Surgical Complications in Cancer Patients Probably are Not Secondary to
Immune System Defects
Jeffrey Scott Isenberg, MD, MPH, Lombardi Cancer Center, Georgetown University
It has been accepted that the immune system undergoes changes in its ability to respond
to immune challenge both with in the presence of tumor. The clinical observations of
increased infection rates and wound healing complications in cancer-bearing patients are
often attributed to this immune system defect. Some reports have documented T-cell
functional defects in both tumor-bearing mice, and in cancer patients. However, the exact
nature of and reasons for such defects and alterations of the immune system have not
been fully elucidated. The purpose of this study was to quantify specifically the effect of
tumor burden upon stem cell mobilization and immune system response. Female BALB/c
mice were treated with 4T1 breast cancer cells (1 x 105 cells) injected to the mammary fat
pad. Control mice received no such injections. Animals were matched for age and tumorbearing interval. At the time of sacrifice peripheral blood and spleens were collected and
from which light density mononuclear cells (LDMNCs) were separated via density
gradient centrifugation and utilized immediately. Assays performed included colony
forming unit count (CFU-C), INF-g output, mitogenic response and cytotoxicity. Serum
from animals was further analyzed for levels of several growth factors and cytokines
including TGF-b (both bound and unbound), G-CSF and Flt-3 ligand using standard
sandwich ELISA techniques. Finally, blood and splenic LDMNCs were tagged with
fluorescent markers and percentage distributions determined via FACS analysis. All
studies were performed in triplicate. Breast cancer bearing mice showed progressive
increase in their splenic to body weight ratios with lengthening tumor-bearing interval
(0.022 vs. 0.0048). The corresponding increase in splenic weight and size paralleled the
increased numbers of LDMNCs recovered form each organ (34 x 106 cells/spleen vs. 580
x 106 cells/spleen). Output of INF-g, a general measure of cellular inflammatory activity,
was markedly increased in LDMNCs from spleens of tumor-bearing animals in
comparison to controls as measured via the Elispot® assay (78  16 vs. 13  3).
Mitogenic response was markedly increased in cells from tumor-bearing animals as
compared to controls (0.88 vs. 1.78, normal vs. tumor-bearing). This effect was found in
cells both from the blood and spleen. Cell killing activity (cytotoxicity) against 4T1
cancer cells was likewise increased as a function of tumor-bearing interval (1.83% vs.
36.4% for normal and 3 week tumor-bearing interval at a 40:1 effector to target cell
ratio). As a measure of hematopoietic stem cell mobilization, clonogenic assays
demonstrated significant increases in CFU-C per cells plated and total CFU-C in splenic
LDMNCs from tumor-bearing animals. FACS analysis of these same cells found a
decrease in all cell lines except for Gr-1+ and Lin- Sca-1+ C-kit+ cells. Concerning output
of growth factors and other regulatory cytokines, levels of biologically active TBF-b
increased with lengthening of tumor bearing interval (2 vs. 15 ng/ml). This was in
contrast to bound levels of TBF-b, which decreased with increasing tumor-bearing
interval (360 vs 75 ng/ml). Finally, G-CSF was elevated as a function of tumor-bearing
interval (721 vs 35.8 pg/ml) as was Ftl-3 ligand (364 vs 294 pg/ml). Analysis of immune
response and stem cell mobilization of splenic LDMNCs in breast cancer bearing mice of
various ages demonstrated consistent increase in immune response by several standard
measures. Concurrent with this general increase in immune system response was
increased mobilization of stem cells to the spleen. These changes were mirrored by
elevated output from splenic LDMNCs of several cytokines including TBF-b, G-CSF and
Flt-3 ligand. These changes increased with lengthening of the tumor-bearing interval.
These results suggest that in terms of in-vitro immune activity and capacitance splenic
LDMNCs of tumor-bearing mice are competent, a situation that does not decrease with
increasing tumor-bearing interval. These immune responses occurred concurrent with
progressive stem cell mobilization to the spleen in tumor-bearing animals. Nonetheless,
the results of these experiments suggest that immune system deficiency is probably not
the reason for increased wound healing and infectious complications in post-surgical
cancer patients.