A causative relationship between chronic inflammation and cancer has been postulated for many years, and clinical observations and laboratory experiments support the hypothesis that inflammation contributes to tumor onset and progression. However, the precise mechanisms underlying the relationship are not known. We recently reported that the proinflammatory cytokine, interleukin-1B, induces the accumulation and retention of myeloid-derived suppressor cells (MDSC), which are commonly found in many patients and experimental animals with cancer and are potent suppressors of adaptive and innate immunity. This finding led us to hypothesize that inflammation leads to cancer through the induction of MDSC, which inhibit immunosurveillance and thereby allow the unchecked persistence and proliferation of premalignant and malignant cells. We now report that host MDSC have receptors for prostaglandin E2 (PGE2) and that E-prostanoid receptor agonists, including PGE2, induce the differentiation of Gr1 + CD11b + MDSC from bone marrow stem cells, whereas receptor antagonists block differentiation. BALB/c EP2 knockout mice inoculated with the spontaneously metastatic BALB/c-derived 4T1 mammary carcinoma have delayed tumor growth and reduced numbers of MDSC relative to wild-type mice, suggesting that PGE2 partially mediates MDSC induction through the EP2 receptor. Treatment of 4T1-tumor-bearing wild-type mice with the cyclooxygenase 2 inhibitor, SC58236, delays primary tumor growth and reduces MDSC accumulation, further showing that PGE2 induces MDSC and providing a therapeutic approach for reducing this tumor-promoting cell population. [Cancer Res 2007;67(9):4507-13]

Tumor cells aberrantly express chemokines and/or chemokine receptors, and some may promote tumor growth and metastasis. We examined the expression and function of chemokine receptor CXCR3 in a syngeneic murine model of metastatic breast cancer. By flow cytometry, CXCR3 was detected in all murine mammary tumor cell lines examined. All human breast cancer cell lines examined also expressed CXCR3, as did the immortalized but nontumorigenic MCF-10A cell line. Interaction of CXCR3 ligands, CXCL9, CXCL10, and CXCL11, with CXCR3 on the highly malignant murine mammary tumor cell line 66.1 resulted in intracellular calcium mobilization and chemotaxis in vitro. To test the hypothesis that tumor metastasis is facilitated by CXCR3 expressed by tumor cells, we employed a small molecular weight antagonist of CXCR3, AMG487. 66.1 tumor cells were pretreated with AMG487 prior to i.v. injection into immunecompetent female mice. Antagonism of CXCR3 on 66.1 tumor cells inhibited experimental lung metastasis, and this antimetastatic activity was compromised in mice depleted of natural killer cells. Systemic administration of AMG487 also inhibited experimental lung metastasis. In contrast to the antimetastatic effect of AMG487, local growth of 66.1 mammary tumors was not affected by receptor antagonism. These studies indicate that murine mammary tumor cells express CXCR3 which facilitates the development of lung metastases. These studies also indicate for the first time that a small molecular weight antagonist of CXCR3 has the potential to inhibit tumor metastasis. (Cancer Res 2006; 66(15): 7701-7)

Recurrent solid malignancies are often refractory to standard therapies. While adoptive T cell transfer may benefit select individuals, the majority of patients succumb to their disease. In order to address this important clinical dilemma, we developed a mouse melanoma model in which initial regression of advanced disease was followed by tumor recurrence. During recurrence, Foxp3+ tumor-specific CD4+ T cells became PD-1+ and represented over 60% of the tumor-specific CD4+ T cells in the host. Concomitantly, tumor-specific CD4+ T effector cells showed traits of chronic exhaustion as evidenced by their high expression of the PD-1, TIM-3, 2B4, TIGIT, and LAG-3 inhibitory molecules. While blockade of the PD-1/PD-L1 pathway with anti-PD-L1 antibodies or depletion of tumor-specific Treg cells alone failed to reverse tumor recurrence, combination of PD-L1 blockade with tumor-specific Treg cell depletion effectively mediated disease regression. Furthermore, blockade with a combination of anti-PD-L1 and anti-LAG-3 antibodies overcame the requirement to deplete tumor-specific Treg cells. In contrast, successful treatment of primary melanoma with adoptive cell therapy required only Treg depletion or antibody therapy, underscoring the differences in the characteristics of treatment between primary and relapsing cancer. These data highlight the need for preclinical development of combined immunotherapy approaches specifically targeting recurrent disease.

Breast tumor cells express the chemokine receptor CXCR3, which binds the ligands CXCL9, CXCL10, and CXCL11. CXCR3 and other chemokine receptors may mediate tumor metastasis by supporting migration of tumor cells to sites of ligand expression including the lymph nodes, lungs, and bone marrow. We examined the relationship of CXCR3 expression to clinical outcome in 75 women diagnosed with early-stage breast cancer. We detected CXCR3 in malignant epithelium from all tumors. Twelve percent were weakly positive and 64% had moderate levels of CXCR3. Strong CXCR3-positive staining was observed in 24% of tumors. Kaplan-Meier survival curves showed that high CXCR3 expression was associated with poorer overall survival; the unadjusted hazard ratio was 1.56 and it was marginally significant (P = 0.07). When interactions between lymph node status and CXCR3 were considered, the adjusted hazard ratio for CXCR3 was 2.62 (P = 0.02) for women with nodenegative disease at diagnosis, whereas the hazard ratio for CXCR3 was not significant for those with node-positive disease. CXCR3 gene silencing inhibited lung colonization and spontaneous lung metastasis from mammary glandimplanted tumors in a murine model. The size or growth rate of the locally growing tumors was not affected. The antimetastatic effect of CXCR3 gene silencing was compromised in mice depleted of Natural Killer cells or with mutations in IFN-;, suggesting that the role of CXCR3 is not simply to mediate tumor cell trafficking. These studies support the continued examination of CXCR3 as a potential therapeutic target in patients with breast cancer. [Mol Cancer Ther 2009;8(3):490 -8]