Purpose A subset of T cells essential for inhibitory properties such as self-tolerance termed regulatory T cells (Treg) has recently been described in patients with cancer. This expanded pool of inhibitory cells has been described in ovarian, lung, and other epithelial cancers. The current study is to evaluate whether patients with pancreatic cancer exhibit expanded Treg pools and whether this correlates with expanded tumor infiltrating lymphocytes (TILs) in the tumor bed.
Experimental Design During the period from June 2005 to the present, 21 patients admitted for possible Whipple surgery and 13 controls underwent flow cytometry to evaluate T-cell subset compartment. Flow cytometry for total CD4+, CD8+, CD25+, and coexpression were performed. In nine patients in whom Whipple surgery was successful, immunohistochemistry (IHC) was performed for these subsets.
Results Patients with pancreatic cancer showed a trend toward an expanded pool of Treg subset in comparison with controls. Patients with pancreatic cancer had 45.5% (SD 15.5) of CD4+ compartment coexpressing CD25+, typical of Treg expression, in comparison with controls of 35.4% (SD 16.2). The p value was .08. There was no difference in CD8+ percentage in comparison with controls. In eight of nine patients in whom tumor was resected, peripheral blood was consistent with the number of TILs that were CD4+CD25+. In peripheral blood, the ratio of CD4:CD8 was 1.3:1, not significantly different from controls. However, in resected specimens, the ratio of CD4:CD8 TILs was 30:1 by IHC.
Conclusion Our data provide evidence of a trend toward expanded Treg pool in patients with pancreatic cancer. It shows evidence that peripheral blood expansion of Tregs is reflective of tumor bed infiltration. Lastly, our data suggest that peripheral blood CD8 values are not reflective of TILs. Further study with a larger sample size is warranted for confirmation of findings.
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