Understanding cellular responses modulated by low doses of...

Understanding cellular responsesmodulated by low doses of ionizing

radiation

Matthew Coleman Ph.D.Andrew Wyrobek Ph.D.

[email protected]

UCRL-JRNL-204884; Coleman, et. al., (October, 2005) Rad Res.

From the Washington Post

“The health risk posed by radiation from X-rays andother medical procedures is so small that it shouldnot deter people from seeking needed medicalcare….. there is no dose of radiation, howeverlow, that can be deemed completely safe”.

Bier Report from the National Research Council, Thursday, June 30, 2005

Cells respond to ionizing radiation by choosing torepair themselves or undergo programmed cell

deathIonizingradiation

Radiationdamage• DNA strand

breaks

• Oxidativedamage

Cellfunction/fate

Cell death

Cellularresponse• Gene expression

changes:

mRNA, protein

• Proteinmodification

seconds minutes hours years

Cancer

Birth defects

Gene pool

Acutesyndromes

Organ failure

weeks

GenomicInstability

1 day

Drivesmedicalconsequences

Cellularresponse

DOE Low-Dose Radiation ResearchProgram

• A ~10 year program

• Focused on biological mechanisms of low-dose (< 10 cGy) and low dose-rate (< 10 cGy / Yr) radiation

• International in scope, with multiple joint projects co-funded with NASA

• Goal: to develop radiation standards based on risk

• http://lowdose.tricity.wsu.edu/

Need for studies of low dose

- Standards have been set from high dose effects, but low dose effects havenot been measurable until recently.

- Radiation risks from low levels of radiation exposure cannot be predictedwith epidemiological studies alone.

- Understanding the role of these biological changes in cancer risk may ormay not impact radiation protection standards, but will help ensure that thestandards are both adequate and appropriate.

- Combining advances in technology with those in cell and molecular biologymake it possible to detect biological changes after low doses and varying dose-rates of radiation exposure.

•http://lowdose.tricity.wsu.edu/

• Units of absorbed dose– 1 cGy (0.01 Gy) = 1 rad ≈ 1 rem

• Toxicity– D10 usually ~400 cGy– D37 usually ~70 to 200 cGy– no detectable apoptosis or cytotoxicity at 10 cGy or less with conventional assays

• Radiation therapy– standard daily dose usually ~200 cGy– total dose usually ~5,000 cGy or more

• Occupational exposure limits– 5 cGy per year

• Background radiation levels– 0.37cGy per year (0.3 natural and 0.07 man-made)

Defining the Low Dose Range (<10cGy)


70 mrem/yrMedical procedures 53 mremsConsumer products 10 mremsOne coast to coast airplane flight 2 mremsWatching color TV 1 mremSleeping with another person 1 mremWeapons test fallout less that 1 mremNuclear industry less than 1 mrem

Normal annual exposure from man-made radiation

Normal annual exposure from natural radiation 300 mrem/year = 0.3 cGy = ~1 day in space

Radon gas 200 mrem Human body 40 mrem Rocks, soil 28 mrem Cosmic rays 27 mrem

1 % risk of developing cancer is associated with 10 CTscans or 1000 chest X-rays


Several cellular response phenomena have been attributed tolow-dose irradiation and what are the “conceptual” risks?

RIS

K

Radiation Dose

Low dose hypersensitivitycells show more sensitivity to low doses(effects as low as 1 uGy)

Adaptive Responselow dose (priming dose) inducesprotection from damage to subsequenthigher dose exposures (challenge dose)

Bystander Effectdamage to neighboring cells not directlyhit by radiation beam under low-doseand low-dose rate conditions

Genomic Instabilityelevated frequencies of cells withgenomic damage in subsequent cellgenerations

Low dose

High DoseSupportedby data

Gene-transcript expression microarray technology is anideal tool for inferring molecular processes fromgenomic responses.

Amundson, et al.,2001, 2002 and 2003 - human lymphocytesYin, et al., 2003 - mouse brainGoldberg et al., 2004 - human skin biopsiesMercier, et al., 2004 - YeastDing, et al., 2005 - human fibroblastColeman, et al., 2005 - human lymphoblastoid

All of these experiments point to the fact that low doses of IR elicit aunique response that is different when compared to high IR doses.

Experimental and

Model System s Estimates of numbers of radiation responsive gene s

Single dose exposure Genes on c h i p IR responsive

Low-dose

responsive

High-dose

responsiv e

Human in vitro (dose

response) ~22,000 4 2 0 8 0 2 1 0

Mouse in vivo (time

response) ~10,000 7 0 0 1 9 0 2 1 0

Mouse in vivo (dose

response) ~10,000 760 210 130

Split-dose exposures Genes on c h i p IR responsive 5 cGy effect

Radioadaptive

associat e d

Human in vitro (adaptive

response) e ~12,000 520 1 4 0 1 6 0

Published experimental data sets to understand low doses ofIR at LLNL

Coleman and Wyrobek. 2005 (In press)

Unique gene sets

Experimental and

Model System s Estimates of numbers of radiation responsive gene s

Single dose exposure Genes on c h i p IR responsive

Low-dose

responsive

High-dose

responsiv e

Human in vitro (dose

response) ~22,000 4 2 0 8 0 2 1 0

Mouse in vivo (time

response) ~10,000 7 0 0 1 9 0 2 1 0

Mouse in vivo (dose

response) ~10,000 760 210 130

Split-dose exposures Genes on c h i p IR responsive 5 cGy effect

Radioadaptive

associat e d

Human in vitro (adaptive

response) ~12,000 520 1 4 0 1 6 0

Experimental data sets to understand low doses of IR

Coleman and Wyrobek. 2005 (In press)

Adaptive Response

When large radiationexposure is preceded by a

small “tickle” dose, theeffect of the large dose is

sometimes diminished


History of the adaptive responseHistory of the adaptive response• Samson and Cairns (1977). E. coli pre-exposed to a sub-

lethal dose of alkylating agent increases the survival to asubsequent toxic dose of alkylating agents. (Adaptation)

• Olivieri et al (1984) A prior exposure to a low-dosefollowed by a subsequent high dose of irradiation canreduce chromosomal aberrations in lymphocytes.(Radioadaptation)

• The effect is an early response mechanism peaking 4-6hours post high dose irradiation.

• Cross adaptation has been observed between radiationand metals, chemicals and hyperthermia.

• May have applications in cancer biology.

Adaptive Response

0102030405060708090

0 0.5 150 0.5 + 150

ObservedExpected

Shadley and Wolff 1987

Abe

rrat

ions

Dose cGy•http://lowdose.tricity.wsu.edu/

Adaptive outcomes have beenassociated with multiple biological

outcomes

• Chromosome damage (Olivieri 1984)

• DNA damage (Le et al 1998)

• Mutation (Sanderson et al. 1986)

• Cell transformation (Redpath and Antoniono 1998)

• Cell killing (Ishi and Watanabe 1996)

• Gene Induction (Colemanet al. 2005)


Adaptive response has beendemonstrated on various levels

• Molecular• Cellular• Tissue• Whole animal• Human (cellular)


Adaptive response is specific

There seems to be a genetic basis for adaptive response, since it is

demonstrated only in specific celllines, tissues, animal lines and

individuals.


Radioadaptation has been associated withRadioadaptation has been associated withspecific protein responsesspecific protein responses

Protein References

PI3K [Sasaki, 2002]

PKC [Sasaki, 2002]

p38MAPK [Sasaki, 2002]

PLC [Sasaki, 2002]

HSPA4 [Kang, 2002]

PBP74 [Sadekova, 1997], [Carette, 2002]

- TP53 may play a pivotal role radioadaptation through cell cycle control, DNARepair, stress response and transcription/translational control. - Inhibiting DNA repair or protein synthesis will block radioadaptation

Cell signaling

Stress response

Cellular function

Our experimental approach to understanding themechanisms of radioadaptive response

- Measure cytogenetic adaptive response(chromosomal damage end point)

- Apply gene expression analysis

- Correlate gene expression to phenotype

- Form hypotheses for future testing

Are IR induced low dose genes/functions predictive for protection fromAre IR induced low dose genes/functions predictive for protection fromchromosomal damage from a subsequent high dose exposure?chromosomal damage from a subsequent high dose exposure?

Micronuclei analysis tomeasure chromosomaldamage.

Radioadaptive response onchromosome damage

Human lymphoblastoid model system

HLB cells:- Controllable experimental conditions.- Experiments can be repeated using same line.- Cell cycle can be synchronized.- Allows both genetic and physiological comparisons.

Human Genetic Cell Repository, is a resource of cell lines and DNA samples that can be

used to discover DNA sequence polymorphisms. This resource is comprised of cell lines

from 450 unrelated individuals, male and female designed to reflect the diversity in the

human and facilitates finding genetic variants in the entire human population from a

random sample of residents of the United States.

Population Group Full Set Subset of 24

European American 120 6

African American 120 6

Mexican American 60 3

Native American 30 3

Asian American 120 6

Total Individuals 450 24

Mature RedBlood CorpusclesLiver CellsNeural CellsPituitary CellsThyroid CellsMuscle CellsBone andCartilage CellsSkin EpitheliumCorneaSquamousMucousEpitheliumRenal TubulesLung-Tissue CellsLensGonadal GermCellsSmall intestineepithelium Bone-Marrow CellsLymphocytes

Time (hrs.)

Adapting Dose:5 cGy

Challenge Dose: 200 cGy

HarvestCells for MN analyses

0 6 28

Add CytoB

22

RNA and protein sampling windows

Experimental outlineExperimental outline

RNA sample

3 HLB cell lines

0, 5+200, and 200 cGySample RNA and protein at 4h after challenge dose

2 Affy “U95A”chips per dose

x 3 doses = 18 chips

IR

12,000+genes

The radioadaptive response is variableThe radioadaptive response is variable

Sorensen K.J., et. al., (2002) Mutat Res. 519:15-24.

Binucleated cellwithout

micronucleus

Binucleated cell withmicronucleus

k value = Ratio ofMicronucleus Frequenciesof Priming vs. Non-Primingdose (5+200/200 cGY).

- Cell lines chosen for the initial gene expression studies

Gene expression can be associated with the radioadaptiveoutcome

Cell line response:268 Radioadaptive responder115 Radioadaptive responder036 non-responder

4 hrs post IR

268 cell line268 cell line



Pairwise comparison of radiodaptive and 2 Gy doses

12592 4768 1775

Genes on array U95A Genes detected (Bioconductor/RMA)

Genes with significant F-ratio p-value < 0.05

Selection of radioadaptive genes

*Genes with significant p-value < 0.2 *Genes with significant p-value < 0.1 *Genes with significant p-value < 0.05

520 340 145

* genes with an effect >1.8 fold

Possible radioadaptive genes

Radioadaptive effects across 3 cell lines?

How many genes are effected?

IR effects in lymphoblastoid cells

A set of 520 gene transcripts were selected for further analyses.

0 vs. 5+200 or 200 cGy

5+200 vs. 200 cGy

We identified 4 gene important groupsof genes

• Gene group 1 - Expression all up, independent of ARoutcome - changes associated with IR response~ 60 genes

• Gene group 2 - Expression all down, independent of ARoutcome - changes associated with IR response~ 70 genes

• Gene group 3 - Lower expression associated with ARoutcomes - associated with chromosomal damage levels~ 80 genes

• Gene group 4 - Higher expression associated with ARoutcomes - associated with chromosomal damage levels~ 50 genes

Common priming dose effects independent of AR

Protein synthesis Metabolism/signal transduction

Gro

up 2

EBI2SLAMGM2APRDX4

SQLEPORIMIN

W28612GLDC

AI768188TRA1SEC63HNRPH3HTGN29MGC2840

CANXAL031659AL080234

ITGB1LAMP2

DAFATP1B1

Gro

up 1

RPL28RPS15a

RPL8EIF3S2GNB2L1

RPS11RPL14RPS20

RPL6RPS10

RPS3EEF1A1RPL27ARPL23A

RPS17RPL19RPL12RPL13A

RPS27RPS20RPS24RPS23RPS3ARPL11

RPS6RPL31

GM15036 GM15510 GM15268

Fold

Cha

nge

GM15036 GM15510 GM15268

Fold

Cha

nge

GM

1551

0G

M15

268

GM

1503

6G

M15

510

GM

1526

8

GM

1503

6

1

2

0 0.5 1 1.5 2 2.5 3 3.5

2

4

6

8

1

Gene

Gene

Cluster analysis identifies genes associated with low dosepriming dose, independent of radioadaptive response outcomes

GeneMRPS27SUI1ATF4EIF4A1PSMB9TPM4

GM15036 GM15510 GM15268

TXNRD1

MYCETR101

STK24PIM2ADFPPDLIM1

GNB1DCTDGARSCCNIWARSCCL4JUNDSFRS6

Fold

Cha

nge

ACTG1SP100

ATMMYL6LDHBHSPA8HSPA8

MPHOSPH10P125

RES4-25FRG1

SUCLA2CBF2CBF2CETN3

PRDX1SAP18

NBPATP5INME1PSMA4ERCC5

C2FARPC2HSPA8

EBNA1BP2DLAT

Fold

Cha

nge

MTIF2

PSMC1FSCN1

RTCD1MEP50PABPC1

BLNKSRP14

HSPD1PSMD10

LDHBCREM

DKFZP564F0522DIA1EIF2S1

IFI30DDX42

LPXN

Gro

up 4

Gro

up 3

GM15036 GM15510 GM15268

GM

1551

0G

M15

268

GM

1503

6

GM

1551

0G

M15

268

GM

1503

6

SSRP1PMM2BZRPTRAABUB3KIAA0111ODC1H3F3BGADD45ASERP1NUDT3KIAA0084POLE3EDF1PABPC4RGS1NXF1TTC3CASP8SRFBTG1SFRS2NFKB1HAX1SPAG7KPNB2FLJ10803

1

2

3

0 1 2 3 3.5

IFNAR2W26496CCL3BRD2DUSP5CD48OAS1FADS1HLA-DRB1

1

2

34

Gene

Cluster analysis identifies genes associated with radioadaptiveoutcomes

Table 4. Genes with relatively higher fold changes in

expression when the cell does not adapt (Group 3 )

fold change

Gene

Accession

number

GM

15036

GM

15510

GM

15268

Ratio of

effecta

SCYA4 J04130 3.3 0.03 0.03 110.0

SCYA3 D90144 2.5 0.2 0.1 16.7

ATF5 AB021663 7.8 0.7 0.6 12.0

IFNAR2 L42243 2.7 0.3 0.2 10.8

JUND X56681 3.2 0.3 0.4 9.1

SFRS6 AL031681 3.2 0.3 0.4 9.1

SARS X91257 8.2 1 0.8 9.1

ETR101 M62831 3.7 0.6 0.4 7.4

LITAF AF010312 6.5 1.2 0.6 7.2

EIF4A1 D13748 4.8 1.1 0.6 5.6

GARS U09510 3.1 0.7 0.4 5.6

MYC V00568 3.9 0.5 0.9 5.6

TM9SF2 U81006 0.8 0.2 0.1 5.3

CD48 M37766 2.1 0.4 0.4 5.3

OAS1 X04371 2.1 0.4 0.4 5.3

ADFP X97324 3.4 1 0.3 5.2

PIM2 U77735 3.6 0.9 0.5 5.1

NP X00737 6.7 1.5 1.2 5.0

PRKDCIP U85611 5.8 1.4 1 4.8

WARS X59892 2.9 0.8 0.4 4.8

Table 5. Genes associated with the adaptive outcome with

higher expression in the adapting cell lines (Group 4 )

fold changes

Gene

Accession

number

GM

15036

GM

15510

GM

15268

Ratio of

effectsa

NKTR NM_005385 0.2 6.9 4.3 28.0

PSMC6 D78275 0.2 1.9 1.2 7.8

PFTK1 AB020641 0.2 1.5 1.3 7.0

MPHOSPH10 X98494 0.5 3.2 2.5 5.7

MTIF2 AF494407 0.3 1.5 1.6 5.2

CRM1 Y08614 0.2 1.1 0.9 5.0

RDX L02320 0.2 0.9 1.1 5.0

TCF12 M80627 0.3 1.2 1.8 5.0

CETN3 AI056696 0.5 2.1 2.6 4.7

FLJ20720 FLJ20719 1.1 5.9 4.1 4.5

PSMA6 X59417 0.3 1.7 0.9 4.3

ZNF148 AJ236885 0.3 1.8 0.8 4.3

C2F U72514 0.5 2.8 1.5 4.3

ERCC5 L20046 0.5 2.8 1.5 4.3

SMARCA2 X72889 0.2 1 0.7 4.3

DDX42 AB036090 0.4 1.4 1.6 3.8

HSPA8 P11142 0.8 3.1 2.7 3.6

EIF2S1 BC002513 0.5 1.8 1.7 3.5

EBNA1BP2 U86602 0.6 2.3 1.8 3.4

DKFZP564F0522 AK027432 0.5 1.9 1.5 3.4

Large ratio’s of effect were associated with AR outcomes

Multiple cellular functions Multiple cellular functions

- 3

- 2

- 1

0

1

2

3

4

Hs_amino acid activation

Hs_tRNA l igase

Hs_tr anscr iption r egulation 7

Hs_ubiquitin C- terminal hydr olase

Hs_ATP binding 5

Hs_tr anscr iption r egulation, fr omPol I I pr omoter

Hs_l igand binding or car r ier 12

Hs_ox idor eductase

Hs_hydrolase 10

Non-radioadaptive

Radioadaptive

Three Cell Lines

z-score

* - showing differential expression > 1.8 fold

GO MAPS*

Specific cellular pathways were not modulatedwhen associated with radioadaptive outcomes

1053 Gene Ontology maps were searched with 641 genes, the maps shown are for those that gave a z-score > 2

- 2

- 1

0

1

2

3

4

5

6

Hs_lysosome

Hs_antimicr obial humor al r esponse(sensu Inver tebr ata)Hs_protein car r ier

Hs_small molecule tr anspor t 2

Hs_cell- cel l signal ing

Hs_cytoplasm 9

Hs_intr acel lular 31

Hs_cell- cel l adhesion

Hs_cell 21

Hs_cell 9

Hs_membrane fr action 9

Hs_r esponse to exter nal stimulus 6

Non-radioadaptive

Radioadaptive

Three Cell Lines

z-score

* - showing differential expression > 1.8 fold

GO MAPS*

Specific cellular pathways were modulated when associated with radioadaptive conditions

1053 Gene Ontology maps were searched with 1209 genes, the maps shown are for those that gave a z-score > 2

DNA damage response, activation of p53-ATM-BTG2-CHES1

Telomere maintence-DKC1

Oxidative stress response-ATOX1-PDLM1-SCYA22-SCYA3-SCYA4-SCYA5-SOD1

Examples of genes from the “resistance toinfection” pathway

Unfolded protein responses-HERPUD1

Response to viruses-IFNAR2-TNF

Host pathogen related responses-NFKB1-NFKB1A-NSEP1-PABPC4-STAT1-E1B-AP5

DNA damage response, activation of p53-ATM-BTG2-CHES1

Telomere maintence-DKC1

Oxidative stress response-ATOX1-PDLM1-SCYA22-SCYA3-SCYA4-SCYA5-SOD1*

Examples of genes from the “resistance toinfection” pathway

Unfolded protein responses-HERPUD1

Response to viruses-IFNAR2-TNF

Host pathogen related responses-NFKB1-NFKB1A-NSEP1-PABPC4-STAT1-E1B-AP5

Pathway Priming dose genes Radioadaptive genes

Response Group

Group 1, common “up” response after priming do s e

Group 2, Common “down”

response after priming dose

Group 3, Differential response, Lower in adapting cell

l ines

Group 4, Differential response, Higher in adapting cell

l ines

Apoptosis CD53, PORIMIN, TNFRSF10B

CASP8, DAD1, HAX1, NFKB1, TNF, TNFRSF17

Cell Adhesion CD58, ENTPD1, ITGB1, KIAA0911 CD44, CD164 ICAM2

Cell Cycle RB1 WEE1

CCNI, BTG1, BUB3, EDF1, EMP3, MYC PIM2, SRF, PRKDCIP

CETN3, MPHOSPH10, P125

Chemokine CCL3, CCL4, SCYA5, SCYA22, SCYA3, SCYA4 CRM1

DNA Repair PRKDC PRKAR1A ATM, ERCC5, SP100, NBP

Immune response CD48, IFITM1, HLA-DMA, HLA-DMB, TCRA BLNK, NKTR

Metabolism ODC1, RPS13

ARL6IP, CD9, CYP1B1, EBP, ENTPD1, GGH, GLDC, GM2A, GUSB, HMGCR, KIAA0004,

KIAA0088, LAMP1, LAMP2, PPT1, SLC2A5, SLC9A6, SPTLC1, TFRC, ZMPSTE24

AHCY, ADA, IDH2 IDH3G, ODC1, PMM2 SC5DL, SIAT1

DLAT, FDFT1, LDHB OS9, SUCLA2

Protein degradation

KIAA0317, RPN2, RZF, TL132, USP9X

CTSC, EDD, PSEN1, SPAG7, UBE21

IFI30, PSMA4, PSMC1, PSMC6, PSMD10, USP6

Protein Biosythesis

RPL (5, 6, 8 – 12, 13A, 14, 15, 17, 19, 18A, 21, 23, 23A, 24, 27A, 28 – 32, 34, 38), RPLP0, RPLP1, RPS (2, 3, 3A, 4X, 5 – 11, 14, 15A, 17, 19, 20, 23, 24, 27),

EEF1A1, EEF1G FMR1, CANX, MRPS6 EIF3S5, EIF4A1, E2EPF

RNA metabolism DDX3, HNRPH3, RNP24

DDX21, NXF1, PABPC1,

SFRS2, SFRS6

DDX42, RTCD1 PABPC1,

RTCD1

Signal Transduction

DRES9, GNB2L1, TEBP

ADAM10, AKAP1, ATP1B3, ASAH, CD19, CD59, CNIH, CR2, EBI2, EPB72, SLAM, SORL1, TNFRSF8

AMFR, BZRP, GNB1, IFNAR2, NUDT3, PRKCB1, RGS1, STAT1, STAT3, SSRP1, STK24, VEGFB, YWHAZ

CREM, CTNNB1, EBNA1,BP2, LPXN, PFTK1, YWHAQ, TTK

Stress Response

HADH2 HSPA5, PDIA3, PDIA6, PRDX4, SQLE

HERPUD1, GADD45A, MTRR, LITAF, SERP1, TXNRD1

DIA1, HSPA8, HSPD1, IFI30

Transcription DRAP1, NSEP1 H-SP1, TRA1, CHD1,

ATF5, EIF4A2, ETR101, JUND, SMARCA4, T CEA1

CBF2, DEK, SMARCA2, TCF12, ZNF148

Translation

GARS, SARS, WARS, YARS

EIF2S1, MTIF2, NARS, RARS

Major pathwaysinvolved in thecommon primingdose effect and theradioadaptiveresponse wereidentified within ourdata.

Gene interaction map derived from transcript modulation in adaptingand non-adapting cell lines

ATM

IRIR

Stress response

CHK2

TP53

p21

MYC

PML,, SP100

HSP8AHSP8A, , HSPD1

CBF2 + P73 +

FUSE ++ P89 Helicase

SSRP1 + CK2

Rb + + ID2ID2

p16

NBS, MRE11RAD50

JUNDJUND

RAS

DNA Repair

Apoptosis

GADD45AGADD45A

CyclinD

TNFaTNFa

NFKB1

CASP3 CASP8

IFI30 IFI30 PSMC6 PSMA6 USP6

ERCC5

Cell Cycle Control

YWHAQ (14.3.3)

MAPK38

STAT1 STAT3

WEE1

PRKCB1PRKDC

0

0.5

1

1.5

2

2.5

3

3.5

p125 ATM MYC p125 ATM MYC

A.Microarray B. RT-PCR

Fold

Diff

eren

ce

Genes up-regulated in adaptive cellsGenes down-regulated in adaptive cellsGenes down-regulated in adaptive cellsGenes modulated by the 5 Genes modulated by the 5 cGy cGy priming dosepriming doseGenes known to be in the same pathways Genes known to be in the same pathways

Low dose IR influenced the post-challenge dose transcriptionalLow dose IR influenced the post-challenge dose transcriptionalresponse of cell in three waysresponse of cell in three ways

METABOLISMPROTEIN SYNTHESIS

DNA REPAIRSTRESS RESPONSEAPOPTOSISCELLULAR PROLIFERATION

DNA REPAIRSTRESS RESPONSEAPOPTOSISCELLULAR PROLIFERATION

Responses predictive ofAR outcome

Responses predictiveof non-AR outcome

Priming-Dose responsesindependent of the ARoutcomes

Priming Dose +Challenging Dose(5 + 200 cGy)

GREEN - gene groups with down-regulated expression RED - gene groups with up-regulated expression

Summary1. Cytogenetic radioadaptive response was observed 60% of the time in

HLB cell line.

2. AR was observed in two cell lines which shared similar globalpatterns of gene expression signals that was different from theexpression profile of a non-adapting cell line.

3. We found 5 cGy induced transcript profiles that were:- independent of AR outcome- associated with AR outcome (less chromosome damage)- associated with non-AR outcome (no change in chromosomedamage)

4. Genes associated with adaptation are part of a complex DNA damagesignaling pathway, possibly mediated by the TP53-related pathway.

Future studies

• Examine the time course of the mRNA and proteinprofiles before and after the challenge dose exposure inHLB cells.

• Characterize the corresponding proteomic responsesfor low-dose and radioadaptive responses.

• Extend the studies to in vivo tissues to test theprediction that transcript modulation of panels ofgenes will lower the risk for chromosomal damage intissues susceptible to radiation-induced cancers.

LLNL, Biosciences A. WyrobekEric YinB. SouzaF. PearsonK. Sorensen

LLNL, ComputationsDave Nelson

Wayne StateJ. Tucker

Baylor College of MedicineL. Peterson

Funded by grants from DOE, NIH and DTRA

Acknowledgements

Understanding cellular responses modulated by low doses of...

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