Several clinical studies indicated that tumor infiltrating lymphocytes
(TILs) correlate with tumor prognosis and patient survival in many
human cancer types. However, itwas also noted that not the absolute
number of infiltrating lymphocytes but rather the ratio between the
different lymphocyte subsets had prognostic value. Tregs, as stable cellular
components of the tumor microenvironment playing a basic role
in tumor immune suppression, have been intensively investigated as
prognostic factors in patient survival and therapy response. However,
findings are quite discrepant with some studies reporting no prognostic
value of Tregs, others stating that increased Treg infiltration correlates
with poor prognosis, or, in contrary, with good prognosis. Recently
deLeeuw et al. published a comprehensive reviewabout clinical studies
investigating the prognostic value of TILs in different tumor types. Their
main conclusionswere that the prognostic value of Treg cells could be
clearly defined in certain tumors, such as hepatocellular carcinomas,
where all of the reported studies agreed on the negative prognostic value
of Tregs. In the case of colorectal cancers the reported studies either
did not find any correlation between Treg infiltration and patient survival
or reported that Treg infiltration was associated with a good
prognosis.