Melanoma susceptibility and progression: Association study between polymorphisms of the chemokine (CCL2) and chemokine receptors (CX3CR1, CCR5)

Cytokine Regulation of Metastasis and Tumorigenicity

The human body combats infection and promotes wound healing through the remarkable process of inflammation. Inflammation is characterized by the recruitment of stromal cell activity including recruitment of immune cells and induction of angiogenesis. These cellular processes are regulated by a class of soluble molecules called cytokines. Based on function, cell target, and structure, cytokines are subdivided into several classes including: interleukins, chemokines, and lymphokines. While cytokines regulate normal physiological processes, chronic deregulation of cytokine expression and activity contributes to cancer in many ways. Gene polymorphisms of all types of cytokines are associated with risk of disease development. Deregulation RNA and protein expression of interleukins, chemokines, and lymphokines have been detected in many solid tumors and hematopoetic malignancies, correlating with poor patient prognosis. The current body of literature suggests that in some tumor types, interleukins and chemokines work against the human body by signaling to cancer cells and remodeling the local microenvironment to support the growth, survival, and invasion of primary tumors and enhance metastatic colonization. Some lymphokines are downregulated to suppress tumor progression by enhancing cytotoxic T cell activity and inhibiting tumor cell survival. In this review, we will describe the structure/function of several cytokine families and review our current understanding on the roles and mechanisms of cytokines in tumor progression. In addition, we will also discuss strategies for exploiting the expression and activity of cytokines in therapeutic intervention.

Control of both myeloid cell infiltration and angiogenesis by CCR1 promotes liver cancer metastasis development in mice

Expression of the CC chemokine receptor 1 (CCR1) by tumor cells has been associated with protumoral activity; however, its role in nontumoral cells during tumor development remains elusive. Here, we investigated the role of CCR1 deletion on stromal and hematopoietic cells in a liver metastasis tumor model. Metastasis development was strongly impaired in CCR1-deficient mice compared to control mice and was associated with reduced liver monocyte infiltration. To decipher the role of myeloid cells, sublethally irradiated mice were reconstituted with CCR1-deficient bone marrow (BM) and showed better survival rates than the control reconstituted mice. These results point toward the involvement of CCR1 myeloid cell infiltration in the promotion of tumor burden. In addition, survival rates were extended in CCR1-deficient mice receiving either control or CCR1-deficient BM, indicating that host CCR1 expression on nonhematopoietic cells also supports tumor growth. Finally, we found defective tumor-induced neoangiogenesis (in vitro and in vivo) in CCR1-deficient mice. Overall, our results indicate that CCR1 expression by both hematopoietic and nonhematopoietic cells favors tumor aggressiveness. We propose CCR1 as a potential therapeutical target for liver metastasis therapy.

Polymorphism in the microglial cell-mobilizing CX3CR1 gene is associated with survival in patients with glioblastoma

PURPOSE

Few reliable prognostic molecular markers have been characterized for glioblastoma multiforme (GBM), considered the deadliest of human cancers. We hypothesized that genetic polymorphisms in chemokines and their receptors, which together control microglial cell mobilization, may influence survival.

METHODS

Distributions of one polymorphism of the chemokine CCL2 (-2518A<G) and two polymorphisms of the chemokine receptor CX3CR1 (termed V249I and T280M) were determined in a prospective series of 230 patients with GBM and correlated with overall survival. The replication study used data from a retrospective series of 106 additional patients with GBM. The extent of microglial cell infiltration was assessed by immunochemistry in 102 tumor specimens.

RESULTS

Survival analysis showed that the common CX3CR1-I249 allele was an independent favorable prognostic factor in both groups, prospective and retrospective, with hazard ratios of 0.619 (95% CI, 0.451 to 0.850; P = .0031) and 0.354 (95% CI, 0.217 to 0.580; P < .0001), respectively. This beneficial effect was observed only in patients who underwent surgery. Patients with only this CX3CR1-I249 allele had a substantially longer mean survival (23.5 v 14.1 months; P < .0001). The CCL2-2518G allele was not associated with patient survival. Immunohistochemical analysis of primary tumor biopsies showed that the common CX3CR1 variant allele was associated with reduced microglial cell infiltration.

CONCLUSION

The common CX3CR1 allelic variant was associated with increased GBM survival and with reduced tumor infiltration by microglia. The CX3CR1 polymorphism does not seem to be a risk factor for GBM but may prove useful in predicting survival.