DCTPP1, a reliable Q-biomarker for comprehensive evaluation of the quality of tripterygium glycoside tablets based on chemical references.

BACKGROUND: As first-line clinical drugs, tripterygium glycoside tablets (TGTs) often have inconsistent efficacy and toxic side effects, mainly due to inadequate quality control. Therefore, clinically relevant quality standards for TGTs are urgently required. PURPOSE: Based on chemical substances and considering pharmacological efficacy, we aimed to develop an effective quality evaluation method for TGTs. METHODS: Representative commercial samples of TGTs were collected from different manufacturers, and qualitative UHPLC/LTQ-Orbitrap-MS and quantitative UHPLC-MS/MS analysis methods were successfully applied to evaluate their quality similarities and differences based on their chemical properties. Then the anti-immunity, anti-inflammatory and antitumor activities of TGTs and related monomers were evaluated using Jurkat, RAW264.7, MIA PaCa-2, and PANC-1 as cellular models. Subsequently, we predicted and verified small molecule-DCTPP1 interactions via molecular docking using the established DCTPP1 enzymatic activity assay. Finally, we performed a gray relational analysis to evaluate the chemical characteristics and biological effects of TGTs produced by different manufacturers. RESULTS: We collected 24 batches of TGTs (D01-D24) from 5 manufacturers (Co. A, Co. B, Co. C, Co. D, Co. E) for quality evaluation. The chemical composition analysis revealed significant differences in the substance bases of the samples. The D02, D18-D20 samples from Co. B constituted a separate group that differed from other samples, mainly in their absence of diterpenoids and triterpenoids, including triptolide, triptophenolide, and triptonide. In vitro anti-immunity, antitumor and anti-inflammatory tests using the same TGT concentration revealed that, except for D02, D18-D20, the remaining 20 samples exhibited different degrees of anti-immunity, antitumor and anti-inflammatory activity. Our experiments verified that triptolide, triptophenolide, and triptonide were all DCTPP1 inhibitors, and that TGTs generally exhibited DCTPP1 enzyme inhibitory activity. Moreover, the inhibitory activity of D02, D18-D20 samples from Co. B was much lower than that of the other samples, with a nearly tenfold difference in IC50. Further comprehensive analysis revealed a high correlation between DCTPP1 enzyme inhibition activity and the anti-immunity and antitumor and anti-inflammatory activities of these samples. CONCLUSION: The established DCTPP1 enzymatic activity assay proved suitable for quantitative pharmacological and pharmaceutical analysis to complement the existing quality control system for TGTs and to evaluate their effectiveness.

Mechanistic investigations of hirsutene biosynthesis catalyzed by a chimeric sesquiterpene synthase from Steccherinum ochraceum.

The high efficiency and elegance of terpene synthases is fascinating in constructing the molecular skeleton of complicated terpenoids with multiple chiral centers. Although the rapid development of sequencing technology has led to the discovery of an increasing number of terpene synthases, the cyclization mechanisms of some terpene synthases remains elusive. Here, we report that a chimeric sesquiterpene synthase from Steccherinum ochraceum is responsible for the biosynthesis of (+)-hirsutene, a linear triquinane sesquiterpene. Structural validation, and isotope labeling experiments demonstrate that the biosynthesis of (+)-hirsutene employs an unusual cyclization mode, involving three different cyclization processes (C1-C11, C2-C9, C3-C6), one intramolecular 1,2-hydride shift (C9-C10) and three successive 1,2-alkyl shifts to construct the 5-5-5 fused ring skeleton of (+)-hirsutene.

Triptolide: reflections on two decades of research and prospects for the future.

Covering: 2000 to 2020 Triptolide is a bioactive diterpene triepoxide isolated from Tripterygium wilfordii Hook F, a traditional Chinese medicinal plant whose extracts have been used as anti-inflammatory and immunosuppressive remedies for centuries. Although triptolide and its analogs exhibit potent bioactivities against various cancers, and inflammatory and autoimmune diseases, none of them has been approved to be used in the clinic. This review highlights advances in material sourcing, molecular mechanisms, clinical progress and new drug design strategies for triptolide over the past two decades, along with some prospects for the future course of development of triptolide.

A Glucose-Triptolide Conjugate Selectively Targets Cancer Cells under Hypoxia.

A major hurdle in the treatment of cancer is chemoresistance induced under hypoxia that is characteristic of tumor microenvironment. Triptolide, a potent inhibitor of eukaryotic transcription, possesses potent antitumor activity. However, its clinical potential has been limited by toxicity and water solubility. To address those limitations of triptolide, we designed and synthesized glucose-triptolide conjugates (glutriptolides) and demonstrated their antitumor activity in vitro and in vivo. Herein, we identified a lead, glutriptolide-2 with an altered linker structure. Glutriptolide-2 possessed improved stability in human serum, greater selectivity toward cancer over normal cells, and increased potency against cancer cells. Glutriptolide-2 exhibits sustained antitumor activity, prolonging survival in a prostate cancer metastasis animal model. Importantly, we found that glutriptolide-2 was more potent against cancer cells under hypoxia than normoxia. Together, this work provides an attractive glutriptolide drug lead and suggests a viable strategy to overcome chemoresistance through conjugation of cytotoxic agents to glucose.

LncRNA TTN-AS1 promotes the progression of oral squamous cell carcinoma via miR-411-3p/NFAT5 axis.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a common kind of squamous cell carcinoma of the head and neck, which is a threat to public health. Long noncoding RNAs (lncRNAs) are associated with the development of various diseases, including cancers. LncRNA titin antisense RNA 1 (TTN-AS1) is known as a crucial regulatory factor in several cancers. Nevertheless, the specific functions of TTN-AS1 in OSCC remains obscure. METHODS: The expression of TTN-AS1 in OSCC samples or cells was analyzed through qRT-PCR. Colony formation assay, EdU assay, flow cytometry assay, TUNEL assay and wound healing assay were conducted to estimate the functions of TTN-AS1 in OSCC cells. RIP and luciferase reporter assays were utilized to detect the interaction between TTN-AS1 and miR-411-3p as well as between miR-411-3p and NFAT5. RESULTS: TTN-AS1 expression was stronger in OSCC cells. Knockdown of TTN-AS1 effectively restrained cell proliferation and migration but had inductive role in apoptosis. Moreover, TTN-AS1 could function as the miR-411-3p sponge in OSCC and miR-411-3p exerted the inhibitory functions on OSCC cell growth. In addition, NFAT5 was proven as the target of miR-411-3p. Rescue assay indicated that overexpressing NFAT5 could reverse the inhibitory function of TTN-AS1 depletion on cell growth. CONCLUSION: lncRNA TTN-AS1 contributed to the progression of OSCC via miR-411-3p/NFAT5 axis.

Targeted Delivery and Sustained Antitumor Activity of Triptolide through Glucose Conjugation.

Triptolide, a key ingredient from the traditional Chinese medicinal plant thunder god vine, which has been used to treat inflammation and autoimmune diseases for centuries, has been shown to be an irreversible inhibitor of the XPB subunit of the transcription factor TFIIH and initiation of RNA polymerase II mediated transcription. The clinical development of triptolide over the past two decades has been limited by its toxicity and low water solubility. Herein, we report the development of a glucose conjugate of triptolide, named glutriptolide, which was intended to target tumor cells overexpressing glucose transporters selectively. Glutriptolide did not inhibit XPB activity in vitro but demonstrated significantly higher cytotoxicity against tumor cells over normal cells with greater water solubility than triptolide. Furthermore, it exhibited remarkable tumor control in vivo, which is likely due to sustained stepwise release of active triptolide within cancer cells. These findings indicate that glutriptolide may serve as a promising lead for developing a new mechanistic class of anticancer drugs.

Covalent modification of a cysteine residue in the XPB subunit of the general transcription factor TFIIH through single epoxide cleavage of the transcription inhibitor triptolide.

Triptolide is a key component of the traditional Chinese medicinal plant Thunder God Vine and has potent anticancer and immunosuppressive activities. It is an irreversible inhibitor of eukaryotic transcription through covalent modification of XPB, a subunit of the general transcription factor TFIIH. Cys342 of XPB was identified as the residue that undergoes covalent modification by the 12,13-epoxide group of triptolide. Mutation of Cys342 of XPB to threonine conferred resistance to triptolide on the mutant protein. Replacement of the endogenous wild-type XPB with the Cys342Thr mutant in a HEK293T cell line rendered it completely resistant to triptolide, thus validating XPB as the physiologically relevant target of triptolide. Together, these results deepen our understanding of the interaction between triptolide and XPB and have implications for the future development of new analogues of triptolide as leads for anticancer and immunosuppressive drugs.

Self-resistance to an antitumor antibiotic: a DNA glycosylase triggers the base-excision repair system in yatakemycin biosynthesis.

Resistance is (not) futile: The yatakemycin biosynthetic gene cluster involves the ytkR2 gene, which encodes a protein with homology to a recently discovered bacterial DNA glycosylase. Genetic validation in vivo, biochemical assays, and in vitro mutagenesis studies revealed that YtkR2 confers resistance for the bacteria by specifically recognizing and cleaving the YTM-modified base (see scheme).

Characterization of yatakemycin gene cluster revealing a radical S-adenosylmethionine dependent methyltransferase and highlighting spirocyclopropane biosynthesis.

Yatakemycin (YTM), an antitumor natural product, represents the most potent member of a class of potent anticancer natural products including CC-1065 and duocarmycins. Herein we describe the biosynthetic gene cluster of YTM, which was identified by genome scanning of Streptomyces sp. TP-A0356. This cluster consists of 31 open reading frames (ORFs) and was localized to a 36 kb DNA segment. Moreover, its involvement in YTM biosynthesis was confirmed by cluster deletion, gene replacement, and complementation. Inactivation of ytkT, which encodes a radical S-adenosylmethionine (SAM) protein, created a mutant strain that failed to produce YTM but accumulated a new metabolite, which was structurally elucidated as a precursor that was related to the formation of the cyclopropane ring. More importantly, biochemical characterization of the radical SAM-dependent enzyme YtkT revealed that it is a novel C-methyltransferase and contributes to an advanced intermediate during formation of the cyclopropane ring through a radical mechanism in the YTM biosynthetic pathway. On the basis of in silico analysis, genetic experiments, structure elucidation of the novel intermediate, and biochemical characterization, a biosynthetic pathway for yatakemycin was proposed, which sets the stage to further investigate the novel enzymatic mechanisms and engineer the biosynthetic machinery for the production of novel analogues.

XPB, a subunit of TFIIH, is a target of the natural product triptolide.

Triptolide (1) is a structurally unique diterpene triepoxide isolated from a traditional Chinese medicinal plant with anti-inflammatory, immunosuppressive, contraceptive and antitumor activities. Its molecular mechanism of action, however, has remained largely elusive to date. We report that triptolide covalently binds to human XPB (also known as ERCC3), a subunit of the transcription factor TFIIH, and inhibits its DNA-dependent ATPase activity, which leads to the inhibition of RNA polymerase II-mediated transcription and likely nucleotide excision repair. The identification of XPB as the target of triptolide accounts for the majority of the known biological activities of triptolide. These findings also suggest that triptolide can serve as a new molecular probe for studying transcription and, potentially, as a new type of anticancer agent through inhibition of the ATPase activity of XPB.