Hlffi,
H,E
,F
#
nd
*t+A)
Su Song-Xi
INVESTIGATE
THE
CAUSES
OF
CANCER
While
at
a
molecular
level
there
may
be "a final
common
pathway"
in
the etiology
of
cancer,
the
interplay of a number of fac-
tors
is considered
to
be respon-
sible for the development of
ma-
lignant
disease.
These
include
genetic, viral, chemical, and physi-
cal
factors,
as well as
the response
of
the
host.
Genetic
factors
play
an
im-
portant role in some of the com-
mon types
of
tumors
-
s6l6n 3nd
breast cancers for
instance.
The
risk
of
developing breast cancer
in
the first degree relatives of a
pa-
tient
is
fivefold
that
of
the
general
population.
Viruses have
been
demonstrated to cause leukemia
in
a
number of mammalian
and
other
species.
The
most impor-
tant established chemical carcino-
gen
in
man's environment at the
moment
is
cigarette
smoke.
The
fact that tumors occur with
in-
creased frequency
in
patients with
congenital deficiencies and also
in
patients with acquired or
induced
immunologic deficits have resulted
in
the "immunologic surveillance"
hypothesis.
lntensive investigation con-
cerning
the
etiology
of
human
neoplasia
is
currently
under way,
and
definitive
results indicate
that
neoplasia develops
insidiously
and
perhaps
in
a stepwise
fashion,
as
illustrated
by
studies
of
the
respi-
ratory
tract tumors
of
smokers.
Up
to a point, the progressive
changes
may be
stopped
or even
reversible,
if
the
inciting factors
cited
above
is removed.
A gen-
eral understanding
of
these newer
knowledge is important and use-
ful
to physicians and the lay popu-
lation, alike.
#|rffifr<rffifr
,#*t+ea-ffi
FFAAW#J*)J
,E'+T+AflEil
tr
HofiB'i
"
f&ffietE4€+,HrH
+€.194K'fi
'
}EEEE€€GMTN
&
4-+
*W
EE
ttrE
Fg
FrE*s
Eg
€'
H&ffiIR
"
)r-^AF
rfl
E €'lE
E
H'
*E
EO
lt
#EEt
, flFM
'tEjetE#trE7E++
*.fffi.h
rffi
ffi
E@,,
rffi
ffi
E@,xEt+
M.
ffi,
,
d#J*ffi"ffi.'lg,'
€Bf
ffi.,\ie
Efi
mt,
H
fr<J
FTJAE#
ffi
F-YA
+.
E?
#*6tx,tqA '
'ffiffi.H|V,
4-
+rJE
-
fr€
-
iE€&.HE*
,d+nH.HH.&ffi6, Erffi++tr*
eH-re-ffi|,4
"
+)\Zffi#JE
,
7EtrffiFl#ffi- I*'I+T
,hEM,
ffi,*.**.^4@W+^rffift'
Rd
t6't
W)\*
@
#
+
rffi
ft.
?
E
#J
rffi
ffi^d€Haq.-'
tlra.i,H€.Hs(h
tffifr-,\jfYq€.fiffiz'g-
?
E&'E
'l+*.ffi
fr+J
)-,
F.A
t6r9-F!€S
tY.H
rE
fr.'
ffi,X*
*.4.iftItttB^
€
w
4Y.
H, tE
ft
?
rE+t+
4
^ffi
#tJ
^&+
AF€.
t*4
zJ'IFIE,
]fi
rt-s
zJrffi
IEH'f+MA€ffiA4HHEFAEI
F,#ttffi,fr.
?
d4r.t\#HiEHffin@,ZFn
u
rffi
ffi
,
+4
8
#E€g
ft,rE
trt
fte,W.
TEtrtsrr
,ffi+E*s*+ffifr
,
*ItH
Ht#JHffi
"
+#2o'K+ffi
ETrfr.soo
&U,EF.,\
,
Tffi4fi,4r1
7e,Eft
+ s
rF,ft
ft
ffi
F!
I
€
&3R
#+*,tr+H9€efl
Yft,
RF't6
}ffiE'+.ffi
,
Igffi€F*+#ffi*.
ffi
,Fne.Ee*-Eftt+T
"
#*{E
1p*7,-
?E.^trWeft&ffih
ffi4ft.,€eHF€t68ffi
,hErt+
TWffi*
,
)LF-EIJTffi'JEF.4T.
W,
t&+X*tuEhFC
" iEjEEfi
Frffi?+
EEr
*
-
'ffiffiFrffi
51ftsffi
ER
-
Atr^
4+'
D)&-{ffiffifrEd.rJt
wwR
7t
afiF*r €8.{E
rE'
H
#E
EE
^
#
+
H.IEEL
tr
+
AF€,
&',!-g.
H!'EELtr,
NB@..'
€tr9'EE!t8E-ft4+MrE:nd,1*1+T
7fE*
9.,
I*-E H fffiEF-E.Hffiffiffi
'
tE*EBEx
f+.4t
Mre)ft'd.'l*4+
T
'
€-Htevfltfr#.rE
,
Hffi*rE*EE
?
€
/-TffiilJE,
H4t@.lElE&EHtrFt=e
.
{*4*T,
ffix*
el,\
T€g
*.fafr
, n
A
ta'>#.
Lt
A#Hffifr.
?
t
^&ffi
?#EA.#t',7rtfd.#'rEEI
EU
;F.
#
H
TEEfl
EFQ
H*
F=1
#F€
tuE€)nEjHAtH!,
=.+lxrTtE*E,'{nH1+845t'lllflJ# )r
##
-
4iyBlF€lB/-trJflffi'
1EHTFE'(*44
"
19
