
[Cancer Research 60, 5002-5006, September 15, 2000]
© 2000 American Association for Cancer Research
p53 Is Essential for Chemotherapy-induced Hair Loss1
Vladimir A. Botchkarev2,
Elena A. Komarova,
Frank Siebenhaar,
Natalia V. Botchkareva,
Pavel G. Komarov,
Marcus Maurer,
Barbara A. Gilchrest and
Andrei V. Gudkov2
Department of Dermatology, Boston University School of Medicine, Boston, Massachusetts 02118 [V. A. B., F. S., N. V. B., B. A. G.]; Department of Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607 [E. A. K., P. G. K., A. V. G.]; Department of Dermatology, Johannes Gutenberg University, D-55101 Mainz, Germany [F. S., M. M.]; and Quark Biotech, Inc., Pleasanton, California 94566 [P. G. K.]
 |
ABSTRACT
|
|---|
Anticancer drugs stimulate apoptosis in the hair follicles (HF) and
cause hair loss, the most common side effect of chemotherapy. In a
mouse model for chemotherapy-induced hair loss, we demonstrate that p53
is essential for this process: in contrast to wild-type mice,
p53-deficient mice show neither hair loss nor apoptosis in the HF
keratinocytes that maintained active proliferation after
cyclophosphamide treatment. HF in p53 mutants are characterized by
down-regulation of Fas and insulin-like growth factor-binding protein 3
and by increased expression of Bcl-2. These observations indicate that
local pharmacological inhibition of p53 may be useful to prevent
chemotherapy-associated hair loss.
 |
Introduction
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Cancer treatment with chemotherapeutic agents is associated with
severe side effects due to the occurrence of apoptosis in several
sensitive tissues (such as the hematopoietic system or epithelia of
digestive tract) as a result of drug cytotoxicity (1)
.
This apoptosis largely depends on p53, a key mediator of cellular
mechanism of stress response (2)
. p53 accumulation in
sensitive cells after a variety of stresses results in growth arrest at
one of the cellular checkpoints or induction of programmed cell death
(3)
. p53 acts as a nuclear transcription factor altering
expression of multiple p53-responsive genes, the activity of which is,
at least in part, responsible for cell reaction to stress (2
, 3)
. The major role of p53 in mediating the side effects of
cancer treatment was confirmed by the isolation and application
of a chemical inhibitor of p53 that reduced the toxicity of cancer
treatment in experimental animals by temporary reversible suppression
of p53 (4)
.
Temporary hair loss (alopecia) is a common side effect of chemotherapy.
HF3
are "hair shaft-producing miniorgans" showing during postnatal life
a unique pattern of cyclic activity with periods of relative resting
(telogen), active growth (anagen), and apoptosis-driven involution
(catagen) (5)
. HF are strongly affected by many
chemotherapeutic agents because of the rapid proliferative rate of hair
matrix keratinocytes during anagen. In the mouse model of
chemotherapy-induced hair loss, the active hair growth phase was first
induced by depilation, and cyclophosphamide administration during new
anagen phase causes complete alopecia imitating changes seen in human
chemotherapy-induced hair loss (6
, 7)
. The drug treatment
induces dystrophic changes in growing HF and, in more severely damaged
follicles, premature regression as a result of massive apoptosis
in the entire proximal hair bulb, with subsequent hair shedding
(6
, 7)
.
Apoptosis of hematopoietic cells and cells of the digestive tract
associated with cancer treatment is known to be p53 dependent
(2, 3, 4
, 8)
. Radiation- or chemotherapy-induced DNA damage
leads to the rapid accumulation of p53 protein in the susceptible cells
(3
, 9)
, followed by up-regulation of Fas, IGF-BP3, and
Bax, encoded by the corresponding p53-responsive genes
(10, 11, 12)
. Moreover, it was demonstrated that Fas and Bax
are up-regulated in the HF during cyclophosphamide treatment
(13)
and that p53 is involved in the ionizing
radiation-induced apoptosis in the HF (14)
.
To explore the role of p53 in the hair loss induced by chemotherapeutic
agents, we used a mouse model for chemotherapy-induced hair loss:
cyclophosphamide treatment of C57BL/6 mice after hair cycle
synchronization in anagen by depilation (6
, 7
, 13)
. We
analyzed the expression of p53 in the HF of drug-treated wild-type mice
and then compared the dynamics of HF of wild-type versus
p53-deficient mice after cyclophosphamide treatment. We demonstrate
here that p53 is indeed essential for the development of
chemotherapy-induced hair loss in mice.
 |
Materials and Methods
|
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Animal Models and Tissue Collection.
Female 8-week-old C57BL/6 mice (n = 20), 8-
to 10-week-old p53 knockout (n = 25), and
wild-type mice (n = 25) were purchased from
Charles River (Boston, MA) and The Jackson Laboratory (Bar Harbor, ME).
p53 knockout mice generated on C57BL/6 background were viable, showed
apparently normal fur, and developed spontaneous tumors not earlier
than 12 weeks after birth (15)
, i.e., after the
end of experiment. Mice were housed in community cages at the animal
facilities of the Boston University School of Medicine and University
of Illinois at Chicago. All mice were fed water and murine chow
ad libitum and were kept under 12-h light/dark cycles.
Active hair growth (anagen) was induced in the back skin by application
of a wax-rosin mixture with subsequent depilation, as described before
(6
, 7
, 13)
. On day 9 after hair cycle induction (at anagen
VI stage of the hair cycle), a single i.p. injection of 150 mg/kg
cyclophosphamide (Endoxan; Bristol Meyers Squibb, Princeton, NJ) or PBS
(vehicle control) was given as described previously (6
, 7
, 13)
. Skin samples were harvested at days 1, 3, 5, 7, 9, and 11
after cyclophosphamide administration (at days 10, 12, 14, 16, 18, and
20 postdepilation, respectively). Harvesting of skin and cryosectioning
were performed by a special technique to obtain longitudinal sections
of the HF, as described previously (6
, 7
, 13)
.
Immunohistochemistry and TUNEL Technique.
Expression of p53 protein, p55 TNF receptor, and IGF-BP3 was assessed
with the use of rabbit polyclonal antiserum against murine p53
(Novocastra, Newcastle upon Tyne, United Kingdom), rat monoclonal
antibody against murine p55 TNF receptor (PharMingen, San Diego, CA),
and rabbit polyclonal antiserum against IGF-BP3 (Santa Cruz
Biotechnology, Santa Cruz, CA), respectively. Tyramide amplification
was used for the visualization of these antigens, as described
previously (16
, 17)
. Double immunovisualization of p53 and
TUNEL or proliferative marker Ki-67 and TUNEL was performed, as
described previously (18)
. For immunovisualization of
Ki-67, a rabbit polyclonal antiserum against murine Ki-67 was obtained
from Dianova (Hamburg, Germany).
Immunodetection of Fas, p75 neurotrophin receptor, Bax, and Bcl-2 was
performed with corresponding monoclonal antibodies and the
avidin-biotin-alkaline phosphatase method, as described previously
(13
, 17)
. Histoenzymatic detection of the endogenous
alkaline phosphatase was performed for the precise identification of
dermal papilla morphology in HF of the distinct stages of
apoptosis-driven involution (catagen) (6
, 7
, 13
, 16
, 17)
.
 |
Results and Discussion
|
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p53 Is Up-Regulated in Hair Follicles after Cyclophosphamide
Treatment.
To determine the p53 involvement in the pathogenesis of
chemotherapy-induced hair loss, we first compared the expression of p53
in actively growing HF in the back skin of vehicle-treated and
cyclophosphamide-treated C57BL/6 mice. Active hair growth (anagen) was
induced by depilation as described before (6
, 7
, 13)
, and
cyclophosphamide was administered 9 days postdepilation,
i.e., at the time point when all HF have reached the stage
of active hair shaft production (anagen VI).
Twenty-four hours after cyclophosphamide administration (10 days
postdepilation), HF treated by vehicle control showed a relatively weak
expression of p53 in the proximal outer root sheath and hair matrix,
associated with absence of TUNEL-positive cells (Fig. 1A)
. In contrast, cyclophosphamide-treated HF displayed a
strong up-regulation of p53 in the proximal outer and inner root
sheaths and hair matrix (Fig. 1B)
. In the HF after
cyclophosphamide treatment, many TUNEL-positive apoptotic cells located
in the HF matrix were also p53 positive (Fig. 1B)
.

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Fig. 1. Up-regulation of p53 and TUNEL in the
cyclophosphamide-treated hair follicles of C57BL/6 mice. The hair cycle
was induced in the back skin of 8-week-old C57BL/6 mice by depilation,
and cyclophosphamide was administered 9 days after. Skin was harvested
at the indicated time points after cyclophosphamide administration, and
cryosections (8 µm thick) were processed for double
immunovisualization of p53 and TUNEL. Cell nuclei were visualized by
TO-PRO-3 staining. A, control (day 10
postdepilation). Weak expression of p53 (red fluorescence) in the HF
matrix (arrows) and outer root sheath
(ORS; arrowheads); B, 1
day after cyclophosphamide administration (day 10 postdepilation).
Prominent expression of p53 (red fluorescence) and colocalization of
p53 and TUNEL (yellow fluorescence) in the HF matrix (small
arrows). Prominent expression of p53 alone in the outer root
sheath (large arrowheads) and inner root sheath
(small arrowheads). Numerous TUNEL-positive cells are
visible in the hair matrix (green fluorescence) and in the hair shaft
(large arrow); C, 3 days after
cyclophosphamide administration (day 12 postdepilation). Prominent
expression of p53 (red fluorescence) and colocalization with TUNEL
(yellow-orange fluorescence) in the regressing outer root sheath
(large arrowheads) and inner root sheaths
(arrow). Numerous TUNEL-positive cells (green
fluorescence, small arrowheads) are also visible in the
inner root sheath; D, 9 days after cyclophosphamide
administration (day 18 postdepilation). Shortening of HF length is
completed and is associated with absence of TUNEL in the HF epithelium,
whereas relatively weak expression of p53 is present in the HF
connective tissue sheath (arrow). DP,
dermal papilla; HM, hair matrix; HS, hair
shaft; IRS, inner root sheath; Mel,
melanogenic area. ORS, outer root sheath.
Bars, 100 µm.
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In line with previous reports (6
, 7
, 13)
, 3 days after
cyclophosphamide administration (12 days post depilation), HF
showed a shortening of their length caused by the massive apoptosis in
the proximal hair bulb. This was associated with prominent p53
expression and colocalization of p53 and TUNEL in the regressing outer
and inner root sheaths (Fig. 1C)
. At day 7 after
cyclophosphamide administration (day 16 postdepilation), all
cyclophosphamide-treated animals showed massive hair loss in the entire
back (not shown), and 2 days later the process of
cyclophosphamide-driven HF regression was almost complete. At this
time, no p53 immunoreactivity or TUNEL positivity were seen in the HF
(Fig. 1D)
.
p53 Knockout Mice Do Not Show Cyclophosphamide-induced Hair Loss.
To test the role for p53 in the control of cyclophosphamide-induced
apoptosis in the HF and hair loss, we compared the effects of
cyclophosphamide on actively growing HF of p53 knockout
versus wild-type mice. Animals were treated by
cyclophosphamide 9 days postdepilation as described previously
(6
, 7
, 13)
. Seven days after cyclophosphamide treatment
(16 days postdepilation), wild-type mice showed extensive hair loss
over the entire back associated with dramatic shortening of HF length
and massive apoptosis in the regressing HF compartments (Fig. 2
, A, B, and D).

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Fig. 2. p53 knockout mice treated by cyclophosphamide do not
display hair loss. Hair cycle was induced in the back skin of
8-week-old wild-type (n = 25) and
p53-null mice (n = 25) by depilation, and
cyclophosphamide was administered 9 days after. Skin was harvested at
day 7 after cyclophosphamide administration (day 16 postdepilation),
and cryosections (8 µm thick) were processed for the histoenzymatic
detection of alkaline phosphatase (B and
C) and double immunovisualization of proliferative
marker Ki-67 and TUNEL (D and E). Cell
nuclei in D and E were visualized by
TO-PRO-3 staining. A, severe hair loss over the entire
back of the wild-type mice treated by cyclophosphamide, with no hair
loss visible in the p53 knockout mice. B, shortening of
the length and reduction in the volume of proximal hair bulb in the
wild-type HF (arrows) is associated with dramatic
decrease of skin thickness after cyclophosphamide treatment.
C, large volume of the proximal hair bulb
(arrows) and dermal papilla (red color) in
the p53 null HF after cyclophosphamide treatment. D,
numerous TUNEL-positive cells (green fluorescence,
arrows) and single Ki-67-positive cells (red
fluorescence, arrowhead) in the regressing HF
compartments of wild-type skin. E, numerous
Ki-67-positive cells in the HF matrix (red fluorescence,
arrowheads) and single TUNEL-positive granules in the
precortical zone (arrow). Some TUNEL-positive cells are
also visible in the subcutis around HF (green
fluorescence). Bars, 100 µm.
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However, no hair loss was seen in the cyclophosphamide-treated p53
knockout mice up to 14 days after cyclophosphamide administration. In
particular, 7 days after cyclophosphamide treatment (16 days
postdepilation), all HF in p53-null mice were in anagen VI stage. These
HF were characterized by a large volume of the proximal hair bulb and
dermal papilla, by active keratinocyte proliferation in the hair
matrix, and by single TUNEL-positive granules in the melanogenic area
above dermal papilla (Fig. 2
, A, C, and E).
Therefore, anagen HF in p53 knockout mice kept a high rate of
keratinocyte proliferation in the hair matrix and active hair shaft
production, did not show intrafollicular apoptosis, and, therefore were
resistant to the cyclophosphamide treatment. Most importantly, at days
911 after cyclophosphamide administration (1820 days
postdepilation), all HF in the p53 knockout mice showed apparently
normal patterns of physiological transformation from the active growth
to the regression and then to the resting phase (not shown).
Hair Follicles in p53-deficient Mice Are Characterized by
Down-Regulation of Fas and IGBP3, and by Increased Expression of
Bcl-2.
To identify factors that might contribute to p53-dependent
cyclophosphamide-induced hair loss, we compared the expression of
number of molecules (Fas, p55 kDa TNF receptor, p75 kDa
neurotrophin receptor, Bax, Bcl-2, IGF-BP3) implicated in the
control of cyclophosphamide-induced apoptotic cell death in the HF
(5
, 13)
. Several of the proteins analyzed (Fas, Bax,
Bcl-2, IGF-BP3) are encoded by genes, the transcription of which is
regulated by p53 during DNA damage induced by chemotherapeutic agents
(10, 11, 12
, 19)
.
We found that, in contrast to the wild-type HF treated by
cyclophosphamide, p53-null HF showed strongly reduced expression of Fas
in the proximal outer and inner root sheaths (Fig. 3, A and B)
. This observation is consistent with
the reported involvement of p53 in intracellular trafficking of Fas
receptor (10)
. Interestingly, immunoreactivity for p55
kDa TNF receptor was also reduced in the proximal outer root
sheath of the HF in p53 knockout mice, compared with wild-type animals
(Fig. 3, C and D)
. However, the expression
patterns of another member of "death domain" containing growth
factor receptors, namely p75 neurotrophin receptor, showed no
differences between wild-type and p53-null HF treated by
cyclophosphamide (Fig. 3, E and F)
.

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Fig. 3. Cyclophosphamide-treated HF of p53-null mice show
down-regulation of Fas and IGF-BP3 and up-regulation of Bcl-2. Skin
sections of wild-type (WT) and p53 knockout (-/-) mice
were analyzed at day 5 after cyclophosphamide administration (day 14
postdepilation) for immunoreactivity of Fas, p55 kDa TNF receptor
(p55 TNFR), p75 kDa neurotrophin receptor
(p75NTR), IGF-BP3, Bax, and Bcl-2. A and
B, Fas. Prominent expression of Fas in the HF outer root
sheath (A, arrows) and inner root sheath
(A, arrowhead) in wild-type skin, and weak expression of
Fas in the HF outer root sheath in p53-null skin (B,
arrows). C and D, p55 TNFR.
Wild-type HF shows p55 TNF receptor immunoreactivity in the outer root
sheath (C, arrow). Decrease of immunoreactivity in the
p53 null HF (D, arrow). E and
F, p75 NTR. Expression in the outer root sheath of
wild-type (E, arrows) and p53 null HF (F,
arrows). G and H, IGF-BP3.
Expression in the proximal outer root sheath (G, arrows)
and inner root sheath (G, arrowheads) of the wild-type
HF. Down-regulation of IGF-BP3 in the HF of p53 knockout mice
(H). I and J, Bax.
Expression in the matrix and dermal papilla (arrows) of
the wild-type (I) and p53-null HF (J).
K and L, Bcl-2. Expression in the dermal
papilla (K, arrow) and in the hair matrix (K,
arrowhead) of the wild-type HF. Up-regulation of Bcl-2 in the
dermal papilla (L, arrow) and hair matrix (L,
arrowhead) of the p53-null HF. Bar, 100 µm.
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Furthermore, the immunoreactivity for IGF-BP3 was strongly reduced in
the p53-deficient HF, compared with wild-type HF (Fig. 3, G and H)
. Bax expression was relatively unchanged in p53-null
HF, whereas Bcl-2 was highly expressed in the HF dermal papilla of 53
knockout mice, compared with that of wild-type mice (Fig. 3, IL)
.
Taken together, our data suggest that p53 is essential for triggering
apoptotic cell death in the HF that is induced by cyclophosphamide in
mice. This puts HF in the same category of other organs sensitive to
genotoxic stress, such as the hematopoietic system or epithelia of the
digestive tract, which respond to genotoxic stress by p53-dependent
apoptosis, thus limiting the tolerable doses of anticancer drugs or
radiation (2
, 3
, 8)
. Considering the similarity of
chemotherapyinduced alterations in HF of humans and mice
(6)
, we presume that p53 plays a similar role in hair loss
occurring in cancer patients during chemotherapy.
As is true for other sensitive tissues, the exact mechanism of
p53-dependent apoptosis in HF remains unclear. It may involve at least
several p53-responsive genes acting through different mechanisms. We
speculate that p53 mediates cyclophosphamide-induced apoptosis by:
(a) up-regulation of IGF-BP3 and stimulation of the
extracellular neutralization of the insulin-like growth factor-1
(IGF-1), implicated in retarding physiological transition of the HF
from active growth to apoptosis-driven regression (20)
;
(b) up-regulation of the membrane "death domain"
containing receptor Fas/Apo-1 implicated in mediating apoptosis in the
HF (13)
; and (c) modulation (reduction) of the
Bcl-2:Bax ratio in the HF triggering mitochondria-mediated apoptosis
(13)
. The relative impact of the above factors in HF
regression after chemotherapy remains to be determined.
Recently, we showed that a small molecule acting as a p53 inhibitor
efficiently reduces the side effects of ionizing radiation in mice,
presumably by suppressing p53-mediated apoptosis (4)
. We
thus presume that a local pharmacological blockade of p53 by synthetic
antagonists may provide a new therapeutic strategy for the prevention
of chemotherapy-induced hair loss, one of the most devastating side
effects of cancer treatment.
 |
ACKNOWLEDGMENTS
|
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The generous help of Dr. T. Golovkina and continued support of
Prof. J. Knop are gratefully acknowledged.
 |
FOOTNOTES
|
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported by Grant
IRG-72-001-26-IRG from the American Cancer Society to V. A. B., by
grants from the National Institutes of Health (CA75179) and Quark
Biotech, Inc., to A. V. G., and by a grant from MAIFOR (to M. M.). 
2 To whom requests for reprints should be
addressed, at Department of Dermatology, Boston University School of
Medicine, 609 Albany Street, Boston, MA 02118. Phone: 617-638-5548;
Fax: 617-638-5515; E-mail: vladbotc{at}bu.edu [V. A. B.] or 
3 The abbreviations used are: HF, hair
follicle(s); IGF-BP3, insulin-like growth factor-binding protein 3;
TUNEL, terminal deoxynucleotidyl transferase-mediated nick end
labeling. 
Received 5/31/00.
Accepted 8/ 3/00.
 |
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