Prodigiosin induces the proapoptotic gene NAG-1 via glycogen synthase kinase-3beta activity in human breast cancer cells

Actively Targeted Nanomedicines: A New Perspective for the Treatment of Pregnancy-Related Diseases

More than 20% of pregnant women experience serious complications during pregnancy, that gravely affect the safety of both the mother and the child. Due to the unique state of pregnancy, medication during pregnancy is subject to various restrictions. Nanotechnology is an emerging technology that has been the focus of extensive medical research, and great progress has recently been made in developing sensitive diagnostic modalities and efficient medical treatment. Accumulating evidence has shown that nanodrug delivery systems can significantly improve the targeting, reduce the toxicity and improve the bioavailability of drugs. Recently, some actively targeted nanomedicines have been explored in the treatment of pregnancy-related diseases. This article reviews common types of nanocarriers and active targeting ligands in common pregnancy-related diseases and complications such as preeclampsia, preterm birth, fetal growth restriction, and choriocarcinoma. Finally, the challenges and future prospects in the development of these nanomaterials are discussed, with the aim of providing guidance for future research directions.

GDF15 induces chemoresistance to oxaliplatin by forming a reciprocal feedback loop with Nrf2 to maintain redox homeostasis in colorectal cancer

PURPOSE

Growth differentiating Factor 15 (GDF15) is linked to several cancers, but its effect on chemoresistance in colorectal cancer (CRC) remains unclear. Here, we investigated the role of GDF15 in the chemotherapeutic response of CRC patients to oxaliplatin (L-OHP).

METHODS

GDF15 levels in serum and tumour tissues were detected in CRC patients have received L-OHP-based neoadjuvant chemotherapy. The effects of GDF15 neutralization or GDF15 knockdown on cell proliferation, apoptosis and intracellular reactive oxygen species (ROS) levels were analysed in vitro and in vivo. Co-immunoprecipitation (Co-IP), Chromatin Immunoprecipitation (ChIP) and luciferase reporter assays were used to explore the interaction between GDF15 and Nrf2.

RESULTS

In this study, we found that GDF15 alleviates oxidative stress to induce chemoresistance of L-OHP in CRC. Mechanically, GDF15 posttranscriptionally regulates protein stability of Nrf2 through the canonical PI3K/AKT/GSK3β signaling pathway, and in turn, Nrf2 acts as a transcription factor to regulate GDF15 expression to form a positive feedback loop, resulting in the maintenance of redox homeostasis balance in CRC. Furthermore, a positive correlation between GDF15 and Nrf2 was observed in clinical CRC samples, and simultaneous overexpression of both GDF15 and Nrf2 was associated with poor prognosis in CRC patients treated with L-OHP. Simultaneous inhibition of both GDF15 and Nrf2 significantly increases the response to L-OHP in an L-OHP-resistant colorectal cancer cells-derived mouse xenograft model.

CONCLUSION

This study identified a novel GDF15-Nrf2 positive feedback loop that drives L-OHP resistance and suggested that the GDF15-Nrf2 axis is a potential therapeutic target for the treatment of L-OHP-resistant CRC.

In-vivo studies of targeted and localized cancer drug release from microporous poly-di-methyl-siloxane (PDMS) devices for the treatment of triple negative breast cancer

Triple-negative breast cancer (TNBC) treatment is challenging and frequently characterized by an aggressive phenotype and low prognosis in comparison to other subtypes. This paper presents fabricated implantable drug-loaded microporous poly-di-methyl-siloxane (PDMS) devices for the delivery of targeted therapeutic agents [Luteinizing Hormone-Releasing Hormone conjugated paclitaxel (PTX-LHRH) and Luteinizing Hormone-Releasing Hormone conjugated prodigiosin (PG-LHRH)] for the treatment and possible prevention of triple-negative cancer recurrence. In vitro assessment using the Alamar blue assay demonstrated a significant reduction (p < 0.05) in percentage of cell growth in a time-dependent manner in the groups treated with PG, PG-LHRH, PTX, and PTX-LHRH. Subcutaneous triple-negative xenograft breast tumors were then induced in athymic female nude mice that were four weeks old. Two weeks later, the tumors were surgically but partially removed, and the device implanted. Mice were observed for tumor regrowth and organ toxicity. The animal study revealed that there was no tumor regrowth, six weeks post-treatment, when the LHRH targeted drugs (LHRH-PTX and LHRH-PGS) were used for the treatment. The possible cytotoxic effects of the released drugs on the liver, kidney, and lung are assessed using quantitative biochemical assay from blood samples of the treatment groups. Ex vivo histopathological results from organ tissues showed that the targeted cancer drugs released from the implantable drug-loaded device did not induce any adverse effect on the liver, kidneys, or lungs, based on the results of qualitative toxicity studies. The implications of the results are discussed for the targeted and localized treatment of triple negative breast cancer.

Rise of the natural red pigment 'prodigiosin' as an immunomodulator in cancer

Cancer is a heterogeneous disease with multifaceted drug resistance mechanisms (e.g., tumour microenvironment [TME], tumour heterogeneity, and immune evasion). Natural products are interesting repository of bioactive molecules, especially those with anticancer activities. Prodigiosin, a red pigment produced by Serratia marcescens, possesses inherent anticancer characteristics, showing interesting antitumour activities in different cancers (e.g., breast, gastric) with low or without harmful effects on normal cells. The present review discusses the potential role of prodigiosin in modulating and reprogramming the metabolism of the various immune cells in the TME, such as T and B lymphocytes, tumour-associated macrophages (TAMs), natural killer (NK) cells, and tumour-associated dendritic cells (TADCs), and myeloid-derived suppressor cells (MDSCs) which in turn might introduce as an immunomodulator in cancer therapy.

Bacteria as a treasure house of secondary metabolites with anticancer potential

Cancer stands in the frontline among leading killers worldwide and the annual mortality rate is expected to reach 16.4 million by 2040. Humans suffer from about 200 different types of cancers and many of them have a small number of approved therapeutic agents. Moreover, several types of major cancers are diagnosed at advanced stages as a result of which the existing therapies have limited efficacy against them and contribute to a dismal prognosis. Therefore, it is essential to develop novel potent anticancer agents to counteract cancer-driven lethality. Natural sources such as bacteria, plants, fungi, and marine microorganisms have been serving as an inexhaustible source of anticancer agents. Notably, over 13,000 natural compounds endowed with different pharmacological properties have been isolated from different bacterial sources. In the present article, we have discussed about the importance of natural products, with special emphasis on bacterial metabolites for cancer therapy. Subsequently, we have comprehensively discussed the various sources, mechanisms of action, toxicity issues, and off-target effects of clinically used anticancer drugs (such as actinomycin D, bleomycin, carfilzomib, doxorubicin, ixabepilone, mitomycin C, pentostatin, rapalogs, and romidepsin) that have been derived from different bacteria. Furthermore, we have also discussed some of the major secondary metabolites (antimycins, chartreusin, elsamicins, geldanamycin, monensin, plicamycin, prodigiosin, rebeccamycin, salinomycin, and salinosporamide) that are currently in the clinical trials or which have demonstrated potent anticancer activity in preclinical models. Besides, we have elaborated on the application of metagenomics in drug discovery and briefly described about anticancer agents (bryostatin 1 and ET-743) identified through the metagenomics approach.

Anticancer Potential of Compounds from the Brazilian Blue Amazon

"Blue Amazon" is used to designate the Brazilian Economic Exclusive Zone, which covers an area comparable in size to that of its green counterpart. Indeed, Brazil flaunts a coastline spanning 8000 km through tropical and temperate regions and hosting part of the organisms accredited for the country's megadiversity status. Still, biodiversity may be expressed at different scales of organization; besides species inventory, genetic characteristics of living beings and metabolic expression of their genes meet some of these other layers. These metabolites produced by terrestrial creatures traditionally and lately added to by those from marine organisms are recognized for their pharmaceutical value, since over 50% of small molecule-based medicines are related to natural products. Nonetheless, Brazil gives a modest contribution to the field of pharmacology and even less when considering marine pharmacology, which still lacks comprehensive in-depth assessments toward the bioactivity of marine compounds so far. Therefore, this review examined the last 40 years of Brazilian natural products research, focusing on molecules that evidenced anticancer potential-which represents ~ 15% of marine natural products isolated from Brazilian species. This review discusses the most promising compounds isolated from sponges, cnidarians, ascidians, and microbes in terms of their molecular targets and mechanisms of action. Wrapping up, the review delivers an outlook on the challenges that stand against developing groundbreaking natural products research in Brazil and on a means of surpassing these matters.

Bacterial Pigment Prodigiosin Demonstrates a Unique Antiherpesvirus Activity That Is Mediated through Inhibition of Prosurvival Signal Transducers

Herpes simplex virus (HSV) is among the most prevalent viral infections worldwide and remains incurable. While nucleoside analogs are used to relieve symptoms of infection, they suffer from having serious adverse effects and are unable to abolish the virus from the host. Here, we demonstrate a unique antiviral effect of prodigiosin (PG), a natural secondary metabolite produced by Serratia marcescens, on HSV infection. We show that PG naturally exerts antiviral activity against HSV-1 and HSV-2 infections. PG treatment resulted in robust inhibition of viral replication in vitro and ex vivo in cultured porcine corneas. Additionally, PG protected against HSV-1 infection and disease progression in a murine model of ocular infection. In our quest to determine the molecular mechanisms of its antiviral activity, we show that PG specifically inhibits NF-κB and Akt signaling pathways and promotes accelerated cell death in HSV-infected cells. Our findings reveal novel antiviral properties of PG, suggesting its high potential as an alternative treatment for herpetic diseases. They also provide new information on antiviral effects of HSV-bacterial metabolite interactions.IMPORTANCE In this article, we provide a new role for a commonly found bacterial pigment in controlling herpes simplex virus infection, for which diverse and multimodal antiviral agents are needed to prevent drug resistance. Serratia marcescens is a red pigment (prodigiosin)-producing Gram-negative bacillus that is naturally found in soil and water. It is associated with many kinds of human infections, including wound and eye infections, and meningitis. Taking cues from previous studies on prodigiosin, including possible proapoptotic anticancer properties, we investigated how it might affect HSV infection. Interestingly, we found that it is a potent virucidal compound that disrupts host signaling pathways needed for HSV growth and survival. The mode of antiviral action suggests potentially broad activity against enveloped viruses. Our results also indicate that interactions with commensal bacteria may inhibit HSV infection, underscoring the importance of studying these microbial metabolites and their implications for viral pathogenesis and treatment.

Production and Potential Applications of Bioconversion of Chitin and Protein-Containing Fishery Byproducts into Prodigiosin: A Review

The technology of microbial conversion provides a potential way to exploit compounds of biotechnological potential. The red pigment prodigiosin (PG) and other PG-like pigments from bacteria, majorly from Serratia marcescens, have been reported as bioactive secondary metabolites that can be used in the broad fields of agriculture, fine chemicals, and pharmacy. Increasing PG productivity by investigating the culture conditions especially the inexpensive carbon and nitrogen (C/N) sources has become an important factor for large-scale production. Investigations into the bioactivities and applications of PG and its related compounds have also been given increased attention. To save production cost, chitin and protein-containing fishery byproducts have recently been investigated as the sole C/N source for the production of PG and chitinolytic/proteolytic enzymes. This strategy provides an environmentally-friendly selection using inexpensive C/N sources to produce a high yield of PG together with chitinolytic and proteolytic enzymes by S. marcescens. The review article will provide effective references for production, bioactivity, and application of S. marcescens PG in various fields such as biocontrol agents and potential pharmaceutical drugs.

The production and bioactivity of prodigiosin: quo vadis?

Prodigiosin (PG), a red tripyrrole pigment, belongs to a member of the prodiginine family and is normally secreted by various sources including Serratia marcescens and other Gram-negative bacteria. The studies of PG have received innovative devotion as a result of reported antimicrobial, larvicidal and anti-nematoid immunomodulation and antitumor properties, owing to its antibiotic and cytotoxic activities. This review provides a comprehensive summary of research undertaken toward the isolation and structural elucidation of the prodiginine family of natural products. Additionally, the current evidence-based understanding of the biological activities and medicinal potential of PG is employed to determine the efficacy, with some reports of information related to pharmacokinetics, pharmacodynamics and toxicology.

Targeted Delivery Prodigiosin to Choriocarcinoma by Peptide-Guided Dendrigraft Poly-l-lysines Nanoparticles

The available and effective therapeutic means to treat choriocarcinoma is seriously lacking, mainly due to the toxic effects caused by chemotherapy and radiotherapy. Accordingly, we developed a method for targeting delivery of chemotherapeutical drugs only to cancer cells, not normal cells, in vivo, by using a synthetic placental chondroitin sulfate (CSA)-binding peptide (plCSA-BP) derived from malarial protein VAR2CSA. A 28 amino acids placental CSA-binding peptide (plCSA-BP) from the VAR2CSA was synthesized as a guiding peptide for tumor-targeting delivery, dendrigraft poly-L-lysines (DGL) was modified with plCSA-BP and served as a novel targeted delivery carrier. Choriocarcinoma was selected to test the effect of targeted delivery carrier, and prodigiosin isolated from Serratia marcescens subsp. lawsoniana was selected as a chemotherapeutical drug and encapsulated in the DGL modified by the plCSA-BP nanoparticles (DGL/CSA-PNPs). DGL/CSA-PNPs had a sustained slow-release feature at pH 7.4, which could specifically bind to the JEG3 cells and exhibited better anticancer activity than that of the controls. The DGL/CSA-PNPs induced the apoptosis of JEG3 cells through caspase-3 and the P53 signaling pathway. DGL/CSA-PNPs can be used as an excellent targeted delivery carrier for anticancer drugs, and the prodigiosin could be an alternative chemotherapeutical drug for choriocarcinoma.

Growth differentiation factor 15 (GDF15): A survival protein with therapeutic potential in metabolic diseases

Growth Differentiation Factor 15 (GDF15), also known as NSAID activated gene-1 (NAG-1), is associated with a large number of biological processes and diseases, including cancer and obesity. GDF15 is synthesized as pro-GDF15, is dimerized, and is cleaved and secreted into the circulation as a mature dimer GDF15. Both the intracellular GDF15 and the circulating mature GDF15 are implicated in biological processes, such as energy homeostasis and body weight regulation. Although there have been many studies on GDF15, GFRAL, a member of the glial-derived neurotropic factor receptor α family, has only been recently identified as a receptor for mature GDF15. In this review, we focused on cancer and energy homeostasis along with obesity and body weight, and the effect of the identification of the GDF15 receptor in these investigations. In addition, the therapeutic potential of GDF15 as a pharmacological agent in obesity and other metabolic diseases was discussed.

Genotoxic activity of L-asparaginase produced by Streptomyces ansochromogenes UFPEDA 3420

L-asparaginase is an enzyme capable of hydrolyzing the substrate asparagine in aspartic acid and ammonia. Due to this mechanism of action observed, L-asparaginase is widely used in the treatment of Acute Lymphoblastic Leukemia, since these cells use asparagine for their survival. Because it is frequently used as an antineoplastic, it is necessary to evaluate its genotoxic effects. The aim of the present study was to evaluate cellular DNA damage after exposure to L-asparaginase produced by Streptomyces ansochromogenes UFPEDA 3420. NCIH-292, MCF-7 and MOLT-4 neoplastic cell lines and normal PBMC cells were used. L-Asparaginase used in this study was produced by actinobacteria S. ansochromogenes UFPEDA 3420, isolated and purified by chromatographic methods. L-Asparaginase induced micronucleus formation in PBMC cells and tumor lines when compared to the negative control. These data suggest that L-Asp appears to have a genotoxic effect very close to the positive control in normal cells (p < 0.05). The level of genomic damage measured by DNA breaks in alkaline SCGE assay was detected from the lowest concentration (12.5 µg/mL) to the highest concentration (50 µg/mL) for tumor cell lines and PBMC. In view of the above, new genotoxic studies will be carried out to better elucidate L-Asparaginase and its mutagenic potential, still unknown, enough for this drug to be safely used in conventional antineoplastic therapies.

Comparative Transcriptomics Unravels Prodigiosin's Potential Cancer-Specific Activity Between Human Small Airway Epithelial Cells and Lung Adenocarcinoma Cells

Objective: Non-Small Cell Lung Cancer (NSCLC) is extremely lethal upon metastasis and requires safe and effective systemic therapies to improve a patient's prognosis. Prodigiosin (PG) appears to selectively and effectively target cancer but not healthy cells. However, PG's cancer-specific activity has remained elusive until recently. Methods: PG's cancer-specific performance was compared to Docetaxel (DTX), Paclitaxel (PTX), and Doxorubicin (DOX) against human lung adenocarcinoma (A549) and human small airway epithelial cells (HSAEC). Combination of PG with DTX, PTX, or DOX in a 1:1 ED50 ratio was also evaluated. MTT assay was used to determine the post-treatment cell viability. RNA-sequencing was used for comparative transcriptomics analysis between A549 and HSAEC treated with 1.0 μM PG for 24 h. Results: PG reduced A549 cell viability by four-folds greater than HSAEC. In comparison to DTX, PTX and DOX, PG was ~1.7 times more toxic toward A549, and 2.5 times more protective toward HSAEC. Combination of PG in a 1:1 ED50 ratio with DTX, PTX, or DOX failed to exhibit synergistic toxicity toward A549 or protection toward HSAEC. In A549, genes associated in DNA replication were downregulated, while genes directly or indirectly associated in lipid and cholesterol biogenesis were upregulated. In HSAEC, co-upregulation of oncogenic and tumor-suppressive genes was observed. Conclusion: An overactive lipid and cholesterol biogenesis could have caused A549's autophagy, while a balancing-act between genes of oncogenic and tumor-suppressive nature could have conferred HSAEC heightened survival. Overall, PG appears to be a smart chemotherapeutic agent that may be both safe and effective for NSCLC patients.

Prodigiosin-Emerged PI3K/Beclin-1-Independent Pathway Elicits Autophagic Cell Death in Doxorubicin-Sensitive and -Resistant Lung Cancer

Prodigiosin (PG) belongs to a family of prodiginines isolated from gram-negative bacteria. It is a water insoluble red pigment and a potent proapoptotic compound. This study elucidates the anti-tumor activity and underlying mechanism of PG in doxorubicin-sensitive (Dox-S) and doxorubicin-resistant (Dox-R) lung cancer cells. The cytotoxicity and cell death characteristics of PG in two cells were measured by MTT assay, cell cycle analysis, and apoptosis/autophagic marker analysis. Then, the potential mechanism of PG-induced cell death was evaluated through the phosphatidylinositol-4,5-bisphosphate 3-kinase-p85/Protein kinase B /mammalian target of rapamycin (PI3K-p85/Akt/mTOR) and Beclin-1/phosphatidylinositol-4,5-bisphosphate 3-kinase-Class III (Beclin-1/PI3K-Class III) signaling. Finally, in vivo efficacy was examined by intratracheal inoculation and treatment. There was similar cytotoxicity with PG in both Dox-S and Dox-R cells, where the half maximal inhibitory concentrations (IC₅₀) were all in 10 μM. Based on a non-significant increase in the sub-G₁ phase with an increase of microtubule-associated proteins 1A/1B light chain 3B-phosphatidylethanolamine conjugate (LC3-II), the cell death of both cells was categorized to achieve autophagy. Interestingly, an increase in cleaved-poly ADP ribose polymerase (cleaved-PARP) also showed the existence of an apoptosis-sensitive subpopulation. In both Dox-S and Dox-R cells, PI3K-p85/Akt/mTOR signaling pathways were reduced, which inhibited autophagy initiation. However, Beclin-1/PI3K-Class III downregulation implicated non-canonical autophagy pathways were involved in PG-induced autophagy. At completion of the PG regimen, tumors accumulated in the mice trachea and were attenuated by PG treatment, which indicated the efficacy of PG for both Dox-S and Dox-R lung cancer. All the above results concluded that PG is a potential chemotherapeutic agent for lung cancer regimens regardless of doxorubicin resistance.

Effects of non-steroidal anti-inflammatory drug-activated gene-1 on Ganoderma lucidum polysaccharides-induced apoptosis of human prostate cancer PC-3 cells

Ganoderma lucidum polysaccharides (GLP) has been demonstrated to elicit antitumorigenic and proapoptotic activities in cancer; however, the molecular mechanisms underlying the anticancer effects of GLP have yet to be elucidated. Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) has been reported to exert proapoptotic effects and therefore, may serve an important role in cancer prevention. The present study aimed to elucidate the molecular mechanism by which GLP stimulates anticancer activity in human prostate cancer (PCa) PC-3 cells. In addition, the role of NAG-1 in GLP-induced cancer inhibition was examined. The results of the present study demonstrated that GLP significantly inhibited cell viability in a time- and dose-dependent manner in PC-3 cells. Flow cytometry indicated that GLP induced late apoptosis, which was accompanied by poly (ADP-ribose) polymerase 1 (PARP) cleavage, and inhibition of pro-caspase-3, -6 and -9 protein expression. Furthermore, it was observed that the expression levels of NAG-1, and its transcriptional factor early growth response-1, were upregulated in a time- and dose-dependent manner upon GLP treatment. The results of a luciferase assay demonstrated that GLP induced the promoter activity of NAG-1, thus indicating that NAG-1 may be transcriptionally regulated by GLP. The secretion of NAG-1 proteins into the cell culture medium was also upregulated upon GLP treatment. Furthermore, inhibition of NAG-1 expression by small interfering RNA significantly, but not completely, prevented GLP-induced apoptosis, and reversed the effects of GLP on PARP and pro-caspase expression. It was further demonstrated that GLP inhibited the phosphorylation of protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling in PC-3 cells. The present study is the first, to the best of our knowledge, to report that GLP may induce apoptosis of PCa cells, which is partially mediated through NAG-1 induction. The present findings may be helpful in elucidating the anticancer mechanisms of GLP through NAG-1 induction for its chemopreventive potential in PCa.

Prodigiosin inhibits Wnt/β-catenin signaling and exerts anticancer activity in breast cancer cells

Prodigiosin, a natural red pigment produced by numerous bacterial species, has exhibited promising anticancer activity; however, the molecular mechanisms of action of prodigiosin on malignant cells remain unclear. Aberrant activation of the Wnt/β-catenin signaling cascade is associated with numerous human cancers. In this study, we identified prodigiosin as a potent inhibitor of the Wnt/β-catenin pathway. Prodigiosin blocked Wnt/β-catenin signaling by targeting multiple sites of this pathway, including the low-density lipoprotein-receptor-related protein (LRP) 6, Dishevelled (DVL), and glycogen synthase kinase-3β (GSK3β). In breast cancer MDA-MB-231 and MDA-MB-468 cells, nanomolar concentrations of prodigiosin decreased phosphorylation of LRP6, DVL2, and GSK3β and suppressed β-catenin-stimulated Wnt target gene expression, including expression of cyclin D1. In MDA-MB-231 breast cancer xenografts and MMTV-Wnt1 transgenic mice, administration of prodigiosin slowed tumor progression and reduced the expression of phosphorylated LRP6, phosphorylated and unphosphorylated DVL2, Ser9 phosphorylated GSK3β, active β-catenin, and cyclin D1. Through its ability to inhibit Wnt/β-catenin signaling and reduce cyclin D1 levels, prodigiosin could have therapeutic activity in advanced breast cancers.

Hypoxic inactivation of glycogen synthase kinase-3β promotes gastric tumor growth and angiogenesis by facilitating hypoxia-inducible factor-1 signaling

Since the molecular mechanism of hypoxic adaptation in cancer cells is cell-type specific, we investigated whether glycogen synthase kinase-3β (GSK-3β) activation is involved in hypoxia-induced gastric tumor promotion. Stable gastric cancer cell lines (SNU-638, SNU-484, MKN1, and MKN45) were cultured under hypoxic conditions. Cells overexpressing wild-type GSK-3β (WT-GSK-3β) or kinase-dead mutant of GSK-3β (KD-GSK-3β) were generated and used for cell culture and animal studies. In cell culture experiments, hypoxia decreased GSK-3β activation in gastric cancer cells. Cell viability and the expressions of HIF-1α protein and VEGF mRNA in gastric cancer cells were higher in KD-GSK-3β transfectants than in WT-GSK-3β transfectants under hypoxic conditions, but not under normoxic conditions. Gastric cancer xenografts showed that tumor growth, microvessel area, HIF-1α activation, and VEGF expression were higher in KD-GSK-3β tumors than in WT-GSK-3β tumors in vivo. In addition, the expression of hypoxia-induced HIF-1α protein was regulated by GSK-3β at the translational level. Our data suggest that GSK-3β is involved in hypoxic adaptation of gastric cancer cells as an inhibitory upstream regulator of the HIF-1α/VEGF signaling pathway.

Prodigiosin and its potential applications

Since a decade, there has been a strong consumer demand for more natural products. This has augmented inclination towards substitution of synthetic colorants with natural pigments. Natural pigments not only have the capacity to increase the marketability of products, they also demonstrate valuable biological activities as antioxidants and anticancer agents. There is a long history of exploitation of natural products produced by bacteria as sources of pharmaceutically important, bioactive compounds. Among natural pigments, pigments from microbial sources are potentially suitable alternatives to synthetic pigments. The red pigment prodigiosin (PG) has unusual properties, which have long been documented. The red-pigmented prodiginines are bioactive secondary metabolites produced by both Gram-negative and Gram-positive bacteria. Prodigiosins are characterized by a common pyrrolyl pyrromethene skeleton, and the biological role of these pigments in the producer organisms remains unclear. Bacterial prodigiosins and their synthetic derivatives are effective proapoptotic agents against various cancer cell lines, with multiple cellular targets including multi-drug resistant cells with little or no toxicity towards normal cell lines. However, research into the biology of pigment production will stimulate interest in the bioengineering of strains to synthesize useful prodiginine derivatives. This review article highlights the characteristics and potential applications of prodigiosin pigment from Serratia as prodigiosins are real potential therapeutic drugs.

Reduced expression of GDF-15 is associated with atrophic inflammatory lesions of the prostate

BACKGROUND

Accumulating evidence suggests that chronic prostatic inflammation may lead to prostate cancer development. Growth differentiation factor-15 (GDF-15) is highly expressed in the prostate and has been associated with inflammation and tumorigenesis.

METHODS

To examine the relationship between GDF-15 and prostatic inflammation, GDF-15 expression was measured by immunohistochemical (IHC) staining in human prostatectomy specimens containing inflammation. The relationship between GDF-15 and specific inflammatory cells was determined using non-biased computer image analysis. To provide insight into a potential suppressive role for GDF-15 in inflammation, activation of inflammatory mediator nuclear factor of kappa B (NFκB) was measured in PC3 cells.

RESULTS

GDF-15 expression in luminal epithelial cells was decreased with increasing inflammation severity, suggesting an inverse association between GDF-15 and inflammation. Quantification of IHC staining by image analysis for GDF-15 and inflammatory cell markers revealed an inverse correlation between GDF-15 and CD3+, CD4+, CD8+, CD68+, and inos+ leukocytes. GDF-15 suppressed NFκB activity in luciferase reporter assays. Expression of the NFκB target, interleukin 8 (IL-8), was downregulated by GDF-15.

CONCLUSIONS

The inverse relationship between GDF-15 and inflammation demonstrates a novel expression pattern for GDF-15 in the human prostate and suppression of NFκB activity may shed light on a potential mechanism for this inverse correlation.

Copper-obatoclax derivative complexes mediate DNA cleavage and exhibit anti-cancer effects in hepatocellular carcinoma

Obatoclax is an indole-pyrrole compound that induces cancer cell apoptosis through targeting the anti-apoptotic Bcl-2 protein family. Previously, we developed a series of obatoclax derivatives and studied their STAT3 inhibition-dependent activity against cancer cell lines. The obatoclax analog, prodigiosin, has been reported to mediate DNA cleavage in cancer cells by coordinating with copper complexes. To gain an understanding of copper-obatoclax complex activity, we applied obatoclax derivatives to examine their copper-mediated nuclease activity as a means to establish a basis for structure activity relationship. Replacement of the indole ring of obatoclax with furanyl, thiophenyl or Boc-indolyl rings reduced the DNA cleavage ability. The same effect was achieved through the replacement of the obatoclax pyrrolyl ring with thiazolidinedione and thioacetal. Among the compounds tested, we demonstrated that the complex of obatoclax or compound 7 with copper exhibited potent DNA strand scission which correlated with HCC cell growth inhibition.

GSK3β overexpression indicates poor prognosis and its inhibition reduces cell proliferation and survival of non-small cell lung cancer cells

BACKGROUND

Glycogen synthase kinase 3 beta (GSK3β) is centrally involved in diverse cellular processes, including proliferation and apoptosis. This study aimed to investigate the influence of GSK3β expression on the prognosis of human non-small cell lung cancer (NSCLC) and the effects of GSK3β inhibition in NSCLC cell lines.

METHODS

Immunohistochemical and western blot assays were used to evaluate the GSK3β expression level in human NSCLC tissues. Lentiviral RNA interference was performed to inhibit the expression of GSK3β in the A549, H292, H1299 and SK-MES-1 cell lines. Cell survival, apoptosis and motility were evaluated in vivo and in vitro.

RESULTS

The levels of GSK3β were greater in NSCLC tissues (n = 211) than in control tissues (n = 194) (P<0.001). The 5-year follow-up analysis showed that positive GSK3β expression was indicative of poor prognosis (P = 0.006). Furthermore, knockdown of GSK3β in NSCLC cell lines suppressed cell proliferation, arrested tumor cells in G0/G1 phase, induced apoptosis and reduced cell motility. A xenograft model showed that the deregulation of GSK3β attenuated tumorigenesis, as confirmed by reduced cell proliferation based on Ki-67 and significantly increased apoptotic cell death. The inhibition of GSK3β had inconsistent effects on the expression of β-catenin, depending on the cell type examined.

CONCLUSION

Aberrant expression of GSK3β serves as an independent marker of poor prognosis for NSCLC. The inhibition of GSK3β suppressed tumorigenesis by attenuating cell proliferation, increasing apoptosis and restraining cell motility. These results identify GSK3β as a tumor promoter and a potential therapeutic target in NSCLC.

Properties and applications of undecylprodigiosin and other bacterial prodigiosins

The growing demand to fulfill the needs of present-day medicine in terms of novel effective molecules has lead to reexamining some of the old and known bacterial secondary metabolites. Bacterial prodigiosins (prodiginines) have a long history of being re markable multipurpose compounds, best examined for their anticancer and antimalarial activities. Production of prodigiosin in the most common producer strain Serratia marcescens has been described in great detail. However, few reports have discussed the ecophysiological roles of these molecules in the producing strains, as well as their antibiotic and UV-protective properties. This review describes recent advances in the production process, biosynthesis, properties, and applications of bacterial prodigiosins. Special emphasis is put on undecylprodigiosin which has generally been a less studied member of the prodigiosin family. In addition, it has been suggested that proteins involved in undecylprodigiosin synthesis, RedG and RedH, could be a useful addition to the biocatalytic toolbox being able to mediate regio- and stereoselective oxidative cyclization. Judging by the number of recent references (216 for the 2007-2013 period), it has become clear that undecylprodigiosin and other bacterial prodigiosins still hold surprises in terms of valuable properties and applicative potential to medical and other industrial fields and that they still deserve continuing research curiosity.

Activation of AMP-activated protein kinase and phosphorylation of glycogen synthase kinase3 β mediate ursolic acid induced apoptosis in HepG2 liver cancer cells

Despite the antitumour effect of ursolic acid observed in several cancers, the underlying mechanism remains unclear. Thus, in the present study, the roles of AMP-activated protein kinase (AMPK) and glycogen synthase kinase 3 beta (GSK3β) were examined in ursolic acid induced apoptosis in HepG2 hepatocellular carcinoma cells. Ursolic acid significantly exerted cytotoxicity, increased the sub-G1 population and the number of ethidium homodimer and terminal deoxynucleotidyl transferase(TdT) mediated dUTP nick end labeling positive cells in HepG2 cells. Also, ursolic acid enhanced the cleavages of poly-ADP-ribose polymerase (PARP) and caspase3, attenuated the expression of astrocyte elevated gene (AEG1) and survivin in HepG2 cells. Interestingly, ursolic acid increased the phosphorylation of AMPK and coenzyme A carboxylase and also enhanced phosphorylation of GSK3β at inactive form serine 9, whereas ursolic acid attenuated the phosphorylation of AKT and mTOR in HepG2 cells. Conversely, AMPK inhibitor compound C or GSK3β inhibitor SB216763 blocked the cleavages of PARP and caspase 3 induced by ursolic acid in HepG2 cells. Furthermore, proteosomal inhibitor MG132 suppressed AMPK activation, GSK3β phosphorylation, cleaved PARP and deceased AEG-1 induced by ursolic acid in HepG2 cells. Overall, our findings suggest that ursolic acid induced apoptosis in HepG2 cells via AMPK activation and GSK3β phosphorylation as a potent chemopreventive agent.

Undecylprodigiosin induced apoptosis in P388 cancer cells is associated with its binding to ribosome

Prodigiosins (PGs) are a family of natural red pigments with anticancer activity, and one member of the family has entered clinical phase II trials. However, the anticancer mechanisms of PGs remain largely unclear. This study was designed to investigate the molecular basis of anticancer activity of UP, a derivative of PGs, in P388 cells. By introducing pharmacological inhibitors and utilizing a variety of analytical approaches including western blotting, flow cytometry and confocal laser microscopy, we found that UP inhibited proliferation of P388 via arresting cells at G2/M phase and inducing cells apoptosis, which was related to the activation of P38, JNK rather than ERK1/2 signaling. ROS regeneration and acidification in cells appear not involved in UP induced apoptosis. Furthermore, utilizing mass spectrometry, sucrose density gradient fractionation and immunofluorescence staining, we discovered that UP was apparently located at ribosome. These results together indicate that ribosome may be the potential target of UP in cancer cells, which opened a new avenue in delineating the anticancer mechanism of PGs.

Molecular interactions of prodiginines with the BH3 domain of anti-apoptotic Bcl-2 family members

Prodigiosin and obatoclax, members of the prodiginines family, are small molecules with anti-cancer properties that are currently under preclinical and clinical trials. The molecular target(s) of these agents, however, is an open question. Combining experimental and computational techniques we find that prodigiosin binds to the BH3 domain in some BCL-2 protein families, which play an important role in the apoptotic programmed cell death. In particular, our results indicate a large affinity of prodigiosin for MCL-1, an anti-apoptotic member of the BCL-2 family. In melanoma cells, we demonstrate that prodigiosin activates the mitochondrial apoptotic pathway by disrupting MCL-1/BAK complexes. Computer simulations with the PELE software allow the description of the induced fit process, obtaining a detailed atomic view of the molecular interactions. These results provide new data to understand the mechanism of action of these molecules, and assist in the development of more specific inhibitors of anti-apoptotic BCL-2 proteins.

Inhibition of Wnt/β-catenin signaling mediates ursolic acid-induced apoptosis in PC-3 prostate cancer cells

BACKGROUND

Ursolic acid, a pentacyclic triterpenoid, is known to exert antitumor activity in breast, lung, liver and colon cancers. Nonetheless, the underlying mechanism of ursolic acid in prostate cancer cells still remains unclear. To investigate the antitumor mechanism, the apoptotic mechanism of ursolic acid via Wnt/β-catenin signaling was examined in PC-3 prostate cancer cells.

METHODS

Cytotoxicity assay, flow cytometry, immunofluorescence assay and western blotting were performed.

RESULTS

Ursolic acid showed cytotoxicity against PC-3, LNCaP and DU145 prostate cancer cells with IC50 of 35 μM, 47 μM and 80 μM, respectively. Also, ursolic acid significantly increased the number of ethidium homodimer stained cells and apoptotic bodies, and dose-dependently enhanced the sub-G1 apoptotic accumulation in PC-3 cells. Consistently, western blotting revealed that ursolic acid effectively cleaved poly (ADP-ribose) polymerase (PARP), activated caspase-9 and -3, suppressed the expression of survival proteins such as Bcl-XL, Bcl-2 and Mcl-1, and upregulated the expression of Bax in PC-3 cells. Interestingly, ursolic acid suppressed the expression of Wnt5α/β and β-catenin, and enhanced the phosphorylation of glycogen synthase kinase 3 β (GSK3β). Furthermore, the GSK3β inhibitor SB216763 or Wnt3a-conditioned medium (Wnt3a-CM) reversed the cleavages of caspase-3 and PARP induced by ursolic acid in PC-3 cells.

CONCLUSIONS

Our findings suggest that ursolic acid induces apoptosis via inhibition of the Wnt5/β-catenin pathway and activation of caspase in PC-3 prostate cancer cells. These results support scientific evidence that medicinal plants containing ursolic acid can be applied to cancer prevention and treatment as a complement and alternative medicine (CAM) agent.

Prodigiosin down-regulates SKP2 to induce p27(KIP1) stabilization and antiproliferation in human lung adenocarcinoma cells

BACKGROUND AND PURPOSE

High levels of SKP2 are a poor prognostic factor in multiple human cancers and mostly correlate with low p27(KIP1) levels. Prodigiosin is a bacterial tripyrrole pigment with strong pro-apoptotic activity. Induction of cell cycle blockade underlies one of its anticancer actions but the mechanisms involved are unclear. The aim of this study was to explore the role of the SKP2-p27(KIP1) axis in prodigiosin's cytostatic effect on human lung adenocarcinoma cells.

EXPERIMENTAL APPROACH

Prodigiosin's effects on cell cycle progression and long-term cell proliferation of human lung adenocarcinoma cells were characterized by flow cytometry and colony formation assay, respectively. Real-time RT-PCR and promoter activity analyses were performed for assessing transcriptional control, while cycloheximide chase analysis evaluated protein stability. Immunoblotting was employed for mechanistic study.

KEY RESULTS

Prodigiosin increased p27(KIP1) expression mainly by stabilizing p27(KIP1) through transcriptional repression of SKP2. Importantly, SKP2 overexpression or p27(KIP1) depletion restored the colony forming capacity of prodigiosin-treated cells. Furthermore, prodigiosin induced PKB dephosphorylation, leading to PKB inhibition as revealed by decreased serine 9 phosphorylation of GSK-3β. Constitutive PKB activation reduced prodigiosin-induced SKP2 repression. Prodigiosin also down-regulated E2F1 (mediates PI3K/PKB-induced SKP2 transcription), but E2F1 overexpression failed to restore SKP2 expression in prodigiosin-treated cells.

CONCLUSIONS AND IMPLICATIONS

Transcriptional repression of SKP2 and the consequent accumulation of p27(KIP1) are essential for prodigiosin's antiproliferative action. Mechanistically, prodigiosin induces PKB inhibition to down-regulate SKP2 in a GSK-3β- and E2F1-independent manner. Our findings further implicate the potential for developing prodigiosin as a novel class of SKP2-targeting anticancer agent.

Inhibition of GSK-3β reverses the pro-apoptotic effect of proadifen (SKF-525A) in HT-29 colon adenocarcinoma cells

Proadifen (SKF-525A) is a well-known inhibitor of cytochrome P450 monooxygenases. Besides the prevention of drug metabolism it affects the proliferation of cancer cells, although the mechanisms of possible anti-cancer activity of proadifen have not been fully understood yet. The aim of this study therefore was to evaluate the potential anti-proliferative effect of proadifen on HT-29 colon cancer cells. Our results show that proadifen inhibited the growth of HT-29 cells by the accumulation of cells in the G1 phase of the cell cycle, reduction of metabolic activity and colony formation and by the induction of apoptosis. Analyses of Western blots and flow cytometry revealed time- and dose-dependent phosphatidylserine externalization, caspase-3 activation and PARP cleavage. Intense upregulation of NAG-1 and ATF3 and downregulation of Mcl-1 and Egr-1 were also observed. Further investigation showed that NAG-1 gene silencing by siRNA had no effect on the pro-apoptotic action of proadifen. In contrast, we found that AR-A014418, the specific inhibitor of glycogen synthase kinase-3 β (GSK-3β), significantly decreased proadifen-induced apoptosis. Inactivation of GSK-3β (phosphorylation at serine 9) resulted in changes in phosphatidylserine externalization and caspase-3 activation. These data suggest that GSK-3β is an important factor in the induction of apoptosis in HT-29 colon cancer cells treated with proadifen.

Ursolic acid from Oldenlandia diffusa induces apoptosis via activation of caspases and phosphorylation of glycogen synthase kinase 3 beta in SK-OV-3 ovarian cancer cells

Although ursolic acid isolated from Oldenlandia diffusa (Rubiaceae) was known to have anticancer activities in prostate, breast and liver cancers, the underlying mechanism of ursolic acid in ovarian cancer cells was not investigated so far. In the present study, the apoptotic mechanism of ursolic acid was elucidated in SK-OV-3 ovarian cancer cells by 2,3-bis(2-methoxy-4-nitro-5-sulphophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay, cell cycle analysis and Western blotting. Ursolic acid exerted cytotoxicity against SK-OV-3 and A2780 ovarian cancer cells with IC₅₀ of ca. 50 and 65 µM, respectively. Apoptotic bodies were observed in ursolic acid treated SK-OV-3 cells. Also, ursolic acid significantly increased ethidium homodimer stained cells and sub-G1 apoptotic portion in SK-OV-3 cells. Consistently, Western blotting revealed that ursolic acid effectively cleaved poly(ADP-ribose) polymerase (PARP), caspase-9 and -3, suppressed the expression of survival genes such as c-Myc, Bcl-x(L) and astrocyte elevated gene (AEG)-1, and upregulated phosphorylation of extracellular signal-regulated kinase (ERK) in SK-OV-3 cells. Interestingly, ursolic acid suppressed β-catenin degradation as well as enhanced phosphorylation of glycogen synthase kinase 3 beta (GSK 3β). Furthermore, GSK 3β inhibitor SB216763 blocked the cleavages of caspase-3 and PARP induced by ursolic acid and proteosomal inhibitor MG132 disturbed down-regulation of β-catenin, activation of caspase-3 and decreased mitochondrial membrane potential (MMP) induced by ursolic acid in SK-OV-3 cells. Overall, our findings suggest that ursolic acid induces apoptosis via activation of caspase and phosphorylation of GSK 3β in SK-OV-3 cancer cells as a potent anti-cancer agent for ovarian cancer therapy.

The TGF-β superfamily cytokine, MIC-1/GDF15: a pleotrophic cytokine with roles in inflammation, cancer and metabolism

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) is associated with cardiovascular disease, inflammation, body weight regulation and cancer. Its serum levels facilitate the diagnosis and prognosis of cancer and vascular disease. Furthermore, its serum levels are a powerful predictor of all-cause mortality, suggesting a fundamental role in biological processes associated with ageing. In cancer, the data available suggest that MIC-1/GDF15 is antitumorigenic, but this may not always be the case as disease progresses. Cancer promoting effects of MIC-1/GDF15 may be due, in part, to effects on antitumour immunity. This is suggested by the anti-inflammatory and immunosuppressive properties of MIC-1/GDF15 in animal models of atherosclerosis and rheumatoid arthritis. Furthermore, in late-stage cancer, large amounts of MIC-1/GDF15 in the circulation suppress appetite and mediate cancer anorexia/cachexia, which can be reversed by monoclonal antibodies in animals. Available data suggest MIC-1/GDF15 may be an important molecule mediating the interplay between cancer, obesity and chronic inflammation.

Prodigiosin produced by Serratia marcescens NMCC46 as a mosquito larvicidal agent against Aedes aegypti and Anopheles stephensi

Microbial control agents offer alternatives to chemical pest control as they can be more selective than chemical insecticides. The present study evaluates the mosquito larvicidal potential of microbial pigment prodigiosin produced by Serratia marcescens NMCC46 against Aedes aegypti and Anopheles stephensi. The pigment of S. marcescens NMCC46 was extracted after 24 h from mannitol containing nutrient broth media. The effects of crude extracted pigment on the growth, survival, development, and other life cycle aspects were studied. The LC(50) and LC(90) values of second, third, and fourth instars of A. aegypti (LC(50) = 41.65, 139.51, 103.95; LC(90) = 117.81, 213.68, 367.82) and A. stephensi (LC(50) = 51.12, 105.52, 133.07; LC(90) = 134.81, 204.45, 285.35) were determined. At higher concentration (500 ppm), mortality starts within first 6 h of exposure. More than 50% mortality occurs within the first 24 h. The overall observed effects against A. aegypti and A. stephensi larvae after 48 h were increasing percent survival larvae, survival pupation, adult emergence with decreasing crude pigment extract concentration. These ensure that the resultant mosquito population reduction is substantial even where the larvicidal potential is minimal. The UV (λ (max) = 536 nm), TLC (Rf = 0.9), HPLC, and FTIR analysis of crude pigment shows the presence of prodigiosin as active compound. Thus, the active compound produced by this species would be more useful against vectors responsible for diseases of public health importance. This is the first report on mosquito larvicidal activity of prodigiosin produced by Serratia species.

Development of natural anti-tumor drugs by microorganisms

Discoveries of tumor-resistant pharmacological drugs have mainly resulted from screening of natural products and their analogs. Some are also discovered incidentally when studying organisms. The great biodiversity of microorganisms raises the possibility of producing secondary metabolites (e.g., mevastatin, lovastatin, epothilone, salinosporamide A) to cope with adverse environments. Recently, natural plant pigments with anti-tumor activities such as β-carotene, lycopene, curcumin and anthocyanins have been proposed. However, many plants have a long life cycle. Therefore, pigments from microorganisms represent another option for the development of novel anti-tumor drugs. Prodigiosin (PG) is a natural red pigment produced by microorganisms, i.e., Serratia marcescens and other gram-negative bacteria. The anti-tumor potential of PG has been widely demonstrated. The families of PG (PGs), which share a common pyrrolylpyrromethene (PPM) skeleton, are produced by various bacteria. PGs are bioactive pigments and are known to exert immunosuppressive properties, in vitro apoptotic effects, and in vivo anti-tumor activities. Currently the most common strain used for producing PGs is S. marcescens. However, few reports have discussed PGs production. This review therefore describes the development of an anti-tumor drug, PG, that can be naturally produced by microorganisms, and evaluates the microbial production system, fermentation strategies, purification and identification processes. The application potential of PGs is also discussed.

Apoptosis of human lung adenocarcinoma A549 cells induced by prodigiosin analogue obtained from an entomopathogenic bacterium Serratia marcescens

An entomopathogenic bacterial strain SCQ1 was isolated from silkworm (Bombyx mori) and identified as Serratia marcescens via 16S rRNA gene analysis. This strain produces a red pigment that causes acute septicemia of silkworm. The red pigment of strain SCQ1 was identified as prodigiosin analogue (PGA) with various reported biological activities. In this study, we found that low concentration of PGA showed significant anticancer activity in human lung adenocarcinoma A549 cells, but has little effect in human bone marrow stem cells, in vitro. By exposure to different concentrations of PGA for 24 h, morphological changes and the MTT assay showed that A549 cell line was very sensitive to PGA, with IC(50) value about 2.2 mg/L. Early stage of apoptosis was detected by flow cytometry while A549 cells were treated with PGA for 4 and 12 h, respectively. The proportion of dead cells was increased with treatment time or the concentrations of PGA, but it was inversely proportional to that of apoptotic cells. These results indicate that PGA obtained from strain SCQ1 induces apoptosis in A549 cells, but the molecular mechanisms of cell death are complicated, and the S. marcescens strain SCQ1 may serve as a source of the anticancer compound, PGA.

Constitutive activation of glycogen synthase kinase-3beta correlates with better prognosis and cyclin-dependent kinase inhibitors in human gastric cancer

Background

Aberrant regulation of glycogen synthase kinase-3β (GSK-3β) has been implicated in several human cancers; however, it has not been reported in the gastric cancer tissues to date. The present study was performed to determine the expression status of active form of GSK-3β phosphorylated at Tyr²¹⁶ (pGSK-3β) and its relationship with other tumor-associated proteins in human gastric cancers.

Methods

Immunohistochemistry was performed on tissue array slides containing 281 human gastric carcinoma specimens. In addition, gastric cancer cells were cultured and treated with a GSK-3β inhibitor lithium chloride (LiCl) for immunoblot analysis.

Results

We found that pGSK-3β was expressed in 129 (46%) of 281 cases examined, and was higher in the early-stages of pathologic tumor-node-metastasis (P < 0.001). The expression of pGSK-3β inversely correlated with lymphatic invasion (P < 0.001) and lymph node metastasis (P < 0.001) and correlated with a longer patient survival (P < 0.001). In addition, pGSK-3β expression positively correlated with that of p16, p21, p27, p53, APC, PTEN, MGMT, SMAD4, or KAI1 (P < 0.05), but not with that of cyclin D1. This was confirmed by immunoblot analysis using SNU-668 gastric cancer cells treated with LiCl.

Conclusions

GSK-3β activation was frequently observed in early-stage gastric carcinoma and was significantly correlated with better prognosis. Thus, these findings suggest that GSK-3β activation is a useful prognostic marker for the early-stage gastric cancer.

Prostate-derived factor--a novel inhibitor of drug-induced cell death in colon cancer cells

We investigated the role of the divergent transforming growth factor-beta superfamily member, prostate-derived factor (PDF), in regulating response to chemotherapies used in the treatment of colorectal cancer. A clear p53-dependent expression pattern of PDF was shown in a panel of colorectal cancer cell lines following acute exposure to oxaliplatin, 5-fluorouracil, and SN38. PDF gene silencing before chemotherapy treatment significantly sensitized cells expressing wild-type p53, but not p53-null or p53-mutant cells, to drug-induced apoptosis. Similarly, knockdown of PDF expression sensitized HCT116 drug-resistant daughter cell lines to their respective chemotherapies. Inducible PDF expression and treatment with recombinant PDF both significantly attenuated drug-induced apoptosis. Further analysis revealed that PDF activated the Akt but not the extracellular signal-regulated kinase 1/2 signaling pathway. Furthermore, cotreatment with the phosphatidylinositol 3-kinase inhibitor wortmannin abrogated PDF-mediated resistance to chemotherapy-induced apoptosis. Together, these data suggest that PDF may be a novel inhibitor of drug-induced cell death in colorectal cancer cells and that the mature secreted form of the protein activates the phosphatidylinositol 3-kinase/Akt pathway as an acute mechanism of chemoresistance.

A novel anticancer effect of Astragalus saponins: Transcriptional activation of NSAID-activated gene

Astragalus membranaceus has been used to ameliorate the side effects of antineoplastic drugs because of its immunomodulating nature. We had recently demonstrated that total Astragalus saponins (AST) possess anticarcinogenic and proapoptotic properties in human colon cancer cells and tumor xenograft. In this study, we identified NSAID-activated gene (NAG-1) as a potential molecular target of AST. The growth-inhibitory and proapoptotic effects of AST were assessed in a panel of human cancer cell lines. Hoechst 33342 nuclear staining, Annexin V-FITC/propidium iodide staining, Western immunoblotting, real-time PCR, luciferase reporter assay and electrophoretic mobility shift assay were conducted to determine the association of NAG-1 and related transcription factors with AST during its regulation of apoptotic activities. Moreover, the combined proapoptotic and NAG-1 promoting activities of AST and/or inhibitors of the PI3K-Akt pathway were also examined. AST caused overexpression of NAG-1, leading to PARP cleavage and apoptosis. The induction of NAG-1 promoter activity by the drug was associated with increased gene expression, in addition to prior increase in Egr-1 expression and DNA binding activity. AST-induced NAG-1 activation was intensified when PI3K inhibitor LY294002 or Akt inhibitor was co-treated and reversed by NAG-1 siRNA transfection. Nevertheless, the extent of NAG-1 induction could not be altered by the ERK inhibitor PD98059. Our results indicate that NAG-1 is a potential molecular target of AST in its antitumorigenic and proapoptotic actions, which would have additive effects when used along with PI3K-Akt inhibitors. The information obtained could facilitate future development of a novel target-specific chemotherapeutic agent with known molecular pathway.

Induction of apoptosis and nonsteroidal anti-inflammatory drug-activated gene 1 in pancreatic cancer cells by a glycyrrhetinic acid derivative

Methyl 2-cyano-3,11-dioxo-18beta-olean-1,12-dien-30-oate (CDODA-Me) is a synthetic triterpenoid derived from glycyrrhetinic acid, a bioactive phytochemical in licorice, CDODA-Me inhibits growth of Panc1 and Panc28 pancreatic cancer cell lines and activates peroxisome proliferator-activated receptor gamma (PPARgamma)-dependent transactivation in these cells. CDODA-Me also induced p21 and p27 protein expression and downregulates cyclin D1; however, these responses were receptor-independent. CDODA-Me induced apoptosis in Panc1 and Panc28 cells, and this was accompanied by receptor-independent induction of the proapoptotic proteins early growth response-1 (Egr-1), nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), and activating transcription factor-3 (ATF3). Induction of NAG-1 and Egr-1 by CDODA-Me was dependent on activation of phosphatidylinositol-3-kinase (PI3-K) and/or p42 and p38 mitogen-activated protein kinase (MAPK) pathways but there were differences between Panc28 and Panc1 cells. Induction of NAG-1 in Panc28 cells was p38-MAPK- and PI3-K-dependent but Egr-1-independent, whereas induction in Panc1 cells was associated with activation of p38-MAPK, PI3-K, and p42-MAPK and was only partially Egr-1-dependent. This is the first report of the induction of the proapoptotic protein NAG-1 in pancreatic cancer cells.

Prodigiosin down-regulates survivin to facilitate paclitaxel sensitization in human breast carcinoma cell lines

Prodigiosin is a bacterial metabolite with potent anticancer activity, which is attributed to its proapoptotic effect selectively active in malignant cells. Still, the molecular mechanisms whereby prodigiosin induces apoptosis remain largely unknown. In particular, the role of survivin, a vital inhibitor of apoptosis, in prodigiosin-induced apoptosis has never been addressed before and hence was the primary goal of this study. Our results showed that prodigiosin dose-dependently induced down-regulation of survivin in multiple breast carcinoma cell lines, including MCF-7, T-47D and MDA-MB-231. This down-regulation is mainly regulated at the level of transcription, as prodigiosin reduced the levels of both survivin mRNA and survivin promoter activity but failed to rescue survivin expression when proteasome-mediated degradation is abolished. Importantly, overexpression of survivin rendered cells more resistant to prodigiosin, indicating an essential role of survivin down-regulation in prodigiosin-induced apoptosis. In addition, we found that prodigiosin synergistically enhanced cell death induced by paclitaxel, a chemotherapy drug known to up-regulate survivin that in turn confers its own resistance. This paclitaxel sensitization effect of prodigiosin is ascribed to the lowering of survivin expression, because prodigiosin was shown to counteract survivin induction by paclitaxel and, notably, the sensitization effect was severely abrogated in cells that overexpress survivin. Taken together, our results argue that down-regulation of survivin is an integral component mediating prodigiosin-induced apoptosis in human breast cancer cells, and further suggest the potential of prodigiosin to sensitize anticancer drugs, including paclitaxel, in the treatment of breast cancer.

p53 controls prostate-derived factor/macrophage inhibitory cytokine/NSAID-activated gene expression in response to cell density, DNA damage and hypoxia through diverse mechanisms

The p53 tumor suppressor modulates cellular response to stress through both transcriptional and post-transcriptional mechanisms. Elucidation of the downstream targets of p53 following cell stress will aid in our understanding of the pathways involved in cellular adaptation to stressful stimuli. Here, we demonstrate that the TGF-beta superfamily member, and putative tumor suppressor, prostate-derived factor (PDF)/NSAID-activated gene (NAG)-1/macrophage inhibitory cytokine (MIC)-1 is induced in LNCaP human prostate cancer cells following treatment with the DNA-damaging agent, doxorubicin, culture under hypoxic conditions and by the hypoxia mimetic, cobalt chloride. Additionally, PDF expression was induced by increasing cell density. Expression of dominant negative p53 in LNCaP cells blocked induction of PDF mRNA and protein demonstrating the requirement for functional p53 in PDF induction by these stimuli. DNA damage and hypoxia resulted in increased p53 protein accumulation indicating that PDF expression may be controlled by cellular levels of p53. We also show the requirement for de novo protein synthesis in PDF induction by hypoxia and DNA damage. Increased PDF mRNA stability in response to hypoxia and cobalt chloride, but not doxorubicin, indicates that p53-dependent induction of PDF expression occurs via diverse mechanisms. Thus, PDF may represent a novel target of p53 in response to cell stress.

Glycogen synthase kinase 3beta (GSK3beta) in tumorigenesis and cancer chemotherapy

Glycogen synthase kinase 3beta (GSK3beta), a multifunctional serine/threonine kinase found in all eukaryotes, had been initially identified as a key regulator of insulin-dependent glycogen synthesis. It is now known that GSK3beta functions in diverse cellular processes including proliferation, differentiation, motility and survival. Aberrant regulation of GSK3beta has been implicated in a range of human pathologies including non-insulin-dependent diabetes mellitus, cardiovascular disease, some neurodegenerative diseases, and bipolar disorder. As a consequence, the therapeutic potential of GSK3beta inhibitors has become an important area of investigation. However, GSK3beta also participates in neoplastic transformation and tumor development. The role of GSK3beta in tumorigenesis and cancer progression remains controversial; it may function as a "tumor suppressor" for certain types of tumors, but promotes growth and development for some others. GSK3beta also mediates drug sensitivity/resistance in cancer chemotherapy. Therefore, although GSK3beta is an attractive therapeutic target for a number of human diseases, its potential impact on tumorigenesis and cancer chemotherapy needs to be carefully evaluated. This mini-review discusses the role of GSK3beta in tumorigenesis/cancer progression as well as its modulation of cancer chemotherapy.

Anticancer and immunosuppressive properties of bacterial prodiginines

Bacterial prodiginines are a family of red-pigmented, tripyrrolic compounds that display numerous biological activities, including antibacterial, antifungal, antiprotozoal, antimalarial, immunosuppressive and anticancer properties. Recently, significant progress has been made in understanding the biosynthesis and regulation of bacterial prodiginines. An understanding of the biosynthesis of prodiginines will allow engineering of bacterial strains capable of synthesizing novel prodiginines through rational design and mutasynthesis experiments. Bacterial prodiginines and synthetic derivatives are effective proapoptotic agents with multiple cellular targets, and they are active against numerous cancer cell lines, including multidrug-resistant cells, with little or no toxicity towards normal cell lines. A synthetic derivative, GX15-070 (Obatoclax), developed through structure-activity relationship studies of the pyrrolic ring A of GX15, is in multiple Phase I and II clinical trials in both single and dual-agent studies to treat different types of cancer. Therefore, prodiginines have real therapeutic potential in the clinic.

The anticancer agent prodigiosin induces p21WAF1/CIP1 expression via transforming growth factor-beta receptor pathway

The anticancer agent prodigiosin has been shown to act as an efficient immunosuppressant, eliciting cell cycle arrest at non-cytotoxic concentrations, and potent proapoptotic and antimetastatic effects at higher concentrations. Gene expression profiling of MCF-7 cells after treatment with a non-cytotoxic concentration of prodigiosin showed that expression of the p21WAF1/CIP1 gene, a negative cell cycle regulator was induced. In this study, we show that prodigiosin induces p21 expression leading to cell cycle blockade. Subsequently, we attempted to elucidate the molecular mechanisms involved in prodigiosin-mediated p21 gene expression. We demonstrate that prodigiosin induces p21 in a p53-independent manner as prodigiosin induced p21 in cells with both mutated and dominant negative p53. Conversely, the transforming growth factor-beta (TGF-beta) pathway has been found to be necessary for p21 induction. Prodigiosin-mediated p21 expression was blocked by SB431542, a TGF-beta receptor inhibitor. Nevertheless, this pathway alone is not enough to induce p21 expression. The TGF-beta family member (nonsteroidal anti-inflammatory drug)-activated gene 1/growth differentiation factor 15 (NAG-1) may activate this pathway, as it has previously been suggested to signal through the TGF-beta pathway and is overexpressed in response to prodigiosin treatment. We show that NAG-1 colocalizes with TGF-beta receptor type I, suggesting a possible interaction between them. Taken together, these results suggest the TGF-beta pathway is required for induction of p21 expression after prodigiosin treatment of MCF-7 cells.