Trichostatin A-modified vaccine provides superior protection against ovarian cancer formation and development.

More attention has been paid to immunotherapy for ovarian cancer and the development of tumor vaccines. We developed a trichostatin A (TSA)-modified tumor vaccine with potent immunomodulating activities that can inhibit the growth of ovarian cancer in rats and stimulate immune cell response in vivo. TSA-treated Nutu-19 cells inactivated by X-ray radiation were used as a tumor vaccine in rat ovarian cancer models. Prophylactic and therapeutic experiments were performed with TSA-modified tumor vaccine in rats. Flow cytometry and ELISpot assays were conducted to assess immune response. Immune cell expression in the spleen and thymus were detected by immunohistochemical staining. GM-CSF, IL-7, IL-17, LIF, LIX, KC, MCP-1, MIP-2, M-CSF, IP-10/CXCL10, MIG/CXCL9, RANTES, IL-4, IFN-γ, and VEGF expressions were detected with Milliplex Map Magnetic Bead Panel immunoassay. TSA vaccination in therapeutic and prophylactic models could effectively stimulate innate immunity and boost the adaptive humoral and cell-mediated immune responses to inhibit the growth and tumorigenesis of ovarian cancer. This vaccine stimulated the thymus into reactivating status and enhanced infiltrating lymphocytes in tumor-bearing rats. The expression of key immunoregulatory factors were upregulated in the vaccine group. The intensities of infiltrating CD4+ and CD8+ T cells and NK cells were significantly increased in the vaccine group compared to the control group (P<0.05). This protection was mainly dependent on the IFN-γ pathway and, to a much lesser extent, by the IL-4 pathway. The tumor cells only irradiated by X-ray as the control group still showed a slight immune effect, indicating that irradiated cells may also cause certain immune antigen exposure, but the efficacy was not as significant as that of the TSA-modified tumor vaccine. Our study revealed the potential application of the TSA-modified tumor vaccine as a novel tumor vaccine against tumor refractoriness and growth. These findings offer a better understanding of the immunomodulatory effects of the vaccine against latent tumorigenesis and progression. This tumor vaccine therapy may increase antigen exposure, synergistically activate the immune system, and ultimately improve remission rates. A vaccine strategy designed to induce effective tumor immune response is being considered for cancer immunotherapy.

Induction of indoleamine 2,3-dioxygenase 1 expression in neurons of the central nervous system through inhibition of histone deacetylases blocks the progression of experimental autoimmune encephalomyelitis.

BACKGROUND: A wide array of histone deacetylase (HDAC) inhibitors and aryl hydrocarbon receptor (AHR) agonists commonly arrest experimental autoimmune encephalomyelitis (EAE). However, it is not known whether HDAC inhibition is linked to the AHR signaling pathway in EAE. METHODS: We investigated how the pan-HDAC inhibitor SB939 (pracinostat) exerted immunoregulatory action in the myelin oligodendrocyte glycoprotein 35-55 (MOG35-55)-induced EAE mouse model by evaluating changes in of signal transducer and activator of transcription 3 (STAT3) acetylation and the expression of indoleamine 2,3-dioxygenase 1 (IDO1) and AHR in inflamed spinal cords during EAE evolution. We proved the involvement of IDO1 and the AHR in SB939-mediated immunosuppression using Ido1-/- and Ahr-/- mice. RESULTS: Administration with SB939 halted EAE progression, which depended upon IDO1 expression in neurons of the central nervous system (CNS). Our in vitro and in vivo studies demonstrated that SB939 sustained the interleukin-6-induced acetylation of STAT3, resulting in the stable transcriptional activation of Ido1. The therapeutic effect of SB939 also required the AHR, which is expressed mainly in CD4+ T cells and macrophages in CNS disease lesions. Finally, SB939 was shown to markedly reduce the proliferation of CD4+ T cells in inflamed neuronal tissues but not in the spleen or draining lymph nodes. CONCLUSIONS: Overall, our results suggest that IDO1 tryptophan metabolites produced by neuronal cells may act on AHR in pathogenic CD4+ T cells in a paracrine fashion in the CNS and that the specific induction of IDO1 expression in neurons at disease-afflicted sites can be considered a therapeutic approach to block the progression of multiple sclerosis without affecting systemic immunity.

New synergistic combination therapy approaches with HDAC inhibitor quisinostat, cisplatin or PARP inhibitor talazoparib for urothelial carcinoma.

Urothelial carcinoma (UC) urgently requires new therapeutic options. Histone deacetylases (HDAC) are frequently dysregulated in UC and constitute interesting targets for the development of alternative therapy options. Thus, we investigated the effect of the second generation HDAC inhibitor (HDACi) quisinostat in five UC cell lines (UCC) and two normal control cell lines in comparison to romidepsin, a well characterized HDACi which was previously shown to induce cell death and cell cycle arrest. In UCC, quisinostat led to cell cycle alterations, cell death induction and DNA damage, but was well tolerated by normal cells. Combinations of quisinostat with cisplatin or the PARP inhibitor talazoparib led to decrease in cell viability and significant synergistic effect in five UCCs and platinum-resistant sublines allowing dose reduction. Further analyses in UM-UC-3 and J82 at low dose ratio revealed that the mechanisms included cell cycle disturbance, apoptosis induction and DNA damage. These combinations appeared to be well tolerated in normal cells. In conclusion, our results suggest new promising combination regimes for treatment of UC, also in the cisplatin-resistant setting.

Batimastat Induces Cytotoxic and Cytostatic Effects in In Vitro Models of Hematological Tumors.

The role of metalloproteinases (MMPs) in hematological malignancies, like acute myeloid leukemia (AML), myelodysplastic neoplasms (MDS), and multiple myeloma (MM), is well-documented, and these pathologies remain with poor outcomes despite treatment advancements. In this study, we investigated the effects of batimastat (BB-94), an MMP inhibitor (MMPi), in single-administration and daily administration schemes in AML, MDS, and MM cell lines. We used four hematologic neoplasia cell lines: the HL-60 and NB-4 cells as AML models, the F36-P cells as an MDS model, and the H929 cells as a model of MM. We also tested batimastat toxicity in a normal human lymphocyte cell line (IMC cells). BB-94 decreases cell viability and density in a dose-, time-, administration-scheme-, and cell-line-dependent manner, with the AML cells displaying higher responses. The efficacy in inducing apoptosis and cell cycle arrests is dependent on the cell line (higher effects in AML cells), especially with lower daily doses, which may mitigate treatment toxicity. Furthermore, BB-94 activated apoptosis via caspases and ERK1/2 pathways. These findings highlight batimastat's therapeutic potential in hematological malignancies, with daily dosing emerging as a strategy to minimize adverse effects.

Pharmacological blockade of HDAC6 attenuates cancer progression by inhibiting IL-1ß and modulating immunosuppressive response in OSCC.

Interleukin-1-beta (IL-1ß) one of the biomarkers for oral squamous cell carcinoma (OSCC), is upregulated in tumor-microenvironment (TME) and associated with poor patient survival. Thus, a novel modulator of IL-1ß would be of great therapeutic value for OSCC treatment. Here we report regulation of IL-1ß and TME by histone deacetylase-6 (HDAC6)-inhibitor in OSCC. We observed significant upregulation of HDAC6 in 4-nitroquniline (4-NQO)-induced OSCC in mice and 4-NQO & Lipopolysaccharide (LPS) stimulated OSCC and fibroblast cells. Tubastatin A (TSA)-attenuated the OSCC progression in mice as observed improvement in the histology over tongue and esophagus, with reduced tumor burden. TSA treatment to 4-NQO mice attenuated protein expression of HDAC6, pro-and-mature-IL-1ß and pro-and-cleaved-caspase-1 and ameliorated acetylated-tubulin. In support of our experimental work, human TCGA analysis revealed HDAC6 and IL-1ß were upregulated in the primary tumor, with different tumor stages and grades. We found TSA modulate TME, indicated by downregulation of CD11b+Gr1+-Myeloid-derived suppressor cells, CD11b+F4/80+CD206+ M2-macrophages and increase in CD11b+F4/80+MHCII+ M1-macrophages. TSA significantly reduced the gene expression of HDAC6, IL-1ß, Arginase-1 and iNOS in isolated splenic-MDSCs. FaDu-HTB-43 and NIH3T3 cells stimulated with LPS and 4-NQO exhibit higher IL-1ß levels in the supernatant. Interestingly, immunoblot analysis of the cell lysate, we observed that TSA does not alter the expression as well as activation of IL-1ß and caspase-1 but the acetylated-tubulin was found to be increased. Nocodazole pre-treatment proved that TSA inhibited the lysosomal exocytosis of IL-1ß through tubulin acetylation. In conclusion, HDAC6 inhibitors attenuated TME and cancer progression through the regulation of IL-1ß in OSCC.

Phase II trial of domatinostat (4SC-202) in combination with avelumab in patients with previously treated advanced mismatch repair proficient oesophagogastric and colorectal adenocarcinoma: EMERGE.

BACKGROUND: Most oesophagogastric adenocarcinomas (OGAs) and colorectal cancers (CRCs) are mismatch repair proficient (MMRp), responding poorly to immune checkpoint inhibition. We evaluated the safety and efficacy of domatinostat (histone deacetylase inhibitor) plus avelumab (anti-PD-L1 antibody) in patients with previously treated inoperable, advanced/metastatic MMRp OGA and CRC. PATIENTS AND METHODS: Eligible patients were evaluated in a multicentre, open-label dose escalation/dose expansion phase II trial. In the escalation phase, patients received escalating doses of domatinostat [100 mg once daily (OD), 200 mg OD, 200 mg twice daily (BD)] orally for 14 days followed by continuous dosing plus avelumab 10 mg/kg administered intravenously 2-weekly (2qw) to determine the recommended phase II dose (RP2D). The trial expansion phase evaluated the best objective response rate (ORR) during 6 months by RECIST version 1.1 using a Simon two-stage optimal design with 2/9 and 1/10 responses required to proceed to stage 2 in the OGA and CRC cohorts, respectively. RESULTS: Patients (n = 40) were registered between February 2019 and October 2021. Patients in the dose escalation phase (n = 12) were evaluated to confirm the RP2D of domatinostat 200 mg BD plus avelumab 10 mg/kg. No dose-limiting toxicities were observed. Twenty-one patients were treated at the RP2D, 19 (9 OGA and 10 CRC) were assessable for the best ORR; 2 patients with CRC did not receive combination treatment and were not assessable for the primary endpoint analysis. Six patients were evaluated in the dose escalation and expansion phases. In the OGA cohort, the best ORR was 22.2% (95% one-sided confidence interval lower bound 4.1) and the median duration of disease control was 11.3 months (range 9.9-12.7 months). No responses were observed in the CRC cohort. No treatment-related grade 3-4 adverse events were reported at the RP2D. CONCLUSIONS: Responses in the OGA cohort met the criteria to expand to stage 2 of recruitment with an acceptable safety profile. There was insufficient signal in the CRC cohort to progress to stage 2. TRIAL REGISTRATION: NCT03812796 (registered 23rd January 2019).

Dual-Epigenetically Relieving the MYC-Correlated Immunosuppression via an Advanced Nano-Radiosensitizer Potentiates Cancer Immuno-Radiotherapy.

Cancer cells can upregulate the MYC expression to repair the radiotherapy-triggered DNA damage, aggravating therapeutic resistance and tumor immunosuppression. Epigenetic treatment targeting the MYC-transcriptional abnormality may intensively solve this clinical problem. Herein, 5-Aza (a DNA methyltransferase inhibitor) and ITF-2357 (a histone deacetylase inhibitor) are engineered into a tungsten-based nano-radiosensitizer (PWAI), to suppress MYC rising and awaken robust radiotherapeutic antitumor immunity. Individual 5-Aza depletes MYC expression but cannot efficiently awaken radiotherapeutic immunity. This drawback can be overcome by the addition of ITF-2357, which triggers cancer cellular type I interferon (IFN-I) signaling. Coupling 5-Aza with ITF-2357 ensures that PWAI does not evoke the treated model with high MYC-related immune resistance while amplifying the radiotherapeutic tumor killing, and more importantly promotes the generation of IFN-I signal-related proteins involving IFN-α and IFN-ß. Unlike the radiation treatment alone, PWAI-triggered immuno-radiotherapy remarkably enhances antitumor immune responses involving the tumor antigen presentation by dendritic cells, and improves intratumoral recruitment of cytotoxic T lymphocytes and their memory-phenotype formation in 4T1 tumor-bearing mice. Downgrading the radiotherapy-induced MYC overexpression via the dual-epigenetic reprogramming strategy may elicit a robust immuno-radiotherapy.

Dual inhibition of CYP17A1 and HDAC6 by abiraterone-installed hydroxamic acid overcomes temozolomide resistance in glioblastoma through inducing DNA damage and oxidative stress.

Glioblastoma (GBM) is a highly aggressive and treatment-resistant brain tumor, necessitating novel therapeutic strategies. In this study, we present a mechanistic breakthrough by designing and evaluating a series of abiraterone-installed hydroxamic acids as potential dual inhibitors of CYP17A1 and HDAC6 for GBM treatment. We established the correlation of CYP17A1/HDAC6 overexpression with tumor recurrence and temozolomide resistance in GBM patients. Compound 12, a dual inhibitor, demonstrated significant anti-GBM activity in vitro, particularly against TMZ-resistant cell lines. Mechanistically, compound 12 induced apoptosis, suppressed recurrence-associated genes, induced oxidative stress and initiated DNA damage response. Furthermore, molecular modeling studies confirmed its potent inhibitory activity against CYP17A1 and HDAC6. In vivo studies revealed that compound 12 effectively suppressed tumor growth in xenograft and orthotopic mouse models without inducing significant adverse effects. These findings highlight the potential of dual CYP17A1 and HDAC6 inhibition as a promising strategy for overcoming treatment resistance in GBM and offer new hope for improved therapeutic outcomes.

Activity of alkoxyamide-based histone deacetylase inhibitors against Plasmodium falciparum malaria parasites.

There are more than 240 million cases of malaria and 600,000 associated deaths each year, most due to infection with Plasmodium falciparum parasites. While malaria treatment options exist, new drugs with novel modes of action are needed to address malaria parasite drug resistance. Protein lysine deacetylases (termed HDACs) are important epigenetic regulatory enzymes and prospective therapeutic targets for malaria. Here we report the antiplasmodial activity of a panel of 17 hydroxamate zinc binding group HDAC inhibitors with alkoxyamide linkers and different cap groups. The two most potent compounds (4a and 4b) were found to inhibit asexual P. falciparum growth with 50% inhibition concentrations (IC50's) of 0.07 µM and 0.09 µM, respectively, and demonstrated >200-fold more selectivity for P. falciparum parasites versus human neonatal foreskin fibroblasts (NFF). In situ hyperacetylation studies demonstrated that 4a, 4b and analogs caused P. falciparum histone H4 hyperacetylation, suggesting HDAC inhibition, with structure activity relationships providing information relevant to the design of new Plasmodium-specific aliphatic chain hydroxamate HDAC inhibitors.

Recent developments of hydroxamic acid hybrids as potential anti-breast cancer agents.

Histone deacetylase inhibitors not only possess favorable effects on modulating tumor microenvironment and host immune cells but also can reactivate the genes silenced due to deacetylation and chromatin condensation. Hydroxamic acid hybrids as promising histone deacetylase inhibitors have the potential to address drug resistance and reduce severe side effects associated with a single drug molecule due to their capacity to simultaneously modulate multiple targets in cancer cells. Accordingly, rational design of hydroxamic acid hybrids may provide valuable therapeutic interventions for the treatment of breast cancer. This review aimed to provide insights into the in vitro and in vivo anti-breast cancer therapeutic potential of hydroxamic acid hybrids, together with their mechanisms of action and structure-activity relationships, covering articles published from 2020 to the present.

Quisinostat is a brain-penetrant radiosensitizer in glioblastoma.

Histone deacetylase (HDAC) inhibitors have garnered considerable interest for the treatment of adult and pediatric malignant brain tumors. However, owing to their broad-spectrum nature and inability to effectively penetrate the blood-brain barrier, HDAC inhibitors have failed to provide substantial clinical benefit to patients with glioblastoma (GBM) to date. Moreover, global inhibition of HDACs results in widespread toxicity, highlighting the need for selective isoform targeting. Although no isoform-specific HDAC inhibitors are currently available, the second-generation hydroxamic acid-based HDAC inhibitor quisinostat possesses subnanomolar specificity for class I HDAC isoforms, particularly HDAC1 and HDAC2. It has been shown that HDAC1 is the essential HDAC in GBM. This study analyzed the neuropharmacokinetic, pharmacodynamic, and radiation-sensitizing properties of quisinostat in preclinical models of GBM. It was found that quisinostat is a well-tolerated and brain-penetrant molecule that extended survival when administered in combination with radiation in vivo. The pharmacokinetic-pharmacodynamic-efficacy relationship was established by correlating free drug concentrations and evidence of target modulation in the brain with survival benefit. Together, these data provide a strong rationale for clinical development of quisinostat as a radiosensitizer for the treatment of GBM.

Synergistic effect of docetaxel combined with a novel multi-target inhibitor CUDC-101 on inhibiting human prostate cancer.

Histone deacetylases (HDACs) are commonly overexpressed in several types of human cancers, including prostate cancer (PCa). Histone deacetylase inhibitors (HDACis) are emerging as promising tools for cancer therapy. However, there is still a need to understand their anti-tumor effects and the mechanisms underlying their action. In our study, we investigated the effects of co-treatment with CUDC-101 and docetaxel (DTX) on cell growth, clonogenicity, invasion and migration of PCa cells both in vitro, and in a xenograft mouse model. We found that the combination of CUDC-101 and DTX significantly reduced tumor growth, as evidenced by lower tumor weight and volumes. Moreover, apoptotic cell death was increased in the combination group compared to either drug alone or control. Mechanistically, we observed that the combined treatment of CUDC-101 with DTX suppressed the progression of PCa cell lines through the AKT and ERK1/2 signaling pathways. Additionally, this combination treatment reversed EMT by modulating the expression of key markers such as E-cadherin, vimentin, Snail and MMP-9. To conclude, these results demonstrated that the combination of CUDC-101 with DTX had a synergistic and significantly improved anti-carcinogenic effect. This combination may serve as a potential strategy for clinical treatment and prognosis improvement in PCa.

Hydroxamate-based compounds are potent inhibitors of Toxoplasma gondii HDAC biological activity.

Toxoplasmosis is a critical health issue for immune-deficient individuals and the offspring of newly infected mothers. It is caused by a unicellular intracellular parasite called Toxoplasma gondii that is found worldwide. Although efficient drugs are commonly used to treat toxoplasmosis, serious adverse events are common. Therefore, new compounds with potent anti-T. gondii activity are needed to provide better suited treatments. We have tested compounds designed to target specifically histone deacetylase enzymes. Among the 55 compounds tested, we identified three compounds showing a concentration of drug required for 50% inhibition (IC50) in the low 100 nM range with a selectivity index of more than 100. These compounds are not only active at inhibiting the growth of the parasite in vitro but also at preventing some of the consequences of the acute disease in vivo. Two of these hydroxamate based compound also induce a hyper-acetylation of the parasite histones while the parasitic acetylated tubulin level remains unchanged. These findings suggest that the enzymes regulating histone acetylation are potent therapeutic targets for the treatment of acute toxoplasmosis.

Histone Deacetylase Inhibitor (SAHA) Reduces Mortality in an Endotoxemia Mouse Model by Suppressing Glycolysis.

Sepsis is a life-threatening medical emergency triggered by excessive inflammation in response to an infection. High mortality rates and limited therapeutic options pose significant challenges in sepsis treatment. Histone deacetylase inhibitors (HDACi), such as suberoylanilide hydroxamic acid (SAHA), have been proposed as potent anti-inflammatory agents for treating inflammatory diseases. However, the underlying mechanisms of sepsis treatment remain poorly understood. In this study, we investigated the effects of SAHA treatment in the lipopolysaccharide (LPS)-induced endotoxemia mouse model as it closely mimics the early stages of the systemic inflammation of sepsis. Our results demonstrate a reduced inflammatory mediator secretion and improved survival rates in mice. Using quantitative acetylomics, we found that SAHA administration increases the acetylation of lactate dehydrogenase (LDHA), and consequently inhibits LDHA activity. Notably, the reduced enzyme activity of LDHA results in a reduced rate of glycolysis. Furthermore, our experiments with bone marrow-derived macrophages (BMDMs) show that SAHA administration reduced oxidative stress and extracellular ATP concentrations, ultimately blunting inflammasome activation. Overall, our study provides insights into the mechanism underlying SAHA's therapeutic effects in sepsis treatment and highlights LDHA as a potential target for developing novel sepsis treatment.

Anticancer clinical efficiency and stochastic mechanisms of belinostat.

Cancer progression is strongly affected by epigenetic events in addition to genetic modifications. One of the key elements in the epigenetic control of gene expression is histone modification through acetylation, which is regulated by the synergy between histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs are thought to offer considerable potential for the development of anticancer medications, particularly when used in conjunction with other anticancer medications and/or radiotherapy. Belinostat (Beleodaq, PXD101) is a pan-HDAC unsaturated hydroxamate inhibitor with a sulfonamide group that has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of refractory or relapsed peripheral T-cell lymphoma (PTCL) and solid malignancies or and other hematological tissues. This drug modifies histones and epigenetic pathways. Because HDAC and HAT imbalance can lead to downregulation of regulatory genes, resulting in tumorigenesis. Inhibition of HDACs by belinostat indirectly promotes anti-cancer therapeutic effect by provoking acetylated histone accumulation, re-establishing normal gene expressions in cancer cells and stimulating other routes such as the immune response, p27 signaling cascades, caspase 3 activation, nuclear protein poly (ADP-ribose) polymerase-1 (PARP-1) degradation, cyclin A (G2/M phase), cyclin E1 (G1/S phase) and other events. In addition, belinostat has already been discovered to increase p21WAF1 in a number of cell lines (melanoma, prostate, breast, lung, colon, and ovary). This cyclin-dependent kinase inhibitor actually has a role in processes that cause cell cycle arrest and apoptosis. Belinostat's clinical effectiveness, comprising Phase I and II studies within the areas of solid and hematological cancers, has been evidenced through several investigative trials that have supported its potential to be a valuable anti-cancer drug. The purpose of this research was to provide insight on the specific molecular processes through which belinostat inhibits HDAC. The ability to investigate new therapeutic options employing targeted therapy and acquire a deeper understanding of cancer cell abnormalities may result from a better understanding of these particular routes.

HDAC inhibition regulates oxidative stress in CD4+Thelper cells of chronic obstructive pulmonary disease and non-small cell lung cancer patients via mitochondrial transcription factor a (mtTFA) modulating NF-κB/HIF1α axis.

Histone deacetylases (HDACs) play a crucial role in the epigenetic regulation of gene expression by remodelling chromatin. Isoenzymes of the HDAC family exhibit aberrant regulation in a wide variety of cancers as well as several inflammatory lung disorders like chronic obstructive pulmonary disease (COPD). Inhibition of HDACs is a potential therapeutic strategy that could be used to reverse epigenetic modification. Trichostatin A (TSA), a powerful histone deacetylase (HDAC) inhibitor, has anti-cancer effects in numerous cancer types. However, it is not yet apparent how HDAC inhibitors affect human non-small cell lung cancer cells (NSCLC) and COPD. This study aims to investigate TSA's role in restoring mitochondrial dysfunction and its effect on hypoxia and inflammation in CD4+T cells obtained from patients with COPD and lung cancer. As a result of treatment with TSA, there is a reduction in the expression of inflammatory cytokines and a decreased enrichment of transcriptional factors associated with inflammation at VEGFA gene loci. We have seen a substantial decrease in the expression of NF-κB and HIF1α, which are the critical mediators of inflammation and hypoxia, respectively. Following TSA treatment, mtTFA expression was increased, facilitating patients with COPD and NSCLC in the recovery of their dysfunctional mitochondria. Furthermore, we have discovered that TSA treatment in patients with COPD and NSCLC may lead to immunoprotective ness by inducing Th1ness. Our finding gives a new insight into the existing body of knowledge regarding TSA-based therapeutic methods and highlights the necessity of epigenetic therapy for these devastating lung disorders.

Signaling Network Response to α-Particle-Targeted Therapy with the 225Ac-Labeled Minigastrin Analog 225Ac-PP-F11N Reveals the Radiosensitizing Potential of Histone Deacetylase Inhibitors.

α-particle emitters have recently been explored as valuable therapeutic radionuclides. Yet, toxicity to healthy organs and cancer radioresistance limit the efficacy of targeted α-particle therapy (TAT). Identification of the radiation-activated mechanisms that drive cancer cell survival provides opportunities to develop new points for therapeutic interference to improve the efficacy and safety of TAT. Methods: Quantitative phosphoproteomics and matching proteomics followed by the bioinformatics analysis were used to identify alterations in the signaling networks in response to TAT with the 225Ac-labeled minigastrin analog 225Ac-PP-F11N (DOTA-(dGlu)6-Ala-Tyr-Gly-Trp-Nle-Asp-Phe) in A431 cells, which overexpress cholecystokinin B receptor (CCKBR). Western blot analysis and microscopy verified the activation of the selected signaling pathways. Small-molecule inhibitors were used to validate the potential of the radiosensitizing combinatory treatments both in vitro and in A431/CCKBR tumor-bearing nude mice. Results: TAT-induced alterations were involved in DNA damage response, cell cycle regulation, and signal transduction, as well as RNA transcription and processing, cell morphology, and transport. Western blot analysis and microscopy confirmed increased phosphorylations of the key proteins involved in DNA damage response and carcinogenesis, including p53, p53 binding protein 1 (p53BP1), histone deacetylases (HDACs), and H2AX. Inhibition of HDAC class II, ataxia-telangiectasia mutated (ATM), and p38 kinases by TMP269, AZD1390, and SB202190, respectively, sensitized A431/CCKBR cells to 225Ac-PP-F11N. As compared with the control and monotherapies, the combination of 225Ac-PP-F11N with the HDAC inhibitor vorinostat (suberoylanilide hydroxamic acid, SAHA) significantly reduced the viability and increased the DNA damage of A431/CCKBR cells, led to the most pronounced tumor growth inhibition, and extended the mean survival of A431/CCKBR xenografted nude mice. Conclusion: Our study revealed the cellular responses to TAT and demonstrated the radiosensitizing potential of HDAC inhibitors to 225Ac-PP-F11N in CCKBR-positive tumors. This proof-of-concept study recommends development of novel radiosensitizing strategies by targeting TAT-activated and survival-promoting signaling pathways.

Rationally designed donepezil-based hydroxamates modulate Sig-1R and HDAC isoforms to exert anti-glioblastoma effects.

The pursuit of activating the HDAC inhibitory template towards additional mechanisms spurred us to design dual modulators (Sig-1R agonist - HDAC inhibitor) via utilization of the core structural unit of donepezil (an FDA-approved anti-Alzheimer's agent) as a surface recognition part. Literature precedents coupled with our experience rendered us with several insights that led to the inclusion of chemically diverse linkers and hydroxamic acid (zinc-binding motif) as the other components of HDAC inhibitory pharmacophore. With this envisionment and clarity, donepezil-based HDAC inhibitory adducts were furnished and exhaustively explored for their anti-GBM efficacy. Resultantly, a magnificently potent HDAC inhibitor 10 [IC50 (HDAC6) = 2.7 nM, IC50 (HDAC2) = 0.71 µM] was pinpointed that was endowed with the ability to: i) exert cell growth inhibitory effects against Human U87MG GBM cells ii) cause death in TMZ-resistant GBM cells iii) induce subG1 arrest in GBM cells iv) prolong the survival of TMZ-resistant U87MG inoculated orthotopic mice (in-vivo studies) v) induce GBM cell apoptosis via binding to Sig-1R. Collectively, the results led to the identification of compound 10 as a tractable anti-GBM agent that deserves detailed investigation for the accomplishment of its candidature as a GBM therapeutic.

Network-based assessment of HDAC6 activity predicts preclinical and clinical responses to the HDAC6 inhibitor ricolinostat in breast cancer.

Inhibiting individual histone deacetylase (HDAC) is emerging as well-tolerated anticancer strategy compared with pan-HDAC inhibitors. Through preclinical studies, we demonstrated that the sensitivity to the leading HDAC6 inhibitor (HDAC6i) ricolinstat can be predicted by a computational network-based algorithm (HDAC6 score). Analysis of ~3,000 human breast cancers (BCs) showed that ~30% of them could benefice from HDAC6i therapy. Thus, we designed a phase 1b dose-escalation clinical trial to evaluate the activity of ricolinostat plus nab-paclitaxel in patients with metastatic BC (MBC) (NCT02632071). Study results showed that the two agents can be safely combined, that clinical activity is identified in patients with HR+/HER2- disease and that the HDAC6 score has potential as predictive biomarker. Analysis of other tumor types also identified multiple cohorts with predicted sensitivity to HDAC6i's. Mechanistically, we have linked the anticancer activity of HDAC6i's to their ability to induce c-Myc hyperacetylation (ac-K148) promoting its proteasome-mediated degradation in sensitive cancer cells.