The biosynthetic logic and enzymatic machinery of approved fungi-derived pharmaceuticals and agricultural biopesticides

Covering: 2000 to 2023The kingdom Fungi has become a remarkably valuable source of structurally complex natural products (NPs) with diverse bioactivities. Since the revolutionary discovery and application of the antibiotic penicillin from Penicillium, a number of fungi-derived NPs have been developed and approved into pharmaceuticals and pesticide agents using traditional "activity-guided" approaches. Although emerging genome mining algorithms and surrogate expression hosts have brought revolutionary approaches to NP discovery, the time and costs involved in developing these into new drugs can still be prohibitively high. Therefore, it is essential to maximize the utility of existing drugs by rational design and systematic production of new chemical structures based on these drugs by synthetic biology. To this purpose, there have been great advances in characterizing the diversified biosynthetic gene clusters associated with the well-known drugs and in understanding the biosynthesis logic mechanisms and enzymatic transformation processes involved in their production. We describe advances made in the heterogeneous reconstruction of complex NP scaffolds using fungal polyketide synthases (PKSs), non-ribosomal peptide synthetases (NRPSs), PKS/NRPS hybrids, terpenoids, and indole alkaloids and also discuss mechanistic insights into metabolic engineering, pathway reprogramming, and cell factory development. Moreover, we suggest pathways for expanding access to the fungal chemical repertoire by biosynthesis of representative family members via common platform intermediates and through the rational manipulation of natural biosynthetic machineries for drug discovery.

Somalactams A-D: Anti-inflammatory Macrolide Lactams with Unique Ring Systems from an Arctic Actinomycete Strain

Four new PKS-NRPS-derived macrolide lactams with three unique ring fusion types were discovered from the Arctic sponge associated actinomycete Streptomyces somaliensis 1107 using a genome mining strategy. Their structures were elucidated by a combination of MS, NMR spectroscopic analysis, and single-crystal X-ray diffraction. Biosynthetically, a novel gene cluster sml consisting of three polyketide synthases and one hybrid polyketide synthase-nonribosomal peptide synthetase together with cytochrome P450s and flavin-containing monooxygenases and oxidoreductases was demonstrated to assemble the unique skeleton. Pharmacological studies revealed that compound 1 displayed a potent anti-inflammatory effect without cytotoxicity. It inhibited IL-6 and TNF-α release in the serum of LPS-stimulated RAW264.7 macrophage cells with IC₅₀ values of 5.76 and 0.18 μM, respectively, and modulated the MAPK pathway. Moreover, compound 1 alleviated LPS-induced systemic inflammation in our transgenic fluorescent zebrafish model.

Biosynthesis of Chuangxinmycin Featuring a Deubiquitinase-like Sulfurtransferase

The knowledge on sulfur incorporation mechanism involved in sulfur-containing molecule biosynthesis remains limited. Chuangxinmycin is a sulfur-containing antibiotic with a unique thiopyrano[4,3,2-cd]indole (TPI) skeleton and selective inhibitory activity against bacterial tryptophanyl-tRNA synthetase. Despite the previously reported biosynthetic gene clusters and the recent functional characterization of a P450 enzyme responsible for C-S bond formation, the enzymatic mechanism for sulfur incorporation remains unknown. Here, we resolve this central biosynthetic problem by in vitro biochemical characterization of the key enzymes and reconstitute the TPI skeleton in a one-pot enzymatic reaction. We reveal that the JAMM/MPN⁺ protein Cxm3 functions as a deubiquitinase-like sulfurtransferase to catalyze a non-classical sulfur-transfer reaction by interacting with the ubiquitin-like sulfur carrier protein Cxm4GG. This finding adds a new mechanism for sulfurtransferase in nature.

Polyene-Producing Streptomyces spp. From the Fungus-Growing Termite Macrotermes barneyi Exhibit High Inhibitory Activity Against the Antagonistic Fungus Xylaria

Fungus-growing termites are engaged in a tripartite mutualism with intestinal microbes and a monocultivar (Termitomyces sp.) in the fungus garden. The termites are often plagued by entomopathogen (Metarhizium anisopliae) and fungus garden is always threatened by competitors (Xylaria spp.). Here, we aim to understand the defensive role of intestinal microbes, the actinomycetes which were isolated from the gut of Macrotermes barneyi. We obtained 44 antifungal isolates, which showed moderate to strong inhibition to Xylaria sp. HPLC analysis indicated that different types of polyenes (tetraene, pentene, and heptaene) existed in the metabolites of 10 strong antifungal Streptomyces strains. Two pentene macrolides (pentamycin and 1′14-dihydroxyisochainin) were firstly purified from Streptomyces strain HF10, both exhibiting higher activity against Xylaria sp. and M. anisopliae than cultivar Termitomyces. Subsequently, tetraene and heptaene related gene disruption assay showed that the mutant strains lost the ability to produce corresponding polyenes, and they also had significantly decreased activities against Xylaria sp. and M. anisopliae compared to that of wild type strains. These results indicate that polyene-producing Streptomyces from the guts of M. barneyi have strong inhibition to competitor fungus and polyenes contribute to inhibitory effects on Xylaria sp.

Abstract P3-01-18: In vivo isolation of circulating tumour cells using CellCollector and detection of gene mutations in different metastasis organ sites in breast cancer

Introduction: Metastasis is thought to result from tumour cell entry into the circulation and migration to distant organs, where the mutation landscape of metastatic breast cancer (MBC) may shift and vary. The genotypic features of circulating tumour cells (CTCs) typically differ from those of primary breast cancer (BC) cells. Gene mutation analysis of CTCs in MBC may benefit patients by identifying those amenable to specific therapies. Currently, CTCs are primarily isolated in vitro from small volumes of blood. The aim of this study was to isolate CTCs in vivo using CellCollector and screen for specific gene mutations in cells from different metastasis organ sites and molecular subtypes in MBC patients.

Methods: In this study, we used a novel technology, CellCollector, to collect peripheral CTCs. Thirty MBC patients were enrolled, and 17 were analysed with next-generation sequencing (NGS) methods. Clinical characteristics were analysed along with CTC enumeration and detection rates. Whole-genome amplification (WGA) was used to amplify the CTC genomic DNA of 127 genes.

Results: We isolated CTCs in vivo from 20 of 30 MBC patients (66.7%), with a median and mean (range) of 2 (0-15) CTCs. In non-cancer patients, no CTCs were detected. We analysed CTC enumeration and the detection rate in different clinical characteristic subgroups. We found that in their corresponding subgroups, patients younger than 45 years old, with brain metastasis, with three or more metastasis organ sites, or with HER2-positive subtypes had the highest CTC medians and means.As far as clinical characteristics were concerned, the number of CTCs seemed correlated with more advanced clinical characteristics. In the one metastasis organ, two metastasis organs and three or more metastasis organs subgroups, the CTC detection rates were 38.5% (5/13), 77.8% (7/9), and 100.0% (8/8), respectively. The CTC detection rate correlated with the number of metastasis organs; patients with more metastasis organ sites had higher CTC detection rates. We also found that different metastasis organs and molecular subtypes contain high-frequency mutation genes, and also contain unique gene mutations.

Conclusions: In MBC, CellCollector can be used to collect intact CTCs, from which we can obtain gene mutation information. Different metastasis organs and molecular subtypes may have corresponding unique mutations, which may provide a basis for future gene therapy.

CTCs enumeration data and correlations to clinicopathologic characteristicsPatients' characteristics CTCs enumeration  RangemedianmeanTotal0-1522Age (years)   <450-422≥45 and <600-1512≥600-212Metastatic location   Brain0-1556Lung+liver0-712Bone+local recurrence0-411Number of metastatic locations   10-40120-15133-41-723Molecular subtypes   Luminal A000Luminal B0-511HER2 positive0-1523Triple negative0-712HER2, human epidermal growth factor receptor 2

Citation Format: Geng C, Li S, Yang S, Shi J, Ding Y, Gao W, Cheng M, Sun Y, Xie Y, Sang M. In vivo isolation of circulating tumour cells using CellCollector and detection of gene mutations in different metastasis organ sites in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-18.

MAGE-A is frequently expressed in triple negative breast cancer and associated with epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a crucial step in tumor metastasis. Triple negative (TN) breast cancer, a high metastasis phenotype, has been verified to be associated with EMT. Melanoma associated antigen-A (MAGE-A) is exclusively expressed in cancers with high aggressiveness as well as unfavorable prognosis and likely to be associated with EMT of triple negative breast cancer (TNBC). The aim of the study is to analyze the expression profile of MAGE-A in breast cancer and the correlation between MAGE-A and EMT of TNBC. Immunohistochemistry (IHC) was performed to assess the prevalence of MAGE-A, vimentin, E-cadherin and β-catenin in breast cancer tissues and correlate them with clinical pathological parameters. The association between MAGE-A and EMT markers was also evaluated. Scratch assay and transwell invasion assay were carried out to evaluate the impact of MAGE-A down-regulation on migration and invasion of the breast cancer cells. Real-time PCR was also conducted to evaluate alterations in EMT markers with decrease in MAGE-A. The results showed that MAGE-A was absent in normal tissue but expressed in tumor samples with the incidence of 49.17% (P=0.008). MAGE-A staining was higher in TNBC (76.47%, 13/17), followed by HER-2(+) (53.85%, 7/13) and Luminal set (43.33%, 39/90), and it was significantly correlated with ER (-), PR (-), HER-2 (-), lymph nodes involvement and higher histological grade (P<0.05). E-cadherin-positivity was frequent in Luminal set (94.44%, 85/90) and linked to ER (+), negative lymph nodes and lower histological grade (P<0.05). Vimentin expression was often observed in TNBC (70.56%, 12/17) and ER (-), PR (-), lymph nodes (+) groups (P<0.05). Expression of β-catenin was prevalent in Luminal set (93.33%, 84/90) and correlated with ER (+), PR (+) and lower histological grade (P<0.05). MAGE-A was inversely associated with E-cadherin (P=0.011) and β-catenin (P=0.048) but expressed in the same trend with vimentin (P=0.000). Migration and invasion of MDA-MB-231 were inhibited when MAGE-A decreased. Increase in epithelial markers and decline in mesenchymal indicators were also seen with MAGE-A reduction. Snail, Slug, ZEB1 and ZEB2 were also down-regulated. In conclusion, MAGE-A may be responsible for high aggressiveness and EMT of TNBC and can be a new choice for targeted therapy.

Tumor suppressor let-7a inhibits breast cancer cell proliferation, migration and invasion by targeting MAGE-A1

Let-7 was one of the earliest discovered miRNAs and while it reportedly acts as a tumor suppressor in various solid tumors, its function in breast cancer has not been fully studied. Therefore, we examined let-7a and MAGE-A1 expression in breast tissues by qRT-PCR and found that let-7a expression significantly correlates with larger tumor size, higher histological grade (p<0.05) and is significantly lower in patients with Her-2-positive cancers and Ki-67 >14% (p=0.028 and p=0.023). MAGE-A1 expression incidence is 50.8% (33/65) and it inversely correlates with let-7a expression (p=0.008). let-7a inhibition of breast cancer cell proliferation, migration and invasion was also observed in in vitro cell culture experiments, and dual-luciferase reporter assays showed that melanoma-associated antigen A1 (MAGE-A1) was its target gene; the target comprised bases 451-457 of the 3'UTR region of the MAGE-A1 mRNA. RT-qPCR and Western blot analyses showed that let-7a inhibited MAGE-A1 expression at both the nucleic acid and protein levels. In our final co-transfection experiment, we targeted MAGE-A1 in a breast cancer cell line and observed that let-7a inhibited cell proliferation, migration and invasion. These combined results confirm that let-7a functions as a tumor suppressor by targeting MAGE-A1 in breast cancer and it therefore provides a novel target in breast cancer clinical treatment.

Enhancing expression of SSU1 genes in Saccharomyces uvarum leads to an increase in sulfite tolerance and a transcriptome profile change

Saccharomyces uvarum is a good wine yeast species that may have great potential for the future. However, sulfur tolerance of most S. uvarum strains is very poor. In addition there is still little information about the SSU1 gene of S. uvarum, which encodes a putative transporter conferring sulfite tolerance. In order to analyze the function of the SSU1 gene, two expression vectors that contained different SSU1 genes were constructed and transferred into a sulfite-tolerant S. uvarum strain, A9. Then sulfite tolerance, SO2 production, and PCR, sequencing, RT-qPCR and transcriptome analyses were used to access the function of the S. uvarum SSU1 gene. Our results illustrated that enhancing expression of the SSU1 gene can promote sulfite resistance in S. uvarum, and an insertion fragment ahead of the additional SSU1 gene, as seen in some alleles, could affect the expression of other genes and the sulfite tolerance level of S. uvarum. This is the first report on enhancing the expression of the SSU1 gene of S. uvarum.

Improvement of gemcitabine sensitivity of p53-mutated pancreatic cancer MiaPaCa-2 cells by RUNX2 depletion-mediated augmentation of TAp73-dependent cell death

Pancreatic cancer exhibits the worst prognostic outcome among human cancers. Recently, we have described that depletion of RUNX2 enhances gemcitabine (GEM) sensitivity of p53-deficient pancreatic cancer AsPC-1 cells through the activation of TAp63-mediated cell death pathway. These findings raised a question whether RUNX2 silencing could also improve GEM efficacy on pancreatic cancer cells bearing p53 mutation. In the present study, we have extended our study to p53-mutated pancreatic cancer MiaPaCa-2 cells. Based on our current results, MiaPaCa-2 cells were much more resistant to GEM as compared with p53-proficient pancreatic cancer SW1990 cells, and there existed a clear inverse relationship between the expression levels of TAp73 and RUNX2 in response to GEM. Forced expression of TAp73α in MiaPaCa-2 cells significantly promoted cell cycle arrest and/or cell death, indicating that a large amount of TAp73 might induce cell death even in the presence of mutant p53. Consistent with this notion, overexpression of TAp73α stimulated luciferase activity driven by p53/TAp73-target gene promoters in MiaPaCa-2 cells. Similar to AsPC-1 cells, small interfering RNA-mediated knockdown of RUNX2 remarkably enhanced GEM sensitivity of MiPaCa-2 cells. Under our experimental conditions, TAp73 further accumulated in RUNX2-depleted MiaPaCa-2 cells exposed to GEM relative to GEM-treated non-silencing control cells. As expected, silencing of p73 reduced GEM sensitivity of MiPaCa-2 cells. Moreover, GEM-mediated Tyr phosphorylation level of TAp73 was much more elevated in RUNX2-depleted MiaPaCa-2 cells. Collectively, our present findings strongly suggest that knockdown of RUNX2 contributes to a prominent enhancement of GEM sensitivity of p53-mutated pancreatic cancer cells through the activation of TAp73-mediated cell death pathway, and also provides a promising strategy for the treatment of patients with pancreatic cancer bearing p53 mutation.

ATM and p53 are essential in the cell-cycle containment of DNA breaks during V(D)J recombination in vivo

V(D)J recombination is essential for the maturation of lymphocytes. Because of the involvement of cutting and joining DNA double strands, this recombination activity is strictly contained within the noncycling phases of the cell cycle. Such containment is crucial for the maintenance of genomic integrity. The ataxia telangiectasia mutated (ATM) gene is known to have a central role in sensing general DNA damage and mediating cell-cycle checkpoint. In this study, we investigated the role of ATM and its downstream targets in the cell-cycle control of V(D)J recombination in vivo. Our results revealed the persistence of double-strand breaks (DSBs) throughout the cell cycle in ATM(-/-) and p53(-/-) thymocytes, but the cell-cycle regulation of a V(D)J recombinase, Rag-2, was normal. The histone variant H2AX, which is phosphorylated during normal V(D)J recombination, was dispensable for containing DSBs. H2AX was still phosphorylated at V(D)J loci in the absence of ATM. Therefore, V(D)J recombination, a physiological DNA rearrangement process, activates the ATM/p53 pathway to contain DNA breaks within the noncycling cells and surprisingly this pathway is not important for containing Rag-2 activity. This study shows the dynamic multiple functions of ATM in maintaining genomic stability and preventing tumorigenesis in developing lymphocytes.

[Recurrence pattern and prognosis of esophageal cancer following tumor resection]

OBJECTIVE

To determine the recurrence patterns and prognosis after resection of esophageal cancer.

METHODS

One hundred eighty five patients who developed recurrence after curative resection for squamous-cell carcinoma of the thoracic esophagus were analyzed retrospectively.

RESULTS

The median recurrence time was 303 days. Recurrence pattern was catagorized into lymphatic, hematogenous, mixed and anastomotic. The number of patients in each recurrence group was 137, 11, 29, and 8, respectively. The 0.5-, 1-, 2-, 3-, and 4-year overall survival rate was 70.7%, 47.1%, 19.8%, 12.2% and 0%, respectively. Multivariate analysis showed that depth of tumor invasion, lymph node metastasis, operative procedure and different regimens of therapy were significant prognostic factors.

CONCLUSION

Lymph node metastasis and the depth of invasion may reflect the biologic behavior of the tumor. Esophagectomy with cervical anastomasis is recommended, additional cervical lymphadenectomy is beneficial in a few patients. Radiotherapy combined with chemotherapy may prolong survival time of patients with recurrence.

Transantral orbital decompression for Graves' disease

Seventy-five patients with Graves' disease have been treated by transantral orbital decompression. In the first post-operative month the average reduction in proptosis was 3 mm. In the years following the operation this reduction increased to an average of 4.5 mm. In 32% of the patients without diplopia before surgery, the diplopia that developed afterwards did not disappear, 83% of them were successfully treated by extraocular muscle surgery. Seventy per cent of the patients experienced immediate post-operative improvement of visual acuity. Only three patients remained with anaesthesia of the infra-orbital nerve. A total of 65% of the patients found the operation procedure beneficial while 76% were satisfied with the ophthalmological result. We conclude, that transantral orbital decompression, though with moderate morbidity, gives good results in patients with the orbital complications of Graves' disease.