE)?
inhibits activation of beta5 >beta1 >beta2 subunits of the 20S proteasome core by forming complex with Threonine OH group at active site, reversible inhibitor of chymotypsin-like and caspase-like (less trypsin-like) activity -> inhibits proteolysis -> protein accumulation -> stress -> cell death
What is the mechanism of action of Ixazomib (NINLARO)?
dipeptidyl boronic acid-based inhibitor which targets beta5 > beta2, reversibly inhibits the chymotrypsin-like, trypsin-like and caspase-like activities at high concentrations with potencies similar to Bortezomib
may overcome resistance to Bortezomib
What is the mechanism of action of Carfilzomib (KYPROLIS)?
tetrapeptide epoxyketone inhibitor, irreversibly inhibits 20S proteasome subunit of 26S proteasome which predominantly inhibit beta5 (more potent than Bortezomib) and more selective for chymotrypsin-like activity than Bortezomib
What is the general mechanism of action of Proteasome inhibitors?
- inhibition of proteasomal degradation = misfolded proteins accumulate in cytosol and ER lumen inducing stress
- endoplasmic reticulum overload = ER-stress related apoptosis
- generation of excess oxygen = DNA damage induced cell death
- NF-kB signaling
How do Proteasome Inhibitors effect NF-kB signaling pathways?
the NF-kB pathway is regulated by protein IkB (inhibitor) which blocks nuclear translocation of the p50 (NF-kB1)/p65(RelA) heterodimer, NF-kB induces transcription of cancer causing genes, so Proteasome inhibitors have inhibitory effects on NF-kB activity= modulate transcription
What are the mechanisms of resistance of Proteasome Inhibitors?
- other signaling pathways
- P-glycoprotein (Pgp)/MDR1/ABCB1
- mutations in the catalytic beta5 subunit gene (PSMB5)
- non-standard 20S proteasome composition
What drugs are Immunomodulators for multiple myeloma?
- thalidomide
- lenalidomide
- pomalidomide
What is the major warning associated with Immunomodulators for multiple myeloma?
pregnancy, tetratogenic and embryo-fetal toxicity
What is the mechanism of action of Immunomodulators used in multiple myeloma?
CRBN E3 ubiquitin ligase complex marks proteins with ubiquitin for degradation, binding of Immunomodulators to this complex leads to the degradation of two key proteins, Aiolos (IKZF3) and Ikaros (IKZF1)= degradation of IKZF1/3= multiple myeloma cell death
What are the effects of Thalidomide?
degrades IKZF1/3 = toxic to tumor, inhibits pro-inflammatory cytokine production by monocytes (IL-6 inhibition= reduced myeloma cell adhesion to bone marrow, reduced TNF-alpha= reduced vascularization through decreased VEGF), activates and increases number of T cells and NK cells, T-cells increase cytokines (IL-2 and interferon)= enhances immune attack by NK cells on myeloma
What is the use of histones?
histones are proteins on chromatin that undergo methylation and acetylation (epigenetic regulation)
What drug is a Histone Deacetylase?
Panobinostat (Farydak)
What is the mechanism of action of Panobinostat (FARYDAK)?
histone deacetyltransferases (DACs) remove acetyl groups (acetylation of histones results in the opening of chromatin and consequently DNA = increased transcription of genes) -> in multiple myeloma closed conformation is preferred = reduced expression of tumor suppressor genes leading to growth and proliferation of cancer cells, Panobinostat inhibits histone deacetyltransferase (DACi)
What is the function of protein kinase?
phosphorylates proteins, enzyme chemically adds terminal phosphate group of ATP to: serine, threonine, and tyrosine= functionally alters target protein by regulating signal pathways
How do kinases regulate signaling pathways?
- activating/amplifying signaling
- alter location of target
- regulate interactions with regulatory proteins
What are the mechanisms of kinase activation in cancer?
- point mutation
- gene amplification
- fusion of kinase ligand
- gene fusion
How does BRAF V600E mutant kinase lead to metastatic melanoma?
BRAF V600E Mt kinase is constitutively active= MAPK= excessive cell proliferation and survival
What is the mechanism of action of Kinase Inhibitors for BRAF V600E mutation in metastatic melanoma?
block activation of MAPK -> G1 cell senescence = apoptosis
What drugs are Kinase Inhibitors for metastatic melanoma?
- Vemurafenib
- Dabrafenib
- Trametinib
- Cobimetinib
What is the molecular target of Vemurafenib?
BRAF V600E mutant kinase
What is the molecular target of Dabrafenib?
BRAF V600E mutant kinase
What is the molecular target of Trametinib?
MEK
What is the molecular target of Cobimetinib?
MEK
What is the role of non-receptor tyrosine kinase (NRTK) BCR-ABL signaling in cancer?
several pathways activated= increased cell proliferation, increased tumor survival, increased cell motility
What is the mechanism of action of Imatinib (GLEEVEC)?
inhibit BCR-ABL kinase activity
What drugs are BCR-ABL Tyrosine Kinase Inhibitors?
- Imatinib (Gleevec)
- Dasatinib
- Nilotinib
- Ponatinib
What is T315I in BCR/ALB mutant tyrosine kinase?
Thr315Iso (T315I) is the most vicioius mutant and accounts for 15% of relapse cases in chronic myloid leukemia (CML), cofers resistance to most approved tyrosine kinase (except Ponatinib)