Diederichsen et al.
) showed that a low CD4/CD8 ratio by flow
cytometric analysis is an independent prognostic factor for a longer
survival by multivariate analysis. Although the study did not discriminate
the precise in situ
location of TILs, it clearly showed
that the CD4/CD8 ratio is important and that this may be
related to the current concept of the role of CD4+ CD25+ FOXP3+ regulatory
T cells in tumor tissue (17
To further analyze immune responses in colorectal cancer, Pages et
) performed a
comprehensive analysis of TILs. They focused on “early
metastatic invasion”, which included the following histopathological
findings: vascular emboli (by tumor cells), lymphatic invasion,
and perineural invasion (collectively referred to VELIPI). They
first showed that VELIPI is an independent prognostic factor in
an analysis of 959 patients. Real-time PCR analysis of 75 patients
showed that the levels of mRNAs for CD8, granzyme B, and granulysin
are higher in VELIPI-negative tumors than in VELIPI-positive tumors.
They also performed a large-scale flow cytometric analysis in 39 patients
to differentiate between naive (CD3+ CCR7+), early memory
(CD45RO+ CCR7- CD28+ CD27+) and effector memory
(CD45RO+ CCR7- CD28- CD27-) T cells in tumor tissue. VELIPI-negative
tumors contained a high proportion of mature CD8+ T cells.
Furthermore, they showed that VELIPI-negative tumors from 377 patients
contained a high number of such CD45RO+ cells by immunohistochemistry.
VELIPI-negative tumors from patients without relapse had a significant increase
in the Th1 mediator T-BET, interferon regulatory factor 1, and interferon-γ compared
to VELIPI-positive tumors from patients which had experienced a
relapse. The number of CD45RO+ cells was found to be an
independent prognostic factor, together with the TNM category, by
Cox proportional hazards regression.
There are two main reservations about this study. First, there was
no clear rationale for subdividing patients at a count of 250 cells
per square millimeter. Second, no distinction was made regarding
the intraepithelial or stromal location of CD45RO+ cells.
Despite these limitations, this study strongly supports the notion
that immune surveillance has a significant prognostic impact on
Recently, the same group extended their study of TILs in colorectal
cancer further (19
). In this
paper, they first analyzed gene expression levels by real-time PCR
in 75 patients with colorectal cancer and showed that the expression
of Th1 adaptive immunity is inversely correlated with tumor recurrence.
Particularly, patients with a homogeneously increased expression
of genes for Th1 adaptive immunity had the best prognosis. Genes
for Th1 adaptive immunity included interferon regulatory factor
1, CD3, CD8, granzyme B, granulysin, interferon-γ, and T-box 21
(TBET). They next performed immunohistochemistry for CD3, CD8, granzyme
B and CD45RO in 415 patients with colorectal cancer using tissue microarray.
In the study, they analyzed both the tumor center and invasive margin.
They showed that patients without recurrence had a higher immune
cell density in both the tumor center and invasive margin. They
confirmed these results in patients from three institutions. They
finally revealed that patients with CD3CThi
longer recurrence-free survival, while patients with CD3CTlo
shorter survival, suggesting that immune cell density is a stronger prognostic
factor than TNM staging.
The methods used in the study are innovative and the results provocative.
However, a closer look at Figure 3A in the paper shows that the
disease-free survival curve of stage III patients (with lymph node
metastasis) suddenly plateaus at 37-38 months after surgery, which
makes the survival rate of the stage III patients not so different
from that of stage I and II patients. Therefore, there is a need
for more analyses to determine whether immune cell factors are better
predictors of survival than TNM staging.