Gm. Halliday et al., SPONTANEOUS REGRESSION OF HUMAN-MELANOMA NONMELANOMA SKIN-CANCER - ASSOCIATION WITH INFILTRATING CD4(-CELLS() T), World journal of surgery, 19(3), 1995, pp. 352-358
Spontaneous regression occurs in some human malignant melanomas and ba
sal cell carcinomas (BCCs). We have compared the cellular infiltrate i
n regressing and nonregressing tumors in order to analyze the mechanis
m by which regression occurs. Regressing primary melanomas and BCCs we
re infiltrated with a larger number of CD4(+), but not CD8(+) T lympho
cytes than were seen in nonregressing tumors. The number of interleuki
n 2 receptor-positive (early activation marker) but not transferrin re
ceptor-positive (intermediate activation marker)T cells was increased,
indicating that the infiltrating T cells were activated. Large number
s of Langerhans cells, macrophages, and other class II major histocomp
atibility complex (MHC)-expressing cells were present but were not inc
reased in the regressing tumors. There were no detectable B lymphocyte
s, and the regressing tumor cells displayed levels of HLA-DR expressio
n similar to those of the nonregressing tumors. Comparison of squamous
cell carcinoma (SCCs) with keratoacanthomas (KAs), which are likely t
o be a spontaneously regressing form of SCC, also showed increased inf
iltration of activated CD4(+), but not CD8(+), T cells within the KA.
A murine ultraviolet (UV)-induced squamous tumor that spontaneously re
gresses when transplanted into immunocompetent syngeneic mice was also
infiltrated with increased numbers of activated CD4(+), but not CD8(), T cells prior to and during rejection. These results indicate that
spontaneous regression of human skin tumors is likely to be immunologi
cally mediated, and that CD4(+) T lymphocytes seem to mediate this reg
ression.