Rapamycin potentiates the effects of paclitaxel in endometrial cancer cells through inhibition of cell proliferation and induction of apoptosis

Small molecule targeted therapies for endometrial cancer: progress, challenges, and opportunities

Endometrial cancer (EC) is a common malignancy among women worldwide, and its recurrence makes it a common cause of cancer-related death. Surgery and external radiation, chemotherapy, or a combination of strategies are the cornerstone of therapy for EC patients. However, adjuvant treatment strategies face certain drawbacks, such as resistance to chemotherapeutic drugs; therefore, it is imperative to explore innovative therapeutic strategies to improve the prognosis of EC. With the development of pathology and pathophysiology, several biological targets associated with EC have been identified, including PI3K/Akt/mTOR, PARP, GSK-3β, STAT-3, and VEGF. In this review, we summarize the progress of small molecule targeted therapies in terms of both basic research and clinical trials and provide cases of small molecules combined with fluorescence properties in the clinical applications of integrated diagnosis and treatment. We hope that this review will facilitate the further understanding of the regulatory mechanism governing the dysregulation of oncogenic signaling in EC and provide insights into the possible future directions of targeted therapeutic regimens for EC treatment by developing new agents with fluorescence properties for the clinical applications of integrated diagnosis and treatment.

Exosomes derived from rapamycin-treated 4T1 breast cancer cells induced polarization of macrophages to M1 phenotype

M2 macrophages are the most prevalent type in the tumor microenvironment and their polarization to M1 type can be used as a potential cancer immunotherapy. Here, we investigated the role of tumor microenvironment and particularly purified exosomes in M2 to M1 macrophage polarization. Rapamycin treatment on triple-negative breast cancer cells (TNBC) was performed. Tumor cells-derived exosomes (called texosomes) were isolated and characterized using scanning electron microscopy, transmission electron microscopy, dynamic light scattering, high-performance liquid chromatography, Fourier transform infrared, and Western blot assays. M2 mouse peritoneal macrophages were treated with rapamycin or rapamycin-texosome. Then, M1/M2 phenotype-specific marker genes and proteins were measured to assess the degree of M2 to M1 polarization. Finally, nitric oxide (NO) production, phagocytosis, and efferocytosis assays were assessed to verify the functionality of the polarized macrophages. Purified rapamycin-texosomes significantly increased the expression of the M1 markers (Irf5, Nos2, and CD86) and decreased M2 markers (Arg, Ym1, and CD206). In addition, the levels of M1-specific cytokines tumor necrosis factor alpha and interleukin 1β (IL-1β) were increased, whereas the levels of M2 specific cytokines IL-10 and transforming growth factor beta were declined. Furthermore, texosome treatment increased NO concentration and phagocytosis and decreased efferocytosis indicating M1 polarization. These findings suggest rapamycin-texosomes can induce M2 to M1 macrophages polarization as a potential immunotherapy for TNBC.

The autophagy inducer SMER28 attenuates microtubule dynamics mediating neuroprotection

SMER28 originated from a screen for small molecules that act as modulators of autophagy. SMER28 enhanced the clearance of autophagic substrates such as mutant huntingtin, which was additive to rapamycin-induced autophagy. Thus, SMER28 was established as a positive regulator of autophagy acting independently of the mTOR pathway, increasing autophagosome biosynthesis and attenuating mutant huntingtin-fragment toxicity in cellular- and fruit fly disease models, suggesting therapeutic potential. Despite many previous studies, molecular mechanisms mediating SMER28 activities and its direct targets have remained elusive. Here we analyzed the effects of SMER28 on cells and found that aside from autophagy induction, it significantly stabilizes microtubules and decelerates microtubule dynamics. Moreover, we report that SMER28 displays neurotrophic and neuroprotective effects at the cellular level by inducing neurite outgrowth and protecting from excitotoxin-induced axon degeneration. Finally, we compare the effects of SMER28 with other autophagy-inducing or microtubule-stabilizing drugs: whereas SMER28 and rapamycin both induce autophagy, the latter does not stabilize microtubules, and whereas both SMER28 and epothilone B stabilize microtubules, epothilone B does not stimulate autophagy. Thus, the effect of SMER28 on cells in general and neurons in particular is based on its unique spectrum of bioactivities distinct from other known microtubule-stabilizing or autophagy-inducing drugs.

Paclitaxel: Application in Modern Oncology and Nanomedicine-Based Cancer Therapy

Paclitaxel is a broad-spectrum anticancer compound, which was derived mainly from a medicinal plant, in particular, from the bark of the yew tree Taxus brevifolia Nutt. It is a representative of a class of diterpene taxanes, which are nowadays used as the most common chemotherapeutic agent against many forms of cancer. It possesses scientifically proven anticancer activity against, e.g., ovarian, lung, and breast cancers. The application of this compound is difficult because of limited solubility, recrystalization upon dilution, and cosolvent-induced toxicity. In these cases, nanotechnology and nanoparticles provide certain advantages such as increased drug half-life, lowered toxicity, and specific and selective delivery over free drugs. Nanodrugs possess the capability to buildup in the tissue which might be linked to enhanced permeability and retention as well as enhanced antitumour influence possessing minimal toxicity in normal tissues. This article presents information about paclitaxel, its chemical structure, formulations, mechanism of action, and toxicity. Attention is drawn on nanotechnology, the usefulness of nanoparticles containing paclitaxel, its opportunities, and also future perspective. This review article is aimed at summarizing the current state of continuous pharmaceutical development and employment of nanotechnology in the enhancement of the pharmacokinetic and pharmacodynamic features of paclitaxel as a chemotherapeutic agent.

Optimization and Pharmacokinetic Evaluation of Synergistic Fenbendazole and Rapamycin Co-Encapsulated in Methoxy Poly(Ethylene Glycol)-b-Poly(Caprolactone) Polymeric Micelles

Purpose

We aimed to develop a nanocarrier formulation incorporating fenbendazole (FEN) and rapamycin (RAPA) with strong efficacy against A549 cancer cells. As FEN and RAPA are poorly soluble in water, it is difficult to apply them clinically in vivo. Therefore, we attempted to resolve this problem by encapsulating these drugs in polymeric micelles.

Methods

We evaluated drug synergy using the combination index (CI) values of various molar ratios of FEN and RAPA. We formed and tested micelles composed of different polymers. Moreover, we conducted cytotoxicity, stability, release, pharmacokinetic, and biodistribution studies to investigate the antitumor effects of FEN/RAPA-loaded mPEG-b-PCL micelles.

Results

We selected mPEG-b-PCL-containing FEN and RAPA at a molar ratio of 1:2 because these particles were consistent in size and had high encapsulation efficiency (EE, %) and drug loading (DL, %) capacity. The in vitro cytotoxicity was assessed for various FEN, RAPA, and combined FEN/RAPA formulations. After long-term exposures, both the solutions and the micelles had similar efficacy against A549 cancer cells. The in vivo pharmacokinetic study revealed that FEN/RAPA-loaded mPEG-b-PCL micelles had a relatively higher area under the plasma concentration–time curve from 0 to 2 h (AUC_{0–2 h}) and 0 to 8 h (AUC_{0–8 h}) and plasma concentration at time zero (C_o) than that of the FEN/RAPA solution. The in vivo biodistribution assay revealed that the IV injection of FEN/RAPA-loaded mPEG-b-PCL micelles resulted in lower pulmonary FEN concentration than the IV injection of the FEN/RAPA solution.

Conclusion

When FEN and RAPA had a 1:2 molar ratio, they showed synergism. Additionally, using data from in vitro cytotoxicity, synergism between a 1:2 molar ratio of FEN and RAPA was observed in the micelle formulation. The FEN/RAPA-loaded mPEG-b-PCL micelle had enhanced bioavailability than the FEN/RAPA solution.

Novel Benzenesulfonate Scaffolds with a High Anticancer Activity and G2/M Cell Cycle Arrest

Sulfonates, unlike their derivatives, sulphonamides, have rarely been investigated for their anticancer activity. Unlike the well-known sulphonamides, esters are mainly used as convenient intermediates in a synthesis. Here, we present the first in-depth investigation of quinazoline sulfonates. A small series of derivatives were synthesized and tested for their anticancer activity. Based on their structural similarity, these compounds resemble tyrosine kinase inhibitors and the p53 reactivator CP-31398. Their biological activity profile, however, was more related to sulphonamides because there was a strong cell cycle arrest in the G2/M phase. Further investigation revealed a multitargeted mechanism of the action that corresponded to the p53 protein status in the cell. Although the compounds expressed a high submicromolar activity against leukemia and colon cancers, pancreatic cancer and glioblastoma were also susceptible. Apoptosis and autophagy were confirmed as the cell death modes that corresponded with the inhibition of metabolic activity and the activation of the p53-dependent and p53-independent pathways. Namely, there was a strong activation of the p62 protein and GADD44. Other proteins such as cdc2 were also expressed at a higher level. Moreover, the classical caspase-dependent pathway in leukemia was observed at a lower concentration, which again confirmed a multitargeted mechanism. It can therefore be concluded that the sulfonates of quinazolines can be regarded as promising scaffolds for developing anticancer agents.

Inhibition of PFKFB3 induces cell death and synergistically enhances chemosensitivity in endometrial cancer

The advanced or recurrent endometrial cancer (EC) has a poor prognosis because of chemoresistance. 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a glycolytic enzyme, is overexpressed in a variety of human cancers and plays important roles in promoting tumor cell growth. Here, we showed that high expression of PFKFB3 in EC cell lines is associated with chemoresistance. Pharmacological inhibition of PFKFB3 with PFK158 and or genetic downregulation of PFKFB3 dramatically suppressed cell proliferation and enhanced the sensitivity of EC cells to carboplatin (CBPt) and cisplatin (Cis). Moreover, PFKFB3 inhibition resulted in reduced glucose uptake, ATP production, and lactate release. Notably, we found that PFK158 with CBPt or Cis exerted strong synergistic antitumor activity in chemoresistant EC cell lines, HEC-1B and ARK-2 cells. We also found that the combination of PFK158 and CBPt/Cis induced apoptosis- and autophagy-mediated cell death through inhibition of the Akt/mTOR signaling pathway. Mechanistically, we found that PFK158 downregulated the CBPt/Cis-induced upregulation of RAD51 expression and enhanced CBPt/Cis-induced DNA damage as demonstrated by an increase in γ-H2AX levels in HEC-1B and ARK-2 cells, potentially revealing a means to enhance PFK158-induced chemosensitivity. More importantly, PFK158 treatment, either as monotherapy or in combination with CBPt, led to a marked reduction in tumor growth in two chemoresistant EC mouse xenograft models. These data suggest that PFKFB3 inhibition alone or in combination with standard chemotherapy may be used as a novel therapeutic strategy for improved therapeutic efficacy and outcomes of advanced and recurrent EC patients.

High-throughput, microscope-based sorting to dissect cellular heterogeneity

Microscopy is a powerful tool for characterizing complex cellular phenotypes, but linking these phenotypes to genotype or RNA expression at scale remains challenging. Here, we present Visual Cell Sorting, a method that physically separates hundreds of thousands of live cells based on their visual phenotype. Automated imaging and phenotypic analysis directs selective illumination of Dendra2, a photoconvertible fluorescent protein expressed in live cells; these photoactivated cells are then isolated using fluorescence-activated cell sorting. First, we use Visual Cell Sorting to assess hundreds of nuclear localization sequence variants in a pooled format, identifying variants that improve nuclear localization and enabling annotation of nuclear localization sequences in thousands of human proteins. Second, we recover cells that retain normal nuclear morphologies after paclitaxel treatment, and then derive their single-cell transcriptomes to identify pathways associated with paclitaxel resistance in cancers. Unlike alternative methods, Visual Cell Sorting depends on inexpensive reagents and commercially available hardware. As such, it can be readily deployed to uncover the relationships between visual cellular phenotypes and internal states, including genotypes and gene expression programs.

The role of RICTOR amplification in targeted therapy and drug resistance

The emergence of tyrosine kinase inhibitors (TKIs) has changed the current treatment paradigm and achieved good results in recent decades. However, an increasing number of studies have indicated that the complex network of receptor tyrosine kinase (RTK) co-activation could influence the characteristic phenotypes of cancer and the tumor response to targeted treatments. One of strategies to blocking RTK co-activation is targeting the downstream factors of RTK, such as PI3K-AKT-mTOR pathway. RICTOR, a core component of mTORC2, acts as a key effector molecule of the PI3K-AKT pathway; its amplification is often associated with poor clinical outcomes and resistance to TKIs. Here, we discuss the biology of RICTOR in tumor and the prospects of targeting RICTOR as a complementary therapy to inhibit RTK co-activation.

Metformin Enhances Nomegestrol Acetate Suppressing Growth of Endometrial Cancer Cells and May Correlate to Downregulating mTOR Activity In Vitro and In Vivo

This study investigated the effect of a novel progestin and its combination with metformin on the growth of endometrial cancer (EC) cells. Inhibitory effects of four progestins, including nomegestrol acetate (NOMAC), medroxyprogesterone acetate, levonorgestrel, and cyproterone acetate, were evaluated in RL95-2, HEC-1A, and KLE cells using cell counting kit-8 assay. Flow cytometry was performed to detect cell cycle and apoptosis. The activity of Akt (protein kinase B), mTOR (mammalian target of rapamycin) and its downstream substrates 4EBP1 (4E-binding protein 1) and eIF4G (Eukaryotic translation initiation factor 4G) were assayed by Western blotting. Nude mice were used to assess antitumor effects in vivo. NOMAC inhibited the growth of RL95-2 and HEC-1A cells, accompanied by arresting the cell cycle at G0/G1 phase, inducing apoptosis, and markedly down-regulating the level of phosphorylated mTOR/4EBP1/eIF4G in both cell lines (p < 0.05). Metformin significantly increased the inhibitory effect of and apoptosis induced by NOMAC and strengthened the depressive effect of NOMAC on activity of mTOR and its downstream substrates, compared to their treatment alone (p < 0.05). In xenograft tumor tissues, metformin (100 mg/kg) enhanced the suppressive effect of NOMAC (100 mg/kg) on mTOR signaling and increased the average concentration of NOMAC by nearly 1.6 times compared to NOMAC treatment alone. Taken together, NOMAC suppressing the growth of EC cells likely correlates to down-regulating the activity of the mTOR pathway and metformin could strengthen this effect. Our findings open a new window for the selection of progestins in hormone therapy of EC.

mTOR Signaling Pathway in Cancer Targets Photodynamic Therapy In Vitro

The Mechanistic or Mammalian Target of Rapamycin (mTOR) is a major signaling pathway in eukaryotic cells belonging to the P13K-related kinase family of the serine/threonine protein kinase. It has been established that mTOR plays a central role in cellular processes and implicated in various cancers, diabetes, and in the aging process with very poor prognosis. Inhibition of the mTOR pathway in the cells may improve the therapeutic index in cancer treatment. Photodynamic therapy (PDT) has been established to selectively eradicate neoplasia at clearly delineated malignant lesions. This review highlights recent advances in understanding the role or regulation of mTOR in cancer therapy. It also discusses how mTOR currently contributes to cancer as well as future perspectives on targeting mTOR therapeutically in cancer in vitro.

Synergistic interaction of gemcitabine and paclitaxel by modulating acetylation and polymerization of tubulin in non-small cell lung cancer cell lines

Background: The combination of gemcitabine (GEM) and paclitaxel (PTX) was appealing for clinical exploration due to different mechanisms of action and partially non-overlapping toxicities.

Purpose: The aim of this study was to elucidate a potential effect of this combination on the proliferation of two non-small cell lung cancer (NSCLC) cell lines, A549 and H520.

Materials and methods: Cell lines were treated with GEM and PTX for 48 hours to evaluate the half maximal inhibitory concentration (IC50). To determine the combination index (CI), cell lines were exposed to GEM and PTX, in a constant ratio of IC50, by various combination treatments. GEM`s effect on tubulin was assessed by western blotting and immunofluorescent staining. GEM was combined with nanoparticle albumin-bound-paclitaxel (NP) in evaluating tumor growth inhibition.

Results: The IC50 of GEM and PTX in A549 and H520 were 6.6 nM and 46.1 nM, and 1.35 nM and 7.59 nM, respectively. Among the sequences explored (GEM→PTX, PTX→GEM, and GEM plus PTX simultaneously [GEM+PTX]), GEM→PTX produced a mean CI <1 in both cell lines. Western blotting and immunofluorescent staining revealed the intention expressions of acetylated tubulin protein and enhancement of tubulin polymerization within GEM→PTX group. A combination order GEM→NP also worked synergistically to suppress tumor growth.

Conclusion: The GEM→PTX sequence may represent a promising candidate regimen for the treatment of NSLCL.

3D Printing of Poloxamer 407 Nanogel Discs and Their Applications in Adjuvant Ovarian Cancer Therapy

Nanogels are attractive biocompatible materials that enable local delivery of multiple drugs. In this study, we demonstrated that 3D printing technology could be used to precisely construct nanogel discs carrying paclitaxel and rapamycin. 3D-printed nanogel disc rounds (12 mm diameter × 1 mm thickness) carrying paclitaxel and rapamycin evaded premature gelation during storage and the initial burst release of the drugs in the dissolution medium. In vivo 3D-printed nanogel discs permitted successful intraperitoneal delivery of paclitaxel and rapamycin in ES-2-luc ovarian-cancer-bearing xenograft mice. They were also shown to be therapeutically effective and capable of preventing postsurgical peritoneal adhesions in the treated xenograft mice.

Concentration-dependent effects of rapamycin on proliferation, migration and apoptosis of endothelial cells in human venous malformation

Rapamycin has been reported to be immunosuppressive and anti-proliferative towards vascular endothelial and smooth muscle cells. The purpose of the present study was to investigate the effects of rapamycin on the biological behaviors of endothelial cells that have been separated from the deformed vein in human venous malformation (VM). Cellular morphology was observed using inverted microscopy. An MTT assay was performed to measure the cell viability at different concentrations of rapamycin and different time points. Cell apoptosis and migration were detected using a terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay and a wound-healing assay, respectively. At 48 and 72 h, rapamycin inhibited proliferation of human VM endothelial cells, with the effects becoming more pronounced with increasing concentration. Only rapamycin at a concentration of 1,000 ng/ml had a significant effect at 24 h in repressing proliferation. At 48 h, compared with the blank group, the majority of cells maintained a clear nuclear boundary and a regular shape following treatment with 1 ng/ml rapamycin; 10 and 100 ng/ml rapamycin caused desquamation and rounded shape; and 1,000 ng/ml rapamycin caused even more marked desquamation, rounded shape and necrosis. Rapamycin at concentrations of 1, 10, 100 and 1,000 ng/ml reduced cell viability, increased the number of apoptotic cells and suppressed the migration capacity of human VM endothelial cells, and the effects became more pronounced with increasing concentration, when compared with the blank group. These findings provide evidence that rapamycin induces apoptosis and inhibits proliferation and migration of human VM endothelial cells in a concentration-dependent manner.

Chemoresistance and targeting of growth factors/cytokines signalling pathways: towards the development of effective therapeutic strategy for endometrial cancer

Endometrial cancer tends to be an aggressive malignancy. Although the disease prognosis can be good at the early stages of disease, the advanced condition is not curable. Chemotherapy regimens and hormone-based therapy in combination with surgery are major approaches for the management of endometrial cancers. However, intrinsic chemoresistance reduces the success rate and increases the possibility of disease relapse. Investigation of underlying mechanisms revealed altered activation of PI3K/AKT, MAPK, fibroblast growth factor (FGF), mTOR and WNT pathways and reduced gene expression of tumor suppressor p53 in recurrent endometrial cancer. A PTEN mutation, deletion or degradation induces positive p-AKT expression, while PI3K knock-down increases the level of pro-apoptotic proteins and decreases the level of anti-apoptotic ones in cancerous cells. Additionally, RAS proteins trigger both the RAF-MEK-ERK and PI3K-PTEN-AKT signalling mechanisms, thus conferring resistance to anti-tumor agents. FGF up-regulates angiogenesis via receptor-mediated tyrosine kinase activation. Single nucleotide polymorphism, gene amplification or missense mutations of FGFR2 are associated with endometrial cancer. The mTOR complex integrates the nutrient and mitogen signals via AMPKs, S6 kinase 1 (S6K1) and eukaryotic initiation factors, causing unrestricted endometrial cellular proliferation. WNT signalling molecules, such as frizzled receptors, β-catenin, PORCN, RSPO3 and DKK1 undergo dysregulation, and drugs targeting these pathways are under clinical trials in patients with endometrial cancer. Common therapies for endometrial tumor include platinum-based anti-neoplastics, taxanes, nucleoside analogues, immune modulators, FGFR and tyrosine kinase inhibitors, small-molecule mTOR inhibitors and drugs that trigger cell cycle arrest in the G1 phase. Taken together, the current review elucidates the mechanism underlying endometrial cancer, existing therapies and chemoresistance, and points towards the need for novel therapeutics that may promote disease-free survival.

Increased efficacy of metformin corresponds to differential metabolic effects in the ovarian tumors from obese versus lean mice

Obesity is a significant risk factor for ovarian cancer (OC) and associated with worse outcomes for this disease. We assessed the anti-tumorigenic effects of metformin in human OC cell lines and a genetically engineered mouse model of high grade serous OC under obese and lean conditions. Metformin potently inhibited growth in a dose-dependent manner in all four human OC cell lines through AMPK/mTOR pathways. Treatment with metformin resulted in G1 arrest, induction of apoptosis, reduction of invasion and decreased hTERT expression. In the K18-gT₁₂₁^+/-; p53^fl/fl; Brca1^fl/fl (KpB) mouse model, metformin inhibited tumor growth in both lean and obese mice. However, in the obese mice, metformin decreased tumor growth by 60%, whereas tumor growth was only decreased by 32% in the lean mice (p=0.003) compared to vehicle-treated mice. The ovarian tumors from obese mice had evidence of impaired mitochondrial complex 2 function and energy supplied by omega fatty acid oxidation rather than glycolysis as compared to lean mice, as assessed by metabolomic profiling. The improved efficacy of metformin in obesity corresponded with inhibition of mitochondrial complex 1 and fatty acid oxidation, and stimulation of glycolysis in only the OCs of obese versus lean mice. In conclusion, metformin had anti-tumorigenic effects in OC cell lines and the KpB OC pre-clinical mouse model, with increased efficacy in obese versus lean mice. Detected metabolic changes may underlie why ovarian tumors in obese mice have heightened susceptibility to metformin.

An overview of rapamycin: from discovery to future perspectives

Rapamycin is an immunosuppressive metabolite produced from several actinomycete species. Besides its immunosuppressive activity, rapamycin and its analogs have additional therapeutic potentials, including antifungal, antitumor, neuroprotective/neuroregenerative, and lifespan extension activities. The core structure of rapamycin is derived from (4R,5R)-4,5-dihydrocyclohex-1-ene-carboxylic acid that is extended by polyketide synthase. The resulting linear polyketide chain is cyclized by incorporating pipecolate and further decorated by post-PKS modification enzymes. Herein, we review the discovery and biological activities of rapamycin as well as its mechanism of action, mechanistic target, biosynthesis, and regulation. In addition, we introduce the many efforts directed at enhancing the production of rapamycin and generating diverse analogs and also explore future perspectives in rapamycin research. This review will also emphasize the remarkable pilot studies on the biosynthesis and production improvement of rapamycin by Dr. Demain, one of the world's distinguished scientists in industrial microbiology and biotechnology.

The anti-tumor activator sMEK1 and paclitaxel additively decrease expression of HIF-1α and VEGF via mTORC1-S6K/4E-BP-dependent signaling pathways

Recently, we found that sMEK1 effectively regulates pro-apoptotic activity when combined with a traditional chemotherapeutic drug. Therefore, combinational therapeutic strategies targeting critical molecular and cellular mechanisms are urgently required. In this present work, we evaluated whether sMEK1 enhanced the pro-apoptotic activity of chemotherapeutic drugs in ovarian carcinoma cells. Combined with a chemotherapeutic drug, sMEK1 showed an additive effect on the suppression of ovarian cancer cell growth by inducing cell cycle arrest and apoptosis and regulating related gene expression levels or protein activities. In addition, the phosphoinositide-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was strongly inhibited by the combined treatment, showing de-repression of the tuberous sclerosis complex (TSC) and suppression of ras homolog enriched in the brain (Rheb) and mTOR and raptor in aggressive ovarian carcinoma cells and mouse xenograft models. Treatment with sMEK1 and paclitaxel reduced phosphorylation of ribosomal S6 kinase (S6K) and 4E-binding protein (4E-BP), two critical downstream targets of the mTOR-signaling pathway. Furthermore, both sMEK1 and paclitaxel significantly inhibited the expression of signaling components downstream of S6K/4E-BP, such as hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF), both in vitro and in vivo. Therefore, our data suggest that the combination of sMEK1 and paclitaxel is a promising and effective targeted therapy for chemotherapy-resistant or recurrent ovarian cancers.

Knockdown of hTERT and Treatment with BIBR1532 Inhibit Cell Proliferation and Invasion in Endometrial Cancer Cells

Telomerase activity and expression of the catalytic protein hTERT are associated with cell proliferation and advanced stage in endometrial cancer. Our objective was to evaluate the effect of inhibition of hTERT by siRNA and BIBR1532 on cell growth, apoptosis and invasion in endometrial cancer cells. Knockdown of hTERT or treatment of the cells with BIBR1532 decreased telomerase activity, inhibited cell proliferation, induced apoptosis, and reduced cell invasion in Ishikawa and ECC-1 cells. Either hTERT siRNA or BIBR1532 in combination with paclitaxel promoted a synergistic inhibitory effect on cell growth through induction of Annexin V expression and a remarkable reduction in cell invasion through reduction of protein expression of MMP9, MMP2, and MMP3. Increased telomerase activity and hTERT protein expression by transfections enhanced the protein expression of MMPs and increased the cell invasion ability. BIBR1532 significantly antagonized cell invasion induced by increased hTERT expression. These findings suggest that telomerase and hTERT facilitate cell invasion via MMP family in human endometrial cancer cells.

MicroRNA-199a-3p suppresses glioma cell proliferation by regulating the AKT/mTOR signaling pathway

Glioma has been investigated for decades, but the prognosis remains poor because of rapid proliferation, its aggressive potential, and its resistance to chemotherapy or radiotherapy. The mammalian target of rapamycin (mTOR) is highly expressed and regulates cellular proliferation and cell growth. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene transcription and translation via up-regulating or down-regulating the levels of miRNAs. This study was conducted to explore the molecular functions of miR-199a-3p in glioma. We detected the expression of miR-199a-3p in glioma samples by quantitative PCR (qPCR). Then, we transfected the U87 and U251 cell lines with miR-199a-3p. Cellular proliferation, invasion, and apoptosis were assessed to explain the function of miR-199a-3p. PCR confirmed that the expression of miR-199a-3p was lower in glioma samples combined with normal brain tissues. The over-expression of miR-199a-3p might target mTOR and restrained cellular growth and proliferation but not invasive and apoptosis capability. Results indicated that cellular proliferation was inhibited to regulate the AKT/mTOR signaling pathway by elevating levels of miR-199a-3p. MiR-199a-3p in glioma cell lines has effects similar to the tumor suppressor gene on cellular proliferation via the AKT/mTOR signaling pathway.

Self-assembled micelles of amphiphilic PEGylated rapamycin for loading paclitaxel and resisting multidrug resistant cancer cells†Electronic supplementary information (ESI) available: Chemicals and reagents, detailed experimental procedures for materials synthesis, characterization, cellular evaluations and supporting figures and tables. See DOI: 10.1039/c4tb01633eClick here for additional data file

A paclitaxel loaded PEGylated rapamycin micelle effectively bypasses the resistance mechanism, allowing for potent treatment of multidrug resistant cancer cells.

Self-assembled micelles of amphiphilic PEG–rapamycin conjugates loaded with paclitaxel have been developed for co-delivery and simultaneous intracellular release of paclitaxel and rapamycin, bypassing the cancer cell drug resistant mechanism and maximising the synergy of dual-drug combinational therapy. This novel nanomedicine offers 20-fold improved potency over free paclitaxel against a model multidrug resistant human breast cancer cell.

Dual mTORC1/2 inhibition in a preclinical xenograft tumor model of endometrial cancer

OBJECTIVES

Up to 70% of endometrioid endometrial cancers carry PTEN gene deletions that can upregulate mTOR activity. Investigational mTOR kinase inhibitors may provide a novel therapeutic approach for these tumors. Using a xenograft tumor model of endometrial cancer, we assessed the activity of mTOR and downstream effector proteins in the mTOR translational control pathway after treatment with a dual mTOR complex 1 and 2 (mTORC1/2) catalytic inhibitor (PP242) compared to that of an allosteric mTOR complex 1 (mTORC1) inhibitor (everolimus, RAD001).

METHODS

Grade 3 endometrioid endometrial cancer cells (AN3CA) were xenografted into nude mice. Animals were treated with PP242, PP242 and carboplatin, carboplatin, RAD001, and RAD001 and carboplatin. Mean tumor volume was compared across groups by ANOVA. Immunoblot analysis was performed to assess mTORC1/2 activity using P-Akt, P-S6 and P-4E-BP1.

RESULTS

The mean tumor volume of PP242+carboplatin was significantly lower than in all other treatment groups, P < 0.001 (89% smaller). The RAD001+carboplatin group was also smaller, but this did not reach statistical significance (P = 0.097). Immunoblot analysis of tumor lysates treated with PP242 demonstrated inhibition of activated P-Akt.

CONCLUSIONS

Catalytic mTORC1/2 inhibition demonstrates clear efficacy in tumor growth control that is enhanced by the addition of a DNA damage agent, carboplatin. Targeting mTORC1/2 leads to inhibition of Akt activation and strong downregulation of effectors of mTORC1, resulting in downregulation of protein synthesis. Based on this study, mTORC1/2 kinase inhibitors warrant further investigation as a potential treatment for endometrial cancer.

Molecular alterations of PI3K/Akt/mTOR pathway: a therapeutic target in endometrial cancer

It is well established that the PI3K/Akt/mTOR pathway plays a central role in cell growth and proliferation. It has also been suggested that its deregulation is associated with cancer. Genetic alterations, involving components of this pathway, are often encountered in endometrial cancers. Understanding and identifying the rate-limiting steps of this pathway would be crucial for the development of novel therapies against endometrial cancer. This paper reviews alterations in the PI3K/Akt pathway, which could possibly contribute to the development of endometrial cancer. In addition, potential therapeutic targets of this pathway with emphasis on the mTOR inhibitors are also presented.

Correlation between TGF-β1 expression and rapamycin-induced liver fibrosis improvement in rats

AIM: To investigate the role of transformation growth factor-β1 (TGF-β1) in the therapeutic effect of rapamycin on liver fibrosis in rats.

METHODS: Rats were divided into three groups: a normal control group, a liver fibrosis model group and a rapamycin treatment group. Rats were treated with carbon tetrachloride to induce liver fibrosis. Eight weeks after treatment, liver histological changes and the expression of TGF-β1 in the liver were detected. In addition, serum TGF-β1 levels were dynamically monitored.

RESULTS: After immunohistochemical and HE staining, image-pro plus 6 image analysis software was used to analyze the integrated absorbance (IA). The IA values were 9891.4 ± 1725.7, 104239.9 ± 20890.6, and 27853.6 ± 2031 in the normal control group, liver fibrosis model group and rapamycin treatment group, respectively. The expression of TGF-β1 in liver tissue was significantly different among the three groups (P < 0.01).

CONCLUSION: Rapamycin can significantly reduce the levels of TGF-β1 in liver tissue and serum, which may be involved in the therapeutic effect of rapamycin on liver fibrosis.

Cancer-associated fibroblasts promote proliferation of endometrial cancer cells

Endometrial cancer is the most commonly diagnosed gynecologic malignancy worldwide; yet the tumor microenvironment, especially the fibroblast cells surrounding the cancer cells, is poorly understood. We established four primary cultures of fibroblasts from human endometrial cancer tissues (cancer-associated fibroblasts, CAFs) using antibody-conjugated magnetic bead isolation. These relatively homogenous fibroblast cultures expressed fibroblast markers (CD90, vimentin and alpha-smooth muscle actin) and hormonal (estrogen and progesterone) receptors. Conditioned media collected from CAFs induced a dose-dependent proliferation of both primary cultures and cell lines of endometrial cancer in vitro (175%) when compared to non-treated cells, in contrast to those from normal endometrial fibroblast cell line (51%) (P<0.0001). These effects were not observed in fibroblast culture derived from benign endometrial hyperplasia tissues, indicating the specificity of CAFs in affecting endometrial cancer cell proliferation. To determine the mechanism underlying the differential fibroblast effects, we compared the activation of PI3K/Akt and MAPK/Erk pathways in endometrial cancer cells following treatment with normal fibroblasts- and CAFs-conditioned media. Western blot analysis showed that the expression of both phosphorylated forms of Akt and Erk were significantly down-regulated in normal fibroblasts-treated cells, but were up-regulated/maintained in CAFs-treated cells. Treatment with specific inhibitors LY294002 and U0126 reversed the CAFs-mediated cell proliferation (P<0.0001), suggesting for a role of these pathways in modulating endometrial cancer cell proliferation. Rapamycin, which targets a downstream molecule in PI3K pathway (mTOR), also suppressed CAFs-induced cell proliferation by inducing apoptosis. Cytokine profiling analysis revealed that CAFs secrete higher levels of macrophage chemoattractant protein (MCP)-1, interleukin (IL)-6, IL-8, RANTES and vascular endothelial growth factor (VEGF) than normal fibroblasts. Our data suggests that in contrast to normal fibroblasts, CAFs may exhibit a pro-tumorigenic effect in the progression of endometrial cancer, and PI3K/Akt and MAPK/Erk signaling may represent critical regulators in how endometrial cancer cells respond to their microenvironment.

Targeted inhibition of mammalian target of rapamycin (mTOR) enhances radiosensitivity in pancreatic carcinoma cells

The mammalian target of rapamycin (mTOR) is a protein kinase that regulates protein translation, cell growth, and apoptosis. Rapamycin (RPM), a specific inhibitor of mTOR, exhibits potent and broad in vitro and in vivo antitumor activity against leukemia, breast cancer, and melanoma. Recent studies showing that RPM sensitizes cancers to chemotherapy and radiation therapy have attracted considerable attention. This study aimed to examine the radiosensitizing effect of RPM in vitro, as well as its mechanism of action. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and colony formation assay showed that 10 nmol/L to 15 nmol/L of RPM had a radiosensitizing effects on pancreatic carcinoma cells in vitro. Furthermore, a low dose of RPM induced autophagy and reduced the number of S-phase cells. When radiation treatment was combined with RPM, the PC-2 cell cycle arrested in the G2/M phase of the cell cycle. Complementary DNA (cDNA) microarray and reverse transcription polymerase chain reaction (RT-PCR) revealed that the expression of DDB1, RAD51, and XRCC5 were downregulated, whereas the expression of PCNA and ABCC4 were upregulated in PC-2 cells. The results demonstrated that RPM effectively enhanced the radiosensitivity of pancreatic carcinoma cells.

Ridaforolimus as a single agent in advanced endometrial cancer: results of a single-arm, phase 2 trial

Background:

This open-label, multicentre, phase 2 trial evaluated the efficacy and tolerability of the mammalian target of rapamycin inhibitor ridaforolimus in women with advanced endometrial cancer.

Methods:

Women with measurable recurrent or persistent endometrial cancer and documented disease progression were treated with ridaforolimus 12.5 mg intravenously once daily for 5 consecutive days every 2 weeks in a 4-week cycle. The primary end point was clinical benefit response, defined as an objective response or prolonged stable disease of 16 weeks or more.

Results:

In all, 45 patients were treated with single-agent ridaforolimus. Clinical benefit was achieved by 13 patients (29%), including 5 (11%) with confirmed partial responses and 8 (18%) with prolonged stable disease. All patients with clinical benefit response received ridaforolimus for more than 4 months. In this heavily pretreated population, the 6-month progression-free survival was 18%. Ridaforolimus was generally well tolerated: adverse events were predictable and manageable, consistent with prior studies in other malignancies. Overall, the most common adverse events were diarrhoea (58%) and mouth sores (56%); most common grade 3 or higher adverse events were anaemia (27%) and hyperglycaemia (11%).

Conclusion:

Single-agent ridaforolimus has antitumor activity and acceptable tolerability in advanced endometrial cancer patients. Further clinical evaluation of ridaforolimus is warranted.

Antitumor effects of rapamycin in pancreatic cancer cells by inducing apoptosis and autophagy

Rapamycin (Rapa), an inhibitor of mammalian target of Rapamycin (mTOR), is an immunosuppressive agent that has anti-proliferative effects on some tumors. This study aims to investigate the effects of Rapa suppressing proliferation of pancreatic carcinoma PC-2 cells in vitro and its molecular mechanism involved in antitumor activities. MTT assays showed that the inhibition of proliferation of PC-2 cells in vitro was in a time- and dose-dependent manner. By using transmission electron microscopy, apoptosis bodies and formation of abundant autophagic vacuoles were observed in PC-2 cells after Rapa treatment. Flow cytometry assays also showed Rapa had a positive effect on apoptosis. MDC staining showed that the fluorescent density was higher and the number of MDC-labeled particles in PC-2 cells was greater in the Rapa treatment group than in the control group. RT-PCR revealed that the expression levels of p53, Bax and Beclin 1 were up-regulated in a dose-dependent manner, indicating that Beclin 1 was involved in Rapa induced autophagy and Rapa induced apoptosis as well as p53 up-regulation in PC-2 cells. The results demonstrated that Rapa could effectively inhibit proliferation and induce apoptosis and autophagy in PC-2 cells.

Utility of a PI3K/mTOR inhibitor (NVP-BEZ235) for thyroid cancer therapy

BACKGROUND

We assessed the utility of the dual PI3K/mTOR inhibitor NVP-BEZ235 (BEZ235) as single agent therapy and in combination with conventional chemotherapy for thyroid cancer.

METHODOLOGY/PRINCIPAL FINDINGS

Eight cell lines from four types of thyroid cancer (papillary, follicular, anaplastic, medullary) were studied. The cytotoxicity of BEZ235 and five conventional chemotherapeutic agents alone and in combination was measured using LDH assay. Quantitative western blot assessed expression of proteins associated with cell cycle, apoptosis and signaling pathways. Cell cycle distribution and apoptosis were measured by flow cytometry. Murine flank anaplastic thyroid cancers (ATC) were treated with oral BEZ235 daily. We found that BEZ235 effectively inhibited cell proliferation of all cancer lines, with ATC exhibiting the greatest sensitivity. BEZ235 consistently inactivated signaling downstream of mTORC1. BEZ235 generally induced cell cycle arrest at G0/G1 phase, and also caused apoptosis in the most sensitive cell lines. Baseline levels of p-S6 ribosomal protein (Ser235/236) and p27 correlated with BEZ235 sensitivity. Growth of 8505C ATC xenograft tumors was inhibited with BEZ235, without any observed toxicity. Combination therapy of BEZ235 and paclitaxel consistently demonstrated synergistic effects against ATC in vitro.

CONCLUSIONS

BEZ235 as a single therapeutic agent inhibits thyroid cancer proliferation and has synergistic effects in combination with paclitaxel in treating ATC. These findings encourage future clinical trials using BEZ235 for patients with this fatal disease.

Antitumor activity of Triolimus: a novel multidrug-loaded micelle containing Paclitaxel, Rapamycin, and 17-AAG

Triolimus is a first-in-class, multidrug-loaded micelle containing paclitaxel, rapamycin, and 17-AAG. In this study, we examine the antitumor mechanisms of action, efficacy, and toxicity of Triolimus in vitro and in vivo. In vitro cytotoxicity testing of Triolimus was conducted using two aggressive adenocarcinomas including the lung cancer cell line, A549, and breast cancer cell line, MDA-MB-231. The three-drug combination of paclitaxel, rapamycin, and 17-AAG displayed potent cytotoxic synergy in both A549 and MDA-MB-231 cell lines. Mechanistically, the drug combination inhibited both the Ras/Raf/mitogen-activated protein kinase and PI3K/Akt/mTOR pathways. Triolimus was advanced into tumor xenograft models for assessment of efficacy, toxicity, and mechanisms of action. In vivo, a three-infusion schedule of Triolimus inhibited A549 and MDA-MB-231 tumor growth far more potently than paclitaxel-containing micelles and effected tumor cures in MDA-MB-231 tumor-bearing animals. Tumor growth delays resulted from a doubling in tumor cell apoptosis and a 50% reduction in tumor cell proliferation compared with paclitaxel-containing micelles. Enhanced antitumor efficacy was achieved without clinically significant increases in acute toxicity. Thus, Triolimus displays potent synergistic activity in vitro and antitumor activity in vivo with comparable toxicity to paclitaxel. These observations provide strong support for further development of Triolimus and an important proof of concept for safe, effective nanoparticle-based delivery of three complementary anticancer agents.

Metformin potentiates the effects of paclitaxel in endometrial cancer cells through inhibition of cell proliferation and modulation of the mTOR pathway

OBJECTIVES

To examine the effects of combination therapy with metformin and paclitaxel in endometrial cancer cell lines.

METHODS

ECC-1 and Ishikawa endometrial cancer cell lines were used. Cell proliferation was assessed after exposure to paclitaxel and metformin. Cell cycle progression was assessed by flow cytometry. hTERT expression was determined by real-time RT-PCR. Western immunoblotting was performed to determine the effect of metformin/paclitaxel on the mTOR pathway.

RESULTS

Paclitaxel inhibited proliferation in a dose-dependent manner in both cell lines with IC(50) values of 1-5nM and 5-10nM for Ishikawa and ECC-1 cells, respectively. Simultaneous exposure of cells to various doses of paclitaxel in combination with metformin (0.5mM) resulted in a significant synergistic anti-proliferative effect in both cell lines (Combination Index<1). Metformin induced G1 arrest in both cell lines. Paclitaxel alone or in combination with metformin resulted in predominantly G2 arrest. Metformin decreased hTERT mRNA expression while paclitaxel alone had no effect on telomerase activity. Metformin stimulated AMPK phosphorylation and decreased phosphorylation of the S6 protein. In contrast, paclitaxel inhibited AMPK phosphorylation in the ECC-1 cell line and induced phosphorylation of S6 in both cell lines. Treatment with metformin and paclitaxel resulted in decreased phosphorylation of S6 in both cell lines but only had an additive effect on AMPK phosphorylation in the ECC-1 cell line.

CONCLUSIONS

Metformin potentiates the effects of paclitaxel in endometrial cancer cells through inhibition of cell proliferation and modulation of the mTOR pathway. This combination may be a promising targeted therapy for endometrial cancer.

Rapamycin synergizes with low-dose oxaliplatin in the HCT116 colon cancer cell line by inducing enhanced apoptosis

The present study aimed to examine the combined effects of oxaliplatin (L-OHP) and rapamycin (RAPA) in the HCT116 colon cancer cell line. The growth inhibitory effect was evaluated by MTT assay as a monotherapy or combination therapy. IC(50) values were determined using CalcuSyn 2.0 software. To determine the interaction of the drugs, the combination index (CI) was calculated using the Chou-Talalay method. Apoptosis was investigated using flow cytometry and Western blotting. Acridine orange staining was employed to observe morphological changes. The results showed the IC(50) values of L-OHP and RAPA to be 8.35±0.78 μM (r=0.99) and 223.44±38.10 nM (r=0.94), respectively. CI was ≤1 when L-OHP was used at doses ranging from 1 to 5 μM plus RAPA at a dose of 10 nM, suggesting synergistic or additive effects. CI was ≥1 when 100 nM RAPA was used in combination with low-dose L-OHP, showing additive to antagonistic effects. The combination of L-OHP (1 μM) and RAPA (10 nM) induced 19.76% Annexin V-positive cells, which was found to be higher than L-OHP (11.45%, p<0.01) or RAPA (6.89%, p<0.01) alone. The cleaved PARP protein expression levels were highest after 48 h of combination treatment. Acridine orange staining showed typical bright red Acidic vesicular organelles in the RAPA group, whereas the green condensed chromatin in the apoptotic bodies was found in both the L-OHP and combination groups. In conclusion, at a cytostatic concentration, RAPA was found to potentiate the anti-tumor effects of low-dose L-OHP in the HCT116 colon cancer cell by inducing enhanced apoptosis.

PRAS40 regulates protein synthesis and cell cycle in C2C12 myoblasts

PRAS40 is an mTOR binding protein that has complex effects on cell metabolism. Our study tests the hypothesis that PRAS40 knockdown (KD) in C2C12 myocytes will increase protein synthesis via upregulation of the mTOR-S6K1 pathway. PRAS40 KD was achieved using lentiviruses to deliver short hairpin (sh)-RNA targeting PRAS40 or a scrambled control. C2C12 cells were used as either myoblasts or differentiated to myotubes. Knockdown reduced PRAS40 mRNA and protein content by >80% of time-matched control values but did not alter the phosphorylation of mTOR substrates, 4E-BP1 or S6K1, in neither myoblasts nor myotubes. No change in protein synthesis in myotubes was detected, as measured by the incorporation of (35)S-methionine. In contrast, protein synthesis was reduced 25% in myoblasts. PRAS40 KD in myoblasts also decreased proliferation rate with an increased percent of cells retained in the G1 phase. PRAS40 KD myoblasts were larger in diameter and had a decreased rate of myotube formation as assessed by myosin heavy chain content. Immunoblotting revealed a 25-30% decrease in total p21 and S807/811 phosphorylated Rb protein considered critical for G1 to S phase progression. Reduction in protein synthesis was not due to increased apoptosis, since cleaved caspase-3 and DNA laddering did not differ between groups. In contrast, the protein content of LC3B-II was decreased by 30% in the PRAS40 KD myoblasts, suggesting a decreased rate of autophagy. Our results suggest that a reduction in PRAS40 specifically impairs myoblast protein synthesis, cell cycle, proliferation and differentiation to myotubes.

Promising novel therapies for the treatment of endometrial cancer

OBJECTIVES

To discuss the novel agents which are being developed for the treatment of advanced and recurrent endometrial carcinoma and to review other molecular targets that may be interesting in the treatment of this disease. While the majority of women with endometrial cancer enjoy a relatively good prognosis, the options for those women who suffer from a disease recurrence are limited and there is a need to identify novel agents.

METHODS

A review of clinical trials of novel therapeutic agents and their molecular targets is provided. In addition, a review of the current literature on other potential molecular targets for endometrial cancer was performed.

RESULTS

Several phase II trials of novel agents, both alone and in combination with traditional cytotoxic chemotherapy, have been completed or are nearing completion. It appears that the targeted agents may have the most efficacy in combination with cytotoxic chemotherapy or in a multi-targeted agent approach.

CONCLUSIONS

Chemotherapy offers the opportunity for a meaningful response rate in women with endometrial cancer, but the responses are often short lived and cure is uncommon in the setting of recurrent disease. The recent increase in molecular targets has led to the availability of many novel therapies. Determining how these agents are to be used, alone or in combination with "standard" therapies, needs to be defined and translational studies are needed to develop rational combinations of these novel agents before we can move into clinical trials.