M. Martinsgreen et al., INFLAMMATION IS RESPONSIBLE FOR THE DEVELOPMENT OF WOUND-INDUCED TUMORS IN CHICKENS INFECTED WITH ROUS-SARCOMA VIRUS, Cancer research, 54(16), 1994, pp. 4334-4341
When newly hatched chicks are given injections of Rous sarcoma virus,
a tumor develops at the site of injection. In spite of the presence of
the virus in the blood, no other tumors are found distant from the si
te of inoculation during the life span of the animal (4-6 weeks). Howe
ver, if a wound is made away from the primary tumor, a tumor develops
at the site of wounding. Work in our laboratory showed previously that
these wound tumors do not develop as a result of metastasis, therefor
e, factors released upon wounding must contribute to the development o
f the wound tumors. In particular, we showed that transforming growth
factor (TGF) beta, a growth factor implicated in wound healing, can re
place wounding in tumor development. However, we also showed that epid
ermal growth factor and TGF-alpha, growth factors that also have roles
in wound healing, do not induce tumors. To identify the critical even
t(s) and to determine the mechanism involved in wound tumor developmen
t, we have continued these studies. Here we show that: (a) wound tumor
development correlates with the presence of circulating virus and inf
lammation; (b) the virus is present in serum and in heterophils of the
peripheral blood; (c) cell division at the site of wounding precedes
the expression of viral proteins; (d) in addition to TGF-beta, acidic
and basic fibroblast growth factors can also replace wounding in tumor
development; (e) these three factors (TGF-beta, acidic fibroblast gro
wth factor, basic fibroblast growth factor) which promote tumors also
induce inflammation, whereas epidermal growth factor and TGF-alpha do
not; and (f) during the inflammatory response, blood vessel leakage oc
curs as tested by the release of fibrinogen into the tissues. To test
the possibility that inflammation is the key element in the developmen
t of these wound tumors, we used beta-methylprednisolone, an antiinfla
mmatory drug that inhibits inflammation (including blood vessel leakag
e), to determine if wound tumor development could be prevented. We fou
nd that when inflammation was inhibited, tumors were also inhibited; w
hen inflammation could not be stopped, tumors developed as before. The
se results indicate that the effect of wounding on the development of
wound tumors in Rous sarcoma virus-infected chicks is accomplished thr
ough the cytokines released by the inflammatory cells at the site of w
ounding. These inflammatory mediators play a critical role in providin
g the conducive environment for oncogene integration and activation, a
nd subsequent development of tumors. Our results also suggest that in
humans and other mammals, the tumors that develop at the sites of chro
nic irritation may be the result of the persistent action of inflammat
ory cytokines on cellular genes that are important in the maintenance
of homeostasis. Overexpression or underexpression of these genes could
lead to deregulation of cell function culminating in transformation.