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radiotherapy. Patients with relapsed or refractory neuroblastoma who received 131I-mIBG at UCSF were
used to correlate internal ionizing radiation (IR) dose with selected gene expression. 41 patients, median
age 9 years, had blood drawn at baseline, 72, 96, and 120 hours after 131I-mIBG infusion. A total of 14
patients received mIBG treatment only, while 19 patients received Irinotecan and 7 received Vorinostat
in combination with mIBG. Whole body absorbed dose was calculated for each patient based on the mIBG
treatment doses using MIRD internal dosimetry models. We then assessed transcripts using RT-PCR that
were the most significant for describing the mixed therapeutic treatments over time. Modulation was
evaluated statistically using multiple regression analysis for data at hours 0, 72, 96. A total of 6 genes were
analyzed across 41 patients: CDKN1A, FDXR, GADD45A, BCLXL, STAT5B, and BAX. Four genes were
significantly modulated upon exposure to 131I-mIBG at 72 hours, as well as at 96 hours, when controlling
for dose and chemotherapy. Four genes varied significantly with absorbed dose when controlling for time
and chemotherapy. Five genes showed significant responses to Irinotecan combined with mIBG and 2 had
significant responses to Vorinostat combined with mIBG, all when controlling for time and dose. Pearson’s
product-moment correlation test showed significant relationships between the collective transcript
responses to IR dose, time, and chemotherapy. This represents a unique study using radiotherapy patients
to characterize biomarkers that may be useful for biodosimetry and treatment. Our data indicate that
transcripts, which have been previously identified as biomarkers of external exposures in ex vivo whole
blood and in vivo radiotherapy patients, are also good indicators of internal exposure over time. The
characterization of internal irradiation-responsive genes will provide valuable understanding of the
genetic mechanisms related to internal exposures.
(PS6-23) A retrospective comparison of chromosome damage measured by three-color painting and
mFISH. Michael Cornforth and Bradford Loucas, University of Texas Medical Branch, Galveston, TX
Whole chromosome painting (WCP) involves the labeling of a few select chromosomes of the
genome, thereby producing discrete changes in fluorescent color patterns that accompany the junctions
of exchange breakpoints. These include junctions between the painted and unpainted chromosomes, and
between the painted chromosomes themselves. WCP data can be mathematically rendered in order to
approximate the total number of exchanges that would have been detected if all the chromosomes would
have been painted a unique color. Converting WCP data to “whole genome equivalents” makes use of
relationships similar to that of Lucas and colleagues (Lucas, Tenjin et al. 1989). In theory, this approach
addresses the problem of unseen exchanges between unpainted chromosomes. Yet WCP has also
demonstrated that a significant fraction of radiation-induced interchanges are complex, involving the
three (or more) chromosomes. Many complex exchanges go undetected by WCP, and many others are
incorrectly scored as simple exchanges (pseudo-simple exchanges). The presence of complex exchanges
violates the assumption common to such methods of approximation that all interchanges are simple
reciprocal rejoinings between just two chromosomes. We reasoned that violating this core assumption
would lead to errors when applying whole genome corrections to WCP data, and set out to examine the
extent of these putative errors. To do this, we conducted a retrospective examination of our 24-color
(whole genome) mFISH data base for aberrations produced in human cellsby a range of different radiation
types. On a cell-by-cell basis, we stripped from the full 24-color mFISH profile all information concerning
exchanges except that pertaining to three-color WCP. From this information, we used the mathematical
correction suggested by Cucinotta and colleagues (George, Hada et al. 2009) to scale this WCP data back
336 | P a g e
used to correlate internal ionizing radiation (IR) dose with selected gene expression. 41 patients, median
age 9 years, had blood drawn at baseline, 72, 96, and 120 hours after 131I-mIBG infusion. A total of 14
patients received mIBG treatment only, while 19 patients received Irinotecan and 7 received Vorinostat
in combination with mIBG. Whole body absorbed dose was calculated for each patient based on the mIBG
treatment doses using MIRD internal dosimetry models. We then assessed transcripts using RT-PCR that
were the most significant for describing the mixed therapeutic treatments over time. Modulation was
evaluated statistically using multiple regression analysis for data at hours 0, 72, 96. A total of 6 genes were
analyzed across 41 patients: CDKN1A, FDXR, GADD45A, BCLXL, STAT5B, and BAX. Four genes were
significantly modulated upon exposure to 131I-mIBG at 72 hours, as well as at 96 hours, when controlling
for dose and chemotherapy. Four genes varied significantly with absorbed dose when controlling for time
and chemotherapy. Five genes showed significant responses to Irinotecan combined with mIBG and 2 had
significant responses to Vorinostat combined with mIBG, all when controlling for time and dose. Pearson’s
product-moment correlation test showed significant relationships between the collective transcript
responses to IR dose, time, and chemotherapy. This represents a unique study using radiotherapy patients
to characterize biomarkers that may be useful for biodosimetry and treatment. Our data indicate that
transcripts, which have been previously identified as biomarkers of external exposures in ex vivo whole
blood and in vivo radiotherapy patients, are also good indicators of internal exposure over time. The
characterization of internal irradiation-responsive genes will provide valuable understanding of the
genetic mechanisms related to internal exposures.
(PS6-23) A retrospective comparison of chromosome damage measured by three-color painting and
mFISH. Michael Cornforth and Bradford Loucas, University of Texas Medical Branch, Galveston, TX
Whole chromosome painting (WCP) involves the labeling of a few select chromosomes of the
genome, thereby producing discrete changes in fluorescent color patterns that accompany the junctions
of exchange breakpoints. These include junctions between the painted and unpainted chromosomes, and
between the painted chromosomes themselves. WCP data can be mathematically rendered in order to
approximate the total number of exchanges that would have been detected if all the chromosomes would
have been painted a unique color. Converting WCP data to “whole genome equivalents” makes use of
relationships similar to that of Lucas and colleagues (Lucas, Tenjin et al. 1989). In theory, this approach
addresses the problem of unseen exchanges between unpainted chromosomes. Yet WCP has also
demonstrated that a significant fraction of radiation-induced interchanges are complex, involving the
three (or more) chromosomes. Many complex exchanges go undetected by WCP, and many others are
incorrectly scored as simple exchanges (pseudo-simple exchanges). The presence of complex exchanges
violates the assumption common to such methods of approximation that all interchanges are simple
reciprocal rejoinings between just two chromosomes. We reasoned that violating this core assumption
would lead to errors when applying whole genome corrections to WCP data, and set out to examine the
extent of these putative errors. To do this, we conducted a retrospective examination of our 24-color
(whole genome) mFISH data base for aberrations produced in human cellsby a range of different radiation
types. On a cell-by-cell basis, we stripped from the full 24-color mFISH profile all information concerning
exchanges except that pertaining to three-color WCP. From this information, we used the mathematical
correction suggested by Cucinotta and colleagues (George, Hada et al. 2009) to scale this WCP data back
336 | P a g e
