Selective activation of IFNγ-ipilimumab enhances the therapeutic effect and safety of ipilimumab.

INTRODUCTION: Immune checkpoint inhibitor therapy is a highly promising strategy for clinical treatment of cancer. Among these inhibitors, ipilimumab stands out for its ability to induce cytotoxic T cell proliferation and activation by binding to CTLA-4. However, ipilimumab also gives rise to systemic immune-related adverse effects and tumor immune evasion, limiting its effectiveness. OBJECTIVES: We developed IFNγ-ipilimumab and confirmed that the addition of INF-γ does not alter the fundamental properties of ipilimumab. RESULTS: IFNγ-ipilimumab can be activated by matrix metalloproteinases, thereby promoting the IFNγ signaling pathway and enhancing the cytotoxicity of T cells. In vivo studies demonstrated that IFNγ-ipilimumab enhances the therapeutic effect of ipilimumab against colorectal cancer by increasing CD8+ and CD4+ lymphocyte infiltration into the tumor area and inducing MHC-I expression in tumor cells. Mice treated with IFNγ-ipilimumab showed higher survival rates and body weight, as well as lower CD4+ and CD8+ lymphocyte activation rates in the blood and reduced organ damage. CONCLUSION: IFNγ-ipilimumab improved the effectiveness of ipilimumab while reducing its side effects. It is likely that future immunotherapies would rely on such antibodies to activate local cancer cells or immune cells, thereby increasing the therapeutic effectiveness of cancer treatments and ensuring their safety.

Discovery of aliphatic-chain hydroxamates containing indole derivatives with potent class I histone deacetylase inhibitory activities.

Histone deacetylase (HDAC) is a validated drug target for various diseases. This study combined indole recognition cap with SAHA, an FDA-approved HDAC inhibitor used to treat cutaneous T-cell lymphoma (CTCL). The structure activity relationship of the resulting compounds that inhibited HDAC was disclosed as well. Some compounds exhibited much stronger inhibitory activities than SAHA. We identified two meta-series compounds 6j and 6k with a two-carbon linker had IC50 values of 3.9 and 4.5 nM for HDAC1, respectively. In contrast, the same oriented compounds with longer carbon chain linkers showed weaker inhibition. The result suggests that the linker chain length greatly contributed to enzyme inhibitory potency. In addition, comparison of enzyme-inhibiting activity between the compounds and SAHA showed that compounds 6j and 6k displayed higher inhibiting activity for class I (HDAC1, -2, -3 and -8). The molecular docking and structure analysis revealed structural differences with the inhibitor cap and metal-binding regions between the HDAC isozymes that affect interactions with the inhibitors and play a key role for selectivity. Further biological evaluation showed multiple cellular effects associated with compounds 6j- and 6k-induced HDAC inhibitory activity.

A Flavone Constituent from Myoporum bontioides Induces M-Phase Cell Cycle Arrest of MCF-7 Breast Cancer Cells.

Myoporum bontioides is a traditional medicinal plant in Asia with various biological activities, including anti-inflammatory and anti-bacterial characteristics. To identify the bioactive constituents from M. bontioides, a newly-identified flavone, 3,4'-dimethoxy-3',5,7-trihydroxyflavone (compound 1), along with eight known compounds, were investigated in human MCF-7 breast cancer, SCC4 oral cancer, and THP-1 monocytic leukemia cells. Among these compounds, compound 1 exhibited the strongest antiproliferative activity with half-maximal inhibitory concentration (IC50) values ranging from 3.3 µM (MCF-7) to 8.6 µM (SCC4). Flow cytometric analysis indicated that compound 1 induced G2/M cell cycle arrest in MCF-7 cells. Mechanistic evidence suggests that the G2/M arrest could be attributable to compound 1's modulatory effects on the phosphorylation and expression of numerous key signaling effectors, including cell division cycle 2 (CDC2), CDC25C, and p53. Notably, compound 1 downregulated the expression of histone deacetylase 2 (HDAC2) and HDAC4, leading to increased histone H3 acetylation and p21 upregulation. Together, these findings suggest the translational potential of compound 1 as a breast cancer treatment.

HDAC8 Inhibition Specifically Targets Inv(16) Acute Myeloid Leukemic Stem Cells by Restoring p53 Acetylation.

Acute myeloid leukemia (AML) is driven and sustained by leukemia stem cells (LSCs) with unlimited self-renewal capacity and resistance to chemotherapy. Mutation in the TP53 tumor suppressor is relatively rare in de novo AML; however, p53 can be regulated through post-translational mechanisms. Here, we show that p53 activity is inhibited in inv(16)(+) AML LSCs via interactions with the CBFß-SMMHC (CM) fusion protein and histone deacetylase 8 (HDAC8). HDAC8 aberrantly deacetylates p53 and promotes LSC transformation and maintenance. HDAC8 deficiency or inhibition using HDAC8-selective inhibitors (HDAC8i) effectively restores p53 acetylation and activity. Importantly, HDAC8 inhibition induces apoptosis in inv(16)(+) AML CD34(+) cells, while sparing the normal hematopoietic stem cells. Furthermore, in vivo HDAC8i administration profoundly diminishes AML propagation and abrogates leukemia-initiating capacity of both murine and patient-derived LSCs. This study elucidates an HDAC8-mediated p53-inactivating mechanism promoting LSC activity and highlights HDAC8 inhibition as a promising approach to selectively target inv(16)(+) LSCs.

Total Synthesis of Hispidulin and the Structural Basis for Its Inhibition of Proto-oncogene Kinase Pim-1.

A new method is applied to synthesize hispidulin, a natural flavone with a broad spectrum of biological activities. Hispidulin exhibits inhibitory activity against the oncogenic protein kinase Pim-1. Crystallographic analysis of Pim-1 bound to hispidulin reveals a binding mode distinct from that of quercetin, suggesting that the binding potency of flavonoids is determined by their hydrogen-bonding interactions with the hinge region of the kinase. Overall, this work may facilitate construction of a library of hispidulin-derived compounds for investigating the structure-activity relationship of flavone-based Pim-1 inhibitors.

DUSP1 expression induced by HDAC1 inhibition mediates gefitinib sensitivity in non-small cell lung cancers.

PURPOSE: Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related death worldwide. Patients with NSCLC with EGFR-activating mutation benefit greatly by gefitinib, an EGFR tyrosine kinase inhibitor. However, acquired resistance limits its clinical use. Histone deacetylases (HDAC) are oncoproteins associated with cancer progression and drug resistance. Here, we disclosed that inhibition of HDAC1 induced protein phosphatase DUSP1 upregulation to overcome gefitinib-acquired resistance. EXPERIMENTAL DESIGN: The effect of HDAC1 inhibition restored gefitinib sensitivity was assessed by in vitro MTT and apoptotic assays, and in vivo xenograft and orthotopic lung cancer mouse models. Protein phosphatase array was used to detect DUSP1 expression. Immunohistochemical staining and quantitative PCR were used to analyze DUSP1 expression in clinical NSCLC specimens. RESULTS: Gefitinib-resistant NSCLC cells showed HDAC1 overexpression, and its knockdown sensitized resistant cells to gefitinib in vitro and in preclinical models through DUSP1 expression. Overexpression of DUSP1 in resistant cells restored gefitinib sensitivity by inhibiting EGFR signaling and inducing apoptosis, whereas its knockdown in sensitive cells conferred gefitinib resistance. A novel HDAC inhibitor, WJ-26210-2, in combination with gefitinib upregulated DUSP1 expression to exert in vitro and in vivo synergistic effect on inactivation of EGFR signaling, growth inhibition, and apoptosis. Clinically, high DUSP1 level was correlated with delayed emergence of gefitinib-acquired resistance. CONCLUSIONS: Decreased DUSP1 might be a mechanism responsible for gefitinib resistance, and DUSP1 might be a biomarker for gefitinib efficacy. HDAC1 inhibition-induced DUSP1 upregulation could be a promising strategy to overcome gefitinib-acquired resistance. Clin Cancer Res; 21(2); 428-38. ©2015 AACR.

A novel small molecule hybrid of vorinostat and DACA displays anticancer activity against human hormone-refractory metastatic prostate cancer through dual inhibition of histone deacetylase and topoisomerase I.

Vorinostat, which is an extensively studied inhibitor against histone deacetylase (HDAC), shows limited clinical activity to solid tumors. WJ35435, a new hybrid of vorinostat and DACA (a topoisomerase inhibitor) potently inhibited HDAC activity (in particular HDAC1 and HDAC6) in kinase assay and cell-based examination. The anti-HDAC effect was confirmed by the induction of histone H3 acetylation and phosphorylation, α-tubulin acetylation and γ-H2AX formation. WJ35435 showed better potency than vorinostat and DACA against PC-3 and DU-145, two human hormone-refractory metastatic prostate cancer (HRMPC) cell lines, but not benign prostate cells. WJ35435 at differential concentrations induced G1- or G2-phase arrest of the cell cycle in HRMPCs but not in benign prostate cells. WJ35435 induced the formation of topoisomerase I-DNA cleavable complexes but not type-IIα or -IIß. Topoisomerase activity assay confirmed the selective inhibition of topoisomerase I. WJ35435 induced profound DNA damage using comet tailing assay. WJ35435 was less effective than camptothecin and etoposide in inducing the phosphorylation and activation of Chk1, Chk2 and RPA32 which were crucial coordinators in DNA repair pathway, indicating a low DNA repair activity to WJ35435 action. Furthermore, WJ35435 showed an in vivo antitumor activity. A synergistic apoptosis (combination index=0.55) was obtained in combination between WJ35435 and MG-132 (a proteasome inhibitor). In summary, WJ35435 is a dual-targeted anticancer hybrid induces anti-HDAC and anti-topoisomerase I activities that cause DNA damage associated with a low DNA repair capability, and induce cell cycle arrest at G1- and G2-phase. Ultimately, WJ35435 inhibits cell proliferation and induces apoptosis of HRMPCs.

A histone deacetylase inhibitor YCW1 with antitumor and antimetastasis properties enhances cisplatin activity against non-small cell lung cancer in preclinical studies.

Many histone deacetylase (HDAC) inhibitors show limited therapeutic effects for solid tumors. Here, we develop a novel HDAC inhibitor YCW1 and verify the combination effect of YCW1 and cisplatin in lung cancer pre-clinical models. YCW1 exerted cancer-specific cytotoxicity via mitochondria-mediated apoptosis. YCW1 and cisplatin showed synergistic anti-tumor effects through impairment of DNA damage repair. YCW1 inhibited tumor growth in lung orthotopic and subcutaneously implanted xenograft models. YCW1 significantly suppressed lung metastases via inhibition of focal adhesion complex. Our findings suggested that YCW1 is a potential HDAC inhibitor for lung cancer treatment as single and in combination regimens with cisplatin.

Synthesis and biological evaluation of ortho-aryl N-hydroxycinnamides as potent histone deacetylase (HDAC) 8 isoform-selective inhibitors.

Histone deacetylases (HDACs) are a family of enzymes that play a crucial role in biological process and diseases. In contrast to other isozymes, HDAC8 is uniquely incapable of histone acetylation. In order to delineate its physiological function, we developed HDAC8-selective inhibitors using knowledge-based design combined with structural modeling techniques. Enzyme inhibitory analysis demonstrated that some of the resulting compounds (22 b, 22 d, 22 f, and 22 g) exhibited anti-HDAC8 activity superior to PCI34051, a known HDAC8-specific inhibitor, with IC(50) values in the range of 5-50 nM. Among them, compound 22 d showed antiproliferative effects toward several human lung cancer cell lines (A549, H1299, and CL1-5); it exhibited cytotoxicity against human lung CL1-5 cells similar to that of SAHA yet without significant cytotoxicity for normal IMR-90 cells. Expression profiling of HDAC isoforms in three cancer cell lines indicated that the HDAC8 level in CL1-5 is higher than that in H1299 and CL1-1 cells, a result consistent with the differential cytotoxicity of compound 22 d. These results suggest the effectiveness of our design concept, which may lead to a tool compound for studying the specific role of HDAC8 in cellular biological processes.

Synthesis and evaluation of aliphatic-chain hydroxamates capped with osthole derivatives as histone deacetylase inhibitors.

Our previous studies have demonstrated that osthole, a Chinese herbal compound, could be incorporated into the hydroxycinnamide scaffold of LBH-589, a potent HDAC inhibitor, as an effective hydrophobic cap; the resulting compounds showed significant potency against several HDAC isoforms. Here, we presented a series of osthole derivatives fused with the aliphatic-hydroxamate core of suberoylanilide hydroxamic acid (SAHA), a clinically-approved HDAC inhibitor. Several compounds showed potent activity against nuclear HDACs. Further assays against individual HDAC isoforms revealed that some compounds showed not only SAHA-like activity towards HDAC1, -4 and -6, they inhibited HDAC8 by log difference than SAHA and thus exhibited a broader HDAC inhibition spectrum. Among them, compound 6g showed potent antiproliferative effect on several human cancer cell lines.

Synthesis of N-hydroxycinnamides capped with a naturally occurring moiety as inhibitors of histone deacetylase.

Histone deacetylase (HDAC) inhibitors are regarded as promising therapeutics for the treatment of cancer. All reported HDAC inhibitors contain three pharmacophoric features: a zinc-chelating group, a hydrophobic linker, and a hydrophobic cap for surface recognition. In this study we investigated the effectiveness of osthole, a hydrophobic Chinese herbal compound, as the surface recognition cap in hydroxamate-based compounds as inhibitors of HDAC. Nine novel osthole-based N-hydroxycinnamides were synthesized and screened for enzyme inhibition activity. Compounds 9 d, 9 e, 9 g exhibited inhibitory activities (IC(50)=24.5, 20.0, 19.6 nM) against nuclear HDACs in HeLa cells comparable to that of suberoylanilide hydroxamic acid (SAHA; IC(50)=24.5 nM), a potent inhibitor clinically used for the treatment of cutaneous T-cell lymphoma (CTCL). While compounds 9 d and 9 e showed SAHA-like activity towards HDAC1 and HDAC6, compound 9 g was more selective for HDAC1. Compound 9 d exhibited the best cellular effect, which was comparable to that of SAHA, of enhancing acetylation of either alpha-tubulin or histone H3. Molecular docking analysis showed that the osthole moiety of compound 9 d may interact with the same hydrophobic surface pocket exploited by SAHA and it may be modified to provide class-specific selectivity. These results suggest that osthole is an effective hydrophobic cap when incorporated into N-hydroxycinnamide-derived HDAC inhibitors.