Cucurbitacin B Causes Increased Radiation Sensitivity of Human Breast Cancer Cells via G2/M Cell Cycle Arrest

Potential of cucurbitacin as an anticancer drug

In Chinese medicine, the Cucurbitaceae family contains many compounds known as cucurbitacins, which have been categorized into 12 classes ranging from A to T and more than 200 derivatives. Cucurbitacins are a class of highly oxidized tetracyclic triterpenoids with potent anticancer properties. The eight components of cucurbitacins with the strongest anticancer activity are cucurbitacins B, D, E, I, IIa, L-glucoside, Q, and R. Cucurbitacins have also been reported to suppress JAK-STAT 3, mTOR, VEGFR, Wnt/β-catenin, and MAPK signaling pathways, all of which are crucial for the survival and demise of cancer cells. In this paper, we review the progress in research on cucurbitacin-induced apoptosis, autophagy, cytoskeleton disruption, cell cycle arrest, inhibition of cell proliferation, inhibition of invasion and migration, inhibition of angiogenesis, epigenetic alterations, and synergistic anticancer effects in tumor cells. Recent studies have identified cucurbitacins as promising molecules for therapeutic innovation with broad versatility in immune response. Thus, cucurbitacin is a promising class of anticancer agents that can be used alone or in combination with chemotherapy and radiotherapy for the treatment of many types of cancer.Therefore, based on the research reports in the past five years at home and abroad, we further summarize and review the structural characteristics, chemical and biological activities, and studies of cucurbitacins based on the previous studies to provide a reference for further development and utilization of cucurbitacins.

Recent Advances in the Application of Cucurbitacins as Anticancer Agents

Cucurbitacins are tetracyclic triterpenoid secondary metabolites, widely distributed in the Cucurbitaceae family. These bitter-tasting compounds act primarily as defense mechanisms against external injuries, and thus against herbivores, and furthermore, they have also found use in folk medicine in the treatment of various diseases. Many studies have acknowledged significant biological activities of cucurbitacins, such as antioxidant and anti-inflammatory activities, antimicrobial properties, or antitumor potential. Overall, cucurbitacins have the ability to inhibit cell proliferation and induce apoptosis in various cancer cell lines. Both in vitro and in vivo studies were performed to evaluate the anticancer activity of varied cucurbitacins. Cucurbitacins offer a promising avenue for future cancer treatment strategies, and their diverse mechanisms of action make them attractive candidates for further investigation. The aim of the present study is to shed light on the chemical diversity of this group of compounds by providing the sources of origin of selected compounds and their chemical structure, as well as insight into their anticancer potential. In addition, within this paper molecular targets for cucurbitacins and signalling pathways important for cancer cell proliferation and/or survival that are affected by the described class of compounds have been presented.

Cucurbitacins as Potent Chemo-Preventive Agents: Mechanistic Insight and Recent Trends

Cucurbitacins constitute a group of cucumber-derived dietary lipids, highly oxidized tetracyclic triterpenoids, with potential medical uses. These compounds are known to interact with a variety of recognized cellular targets to impede the growth of cancer cells. Accumulating evidence has suggested that inhibition of tumor cell growth via induction of apoptosis, cell-cycle arrest, anti-metastasis and anti-angiogenesis are major promising chemo-preventive actions of cucurbitacins. Cucurbitacins may be a potential choice for investigations of synergism with other drugs to reverse cancer cells' treatment resistance. The detailed molecular mechanisms underlying these effects include interactions between cucurbitacins and numerous cellular targets (Bcl-2/Bax, caspases, STAT3, cyclins, NF-κB, COX-2, MMP-9, VEGF/R, etc.) as well as control of a variety of intracellular signal transduction pathways. The current study is focused on the efforts undertaken to find possible molecular targets for cucurbitacins in suppressing diverse malignant processes. The review is distinctive since it presents all potential molecular targets of cucurbitacins in cancer on one common podium.

Dual Hyaluronic Acid and Folic Acid Targeting pH-Sensitive Multifunctional 2DG@DCA@MgO-Nano-Core-Shell-Radiosensitizer for Breast Cancer Therapy

Simple Summary

In this study, we have developed CD44 and folate receptor-targeting multi-functional dual drug-loaded nanoparticles. This comprises hyaluronic acid (HA) and folic acid (FA) conjugated to 2-deoxy glucose (2DG) and a shell linked to a dichloroacetate (DCA) and magnesium oxide (MgO) core (2DG@DCA@MgO; DDM) to enhance the localized chemo-radiotherapy for effective breast cancer (BC) treatment. The physicochemical properties of nanoparticles including stability, selectivity, responsive release to pH, cellular uptake, and anticancer efficacy were comprehensively examined. Mechanistically, we identified multiple component signal pathways as important regulators of BC metabolism and mediators for the inhibitory effects exerted by DDM. Nanoparticles exhibited sustained DDM release properties in bio-relevant media, which was responsive to acidic pH providing edibility to the control of drug release from nanoparticles. DDM-loaded and HA–FA-functionalized nanoparticles exhibited increased selectivity and uptake by BC cells. Cell-based assays indicated that the functionalized DDM significantly suppressed cancer cell growth and boosted radiotherapy (RT) efficacy via inducing cell cycle arrest, enhancing apoptosis, and modulating glycolytic and OXPHOS pathways. Accordingly, the inhibition of glycolysis/OXPHOS by DDM and RT treatment may result in cancer metabolic reprogramming via a novel PI3K/AKT/mTOR/P53NF-κB/VEGF pathway in BC cells. Therefore, the dual targeting of glycolysis/OXPHOS pathways is suggested as a promising antitumor strategy.

Abstract

Globally, breast cancer (BC) poses a serious public health risk. The disease exhibits a complex heterogeneous etiology and is associated with a glycolytic and oxidative phosphorylation (OXPHOS) metabolic reprogramming phenotype, which fuels proliferation and progression. Due to the late manifestation of symptoms, rigorous treatment regimens are required following diagnosis. Existing treatments are limited by a lack of specificity, systemic toxicity, temporary remission, and radio-resistance in BC. In this study, we have developed CD44 and folate receptor-targeting multi-functional dual drug-loaded nanoparticles. This composed of hyaluronic acid (HA) and folic acid (FA) conjugated to a 2-deoxy glucose (2DG) shell linked to a layer of dichloroacetate (DCA) and a magnesium oxide (MgO) core (2DG@DCA@MgO; DDM) to enhance the localized chemo-radiotherapy for effective BC treatment. The physicochemical properties of nanoparticles including stability, selectivity, responsive release to pH, cellular uptake, and anticancer efficacy were thoroughly examined. Mechanistically, we identified multiple component signaling pathways as important regulators of BC metabolism and mediators for the inhibitory effects elicited by DDM. Nanoparticles exhibited sustained DDM release properties in a bio-relevant media, which was responsive to the acidic pH enabling eligibility to the control of drug release from nanoparticles. DDM-loaded and HA–FA-functionalized nanoparticles exhibited increased selectivity and uptake by BC cells. Cell-based assays revealed that the functionalized DDM significantly suppressed cancer cell growth and improved radiotherapy (RT) through inducing cell cycle arrest, enhancing apoptosis, and modulating glycolytic and OXPHOS pathways. By highlighting DDM mechanisms as an antitumor and radio-sensitizing reagent, our data suggest that glycolytic and OXPHOS pathway modulation occurs via the PI3K/AKT/mTOR/NF-κB/VEGF_low and P53_high signaling pathway. In conclusion, the multi-functionalized DDM opposed tumor-associated metabolic reprogramming via multiple signaling pathways in BC cells as a promising targeted metabolic approach.

Modeling bystander effects that cause growth delay of breast cancer xenografts in bone marrow of mice treated with radium-223

RATIONALE

The role of radiation-induced bystander effects in cancer therapy with alpha-particle emitting radiopharmaceuticals remains unclear. With renewed interest in using alpha-particle emitters to sterilize disseminated tumor cells, micrometastases, and tumors, a better understanding of the direct effects of alpha particles and the contribution of the bystander responses they induce is needed to refine dosimetric models that help predict clinical benefit. Accordingly, this work models and quantifies the relative importance of direct effects (DE) and bystander effects (BE) in the growth delay of human breast cancer xenografts observed previously in the tibiae of mice treated with 223RaCl2.

METHODS

A computational model of MDA-MB-231 and MCF-7 human breast cancer xenografts in the tibial bone marrow of mice administered 223RaCl2 was created. A Monte Carlo radiation transport simulation was performed to assess individual cell absorbed doses. The responses of the breast cancer cells to direct alpha particle irradiation and gamma irradiation were needed as input data for the model and were determined experimentally using a colony-forming assay and compared to the responses of preosteoblast MC3T3-E1 and osteocyte-like MLO-Y4 bone cells. Using these data, a scheme was devised to simulate the dynamic proliferation of the tumors in vivo, including DE and BE propagated from the irradiated cells. The parameters of the scheme were estimated semi-empirically to fit experimental tumor growth.

RESULTS

A robust BE component, in addition to a much smaller DE component, was required to simulate the in vivo tumor proliferation. We also found that the relative biological effectiveness (RBE) for cell killing by alpha particle radiation was greater for the bone cells than the tumor cells.

CONCLUSION

This modeling study demonstrates that DE of radiation alone cannot explain experimental observations of 223RaCl2-induced growth delay of human breast cancer xenografts. Furthermore, while the mechanisms underlying BE remain unclear, the addition of a BE component to the model is necessary to provide an accurate prediction of the growth delay. More complex models are needed to further comprehend the extent and complexity of 223RaCl2-induced BE.

A Bioreductive Prodrug of Cucurbitacin B Significantly Inhibits Tumor Growth in the 4T1 Xenograft Mice Model

Cucurbitacin B (CuB), a highly cytotoxic constituent of the Cucurbitaceae plant, was identified to exhibit potent inhibitory activity against human cancer cells as well as normal cells. This disadvantage hampers the possibility of developing this compound into an anticancer drug candidate. In this work, several bioreductive prodrugs of CuB were designed to reduce toxicity to normal cells while maintaining the cytotoxic effect to cancer cells. Embedded with a bioreductive delivery and cleavable system in cancer tissues, cucurbitacin B-based prodrugs 1, 2, and 3 were synthesized and evaluated by in vitro and in vivo experiments. Compared with the parent CuB, prodrug 1 was found to significantly reduce the toxicity down to 310-fold lower against noncancerous cells. LC-MS analyses show that prodrug 1 efficiently releases the parent compound in the reductase-overexpressed MCF-7 cells. In addition, prodrug 1 shows satisfactory and comparable effectiveness in controlling tumor growth as that by tamoxifen in the 4T1 xenograft mice model.

Dose-Dependent Growth Delay of Breast Cancer Xenografts in the Bone Marrow of Mice Treated with 223Ra: The Role of Bystander Effects and Their Potential for Therapy

The role of radiation-induced bystander effects in radiation therapy remains unclear. With renewed interest in therapy with α-particle emitters, and their potential for sterilizing disseminated tumor cells (DTCs), it is critical to determine the contribution of bystander effects to the overall response so they can be leveraged for maximum clinical benefit. Methods: Female Foxn1_nu athymic nude mice were administered 0, 50, or 600 kBq/kg ²²³RaCl₂ to create bystander conditions. At 24 hours after administration, MDA-MB-231 or MCF-7 human breast cancer cells expressing luciferase were injected into the tibial marrow compartment. Tumor burden was tracked weekly via bioluminescence. Results: The MDA-MB-231 xenografts were observed to have a 10-day growth delay in the 600 kBq/kg treatment group only. In contrast, MCF-7 cells had 7- and 65-day growth delays in the 50 and 600 kBq/kg groups, respectively. Histologic imaging of the tibial marrow compartment, α-camera imaging, and Monte Carlo dosimetry modeling revealed DTCs both within and beyond the range of the α-particles emitted from ²²³Ra in bone for both MCF-7 and MDA-MB-231 cells. Conclusion: Taken together, these results support the participation of ²²³Ra-induced antiproliferative/cytotoxic bystander effects in delayed growth of DTC xenografts. They indicate that the delay depends on the injected activity and therefore is dose-dependent. They suggest using ²²³RaCl₂ as an adjuvant treatment for select patients at early stages of breast cancer.

PARP inhibitors affect growth, survival and radiation susceptibility of human alveolar and embryonal rhabdomyosarcoma cell lines

PURPOSE

PARP inhibitors (PARPi) are used in a wide range of human solid tumours but a limited evidence is reported in rhabdomyosarcoma (RMS), the most frequent childhood soft-tissue sarcoma. The cellular and molecular effects of Olaparib, a specific PARP1/2 inhibitor, and AZD2461, a newly synthesized PARP1/2/3 inhibitor, were assessed in alveolar and embryonal RMS cells both as single-agent and in combination with ionizing radiation (IR).

METHODS

Cell viability was monitored by trypan blue exclusion dye assays. Cell cycle progression and apoptosis were measured by flow cytometry, and alterations of specific molecular markers were investigated by, Real Time PCR, Western blotting and immunofluorescence experiments. Irradiations were carried out at a dose rate of 2 Gy (190 UM/min) or 4 Gy (380 UM/min). Radiosensitivity was assessed by using clonogenic assays.

RESULTS

Olaparib and AZD2461 dose-dependently reduced growth of both RH30 and RD cells by arresting growth at G2/M phase and by modulating the expression, activation and subcellular localization of specific cell cycle regulators. Downregulation of phospho-AKT levels and accumulation of γH2AX, a specific marker of DNA damage, were significantly and persistently induced by Olaparib and AZD2461 exposure, this leading to apoptosis-related cell death. Both PARPi significantly enhanced the effects of IR by accumulating DNA damage, increasing G2 arrest and drastically reducing the clonogenic capacity of RMS-cotreated cells.

CONCLUSIONS

This study suggests that the combined exposure to PARPi and IR might display a role in the treatment of RMS tumours compared with single-agent exposure, since stronger cytotoxic effects are induced, and compensatory survival mechanisms are prevented.

Cucurbitacin B and cancer intervention: Chemistry, biology and mechanisms (Review)

Cancer is one of the most important healthcare matters, with the worst prognosis but the best possibilities for scientific development. It is likely to increase in the future and cause global havoc designating it as an epidemic. Cancer development requires urgent intervention. Past few decades have witnessed extensive research to challenge carcinogenesis. Treatment involving synthetic discipline is often associated with severe adverse effects, or even worsened prognosis. Accordingly, newer economic and patient friendly molecules are warranted. Many natural substances have proved their potential so far. Cucurbitacin B against cancer and other diseases has achieved towering popularity among the researchers around the world, as detailed in the below sections with summarized tables. In line with the fascinating role of cucurbitacin B against various types of cancers, through various molecular signaling pathways, it is justifiable to propose cucurbitacin B as a mainline chemotherapy before the onset and after the diagnosis of cancer.

Sestrin-3 modulation is essential for therapeutic efficacy of cucurbitacin B in lung cancer cells

Many purified compounds from dietary sources have been investigated for their anticancer activities. The main issue with most agents is their effectiveness at high doses which generally could not be delivered to humans through dietary consumption. Here, we observed that cucurbitacin B, a tetracyclic triterpenoid present in pumpkins, gourds and squashes, exhibits antiproliferative effects on human non-small cell lung cancer (NSCLC) cells at nanomolar concentrations. Treatment with cucurbitacin B (0.2-0.6 μM; 24 h) was found to result in decrease in the viability of EGFR-wild type (A549 and H1792) and EGFR-mutant lung cancer cells (H1650 and H1975) and reduction in cell-colonies but had only minimal effect on normal human bronchial epithelial cells. Treatment with cucurbitacin B also caused inhibition of PI3K/mTOR and signal transducer and activator of transcription (STAT)-3 signaling along with simultaneous activation of AMPKα levels in both EGFR-wild type and EGFR-mutant lung cancer cells. Cucurbitacin B caused specific increase in the protein and mRNA expression of sestrin-3 in EGFR-mutant lung cancer cells, but not in EGFR-wild type cells. Treatment with cucurbitacin B to sestrin-3 siRNA treated EGFR-mutant cells further amplified the decrease in cell-viability and caused more sustained G2-phase cell cycle arrest, suggesting that these effects are mediated partly through sestrin-3. We also found that sestrin-3 has a role in the induction of apoptosis by cucurbitacin B in both EGFR-wild type and EGFR-mutant lung cancer cells. These findings suggest novel mechanism by the modulation of sestrin-3 for the action of cucurbitacin B and suggest that it could be developed as an agent for therapy of NSCLC.

Silencing of FANCD2 enhances the radiosensitivity of metastatic cervical lymph node-derived head and neck squamous cell carcinoma HSC-4 cells

Fanconi anemia complementation group D2 (FANCD2) is involved in the key steps of the Fanconi anemia (FA) pathway, which plays a role in the repair of DNA crosslink damage. However, the role of FANCD2 during radiotherapy for head and neck squamous cell carcinoma (HNSCC) is unclear. In this study, the HNSCC cell line HSC-4 was used. Western blotting was used to evaluate the expression of the FANCD2 in HSC-4 cells. We investigated the impact of FANCD2 on the radiosensitivity of HSC-4 cells in vitro and in vivo. TUNEL, western blotting and immunohistochemistry were used to analyze the apoptosis and proteins involved in apoptosis-related pathways after radiotherapy to investigate the relevant mechanism. The present study showed that shRNA interference could effectively and stably silence FANCD2 expression in HSC-4 cells. In vitro, the silencing of FANCD2 inhibited cell proliferation, decreased the survival rate, increased apoptosis and induced S phase arrest in HSC-4 cells after radiotherapy. In vivo, the silencing of FANCD2 could prolong the tumor-forming time and slow tumor growth. In addition, the tumor volume was significantly reduced, the weight was deceased, and the tumor inhibition rate was increased after radiotherapy. TUNEL showed that the silencing of FANCD2 significantly increased apoptosis in HSC-4 cells induced by radiotherapy. Both in vitro and in vivo esperiments revealed that the expression of the Bax and p-p38 proteins in HSC-4 cells, in which FANCD2 had been silenced, was increased after radiotherapy, whereas the expression of the p38 and Bcl2 proteins was decreased. Our results suggested that the silencing of FANCD2 enhanced the radiosensitivity of HSC-4 cells, and its mechanism involves the activation of the p38 MAPK signaling pathway and the regulation of the expression of Bax and Bcl2 proteins. This study provides a novel candidate target for HNSCC therapy.

Radioprotective potential of Lagenaria siceraria extract against radiation-induced gastrointestinal injury

The cucurbits (prebiotics) were investigated as novel agents for radio-modification against gastrointestinal injury. The cell-cycle fractions and DNA damage were monitored in HCT-15 cells. A cucurbit extract was added to culture medium 2 h before irradiation (6 Gy) and was substituted by fresh medium at 4 h post-irradiation. The whole extract of the fruits of Lagenaria siceraria, Luffa cylindrica, or Cucurbita pepo extract enhanced G2 fractions (42%, 34%, and 37%, respectively) as compared with control (20%) and irradiated control (31%). With cucurbits, the comet tail length remained shorter (L. siceraria, 28 μm; L. cylindrica, 34.2 μm; C. pepo, 36.75 μm) than irradiated control (41.75 μm). For in vivo studies, L. siceraria extract (2 mg/kg body weight) was administered orally to mice at 2 h before and 4 and 24 h after whole-body irradiation (10 Gy). L. siceraria treatment restored the glutathione contents to 48.8 μmol/gm as compared with control (27.6 μmol/gm) and irradiated control (19.6 μmol/gm). Irradiation reduced the villi height from 379 to 350 μm and width from 54 to 27 μm. L. siceraria administration countered the radiation effects (length, 366 μm; width, 30 μm, respectively) and improved the villi morphology and tight junction integrity. This study reveals the therapeutic potential of cucurbits against radiation-induced gastrointestinal injury.

Functional Characterisation of Anticancer Activity in the Aqueous Extract of Helicteres angustifolia L. Roots

Helicteres angustifolia L. is a shrub that forms a common ingredient of several cancer treatment recipes in traditional medicine system both in China and Laos. In order to investigate molecular mechanisms of its anticancer activity, we prepared aqueous extract of Helicteresangustifolia L. Roots (AQHAR) and performed several in vitro assays using human normal fibroblasts (TIG-3) and osteosarcoma (U2OS). We found that AQHAR caused growth arrest/apoptosis of U2OS cells in a dose-dependent manner. It showed no cytotoxicity to TIG-3 cells at doses up to 50 μg/ml. Biochemical, imaging and cell cycle analyses revealed that it induces ROS signaling and DNA damage response selectively in cancer cells. The latter showed upregulation of p53, p21 and downregulation of Cyclin B1 and phospho-Rb. Furthermore, AQHAR-induced apoptosis was mediated by increase in pro-apoptotic proteins including cleaved PARP, caspases and Bax. Anti-apoptotic protein Bcl-2 showed decrease in AQHAR-treated U2OS cells. In vivo xenograft tumor assays in nude mice revealed dose-dependent suppression of tumor growth and lung metastasis with no toxicity to the animals suggesting that AQHAR could be a potent and safe natural drug for cancer treatment.

Cucurbitacins: A Systematic Review of the Phytochemistry and Anticancer Activity

Cucurbitacins are highly oxidized tetracyclic triterpenoids that are widely present in traditional Chinese medicines (Cucurbitaceae family), possess strong anticancer activity, and are divided into 12 classes from A to T with over 200 derivatives. The eight most active cucurbitacin components against cancer are cucurbitacin B, D, E, I, IIa, L glucoside, Q, and R. Their mechanisms of action include antiproliferation, inhibition of migration and invasion, proapoptosis, and cell cycle arrest promotion. Cucurbitacins are also found to be the inhibitors of JAK-STAT3, Wnt, PI3K/Akt, and MAPK signaling pathways, which play important roles in the apoptosis and survival of cancer cells. Recently, new studies have discovered synergistic anticancer effects by using cucurbitacins together with clinically approved chemotherapeutic drugs, such as docetaxel and methotrexate. This paper provides a summary of recent research progress on the anticancer property of cucurbitacins and the various intracellular signaling pathways involved in the regulation of cancer cell proliferation, death, invasion, and migration. Therefore, cucurbitacins are a class of promising anticancer drugs to be used alone or be intergraded in current chemotherapies and radiotherapies to treat many types of cancers.

Synergistic Antiproliferative Effects of a New Cucurbitacin B Derivative and Chemotherapy Drugs on Lung Cancer Cell Line A549

Nonsmall cell lung cancer (NSCLC) represents an important cause of mortality worldwide due to its aggressiveness and growing resistance to currently available therapy. Cucurbitacins have emerged as novel potential anticancer agents showing strong antiproliferative effects and can be promising candidates for combined treatments with clinically used anticancer agents. This study investigates the synergistic antiproliferative effects of a new semisynthetic derivative of cucurbitacin B (DACE) with three chemotherapy drugs: cisplatin (CIS), irinotecan (IRI), and paclitaxel (PAC) on A549 cells. The most effective combinations were selected for studies of the mechanism of action. Using an in silico tool, DACE seems to act by a different mechanism of action when compared with that of different classes of drugs already used in clinical settings. DACE also showed potent synergic effects with drugs, and the most potent combinations induced G2/M cell cycle arrest by modulating survivin and p53 expression, disruption of F-actin cytoskeleton, and cell death by apoptosis. These treatments completely inhibited the clonogenic potential and did not reduce the proliferation of nontumoral lung cells (MRC-5). DACE also showed relevant antimigratory and anti-invasive effects, and combined treatments modulated cell migration signaling pathways evolved with metastasis progression. The effects of DACE associated with drugs was potentiated by the oxidant agent l-buthionine-sulfoximine (BSO), and attenuated by N-acetilcysteine (NAC), an antioxidant agent. The antiproliferative effects induced by combined treatments were attenuated by a pan-caspase inhibitor, indicating that the effects of these treatments are dependent on caspase activity. Our data highlight the therapeutic potential of DACE used in combination with known chemotherapy drugs and offer important insights for the development of more effective and selective therapies against lung cancer.

Radiosensitivity in HeLa cervical cancer cells overexpressing glutathione S-transferase π 1

The aims of the present study were to investigate the effect of overexpressed exogenous glutathione S-transferase π 1 (GSTP1) gene on the radiosensitivity of the HeLa human cervical cancer cell line and conduct a preliminarily investigation into the underlying mechanisms of the effect. The full-length sequence of human GSTP1 was obtained by performing a polymerase chain reaction (PCR) using primers based on the GenBank sequence of GSTP1. Subsequently, the gene was cloned into a recombinant eukaryotic expression plasmid, and the resulting construct was confirmed by restriction analysis and DNA sequencing. A HeLa cell line that was stably expressing high levels of GSTP1 was obtained through stable transfection of the constructed plasmids using lipofectamine and screening for G418 resistance, as demonstrated by reverse transcription-PCR. Using the transfected HeLa cells, a colony formation assay was conducted to detect the influence of GSTP1 overexpression on the cell radiosensitivity. Furthermore, flow cytometry was used to investigate the effect of GSTP1 overexpression on cell cycle progression, with the protein expression levels of the cell cycle regulating factor cyclin B1 detected using western blot analysis. Colony formation and G₂/M phase arrest in the GSTP1-expressing cells were significantly increased compared with the control group (P<0.01). In addition, the expression of cyclin B1 was significantly reduced in the GSTP1-expressing cells. These results demonstrated that increased expression of GSTP1 inhibits radiosensitivity in HeLa cells. The mechanism underlying this effect may be associated with the ability of the GSTP1 protein to reduce cyclin B1 expression, resulting in significant G₂/M phase arrest.

Panepoxydone targets NF-kB and FOXM1 to inhibit proliferation, induce apoptosis and reverse epithelial to mesenchymal transition in breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is a highly diverse group that is associated with an aggressive phenotype. Its treatment has been challenging due to its heterogeneity and absence of well-defined molecular targets. Thus, there is an urgent need to identify novel agents with therapeutic application. NF-κB is over-expressed in many breast cancers; thus, inactivation of the NF-κB pathway could serve as a therapeutic target. Here we report for the first time the anti-tumor activity of panepoxydone (PP), a NF-κB inhibitor isolated from an edible mushroom, in several breast cancer cell lines.

METHODS

We investigated the effects of PP on cell growth, migration-invasion, apoptosis and EMT-related proteins expression in MCF-7 and TNBC cell lines MDA-MB-231, MDA-MB-468 and MDA-MB-453.

RESULTS

Significant antitumor activity was seen in all cell lines, with differential responses noted in cell-line specific manner. Treatment with PP resulted in significant cytotoxicity, decreased invasion, migration and increased apoptosis in all cell lines tested. Up-regulation of Bax and cleaved PARP and down-regulation of Bcl-2, survivin, cyclin D1 and caspase 3 were noted in PP-treated breast cancer cells. The antitumor effect of PP appeared related to its ability to inhibit the phosphorylation of inhibitor of NF-κB (IκBα) with cytoplasmic accumulation. PP treatment also down-regulated FOXM1 which resulted in a reversal of EMT. Similar results were obtained after silencing of NF-kB and FOXM1.

CONCLUSION

Altogether, these studies show, for the first time the antitumor activity of PP against breast cancer cells, in particular TNBC cells. Furthermore, it highlights the concept that optimal treatment of TNBC warrants attention to the differential sensitivity of various TNBC subtypes to therapeutic agents. These results suggest that the PP may be a potentially effective chemopreventive or therapeutic agent against breast cancer. However, additional studies are required to more fully elucidate the mechanism of antitumor effect of PP.

Cucurbitacin-E inhibits multiple cancer cells proliferation through attenuation of Wnt/β-catenin signaling

Recent studies suggest that the use of cucurbitacins could inhibit cancer cell progression. In the current study, the authors analyzed the effect of cucurbitacin-E (CuE) in cancer cells using A549, Hep3B, and SW480 cells. The authors found that CuE inhibited cell proliferation and modulated the expression of cell cycle regulators in these cells. Moreover, the authors found that CuE inhibited Wnt/β-catenin signaling activation through upregulation of tumor suppressor Menin. Indeed, ablation of Menin using small interfering RNA (siRNA) oligos attenuated the antiproliferative roles of CuE. Taken together, the results of this study provide a novel mechanism that may contribute to the antineoplastic effects of CuE in cancer cells.

Inactivation of ATP citrate lyase by Cucurbitacin B: A bioactive compound from cucumber, inhibits prostate cancer growth

Prostate cancer, a leading cause of cancer-related deaths in males, is well recognized as having late disease on-set (mostly at age 60-70) and showing slow/latent disease development, and strategies to prevent cancer formation in late manhood may have significant health impacts. Cucurbitacin B (CuB) is a naturally occurring compound that is found abundantly in cucumbers and other vegetables, and it is known to exert anti-cancer activities (primarily via apoptosis-induction) in several human cancers. However, its chemopreventive potential for prostate cancer has not yet been investigated. Here, we reported that CuB significantly and specifically inhibited prostate cancer cell growth with low IC50 (~0.3 μM; PC-3 and LNCaP), accompanied by marked apoptosis (Caspase 3/7 activation, PARP cleavage, increase of Annexin V-Alexa Fluor 488 (Alexa488)+ cells and accumulation of Sub-G0/G1 population), whereas normal human prostate epithelial cells (PrEC) were CuB-insensitive. Using a chemopreventive model, pre-treatment of mice with CuB (2 weeks before PC-3 prostate cancer cell implantation) significantly reduced the rate of in vivo tumor-formation. A 79% reduction in tumor size (accompanied by marked in situ apoptosis) was observed in the CuB-treated group (with no noticeable toxicity) vs. controls at day 31. Strikingly, mechanistic investigations demonstrated that CuB drove dose-dependent inhibition of ATP citrate lyase phosphorylation (ACLY; an important enzyme for cancer metabolism) both in vitro and in the CuB-chemopreventive mouse model. Importantly, ACLY over-expression abrogated CuB's apoptotic effects in prostate cancer cells, confirming ACLY as a direct target of CuB. Thus, CuB harbors potent chemopreventive activity for prostate cancer, and we revealed a novel anti-tumor mechanism of CuB via inhibition of ACYL signaling in human cancer.

The triterpenoid cucurbitacin B augments the antiproliferative activity of chemotherapy in human breast cancer

Despite recent advances in therapy, breast cancer remains the second most common cause of death from malignancy in women. Chemotherapy plays a major role in breast cancer management, and combining chemotherapeutic agents with nonchemotherapeutic agents is of considerable clinical interest. Cucurbitacins are triterpenes compounds found in plants of the Cucurbitaceae family, reported to have anticancer and anti-inflammatory activities. Previously, we have shown antiproliferative activity of cucurbitacin B (CuB) in breast cancer, and we hypothesized that combining CuB with chemotherapeutic agents can augment their antitumor effect. Here, we show that a combination of CuB with either docetaxel (DOC) or gemcitabine (GEM) synergistically inhibited the proliferation of MDA-MB-231 breast cancer cells in vitro. This antiproliferative effect was accompanied by an increase in apoptosis rates. Furthermore, in vivo treatment of human breast cancer orthotopic xenografts in immunodeficient mice with CuB at either low (0.5 mg/kg) or high (1 mg/kg) doses in combination with either DOC (20 mg/kg) or GEM (12.5mg/kg) significantly reduced tumor volume as compared with monotherapy of each drug. Importantly, no significant toxicity was noted with low-dose CuB in combination with either DOC or GEM. In conclusion, combination of CuB at a relatively low concentration with either of the chemotherapeutic agents, DOC or GEM, shows prominent antiproliferative activity against breast cancer cells without increased toxicity. This promising combination should be examined in therapeutic trials of breast cancer.