Plumbagin inhibits cell proliferation and promotes apoptosis in multiple myeloma cells through inhibition of the PI3K/Akt-mTOR pathway

Huangqin tang alleviates colitis-associated colorectal cancer via amino acids homeostasisand PI3K/AKT/mtor pathway modulation

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqin Tang (HQT), a traditional Chinese medicine formula, is commonly used in clinical practice for the treatment of inflammatory bowel diseases. It has been reported that HQT exerts antitumor effects on colitis-associated colorectal cancer (CAC). However, the mechanism by which HQT interferes with the inflammation-to-cancer transformation remains unclear.

AIMS OF THE STUDY

The purpose of this study was to dynamically evaluate the efficacy of HQT in alleviating or delaying CAC and to reveal the underlying mechanism.

METHODS

We established a mouse model of CAC using azoxymethane combined with 1.5% dextran sodium sulphate. The efficacy of HQT was evaluated based on pathological sections and serum biochemical indices. Subsequently, amino acids (AAs) metabolism analyses were performed using ultra-performance liquid chromatography-tandem mass spectrometry, and the phosphatidylinositol 3 kinase/protein kinase B/mechanistic target of rapamycin (PI3K/AKT/mTOR) pathway was detected by western blotting.

RESULTS

The data demonstrated that HQT could alleviate the development of CAC in the animal model. HQT effectively reduced the inflammatory response, particularly interleukin-6 (IL-6), in the inflammation induction stage, as well as in the stages of proliferation initiation and tumorigenesis. During the proliferation initiation and tumorigenesis stages, immunohistochemistry staining showed that the expression of the proliferation marker Ki67 was reduced, while apoptosis was increased in the HQT group. Accordingly, HQT substantially decreased the levels of specific AAs in the colon with CAC, including glutamic acid, glutamine, arginine, and isoleucine. Furthermore, HQT significantly inhibited the activated PI3K/AKT/mTOR pathway, which may contribute to suppression of cell proliferation and enhancement of apoptosis.

CONCLUSION

HQT is effective in alleviating and delaying the colon "inflammation-to-cancer". The mechanism of action may involve HQT maintained AAs metabolism homeostasis and regulated PI3K/AKT/mTOR pathway, so as to maintain the balance between proliferation and apoptosis, and then interfere in the occurrence and development of CAC.

Natural products modulate NLRP3 in ulcerative colitis

Ulcerative colitis (UC) is a clinically common, progressive, devastating, chronic inflammatory disease of the intestine that is recurrent and difficult to treat. Nod-like receptor protein 3 (NLRP3) is a protein complex composed of multiple proteins whose formation activates cysteine aspartate protease-1 (caspase-1) to induce the maturation and secretion of inflammatory mediators such as interleukin (IL)-1β and IL-18, promoting the development of inflammatory responses. Recent studies have shown that NLRP3 is associated with UC susceptibility, and that it maintains a stable intestinal environment by responding to a wide range of pathogenic microorganisms. The mainstay of treatment for UC is to control inflammation and relieve symptoms. Despite a certain curative effect, there are problems such as easy recurrence after drug withdrawal and many side effects associated with long-term medication. NLRP3 serves as a core link in the inflammatory response. If the relationship between NLRP3 and gut microbes and inflammation-associated factors can be analyzed concerning its related inflammatory signaling pathways, its expression status as well as specific mechanism in the course of IBD can be elucidated and further considered for clinical diagnosis and treatment of IBD, it is expected that the development of lead compounds targeting the NLRP3 inflammasome can be developed for the treatment of IBD. Research into the prevention and treatment of UC, which has become a hotbed of research in recent years, has shown that natural products are rich in therapeutic means, and multi-targets, with fewer adverse effects. Natural products have shown promise in treating UC in numerous basic and clinical trials over the past few years. This paper describes the regulatory role of the NLRP3 inflammasome in UC and the mechanism of recent natural products targeting NLRP3 against UC, which provides a reference for the clinical treatment of this disease.

Current Advances in Cellular Approaches for Pathophysiology and Treatment of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a prevalent gynecological and endocrine disorder that results in irregular menstruation, incomplete follicular development, disrupted ovulation, and reduced fertility rates among affected women of reproductive age. While these symptoms can be managed through appropriate medication and lifestyle interventions, both etiology and treatment options remain limited. Here we provide a comprehensive overview of the latest advancements in cellular approaches utilized for investigating the pathophysiology of PCOS through in vitro cell models, to avoid the confounding systemic effects such as in vitro fertilization (IVF) therapy. The primary objective is to enhance the understanding of abnormalities in PCOS-associated folliculogenesis, particularly focusing on the aberrant roles of granulosa cells and other relevant cell types. Furthermore, this article encompasses analyses of the mechanisms and signaling pathways, microRNA expression and target genes altered in PCOS, and explores the pharmacological approaches considered as potential treatments. By summarizing the aforementioned key findings, this article not only allows us to appreciate the value of using in vitro cell models, but also provides guidance for selecting suitable research models to facilitate the identification of potential treatments and understand the pathophysiology of PCOS at the cellular level.

Plumbagin Suppresses Breast Cancer Progression by Downregulating HIF-1α Expression via a PI3K/Akt/mTOR Independent Pathway under Hypoxic Condition

Hypoxia-inducible factor-1α (HIF-1α) is a major transcriptional regulator that plays a crucial role in the hypoxic response of rapidly growing tumors. Overexpression of HIF-1α has been associated with breast cancer metastasis and poor clinical prognosis. Plumbagin, the main phytochemical from Plumbago indica, exerts anticancer effects via multiple mechanisms. However, its precise mechanisms on breast cancer cells under hypoxic conditions has never been investigated. This study aims to examine the anticancer effect of plumbagin on MCF-7 cell viability, transcriptional activity, and protein expression of HIF-1α under normoxia and hypoxia-mimicking conditions, as well as reveal the underlying signaling pathways. The results demonstrate that plumbagin decreased MCF-7 cell viability under normoxic conditions, and a greater extent of reduction was observed upon exposure to hypoxic conditions induced by cobalt chloride (CoCl₂). Mechanistically, MCF-7 cells upregulated the expression of HIF-1α protein, mRNA, and the VEGF target gene under CoCl₂-induced hypoxia, which were abolished by plumbagin treatment. In addition, inhibition of HIF-1α and its downstream targets did not affect the signaling transduction of the PI3K/Akt/mTOR pathway under hypoxic state. This study provides mechanistic insight into the anticancer activity of plumbagin in breast cancer cells under hypoxic conditions by abolishing HIF-1α at transcription and post-translational modifications.

Resibufogenin inhibits the malignant characteristics of multiple myeloma cells by blocking the PI3K/Akt signaling pathway

Resibufogenin (RBG) is an active ingredient of toad venom that also has antitumor potential. The present study aimed to investigate the role of RBG in multiple myeloma (MM) and the underlying action mechanism involving the PI3K/Akt signaling pathway. A human MM cell line, RPMI8226, was treated with RBG and/or insulin-like growth factor 1 (IGF-1; an activator of the PI3K/AKT signaling pathway). Cell viability and apoptosis were detected using Cell Counting Kit-8 and flow cytometry, respectively. Cell migration and invasion were detected using a Transwell assay. In addition, the epithelial-mesenchymal transition (EMT)-associated proteins (E-cadherin, N-cadherin and Vimentin) and the PI3K/AKT pathway-associated proteins [AKT, phosphorylated (p)-AKT, PI3K and p-PI3K] were measured using western blotting. RBG inhibited the viability, migration and invasion, and promoted the apoptosis of RPMI8226 cells in a dose-dependent manner. RBG at concentrations of 4 and 8 µM upregulated E-cadherin, and downregulated N-cadherin and Vimentin in RPMI8226 cells. RBG also decreased the protein expression of p-AKT and p-PI3K in a dose-dependent manner. In addition, the intervention of IGF-1 weakened the inhibitory effects of RBG on the malignant characteristics of MM cells. RBG-induced inhibition of EMT and the PI3K/AKT pathway were also weakened by IGF-1 treatment. In conclusion, RBG inhibited viability, migration, invasion and EMT, and promoted the apoptosis of MM cells by blocking the PI3K/AKT signaling pathway.

Phosphatidylinositol 3-kinase signaling inhibitors for treatment of multiple myeloma: From small molecules to microRNAs

Multiple myeloma is one of the most hard-to-treat cancers among blood malignancies due to the high rate of drug resistance and relapse. The researchers are trying to find more effective drugs for treatment of the disease. Hence, the use of drugs targeting signaling pathways has become a powerful weapon. Overactivation of phosphatidylinositol 3-kinase signaling pathways is frequently observed in multiple myeloma cancer cells, which increases survival, proliferation, and even drug resistance in such cells. In recent years, drugs that inhibit the mediators involved in this biological pathway have shown promising results in the treatment of multiple myeloma. In the present study, we aimed to introduce phosphatidylinositol 3-kinase signaling inhibitors which include small molecules, herbal compounds, and microRNAs.

Plumbagin attenuates traumatic tracheal stenosis in rats and inhibits lung fibroblast proliferation and differentiation via TGF-β1/Smad and Akt/mTOR pathways

Traumatic tracheal stenosis (TS) is a serious respiratory disease characterized by hyperplasia of airway granulation. Plumbagin (PLB) is a natural naphthoquinone component with anti-fibrotic properties. This research aimed to explore the roles of PLB in alleviating TS and the underlying mechanisms. For in vitro studies, lung fibroblasts (IMR-90 cells), with/without PLB treatment or TGF-β1 induction, were used. The viability and proliferation of IMR-90 cells were examined by CCK-8 and EdU incorporation assays. The differentiation of IMR-90 cells was assessed by detecting the mRNA and protein expression levels of collagen (COL)-1 and alpha-smooth muscle actin (α-SMA). Besides, immunofluorescence assay was conducted to evaluate the localization of α-SMA in TGF-β1-induced IMR-90 cells. Moreover, the combination of PLB with/without TβRI (SB-431,542), PI3K/Akt (Ly294002) or mTOR (rapamycin) inhibitor was pretreated on IMR-90 cells after TGF-β1 induction. For in vivo studies, a rat model of TS was established. The pathological features and severity of TS were determined by hematoxylin and eosin staining. The protein levels of TGF-β1/Smad and Akt/mTOR pathways were detected for both in vitro and in vivo models. PLB effectively inhibited the proliferation and differentiation of TGF-β1-induced IMR-90 cells, and suppressed TGF-β1/Smad and Akt/mTOR signaling pathways both in vivo and in vitro. Furthermore, PLB reduced the degree of TS in rats. Taken together, our results indicate that PLB regulates lung fibroblast activity and attenuates TS in rats by inhibiting TGF-β1/Smad and Akt/mTOR signaling pathways. In conclusion, this study implies that PLB may serve as a promising therapeutic compound for TS.

Plumbagin inhibits proliferation and promotes apoptosis of ovarian granulosa cells in polycystic ovary syndrome by inactivating PI3K/Akt/mTOR pathway

Polycystic ovary syndrome (PCOS) is recognized as a general endocrine disease and reproductive disorder. Although evidence indicates that PCOS has a complex etiology and genetic basis, the pathogenic mechanisms and signal pathway in PCOS remain unclear. In this study, the normal structure of follicle and corpus luteum were observed, and no cyst nor hyperemia was observed under the light microscopic study with hematoxylin and eosin (H&E) staining. Eestosterone and progesterone were evaluated by radioimmunoassay in rat serum. The alterations of proliferative ability and cell cycle distribution of each group were assessed by Cell Counting Kit-8 (CCK8) assay and flow cytometry. The protein expression of p-mTOR/mTOR, p-PI3K/PI3K, p-AKT/AKT, and GAPDH were analyzed by western blotting. Both doses of PLB could benefit the ovarian morphology and polycystic property. PLBinduced a suppress effect on the proliferation of rat ovarian granulosa cells. In addition, PLB also induced concentration-dependent apoptosis in rat ovarian granulosa cells. The rat ovarian granulosa cells treated with PLB that the expression levels of p-AKT, p-mTOR, and p-PI3K were significantly decreased in a concentration-dependent manner. PLB not only plays a critical role in attenuating the pathology and polycystic property changes in the ovary but can also induce rat ovarian granulosa cell apoptosis through the PI3K/Akt/mTOR signal pathway. This study showed the innovative role of PLB in the pathogenesis of PCOS and provides a new therapeutic modality for the treatment of PCOS.

Cytokine-Mediated Dysregulation of Signaling Pathways in the Pathogenesis of Multiple Myeloma

Multiple myeloma (MM) is a hematologic disorder of B lymphocytes characterized by the accumulation of malignant plasma cells (PCs) in the bone marrow. The altered plasma cells overproduce abnormal monoclonal immunoglobulins and also stimulate osteoclasts. The host’s immune system and microenvironment are of paramount importance in the growth of PCs and, thus, in the pathogenesis of the disease. The interaction of MM cells with the bone marrow (BM) microenvironment through soluble factors and cell adhesion molecules causes pathogenesis of the disease through activation of multiple signaling pathways, including NF-κβ, PI3K/AKT and JAK/STAT. These activated pathways play a critical role in the inhibition of apoptosis, sustained proliferation, survival and migration of MM cells. Besides, these pathways also participate in developing resistance against the chemotherapeutic drugs in MM. The imbalance between inflammatory and anti-inflammatory cytokines in MM leads to an increased level of pro-inflammatory cytokines, which in turn play a significant role in dysregulation of signaling pathways and proliferation of MM cells; however, the association appears to be inadequate and needs more research. In this review, we are highlighting the recent findings on the roles of various cytokines and growth factors in the pathogenesis of MM and the potential therapeutic utility of aberrantly activated signaling pathways to manage the MM disease.

Plumbagin Prevents Secretory Diarrhea by Inhibiting CaCC and CFTR Channel Activities

Secretory diarrhea, which primarily originates through intestinal pathogens and viruses, is a health burden in many regions worldwide. Enterocyte Cl⁻ channels, as the final step in enterotoxin-induced fluid secretion, constitute an attractive class of targets for diarrhea therapy. Chloride channel inhibitors have become a new class of candidates for antisecretion and anti-intestinal motility agents. In the present study, we identified plumbagin as a transmembrane protein 16A (TMEM16A) inhibitor in a cell-based fluorescence-quenching assay, and the IC₅₀ value was ∼12.46 µM. Short-circuit current measurements showed that plumbagin reversibly inhibited the E_act-induced Cl⁻ current on the apical side of TMEM16A-transfected Fischer rat thyroid (FRT) cells with no significant effect on cytoplasmic Ca²⁺ signaling. Notably, plumbagin also inhibited the activity of intestinal epithelial calcium-activated chloride channel (CaCC) and cystic fibrosis transmembrane conductance regulator (CFTR) in both HT-29 cells and mouse colons, but had no effects on the activity of the Na⁺-K⁺ ATPase or K⁺ channels. In in vivo experiments, the administration of plumbagin reduced both Escherichia coli heat-stable enterotoxin (STa)- and cholera toxin (CT)-induced intestinal fluid secretion. In neonatal mouse models of CT- and rotavirus infection-induced diarrhea, 0.4 µg plumbagin inhibited secretory diarrhea by >40% and 50%, respectively, without affecting intestinal epithelial integrity or the rotaviral infection. In addition, plumbagin exerted inhibitory effects on the vasoactive intestinal peptide (VIP)-, prostaglandin E2 (PGE2)-, and 5-hydroxytryptamine (5-HT)-stimulated Cl⁻ currents. In the evaluations of intestinal motility, plumbagin significantly delayed intestinal motility and inhibited intestinal smooth muscle contractility without an evident impact on contractive frequency. Collectively, our results indicate that plumbagin inhibits both Ca²⁺- and cAMP-activated Cl⁻ channels, accounting for the mechanisms of plumbagin inhibition of chloride secretion and intestinal motility. Thus, plumbagin can be a lead compound in the treatment of CT-induced, Traveler’s, and rotaviral diarrhea, as well as other types of secretory diarrhea that result from excessive intestinal fluid secretion and increased intestinal peristalsis.

Bioinformatic and experimental data decipher the pharmacological targets and mechanisms of plumbagin against hepatocellular carcinoma

OBJECTIVE

Plumbagin exerts effective anti-hepatocellular carcinoma (HCC) benefits, however, the detailed mechanisms behind these effects are not yet completely elucidated. The pharmacological targets and molecular mechanisms of plumbagin against HCC were revealed through conducting network pharmacology approach before experimentative verification.

METHODS

The web-accessible databases of herbal ingredients' targets (HIT), Swiss-Target-Prediction and Super-Pred were used to predict the therapeutic targets of plumbagin, followed by combined with pathogenic targets of HCC from oncogenomic database of hepatocellular carcinoma (OncoDB.HCC) and Liverome databases to obtain the predominant targets of plumbagin-treating HCC. The database for annotation, visualization and integrated discovery (DAVID) was applied to output the gene ontology (GO) annotation and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment by use of all predominant targets for computerized visualization. The validated data of human and cell culture were subjected to a group of medical imaging, biochemical tests and immunostaining, respectively.

RESULTS

As revealed in bioinformatic data, 19 predominant targets of plumbagin-treating HCC were obtained, and 5 top targets of TP53, MAPK1, MAP2K1, RAF1 and CCND1 were the most important biomolecules in anti-HCC effects exerted by plumbagin. Other identifiable 102 GO items were showed, including 66 biological processes, and 12 cellular components, 24 molecular functions. And 67 KEGG pathways were mainly involved in neoplastic signaling. In human data, HCC sections showed increased expressions of hepatocellular TP53, MAPK1, accompanied with positive clinical imaging results for HCC. In plumbagin-treated HepG2 cells, reduced TP53, MAPK1 protein expressions were observed, accompanied with cell arrest and apoptosis.

CONCLUSION

Collectively, the pharmacological targets and mechanisms of plumbagin-treating HCC were predicted and integrated through the method of network pharmacology, followed by some investigative validations. Interestingly, these 5 predominant biomolecules may be the potential targets for screening and treating HCC.

The PI3K/AKT signaling pathway regulates ABCG2 expression and confers resistance to chemotherapy in human multiple myeloma

Side population (SP) cells are involved in the development of multidrug resistance (MDR) in human multiple myeloma (MM), due to their cancer stem cell (CSC)‑like phenotypes. ATP‑binding cassette (ABC) drug transporter proteins have been reported to be closely associated with MDR in leukemia; however, the correlation between ABC proteins and the progression of MM remains unclear. The present study used MM cell lines and clinical samples to determine the role of ABC subfamily G member 2 (ABCG2) in MM via flow cytometry, reverse transcription‑quantitative polymerase chain reaction and western blotting. SP cells sorted from MM cell lines, including NCI‑H929 cells, via fluorescence‑activated cell sorting, exhibited CSC‑like phenotypes and expressed high levels of ABCG2. Expression of ABCG2 and activation of the phosphatidylinositol 3‑kinase (PI3K)/AKT serine/threonine kinase (AKT) signaling pathway was positively associated with the proportion of SP cells in the NCI‑H929 cell line. In addition, suppression of the PI3K/AKT pathway using LY294002 or rapamycin counteracted the protective effects of ABCG2 against chemotherapeutic drug treatment. Mechanistically, PI3K/AKT signaling may regulate ABCG2 expression, and ABCG2 may regulate phosphatase and tensin homolog expression via a potential negative feedback loop. Furthermore, SP cell proportion, ABCG2 expression and PI3K/AKT pathway activation were associated with disease progression in patients with MM. These findings indicated the critical roles of ABCG2 and PI3K/AKT signaling in controlling stemness of MM cells, and suggested a novel strategy for targeting ABCG2 and PI3K/AKT signaling to treat MM with MDR.

Emerging role of plumbagin: Cytotoxic potential and pharmaceutical relevance towards cancer therapy

Plumbagin is a naphthoquinone derived yellow crystalline phytochemical. Plumbagin has a wide range of biological effects including cytotoxicity against cancer cells both in vitro and in vivo. Due to the pleiotropic nature of plumbagin, it shows the anticancer effect by targeting several molecular mechanisms including apoptosis and autophagic pathways, cell cycle arrest, anti-angiogenic pathways, anti-invasion and anti-metastasis pathways. Among many signaling pathways the key regulatory genes regulated by plumbagin are NF-kβ, STAT3, and AKT, etc. Plumbagin is also a potent inducer of ROS, suppressor of cellular glutathione, and causes DNA strand break by oxidative DNA base damages. In vivo studies suggested that plumbagin significantly reduces the tumor weight and volume in dose-dependent manner without any side effects in tested model organisms. Another exciting aspect of plumbagin is the ability to re-sensitize the chemo and radioresistant cancer cells when used in combination or alone. Nano encapsulation of plumbagin overcomes the poor water solubility and bioavailability obstacles, enhancing the pharmaceutical relevance with better therapeutic efficacy. Moreover, plumbagin can be introduced as a future phytotherapeutic anticancer drug after fully satisfied preclinical and clinical trials.

Plumbagin induces ROS-mediated apoptosis and cell cycle arrest and inhibits EMT in human cervical carcinoma cells

Plumbagin, an important phytochemical from the roots of the medicinal plant Plumbago zeylanica L. has shown many biological activities. The roots of this plant have been in use in the Indian system of medicine for more than twenty five centuries for treatments of various ailments. It has shown anticancer activities, however, the anticancer and anti-metastatic effects of plumbagin are largely unknown against cervical cancer cells. Herein, we investigated the molecular alterations associated with plumbagin-mediated inhibition of growth, survival and epithelial to mesenchymal transition of human cervical cancer SiHa and HeLa cells. Plumbagin (1-4 μM) caused a significant decrease in the cell viability and increased the cell death in SiHa and Hela cells after 24 and 48 h. Plumbagin also caused strong G2/M and S-G2/M phase cell cycle arrest in SiHa and HeLa cells, respectively which was accompanied by a decrease in the expression of cyclin and CDK levels. The expression levels of both mRNAs and proteins of cyclin B1, A and E2 and CDK 1 and 2 decreased after 24 and 48 h. Plumbagin strongly induced apoptosis along with increased ratio of Bax : Bcl2 and cleavage of caspase 3, 9, and PARP. Plumbagin caused a significant increase in reactive oxygen species generation which mediated cell death as it was attenuated by pre-treatment with N-acetyl cysteine. Additionally, we also report for the first time that plumbagin possesses an anti-metastatic effect at non-cytotoxic doses that was accompanied by the modulation of MMP-2, 9, E-cadherin, N-cadherin, β-catenin and vimentin. Taken together, our findings suggest that plumbagin has strong anticancer and anti-metastatic effects against human cervical cancer cells.

Plumbagin inhibits the proliferation of nasopharyngeal carcinoma 6-10B cells by upregulation of reactive oxygen species

Plumbagin (PLB) is the primary component of the traditional Chinese medicine Baihua Dan, and possesses anti-infection and anticancer effects, with the ability to enhance the sensitivity of tumor cells to radiation therapy. However, the anticancer effect of PLB on nasopharyngeal carcinoma and the underlying mechanisms remain unclear. In this study, we investigated the anticancer effects of PLB on nasopharyngeal carcinoma 6-10B cells and clarified its molecular mechanisms in vitro. The results showed that PLB was effective against 6-10B cells proliferation in a dose-dependent manner by inducing G2/M phase cell cycle arrest. Furthermore, our data showed that PLB induced reactive oxygen species accumulation, which inhibited the GSK3β/STAT3 pathway and arrested the G2/M phase. Therefore, our results provided new insight into the mechanism of the antitumor effects of PLB, supporting PLB as a prospective therapeutic drug in nasopharyngeal carcinoma by modulating intracellular redox balance.

Exogenous H2 S exerts biphasic effects on porcine mammary epithelial cells proliferation through PI3K/Akt-mTOR signaling pathway

This study aimed to investigate the effects of exogenous H₂ S on the proliferation of porcine mammary gland epithelial cells (PMECs) and explore the underlying mechanisms. We found that exposure of PMECs to NaHS, at concentrations ranging from 10 to 200 µM, stimulated cell proliferation. However, high concentration of NaHS (600 µM) inhibited PMECs proliferation. Accordingly, 10 µM NaHS significantly increased the percentage of cells undergoing DNA replication, elevated the mRNA and/or protein expression of Cyclin A2, Cyclin D1/3, Cyclin E2 and PCNA, and decreased p21 mRNA expression. In contrast, 600 µM NaHS elicited the opposite effects to that of 10 µM NaHS. In addition, PI3 K/Akt and mTOR signaling pathways were activated or inhibited in response to 10 or 600 µM NaHS, respectively. Furthermore, the promotion of PMECs proliferation, the change of proliferative genes expression, and the activation of mTOR signaling pathway induced by 10 µM NaHS were effectively blocked by PI3 K inhibitor Wortmannin. Similarly, inhibition of mTOR with Rapamycin totally abolished the 10 µM NaHS-induced stimulation of PMECs proliferation and alteration of proliferative genes expression, with no influence on PI3 K/Akt signaling pathway. Moreover, constitutive activation of Akt pathway via transfection of Akt-CA completely eliminated the inhibition of PMECs proliferation and mTOR signaling pathway, and the change of proliferative genes expression induced by 600 µM NaHS. In conclusion, our findings provided evidence that exogenous H₂ S supplied by NaHS exerted biphasic effects on PMECs proliferation, with stimulation at lower doses and suppression at high dose, through the intracellular PI3 K/Akt-mTOR signaling pathway.

Discovery and cellular stress pathway analysis of 1,4-naphthoquinone derivatives with novel, highly potent broad-spectrum anticancer activity

BACKGROUND

Chemotherapy and targeted therapies have made important strides in cancer treatment yet they often fail and new therapies are still needed. Here, we employed a phenotypic screen to identify and analyze the mechanism of action of novel small molecules that interfere with critical pathways involved in tumor cell growth, using chemoresistant A375 melanoma cells as a model.

METHODS

Cell culture studies were performed in ATCC-recommended media. Compounds, and compound libraries were obtained from Boston University or purchased commercially. Effects on A375 cell viability, proliferation and morphology were determined by Celigo Image Cytometer and viability staining. Anticancer activity of the lead compound was tested in a xenograft nude mouse model. Signaling and cell death pathways were analyzed by SDS-PAGE and immunoblotting, and/or fluorescence microscopy.

RESULTS

After evaluating 4477 compounds, one hit compound CB533 was identified that caused significant reduction of A375 cell growth. CB533 is an unexplored 1,4-naphthoquinone (NQ) derivative which unlike 1,4-NQ, induced rapid cell death without generating reactive oxygen species (ROS). Structure-activity relationship analysis showed that a pyrrolidine in the 1,4-NQ nucleus in lead compound Pyr-1 yielded optimal activity. CB533 and Pyr-1 had growth-suppressing effects on a large variety of chemotherapy-resistant cancer cell lines in the nano to picomolar range. Pyr-1 also significantly reduced growth of MDA-MB-231 breast cancer cells in nude mice. Pyr-1 rapidly induced activation of major stress pathways and autophagy, which was efficiently blocked by ERK, and somewhat by PI3K inhibitors.

CONCLUSION

CB533 and lead Pyr-1 represent novel broad-spectrum, anticancer compounds that are up to 1000-fold more potent than plumbagin, a natural 1,4-NQ with known anticancer activity. Since the growth suppression activities of CB533 and Pyr-1 are unaffected by the chemotherapy resistance of cancer cells, these compounds have promising therapeutic potential. The pyrrolidine in the 3 position of the 1,4-NQ nucleus of Pyr-1 is a critical component of the pharmacophore. Pyr-1-induced cellular stress was mediated by an ERK, and to a lesser extent by an AKT-dependent pathway without involving apoptosis. Our data suggest that Pyr-1 derives its greatly enhanced antitumor activity via mimicking ROS-induced stress signaling without generating ROS, and likely committing cells to autophagy.

Phytochemicals and PI3K Inhibitors in Cancer-An Insight

In today's world of modern medicine and novel therapies, cancer still remains to be one of the prime contributor to the death of people worldwide. The modern therapies improve condition of cancer patients and are effective in early stages of cancer but the advanced metastasized stage of cancer remains untreatable. Also most of the cancer therapies are expensive and are associated with adverse side effects. Thus, considering the current status of cancer treatment there is scope to search for efficient therapies which are cost-effective and are associated with lesser and milder side effects. Phytochemicals have been utilized for many decades to prevent and cure various ailments and current evidences indicate use of phytochemicals as an effective treatment for cancer. Hyperactivation of phosphoinositide 3-kinase (PI3K) signaling cascades is a common phenomenon in most types of cancers. Thus, natural substances targeting PI3K pathway can be of great therapeutic potential in the treatment of cancer patients. This chapter summarizes the updated research on plant-derived substances targeting PI3K pathway and the current status of their preclinical studies and clinical trials.