Streptomyces sp metabolite(s) promotes Bax mediated intrinsic apoptosis and autophagy involving inhibition of mTOR pathway in cervical cancer cell lines

Antimicrobial potential of Streptomyces sp. NP73 isolated from the forest soil of Northeast India against multi-drug resistant Escherichia coli

This study reports the isolation and characterization of a Streptomyces sp. from soil, capable of producing bioactive secondary metabolites active against a variety of bacterial human pathogens. We targeted the antimicrobial activity against Escherichia coli ATCC-BAA 2469, a clinically relevant strain of bacteria harbouring resistance genes for carbapenems, extended spectrum beta-lactams, tetracyclines, fluoroquinones, etc. Preliminary screening using the spot inoculation technique identified Streptomyces sp. NP73 as the potent strain among the 74 isolated Actinomycetia strain. 16S rRNA gene and whole genome sequencing (WGS) confirmed its taxonomical identity and helped in the construction of the phylogenetic tree. WGS revealed the predicted pathways and biosynthetic gene clusters responsible for producing various types of antibiotics including the isolated compound. Bioactivity guided fractionation and chemical characterization of the active fraction, carried out using liquid chromatography, gas chromatography-mass spectrometry, infra-red spectroscopy, and nuclear magnetic resonance spectroscopy, led to the tentative identification of the active compound as Pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-, a diketopiperazine molecule. This compound exhibited excellent antimicrobial and anti-biofilm properties against E. coli ATCC-BAA 2469 with an MIC value of 15.64 µg ml-1, and the low cytotoxicity of the compound identified in this study provides hope for future drug development.

Urolithin A, induces apoptosis and autophagy crosstalk in Oral Squamous Cell Carcinoma via mTOR /AKT/ERK1/2 pathway

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the most prevalent malignancy in the world with an alarming rate of mortality. Despite the advancement in treatment strategies and drug developments, the overall survival rate remains poor. Therefore, it is imperative to develop alternative or complimentary anti cancer drugs with minimum off target effects. Urolithin A, a microbial metabolite of ellagic acid and ellagitannins produced endogenously by human gut micro biome is considered to have anti-cancerous activity. However anti tumorigenic effect of urolithin A in OSCC is yet to be elucidated. In this study, we examined whether urolithin A inhibits cell growth and induces both apoptosis and autophagy dependent cell death in OSCC cell lines.

PURPOSE

The present study aims to evaluate the potential of urolithin A to inhibit OSCC and its regulatory effect on OSCC proliferation and invasion in vitro and in vivo mouse models.

METHODS

We evaluated whether urolithin A could induce cell death in OSCC in vitro and in vivo mouse models.

RESULTS

Flow cytometric and immunoblot analysis on Urolithin A treated OSCC cell lines revealed that urolithin A markedly induced cell death of OSCC via the induction of endoplasmic reticulum stress and subsequent inhibition of AKT and mTOR signaling as evidenced by decreased levels of phosphorylated mTOR and 4EBP1. This further revealed a possible cross talk between apoptotic and autophagic signaling pathways. In vivo study demonstrated that urolithin A treatment reduced tumor size and showed a decrease in mTOR, ERK1/2 and Akt levels along with a decrease in proliferation marker, Ki67. Taken together, in vitro as well as our in vivo data indicates that urolithin A is a potential anticancer agent and the inhibition of AKT/mTOR/ERK signalling is crucial in Urolithin A induced growth suppression in oral cancer.

CONCLUSION

Urolithin A exerts its anti tumorigenic activity through the induction of apoptotic and autophagy pathways in OSCC. Our findings suggest that urolithin A markedly induced cell death of oral squamous cell carcinoma via the induction of endoplasmic reticulum stress and subsequent inhibition of AKT and mTOR signaling as evidenced by decreased levels of phosphorylated mTOR and 4EBP1. Urolithin A remarkably suppressed tumor growth in both in vitro and in vivo mouse models signifying its potential as an anticancer agent in the prevention and treatment of OSCC. Henceforth, our findings provide a new insight into the therapeutic potential of urolithin A in the prevention and treatment of OSCC.

Streptomyces sp. MNP32, a forest-dwelling Actinomycetia endowed with potent antibacterial metabolites

The Actinomycetia isolate, MNP32 was isolated from the Manas National Park of Assam, India, located in the Indo-Burma biodiversity hotspot region of Northeast India. Morphological observations and molecular characterization revealed its identity to be Streptomyces sp. with a 99.86% similar to Streptomyces camponoticapitis strain I4-30 through 16S rRNA gene sequencing. The strain exhibited broad-spectrum antimicrobial activity against a wide range of bacterial human pathogens including WHO-listed critical priority pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii. The ethyl acetate extract was found to disrupt the membrane of the test pathogens which was evidenced through scanning electron microscopy, membrane disruption assay and confocal microscopy. Cytotoxicity studies against CC1 hepatocytes demonstrated that EA-MNP32 had a negligible effect on cell viability. Chemical analysis of the bioactive fraction using gas chromatography-mass spectrometry (GC-MS) showed the presence of 2 major chemical compounds that include Phenol, 3,5-bis(1,1-dimethylethyl)- and [1,1'-Biphenyl]-2,3'-diol, 3,4',5,6'-tetrakis(1,1-dimethylethyl)- which have been reported to possess antimicrobial activity. The phenolic hydroxyl groups of these compounds were proposed to interact with the carbonyl group of the cytoplasmic proteins and lipids leading to destabilization and rupture of the cell membrane. These findings highlight the potential of exploring culturable actinobacteria from the microbiologically under-explored forest ecosystem of Northeast India and bioactive compounds from MNP32 which can be beneficial for future antibacterial drug development.

Artificial intelligence in microbial natural product drug discovery: current and emerging role

Covering: up to the end of 2022Microorganisms are exceptional sources of a wide array of unique natural products and play a significant role in drug discovery. During the golden era, several life-saving antibiotics and anticancer agents were isolated from microbes; moreover, they are still widely used. However, difficulties in the isolation methods and repeated discoveries of the same molecules have caused a setback in the past. Artificial intelligence (AI) has had a profound impact on various research fields, and its application allows the effective performance of data analyses and predictions. With the advances in omics, it is possible to obtain a wealth of information for the identification, isolation, and target prediction of secondary metabolites. In this review, we discuss drug discovery based on natural products from microorganisms with the help of AI and machine learning.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.

Beyond controlling cell size: functional analyses of S6K in tumorigenesis

As a substrate and major effector of the mammalian target of rapamycin complex 1 (mTORC1), the biological functions of ribosomal protein S6 kinase (S6K) have been canonically assigned for cell size control by facilitating mRNA transcription, splicing, and protein synthesis. However, accumulating evidence implies that diverse stimuli and upstream regulators modulate S6K kinase activity, leading to the activation of a plethora of downstream substrates for distinct pathobiological functions. Beyond controlling cell size, S6K simultaneously plays crucial roles in directing cell apoptosis, metabolism, and feedback regulation of its upstream signals. Thus, we comprehensively summarize the emerging upstream regulators, downstream substrates, mouse models, clinical relevance, and candidate inhibitors for S6K and shed light on S6K as a potential therapeutic target for cancers.

Resistance to Intervention: Paclitaxel in Breast Cancer

Breast cancer stands as the most prevalent cancer in women globally, and contributes to the highest percentage of mortality due to cancer-related deaths in women. Paclitaxel (PTX) is heavily relied on as a frontline chemotherapy drug in breast cancer treatment, especially in advanced metastatic cancer. Generation of resistance to PTX often derails clinical management and adversely affects patient outcomes. Understanding the molecular mechanism of PTX resistance is necessary to device methods to aid in overcoming the resistance. Recent studies exploring the mechanism of development of PTX resistance have led to unveiling of a range novel therapeutic targets. PTX resistance pathways that involve major regulatory proteins/RNAs like RNF8/Twist/ROR1, TLR, ErbB3/ErbB2, BRCA1- IRIS, MENA, LIN9, MiRNA, FoxM1 and IRAK1 have expanded the complexity of resistance mechanisms, and brought newer insights into the development of drug targets. These resistance-related targets can be dealt with synthetic/natural therapeutics in combination with PTX. The present review encompasses the recent understanding of PTX resistance mechanisms in breast cancer and possible therapeutic combinations to overcome resistance.

An Overview of Novel Agents for Cervical Cancer Treatment by Inducing Apoptosis: Emerging Drugs Ongoing Clinical Trials and Preclinical Studies

As the leading cause of cancer death, cervical cancer ranks fourth for both incidence and mortality. Cervical cancer incidence and mortality rates have reportedly decreased over the last decades thanks to extensive screening and widespread vaccination against human papilloma virus. However, there have been no major improvements concerning platinum-based chemotherapy on the survival of advanced cervical cancer. Thus, novel agents are urgently needed for the improvement of therapeutic effect. With the development of molecular biology and genomics, targeted therapy research has achieved a breakthrough development, including anti-angiogenesis, immune checkpoint inhibitors, and other treatments that are efficient for treatment of cervical cancer. Apoptosis is a crucial process for tumor progression. Drugs directed at inducing tumor-cell apoptosis are regarded as important treatment modalities. Besides, a number of novel compounds synthesized or derived from plants or microorganisms exhibited prominent anti-cancer activity by changing the apoptotic balance in cervical cancer. In this review, we summarized new target therapy drugs ongoing clinical trials that are used for treatment of cervical cancer. Further, we classified novel agents with a focus on improvement of therapeutic effect pre-clinically. To summarize, we also discussed application prospects of the new uses of old drugs and drug combinations, to provide researchers with new ideas for cervical cancer treatment.

Therapeutic Potential of Natural Products in Treatment of Cervical Cancer: A Review

Cervical cancer is the fourth most common cancer among women worldwide. Though several natural products have been reported regarding their efficacies against cervical cancer, there has been no review article that categorized them according to their anti-cancer mechanisms. In this study, anti-cancerous natural products against cervical cancer were collected using Pubmed (including Medline) and google scholar, published within three years. Their mechanisms were categorized as induction of apoptosis, inhibition of angiogenesis, inhibition of metastasis, reduction of resistance, and regulation of miRNAs. A total of 64 natural products suppressed cervical cancer. Among them, Penicillium sclerotiorum extracts from Cassia fistula L., ethanol extracts from Bauhinia variegate candida, thymoquinone obtained from Nigella sativa, lipid-soluble extracts of Pinellia pedatisecta Schott., and 1'S-1'-acetoxychavicol extracted from Alpinia conchigera have been shown to have multi-effects against cervical cancer. In conclusion, natural products could be attractive candidates for novel anti-cancer drugs.

Therapeutic applications and biological activities of bacterial bioactive extracts

Bacteria are rich in a wide variety of secondary metabolites, such as pigments, alkaloids, antibiotics, and others. These bioactive microbial products serve a great application in human and animal health. Their molecular diversity allows these natural products to possess several therapeutic attributes and biological functions. That's why the current natural drug industry focuses on uncovering all the possible ailments and diseases that could be combated by bacterial extracts and their secondary metabolites. In this paper, we review the major utilizations of bacterial natural products for the treatment of cancer, inflammatory diseases, allergies, autoimmune diseases, infections and other diseases that threaten public health. We also elaborate on the identified biological activities of bacterial secondary metabolites including antibacterial, antifungal, antiviral and antioxidant activities all of which are essential nowadays with the emergence of drug-resistant microbial pathogens. Throughout this review, we discuss the possible mechanisms of actions in which bacterial-derived biologically active molecular entities could possess healing properties to inspire the development of new therapeutic agents in academia and industry.

Discovery of 3-(benzofuran-2-ylmethyl)-1H-indole derivatives as potential autophagy inducers in cervical cancer cells

In this manuscript we have documented the identification of a novel anticancer scaffold 3-(benzofuran-2-ylmethyl)-1H-indole. This scaffold has been designed by tweaking the known bisindolylmethane scaffold of natural products that display a wide range of biological activities. A series of 24 new conjugates have been synthesized and among them 5 derivatives exhibited IC₅₀ values less than 40 µM against two cervical cancer cell lines SiHa and C33a. Further mechanistic studies of two compounds 3eb and 3ec revealed that the toxicity of these compounds was due to the effective induction of autophagy mediated cell death. The autophagy induction was confirmed by the progressive conversion of LC3I to LC3II and downregulation of p62 in cervical cancer cells.

Molecular Networking and Whole-Genome Analysis Aid Discovery of an Angucycline That Inactivates mTORC1/C2 and Induces Programmed Cell Death

Rediscovery of known compounds and time consumed in identification, especially high molecular weight compounds with complex structure, have let down interest in drug discovery. In this study, whole-genome analysis of microbe and Global Natural Products Social (GNPS) molecular networking helped in initial understanding of possible compounds produced by the microbe. Genome data revealed 10 biosythethic gene clusters that encode for secondary metabolites with anticancer potential. NMR analysis of the pure compound revealed the presence of a four-ringed benz[a]anthracene, thus confirming angucycline; molecular networking further confirmed production of this class of compounds. The type II polyketide synthase gene identified in the microbial genome was matched with the urdamycin cluster by BLAST analysis. This information led to ease in identification of urdamycin E and a novel natural derivative, urdamycin V, purified from Streptomyces sp. OA293. Urdamycin E (Urd E) induced apoptosis and autophagy in cancer cell lines. Urd E exerted anticancer action through inactivation of the mTOR complex by preventing phosphorylation at Ser 2448 and Ser 2481 of mTORC1 and mTORC2, respectively. Significant reduction in phosphorylation of the major downstream regulators of both mTORC1 (p70s6k and 4e-bp1) and mTORC2 (Akt) were observed, thus further confirming complete inhibition of the mTOR pathway. Urd E presents itself as a novel mTOR inhibitor that employs a novel mechanism in mTOR pathway inhibition.

mTORC1 as a Regulator of Mitochondrial Functions and a Therapeutic Target in Cancer

Continuous proliferation of tumor cells requires constant adaptations of energy metabolism to rapidly fuel cell growth and division. This energetic adaptation often comprises deregulated glucose uptake and lactate production in the presence of oxygen, a process known as the "Warburg effect." For many years it was thought that the Warburg effect was a result of mitochondrial damage, however, unlike this proposal tumor cell mitochondria maintain their functionality, and is essential for integrating a variety of signals and adapting the metabolic activity of the tumor cell. The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of numerous cellular processes implicated in proliferation, metabolism, and cell growth. mTORC1 controls cellular metabolism mainly by regulating the translation and transcription of metabolic genes, such as peroxisome proliferator activated receptor γ coactivator-1 α (PGC-1α), sterol regulatory element-binding protein 1/2 (SREBP1/2), and hypoxia inducible factor-1 α (HIF-1α). Interestingly it has been shown that mTORC1 regulates mitochondrial metabolism, thus representing an important regulator in mitochondrial function. Here we present an overview on the role of mTORC1 in the regulation of mitochondrial functions in cancer, considering new evidences showing that mTORC1 regulates the translation of nucleus-encoded mitochondrial mRNAs that result in an increased ATP mitochondrial production. Moreover, we discuss the relationship between mTORC1 and glutaminolysis, as well as mitochondrial metabolites. In addition, mitochondrial fission processes regulated by mTORC1 and its impact on cancer are discussed. Finally, we also review the therapeutic efficacy of mTORC1 inhibitors in cancer treatments, considering its use in combination with other drugs, with particular focus on cellular metabolism inhibitors, that could help improve their anti neoplastic effect and eliminate cancer cells in patients.

Arsenite-induced apoptosis can be attenuated via depletion of mTOR activity to restore autophagy

Arsenic and its compounds are toxic environmental pollutants and known carcinogens. We investigated here the mechanism of arsenite-induced damage in renal cells. Treating human embryonic kidney cells (HEK293) with sodium arsenite reduces cell viability in a dose- and time-dependent manner. The decline of cell viability is due to apoptotic death since arsenite treatment reduces Akt activity and the Bcl2 level but increases caspase 3 activity and the cytochrome c level. These effects can be reverted by the addition of an apoptosis inhibitor. PTEN, the upstream negative regulator of Akt activity, was also reduced with arsenite treatment. Noticeably, PTEN markedly increased in the insoluble fraction of the cells, suggesting a cell failure in removing the damaged proteins. Arsenite treatment activates a variety of signaling factors. Among them, ERK and JNK are associated with autophagy via regulating the levels of LC3 and p62. With arsenite administration, the LC3 and p62 levels increased. However, lysosomal activity was decreased and led to the decline of autophagic activity. The addition of rapamycin, the mTOR inhibitor, activated the autophagic pathway that accelerated the removal of damaged proteins. The recovery of autophagy increased the viability of arsenite-treated cells. Similar to rapamycin treatment, the knockdown of mTOR expression also enhanced the viability of arsenite-treated cells. Both rapamycin treatment and mTOR knockdown enhanced ERK activity further, but reduced JNK activity and the p62 level in arsenite-treated cells. Lysosomal activity increased with the depletion of mTOR, indicating an increase of autophagic activity. These results reveal the critical role of mTOR in regulating the cell fate of arsenite-exposed renal cells.