Annual Meeting Proceedings Part 1 - American Society of Clinical ...

686s Tumor Biology
10622 General Poster Session (Board #52G), Mon, 1:15 PM-5:15 PM
Diurnal proteomics and biomarker discovery in indolent versus aggressive
chronic lymphocytic leukemia patients. Presenting Author: Georg A.
Bjarnason, Sunnybrook Odette Cancer Centre, University of Toronto,
Toronto, ON, Canada
Background: In rodents, 10-20% of the genome has a 24-hour (h) rhythm in
RNA expression. A molecular clock consisting of transcription / translation
feedback loops of clock-genes controls this rhythmicity. In a microarray
study (Affymetrix HG_U133_Plus2 chip) on RNA extracted from CLL cells
sampled every 4 hours over 24 hours (6 samples) from 3 male (M) and 6
female (F) patients (pts) with chronic lymphocytic leukemia (CLL) we found
15,094 and 13,415 rhythmic transcripts (Cosinor analysis) in M and F
respectively, only 6,629 of which were common to both M and F. We
hypothesized that these gender differences in rhythmic RNA expression
might have clinical implication for biomarker discovery with some important
biomarkers only found at a certain times of day and with gender
differences. Methods: Sampling was performed again at 6 time points in M
and F CLL patients with indolent CLL (10pts, 5 M, 5F) and aggressive CLL
(10 pts, 5M, 5F). An 8-plex iTRAQ kit was employed for mass spectrometry
(MS) based relative quantification. Each iTRAQ block comprised all
time-points for a single patient including a universal control. Results: At
least 300 proteins were identified at a 95% confidence level in each iTRAQ
experiment. Of these, 74 proteins displayed significant change between
aggressive and indolent pts in 24-hour average or single time point
normalized expression based on a non-parametric U-test (p�0.05). The
JTK_CYCLE algorithm was used to detect 24-hour rhythmic patterns in the
proteomic datasets. Significant rhythmic expression was found for 44
proteins (p�0.10) identified by iTRAQ. Data for each time point were
independently analyzed using an in-house Butterfly clustering algorithm
based on discrete dynamical systems. The 4 PM time point was found to be
optimal for stratifying aggressive and indolent disease. Cellular pathways
with significant association to differentially expressed proteins included
PPAR signaling, fatty acid metabolism, and granzyme-A signaling. Confirmation
by selected reaction monitoring (SRM) MS is ongoing. Conclusions:
Rhythmic protein expression may have clinical implications for biomarker
discovery.
10624 General Poster Session (Board #53A), Mon, 1:15 PM-5:15 PM
Synthetic lethality of EGFR blockade in the context of tumor hypoxia.
Presenting Author: Haruhiko Makino, University of Texas SouthWestern
Medical Center Department of Radiation Oncology, Dallas, TX
Background: Hypoxia induces a wide spectrum of biological responses in
tumors that alter tumor radio-sensitivity. In several tumors, including
non-small cell lung carcinoma (NSCLC), the epidermal growth factor
receptor (EGFR) is frequently over-expressed and activated in response to
hypoxia, although the precise role of EGFR in hypoxia-associated radioresitance
is unclear. Activating mutations in EGFR have been clinically linked
to dramatic responses to EGFR tyrosine kinase inhibitors. We previously
demonstrated that NSCLCs harboring activating EGFR mutations are
radiosensitive with severe deficits in the non homologous end-joining
(NHEJ) repair of DNA damage. Methods: We investigated hypoxia associated
radiation responses in a panel of NSCLC cell lines and immortalized
human bronchial epithelial cells expressing wild type EGFR (WT) or
expressed EGFR forms with somatic activating L858R or DE746-E750
mutations (MT). Results: (1) Relative to WT EGFR, MT EGFR expression is
associated with significantly higher radiosensitivity under chronic hypoxia
(2) Under hypoxic conditions, MT EGFR expression is associated with a
unique spectrum of DNA damage responses (DDR) that significantly
deviated from canonical response of WT EGFR expressing NSCLCs (3)
Genome wide gene expression analysis identified a dramatic hypoxiaassociated
DDR shift to selective down-regulation of homologous recombination
(HR). Moreover, MT EGFR deficits in NHEJ caused a synthetic
lethality effect in the context of hypoxia through a simultaneous blockade
of HR and NHEJ. (4) Blockade of WT EGFR by the anti-EGFR monoclonal
antibody, cetuximab perfectly recapitulated the contextual synthetic lethality
of MT EGFR expression. (5) Cetuximab had a dramatic synergistic effect
on survival of rat lung orthotopic tumors where hypo-fractionated radiotherapy
or cetuximab alone had marginally controlled tumors. Conclusions:
The data support a critical role for EGFR-mediated DNA repair in hypoxia
associated tumor radio-resistance. Furthermore, this role could be a target
for refractory hypoxic EGFR-WT tumor especially in the context of hypofractionated
radiotherapy which, in its current form, is potentially counterproductive
for hypoxic tumors.
10623 General Poster Session (Board #52H), Mon, 1:15 PM-5:15 PM
New mechanistic insights into possible radiobiologic and pathophysiologic
explanations for unexpectedly impressive outcomes data observed for
hormone-refractary metastatic prostate cancer patients treated with radium
223. Presenting Author: Roger M. Macklis, Cleveland Clinic Foundation
and Taussig Cancer Center, Cleveland, OH
Background: The ALSYMPCA Trial of 223Ra (“Alpharadin”) for men with
metastatic castrate-resistant prostate cancer was a Phase III randomized
trial comparing 223Ra plus SOC vs best SOC. This trial was stopped early
after 922 patients enrolled at over 100 centers achieved primary (overall
survival) and all secondary endpoints including median survived (14 vs
11.2 m) time to first SRE (13.6 m vs 8.4 m) and time to PSA
progression.These unexpectedly positive results prompted us to review
some of the unique aspects of alpha-particle radiobiology and ultra-short
range molecular targeting capabilities. Methods: Literature analysis. Results:
The highly energetic alpha particles such as those released during decay of
223Ra (T1/2 � 11.4 mins) display unique radiobiologic and dosimetric
aspects. The nuclear dose required in vitro for approximately 90% target
cell kill is less than 1 Gy and electron micrographs shortly after exposure
confirm bizarre blebbing and condensation of chromosomal material
characteristic of apoptosis. Bovine aortic endothelial cells exposed to alpha
particle radiation indicate that the radiobiologic effects depend heavily on
cell culture condition with nonuniform DNA strand break damage observed
in isolated detached cells. The subcellular alpha particle path length
appears to allow specific target cell populations to be killed within bony
stroma without excessive damage to nearby sensitive hematopoietic cells.
223Ra treatment in rodent models showed that this family of Ca �� analogs
delivers extremely high doses to stromal elements such as bone-resorbing
osteoclasts and this selectivity may aid in decreasing SREs. Conclusions:
We highlight the fact that some basic radiobiologic and cell compartmentspecific
stromal localization principles known to be effective in alpha
particle radiopharmaceutical therapy may contribute to the very positive
clinical outcomes observed while allowing subcellular damage accumulation
to target cell groups.
10625 General Poster Session (Board #53B), Mon, 1:15 PM-5:15 PM
Using CHFR expression to predict response and survival after first line
treatment with carboplatin-paclitaxel in NSCLC. Presenting Author: Rathi
Narayana Pillai, Winship Cancer Institute, Emory University, Atlanta, GA
Background: The identification of resistance mechanisms for conventional
chemotherapy in lung cancer is of fundamental importance not only for
personalization of chemotherapy but also for the subsequent development
of novel targeted approaches to overcome this resistance. Currently, there
is no clinically validated test for the prediction of response to tubulintargeted
agents in NSCLC. Our previous preclinical work identified Checkpoint
with Forkhead and Ringfinger domain” (CHFR) as a predictor of
taxane cytotoxicity in in vitro models. The current work assessed the
translational significance of this finding in a cohort of US veterans treated
at a single-institution. Methods: We studied a cohort of patients with
advanced NSCLC treated with taxane-containing frontline regimens at the
Atlanta VA Medical Center between 2000 and 2009. Archived paraffinembedded
tissue was retrieved and stained for CHFR expression using
standard immunohistochemical techniques. Level of protein expression
was assessed by light microscopy and scored for intensity of CHFR staining.
Intensity of staining was correlated with clinical outcome including
objective response and median overall survival using Chi-Square test and
Cox proportional models. Results: We analyzed tumor samples from 45
eligible patients with median age 62.6 years, M/F (44/1). In this cohort,
high expression of CHFR is strongly associated with adverse outcomes: the
risk for progressive disease (PD) after first-line chemotherapy with carboplatin-paclitaxel
was 54% in patients with CHFR-high vs. only 18% in those
with CHFR-low tumors (HR 3.1; 95% CI 1.09-9.04; p�0.02). Median
overall survival was strongly correlated with response to first-line therapy
(clinical benefit: 9.24 months; PD: 4.7 months; p�0.001) and with CHFR
expression status (CHFR low: 10 months; CHFR high: 5.6 months; p
�0.01). Conclusions: CHFR expression is a novel predictive marker of
response and overall survival in NSCLC patients treated with taxanecontaining
chemotherapy.
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