Transcript TARGETING THE TARGETS: THE EGFR AND HER2 STORIES

Targeting the Targets:
the EGFR and HER2 stories
Dr. Mark Basik
Potential Conflict of Interest
• Research Grant / 2006-2008
– Chemokine Therapeutics
TARGETING THE TARGETS: THE
EGFR AND HER2 STORIES
Mark Basik MDCM
Segal Cancer Center
McGill University
OUTLINE
• EGFR and colorectal cancer
• HER2 and breast cancer
The HER family of receptors
Fig 1. Mechanisms of receptor activation
Mendelsohn, J. et al. J Clin Oncol; 21:2787-2799 2003
Copyright © American Society of Clinical Oncology
Fig 2. Epidermal growth factor receptor signaling
Mendelsohn, J. et al. J Clin Oncol; 21:2787-2799 2003
Copyright © American Society of Clinical Oncology
EGFR as target
• 65-70% colorectal
cancers express
EGFR (IHC)
• Correlation with
poor prognosis and
more aggressive
disease
Dakocytomation
EGFR as target
Anti-EGFR antibodies
• Cetuximab (Imclone/BMS): chimeric molecule:
mouse MoAb vs ligand-binding site of EGFR+human
IgG constant region fragment
– Approved FDA 2004 for irinotecan-resistant metastatic
colorectal cancer
• Panitumumab (Amgen) :fully human IgG2 MoAb
– Approved FDA 2006 for resistant EGFR-expressing
metastatic colorectal cancer
EGFR expression not required for
response
Chung et al, JCO 2005
Phase II Pharmacogenomic
exploratory trial
• 111 patients with metastatic colorectal cancer were
enrolled in a trial of cetuximab monotherapy.
• Transcriptional profiling was conducted on RNA from
pre-treatment metastatic site biopsies from all
patients to identify genes whose expression
correlates with best clinical responses.
• EGFR, B-RAF and K-RAS mutation analyses and
EGFR gene copy number analyses were performed
on DNA from pre-treatment biopsies.
Affymetrix mRNA level
Figure 2: mRNA LEVELS OF EGFR LIGANDS EPIREGULIN AND AMPHIREGULIN
3500
Epiregulin
3000
CR/PR
SD
non-responders
2500
2000
1500
1000
Affymetrix mRNA level
500
0
7000
Amphiregulin
6000
5000
4000
3000
2000
1000
0
Subjects
Codons 12, 13 in exon 1
FFPE tissue samples
PLoS Med. 2005
KRAS mutations and
colorectal cancer
• Activating missense K-Ras mutations
– 40% colon cancers, 95% pancreatic cancers
• Approximately 90% of the activating mutations are found in
codons 12 (wild-type GGT) and 13 (wild-type GGC) of exon 1
and ~5% in codon 61 (wild-type CAA) located in exon 2 (8–
10).
• Previous studies from various countries have revealed
specific point mutations in codons 12 and 13. The most
frequently observed types of mutations are G>A transitions
and G>T transversions
Figure 4: K-Ras MUTATION ANALYSIS
3
27
26
24
Disease Control
Group
(11%)
Non-responders
(51%)
Mutant at K-Ras codon 12 or 13
Wild Type
b
high
low
Patients Free of Tumor Progression (%)
EREG
AREG
high
low
(days)
c
(days)
Patients Free of Tumor Progression (%)
a
Patients Free of Tumor Progression (%)
Figure 3: PROGRESSION-FREE SURVIVAL CURVES
K-RAS
mutant
wild type
Khambata-Ford
et al, JCO 2007
Time (days)
Figure 5: CETUXIMAB AND K-RAS MODULATE SIGNALING THROUGH EGFR PATHWAY
a
b
c
CLINICAL VALIDATION
• Predictive vs prognostic biomarkers
– Is the marker indicating merely bad disease
– How much of the drug effect is real?
• A randomized clinical trial can definitely establish
predictive value of biomarker
Original Article
K-ras Mutations and Benefit from Cetuximab in
Advanced Colorectal Cancer
Christos S. Karapetis, M.D., Shirin Khambata-Ford, Ph.D., Derek J. Jonker, M.D.,
Chris J. O'Callaghan, Ph.D., Dongsheng Tu, Ph.D., Niall C. Tebbutt, Ph.D., R. John
Simes, M.D., Haji Chalchal, M.D., Jeremy D. Shapiro, M.D., Sonia Robitaille, M.Sc.,
Timothy J. Price, M.D., Lois Shepherd, M.D.C.M., Heather-Jane Au, M.D., Christiane
Langer, M.D., Malcolm J. Moore, M.D., and John R. Zalcberg, M.D., Ph.D.
N Engl J Med
Volume 359(17):1757-1765
October 23, 2008
Kaplan-Meier Curves for Overall Survival According to Treatment
Karapetis CS et al. N Engl J Med 2008;359:1757-1765
Kaplan-Meier Curves for Overall Survival According to K-ras-Mutation Status among Patients
Receiving Supportive Care Alone
Karapetis CS et al. N Engl J Med 2008;359:1757-1765
Conclusion
• Patients with a colorectal tumor bearing
mutated K-ras did not benefit from
cetuximab, whereas patients with a
tumor bearing wild-type K-ras did benefit
from cetuximab
• The mutation status of the K-ras gene
had no influence on survival among
patients treated with best supportive
care alone
BRAF mutations
• Exclusive of KRAS mutations in CRC
• 13% of CRCs
Fig 1. KRAS and BRAF mutations correlate with lack of response to treatment with monoclonal
antibodies targeting epidermal growth factor receptor
Di Nicolantonio, F. et al. J Clin Oncol; 26:5705-5712 2008
Copyright © American Society of Clinical Oncology
Figure 1. Kaplan-Meier cumulative PFS on the basis of PIK3CA and KRAS mutational
status and PTEN protein expression in mCRC patients treated with panitumumab and
cetuximab
Sartore-Bianchi, A. et al. Cancer Res 2009;69:1851-1857
Copyright ©2009 American Association for Cancer Research
WHY KRAS?
KRAS mutation detection
• FFPE: use enough template DNA
• Direct sequencing = gold standard
(min 20-50% mutant/WT ratio)
• HRMA to be followed by sequencing
February 2nd, 2009
Anti-EGFR TKIs (lung cancer)
INTRINSIC RESISTANCE
TO CETUXIMAB
• MUTATIONS & MUTATIONS
• LOW AUTOCRINE SIGNALING
Acquired resistance to
cetuximab
• Cell line model (NSCLC) 6 months of
cetuximab
• Increased steady-state EGFR expression
due to altered traffic and degradation
• Activation of HER2, HER3 and cMET
• No clinical trial material for acquired
resistance
Wheeler DL et al. Oncogene 2008
ErbB-2/Her-2/neu amplification in breast
cancer
17
• 20-30% Amplification
• 17q12
• Associated with:
1) Adverse prognosis
2) Aggressive tumors
• Effect: cell proliferation,
survival, angiogenesis,
migration
ErbB-2
TRASTUZUMAB
(HERCEPTIN)
• Humanized anti-ErbB-2 monoclonal
antibody
• Recognizes extracellular portion of ErbB-2
• Mechanisms of Action
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–
–
–
–
????
Receptor endocytosis and degradation
Decreased AKT signaling (PTEN activation)
ADCC
Induction of apoptosis
Cell cycle arrest
Inhibition angiogenesis
Trastuzumab response rate
• Monotherapy (metastatic breast cancer):
12-34% response
• Median duration 9 months
• Most patients with initial response acquire
resistance after 1 year
Mechanisms of intrinsic resistance
1.
Mechanisms involving ErbB-2:
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•
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Direct implication of ErbB-2 function or localization
Inhibition of trastuzumab binding to ErbB-2 (e.g. MUC4)
Increased circulating ECD-HER2 (not clinically validated)
Increased expression of p95 form of HER2 (partially
clinically validated)
Mechanisms of intrinsic resistance
2. Mechanisms involving altered downstream or
compensatory signaling pathways
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•
•
•
•
Downregulation of p27
Loss of PTEN (expression/mutation) (partially clinically
validated)
Activation of IGF-1R
Upregulation of TGF-alpha
Increase in heat shock protein function
siRNA screen:
PIK3CA/PTEN
Berns, Cancer Cell 2007
INTRINSIC vs ACQUIRED
• Is it the same mechanism?
• The issue of cell number?
– Few resistant cells: acquired
– Many resistant cells: intrinsic
• More difficult to study acquired
Resistance both in vitro and clinically:
• No clinical material
Chan CT et al, Breast Cancer Res Treatment, 2005
AKT activated in Herceptinresistant cells
BT
0.2 mM Hcptn
1 mM Hcptn
24 hrs
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+
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0.2J
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+
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+
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1E
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+
pAkt
Akt
a-tubulin
Acquired resistance to herceptin: in vivo
Ritter et al, CCR 2007
DARPP-32 expression in trastuzumab-resistant cells
0.2J* 0.2J
BT
0.2 mM Hcptn
1 mM Hcptn
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+
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1E*
1E
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+
+
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+
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+
DARPP-32
a-tubulin
DARPP-32
• Dopamine and cAMP regulated
phosphoprotein of MW 32
• Protein phosphatase 1 inhibitor (PP1)
• Protein kinase A inhibitor (PKA)
T-Darpp is required and sufficient for
resistance to trastuzumab in BT-474 cells
Hamel S et
al. Breast
Cancer Res
Treat 2009
DARPP-32 activates AKT
Hamel S et al. Breast Cancer Res Treat 2009
DARPP-32 expression in primary breast
cancers
DARPP-32: anti-apoptotic effect (AKT-BCL2)
Belkhiri et al, Cancer Res. 2008
Hamel S et al. Breast Cancer Res Treat 2009
Other causes of acquired
resistance to herceptin
• Co-operating factors
– CXCR4/DARPP32
– EGFR/DARPP32
• Context dependence
(ER+ vs ER-)
GENE ONTOLOGY
Term
SKBR3 UP
P value gene
changed
BT474 1F
P value gene changed
Heat shock protein
binding
0.00
1.00
Alcohol metabolism
0.00
0.69
Wnt receptor
signaling
0.008
0.78
Lysosome/lytic
vacuole
0.02
0.83
Monosaccharide
metabolism
0.03
0.86
Unfolded protein
binding
0.04
0.87
Metal ion transport
0.91
0.00
Cysteine protease
inhibitor activity
1.00
0.00
cAMP mediated
signaling
1.00
0.01
Amine receptor
activity
0.61
0.02
HERCEPTIN RESISTANCE
• Intrinsic: Mutation + HER pathway
alterations
• Extrinsic: different pathways
activated
• Functional overlap
• AKT the common factor
LAPATINIB: resistance
• small molecule ErbB2 Tk inhibitor
• Intrinsic: PIK3CA mutations and PI3K
hyperactivation (Eichhorn et al, Cancer Res 2009)
• Acquired: activation of ER signaling (Xia et al,
PNAS 2006)
How to overcome acquired
resistance
• Target the resistance factor
– PI3K/mTor (e.g. NVP-BEZ235), geldanamycin
• Combine with vertical or horizontal
inhibitors (e.g. IGF-1R, mTOR…)
• CONTINUE anti-Her therapy
–
–
–
–
Lapatinib (affects MAPK > PI3K pathways)
Pertuzumab
Continue herceptin?
HER3 as a target
HER3: required for AKT-P
Hsieh and Moasser, Br J Cancer 2007
Continuing
Herceptin:
double clinical response
Von Minckwitz et al, Journal Clinical Oncology March 2009
Continuing anti-HER2
therapy?
Fig 4. (A and B) The colorectal cancer cell line DiFi was transduced with either an empty vector or a
BRAF V600E-encoding lentiviral vector
Di Nicolantonio, F. et al. J Clin Oncol; 26:5705-5712 2008
Copyright © American Society of Clinical Oncology
Tumor heterogeneity:
an essential component of acquired
resistance?
Moroni, Lancet Oncology 2005
The analysis of tumor
subclones
MOLECULAR PROFILING:
The cancer stem cell?
THANK YOU
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A. Bouchard
S. Hamel
C. Ferrario
A. Aguilar-Mahecha
D.Mauro
S. Khambata-Ford