Anti-LGALS3 monoclonal antibody, clone 303324

Galectin 3 (LGALS3) expression is prognostic for poor survival in acute myeloid leukemia (AML) patients. GCS-100 is a novel galectin inhibitor that may prove useful for AML therapy. In this study, we found that GCS-100 induced apoptosis in AML cells. The agent reduced MCL-1 expression suggesting that GCS-100 could be more effective when combined with a BH3 mimetic. Indeed, potent synergistic cytotoxicity was achieved when GCS-100 was combined with ABT-737 or ABT-199. Furthermore, the GCS-100/ABT-199 combination was effective against primary AML blast cells from patients with FLT3 ITD mutations, which is another prognostic factor for poor outcome in AML. This activity may involve wild-type p53 as shRNA knocicdown of LGALS3 or galectin 1 (LGALS1) sensitized wild-type p53 OCI-AML3 cells to GCS-100/ABT-737-induced apoptosis to a much greater extent than p53 null THP-1 cells. Suppression of LGALS3 by shRNA inhibited MCL-1 expression in OCI-AML3 cells, but not THP-1 cells, suggesting the induced sensitivity to ABT-737 may involve a MCL-1 mediated mechanism. OCI-AML3 cells with LGALS1 shRNA were also sensitized to ABT-737. However, these cells exhibited increased MCL-1 expression, so MCL-1 reduction is apparently not required in this process. A role for p53 appears important as GCS-100 induces p53 expression and shRNA knockdown of p53 protected OCI-AML3 cells from the cytotoxic effects of the GCS-100/ABT-737 treatment combination. Our results suggest that galectins regulate a survival axis in AML cells, which may be targeted via combined inhibition with drugs such as GCS-100 and ABT-199. (C) 2015 Elsevier B.V. All rights reserved.

Background: The HIV-1 infection is characterized by profound CD4(+) T cell destruction and a marked Th17 dysfunction at the mucosal level. Viral suppressive antiretroviral therapy restores Th1 but not Th17 cells. Although several key HIV dependency factors (HDF) were identified in the past years via genome-wide siRNA screens in cell lines, molecular determinants of HIV permissiveness in primary Th17 cells remain to be elucidated. Results: In an effort to orient Th17-targeted reconstitution strategies, we investigated molecular mechanisms of HIV permissiveness in Th17 cells. Genome-wide transcriptional profiling in memory CD4(+) T-cell subsets enriched in cells exhibiting Th17 (CCR4(+)CCR6(+)), Th1 (CXCR3(+)CCR6(-)), Th2 (CCR4(+)CCR6(-)), and Th1Th17 (CXCR3(+)CCR6(+)) features revealed remarkable transcriptional differences between Th17 and Th1 subsets. The HIV-DNA integration was superior in Th17 versus Th1 upon exposure to both wild-type and VSV-G-pseudotyped HIV; this indicates that post-entry mechanisms contribute to viral replication in Th17. Transcripts significantly enriched in Th17 versus Th1 were previously associated with the regulation of TCR signaling (ZAP-70, Lck, and CD96) and Th17 polarization (ROR gamma t, ARNTL, PTPN13, and RUNX1). A meta-analysis using the NCBI HIV Interaction Database revealed a set of Th17-specific HIV dependency factors (HDFs): PARG, PAK2, KLF2, ITGB7, PTEN, ATG16L1, Alix/AIP1/PDCD6IP, LGALS3, JAK1, TRIM8, MALT1, FOXO3, ARNTL/BMAL1, ABCB1/MDR1, TNFSF13B/BAFF, and CDKN1B. Functional studies demonstrated an increased ability of Th17 versus Th1 cells to respond to TCR triggering in terms of NF-kappa B nuclear translocation/DNA-binding activity and proliferation. Finally, RNA interference studies identified MAP3K4 and PTPN13 as two novel Th17-specific HDFs. Conclusions: The transcriptional program of Th17 cells includes molecules regulating HIV replication at multiple post-entry steps that may represent potential targets for novel therapies aimed at protecting Th17 cells from infection and subsequent depletion in HIV-infected subjects.