Iron Overload Dick Wells

Outline ¡ A functional definition of iron overload

¡  Iron toxicity – from atoms to organs

¡  Treatment of iron overload

Am I overloaded yet? A functional definition of iron overload

Andrews NC. N Engl J Med. 1999;341:1986–1995

Body Iron Distribution

There is no physiologic mechanism to remove excess iron

1 % blood cells digested/d 25 mg iron released

ferroportin

spleen

Fe(III)

Fe(II)

Fe

Absorption of iron balances daily loss

ferroportin

Transferrin iron is used for production of new blood cells

Hepcidin  blocks  ferropor0n,  preven0ng  iron  export  into  plasma  

Hepcidin

Iron released into plasma is incorporated into transferrin

TfSat normally 0.2-0.55 (No non-Tf-bound iron)

DMT1

ferritin

hephaestin

Labile ceIl iron

Dcyb

Fe(III) Fe(II)

Fe(III) Fe(II)

duodenum

The Iron Balance

ferroportin

Transfusion therapy results in iron overload

¡  Normal iron influx through gut is 1–2 mg/day

¡  1 blood unit contains 200-250 mg iron

¡  Iron overload can occur after 10–20 transfusions

Iron from transfused

RBC

Iron from increased absorption

Free Iron: The Essence of Iron Overload

100%

30%

Normal: no free iron produced Iron overload

Subsequent formation of free

iron in plasma

Saturation of transferrin due to •  Frequent blood transfusions, and •  Ineffective erythropoiesis leading to

increased iron absorption

Fe

Fe Fe

Fe Fe

Fe Fe

Uncontrolled iron loading of organs

Pituitary

Parathyroid Thyroid

Heart Liver Pancreas

Gonads

Tran

sfer

rin s

atur

atio

n %

“Free” Iron

Haem biosythesis

Fe-S cluster biogenesis

Fe(II) Fe(III)

Fe(III) Fe(III) Transferrin

Transferrin receptors

DMT1

Fe(II)

Ferritin

Other Fe utilization pathways

Dcyb

Endosome Mitochondria

LCI (Labile cell iron)

Free iron in our cells

Plasma

Summary Iron Balance ¡  There is no mechanism for excreting excess iron

¡  Iron normally is associated with proteins ¡  Haemoglobin and enzymes

¡  Transferrin (plasma transport)

¡  Ferritin (intracellular storage)

¡  “Free” iron is rare

¡ When iron stores are high, free iron appears in the plasma and can get into cells

What problems are caused by

free iron?

Iron supports dangerous radicals

Iron Toxicity: From Atoms to Organs

Fe

Iron and Free Radicals ¡  Cell metabolism produces hydrogen

peroxide (H2O2) as a biproduct

¡  H2O2 is not itself very toxic

¡  Reactive oxygen intermediate (ROI)

¡  Free iron reacts with H2O2 to form highly toxic free radicals

¡  Reactive oxygen species (ROS)

Fe3+ Fe2+

Free iron

LCI

O2

H2O2

O2-

OH.

ROI

ROS

Mitochondria

Lipid Protein

DNA

Cellular targets of labile iron

TfR

DMT

DMT-Divalent metal transporter TfR-Transferrin receptor ROI-reactive oxygen intermediates ROS-reactive oxygen species

Regulated Unregulated

Saturated transferrin

Cellular Effects of Free Iron

O2

OH.

Altered signaling Proliferation

Fibrosis

Apoptosis Mutagenesis

Membrane damage Cell lysis

Inefficient energy metabolism Apoptosis

Senescence

What problems do these cellular effects

cause in organs?

Uncontrolled iron loading of organs

Pituitary

Parathyroid Thyroid

Heart Liver Pancreas

Marrow

Gonads

Iron Overload Morbidity and Mortality

Hepatic fibrosis ! Cirrhosis

Arrhythmia

Hypogonadism

Diabetes

Hypothyroidism

Hypoparathyroidism

Cardiomyopathy

~ 7 g iron

How do we know these problems are

caused by iron?

Surv

ival

(%)

0

60

80

50

40

30

20

10

70

90

100

0 28 26 24 22 20 18 16 14 12 10 8 6 4 2 30 32 34 36 38 40 Time (years)

300–365 225–300 150–225 75–150 0–75

Infusions/year

Iron Overload Effect of iron chelation

Chelation = survival

Are the effects of iron the same, no matter what the

underlying disease?

Comparison of organ dysfunction in thalassaemia major and sickle cell disease

Vichinsky E. Am J Hematol. 2005;80:70-4. NS = not significant.

Characteristic Thalassaemia major

Sickle cell disease

p value

Age 18.4 ± 2.1 14.8 ± 1.0 NS Duration of transfusion 12 years 6 years Serum ferritin (µg/L)

2,122 ± 289 2,916 ± 233 0.04

Liver iron (mg Fe/g dry wt)

14.8 ± 2.2 14.3 ± 1.4 NS

Transfusions (n/year)

12.2 ± 1.8 6.0 ± 0.6 0.002

Cardiac disease 20% 0% 0.002

Gonadal failure 33% 0% < 0.001

Growth delay 27% 9% NS

Hypothyroidism 7% 0% NS

Viral hepatitis 33% 2% < 0.001

Fibrosis 81% 29% 0.02

Factors 1.  Duration of transfusion 2.  TM vs. SCD

Why should this be?

Despite similar Fe measures, SCD patients have fewer end-organ complications

O2

H2O2

O2-

ROI OH.

ROS

Inflammation Primes the Antioxidant Response

GPX-glutathione peroxidase SOD-superoxide dismutase ROI-reactive oxygen intermediates ROS-reactive oxygen species

H2O Catalase GPX SOD

Inflammatory State (SCD)

Cytokines

NRF2

Inflammation in SCD primes the antioxidant response and reduces Fe-catalyzed ROS

Fe

What is the effect of iron overload

in MDS?

Does iron overload contribute to mortality in MDS?

Sanz et al., Blood 2008 112 (abstract 640)

Registry data Overall survival

by serum ferritin level (n=762)

<1000 1000-1500

>2500 1500-2000

Prop

ortio

n su

rviv

ing

40 80 120 Survival (months)

RA, RARS, 5q-

?

Malcovati et al., Haematologica, 2007

MDS Classification: Causes of death in MDS

!"#

$!"#

%!"#

&!"#

'!"#

(!!"#

)*+,-./0# 1.23,-./0#

456.-789#

:.-789#

!"#$%&'()&*$

+,-.*/0,$

12..(),3$

456.'$

“Direct”

“Indirect”

The goals of therapy are different in low-risk and high risk MDS

Malcovati et al., J. Clin. Oncol. 2005 Balduini et al., Hematologica 1999

The heart in MDS

Goldberg et al., ASH 2008

“MDS cardiomyopathy”: chronic anaemia + iron overload + the aged myocardium

Rates of heart disease in US

medicare patients

0 20 40 60 80 100

Medicare database

MDS

MDS (transfused)

MDS (not transfused)

Cardiac iron in patients with MDS

N Cardiac iron

Units transfused

Serum ferritin (µg/L)

Chelated

Jensen et al. 2003 12 9 44–254 (median 115)

1,740–8,715 0

Chacko et al. 2007 11 1 23–257 (median 112)

1,109–6,651 6

Konen et al. 2007 10 1 50–140 (median 89)

1,260–4,450 7

Di Tucci et al. 2008 26 2 14–234 (median 69)

T2*< 20 at > 100 units

1,300–6,241 2

Pascal et al. 2010 76 14 -- 282-7339 54

Di Tucci AA, et al. Haematologica. 2008;93:1385-8. Chacko J, et al. Br J Haematol. 2007;138:587-93.

Jensen PD, et al. Blood. 2003;101:4632-9. Konen E, et al. Am J Hematol. 2007;82:1013-6. Pascal et al., ASH 2010, Abstract 2906

HOWEVER: There is no obvious relationship between cardiac iron and heart problems in

MDS

Should iron chelation be given in MDS?

Ferroscepticism ¡  DeLoughery TG. Iron: The

fifth horseman of the apocalypse? Am J Hematol. 2009

¡  Steensma DP. Myelodysplasia paranoia: iron as the new radon. Leuk Res. 2009

¡  Tefferi A, Stone RM. Iron chelation therapy in myelodysplastic syndrome—Cui bono? Leukemia. 2009

Data?

TELESTO

Iron chelation and survival in MDS Leitch (Clin Leuk Res 2008) ¡  178 pt ¡  OS in ICT >160 mo ¡  OS in non-ICT = 40 mo ¡  p<0.03

¨  Rose (ASH 2007) ¡  170 pt ¡  OS 115 vs. 51 mo ¡  p< 0.0001

¡  Fox (ASH 2009) ¡  186 pt (matched pairs) ¡ OS in ICT = 75 mo ¡ OS in non-ICT = 49 mo ¡  P=0.002

Fox Blood 2009; 114 (abstract 1747)

¡  Lower-risk MDS if life exp > 1y

¡  Higher-risk MDS if BMT candidate

¡  Either desferal or exjade as first line

¡  Target ferritin < 1000 ng/mL

Fe(II)

Ferritin

Translation LCI

(Labile cell iron)

Direct and Indirect Measurement of Iron

Ac0ve  IRP  

Blocks  ferri0n  mRNA  

Ferritin IRE  

IRP

Fe(II)

Serum ferritin

LIC

Ø Biopsy Ø MRI Ø SQUID

MRI = magnetic resonance imaging; SQUID = superconducting quantum interference device.

Unexpected effects of iron in MDS

Iron and Haematopoiesis in MDS

Analysis of trial data to study haematological responses in the MDS patients in EPIC (N=341)

Gattermann et al., ASH 2010, Abstract 2912

Overall erythroid response rate = 22.6%

Iron and AML in MDS

How could IOL promote development of AML?

o  Fe causes DNA damage in vitro o  Fe accelerates development of

AML in mouse model

Chan et al., ASH 2010, Abstract 122

HSC MDS AML

Iron

ROS

Loss  of  mitochondrial  membrane  poten0al  

Loss  of  respiratory  enzyme  ac0vi0es    

Apoptosis  Lipid  peroxida0on   DNA  muta0on  

Liver  cirrhosis  Endocrine  

disturbances  Cardiac  failure  

Iron  overload  

Free  ironà  LCI  à  ROS      

Summary Iron Toxicity

BM  suppression   MDS  à  AML  

Blood transfusion Increased Fe absorption

Conclusions ¡  Iron is both essential and toxic -- balance is

maintained by an intricate network of proteins

¡ Chronic RBC transfusion overwhelms this network, resulting in the presence of “free iron”, which causes cell and organ damage via generation of free radicals

¡  Fe toxicity leaves different footprints in TM, SCD, and MDS

¡ Chelation therapy can prevent chronic Fe toxicity but must be monitored by indirect (ferritin) or direct (LIC) means

Any questions?