Increased levels of immune inhibitory CD34+ progenitor cells in the peripheral blood of patients with node positive head and neck squamous cell carcinomas and the ability of these CD34+ cells to differentiate into immune stimulatory dendritic cells.

OBJECTIVES: This study determined whether mobilization of immune inhibitory CD34+ cells by head and neck squamous cell carcinomas (HNSCC) is most prominent in patients who are node positive and whether these CD34+ cells could differentiate into immune stimulatory dendritic cells. STUDY DESIGN AND SETTING: Peripheral blood from patients with head and neck cancer was used to measure the frequency of CD34+ cells and their capacity to differentiate into immune stimulatory dendritic cells. RESULTS: This study demonstrated that increased CD34+ cell levels were most prominent in patients who were node positive and patients with recurrent disease. These CD34+ cells differentiated into dendritic cells that were able to present tetanus toxoid to autologous T-cells. CONCLUSIONS: Immune suppressive CD34+ cells that are prominent in patients with HNSCC who are node positive are able to develop into immune stimulatory dendritic cells. SIGNIFICANCE: Differentiation of tumor-mobilized CD34+ cells into dendritic cells may be an immunotherapeutic approach to stimulate antitumor reactivity.

Impact of aging on immune modulation by tumor.

Tumor development and aging can each alter immune competence. The present study aimed to determine the impact of Lewis lung carcinoma (LLC) presence on immune parameters of middle-aged (averaging 6.5 months) versus aged (averaging 21.3 months) mice. An age-associated decline in the CD4+ cell frequency was seen in freshly isolated spleen and lymph node cells, as well as in cultures stimulated with immobilized anti-CD3. This decline was not further exacerbated by tumor presence. What was prominently inhibited by tumor was the capacity of either splenic or lymph node CD4+ cells to become stimulated to express IFN-gamma. Spleen and lymph node cultures from aged tumor-bearing mice had the lowest frequency of CD4+IFN-gamma+ cells and the least amount of secreted IFN-gamma. CD8+ cells were not affected by aging, but tumor presence reduced the induction of CD8+IFN-gamma+ cells in lymph node cultures. We previously showed that LLC growth stimulates myelopoiesis, as seen by splenomegaly and the mobilization of immune inhibitory CD34+ progenitor cells. Tumor presence in middle-aged mice reduced spleen cell blastogenesis, which was mediated by CD34+ cells. Aged mice had reduced blastogenesis, and this was further reduced by presence of tumor. However, neither the age-associated immune dysfunction nor the tumor-induced immune suppression in aged mice was due to CD34+ progenitor cells. These studies show how tumor presence can further compromise the immune dysfunction that accompanies aging. In addition, they show that aging impacts on the mechanisms by which tumors inhibit T-cell capabilities, with myelopoiesis-associated CD34+ cells mediating the immune depression of middle-aged tumor-bearers and an independent mechanism being responsible for the immune depression in aged tumor-bearing mice.

Human squamous cell carcinomas of the head and neck chemoattract immune suppressive CD34(+) progenitor cells.

CD34(+) progenitor cells have previously been shown to be mobilized in patients with squamous cell carcinoma of the head and neck (HNSCC). The present study showed that these CD34(+) cells inhibit the capacity of intratumoral lymphoid cells to become activated in response to stimulation through the TCR/CD3 complex. The mechanisms that could lead to the accumulation of CD34(+) cells within the tumor tissue were assessed. This was accomplished through in vitro studies that determined if HNSCC produce soluble factors that chemoattract CD34(+) cells. The migration of cord blood CD34(+) cells, which were used as a readily available source of progenitor cells, was stimulated by products derived from HNSCC explants and primary HNSCC cultures. This stimulated migration was due to chemotaxis because it was dependent on an increasing gradient of HNSCC-derived products. CD34(+) cells that were isolated from the peripheral blood of HNSCC patients were similarly chemoattracted to the HNSCC-derived products. The majority of the chemotactic activity produced by HNSCC could be attributed to vascular endothelial cell growth factor (VEGF). These studies indicate that HNSCC can chemoattract immune inhibitory CD34(+) progenitor cells through their production of VEGF.

Chemoattraction of femoral CD34+ progenitor cells by tumor-derived vascular endothelial cell growth factor.

Patients and animals with GM-CSF-producing tumors have an increased number of mobilized CD34+ progenitor cells within their peripheral blood and tumor tissue. These CD34+ cells are inhibitory to the activity of intratumoral T-cells. The present study used the murine Lewis lung carcinoma (LLC) model to assess mechanisms that could lead to the accumulation of CD34+ cells within the tumor tissue. In vitro analyses showed that LLC tumor explants released chemoattractants for normal femoral CD34+ cells. The LLC tumor cells contributed to the production of this activity since CD34+ cell chemoattractants were also released by cultured LLC cells. Antibody neutralization studies showed that most, although not all, of the chemotactic activity that was produced by LLC cells could be attributed to VEGF. In vivo studies with fluorescent-tagged CD34+ cells showed their accumulation within the tumor tissue, but not within the lungs, spleen or bone marrow, suggesting a selective accumulation within the tumor. Whether or not VEGF could chemoattract CD34+ cells in vivo was measured with a VEGF-containing Matrigel plug assay. Infusion of fluorescent-tagged CD34+ cells into mice after the plugs became vascularized revealed the accumulation of fluorescent-tagged cells within the plugs. However, these CD34+ cells failed to accumulate within the VEGF-containing Matrigel plugs when they were infused together with neutralizing anti-VEGF antibody. Through a combination of in vitro and in vivo analyses, the LLC cells were shown to be capable of chemoattracting CD34+ cells, with most of the tumor-derived chemotactic activity being due to tumor release of VEGF.