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Clinical Application of Cancer Cell Biology
1. Cell cycle check points
2. Cell senescence
3. Signal transduction pathways
4. Epigenetic influences
5. Apoptosis
6. Tumor angiogenesis
7. Cancer stem cell
Characteristic Features of Cancer
• Characteristics
– Unregulated cell growth
– Tissue invasion/metastasis
• Cancer is genetic disease
– Mutations in several different genes.
• Cell proliferation, survival • DNA repair
• motility, invasion • angiogenesis
Phenotypic Characteristics of Malignant Cells (I)
• Deregulated cell proliferation
– Release of supression(Rb, p53) – Oncogene activation(Ras, Myc)
– Aberrant cell cycle control( loss of normal checkpoint response)
• Failure to differentiate
– Arrest at a stage prior to terminal differentiation • In leukemia due to chromosomal translocation
• Loss of normal apoptosis pathways
– Inactivation of p53, increases in Bcl-2 family members
• Genetic instability
– Microsatellite instability(MIN), chromosomal instability(CIN) – Defect in DNA repair pathways
• BRCA1/2, p53, mismatch repair gene(MMR)
• Loss of replicative senescence
– Normal cell stop dividing after 25-50 doublings – Arrest is mediated by the Rb and p53 pathways
Phenotypic Characteristics of Malignant Cells (II)
• Increased angiogenesis
– Increased gene expression of proangiogenic factors
• VEGF, FGF, IL-8
• Invasion
– Loss of cell-cell contacts (gap junctions, cadherens)
– Increased production of matrix metalloproteinases (MMPs) – Form of epithelial to mesenchymal transition(EMT)
• Metastasis
– Spread of tumor cells to lymph nodes or distant site
• Evasion of the immune system
– Downregulation of MHC class I & II molecules – Induction of T cell tolerance
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Genetic Events in Colon Carcinogenesis
normal early adenoma
Intermed adenoma
late
adenoma carcinoma metastasis Microsatellite Instability (MIN)/Chromosomal Instability (CIN)
APC inactivation or -catenin activation K-RAS or BRAF activation SMAD4 or TGF II inactivation P53 inactivation Other alteration
Therapeutic application of pRB/p53
• pRB
– Loss of function
• Cancer cells enter a mitotic cycle
– Therapeutic application
• Selective CDK inhibitor
– Flavopiridol
– Phase II clinical trial in CLL
• p53
– Most common genetic alteration(>50%)
• Li-Fraumani familial cancer syndorme: germline mutation
– Compromise cell cycle arrest chromosome instability
– Therapeutic application
• Oncolytic viruses(adenovirus)
– Phase II clinical trial in H&N cancer
Gompertzian Tumor Growth
Chemosensitive period: small tumor burden maximal growth fraction
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Normal Somatic Cells
Normal Germ Cells or Cancer Cells
telomerase telomerase
Senescence
immortal
Senescence
• Reverse transcriptase activity of telomerase is a prime target
• Telomerase vaccines
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Therapeutic targeting of signal transduction pathways in cancer cells
STI571
“Imatinib”
Pathways activated by Bcr-Abl
Efficacy of Imatinib in CML
Chronic phase (n=532) Accelerated phase (n=235) Blast phase (n=260) Hematologic 95% 34% 7% cytogenetic 41% 17% 7%Imatinib vs Interferon+cytarbine, NEJM 348:11, 2003
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Imatinib
in c-kit
positive
GIST
After 8 months initial NEJM 347:472, 200211
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P<0.001
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erb-b1 EGFR HER1 neu Erb-b2 HER2 Erb-b3 HER3 Erb-b4 HER4 HRG (NRG1) Tyrosine kinase domain Ligand binding domain TransmembraneMendelsohn and Baselga. Oncogene. 2000;19:6550. Olayioye et al. EMBO J. 2000;19:3159.
Prigent and Lemoine. Prog Growth Factor Res. 1992;4:1. Harari and Yarden. Oncogene. 2000;19:6102. Earp et al. Breast Cancer Res Treat. 1995;35:115.
The EGFR/HER Family
Targets HER2 protein
High affinity (K
d= 0.1
nM) and specificity
95% human, 5% murine
Decreases potential
for immunogenicity
Increases potential for
recruiting immune effector
mechanisms
HER2 epitopes recognized by hypervariable murine
antibody fragment
Human IgG-1
Trastuzumab(Herceptin
®
)
Months 0.2 0 0.4 0.6 0.8 1.0 HER2-FISH(+) Months 0.2 0 0.4 0.6 0.8 1.0 Trast. + CT (n = 176) CT (n = 169) Probability of surv iv a l RR = 0.71 p = 0.007 0 10 20 30 40 50 20.0 mo 26.2 mo HER2-FISH(–) RR = 1.11 p = NS 0 10 20 30 40 50 19.8 mo 24.0 mo Trast. + CT (n = 50) CT (n = 56)
Trastuzumab Combination Pivotal Trial:
Overall Survival
Update of Mass. Proc Am Soc Clin Oncol. 2001;20:22a. Abstract 85.
Trastuzumab after Adjuvant chemothx
in HER2-Positive Breast Cancer
(HERA trial)
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Lancet 2010;376:687
Downstream of RTKs: Ras & PI3K
• Ras
– Mutation in 20% of human cancer • Pancreas, colon, lung, AML
– Therapeutic application • Farnesyl-transferase inhibitor
– Some activity in AML
• BRAF kinase inhibitor: vemurafenib
• PI3K
– Serine/threonine kinases Akt & PDK1 – Activated in 30-40% of human cancer
• Breast, colon, brain, gastric, ovary
– Therapeutic application
• mTOR inhibitor – temsirolimus
– renal cell carcinoma
Normal BRAF is activated by interaction with KRAS. In melanoma, BRAF V600 mutant proteins have high unregulated kinase activity that impels cell proliferation and tumor growth.
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NEJM 364;26, 2011
PR: 48%
(Results)
Patients who received temsirolimus alone had longer
overall survival (hazard ratio for death, 0.73; 95%
confidence interval [CI], 0.58 to 0.92; P = 0.008) and
progression-free survival (P<0.001) than did patients who received interferon alone.
Overall survival in the combination-therapy group did not differ significantly from that in the interferon group (hazard ratio, 0.96; 95% CI, 0.76 to 1.20; P = 0.70).
N Engl J Med 2007;356:2271-81
Tumor angiogenesis
• Angiogenic switch
– Ability of tumor to promote formation of new capillaries
– Stimuli for angiogenesis
• Hypoxia, inflammation, genetic lesions
– Steps of angiogenesis
• Stimulation of endothelial cells(ECs) by growth factor • Degradation of ECM by proteases
• Proliferation of ECs and migration into tumor • Eventual formation of new capillary tubes
• Trophic angiogenic molecules
– VEGF
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Angiogenesis is involved throughout
tumor formation, growth and metastasis
Adapted from Poon, et al. JCO 2001
Stages at which angiogenesis plays a role in tumor progression
Premalignant stage Malignant tumor Tumor growth Vascular invasion Dormant micrometastasis Overt metastasis (Avascular tumor) (Angiogenic switch) (Vascularized tumor) (Tumor cell intravasation) (Seeding in distant organs) (Secondary angiogenesis)
Knowledge of the molecular events governing tumor angiogenesis has led to a number of therapeutic strategies to block tumor blood vessel formation
Antiangiogenic therapy
• Bevacizumab
– Colon, lung, breast, renal cell cancer – Combination with chemotherapy
• Single agent activity in RCC
– Mechanism
• Normalization of blood flow in tumors enhance the delivery of cytotoxic
agents
• Inhibition of growth of new tumor vessels nutritional deprivation
tumor cell death – Side effect
• Hypertension, arterial thromboembolic events, hemorrage, bowel
perforation
• Sunitinib
– Multitarget: VEGFR, PDGFR, c-kit receptor
– RCC, GIST • Sorafenib
– Multitarget: VEGFR, PDGFR, Raf kinase inhibitor
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P<0.001
Molecular Pathways & Targeted Therapies in RCC
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Epigenetic Changes in Cancer
Alteration of chromatin structure: • Methylation of CpG islands
• Modification of histones by acetylation
Epigenetic change
• Epigenetically silenced
– Pancreatic cancer, multiple myeloma
• Methylation of p16ink4a promotor pRb nonfunctional
– Renal(VHL), breast(BRCA1), colon(STK11)
• Acute promyelocytic leukemia
– PML-RAR fusion protein
• Bind to promotor and recruits HDAC inhibit gene expression – ATRA
• Release of HDAC activity
• HDAC inhibitor
– Vorinostat: cutaneous T cell lymphoma
• Reverse the hypermethylation of CpG island
Apoptosis
• Extrinsic pathway
– TNF receptor family(
Fas, DR4, DR5), Fas ligand, TRAIL– Caspase-8
• Intrinsic pathway
– Death inducing signals
– SMAC(second mitochondrial activator of caspases)
• Therapeutic application
– Targeting of antiapoptotic Bcl-2 family member
– Targeting DR4 & 5
• Recombinant human TRAIL
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Cancer Stem Cell
• Unlimited self renewal • Proliferate extensively • Less vulerable to
chemotherapy or radiation
– Slow cell cycle
– High expression of Bcl-2 families and MDR family
Senarios Involving Cancer Stem Cells
Bench to bedside: Translational research
Application of basic
scientific discoveries
Generation of scientific questions
based on clinical observations
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Advances in Cancer Therapy
Surgery/Radiation Local Control
Combination chemotherapy Improved response rates
Adjuvant chemotherapy Induces cures
Dose intensity Augments adjuvant Rx
Molecularly directed Rx’s: Increase specificity
Molecular guided therapies: Optimized treatments
“Personalized Treatment based on Molecular Profiles”
Multigene Assay to Predict Recurrence of
Tamoxifen-Treated, Node-Negative Breast Cacner
Soonmyung Paik, MD., NSABP
N Engl J Med 2004;351:2817
16 cancer related genes(selected from 250 candidate genes) 5 reference genes
NSABP trial B-20, B-14(2892 patients) Paraffin block, RT-PCR(Oncotype DX assay)
Prediction of Survival in Diffuse Large-B-Cell Lymphoma Based on
the Expression of Six Genes
Izidore S. Lossos, Stanford University
N Engl J Med 2004;350:1828
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The Use of Moleular Profiling to Predict Survival after Chemotherapy for Diffuse
Large B Cell Lymphoma
N Engl J Med 2002;346:1937
“Lymphochip”(12,196 clones)
-genes for lymphoid cells
-Genes for cancer/immune function
Personalized Treatment
Tailored therapy
• Treat the populations
Treat the individual!
• Treatment rationales come from
– the basic biology of each patient (variation)
