Analyzing and engineering of the biosynthetic pathway of mollemycin A for enhancing its production.

Mollemycin A (MOMA) is a unique glyco-hexadepsipeptide-polyketide that was isolated from a Streptomyces sp. derived from the Australian marine environment. MOMA exhibits remarkable inhibitory activity against both drug-sensitive and multidrug-resistant malaria parasites. Optimizing MOMA through structural modifications or product enhancements is necessary for the development of effective analogues. However, modifying MOMA using chemical approaches is challenging, and the production titer of MOMA in the wild-type strain is low. This study identified and characterized the biosynthetic gene cluster of MOMA for the first time, proposed its complex biosynthetic pathway, and achieved an effective two-pronged enhancement of MOMA production. The fermentation medium was optimized to increase the yield of MOMA from 0.9 mg L-1 to 1.3 mg L-1, a 44% boost. Additionally, a synergistic mutant strain was developed by deleting the momB3 gene and overexpressing momB2, resulting in a 2.6-fold increase from 1.3 mg L-1 to 3.4 mg L-1. These findings pave the way for investigating the biosynthetic mechanism of MOMA, creating opportunities to produce a wide range of MOMA analogues, and developing an efficient strain for the sustainable and economical production of MOMA and its analogues.

An unusual aromatase/cyclase programs the formation of the phenyldimethylanthrone framework in anthrabenzoxocinones and fasamycin.

Aromatic polyketides are renowned for their wide-ranging pharmaceutical activities. Their structural diversity is mainly produced via modification of limited types of basic frameworks. In this study, we characterized the biosynthesis of a unique basic aromatic framework, phenyldimethylanthrone (PDA) found in (+)/(-)-anthrabenzoxocinones (ABXs) and fasamycin (FAS). Its biosynthesis employs a methyltransferase (Abx(+)M/Abx(-)M/FasT) and an unusual TcmI-like aromatase/cyclase (ARO/CYC, Abx(+)D/Abx(-)D/FasL) as well as a nonessential helper ARO/CYC (Abx(+)C/Abx(-)C/FasD) to catalyze the aromatization/cyclization of polyketide chain, leading to the formation of all four aromatic rings of the PDA framework, including the C9 to C14 ring and a rare angular benzene ring. Biochemical and structural analysis of Abx(+)D reveals a unique loop region, giving rise to its distinct acyl carrier protein-dependent specificity compared to other conventional TcmI-type ARO/CYCs, all of which impose on free molecules. Mutagenic analysis discloses critical residues of Abx(+)D for its catalytic activity and indicates that the size and shape of its interior pocket determine the orientation of aromatization/cyclization. This study unveils the tetracyclic and non-TcmN type C9 to C14 ARO/CYC, significantly expanding our cognition of ARO/CYCs and the biosynthesis of aromatic polyketide framework.

Macro CD5L+ deteriorates CD8+T cells exhaustion and impairs combination of Gemcitabine-Oxaliplatin-Lenvatinib-anti-PD1 therapy in intrahepatic cholangiocarcinoma.

Intratumoral immune status influences tumor therapeutic response, but it remains largely unclear how the status determines therapies for patients with intrahepatic cholangiocarcinoma. Here, we examine the single-cell transcriptional and TCR profiles of 18 tumor tissues pre- and post- therapy of gemcitabine plus oxaliplatin, in combination with lenvatinib and anti-PD1 antibody for intrahepatic cholangiocarcinoma. We find that high CD8 GZMB+ and CD8 proliferating proportions and a low Macro CD5L+ proportion predict good response to the therapy. In patients with a poor response, the CD8 GZMB+ and CD8 proliferating proportions are increased, but the CD8 GZMK+ proportion is decreased after the therapy. Transition of CD8 proliferating and CD8 GZMB+ to CD8 GZMK+ facilitates good response to the therapy, while Macro CD5L+-CD8 GZMB+ crosstalk impairs the response by increasing CTLA4 in CD8 GZMB+. Anti-CTLA4 antibody reverses resistance of the therapy in intrahepatic cholangiocarcinoma. Our data provide a resource for predicting response of the combination therapy and highlight the importance of CD8+T-cell status conversion and exhaustion induced by Macro CD5L+ in influencing the response, suggesting future avenues for cancer treatment optimization.

Comparison of intraluminal brachytherapy combined with and without stent placement for treatment of obstructive jaundice induced by tumor thrombus.

PURPOSE: To compare the safety and efficacy of intraluminal brachytherapy with iodine-125 (125I) seed strand implantation combined with and without stent placement to treat patients with obstructive jaundice induced by tumor thrombus. METHODS: Between January 2018 and June 2022, 42 patients with malignant obstructive jaundice (MOJ) induced by tumor thrombus were included. 20 patients received 125I seed strand implantation and stent placement (group A). The remaining 22 patients, implanted 125I seed strands only, served as control (group B). The two groups' overall survival and jaundice-free survival were compared using the Kaplan-Meier method and log-rank test. RESULTS: During the follow-up period, the mean survival time of group A was 38.0 ± 4.1 months (95%CI, 30.0-46.1 months), while that of group B was 25.1 ± 2.8 (95% CI, 19.5-30.6 months) (p = 0.406). The mean survival rates of 12 months for all patients, group A, and group B was 66.7%, 65%, and 68%, respectively. The mean jaundice-free survival of group A and group B were 34.0 ± 3.6 months (95% CI, 27.9-41.2months) and 22.9 ± 2.7 months (95%CI, 17.5-28.2months) (p = 0.254), respectively. Two PTBD drainage tube infection cases occurred in group A and group B separately. CONCLUSIONS: 125I intraluminal brachytherapy is an effective and safe therapy for treating patients with obstructive jaundice induced by tumor thrombus.

A large conserved family of small-molecule carboxyl methyltransferases identified from microorganisms.

Small-molecule carboxyl methyltransferases (CbMTs) constitute a small proportion of the reported methyltransferases, but they have received extensive attention due to their important physiological functions. Most of the small-molecule CbMTs isolated to date originate from plants and are members of the SABATH family. In this study, we identified a type of CbMT (OPCMT) from a group of Mycobacteria, which has a distinct catalytic mechanism from the SABATH methyltransferases. The enzyme contains a large hydrophobic substrate-binding pocket (~400 Å3) and utilizes two conserved residues, Thr20 and Try194, to retain the substrate in a favorable orientation for catalytic transmethylation. The OPCMT_like MTs have a broad substrate scope and can accept diverse carboxylic acids enabling efficient production of methyl esters. They are widely (more than 10,000) distributed in microorganisms, including several well-known pathogens, whereas no related genes are found in humans. In vivo experiments implied that the OPCMT_like MTs was indispensable for M. neoaurum, suggesting that these proteins have important physiological functions.

Formation and Loading of a (2S)-2-Ethylmalonamyl Starter Unit in the Assembly Line of Polyketide-Nonribosomal Peptide Hybrid Sanglifehrin A.

Sanglifehrin A (SFA) is a spirolactam-conjugated, 22-membered macrolide with remarkable immunosuppressive and antiviral activities. This macrolide is a result of a hybrid polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS) assembly line that utilizes (2S)-2-ethylmalonamyl as a starter unit. Here, we report that the formation and loading of this starter unit in the SFA assembly line involve two unusual enzymatic reactions that occur on a discrete acyl carrier protein (ACP), SfaO. An amide synthetase, SfaP, catalyzes the amidation of (2S)-2-ethylmalonyl in a SfaO-dependent manner. Then, a ß-ketoacyl-ACP synthase III-like protein, SfaN, transfers resultant (2S)-2-ethylmalonamyl from SfaO onto the loading ACP domain of the hybrid PKS-NRPS assembly line to prime SFA biosynthesis. Both SfaP and SfaN display promiscuous activities. This study furthers the appreciation of assembly line chemistry, as a new paradigm for unusual building block formation and incorporation is provided.

Engineering the Substrate Specificity of a P450 Dimerase Enables the Collective Biosynthesis of Heterodimeric Tryptophan-Containing Diketopiperazines.

Heterodimeric tryptophan-containing diketopiperazines (HTDKPs) are an important class of bioactive secondary metabolites. Biosynthesis offers a practical opportunity to access their bioactive structural diversity, however, it is restricted by the limited substrate scopes of the HTDKPs-forming P450 dimerases. Herein, by genome mining and investigation of the sequence-product relationships, we unveiled three important residues (F387, F388 and E73) in these P450s that are pivotal for selecting different diketopiperazine (DKP) substrates in the upper binding pocket. Engineering these residues in NasF5053 significantly expanded its substrate specificity and enabled the collective biosynthesis, including 12 self-dimerized and at least 81 cross-dimerized HTDKPs. Structural and molecular dynamics analysis of F387G and E73S revealed that they control the substrate specificity via reducing steric hindrance and regulating substrate tunnels, respectively.

Biosynthesis of Tetronates by a Nonribosomal Peptide Synthetase-Polyketide Synthase System.

A cryptic tetronate biosynthetic pathway was identified in Kitasatospora niigatensis DSM 44781 via heterologous expression. Distinct from the currently known biosynthetic pathways, this system utilizes a partially functional nonribosomal peptide synthetase and a broadly selective polyketide synthase to direct the assembly and lactonization of the tetronate scaffold. By employing a permissive crotonyl-CoA reductase/carboxylase to provide different extender units, seven new tetronates (kitaniitetronins A-G) were obtained via precursor-directed biosynthesis.

Hepatectomy After Conversion Therapy Using Tyrosine Kinase Inhibitors Plus Anti-PD-1 Antibody Therapy for Patients with Unresectable Hepatocellular Carcinoma.

BACKGROUND: Combined treatment with tyrosine kinase inhibitors (TKI) plus anti-PD-1 antibodies showed high anti-tumor efficacy and made conversion resection possible for patients with unresectable hepatocellular carcinoma (HCC). However, long-term survival has not been reported. METHODS: A cohort of consecutive patients who received combined TKI/anti-PD-1 antibodies as first-line treatment for initially unresectable HCC at the authors' hospital between August 2018 and September 2020 was eligible for this study. Patients who were responding to systemic therapy and met the criteria for hepatectomy underwent liver resection with curative intention. The study also investigated the association of clinical factors with successful conversion resection and postoperative recurrence. RESULTS: The study enrolled 101 patients including 24 patients (23.8 %) who underwent R0 resection a median of 3.9 months (interquartile range: 2.5-5.9 months) after initiation of systemic therapy. Patients with an Eastern cooperative oncology group performance status of 0, fewer intrahepatic tumors, or a radiographic response to systemic therapy were more likely to be able to receive curative resection. After a median follow-up period of 21.5 months, hepatectomy was independently associated with a favorable overall survival (hazard ratio [HR], 0.050; 95 % confidence interval [CI], 0.007-0.365; P = 0.003). For the 24 patients who underwent surgery, the 12-month recurrence-free survival and overall survival rates were respectively 75% and 95.8%. Achieving a pathologic complete response (n = 10) to systemic therapy was associated with a favorable recurrence-free survival after resection, with a trend toward significance (HR, 0.345; 95% CI, 0.067-1.785; P = 0.187). CONCLUSIONS: Selected patients with initially unresectable HCC can undergo hepatectomy after systemic therapy with combined TKI/anti-PD-1 antibodies. In this study, conversion resection was associated with a favorable prognosis.

Sublethal heat treatment enhances lactic acid uptake in macrophages via MCT1, leading to reduced paraspeckle formation and a subsequent decrease in macrophage pyroptosis.

Introduction: Heat ablation is one of the key modalities in treating liver cancer, yet the residual cancer tissues suffering sublethal heat treatment possess a potential for increased malignancy. This study conducts a comprehensive analysis of cellular dynamics, metabolic shifts, and macrophage polarization within the tumor microenvironment following sublethal heat treatment. Methods: We observed significant acidification in tumor cell supernatants, attributed to increased lactic acid production. The study focused on how this pH shift, crucial in tumor progression and resistance, influences macrophage polarization, especially towards the M2 phenotype known for tumor-promoting functions. We also examined the upregulation of MCT1 expression post sublethal heat treatment and its primary role in lactic acid transport. Results: Notably, the study found minimal disparity in MCT1 expression between hepatocellular carcinoma patients and healthy liver tissues, highlighting the complexity of cancer biology. The research further revealed an intricate relationship between lactic acid, MCT1, and the inhibition of macrophage pyroptosis, offering significant insights for therapeutic strategies targeting the tumor immune environment. Post sublethal heat treatment, a reduction in paraspeckle under lactic acid exposure was observed, indicating diverse cellular impacts. Additionally, PKM2 was identified as a key molecule in this context, with decreased levels after sublethal heat treatment in the presence of lactic acid. Discussion: Collectively, these findings illuminate the intertwined mechanisms of sublethal heat treatments, metabolic alterations, and immune modulation in the tumor milieu, providing a deeper understanding of the complex interplay in cancer biology and treatment.

Conversion therapy for initially unresectable hepatocellular carcinoma using a combination of toripalimab, lenvatinib plus TACE: real-world study.

BACKGROUND: Combination conversion therapies afforded curative surgery chance for initially unresectable hepatocellular carcinoma (uHCC). This study aimed to evaluate the conversion rate and clinical outcomes of a first-line conversion regimen of lenvatinib combined with transarterial chemoembolization (TACE) plus immunotherapy for initial uHCC by interpreting real-world data. METHODS: Conversion therapy data of patients with uHCC from November 2018 to January 2021 were analysed. The regimens included triple combination therapy (t-CT: lenvatinib, TACE, plus toripalimab) and dual combination therapy (d-CT: lenvatinib plus TACE). Another study population diagnosed with hepatocellular carcinoma of macrovascular invasion disease were included as the upfront surgery cohort. Treatment responses and conversion rate were primary outcomes. Survival and adverse events were analysed. RESULTS: Fifty-one patients receiving t-CT (n = 30) and d-CT (n = 21) were enrolled. Higher overall response rates (76.7 per cent versus 47.6 per cent, P = 0.042) and disease control rates (90.0 per cent versus 57.1 per cent, P = 0.042) were observed via t-CT than d-CT. Both median overall survival and event-free survival were not reached in the t-CT cohort. A higher rate of curative conversion resection was achieved through t-CT than d-CT (50.0 per cent versus 19.0 per cent, P = 0.039). The disease-free survival of patients undergoing conversion resection in the t-CT cohort (n = 15) was higher than that in the upfront surgery cohort (n = 68, P = 0.039). Both t-CT and d-CT regimens were tolerable. CONCLUSIONS: Better treatment responses and conversion rate for patients with uHCC were obtained with first-line t-CT. Neoadjuvant t-CT before surgery should be recommended for patients with macrovascular invasion.

An Atypical Acyl-CoA Synthetase Enables Efficient Biosynthesis of Extender Units for Engineering a Polyketide Carbon Scaffold.

Acyl-CoAs are key precursors of primary and secondary metabolism. Their efficient biosynthesis is often impeded by the limited substrate specificity and low in vivo activity of acyl-CoA synthetases (ACSs) due to regulatory acylation of the catalytically important lysine residue in motif A10 (Lys-A10). In this study, we identified an unusual ACS (UkaQ) from the UK-2A biosynthetic pathway that naturally lacks the Lys-A10 residue and exhibits extraordinarily broad substrate specificity. Protein engineering significantly improved its stability and catalytic activity, enabling it to synthesize a large variety of acyl-CoAs with highly robust activity. By combining it with permissive carboxylases, we produced a large array of polyketide extender units and obtained six novel halobenzyl-containing antimycin analogues through an engineered biosynthetic pathway. This study significantly expands the catalytic mode of ACSs and provides a potent tool for the biosynthesis of acyl-CoA-derived natural products.

Norditerpenoids biosynthesized by variediene synthase-associated P450 machinery along with modifications by the host cell Aspergillus oryzae.

The chemical diversity of terpenoids is typically established by terpene synthase-catalyzed cyclization and diversified by post-tailoring modifications. Fungal bifunctional terpene synthase (BFTS) associated P450 enzymes have shown significant catalytic potentials through the development of various new terpenoids with different biological activities. This study discovered the BFTS and its related gene cluster from the plant endophytic fungus Didymosphaeria variabile 17020. Heterologous expression of the BFTS in Saccharomyces cerevisiae resulted in the characterization of a major product diterpene variediene (1), along with two new minor products neovariediene and neoflexibilene. Further heterologous expression of the BFTS and one cytochrome P450 enzyme VndE (CYP6138B1) in Aspergillus oryzae NSAR1 led to the identification of seven norditerpenoids (19 carbons) with a structurally unique 5/5 bicyclic ring system. Interestingly, in vivo experiments suggested that the cyclized terpene variediene (1) was modified by VndE along with the endogenous enzymes from the host cell A. oryzae through serial chemical conversions, followed by multi-site hydroxylation via A. oryzae endogenous enzymes. Our work revealed that the two-enzymes biosynthetic system and host cell machinery could produce structurally unique terpenoids.

Transcatheter arterial embolization-salvaged ALPPS, a novel ALPPS procedure especially for patients with hepatocellular carcinoma and severe fibrosis/cirrhosis.

Background: The associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) for hepatocellular carcinoma (HCC) with fibrosis/cirrhosis is often associated with limited growth of future liver remnant (FLR). We introduced a new procedure named transcatheter arterial embolization-salvaged ALPPS (TAE-salvaged ALPPS) which was shown to be especially suitable for HCC patients with cirrhosis or fibrosis who failed adequately to respond to conventional ALPPS. The short-term efficacy and safety for the TAE-salvaged ALPPS on patients with HCC and fibrosis/cirrhosis were studied. Methods: Consecutive HCC patients who underwent TAE-salvaged ALPPS in our hospital between November 2016 and June 2020 were retrospectively studied. The new ALPPS procedure included conventional ALPPS stage-1 using associating liver partition and portal vein ligation. When FLR failed to reach sufficient hypertrophy, TAE was carried out 2 weeks later followed by liver resection 3 weeks after ALPPS stage-1. Results: Nine of 10 patients had a single tumor (median diameter 14.0 cm, range, 5.2-17 cm). The remaining patient had multiple tumors (diameter of one tumor 14.0 cm, and two satellite foci 2.0 and 3.0 cm). R0 resection was achieved in all patients (100%) after a median of 21 days. Six patients had cirrhosis, 1 had METAVIR grade-3 fibrosis, and 3 had METAVIR grade-2 fibrosis. The median increase in FLR volume after TAE-salvaged ALPPS was 69.7% (34.4-143.9%). The absolute and relative kinetic growth rates (KGRs) were 9.9 (7.1-17.3) mL/day and 3.4% (1.9-7.2%)/day, respectively. The median absolute KGRs were 15.7, 2.6, and 19.5 mL/day in the first, second, and third postoperative weeks after ALPPS stage-1, respectively. The rapid increase in KGR on the third week was induced by TAE. The overall postoperative morbidity rates were 50,0% (5/10), 20.0% (2/10) and 70.0% (7/10) after ALPPS stage-1, TAE and ALPPS stage-2, respectively. The 90-day mortality rate was 10.0% (1/10). The median overall survival was 40 months. Conclusions: The new TAE-salvaged ALPPS induced significant increases in FLR volumes within 3 weeks in patients with HCC and fibrosis/cirrhosis. The procedure is promising in treating patients with HCC and fibrosis/cirrhosis who fail to achieve sufficient FLR hypertrophy after conventional ALPPS stage-1.

Biosynthesis of pyrroloindoline-containing natural products.

Covering: up to 2022Pyrroloindoline is a privileged tricyclic indoline motif widely present in many biologically active and medicinally valuable natural products. Thus, understanding the biosynthesis of this molecule is critical for developing convenient synthetic routes, which is highly challenging for its chemical synthesis due to the presence of rich chiral centers in this molecule, especially the fully substituted chiral carbon center at the C3-position of its rigid tricyclic structure. In recent years, progress has been made in elucidating the biosynthetic pathways and enzymatic mechanisms of pyrroloindoline-containing natural products (PiNPs). This article reviews the main advances in the past few decades based on the different substitutions on the C3 position of PiNPs, especially the various key enzymatic mechanisms involved in the biosynthesis of different types of PiNPs.

Expanding the Chemical Diversity of Fasamycin Via Genome Mining and Biocatalysis.

Genome mining and biocatalytic modification of chemical structures are critical methods to develop new antibiotics. In this study, eight new fasamycins (3, 4, 6, and 8-12) along with five known analogues (1, 2, 5, 7, and 13) were obtained by the overexpression of two phosphopantetheinyl transferases (PPtases) in Streptomyces kanamyceticus and biocatalytic transformation with two halogenases. These new compounds displayed significant activity against Staphylococcus aureus and Bacillus subtilis, in particular, C-29-methyl and C-2/C-22-halogen derivatives. This study increases the chemical diversity of bioactive fasamycin derivatives and provides useful halogenation tools for engineering their scaffolds.

A Pair of Atypical KAS III Homologues with Initiation and Elongation Functions Program the Polyketide Biosynthesis in Asukamycin.

ß-Ketoacyl-ACP synthase III (KAS III) is a class of important C-C bond-forming enzymes that mostly catalyze the initiation of polyketide and fatty acid biosynthesis. In this study, we elucidated an unusual polyketide synthase (PKS) system that involves two unique KAS IIIs (AsuC3 and C4) in the biosynthesis of the upper triene chain of asukamycin. Significantly, AsuC3 and C4 have both initiation and iterative elongation activity, while being functionally biased toward the elongation and initiation steps, respectively. Mutational analysis revealed that their catalytic activities rely on the catalytic triad Cys-His-Asn. Unlike other KAS IIIs, AsuC3 and C4 are very promiscuous and can accept various lengths of acyl-CoAs with either cyclic, branched or linear acyl moieties. By cooperation with the permissive ketoreductase (AsuC7) and dehydratase (AsuC8/C9), a large variety of polyenes can be efficiently synthesized. This study significantly broadens the understanding of KAS IIIs and polyketide biosynthesis.