Transcript The tumor microenvironment: problems and opportunities for

The tumor microenvironment:
problems and opportunities
for therapy
Nic Denko PhD MD
Radiobiology 2013
The tumor microenvironment
• Unique architectural, physiologic and cellular
environment
• Poor perfusion leads to decreased oxygen
(hypoxia), decreased nutrients
(hypoglycemia), and increased waste products
(acidosis
• All these stresses have compensatory adaptive
cellular responses
Oxygen is a dose modifying factor
OER can be up to 3
Tannock and Hill BSO 1998
Adaptive Biologic Responses
• Hypoxia: HIF-1 (HIF1a and HIF2a), UPR,
SREBP-1, ATF-3, NF-KB
• Hypoglycemia: HIF-1, Mondo, UPR
• Acidosis: Sp1 (renal tubule cells), mRNA
stability
• Increased IFP: ???
HIF-dependent Gene Induction
Hypoxia
PI3K/PTEN/akt
?
Prolyl hydroxylase
?
HIFb
constitutive
Ubi
Elongins
VHL
Other
Transactivation
P564-OH
P402-OH
Hif1a
Inducible
targets?
Proteasome
HRE
VHL connects hypoxic gene induction to
human tumor formation
• VHL is a classic “two hit” tumor suppressor
• Loss of VHL leads to constitutive HIF-1
activity
• Model tumors suggest that this regulation of
HIF is a major activity for tumor suppression
VHL-resistant HIF is tumorigenic in Renal
Cell Cancers
Kaelin
CC 2002
Unfolded proteins generate
a complex, three prong response
Kaufman JCB 2012
Disulfide bond formation requires
molecular oxygen
Feldman and Koong Mol Can Res 2005
Protein Glycosylation requires glucose
How to overcome hypoxia?
• More oxygen delivery
– RBC Mass (transfusion, Epo)
– Inhaled oxygen (100% F1 02)
– Vasorelaxants (hydralazine)
• Oxygen mimetics (Misonitozole, etanidozole,
nimorazole)
• Hypoxic cytotoxins (MMC, TPZ, AQ4N, Pr104)
• Less oxygen utilization ?
Misonidozole
sensitizes
hypoxic cells
to XRT
Miso sensitizes model tumors to
single dose XRT treatment
1000 mg/kg
Miso pre XRT
Development of oxygen mimetics
Nimorazole shown to be beneficial in patients with HNC treated with XRT
Hypoxic Cytotoxins
Tirapazamine
Drug is only
Toxic in
hypoxia
TPZ + XRT in vivo
TPZ has
Low activity
as a single agent
Oxygen tension is a function of
Supply and demand
Supply
Demand
Tumor
Circulation
Systemic
Circulation
Tumor
Vasculature
Can we modify hypoxia
from the demand side?
Hours post DCA
0h
2h
4h
6h
24h
RKO RKOShHIF
Change in
luciferase activity
(photons/s)
d
RKO
RKOshHIF
6.E+07
4.E+07
2.E+07
0.E+00
-10
0
10
20
Time (hr)
30
Increased
oxygen consumption
Causes
Increased hypoxia
post DCA
Metabolic (PDHK) inhibitors
can enhance TPZ activity in vivo
DCA has
to be given
before TPZ
Can we decrease oxygen consumption
and decrease hypoxia?
• Use drugs that decrease mitochondrial
function and reduce overall tumor oxygen
consumption
• Measure changes in oxygenation
• Measure radiosensitization
Oxylite A549 tumor MTF response
49
IV high 7a
44
IV 3.5b
39
IV 4.5
mmHg
34
IV 3.5g
29
IV 3.5i
24
IV 3.5j
19
14
9
4
-1
-10
15
40
65
90
time (drug injected at t=0)
115
140
Tumor Microenvironment
• No microenvironment modifying agents have
yet been successful in improving XRT
(nimorazole in Europe).
• HIF1 may be a marginal target, XBP1 may have
some efficacy, Hgb increases always make the
patient feel better.
Which of the following agents has NOT been
found to be useful for measuring human tumor
hypoxia?
A. [18F]- 2-fluoro-2-deoxy-D-glucose (FDG),
B. pimonidazole
C. [18F]Azomycin Arabinoside (FAZA)
D. [64Cu]- Copper dithiosemicarbazone (ATSM)
E. [18F]Fluoromisonidazole (FMISO)
Pre-treatment correction of anemia with either blood
transfusion or epo may be considered in cancer patients. This
is based, in part, on which one of the following observations?
A. In a German/Swiss, multicenter, randomized, clinical trial,
advanced head and neck cancer patients receiving epoetin
alfa achieved higher hemoglobin concentrations and longer
progression-free survival than placebo.
B. Anemia correction has been shown to improve quality of
life by reducing fatigue.
C. In the Breast Cancer Erythropoietin Survival Trial (BEST),
patients with metastatic breast cancer demonstrated
improved overall survival when treated with epoetin alpha
compared to placebo.
D. The activation of hypoxic signaling pathways, including
HIF-1α, is associated with resistance to therapy and depends
critically on hemoglobin levels
Which statement describing tumor vasculature is correct?
A. Tumor blood vessels are hyper-permeable, tortuous, and feature
haphazard patterns of interconnection, resulting in spatial and
temporal heterogeneity of tumor blood flow.
B. Tumor blood vessels are hypopermeable, irregular, and densely
invested with pericytes resulting in poor diffusion of
chemotherapeutics into tumor parenchyma.
C. Tumor blood vessels are indistinguishable from normal blood vessels
ultrastructurally, however compression caused by proliferating tumor
cells leads to vessel collapse and compromised blood flow.
D. Tumor blood vessels are dilated, tortuous and have uniformly thick
basement membranes, resulting in limited accessibility of
chemotherapy agents.
E. Tumor blood vessel organization resembles that of normal vessels,
however tumor vessels differ ultrastructurally, resulting in poor
function and heterogeneous blood flow.
The regulation of hypoxia-inducible factor-1α (HIF-1α) by oxygen
concentration is best described by which of the following statements?
A. Under hypoxic conditions, HIF-1α transcription and translation are
upregulated, causing the protein to translocate from the cytosol to the
nucleus.
B. Under aerobic conditions, the HIF-1α heme moiety becomes
oxygenated. This drives a conformational change in the protein
limiting DNA binding preventing up-regulation of target genes.
C. Under hypoxic conditions, HIF-1α is activated by bioreduction,
thereby promoting the up-regulation of target genes.
D. Under hypoxic conditions, the HIF-1α heme moiety becomes
deoxygenated. This causes a conformational change in the protein,
enhancing DNA binding promoting up-regulation of target genes.
E. Under aerobic conditions, HIF-1α is hydroxylated by HIF prolyl
hydroxylases. This targets the protein for ubiquitination and
subsequent proteosomal degradation, thereby preventing the upregulation of target genes.
Methods currently under investigation to
monitor the effectiveness of antiangiogenic
therapy include all of the following, EXCEPT:
A. dynamic MRI/CT and PET imaging
B. serial tumor biopsies
C. plasma levels of bevacizumab
D. VEGF concentration in the urine
E. presence of vascular endothelial cells in
the peripheral blood