Chemokine Expression in Melanoma Metastases Associated with CD8+ T-Cell Recruitment

Abstract

Despite the frequent detection of circulating tumor antigen–specific T cells, either spontaneously or following active immunization or adoptive transfer, immune-mediated cancer regression occurs only in the minority of patients. One theoretical rate-limiting step is whether effector T cells successfully migrate into metastatic tumor sites. Affymetrix gene expression profiling done on a series of metastatic melanoma biopsies revealed a major segregation of samples based on the presence or absence of T-cell-associated transcripts. The presence of lymphocytes correlated with the expression of defined chemokine genes. A subset of six chemokines (CCL2, CCL3, CCL4, CCL5, CXCL9, and CXCL10) was confirmed by protein array and/or quantitative reverse transcription-PCR to be preferentially expressed in tumors that contained T cells. Corresponding chemokine receptors were found to be up-regulated on human CD8+ effector T cells, and transwell migration assays confirmed the ability of each of these chemokines to promote migration of CD8+ effector cells in vitro. Screening by chemokine protein array identified a subset of melanoma cell lines that produced a similar broad array of chemokines. These melanoma cells more effectively recruited human CD8+ effector T cells when implanted as xenografts in nonobese diabetic/severe combined immunodeficient mice in vivo. Chemokine blockade with specific antibodies inhibited migration of CD8+ T cells. Our results suggest that lack of critical chemokines in a subset of melanoma metastases may limit the migration of activated T cells, which in turn could limit the effectiveness of antitumor immunity.

Chemokine receptor engineering of T cells with CXCR2 improves homing towards subcutaneous human melanomas in xenograft mouse model

“…The remaining 7 chemokines analyzed by luminex (CCL5, CCL17, CCL22, CXCL9, CXCL10, CXCL11 and CXCL16) were found at negligible levels after 48 h. This is most likely due to secretion of cytokines, growth factors and chemokines by stromal cells in the tumor microenvironment, which are not represented in our luminex assay, rather than by cancer cells themselves. This is in line with findings by others, that while IHC sections or RT-PCR analyses of tumor biopsies show a wide expression of these chemokine, 18 , 29 , 30 the majority of melanoma cell lines only secretes a limited variety of chemokines, among which CXCL8/IL8 are consistently secreted at high levels. 18 , 30 It does however limit our ability to test a combination of chemokine receptors beyond CXCR2, by ACT of xenograft tumors, as the model would lack the cognate chemokine ligands.…”

“…This is in line with findings by others, that while IHC sections or RT-PCR analyses of tumor biopsies show a wide expression of these chemokine, 18 , 29 , 30 the majority of melanoma cell lines only secretes a limited variety of chemokines, among which CXCL8/IL8 are consistently secreted at high levels. 18 , 30 It does however limit our ability to test a combination of chemokine receptors beyond CXCR2, by ACT of xenograft tumors, as the model would lack the cognate chemokine ligands.…”

“…Contrary to the “pro-inflammatory” chemokines, found in a subset of patients with pre-existing TIL infiltration, 18 chemokines responsible for tumor progression through induction of angiogenesis, metastasis and recruitment of immune suppressive cell subsets such as CXCL8/IL8, CXCL12/SDF-1 and CCL22 are widely expressed in the tumor microenvironment. 18 , 19 …”

“…Despite little secretion of the corresponding ligands (CCL2 and CXCL12/SDF-1 respectively) by melanoma cell lines, these chemokines are widely secreted by stromal cells in the tumor microenvironment of melanomas. 18 , 33 Thus, efforts to augment expression of CCR2 and CXCR4 on TILs could be a strategy to increase the tumor specific homing of TILs in a setting of ACT.…”

“…Among these chemokines, CCL2, CCL3, CCL4, CCL5, CXCL9, and CXCL10 were preferentially expressed in lesions characterized by immune cell infiltration, including T cells. 18 However other chemokines are expressed in the tumor microenvironment of melanoma, such as CXCL8/IL-8, CXCL12/SDF1, 18 and CCL22, 19 which have been associated with promoting tumor growth through induction of angiogenesis, metastasis and recruitment of immune regulatory cell subsets, such as myeloid derived suppressor cells (MDSC) and regulatory T cells (Tregs). 19 , 20 …”