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Molecular Diagnostics and Targeted
Therapies in Solid Tumors
Gregory J. Tsongalis, Ph.D.
Professor of Pathology
Director, Molecular Pathology
Dartmouth Medical School
Dartmouth Hitchcock Medical Center
Norris Cotton Cancer Center
Lebanon, NH
1.4M New Cancers (US)
H&E for Morphology
Further Diagnostic Work-up
• Imaging (CT, MRI, PET)
• Immuno (IHC), molecular,
• Proteomic
Therapeutic
management
Current Patient Management Is Based on
Diagnosis
Hallmarks of Human Cancer
Evading
apoptosis
Self-sufficiency in
growth signals
Tissue invasion
and metastasis
Limitless replicative
potential
Sustained
angiogenesis
Insensitivity to anti-
growth signals
Gene Mutations Cause Cancer = New Biomarkers
Single gene = Single mutation = Cancer
Nothing Else Looks Like This!
Susan G. Komen Race for the Cure - Indianapolis
Traditional Processing of Tissues
ImmunoHistoChemistry
(IHC)
• Inexpensive
• Subjective scoring
• Semi-quantitative
• Protein target may be affected
by tissue processing
Traditional Technologies for Pathology Workup
• Fluorescent labeled DNA probes
hybridize to target
• Hybridized DNA probes fluoresce,
giving off brightly lit signals that are
easily viewed and analyzed
Fluorescence in situ
Hybridization (FISH)
EGFR Exon 21
Electropherogram
KRAS Gly13Asp BRAF V600E
Current Clinical Mutation Analysis Data
Evolving Molecular Technologies
-50
50
150
250
350
450
1 5 9 13 17 21 25 29 33 37 41
Cycle
Sig
na
l
1000000
100000
10000
1000
100
10
neg. control
0
1
2
3
4
5
0 1 2 3
Fam (fluorescence)
Vic
(fl
uo
rescen
ce) SNP Genotyping Assay
Real Time PCR:
1. All specimen types
2. Increased sensitivity and specificity
3. Quantification possible
4. TAT = 2-3 hours
qBiomarker™ Somatic Mutation PCR Array: Human EGFR Pathway
Symbol COSMIC ID nt change AA change Known EGFR
Mutation Known KRAS
Mutation Known BRAF
Mutation BRAF 476 c.1799T>A p.V600E - - + EGFR 12366 c.2572C>A p.L858M + - - KRAS 532 c.38G>A p.G13D - + -
qBiomarker™ Somatic Mutation PCR Array Data
Genomic Approaches to Clinical Oncology
Tumor classification
Prognostic markers
Predictive indicators of drug response
New therapeutics
Monitoring disease
Susceptibility to cancer
Cystic Fibrosis
• Single gene disorder (CFTR - 1989)
• 27 exons, 23 kb
• F508
• >1,800 mutations
• Clinical heterogeneity
• Screening program – 2001
• Treatment of symptoms
• VX-770
– small molecule drug
– G551D specific (4%)
• VX-809 - F508 specific (90%)
• Challenges:
– Limited efficacy
– Emergence of resistance
– Unexpected toxicities
Therapies in Human Cancer
• The right treatment
for the right person
at the right time
Trial and Error
Personalized Medicine Current Practice
Personalized Medicine
One size fits all
• Trial and error
Personalized for the Individual Patient
Optimal drug response
Reduced adverse effects
Systemic response
Personalized Medicine Includes Predicting
Response to Targeted Therapies
Pharmacogenomics: Targeted Therapy
Most targeted therapies are directed against genes or gene products
found only in tumor cells – acquired or somatic genetic variants
O
Z
N
Tamoxifen
Targeted Therapy
HER History
1970s 2000s 1990s 1960s 1980s
EGF identified First HER-targeted MAb, trastuzumab (Herceptin®) approved for HER2+ MBC
Gefitinib (Iressa®) approved as
monotherapy for patients with
locally advanced or metastatic NSCLC
HER-targeted
therapies being explored in wide range of human
cancers
Overexpression of HER1/EGFR
reported in cancer cells
Monoclonals
identified
Small molecule
TK inhibitors identified
HER1/HER2
overexpression correlates with poor prognosis
Transmembrane structure of HER2 monomer
Extracellular domain
(632 amino acids)
Ligand-binding site
Intracellular domain
(580 amino acids)
Tyrosine kinase activity Cytoplasm
Plasma
membrane
Increased HER2 production
Normal Amplification/Overexpression
Cytoplasm
HER-2/neu receptor
protein
Cytoplasmic
membrane
Nucleus
HER-2/neu DNA
HER-2/neu
mRNA
Targeted Therapy
Anti-monoclonal Antibody and Anti-TKI Therapy Are Directed
Trastuzumab
(Herceptin) Lapatinib
(Tykerb)
Detecting HER-2
HER-2 Protein
HER-2 Genes Protein expression by IHC
Gene amplification by FISH
CML: The New Poster Child for Targeted
Therapy
• Diagnostic
• Therapeutic monitoring
• Resistance
THE BCR-ABL CHIMERIC ONCOPROTEIN
p185 (aa 426) BCR
BCR p210 (aa 902-927) NLS
Y Kinase SH3 SH2
NES
ABD DBD ABL
- Forms Dimers and Tetramers
- Constitutive Tyrosine Kinase Activity
- Exclusively Cytoplasmic
Therapeutic Options for CML
• ChemotherapyHydroxyurea, Busulfan
• Interferon-alpha
• Allogeneic Stem Cell Transplantation
• Gleevec® (Imatinib Mesylate)
Gleevec®-Tyrosine Kinase Inhibitor
Goldman JM. Lancet. 2000;355:1031-1032.
Bcr-Abl
ATP
Substrate
STI571
Y = Tyrosine
P = Phosphate
Bcr-Abl
Substrate
P P P
P
ATP in its specific binding site in the kinase domain of the protein is able to
phosphorylate tyrosine residues (Y) on selected substrates. The
phosphorylated substrate then binds with other molecules and activates
downstream pathways in leukaemogenesis. STI571 occupies the ATP pocket in
the BCR-ABL kinase domain and substrates cannot be phosphorylated.
Therapeutic Goals in CML
• Hematologic response: normal PB values and spleen size.
• Cytogenetic response: reduction of Ph+ cells in the blood or bone marrow. Complete = 0% Ph+ cells Partial CR = 1-35% Ph+ cells Minor CR = 36-95% Ph+ cells
• Molecular response: reduction or elimination of bcr-abl mRNA in marrow or PB.
Detection of BCR-ABL Positive for BCR-ABL
0
100
200
300
400
500
600
0 10 20 30 40 50
Cycles
Flo
ure
scen
ce
Internal Control
BCR-ABL
>90% Imatinib resistance is due to reactivation of the bcr-abl
tyrosine kinase activity.
Persistance of bcr-abl kinase activity in the presence of imatinib
is mostly due to selected point mutations.
Imatinib Resistance
Kantarjian HM et al. Ann Intern Med 2006;145:913-923
Mutations That Induce Resistance to Imatinib
48 MUTATIONS
Other TKIs
KRAS & EGFR Testing:
predicting response to targeted therapy
in Colon and Lung Cancers
Prognostic vs Predictive Markers
• Prognostic marker- indicator of survival
independent of therapy; indicator of tumor
aggressiveness
• Predictive marker- indicator of response to
therapy, such as PFS or OS; (or in some
cases prediction of severe toxicity)
EGFR and KRAS
• EGFR- epidermal growth factor receptor, ErbB1
– Cell-surface receptor tyrosine kinase
– Activating mutations confer susceptibility to small
molecule TKI’s
– Resistance mutations also occur
• KRAS- Kirsten rat sarcoma virus (human homolog)
– GTP binding protein; signal transduction downstream of
cell surface receptor
– Activating mutations (reduced GTPase activity) negate
the requirement for upstream receptor activation
Mechanisms of EGFR Inhibition
Inhibition Strategies:
• EGFR-TK inhibitors
• Anti-EGFR mAb
inhibitors
mAb
Inhibitors
, Panitumumab
EGFR and Targeted Therapies
EGFR EGFR activating mutations confer susceptibility to small molecule TKI’s in
NSCLC.
Two common mutations account for >80% of EGFR mutant alleles. In frame del exon 19 and point mutation exon 21 (L858R)
Receptor L-domain
Receptor L-domain
Furin-like domain
Kinase domain
Transmembrane region E18
E19
E20
E21
Substitutions
In-frame deletions
Duplications/insertions
Substitutions
Substitutions
(L858R)
6%
6%
46%
42%
Lassus H, et al. J Mol Med. 2006;84:671-681. Lacroix L, et al. Int J Cancer. 2006;118:1068-1069. Stadlmann S, et al. Mod Path. 2006;19:607-610. Schilder RJ, et al. Clin Cancer Res. 2005;11:5539-5548.
KRAS Activating Mutations
• Found in 30-50% of CRCa’s
• Associated with smoking in NSCLC
• Occur most often in codons 12 and 13
• Missense mutations (change of amino acid)
• 7 common mutations, account for at least
95% of all identified
• A few mutations in other locations have
been reported ex: codon 61
KRAS Mutations
Lievre et al., J Clin Oncol 2008 (Jan);26:374
• Cetuximab – monoclonal Ab to EGFR
• KRAS mutations associated with resistance to
Cetuximab
Amado et al., J Clin Oncol 2008 (Mar);26:1
• Panitumamab – monoclonal Ab to EGFR
• Response associated with wild type KRAS
KRAS mutation testing
• DNA extracted from archival FFPE tumor sample (typically
primary tumor)
• Original kit (DxS, European) used allele-specific PCR
• Detection limit: 1% mutation in wild-type background
• Detects 7 mutations in codons 12 and 13
– Gly12Asp Gly12Cys
– Gly12Ala Gly12Arg
– Gly12Val Gly13Asp
– Gly12Ser
Allelic Discrimination for KRAS Mutations
GLY12ARG, 34G>C GLY12ASP, 35G>A
GLY12CYS, 34G>T GLY12ALA, 35G>C
KRAS Mutation Detected in FFPE Tumor
Codon
12
Codon
13
Gly Gly
G>A mutation
(Gly12Asp)
Correlating Molecular Findings with Pathology
Chen H. et al. Correlation of polypoid colorectal adenocarcinoma with
pre-existing adenomatous polyps and KRAS mutation.
Cancer Genet, Apr 204:245-251, 2011
Adenomatous polyp
with villous architecture
Pre-existing adenomatous
polyp with
villous architecture
Invasive adenocarcinoma
with ulceration
Correlating Molecular Findings with Pathology
A Changing Paradigm?
• Patient #1
– Poorly differentiated
– Aggressive
– Pos for therapeutic
targets
• Patient #2
– Well-Moderately
differentiated
– Less aggressive
– Neg for therapeutic
targets
Conclusions
• Targeted therapies offer a better way to
destroy cancer cells beyond the typical
chemotherapy
• Knowledge of tumor cell biology will lead to
more treatments against various pathway
constituents
• Our field is changing rapidly and so will our
roles
What if………..
DHMC Molecular Pathology Laboratory and
Translational Research Program
Samantha Allen
Claudine Bartels, Ph.D.
Heather Bentley
Betty Dokus
Susan Gallagher
Carol Hart
Arnold Hawk
Joel Lefferts, Ph.D.
Rebecca O’Meara
Elizabeth Reader
Mary Schwab
Laura Tafe, M.D.
Brian Ward
Brendan Wood
Eric York