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Histone deacetylase 6 (HDAC6) has emerged as a critical regulator of many cellular pathways in tumors due to its unique structure basis and abundant substrate types. Over the past few decades, the role played by HDAC6 inhibitors as anticancer agents has sparked great interest of biochemists worldwide. However, they were less reported for gastric cancer therapy. In this paper, with the help of bioisosteric replacement, in-house library screening, and lead optimization strategies, we designed, synthesized and verified a series of 1,3-diaryl-1,2,4-triazole-capped HDAC6 inhibitors with promising anti-gastric cancer activities. Amongst, compound 9r displayed the best inhibitory activity towards HDAC6 (IC 50  = 30.6 nM), with 128-fold selectivity over HDAC1. Further BLI and CETSA assay proved the high affinity of 9r to HDAC6. In addition, 9r could dose-dependently upregulate the levels of acetylated α-tubulin, without significant effect on acetylated histone H3 in MGC803 cells. Besides, 9r exhibited potent antiproliferative effect on MGC803 cells, and promoted apoptosis and suppressed the metastasis without obvious toxicity, suggesting 9r would serve as a potential lead compound for the development of novel therapeutic agents of gastric cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Tumor immunotherapy is currently subject of intense scientific and clinical developments. In previous decade, therapists used natural immune system from the human body to treat several diseases. Although tumor immune disease is a big challenge, combinatorial therapeutic strategy has been succeeded to show the clinical significance. In this context, we discuss the HDAC6 and tumor immune diseases relationship. Also, we summarized the current state of knowledge that based on the combination treatments of the HDAC6 inhibitors (HDAC6is) with antitumor immunomodulatory agents. We observed that, the combination therapies slow down the tumor immune diseases by blocking the aggresome and proteasome pathway. The combination therapy was able to reduce M2 macrophage and increasing PD-L1 blockade sensitivity. Most importantly, multiple combinations of HDAC6is with other agents may consider as potential strategies to treat tumor immune diseases, by reducing the side effects and improve efficacy for the future clinical development., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Gramine is a natural indole alkaloid with a wide range of biological activities, but its anti-gastric cancer activity is poor. Herein, a pharmacophore fusion strategy was adopted to design and synthesize a new series of indole-azole hybrids on the structural basis of gramine. Based on our previous studies, different nitrogen-containing five-membered heterocyclic rings and terminal alkyne group were introduced into the indole-based scaffold to investigate their effect on improving the anti-gastric cancer activity of gramine derivatives. Structure-activity relationship (SAR) studies highlighted the role played by terminal alkyne in enhancing the inhibitory effect, and compound 16h displayed the best antiproliferative activity against gastric cancer MGC803 cells with IC 50 value of 3.74 μM. Further investigations displayed compound 16h could induce mitochondria-mediated apoptosis, and caused cell cycle arrest at G2/M phase. Besides, compound 16h could inhibit the metastasis ability of MGC803 cells. Our studies may provide a new strategy for structural optimization of gramine to enhance anti-gastric cancer activity, and provide a potential candidate for the treatment of gastric cancer., (Copyright © 2020. Published by Elsevier Inc.)

To discover novel anticancer agents with potent and low toxicity, we designed and synthesized a range of new thiosemicarbazone-indole analogues based on lead compound 4 we reported previously. Most compounds displayed moderate to high anticancer activities against five tested tumor cells (PC3, EC109, DU-145, MGC803, MCF-7). Specifically, the represented compound 16f possessed strong antiproliferative potency and high selectivity toward PC3 cells with the IC 50 value of 0.054 μM, compared with normal WPMY-1 cells with the IC 50 value of 19.470 μM. Preliminary mechanism research indicated that compound 16f could significantly suppress prostate cancer cells (PC3, DU-145) growth and colony formation in a dose-dependent manner. Besides, derivative 16f induced G1/S cycle arrest and apoptosis, which may be related to ROS accumulation due to the activation of MAPK signaling pathway. Furthermore, molecule 16f could effectively inhibit tumor growth through a xenograft model bearing PC3 cells and had no evident toxicity in vivo. Overall, based on the biological activity evaluation, analogue 16f can be viewed as a potential lead compound for further development of novel anti-prostate cancer drug., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

In this paper, a series of thiosemicarbazone derivatives containing different aromatic heterocyclic groups were synthesized and the tridentate donor system of the lead compound was optimized. Most of the target compounds showed improved antiproliferative activity against MGC803 cells. SAR studies revealed that compound 5d displayed significant advantages in inhibition effect with an IC 50 value of 0.031 μM, and better selectivity between cancer and normal cells than 3-AP and DpC (about 15- and 5-fold improved respectively). Besides, compound 5d showed selective antiproliferative activity in not only other cancer cells but also different gastric cancer cell lines. In-depth mechanism studies showed that compound 5d could induce mitochondria-related apoptosis which might be related to the elevation of intracellular ROS level, and cause cell cycle arrest at S phase. Moreover, 5d could evidently suppress the cell migration and invasion by blocking the EMT (epithelial-mesenchymal transition) process. Consequently, our studies provided a lead optimization strategy of thiosemicarbazone derivatives which would contribute to discover high-efficiency and low-toxicity agents for the treatment of gastric cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Lysine specific demethylase 1 (LSD1) plays an essential role in maintaining a balanced methylation status at histone tails. Overexpression of LSD1 has been involved in the development of a variety of human diseases, including cancers. Herein, on the basis of our previously developed LSD1 inhibitors, two series of new [1,2,3]triazolo[4,5-d]pyrimidine derivatives incorporating (thio)urea moiety were designed and evaluated for their LSD1 inhibitory abilities, leading to a novel chemical class of LSD1 inhibitors. Among them, compound 31 was found to moderately inhibit LSD1 activity, as well as increase the expression of H3K4me2 at the cellular level. This compound also showed good selectivity against MAO-A/-B, and a panel of kinases such as CDK and BTK. Besides, the MTT assay suggested that the selected compounds could inhibit the proliferation of LSD1-overexpressed cancer cells. Although this class of compounds only showed moderate anti-LSD1 activity in the micromolar range, this work presents a novel chemotype of LSD1 inhibitors with good enzyme selectivity as well as cellular LSD1 inhibitory activity, and could provide a useful template for the development of more potent LSD1 inhibitors for cancer treatment., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

To explore anti-gastric cancer agents with high efficacy and selectivity, we report the design, synthesis and optimization of a novel series of 3-(2,6,9-trisubstituted-9H-purine)-8-chalcone derivatives starting from the compound PCA-15 reported by us previously. Most of the target compounds demonstrated significant antiproliferative effects on MGC803 cancer cell line, and more potent than the positive control (PCA-15 and 5-Fu). Among them, compound 6o was identified to be the most active compound against MGC803 cell line with an IC 50 value of 0.84 μM. Additionally, high selectivity was also observed between cancer and normal cells (23.35 μM against GES-1). Further mechanism studies confirmed that compound 6o could inhibit colony formation and migration, induce the apoptosis of MGC803 cells through both the mitochondrial-mediated intrinsic pathway and death receptor-mediated extrinsic pathway, which were evidenced by the up-regulation of Bax, cleaved-caspase 9/3/8, cleaved PARP and down-regulation of Bcl-2. Our systematic studies implied a new scaffold targeting gastric cancer cells for further development of small-molecule compounds with improved potency and selectivity., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

A new series of 6-chloro-2-(propylthio)-8,9-dihydro-7H-purine-8-caboxamide derivatives were designed, synthesized, and further evaluated for their antiproliferative activities on four human cancer cell lines (A549, MGC803, PC-3 and TE-1). The structure-activity relationships (SARs) studies were conducted through the variation in the two regions, which including position 8 and 9, of purine core. One of the compounds, 8, containing a terminal piperazine appendage with a carboxamide moiety at position 8 and phenyl group at position 9 of 6-chloro-8,9-dihydro-7H-purine core, showed the most potent antiproliferative activity and good selectivity between cancer and normal cells (IC 50 values of 2.80 μM against A549 and 303.03 μM against GES-1, respectively). In addition, compound 8 could inhibit the colony formation and migration of A549 cells in a concentration-dependent manner, as well as induce the apoptosis possibly through the intrinsic pathway., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

ABCB1-mediated multidrug resistance (MDR) is a principal obstacle for successful cancer chemotherapy. A series of pyrimidine-based hybrid molecules containing 1,2,3-triazole moiety were evaluated for their reversal activities against MDR. The majority of target compounds displayed moderate to great reversal potency. Among these compounds, compound 25 displayed the most potent reversal activity, about 7-fold more potent than Verapamil (VRP). Further mechanism studies revealed that compound 25 could obviously reverse paclitaxel (PTX) resistance in SW620/AD300 cells by increasing accumulation and extending maintenance of PTX. Our findings indicate that the 1,2,3-triazole-pyrimidine-based derivatives may serve as an interesting lead for the development of new potent and efficacious ABCB1-dependent MDR modulators., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

A series of thiazolo[5,4-d]pyrimidine derivatives were designed through the atom replacement strategy based on biologically validated scaffolds and then evaluated for their antiproliferative activities on cancer cell lines. The structure-activity relationship studies were conducted, leading to the identification of compound 22, which exhibited good antiproliferative activity against HGC-27 with an IC 50 value of 1.22 μM and low toxicity against GES-1 cells. Mechanistic studies showed that compound 22 inhibited the colony formation and migration of HGC-27 as well as induced apoptosis. The western blot experiments proved that compound 22 up-regulated expression of Bax, down-regulated expression levels of Bcl-2 and cleaved caspased-3/9. These findings indicate that compound 22 may serve as a template for designing new agents for the treatment of human gastric cancers. The atom replacement strategy could be viable strategy for designing new anticancer drugs and may find its applications in drug design., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Histone lysine specific demethylase 1 (LSD1) plays an important role in epigenetic modifications, and aberrant expression of LSD1 predicts tumor progression and poor prognosis in human esophageal cancers. In this study, a series of LSD1 inhibitors were synthesized and proved to be highly potent against human esophageal squamous cell carcinoma (ESCC). Our data showed that these LSD1 inhibitors selectively suppressed the viability of esophageal cancer cell line (EC-109) bearing overexpressed LSD1. Among these, compound LPE-1 (LSD1 IC 50 =0.336±0.003μM) significantly suppressed proliferation, induced apoptosis, arrested cell cycle of EC109 cells at G2/M phase, and caused changes of the associated protein markers correspondingly. We also found that compound LPE-1 potently inhibited the migration and invasion of EC-109 cells. Docking studies showed that the cyano group formed hydrogen bonds with Val811 and Thr810. Additionally, the thiophene moiety formed arene-H interaction with Trp761 residue. In vivo studies showed that compound LPE-1 inhibited tumor growth of xenograft models bearing EC-109 without obvious toxicity. Collectively, our findings indicate that LSD1 may be a potential therapeutic target in ESCC, and compound LPE-1 could serve as a lead compound for further development for anti-ESCC drug discovery., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A series of [1,2,3]triazolo[4,5-d]pyrimidine derivatives bearing a hydrazone moiety were designed, synthesized and evaluated for their antiproliferative activity against several cancer cell lines of different origins by MTT assay. Most of the synthesized compounds demonstrated moderate to good activity against the cancer cell lines selected. Especially, compound 43 showed the most potent antiproliferative activity as well as good selectivity between cancer and normal cells (IC 50 values of 0.85 μM against MGC-803 and 56.17 μM against GES-1). In addition, compound 43 evidently inhibited the colony formation of MGC-803 cells at 0.8 μM. Further mechanism studies revealed that compound 43 could induce apoptosis of MGC-803 cells probably through the mitochondrial pathway accompanied with decrease of the mitochondrial membrane potential (MMP), activations of caspase-9/3, up-regulation of the expression of Bax, Bak and PUMA, as well as down-regulation of that of Bcl-2 and Mcl-1., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)