A novel halogenated adenosine analog 5'-BrDA displays potent toxicity against colon cancer cells in vivo and in vitro

Molecular Insights into Converting Hydroxide Adenosyltransferase into Halogenase

Halogenation plays a unique role in the design of agrochemicals. Enzymatic halogenation reactions have attracted great attention due to their excellent specificity and mild reaction conditions. S-adenosyl-l-methionine (SAM)-dependent halogenases mediate the nucleophilic attack of halide ions (X-) to SAM to produce 5'-XDA. However, only 11 SAM-dependent fluorinases and 3 chlorinases have been reported, highlighting the desire for additional halogenases. SAM-dependent hydroxide adenosyltransferase (HATase) has a similar reaction mechanism as halogenases but uses water as a substrate instead of halide ions. Here, we explored a HATase from the thermophile Thermotoga maritima MSB8 and transformed it into a halogenase. We identified a key dyad W8L/V71T for the halogenation reaction. We also obtained the best performing mutants for each halogenation reaction: M1, M2 and M4 for Cl-, Br- and I-, respectively. The M4 mutant retained the thermostability of HATase in the iodination reaction at 80 °C, which surpasses the natural halogenase SalL. QM/MM revealed that these mutants bind halide ions with more suitable angles for nucleophilic attack of C5' of SAM, thus conferring halogenation capabilities. Our work achieved the halide ion specificity of halogenases and generated thermostable halogenases for the first time, which provides new opportunities to expand the halogenase repertoire from hydroxylase.

Synthesis and Selective Anticancer Activity Evaluation of 2-phenylacrylonitrile Derivatives as Tubulin Inhibitors

OBJECTIVE

This study aimed at synthesizing 13 series of novel derivatives with 2-phenylacrylonitrile, evaluating antitumor activity both in vivo and in vitro, and obtaining novel tubulin inhibitors.

METHOD

The 13 series of 2-phenylacrylonitrile derivatives were synthesized by Knoevenagel condensation and the anti-proliferative activities were determined by MTT assay. The cell cycle and apoptosis were analyzed by flow cytometer. Quantitative cell migration was performed using 24-well Boyden chambers. The proteins were detected by western blotting. in vitro kinetics of microtubule assembly was measured using ELISA kit for Human β-tubulin (TUBB). Molecular docking was done by Discovery Studio (DS) 2017 Client online tool.

RESULTS

Among the derivatives, compound 1g2a possessed strong inhibitory activity against HCT116 (IC50 = 5.9 nM) and BEL-7402 (IC50 = 7.8 nM) cells. Compound 1g2a exhibited better selective antiproliferative activities and specificities than all the positive control drugs, including taxol. Compound 1g2a inhibited proliferation of HCT116 and BEL-7402 cells by arresting them in the G2/M phase of the cell cycle, inhibited the migration of HCT116 and BEL-7402 cells and the formation of cell colonies. Compound 1g2a showed excellent tubulin polymerization inhibitory activity on HCT116 and BEL-7402 cells. The results of molecular docking analyses showed that 1g2a may inhibit tubulin to exert anticancer effects.

CONCLUSION

Compound 1g2a shows outstanding antitumor activity both in vivo and in vitro and has the potential to be further developed into a highly effective antitumor agent with little toxicity to normal tissues.

A natural halogenated fluoride adenosine analog 5'-fluorodeoxy adenosine induced anticolon cancer activity in vivo and in vitro

Adenosine (ADO) and its analogs have been introduced into the anticancer clinical trials, especial for the ADO derivatives with fluoride. The biosynthesis of fluorinase produces a fluorine-containing ADO analog 5'-fluorodeoxy adenosine (5'-FDA). The toxicity and application of 5'-FDA has not been evaluated, which limits the application of ADO analogs. In order to study its potential mechanism, we carried out the following experiments. In our research, 5'-FDA displayed good antitumor activity in colon cancer cells and two colon cancer models. As a result, 5'-FDA concentration-dependently inhibited the proliferation, migration, and invasion in colon cancer cells through its proapoptosis and cell cycle arrest pathway. Furthermore, 5'-FDA inhibited the growth of colon cancer and its pulmonary metastasis in CT26 inbred mice without affecting their body weight. It was found that 5'-FDA remarkably increased the protein levels of Caspase 3 and cleaved-Caspase 9 and decreased Cyclin A2 and CDK2 via the regulation of p53 signaling pathway, and increased the protein levels of Caspase 8 and cleaved-Caspase 8 which participated in apoptosis pathway. All in all, 5'-FDA displayed excellent therapeutic effects on colon cancer and its pulmonary metastasis. We believed that our study provided a theoretical basis for further preclinical research of 5'-FDA in the treatment of cancer.