CCR4 inhibition did not reduce the proportion of infiltrating leukocytes in the tumor microenvironment but altered the phenotype of myeloid cells, increased NK cell and Th1 cytokine levels, and reduced immature myeloid cell infiltrate and blood chemokine levels. Th1/Th2 regulation. The anti-CCR4 antibody, alone or in combination with other immune modulators, is usually a potential treatment approach to human solid cancers with high levels of CCR4-expressing tumor-infiltrating leukocytes and abnormal plasma CCR4 ligand levels. Introduction Tumor microenvironments possess complex chemokine networks that contribute to the extent and phenotype of the host infiltrate (1C3). In addition, malignant cells may gain functional chemokine receptors, often as a consequence of oncogenic mutations, allowing them to respond to distant chemokine gradients during metastatic spread (4, 5). The chemokine receptor CCR4 is usually expressed on circulating and tissue-resident T cells, being predominantly associated with a Th2 phenotype (6C8), as well as on other T helper cells (9). CCR4 is also highly expressed on circulating Tregs and on Tregs recruited at tumor sites in ovarian malignancy (10) and in glioblastoma (11). In ovarian malignancy, the CCR4 ligand CCL22 is found both in the tumor tissue and in macrophages isolated from ascitic fluid (9). In hepatocellular carcinoma, malignant cellCproduced CCL22 recruited CCR4+ Tregs that facilitated immune escape of malignant cells (12). Similarly, in breast malignancy, CCR4+ Tregs, recruited by CCL22 in the tumor microenvironment, are CEP-37440 predictive of a worse prognosis (13). A second breast cancer study found reduced overall survival and high CCR4 expression in tumor biopsies (14). Finally, in a cohort of 753 patients with gastric adenocarcinoma, positive staining for CCR4 was also associated with a poorer prognosis (15). CCR4 also plays a role in hematological malignancies, and there are now clinical trials of an anti-CCR4 antibody, mogamulizumab, that has enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity. Mogamulizumab is usually approved in Japan for the treatment of relapsed adult T cell leukemia (ATL) (16) and has also been tested in patients with relapsed peripheral CEP-37440 T cell lymphoma (PTLC) and cutaneous T cell lymphoma (CTLC) (17). The treatment is usually indicated for patients with CCR4-positive leukemia cells, but might also take action by reducing the number of Tregs in malignancy patients (18). In this article, we have investigated CCR4 as a target in renal cell carcinoma (RCC) using patient samples and an orthotopic mouse RCC model. Tnfsf10 We have found abnormal levels of CCR4 and its ligands in human RCC biopsies and plasma samples. In preclinical experiments we found that Affi-5, a fully human anti-CCR4 antibody with antagonistic activity (explained in ref. 19), has antitumor activity CEP-37440 in a renal malignancy model. Inhibition of CCR4 did not reduce the proportion of CCR4-positive infiltrating leukocytes in the tumor microenvironment but altered the phenotype of the immune infiltrate, affecting in particular the phenotype of myeloid cells and increasing the number of infiltrating NK cells. These effects were dependent on the adaptive immune system and required functioning CD4+ T cells. The antibody also altered the phenotype of tumor-associated macrophages (TAMs) in the B16 melanoma model. Inhibition of CCR4, alone or in combination with other immune modulators, may be a valuable therapeutic approach in human cancers with high levels of CCR4 in the tumor microenvironment and abnormal plasma CCR4 ligand levels. Results CCR4 and its ligands in human renal cell carcinoma. This study was prompted by the obtaining of abundant mRNA in biopsies from renal cancers as compared with normal kidney (Physique 1A). CCR4 protein was also detected by IHC on malignant cells and leukocytes in a tissue microarray (TMA) constructed from 57 advanced RCC patient biopsies (Physique 1B and Supplemental Physique 1A; supplemental material available online with this short article; https://doi.org/10.1172/JCI82976DS1). Of the 173 cores in the TMA, 157 showed positive CCR4 staining. 75% of the biopsies were classified as obvious cell, with others classified as papillary RCC. There was a significant positive correlation between CCR4 positivity and the CEP-37440 considerable T cell (CD3+) or macrophage (CD68+) infiltrates in the tumor cores (Supplemental Physique 1, BCD), suggesting that CCR4 may be important in the trafficking of tumor-associated leukocytes. Open in a separate window.