Histone Deacetylase Inhibitors Downregulate CCR4 Expression and Decrease Mogamulizumab Efficacy in CCR4-Positive Mature T-Cell Lymphomas

Background: Histone deacetylase inhibitors (HDACis) are promising agents for various T-cell lymphomas, including cutaneous T-cell lymphoma (CTCL), peripheral T-cell lymphoma (PTCL), and adult T-cell lymphoma/leukemia (ATLL). CCR4 is an important therapeutic target molecule because mogamulizumab, an anti-CCR4 antibody, has shown promising efficacy against CTCL, PTCL, and ATLL. However, their combined effects and interactions have not been examined thus far. We previously showed that CCR6, a chemokine receptor, is overexpressed in cutaneous T-cell lymphomas (Ito et al., 2014 Blood). Moreover, we recently demonstrated that HDACis downregulate CCR6 expression in advanced cutaneous T-cell lymphomas (Abe et al., 2017 Oncotarget). These reports lead us to hypothesize that HDACis might also downregulate CCR4 in various T-cell lymphomas. In this study, we clarify the effect of the combined use of mogamulizumab and HDACis on various T-cell and NK-cell lymphomas. Based on our findings, we discuss what benefits or adverse effects might be assumed for patients if these molecular targeting agents are used in clinical practice.

Methods: We evaluated changes in CCR4 expression and antibody-dependent cell-mediated cytotoxicity (ADCC) activities against mogamulizumab- and HDACi-treated T-cell and NK-cell lymphoma lines and primary cases. To determine which HDAC mainly regulated CCR4 expression, we used isoform-specific HDACis and induced knockdown of respective HDACs for T-cell lymphoma cell lines. To examine the effect of CCR4 downregulation by HDACis in clinical cases, we examined the CCR4 expression of CTCL skin samples, which were obtained from the same patients before and after HDACi treatment (n = 6).

Results: We first examined the expression of CCR4 for 15 T-cell and NK-cell lymphoma cell lines and a peripheral blood mononuclear cell (PBMC) sample derived from healthy donors to investigate the effect of vorinostat, a pan-HDACi, on CCR4 expression. The expression of CCR4 was mostly expressed in the (11 out of 15) cell lines: ATLL (MT-1, MT-2, MT-4, and TL-Su), CTCL (My-La, HH, and MJ), and NK/T-cell lymphoma cell lines (Kai3, SNK6, HANK1, and SNK10). We found that vorinostat decreases mRNA expression and surface expression of CCR4 except for the cell lines without CCR4 expression. Next, we used isoform-specific HDACis to examine which isoform of HDAC is involved in the regulation of CCR4. We used the following class-specific HDACis: romidepsin as a class I selective HDACi, CI-994 as an HDAC1/HDAC2-selective inhibitor, RGFP966 as an HDAC3-selective inhibitor, ricolinostat as an HDAC6-selective inhibitor, and PCI-34051 as an HDAC8-selective inhibitor. When these drugs were exposed to T-cell lymphoma cells, romidepsin and CI-994 strongly suppressed CCR4 expression. These results suggest that class I HDACs might controls CCR4 expression. We further performed knockdown experiments using siRNAs against HDAC1, HDAC2, and HDAC3. When we compared the expression change of CCR4 in HDAC-knockdown cells, HDAC2 knockdown cells showed the most significantly decreased expression of CCR4. These results suggest that class I HDACs, especially HDAC2, might be deeply involved in CCR4 expression regulation. When we examined the CCR4 expression in skin samples from primary CTCL, obtained from the same patients before and after vorinostat treatment, we found that CCR4 expression was greatly reduced after vorinostat treatment. Finally, when we conducted an ADCC assay with mogamulizumab by using various lymphoma cell lines and primary T-cell lymphoma samples, we found that the efficacy of mogamulizumab was significantly reduced by pre-treatment with vorinostat.

Conclusion: Our results suggest that the primary use of HDACis before treatment of mogamulizumab might not be suitable to obtain synergistic effects. Moreover, these results provide potential implications for optimal therapeutic sequences in various CCR4 positive T-cell and NK-cell lymphomas.