A synthetic triterpenoid CDDO-Im inhibits tumorsphere formation by regulating stem cell signaling pathways in triple-negative breast cancer

Oleanolic acid and its analogues: promising therapeutics for kidney disease

Kidney diseases pose a significant threat to human health due to their high prevalence and mortality rates. Worryingly, the clinical use of drugs for kidney diseases is associated with more side effects, so more effective and safer treatments are urgently needed. Oleanolic acid (OA) is a common pentacyclic triterpenoid that is widely available in nature and has been shown to have protective effects in kidney disease. However, comprehensive studies on its role in kidney diseases are still lacking. Therefore, this article first explores the botanical sources, pharmacokinetics, derivatives, and safety of OA, followed by a summary of the anti-inflammatory, immunomodulatory, anti-oxidative stress, autophagy-enhancing, and antifibrotic effects of OA and its analogues in renal diseases, and an analysis of the molecular mechanisms, aiming to provide further insights for the development of novel drugs for the treatment of kidney diseases.

Evaluation of the Antitumor Potential of Soloxolone Tryptamide against Glioblastoma Multiforme Using in silico, in vitro, and in vivo Approaches

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor characterized by uncontrollable diffusive growth, resistance to chemo- and radiotherapy, and a high recurrence rate leading to a low survival rate of patients with GBM. Due to a large number of signaling pathways regulating GBM pathogenesis, one of the promising directions is development of novel anti-glioblastoma compounds based on natural metabolites capable of affecting multiple targets. Here, we investigated the antitumor potential of the semisynthetic triterpenoid soloxolone tryptamide (STA) against human glioblastoma U87 cells. STA efficiently blocked the growth of U87 cells in 2D and 3D cultures, enhanced adhesiveness of tumor cells, and displayed synergistic cytotoxicity with temozolomide. In silico analysis suggested that the anti-glioblastoma activity of STA can be explained by its direct interaction with EGFR, ERBB2, and AKT1 which play an important role in the regulation of GBM malignancy. Along with direct effect on U87 cells, STA normalized tumor microenvironment in murine heterotopic U87 xenograft model by suppressing the development of immature blood vessels and elastin production in the tumor tissue. Taken together, our results clearly demonstrate that STA can be a novel promising antitumor candidate for GMB treatment.

Nrf2 activation contributes to hepatic tumor-augmenting effects of developmental arsenic exposure

Developmental arsenic exposure increases cancer risk in later life with the mechanism elusive. Oxidative stress is a dominant determinant in arsenic toxicity. However, the role of Nrf2, a key regulator in antioxidative response, in tumor-augmenting effects by developmental arsenic exposure is unclear. In the present study, wild-type C57BL/6J and Nrf2-konckout (Nrf2-KO) were developmentally exposed to inorganic arsenic via drinking water. For hepatic tumorigenesis analysis, mice were intraperitoneally injected with diethylnitrosamine (DEN) at two weeks of age. Developmental arsenic exposure aggravated tumor multiplicity and burden, and expression of PCNA and AFP in hepatic tumors induced by DEN. Nrf2 activation as indicated by over-expression of Nrf2 and its downstream genes, including Gss, Gsr, p62, Gclc and Gclm, was found in liver tumors, as well as in the livers in developmentally arsenic-exposed pups at weaning. Notably, Nrf2 deficiency attenuated tumor-augmenting effects and over-expression of Nrf2 downstream genes due to developmental arsenic exposure. Furthermore, the levels of urinary DEN metabolite (acetaldehyde) and hepatic DNA damage markers (O6-ethyl-2-deoxyguanosine adducts and γ-histone H2AX) after DEN treatment were elevated by Nrf2 agonist, 2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide. Collectively, our data suggest that augmentation of DEN-induced hepatic tumorigenesis by developmental arsenic exposure is dependent on Nrf2 activation, which may be related to the role of Nrf2 in DEN metabolic activation. Our findings reveal, at least in part, the mechanism underlying increased susceptibility to developing cancer due to developmental arsenic exposure.

Rab13 sustains breast cancer stem cells by supporting tumor-stroma crosstalk

Cancer stem cells (CSC) are supported by the tumor microenvironment, and non-CSCs can regain CSC phenotypes in certain niches, leading to limited clinical benefits of CSC-targeted therapy. A better understanding of the mechanisms governing the orchestration of the CSC niche could help improve the therapeutic targeting of CSCs. Here, we report that Rab13, a small GTPase, is highly expressed in breast CSCs (BCSCs). Rab13 depletion suppressed breast cancer cell stemness, tumorigenesis, and chemoresistance by reducing tumor-stroma crosstalk. Accordingly, Rab13 controlled the membrane translocation of CXCR1/2, allowing tumor cells to interact with tumor-associated macrophages and cancer-associated fibroblasts to establish a supportive BCSC niche. Targeting the Rab13-mediated BCSC niche with bardoxolone-methyl (CDDO-Me) prevented BCSC stemness in vitro and in vivo. These findings highlight the novel regulatory mechanism of Rab13 in BCSC, with important implications for the development of therapeutic strategies for disrupting the BCSC niche.

Anticancer activity of oleanolic acid and its derivatives: Recent advances in evidence, target profiling and mechanisms of action

Oleanolic acid (OA, 3 β - hydroxyoleanolic acid-12-en-28-oic acid) is a pentacyclic triterpenoid present in many plants. As a new framework for development of semi synthetic triterpenoids, OA is of great significance in the discovery of anticancer drugs. Some of these derivatives, such as CDDO (2-cyano-3,12-dioxooleana-1, 9 (11)-dien-28-oic acid) have been verified in clinical trials, while other derivatives studied previously, such as SZC014, SZC015 and SZC017 (OA derivatives respectively), are also candidate drugs for cancer treatment. This paper reviews the preclinical studies, literature evidence, target analysis and anticancer mechanism of OA and its derivatives. The mechanism of action of its derivatives mainly includes anti-cancer cell proliferation, inducing tumor cell apoptosis, inducing autophagy, regulating cell cycle regulatory proteins, inhibiting vascular endothelial growth, anti angiogenesis, inhibiting tumor cell migration and invasion. In recent years, the molecular mechanism of OA and its derivatives has been elucidated. These effects seem to be mediated by the alterations in a variety of signaling pathways induced by OA and its derivatives. In conclusion, OA and its derivatives are considered as important candidate drugs for the treatment of cancer, indicating that OA and its derivatives have the potential to be used as anticancer drugs in practice.

Ursolic Acid and Related Analogues: Triterpenoids with Broad Health Benefits

Ursolic acid (UA) is a well-studied natural pentacyclic triterpenoid found in herbs, fruit and a number of traditional Chinese medicinal plants. UA has a broad range of biological activities and numerous potential health benefits. In this review, we summarize the current data on the bioavailability and pharmacokinetics of UA and review the literature on the biological activities of UA and its closest analogues in the context of inflammation, metabolic diseases, including liver and kidney diseases, obesity and diabetes, cardiovascular diseases, cancer, and neurological disorders. We end with a brief overview of UA’s main analogues with a special focus on a newly discovered naturally occurring analogue with intriguing biological properties and potential health benefits, 23-hydroxy ursolic acid.

Pisosterol Induces G2/M Cell Cycle Arrest and Apoptosis via the ATM/ATR Signaling Pathway in Human Glioma Cells

BACKGROUND

Pisosterol, a triterpene derived from Pisolithus tinctorius, exhibits potential antitumor activity in various malignancies. However, the molecular mechanisms that mediate the pisosterol-specific effects on glioma cells remain unknown.

OBJECTIVE

This study aimed to evaluate the antitumoral effects of pisosterol on glioma cell lines.

METHODS

The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and trypan blue exclusion assays were used to evaluate the effect of pisosterol on cell proliferation and viability in glioma cells. The effect of pisosterol on the distribution of the cells in the cell cycle was performed by flow cytometry. The expression and methylation pattern of the promoter region of MYC, ATM, BCL2, BMI1, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, MDM2, p14ARF and TP53 was analyzed by RT-qPCR, western blotting and bisulfite sequencing PCR (BSP-PCR).

RESULTS

Here, it has been reported that pisosterol markedly induced G2/M arrest and apoptosis and decreased the cell viability and proliferation potential of glioma cells in a dose-dependent manner by increasing the expression of ATM, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, p14ARF and TP53 and decreasing the expression of MYC, BCL2, BMI1 and MDM2. Pisosterol also triggered both caspase-independent and caspase-dependent apoptotic pathways by regulating the expression of Bcl-2 and activating caspase-3 and p53.

CONCLUSION

It has been, for the first time, confirmed that the ATM/ATR signaling pathway is a critical mechanism for G2/M arrest in pisosterol-induced glioma cell cycle arrest and suggests that this compound might be a promising anticancer candidate for further investigation.

Pathological changes of frozen shoulder in rat model and the therapeutic effect of PPAR-γ agonist

Frozen shoulder is a common shoulder disorder characterized by a gradual increase of pain and a limited range of motion. However, its pathophysiologic mechanisms remain unclear and there is no consensus as to the most effective treatment. The purpose of the study was to investigate the effect of transforming growth factor-β (TGF-β) on fibrosis and inflammatory response of the shoulder joint of rat models and to explore the therapeutic effect of the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist. In the study, the effect of PPAR-γ agonist CDDO-IM treatment on cell proliferation, migration, and extracellular matrix proteins synthesis (vimentin, α-smooth muscle actin, collagen I, and collagen III) were tested by cell proliferation test, scratches test, real-time quantitative polymerase chain reaction, and Western blot analysis. The frozen shoulder was also established on the rat model by injecting adenovirus-TGF-β1 into rats' shoulder capsule. Pathological changes of the frozen shoulder tissue of the experimental group and PPAR-γ agonist treatment group were evaluated. The stiffness of joints of the three groups was tested. Inflammatory mediators' expression including cyclooxygenase-1, interleukin-1β, and tumor necrosis factor-α of the shoulder was tested by enzyme-linked immunosorbent assay, and the expression of extracellular matrix proteins was evaluated by hematoxylin and eosin staining and immunohistochemistry. The results showed that pathological changes of the frozen shoulder in the rat model include an abnormal proliferation of fibroblasts, infiltration of inflammatory cells, and disorder of fibrous structure, while rosiglitazone reduced the severity of the frozen shoulder in the treatment group. Clinically, PPAR-γ agonists may be a promising target for the treatment of the frozen shoulder.

Epigenetic Regulation and Dietary Control of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) represents a highly heterogeneous group of breast cancers, lacking expression of the estrogen (ER) and progesterone (PR) receptors, and human epidermal growth factor receptor 2 (HER2). TNBC are characterized by a high level of mutation and metastasis, poor clinical outcomes and overall survival. Here, we review the epigenetic mechanisms of regulation involved in cell pathways disrupted in TNBC, with particular emphasis on dietary food components that may be exploited for the development of effective strategies for management of TNBC.

The role of natural products in revealing NRF2 function

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

CDDO-Me Elicits Anti-Breast Cancer Activity by Targeting LRP6 and FZD7 Receptor Complex

Aberrant activation of the Wnt/β-catenin pathway leads to the development of multiple cancers, including breast cancer. Development of therapeutic agents against this signaling pathway is an urgent need. In this study, we found that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) could inhibit Wnt/β-catenin signaling mainly through targeting the low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 receptor complex. This compound induced the degradation and ubiquitination of LRP6 and Fzd7 via the lysosomal pathway. We further showed that CDDO-Me mediated the degradation of FZD7 in an LRP6 ectodomain-dependent manner. In breast cancer cells, treatment with CDDO-Me increased the degradation of LRP6 and FZD7 and reduced the levels of phosphorylated Disheveled (DVL) 2 and active β-catenin, resulting in the downregulation of Wnt target genes and several cancer stem cell (CSC) marker genes. In a murine xenograft bearing mouse mammary tumor virus (MMTV)-Wnt1-driven mammary tumor, administration of CDDO-Me significantly inhibited tumor growth and was accompanied by reduced expression of phosphorylated and total LRP6, phosphorylated and unphosphorylated DVL2, active β-catenin, several Wnt target genes, and CSC marker genes. Collectively, the results of our study present that CDDO-Me is a potent Wnt/β-catenin signaling inhibitor that may be a promising therapeutic agent against breast cancer. SIGNIFICANCE STATEMENT: Blocking the membrane receptor complex consisting of low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 may help developing therapeutic approaches for cancers, including breast cancers. Our study indicates that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) can inhibit Wnt/β-catenin signaling by inducing the ubiquitination and degradation of LRP6/FZD7 membrane receptor complex via a lysosomal pathway. We also found that the ectodomain of LRP6 is essential for CDDO-Me-induced FZD7 degradation. Defining CDDO-Me as a novel inhibitor of Wnt/β-catenin signaling, our results provide insight into the mechanism of its anticancer activity.

Bidesmosidic betulin saponin bearing L-rhamnopyranoside moieties induces apoptosis and inhibition of lung cancer cells growth in vitro and in vivo

Betulin has a wide range of biological and pharmacological properties with its anticancer activity attracting most of the attention as it offers a possible alternative treatment to chemotherapy. However, betulin’s in vivo biological effectiveness is limited by its poor solubility. As such, we synthesized polar glycosylated derivatives to increase its hydrosolubility and enhance its pharmacological properties. Among these synthesized compounds, 28-O-α-l-rhamnopyranosylbetulin 3β-O-α-l-rhamnopyranoside (Bi-L-RhamBet) was assessed for its cytotoxic effects against a suite of lung cancer cell lines. We also investigated its mechanism of action using an A549 lung cancer cell line. Our results showed that Bi-L-RhamBet exhibited potent cytotoxic activity toward lung cancer cell lines including A549, NCI-H2087, NCI-H522, NCI-H1993 NCI-H1755, and LLC1 having IC₅₀ values ranging from 2.9 to 5.9 μM. Moreover, Bi-L-RhamBet (50 mg/kg) significantly inhibited tumor growth with a treatment-to-control ratio (T/C) of 0.54 and a tumor growth inhibition rate of 46% at day 18 (p < 0.05). Microscopic observations of A549 cells, double stained with acridine orange and ethidium bromide, showed apoptotic features. Bi-L-RhamBet induced activation of pro-apoptotic caspases 8, 9, and 3/7 as well as causing DNA fragmentation. Moreover, a marked increase in mitochondrial ROS (mROS) was coupled with a reduction of mitochondrial potential. Interestingly, the presence of mitochondrial electron transport chain (ETC) inhibitors, including rotenone, malonate, and antimycin A, reduced mROS production, and the activation of caspases suggesting that Bi-L-RhamBet disturbs the ETC. Finally, dichloroacetate, a pyruvate dehydrogenase kinase inhibitor potentiated the cytotoxicity of Bi-L-RhamBet against A549 cells. Taken together, these data suggest that Bi-L-RhamBet can induce apoptotic cell death via disturbance of mitochondrial electron transfer chain, reduced ROS production, and decreased membrane potential.

Nitro-fatty acid inhibition of triple-negative breast cancer cell viability, migration, invasion, and tumor growth

Triple-negative breast cancer (TNBC) comprises ∼20% of all breast cancers and is the most aggressive mammary cancer subtype. Devoid of the estrogen and progesterone receptors, along with the receptor tyrosine kinase ERB2 (HER2), that define most mammary cancers, there are no targeted therapies for patients with TNBC. This, combined with a high metastatic rate and a lower 5-year survival rate than for other breast cancer phenotypes, means there is significant unmet need for new therapeutic strategies. Herein, the anti-neoplastic effects of the electrophilic fatty acid nitroalkene derivative, 10-nitro-octadec-9-enoic acid (nitro-oleic acid, NO₂-OA), were investigated in multiple preclinical models of TNBC. NO₂-OA reduced TNBC cell growth and viability in vitro, attenuated TNFα-induced TNBC cell migration and invasion, and inhibited the tumor growth of MDA-MB-231 TNBC cell xenografts in the mammary fat pads of female nude mice. The up-regulation of these aggressive tumor cell growth, migration, and invasion phenotypes is mediated in part by the constitutive activation of pro-inflammatory nuclear factor κB (NF-κB) signaling in TNBC. NO₂-OA inhibited TNFα-induced NF-κB transcriptional activity in human TNBC cells and suppressed downstream NF-κB target gene expression, including the metastasis-related proteins intercellular adhesion molecule-1 and urokinase-type plasminogen activator. The mechanisms accounting for NF-κB signaling inhibition by NO₂-OA in TNBC cells were multifaceted, as NO₂-OA (a) inhibited the inhibitor of NF-κB subunit kinase β phosphorylation and downstream inhibitor of NF-κB degradation, (b) alkylated the NF-κB RelA protein to prevent DNA binding, and (c) promoted RelA polyubiquitination and proteasomal degradation. Comparisons with non-tumorigenic human breast epithelial MCF-10A and MCF7 cells revealed that NO₂-OA more selectively inhibited TNBC function. This was attributed to more facile mechanisms for maintaining redox homeostasis in normal breast epithelium, including a more favorable thiol/disulfide balance, greater extents of multidrug resistance protein-1 (MRP1) expression, and greater MRP1-mediated efflux of NO₂-OA-glutathione conjugates. These observations reveal that electrophilic fatty acid nitroalkenes react with more alkylation-sensitive targets in TNBC cells to inhibit growth and viability.

A Review of Systemic Treatment in Metastatic Triple-Negative Breast Cancer

Patients with breast cancer along with metastatic estrogen and progesterone receptor (ER/PR)- and human epidermal growth factor receptor 2 (HER2)-negative tumors are referred to as having metastatic triple-negative breast cancer (mTNBC) disease. Although there have been many new treatment options approved by the Food and Drug Administration for ER/PR-positive and Her2/neu-amplified metastatic breast cancer, relatively few new agents have been approved for patients with mTNBC. There have been several head-to-head chemotherapy trials performed within the metastatic setting, and much of what is applied in clinical practice is extrapolated from chemotherapy trials in the adjuvant setting, with taxanes and anthracyclines incorporated early on in the patient's treatment course. Select synergistic combinations can produce faster and more significant response rates compared with monotherapy and are typically used in the setting of visceral threat or symptomatic disease. Preclinical studies have implicated other possible targets and mechanisms in mTNBC. Ongoing clinical trials are underway assessing new chemotherapeutic strategies and agents, including targeted therapy and immunotherapy. In this review, we evaluate the standard systemic and future treatment options in mTNBC.

High-Throughput Method for Automated Colony and Cell Counting by Digital Image Analysis Based on Edge Detection

Counting cells and colonies is an integral part of high-throughput screens and quantitative cellular assays. Due to its subjective and time-intensive nature, manual counting has hindered the adoption of cellular assays such as tumor spheroid formation in high-throughput screens. The objective of this study was to develop an automated method for quick and reliable counting of cells and colonies from digital images. For this purpose, I developed an ImageJ macro Cell Colony Edge and a CellProfiler Pipeline Cell Colony Counting, and compared them to other open-source digital methods and manual counts. The ImageJ macro Cell Colony Edge is valuable in counting cells and colonies, and measuring their area, volume, morphology, and intensity. In this study, I demonstrate that Cell Colony Edge is superior to other open-source methods, in speed, accuracy and applicability to diverse cellular assays. It can fulfill the need to automate colony/cell counting in high-throughput screens, colony forming assays, and cellular assays.

CDDO and Its Role in Chronic Diseases

There has been a continued interest in translational research focused on both natural products and manipulation of functional groups on these compounds to create novel derivatives with higher desired activities. Oleanolic acid, a component of traditional Chinese medicine used in hepatitis therapy, was modified by chemical processes to form 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO). This modification increased anti-inflammatory activity significantly and additional functional groups on the CDDO backbone have shown promise in treating conditions ranging from kidney disease to obesity to diabetes. CDDO's therapeutic effect is due to its upregulation of the master antioxidant transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) through conformational change of Nrf2-repressing, Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1) and multiple animal and human studies have verified subsequent activation of Nrf2-controlled antioxidant genes via upstream Antioxidant Response Element (ARE) regions. At the present time, positive results have been obtained in the laboratory and clinical trials with CDDO derivatives treating conditions such as lung injury, inflammation and chronic kidney disease. However, clinical trials for cancer and cardiovascular disease have not shown equally positive results and further exploration of CDDO and its derivatives is needed to put these shortcomings into context for the purpose of future therapeutic modalities.

Cancer Stem and Progenitor-Like Cells as Pharmacological Targets in Breast Cancer Treatment

The present review is focused on the current role of neoplastic stem and progenitor-like cells as primary targets in the pharmacotherapy of cancer as well as in the development of new anticancer drugs. We begin by summarizing the main characteristics of these tumor-initiating cells and key concepts that support their participation in therapeutic failure. In particular, we discuss the differences between the major carcinogenesis models (ie, clonal evolution vs cancer stem cell (CSC) model) with emphasis on breast cancer (given its importance to the study of CSCs) and their implications for the development of new treatment strategies. In addition, we describe the main ways to target these cells, including the main signaling pathways that are more activated or altered in CSCs. Finally, we provide a comprehensive compilation of the most recently tested drugs.

Advances in small-molecule drug discovery for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of poor prognosis, highly invasive and difficult-to-treat breast cancers accounting for approximately 15% of clinical cases. Given the poor outlook and lack of sustained response to conventional therapies, TNBC has been the subject of intense studies on new therapeutic approaches in recent years. The development of targeted cancer therapies, often in combination with established chemotherapy, has been applied to a number of new clinical studies in this setting in recent years. This review will highlight recent therapeutic advances in TNBC, focusing on small-molecule drugs and their associated biological mechanisms of action, and offering the possibility of improved prospects for this patient group in the near future.

Novel synthetic pyridyl analogues of CDDO-Imidazolide are useful new tools in cancer prevention

Two new analogues of CDDO-Imidazolide (CDDO-Im), namely 1-[2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-2-yl)-1H-imidazole ("CDDO-2P-Im") and 1-[2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-3-yl)-1H-imidazole ("CDDO-3P-Im") have been synthesized and tested for their potential use as chemopreventive drugs. At nanomolar concentrations, they were equipotent to CDDO-Im for inducing differentiation and apoptosis in U937 leukemia cells. As inflammation and oxidative stress contribute to carcinogenesis, we also assessed their cytoprotective potential. The new compounds suppressed inducible nitric oxide synthase (iNOS) expression in RAW264.7 macrophage-like cells and significantly elevated heme oxygenase-1 (HO-1) and quinone reductase (NQO1) mRNA and protein levels in various mouse tissues in vivo. Most importantly, pharmacokinetic studies performed in vitro in human plasma and in vivo showed that each new analogue was more stable than CDDO-Im. Much higher concentrations of the new derivatives were found in mouse liver, lung, pancreas and kidney after gavage in contrast to CDDO-Im. Because of their better bioavailability and their excellent anti-inflammatory profile in vitro, CDDO-2P-Im and CDDO-3P-Im were tested for prevention in a highly relevant mouse lung cancer model, in which A/J mice develop lung carcinomas after injection of vinyl carbamate, a potent carcinogen. CDDO-2P-Im and CDDO-3P-Im were as effective as CDDO-Im for reducing the size and the severity of the lung tumors.

Metformin inhibits the proliferation, metastasis, and cancer stem-like sphere formation in osteosarcoma MG63 cells in vitro

Metformin is an oral drug that has been widely used to treat type 2 diabetes mellitus. Interestingly, accumulated evidence indicate that metformin may reduce the risk of cancer in patients with type 2 diabetes and inhibit tumor cell growth and survival in numerous malignancies, including osteosarcoma (OS) cells. In the present study, we aimed to investigate the effects of metformin on the proliferation, migration, invasion, and sphere formation in OS MG63 cells in vitro. Metformin suppressed OS MG63 cell proliferation in a dose- and time-dependent manner and markedly blocked anti-metastatic potentials, migration, and invasion, by downregulating matrix metalloproteinase 2 (MMP2) and MMP9. Besides, we established OS cancer stem-like cell (CSC) model with sarcosphere formation assay and demonstrated that metformin posed damage on CSCs in OS by inhibiting sphere formation and by inducing their stemness loss. The stemness of CSCs in OS such as self-renewal and differentiation potentials was both impaired with a significant decrease of Oct-4 and Nanog activation. Consistent with this, the positive rates of CD90, CD133, and stage-specific embryonic antigen-4 (SSEA-4) were all observed with reductions in response to metformin exposure. In addition, Western blot showed that metformin activated AMPKα at Tyr172, followed by a downregulated phosphorylation of mammalian target of rapamycin (mTOR)/S6 and feedback activation of p-AKT Ser(473) in both OS MG63 cells and CSCs. This indicates that AMPK/mTOR/S6 signaling pathway might be involved in the growth inhibition of both OS MG63 cells and CSCs. These results suggest that metformin, a potential anti-neoplastic agent, might make it a novel therapeutic choice for the treatment of OS in the future.

Vitamin D compounds reduce mammosphere formation and decrease expression of putative stem cell markers in breast cancer

Breast cancer stem cells (BCSCs) are a subset of tumor cells that are believed to be the cells responsible for the establishment and maintenance of tumors. Moreover, BCSCs are suggested to be the main cause of progression to metastasis and recurrence of cancer because of their tumor-initiating abilities and resistance to conventional therapies. Ductal carcinoma in situ (DCIS) is an early precursor in breast carcinogenesis which progresses to invasive ductal carcinoma (IDC). We have previously reported that a vitamin D compound, BXL0124, inhibits the progression of DCIS to IDC. In the present study we sought to determine whether this effect was mediated through an influence on BCSCs. In MCF10DCIS cells treated with vitamin D compounds (1α25(OH)2D3 or BXL0124), the breast cancer stem cell-like population, identified by the CD44(+)/CD24(-/low) and CD49f(+)/CD24(-/low) subpopulations, was reduced. To determine the effects of vitamin D compounds on cancer stem cell activity, the MCF10DCIS mammosphere cell culture system, which enriches for mammary progenitor cells and putative BCSCs, was utilized. Untreated MCF10DCIS mammospheres showed a disorganized and irregular shape. When MCF10DCIS cells were treated with 1α25(OH)2D3 or BXL0124, the mammospheres that formed exhibited a more organized, symmetrical and circular shape, similar to the appearance of spheres formed by the non-malignant, normal mammary epithelial cell line, MCF10A. The mammosphere forming efficiency (MFE) was significantly decreased upon treatment with 1α25(OH)2D3 or BXL0124, indicating that these compounds have an inhibitory effect on mammosphere development. Treatment with 1α25(OH)2D3 or BXL0124 repressed markers associated with the stem cell-like phenotype, such as CD44, CD49f, c-Notch1, and pNFκB. Furthermore, 1α25(OH)2D3 and BXL0124 reduced the expression of pluripotency markers, OCT4 and KLF-4 in mammospheres. This study suggests that vitamin D compounds repress the breast cancer stem cell-like population, potentially contributing to their inhibition of breast cancer. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.