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Prostate Cancer 101
Cell 616
Joshi Alumkal, MD
Assistant Professor of Medicine
May 6, 2009
Outline
• Background on prostate and prostate cancer
–
–
–
–
Androgens and AR
Epidemiology
Progression model
Molecular events
• Prevention
• Prostate cancer screening and diagnosis
• Treatment
– Localized prostate cancer
• Prognostication
– Metastatic prostate cancer
• Disease states model
– Pre/post hormonal therapy
• Is AR still a target after castration?
– Moving beyond hormones to target AR and prostate cancer
Background
Urinary bladder
Prostate
Rectal
surface
Rectum
Schematic depiction of the cell types within a human prostatic duct
Androgen
Receptor -
Androgen
Receptor +
Abate-Shen C., Shen M. M. Genes Dev. 2000;14:2410-2434
Prostate: An androgen-responsive
organ
• Prostate develops after puberty due to production of
testosterone and more active metabolite dihydrotestosterone,
which activate AR, the androgen receptor
– AR is a transcription factor which binds to consensus sequences and
turns on target genes such as PSA
• Prostate contributes to fertility by producing enzymes which
aid in fertilization of egg
• Testosterone depletion can prevent prostate formation and
cancer
– Eunuchs do not develop prostates and hence do not get
prostate cancer
• Testosterone administration has not been found to cause
prostate cancer in epidemiological studies or animals models
– May raise one’s PSA level though and prompt a diagnostic work-up
AR
Active HSP90
HDAC6
Ac
HDAC6
Ac
Alpha-tubulin
AR
ERG, PSA, and other AR target genes
Prostate Cancer Public Health
Impact/Demographics
• Prostate cancer is the most common cancer in men
– 187,000 new cases estimated for 2008
– 50,000 recurrences despite early detection and
treatment
• Prostate cancer is also the second most lethal cancer
– 27,050 deaths estimated for 2008
• Previously rare in men <50
• 1/5 men will be diagnosed in their lifetime
Race and prostate cancer
• African-Americans are at increased risk of
prostate cancer development and have more
aggressive disease
– Even when one accounts for screening and
treatment
– Unknown why
• Extremely rare in Asian populations…
– Until they move to the U.S.
Diet and Prostate Cancer
• High consumption of
broccoli is associated with
lower prostate cancer risk
– Kristal, Kolonel,
Giavanucci
– Why?
• High consumption of red
meat particularly charred
red meat is associated with
increased risk
– PhIP adducts
• Asians who move to US are
at increased risk
– Diet?
Viruses and prostate cancer
•Men with mutations in an anti-viral gene called RNase L more likely to
have this virus’ cDNA present in their cancer tissue
•No causal link demonstrated yet
Nelson, et al NEJM 2003
Different roads to gene silencing
Genetic
Epigenetic
+
-
+
+
+
= heritable control of gene
expression in the absence
of DNA sequence changes
•DNA methylation
•Histone methylation
Herman and Baylin NEJM 2003
Increase in ERG
Increase in EZH2
Increase in LSD1
Increase in Sonic
hedgehog
signaling
Nelson, et al NEJM 2003
ERG and Prostate Cancer
• Recent information suggests
that ERG is commonly upregulated in prostate cancer
• This gene is expressed
because it is linked to
TMPRSS2, which AR turns
on
• ERG over-expression leads
to enhanced invasion and
increases one risk of cancer
recurrence
• The VCaP prostate cancer
cell line harbors this
translocation
Science 2005
Transgenic ERG mice develop PIN
(prostate cancer precursor lesions)
Benign
PIN
Klezovitch , et al PNAS 2008
NEJM 2008
Prevention
•Inhibits 5-alpha-reductase enzyme which converts
testosterone to more active dihydrotestosterone agonist of AR protein
-Leads to loss of AR function
•Similar results presented last week at AUA meeting for related drug
dutasteride
Cumulative Incidence of Prostate Cancer Diagnosed in a Biopsy Performed for Cause or after an
Interim Procedure
Need to treat 16 men to prevent 1 cancer
Screening/Diagnosis
Percent of men
Prevalance of cancer (at autopsy)
Wayne State Univ: Dr. Wael Sakr
80
70
60
50
40
30
20
10
0
All m
20-29
30-29 40-49 50-59 60-69 70-79
Age (by decade)
Prostate cancer screening
• PSA is very sensitive and easy to do
– Widely adopted in 1989
– Led to surge in new diagnoses
• However,
– Many men will be diagnosed with non-life-threatening
cancers with which (rather than of which) they might have
died
– Evidence for improvement in survival with treatment is
modest NNT=20
• Bill-Axelson, et al NEJM 2005
– May be leading to lead-time bias
– No high quality RCT has shown a survival benefit
Critical appraisal of screening tests
• Does it do more harm than good?
• Specific ?s to ask:
– Is there an RCT that early diagnosis leads to improved
survival and/or QOL?
– Are the early diagnosed patients willing partners in
the treatment?
– How do benefits/harms compare in
screened/unscreened?
– Do the frequency and severity of the target disorder
warrant the degree of effort and expenditure?
Number of Diagnoses of All Prostate Cancers (Panel A) and Number of Prostate-Cancer Deaths
(Panel B)
•What might explain a negative result in this randomized study of screening?
50% of the control arm underwent screening
Cumulative Risk of Death from Prostate Cancer
Median F/U= 9 years
Never
seen a
curve like
this
Schroder F et al. N Engl J Med 2009;10.1056/NEJMoa0810084
Take homes for screening
• Does it do more harm than good?
– Personal matter
• Specific ?s to ask:
– Is there an RCT that early diagnosis leads to improved survival and/or QOL?
• Yes improved DSS in ERSPC; NNT=48 ; No improved DSS in PLCO
• F/U short
– Are the early diagnosed patients willing partners in the treatment?
• Yes
– How do benefits/harms compare in screened/unscreened?
• Unscreened do not have up-front and persistent harms of screening/treatment liked
screened do
• Screened have a marginal reduced risk of death in ERSPC
• ? effect on QOL r/e development of symptomatic metastases
– Do the frequency and severity of the target disorder warrant the degree of
effort and expenditure?
• Very personal decision
• Presently, we do not have a screening test for aggressive prostate cancers
Diagnosis
Prostate
gland
Rectum
Definitions
Grade = How well differentiated a tumor is
How closely tumor histologically resembles non-tumor/ normal
cells of that organ
Low-grade = Close resemblance
High- grade = Little resemblance
Gleason grading prostate cancer
Assign a number to the
primary/ predominant
pattern.
Assign a 2nd number to
the secondary pattern.
The sum of the numbers is
the Gleason grade/score.
Donald G. Gleason
(VAMC) 1977
Gleason grading of prostate cancer
Higher grade,
worse prognosis
grade 7 (3+4)
grade 10 (5+5)
Donald G. Gleason
(VAMC) 1977
Grade (= how closely prostate cancer cells resemble normal
prostate glands microscopically)
Pattern 3
Gleason grade 3+3=6
Pattern 4
Pattern 5
Gleason grade 4+4=8 Gleason grade 5+5=10
True, et al PNAS 2006
Stage = Where the tumor is at time of
diagnosis
Localized = Tumor is confined to
the organ of origin
Regional spread = Tumor has
invaded adjacent organs
Metastatic = Discontiguous
spread of tumor to other tissues
T.N.M
Incidental (TUR/PSA)
T1A, T1B, T1C
Localized
T2A, T2B , T2C
Locally-advanced
T3A, T3B , T3C
and T4
Metastatic
N(0) vs N(+)
M(0) vs M(+)
Take home points
• All men have prostate cancer
• The histology (grade) of a prostate cancer is a
basis for selecting the type of treatment
• Molecular determinants of grade are specific
biomarkers and targets for therapy
Prostate cancer treatment
Treatment for localized prostate
cancer
– Institutional bias determines which modality is
given
– Radical prostatectomy
– External beam radiation
– Equal cure rates for early disease
• No randomized, head-head data comparing these
approaches
– Brachytherapy
• Most well-studied in low risk tumors
– Androgen-deprivation therapy
• Patients who are not candidates for surgery or radiation
– Observation
• Patients with very limited life expectancy due to comorbid conditions
• Patients with very favorable-appearing tumors
Treatment Outcomes in Prostate
Cancer
• Overall survival (OS)
• Relapse-free survival (RFS)
– PSA blood test is used to monitor relapse
– No elevation in PSA or overt disease
recurrence
Radical prostatectomy
• Involves removal of the prostate, adjacent
seminal vesicles, and regional lymph nodes
• Can be performed as an open procedure or
laparoscopically +/- robotic assistance
– No head to data comparing the approaches
• Allows for determination of the pathological
extent of disease
– Prognostic
– May be therapeutic
• Lymph node removal
Radical Prostatectomy Side Effects
• Incontinence
• Impotence
– Common post-op but improves with time
• Contrasts with XRT which is less frequent
immediately post-treatment but increases with time
– More common in older patients and those with
erectile dysfunction pre-op
External Beam Radiation
• Patients are divided into risk groups based
upon historical outcomes with XRT
Low risk
Int risk
High risk
clinical stage
PSA
Gleason
score
T1c-T2a
T2b
>T3
<10
10-20
>20
6
7
8-10
-- D’Amico (1998) JAMA 280:969
External Beam Radiation
• Low risk patients
– XRT alone
• Intermediate risk patients
– Neoadjuvant Hormonal Therapy->XRT +
Concomitant Hormonal therapy
• LHRH-agonist + an anti-androgen
• High risk patients
– Neoadjuvant Hormonal Therapy-> XRT +
Concomitant Hormonal Therapy->Adjuvant for a
total of 3 years
• LHRH-agonist + an anti-androgen
• Bolla, et al ASCO 2007
External Beam Radiation Side Effects
• Acute
– Irritative symptoms (rectum and bladder)
• during treatment and afterwards
• Chronic
– Impotence
• Lower frequency post-treatment than surgery but increases
over time
• More responsive to PDE inhibitors than post-surgical
impotence
– Irritative symptoms (rectum and bladder)
– Risk of secondary malignancies
Brachytherapy (radioactive
seed implantation)
• Reserved for patients with Gleason scores <7
with clinical stage < T2b (tumors on only 1
side of the prostate) and PSA <10
• Follow-up data less mature
• Side effects
– Acute
– Irritative symptoms (urinary)
– Urinary retention
– Chronic
–
–
–
–
Impotence
Irritative symptoms (rectal and urinary)
Fistulas
Bleeding
Prognostic pathologic parameters
(classic)
Prognosis = Likelihood of the disease
recurring after x years
• Serum [PSA]
• Stage
• Grade
Kattan nomograms
• Useful tool to examine outcome for similar
patients to one’s own using wither preoperative or post-operative data
• Developed from a retrospective database
that was externally validated
• Kattan
Multivariable Analysis of the Risk of Biochemical Recurrence
N=151
Covariate
Odds ratio
95% CI*
P value
Preoperative PSA
1.00
0.91 – 1.09
0.99
Postoperative Gleason score
3.77
1.87 – 7.62
0.0002
Extra capsular penetration
4.92
1.31 – 18.52
0.02
Lymph node involvement
7.26
0.92 – 57.59
0.06
Seminal vesicle involvement
13.41
1.76 – 101.84
0.01
Surgical margin involvement
7.73
1.90 – 31.46
0.004
CDKN2A methylation
0.43
0.10 – 1.90
0.27
GSTP1 methylation
0.30
0.07 – 1.24
0.10
ASC methylation
2.08
0.57 – 7.60
0.27
CDH13 methylation
5.51
1.34 – 22.67
0.02
RUNX3 methylation
0.60
0.16 – 2.28
0.45
MGMT methylation
0.33
0.07 – 1.63
0.17
* Preoperative PSA and postoperative Gleason score were treated as continuous variables
#CI: Confidence interval
Alumkal, et al 2008
Disease States Model of Prostate Cancer
Metastatic
Hormone-naive
Localized
PSA Relapse
Hormone-naive
Metastatic
Castrate
Metastatic
Castrate
Docetaxel-resistant
PSA Relapse
Castrate
Death
Metastatic Disease
Epidural
space
Lung
Liver
Bone
Lymph
nodes
What is happening in the tumor in a
metastasis
• We do not fully know
• Clinical trials at OHSU
– Bone biopsy prior to starting therapy to examine tumors
with microarrays
– Stratify to specific treatment based upon genes
– Correlate with response/resistance to treatment
– Allow for better identification of genes responsible for
sensitivity/resistance to treatments
Treating metastases
• Goals are relief of symptoms and prolongation
of survival
– Pain-control is crucial
– Using most effective and least toxic treatments up-front
– Sequencing treatments
Alkaline phosphatase
Prostatic acid phosphatase
AR and Androgens in Prostate Cancer
Mutated AR
AR
AR
Testosterone(T)/
Dihydrotestosterone
(DHT)
Lower but not
absent T/DHT
ARE
Pre-castrate
PSA
ARE
PSA
Castrate-resistant (no longer
called “androgen independent”)
Hormonal therapy is our most effective
treatment
• LHRH-agonists
– Over stimulate hypothalamus -> decreased LHRH-> decreased LH-> decreased
testosterone
–
–
–
–
Initially, these treatments increase testosterone
80-90% PSA response rate
Most patients also have objective RRs
Median duration response 18-24 months
• Anti-androgens
– Compete with testosterone, DHT for binding to AR
– 30-40% PSA response rate
– Median duration response 6-12 months
– Anti-androgen withdrawal response
• 25% of men progressing on an anti-androgen will have a PSA response and
palliation of systems for 4-6 months when anti-androgen is D/C’d
• Felt to be due to AR mutations, which cause these drugs to act as agonists
• Ketoconazole
– Inhibits both gonadal and adrenal steroidogenesis
– 20% RR
– Median duration response 6-8 months
LHRH agonists,
DES
Orchiectomy
Targeting the Androgen Receptor (AR)
Protein
• AR is the engine of prostate cancer
– Activated by testosterone, the fuel of prostate cancer
– PSA is a gene which goes up when the engine is on
– ERG is a gene which can promote prostate cancer
development and invasion, which goes up when the
engine is on
• The wheels of prostate cancer
• Hormonal treatments inhibit prostate cancer mainly
by reducing levels of testosterone (fuel)
• Prostate cancer cells can eventually grow despite low
levels of testosterone (fuel)
• We then try to dilute out the remaining fuel with
“water,” drugs called anti-androgens
Hormonal Treatments
Death of some cancer cells
X
“Water down” the gas further
Growth and spread
despite low levels of
testosterone (fuel)
Chemotherapy
Supportive Care
• Bone health
– Adequate calcium and Vit D to prevent osteoporosis
from hormonal treatments
– Bisphosphonates
• Inhibit osteoclast function
• When given to men who have castrate-resistant metastatic
cancers, this helps prevent fractures
• Pain control
– XRT
– Analgesics
Is AR still a target when hormonal
therapy fails: “androgen
independence” versus “castration
resistance”?
Nature Medicine 2004
Cancer Research 2007
New therapies targeting AR after
castration resistance appear active
• MDV3100
Tran, et al Science 2009
• Abiraterone acetate
– Reduces adrenal steroidogenesis
Looking beyond hormonal therapy
to target AR and prostate cancer:
our approach
Diet, sulforaphane, and prostate
cancer
• There is strong epidemiological evidence for an inverse risk of prostate
cancer development and high intake of cruciferous vegetables, namely
broccoli
• Cohen, et al 2000, Kolonel, et al 2000, Giovannucci, et al 2003
• Nonetheless, many people do not consume these foods frequently
• Sulforaphane
– Broccoli constituent
– Prevents/delays tumor formation in murine models of colon cancer, other
tumors
– Fahey, et al 1997, Chung, et al 2000, Shen, et al 2007
– Causes cancer cell death or tumor regression in vitro and in prostate cancer
xenografts
– Mechanisms?
• Induction of Phase 2 detoxification enzymes, apoptosis, cell cycle arrest
•
Zhang 2004
• Histone deacetylase inhibition
•
Myzak, et al 2004
SIGNALING
HATs
HDACs
AC
N-
Histone proteins
Chromatin remodeling
K
-C
Non-histone proteins (HSP90, Tubulin)
Stability (AR, Her2Neu, Bcr-Abl, etc)
Gene expression
slide courtesy of David Qian
Centrality of AR in prostate cancer
• Expressed in nearly all human prostate cancers
• Key target for prevention and therapy
– Finasteride, LHRH-agonists, anti-androgens, lyase inhibitors, etc
• Resistance to these therapies is common
– AR mutations
– Intratumoral androgens persist despite effective serum castration (Mostaghel,
et al 2007)
– Depletion of AR protein is a way to overcome these modes of resistance
• Certain pharmacological HDAC inhibitors lower AR protein levels through HDAC6
inhibition and loss of HSP90 function
•
Bali, et al 2005, Scroggins, et al 2007
• Hypothesis
– We hypothesized that sulforaphane treatment would lead to hyperacetylation
of HSP90 and that this would destabilize AR protein and attenuate AR
signaling.
• i.e. We hypothesized we could take out the engine block!
Gibbs, et al PNAS in revision
Taking out the whole engine block
(and the wheels) rather than just the
fuel
Gibbs, et al PNAS in revision
Gibbs, et al PNAS in revision
Sulforaphane
Acetyl
AR
Active HSP90
Decreased de-acetylation
of HSP90 and alpha-tubulin
Inactive or reduced
X levels of HDAC6
Hyperacetylated, inactive HSP90
HDAC6
X
HDAC6
Alpha-tubulin
Inactive or reduced
levels of HDAC6
X
X
AR
X
X
HDAC6
Protein instability and
proteasomal degradation of
AR and HDAC6
Hyperacetylated
alpha-tubulin- ? role
AR
ERG and other AR target genes
ERG and other AR target genes
Gibbs, et al PNAS in revision
What we know/don’t know
• ERG over-expression leads to PIN precursor lesions in
transgenic mice and cellular invasiveness
• 35% of human PIN lesions express ERG
• Most prostate cancers express ERG
• Diets high in broccoli are associated with a reduced risk
of prostate cancer
– Sulforaphane, in broccoli, shuts down AR and ERG (and other AR
target genes like PSA) expression
• Will this prevent prostate cancer precursor lesions through this
mechanism?
• Will this lower PSA levels and have anti-cancer properties in men with
recurrent prostate cancer?
To determine whether SFN supplementation in a murine PIN model of
prostate cancer leads to disruption of AR and ERG expression and
reduced incidence of PIN formation.
ERG
X?
Benign
SFN
PIN (Prostate cancer
precursor)
Klezovitch PNAS 2008
Current Directions with Sulforaphane
• Further explore the effect of sulforaphane on
prostate cancer cells
• Feeding ERG transgenic mice sulforaphane to
see if we can prevent prostate cancer
• Clinical trial with sulforaphane in men
whose cancers recur despite aggressive
treatments like surgery or radiation
Specific gene regulation requires the assembly and coordinate action of
demethylases with distinct substrate specificities
Non-castrate:
ON
PSA
AR
JHDM2A
LSD1
JMJD2C
Other
chromatin
modification
factors??
Castrate State:
REDUCED (NOT
OFF)
PSA
AR
LSD1
JMJD2C
Metzger, et al Nature 2005
Yamane, et al Cell 2006
Wissman, et al Nature Cell Bio 2007
Other
chromatin
modification
factors??
LSD1
• LSD1 (Lysine specific demethylase
1)
Turns off genes
– A monoamine oxidase
– Silences genes with HDACs, which are
commonly up-regulated in prostate
cancer
• Shi, et al 2004
– Found to complex with AR protein and
turn on AR target genes
• Metzger, et al 2005
• Yamane, et al 2006
– Higher LSD1 levels or low levels of the
histone mark it removes are associated
with prostate cancer recurrence
• Kahl, et al 2006
• Seligson, et al 2006
– Inhibition or knock-down of LSD1 leads
to reduced cell growth
Turns on genes
• Which LSD1 gene targets mediate this??
Wysocka, et al 2005
Treatment with a LSD1 small molecule
inhibitor reduces PSA
1c Treatment Reduces PSA
8.00
7.00
EXPRESSION
6.00
5.00
4.00
3.00
2.00
ChIP PCR of PSA gene
1.00
0.00
Mock in Presence of
Testosterone
1c in Presence of
Testosterone
Mock in Absence of
Testosterone
SAMPLE
QRTPCR of PSA gene
1c in Absence of
Testosterone
Check human prostate cancer samples
to determine genes whose
expression is directly/inversely correlated
with LSD1 by expression arrays
Vehicle
siNTC
LSD1 inhibitor
siLSD1
Expression arrays after siLSD1 and
pharmacological inhibitor treatment
in vitro
-293 common genes increase
-51 common genes decrease
Check LSD1 ChIP-Chip datasets
for genes with LSD1 enrichment
Putative direct, functional LSD1 targets
-Assess LSD1 occupancy, control of expression
-Assess gene role in transformation
Modified from
Yu, et al 2007
Summary
• Prostate cancer is common, detectable, sometimes
lethal
• Targeting AR may prevent cancer
– Diet?
• Screening can ID cancers
– Need better methods to screen for aggressive cancers
• Variety of treatment options for localized disease
– Path features and molecular basis for these features may
aid in prognostication
• AR is a key target for treatment in all phases of the
disease (even after castration resistance)
• Translational, molecular studies hold promise for
improving patient outcomes
Acknowledgements
• Alumkal lab
– Angela Gibbs
– Jacob Schwartzman
– Dylan Zodrow
– Lina Gao, PhD
– Looking for another good
post-doc!
• Fred Hutchinson
– Larry True
• Johns Hopkins
– James Herman
– Robert Casero
• Wayne State
– Pat Wooster