New targets for therapy in breast cancer: mammalian target of rapamycin (mTOR) antagonists

Drug carrier wonders: Synthetic strategies of zeolitic imidazolates frameworks (ZIFs) and their applications in drug delivery and anti-cancer activity

With the rapid advancement of nanotechnology, stimuli-responsive nanomaterials have emerged as a feasible choice for the designing of controlled drug delivery systems. Zeolitic imidazolates frameworks are a subclass of Metal-organic frameworks (MOFs) that are recognized by their excellent porosity, structural tunability and chemical modifications make them promising materials for loading targeted molecules and therapeutics agents. The biomedical industry uses these porous materials extensively as nano-carriers in drug delivery systems. These MOFs not only possess excellent targeted imaging ability but also cause the death of tumor cells drawing considerable attention in the current framework of anticancer drug delivery systems. In this review, the outline of stability, porosity, mechanism of encapsulation and release of anticancer drug have been reported extensively. In the end, we also discuss a brief outline of current challenges and future perspectives of ZIFs in the biomedical world.

Nanoscale Zeolitic Imidazolate Framework (ZIF)–8 in Cancer Theranostics: Current Challenges and Prospects

Simple Summary

The biomedical application of metal–organic frameworks in cancer theranostics has become a research hotspot with rapid progress. As a typical representative, ZIF–8 attracts increasing interest from researchers due to its good performance and potential. In this review, we updated recent discoveries on the ZIF–8–based nanoplatforms for cancer, discussed the problems in current research and the obstacles for clinical translation of ZIF–8, and also proposed an outlook on its future development.

Abstract

Cancer severely threatens human health and has remained the leading cause of disease–related death for decades. With the rapid advancement of nanomedicine, nanoscale metal–organic frameworks are believed to be potentially applied in the treatment and biomedical imaging for various tumors. Zeolite imidazole framework (ZIF)–8 attracts increasing attention due to its high porosity, large specific surface area, and pH–responsiveness. The designs and modifications of ZIF–8 nanoparticles, as well as the strategy of drug loading, demand a multifaceted and comprehensive understanding of nanomaterial features and tumor characteristics. We searched for studies on ZIF–8–based nanoplatforms in tumor theranostics on Web of Science from 2015 to 2022, mainly focused on the research published in the past 3 years, summarized the progress of their applications in tumor imaging and treatment, and discussed the favorable aspects of ZIF–8 nanoparticles for tumor theranostics as well as the future opportunities and potential challenges. As a kind of metal–organic framework material full of potential, ZIF–8 can be expected to be combined with more therapeutic systems in the future and continue to contribute to all aspects of tumor therapy and diagnosis.

In silico molecular docking and dynamic simulation of eugenol compounds against breast cancer

Breast cancer is one of the most severe problems, and it is the primary cause of cancer-related death in females worldwide. The adverse effects and therapeutic resistance development are among the most potent clinical issues for potent medications for breast cancer treatment. The eugenol molecules have a significant affinity for breast cancer receptors. The aim of the study has been on the eugenol compounds, which has potent actions on Erα, PR, EGFR, CDK2, mTOR, ERBB2, c-Src, HSP90, and chemokines receptors inhibition. Initially, the drug-likeness property was examined to evaluate the anti-breast cancer activity by applying Lipinski's rule of five on 120 eugenol molecules. Further, structure-based virtual screening was performed via molecular docking, as protein-like interactions play a vital role in drug development. The 3D structure of the receptors has been acquired from the protein data bank and is docked with 87 3D PubChem and ZINC structures of eugenol compounds, and five FDA-approved anti-cancer drugs using AutoDock Vina. Then, the compounds were subjected to three replica molecular dynamic simulations run of 100 ns per system. The results were evaluated using root mean square deviation (RMSD), root mean square fluctuation (RMSF), and protein-ligand interactions to indicate protein-ligand complex stability. The results confirm that Eugenol cinnamaldehyde has the best docking score for breast cancer, followed by Aspirin eugenol ester and 4-Allyl-2-methoxyphenyl cinnamate. From the results obtained from in silico studies, we propose that the selected eugenols can be further investigated and evaluated for further lead optimization and drug development.

Synthesis, antitumor activity and in silico analyses of amino acid derivatives of artepillin C, drupanin and baccharin from green propolis

Breast cancer has the highest incidence and mortality in females, while prostate cancer has the second-highest incidence in males. Studies have shown that compounds from Brazilian green propolis have antitumor activities and can selectively inhibit the AKR1C3 enzyme, overexpressed in hormone-dependent prostate and breast tumors. Thus, in an attempt to develop new cytotoxic inhibitors against these cancers, three prenylated compounds, artepillin C, drupanin and baccharin, were isolated from green propolis to synthesize new derivatives via coupling reactions with different amino acids. All obtained derivatives were submitted to antiproliferative assays against four cancer cells (MCF-7, MDA MB-231, PC-3, and DU145) and two normal cell lines (MCF-10A and PNT-2) to evaluate their cytotoxicity. In general, the best activity was observed for compound6e, derived from drupanin, which exhibited half-maximal inhibitory concentration (IC₅₀) of 9.6 ± 3 μM and selectivity index (SI) of 5.5 against MCF-7 cells.In silicostudies demonstrated that these derivatives present coherent docking interactions and binding modes against AKR1C3, which might represent a possible mechanism of inhibition in MCF-7 cells.

Factors influencing the measurement of the secretion rate of extracellular vesicles

Extracellular vesicles (EVs) are cell-derived vesicles which encapsulate a variety of molecules. Numerous studies have demonstrated EVs as signaling mediators of intercellular communication and are heavily involved under physiological and pathological conditions. In translational medicine, EVs have been used for disease diagnosis and treatment monitoring. EVs as natural nanocarriers for drug delivery and therapeutic EVs are also under intense investigation. While still in its infancy, relevant EV studies have been growing. For EV-centered research to thrive, a few fundamental unanswered questions, such as EV biogenesis, EV secretion rate (SR), EV content sorting mechanisms, etc. require further investigation. In this study, we measured the SR of EVs derived from 6 cancerous cell lines. Several factors that may interfere with EV secretion, isolation, and storage were also investigated. Our results show that the SR of EVs derived from various cancer cells was significantly different, indicating a heterogeneous EV secretion behavior among cell types. Moreover, 5 different drugs that interfere with cellular metabolism significantly influenced EV release. In addition, we found that (1) more EVs can be harvested at 24 h compared to 48 h of serum-free cell culture with a similar degree of FBS contamination; (2) filtration of the cell culture supernatant with a 0.22 μm filter causes ∼70% loss of EVs; (3) the isolation efficiency of EVs with the prevalent ultracentrifugation is only ∼14%; (4) storage at 4 °C for 3 days causes ∼21% loss of EVs. Overall, our findings provide a guideline for proper EV collection and storage in laboratory settings.

Targeting of the Hedgehog/GLI and mTOR pathways in advanced pancreatic cancer, a phase 1 trial of Vismodegib and Sirolimus combination

BACKGROUND/OBJECTIVES

Preclinical data indicated a functional and molecular interaction between Hedgehog (HH)/GLI and PI3K-AKT-mTOR pathways promoting pancreatic ductal adenocarcinoma (PDAC). A phase I study was conducted of Vismodegib and Sirolimus combination to evaluate maximum tolerated dose (MTD) and preliminary anti-tumor efficacy.

METHODS

Cohort I included advanced solid tumors patients following a traditional 3 + 3 design. Vismodegib was orally administered at 150 mg daily with Sirolimus starting at 3 mg daily, increasing to 6 mg daily at dose level 2. Cohort II included only metastatic PDAC patients. Anti-tumor efficacy was evaluated every two cycles and target assessment at pre-treatment and after a single cycle.

RESULTS

Nine patient were enrolled in cohort I and 22 patients in cohort II. Twenty-eight patients were evaluated for dose-limiting toxicities (DLTs). One DLT was observed in each cohort, consisting of grade 2 mucositis and grade 3 thrombocytopenia. The MTD for Vismodegib and Sirolimus were 150 mg daily and 6 mg daily, respectively. The most common grade 3-4 toxicities were fatigue, thrombocytopenia, dehydration, and infections. A total of 6 patients had stable disease. No partial or complete responses were observed. Paired biopsy analysis before and after the first cycle in cohort II consistently demonstrated reduced GLI1 expression. Conversely, GLI and mTOR downstream targets were not significantly affected.

CONCLUSIONS

The combination of Vismodegib and Sirolimus was well tolerated. Clinical benefit was limited to stable disease in a subgroup of patients. Targeting efficacy demonstrated consistent partial decreases in HH/GLI signaling with limited impact on mTOR signaling. These findings conflict with pre-clinical models and warrant further investigations.

Rationally designed rapamycin-encapsulated ZIF-8 nanosystem for overcoming chemotherapy resistance

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are widely reported as a pH-sensitive drug delivery carrier with high loading capacity for tumor therapy. However, the mechanism of intracellular corrosion of ZIF-8 and the corresponding biological effects especially for autophagy response have been rarely reported. Herein, the as-synthesized ZIF-8 was demonstrated to induce mTOR independent and pro-death autophagy. Interestingly, the autophagic process participated in the corrosion of ZIF-8. Subsequently, zinc ion release and the generation of reactive oxygen species due to its corrosion in the acidic compartments were directly responsible for tumor cell killing. In addition, ZIF-8 could sensitize tumor cells to chemotherapy by switching cytoprotective to death promoting autophagy induced by doxorubicin. The mTOR signaling pathway activation was demonstrated to restrict tumor chemotherapy efficiency. Hence, a combined platform rapamycin encapsulated zeolitic imidazolate frameworks (Rapa@ZIF-8) was constructed and demonstrated a more significant chemo-sensitized effect relative to ZIF-8 nanoparticles or rapamycin treatment alone. Lastly, the combined administration of Rapa@ZIF-8 and doxorubicin exhibited an outstanding synergistic antitumor effect without any obvious toxicity to the major organs of mice. Collectively, the optimized nanoplatform, Rapa@ZIF-8, provides a proof of concept for intentionally interfering mTOR pathway and utilizing the switch of survival-to death-promoting autophagy for adjunct chemotherapy.

eIF4E is a critical regulator of human papillomavirus (HPV)-immortalized cervical epithelial (H8) cell growth induced by nicotine

Tobacco smoke is known as a cofactor in the development of cervical precancer and cancer caused by human papillomavirus (HPV). The main component in cigarette smoke, nicotine, can be concentrated more strongly in cervical mucus than in blood and it has been implicated as a cocarcinogen that promotes a serial of cancers development through multiple prosurvival pathways. Although the mechanisms of nicotine-induced cell proliferation have been well studied in some epithelial cells, the molecular mechanism of its action in cervical epithelial cells is still unclear. The aims of this study were to investigate the detailed mechanism by which nicotine could induce cervical cancer growth. We found that nicotine simultaneously activates AKT/mTOR pathway in HPV-immortalized cervical epithelial (H8) cell line, followed by elevation of 4EBP1/eIF4E axis expression and its translational activity with dose-dependent and time-dependent manners. Besides, nicotine decreases eIF4E-4EBP1 binding activity in H8 cell line, which is associated with increased expression of phospho-4EBP1 at threonine 70. We therefore chose to evaluate whether this effect on eIF4E was involved in nicotine-induced proliferation. Remarkably, eIF4E knockdown by small interfering RNA diminishes its translation activity to the downstream targets including c-Myc, VEGF, CyclinD1 and Bcl-2. What is more, eIF4E knockdown inhibits cellular growth and colony formation after nicotine treatment. Note as well that eIF4E-specific siRNA could also suppress cell proliferation by decelerating the G0/G1-S transition of H8 cell treated with nicotine. Taken together, it can be concluded that nicotine promotes H8 cell proliferation by activating AKT/mTOR pathway, as well as 4EBP1/eIF4E axis and its translational activity. Furthermore, phosphorylation of 4EBP1 induced by nicotine has been shown to cause dissociation of 4EBP1/eIF4E and eIF4E may serve as a promising determinant of nicotine activity in vitro.

eIF4E promotes tumorigenesis and modulates chemosensitivity to cisplatin in esophageal squamous cell carcinoma

Patients with esophageal squamous cell cancer are often diagnosed with advanced diseases that respond poorly to chemotherapy. Overexpression of eIF4E leads to enhance the translation of key malignancy-related proteins and enabling tumor growth and chemoresistance in a variety of human malignancies, but whether it has a role in ESCC remains obscure. We hypothesized that eIF4E promoted ESCC tumorigenesis and facilitated the development of acquired resistance to the cisplatin-based chemotherapy. In this study, we showed that eIF4E expression was increased significantly in clinical ESCC tissues and and ESCC cell lines and its expression level was correlated with lymph node metastasis, TNM stage, as well as overall and disease-free survival of ESCC. We also showed here that knockdown of eIF4E in EC9706 would dramatically reduced cell proliferation, colony formation, migration and invasion, apoptosis in vitro as well as in vivo, and vice versa. Moreover, "weak mRNAs" were demonstrated to be regulated by eIF4E in ESCC, which might interpret the above function. Overexpression of eIF4E decreased the efficacy of cisplatin-induced cell growth inhibition in ESCC cell line and xenograft model (P < 0.05). eIF4E knockdown by shRNA increased cisplatin-induced cytotoxicity in ESCC cell lines, and enhanced chemosensitivity to cisplatin in xenograft tumor models. Furthermore, we found that the PI3K/AKT pathway and Bcl-2/Bax ratio might be responsible for the eIF4E-induced cisplatin resistance in ESCC. Our data collectively show association of eIF4E expression with chemotherapeutic response in ESCC, and suggest that therapeutically targeting eIF4E may be a viable means of improving chemotherapy response in ESCC.

Bioinformatic identification of chemoresistance-associated microRNAs in breast cancer based on microarray data

Breast cancer is the most commonly diagnosed cancer among females, and chemoresistance constitutes a major clinical obstacle to the treatment of this disease. MicroRNAs (miRNAs) are related to human cancer development, progression and drug resistance. To identify breast cancer chemoresistance-associated miRNAs, miRNA microarray dataset GSE71142, including five chemoresistant breast cancer tissues and five chemosensitive tissues, was downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed miRNAs (DE-miRNAs) were obtained by t-test and the potential target genes were predicted by miRWalk2.0. Functional and pathway enrichment analysis by WebGestalt was performed for the potential target genes of DE-miRNAs. Protein-protein interaction (PPI) network was established by STRING database and visualized by Cytoscape software. Enriched transcription factors by the target genes were obtained from FunRich. Breast cancer-associated miRNA-gene pairs were identified from miRWalk2.0. A total of 22 DE-miRNAs were screened out, including 10 upregulated miRNAs (e.g., miR-196a-5p) and 12 downregulated miRNAs (e.g., miR-4472) in the chemoresistant breast cancer tissues, compared with chemosensitive tissues. In total 1,278 target genes were screened out, and they were involved in breast cancer-related pathways such as pathways in cancer, signaling pathways regulating pluripotency of stem cells, endocrine resistance, breast cancer, mTOR signaling and Hippo signaling pathway. NOTCH1 and MAPK14 were identified as hub genes in the PPI network. EGR1 and SP1 were the most enriched transcription factors by the target genes. Several breast cancer-associated miRNA-gene pairs including miR-214-TP53 and miR-16-PPM1D were identified. The current bioinformatics study of miRNAs based on microarray may offer a new understanding into the mechanisms of breast cancer chemoresistance, and may identify novel miRNA therapeutic targets.

Molecularly Targeted Therapies for Breast Cancer

Background:

The management of patients with localized and advanced breast cancer continues to evolve. Chemotherapy, endocrine therapy, and trastuzumab are effective therapies but leave considerable room for improvement. As the cellular aberrations inherent to cancer cells in general and breast cancer cells specifically are better understood, therapies to target specific cellular pathways continue to be developed with the goal of expanding available effective therapy through better patient selection.

Methods:

We conducted a computerized search of the medical literature as well as a manual search of selected meeting abstracts.

Results:

Several targeted therapies are in phase III clinical trials testing their promise in the treatment of breast cancer. Many other agents are completing phase I and II testing. An overview of the most promising agents in clinical development is discussed herein.

Conclusions:

Targeted therapy for breast cancer is a reality at this time, and several new agents hold promise for expanding and refining the pool of patients likely to further benefit from this approach in the near future.

Phase I Trial of Everolimus and Capecitabine in Metastatic HER2- Breast Cancer

BACKGROUND

The mammalian target of rapamycin (mTOR) pathway is a driver of breast tumorigenesis. The mTOR inhibitor everolimus reverses antihormonal therapy resistance and is an approved therapy for metastatic breast cancer. A synergistic effect with fluoropyrimidine has been suggested. The present study evaluated the safety and tolerability of an all-oral combination of everolimus and capecitabine for metastatic breast cancer (MBC).

PATIENTS AND METHODS

MBC patients naive to capecitabine and mTOR inhibitors who had received ≤ 3 previous chemotherapy regimens in the metastatic setting were eligible for the present study. The patients were scheduled to receive capecitabine 825 mg/m² twice daily for 14 days in a 21-day cycle, combined with everolimus in 5 separate dose cohorts: 2.5 mg every other day, 2.5 mg daily, 5 mg daily, 7.5 mg daily, and 10 mg daily. A 3+3 design was used. The maximum tolerated dose was based on the dose-limiting toxicity of everolimus plus capecitabine.

RESULTS

A total of 18 patients were enrolled in the present trial. The median age was 58 years. Most had received previous anthracycline (83%) and taxane (94%) therapy. The maximum tolerated dose was everolimus 7.5 mg daily and capecitabine 825 mg/m². The incidence of grade 3 events was low and mainly hematologic in nature. One incident each of grade 4 neutropenia, thrombocytopenia, hyperglycemia, and mucositis occurred. No grade 5 events occurred. The clinical benefit rate was 50%. The median progression-free survival was 196 days, and the median overall survival was 569 days.

CONCLUSION

The all-oral regimen of everolimus with capecitabine is active and well tolerated, with encouraging results for progression-free survival, overall survival, and clinical benefit rate in patients with MBC.

Novel effect and the mechanistic insights of fruiting body extract of medicinal fungus Antrodia cinnamomea against T47D breast cancer

INTRODUCTION

Tamoxifen, an anti-oestrogenic drug for estrogen receptor positive (ER+) breast cancer, was observed to stimulate tumor growth or drug resistance in patients. Antrodia cinnamomea (AC), a precious medicinal fungus has been traditionally used as a folk remedy for cancers in Asian countries. The objective of this study was to investigate the bioefficacy and the underlying molecular mechanisms of the AC fruiting bodies extracts (AC-3E) against human ER+ T47D breast cancer cells, and compare the effect with that of tamoxifen.

METHODS

Cell proliferation, migration, TUNEL assay, western blotting, time-lapse confocal microscopy analyses, chorioallantoic membrane assay, and a xenograft BALB/c nude mouse system were used in this study. Chemical fingerprinting of AC-3E was established using LC-MS.

RESULTS

AC-3E attenuated T47D breast cancer cell activity by deregulating the PI3K/Akt/mTOR signaling pathway and key cell-cycle mediators, and inducing apoptosis. AC-3E also effectively inhibited tube-like structures of endothelial cells, blood vessel branching and microvessel formation ex vivo and in vivo. Significant preventive and therapeutic effects against T47D mammary tumor growth of AC-3E was observed comparable or superior to tamoxifen treatment in xenograft BALB/c nude mice. Dehydroeburicoic acid (2) was characterized as the main chemical constituent in AC-3E against breast cancer.

CONCLUSION

This study suggests that AC-3E extracts can be employed as a double-barreled approach to treat human ER+ breast cancer by attacking both cancer cells and tumor-associated blood vessel cells.

Twist promotes reprogramming of glucose metabolism in breast cancer cells through PI3K/AKT and p53 signaling pathways

Twist, a key regulator of epithelial-mesenchymal transition (EMT), plays an important role in the development of a tumorigenic phenotype. Energy metabolism reprogramming (EMR), a newly discovered hallmark of cancer cells, potentiates cancer cell proliferation, survival, and invasion. Currently little is known about the effects of Twist on tumor EMR. In this study, we found that glucose consumption and lactate production were increased and mitochondrial mass was decreased in Twist-overexpressing MCF10A mammary epithelial cells compared with vector-expressing MCF10A cells. Moreover, these Twist-induced phenotypic changes were augmented by hypoxia. The expression of some glucose metabolism-related genes such as PKM2, LDHA, and G6PD was also found to be upregulated. Mechanistically, activated β1-integrin/FAK/PI3K/AKT/mTOR and suppressed P53 signaling were responsible for the observed EMR. Knockdown of Twist reversed the effects of Twist on EMR in Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Furthermore, blockage of the β1-integrin/FAK/PI3K/AKT/mTOR pathway by siRNA or specific chemical inhibitors, or rescue of p53 activation can partially reverse the switch of glucose metabolism and inhibit the migration of Twist-overexpressing MCF10A cells and Twist-positive breast cancer cells. Thus, our data suggest that Twist promotes reprogramming of glucose metabolism in MCF10A-Twist cells and Twist-positive breast cancer cells via activation of the β1-integrin/FAK/PI3K/AKT/mTOR pathway and inhibition of the p53 pathway. Our study provides new insight into EMR.

DNA damage-induced S and G2/M cell cycle arrest requires mTORC2-dependent regulation of Chk1

mTOR signalling is commonly dysregulated in cancer. Concordantly, mTOR inhibitors have demonstrated efficacy in a subset of tumors and are in clinical trials as combination therapies. Although mTOR is associated with promoting cell survival after DNA damage, the exact mechanisms are not well understood. Moreover, since mTOR exists as two complexes, mTORC1 and mTORC2, the role of mTORC2 in cancer and in the DNA damage response is less well explored. Here, we report that mTOR protein levels and kinase activity are transiently increased by DNA damage in an ATM and ATR-dependent manner. We show that inactivation of mTOR with siRNA or pharmacological inhibition of mTORC1/2 kinase prevents etoposide-induced S and G2/M cell cycle arrest. Further results show that Chk1, a key regulator of the cell cycle arrest, is important for this since ablation of mTOR prevents DNA damage-induced Chk1 phosphorylation and decreases Chk1 protein production. Furthermore, mTORC2 was essential and mTORC1 dispensable, for this role. Importantly, we show that mTORC1/2 inhibition sensitizes breast cancer cells to chemotherapy. Taken together, these results suggest that breast cancer cells may rely on mTORC2-Chk1 pathway for survival and provide evidence that mTOR kinase inhibitors may overcome resistance to DNA-damage based therapies in breast cancer.

Regulation of the cell cycle and PI3K/Akt/mTOR signaling pathway by tanshinone I in human breast cancer cell lines

Breast cancer is the second leading cause of cancer‑related mortality in females worldwide. Therefore, identifying alternative strategies to combat the disease mortality is important. The aim of the present study was to investigate the effect of tanshinone I (Tan I) on the tumorigenicity of estrogen‑responsive MCF‑7 and estrogen‑independent MDA‑MB‑453 human breast cancer cells. The cytotoxicity of Tan I was evaluated using a Cell Counting Kit‑8 assay, the apoptosis and cell cycle distribution were detected using flow cytometry and the cell morphology was observed using a fluorescence microscope. In addition, the cell cycle regulatory proteins and apoptosis‑associated proteins involved in the phosphatidylinositide 3‑kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway were detected using western blot analysis using specific protein antibodies. The MCF‑7 and MDA‑MB‑453 cells were equally sensitive to Tan I regardless of their responsiveness to estrogen. Tan I exerted similar antiproliferative activities and induction of apoptosis, resulting in S phase arrest accompanied by decreases in cyclin B and increases in cyclin E and cyclin A proteins, which may have been associated with the upregulation of cyclin‑dependent kinase inhibitors p21Cip1 and p27Kip1. In addition, Tan I was found to downregulate anti‑apoptotic and upregulate associated apoptotic components of the PI3K/Akt/mTOR signaling pathway. Notably, treatment with the PI3K inhibitor, LY294002, decreased the levels of phosphorylated (p)‑PI3K, p‑Akt and p‑mTOR. These results clearly indicated that the mechanism of action of Tan I involved, at least partially, an effect on the PI3K/Akt/mTOR signaling pathway, providing new information for anticancer drug design and development.

Rapamycin induces apoptosis when autophagy is inhibited in T-47D mammary cells and both processes are regulated by Phlda1

Autophagy is an evolutionarily conserved lysosomal degradation pathway and plays a critical role in the homeostatic process of recycling proteins and organelles. Functional relationships have been described between apoptosis and autophagy. Perturbations in the apoptotic machinery have been reported to induce autophagic cell deaths. Inhibition of autophagy in cancer cells has resulted in cell deaths that manifested hallmarks of apoptosis. However, the molecular relationships and the circumstances of which molecular pathways dictate the choice between apoptosis and autophagy are currently unknown. This study aims to identify specific gene expression of rapamycin-induced autophagy and the effects of rapamycin when the autophagy process is inhibited. In this study, we have demonstrated that rapamycin is capable of inducing autophagy in T-47D breast carcinoma cells. However, when the autophagy process was inhibited by 3-MA, the effects of rapamycin became apoptotic. The Phlda1 gene was found to be up-regulated in both autophagy and apoptosis and silencing this gene was found to reduce both activities, strongly suggests that Phlda1 mediates and positively regulates both autophagy and apoptosis pathways.

Colocalized delivery of rapamycin and paclitaxel to tumors enhances synergistic targeting of the PI3K/Akt/mTOR pathway

Ongoing clinical trials target the aberrant PI3K/Akt/mammalian target of rapamycin (mTOR) pathway in breast cancer through administration of rapamycin, an allosteric mTOR inhibitor, in combination with paclitaxel. However, synergy may not be fully exploited clinically because of distinct pharmacokinetic parameters of drugs. This study explores the synergistic potential of site-specific, colocalized delivery of rapamycin and paclitaxel through nanoparticle incorporation. Nanoparticle drug loading was accurately controlled, and synergistic drug ratios established in vitro. Precise drug ratios were maintained in tumors 48 hours after nanoparticle administration to mice, at levels twofold greater than liver and spleen, yielding superior antitumor activity compared to controls. Simultaneous and preferential in vivo delivery of rapamycin and paclitaxel to tumors yielded mechanistic insights into synergy involving suppression of feedback loop Akt phosphorylation and its downstream targets. Findings demonstrate that a same time, same place, and specific amount approach to combination chemotherapy by means of nanoparticle delivery has the potential to successfully translate in vitro synergistic findings in vivo. Predictive in vitro models can be used to determine optimum drug ratios for antitumor efficacy, while nanoparticle delivery of combination chemotherapies in preclinical animal models may lead to enhanced understanding of mechanisms of synergy, ultimately opening several avenues for personalized therapy.

Morphoproteomics: exposing protein circuitries in tumors to identify potential therapeutic targets in cancer patients

Morphoproteomics combines the disciplines of histopathology, molecular biology and protein chemistry to paint a portrait of the protein circuitry in diseased cells for the purpose of uncovering molecular targets amenable to specific intervention, thereby customizing therapy for individual patients. This review considers the clinical application of morphoproteomics in malignant cells in the context of currently available pharmaceutical agents and discusses opportunities for combinatorial approaches that involve one or more small molecule inhibitors and single-agent chemotherapy with relatively low toxicity profiles. Future directions that involve focusing on points of convergence in signal transduction pathways and which integrate morphoproteomic with genomic and pharmacoproteomic and protein-function microarray data are offered.

Combination of cetuximab and rapamycin enhances the therapeutic efficacy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide. It is well known that the activation of PI3K/AKT/mTOR and the Ras/MAPK signaling pathway plays a critical role in cellular metabolism, growth and proliferation, and its inhibitors have been used as therapeutic drugs for hepatocellular carcinoma. Cetuximab, a chimerical monoclonal EGFR IgG1 antibody, can block the binding of EGF or other ligands to EGFR and thus inhibit ligands-induced receptor phosphorylation. In the present study, we found that rapamycin could enhance the antiproliferation effect of cetuximab in both HepG2 cells and Huh-7 cells and arrest the cell cycle. Cetuximab in combination with rapamycin had synergistic effects on inhibiting the phosphrylation of proteins in PI3K/AKT/mTOR and Ras/MAPK signaling pathway. Combination of cetuximab with rapamycin treatment significantly suppressed the HCC development in HepG2 cells-xenografted mice and improved the survival. Cetuximab and rapamycin inhibited the growth of HCC both in vitro and in vivo. These results suggest that the combination therapy using the inhibitors for both EGFR and PI3K/AKT/mTOR signaling pathways may be a novel therapeutic approach for HCC.

Pertuzumab: a new targeted therapy for HER2-positive metastatic breast cancer

Trastuzumab, a humanized monoclonal antibody, has become an important targeted therapy for patients with all stages of human epidermal growth factor receptor-2 (HER2)-positive breast cancer. However, primary and acquired resistance to trastuzumab remains a significant problem. Pertuzumab, a humanized monoclonal antibody that binds to a domain of the HER2 receptor separate from trastuzumab, may have the potential to overcome trastuzumab resistance. Clinical trials have shown that pertuzumab can be effectively combined with other biologic therapy or chemotherapy in patients with metastatic HER2-positive breast cancer. Pertuzumab is relatively well tolerated with minimal increases in hematologic and cardiac toxicity observed when added to trastuzumab and/or docetaxel. In addition to becoming the standard of care in combination with docetaxel and trastuzumab in patients with newly diagnosed HER2-positive metastatic breast cancer, clinical trials continue to evaluate pertuzumab in combination with other targeted therapy, chemotherapy, and in patients with early stage breast cancer. These trials will help to further determine the role of pertuzumab in the treatment of HER2-positive breast cancer.

Hyperactivation of EGFR and downstream effector phospholipase D1 by oncogenic FAM83B

Despite the progress made in targeted anticancer therapies in recent years, challenges remain. The identification of new potential targets will ensure that the arsenal of cancer therapies continues to expand. FAM83B was recently discovered in a forward genetic screen for novel oncogenes that drive human mammary epithelial cell (HMEC) transformation. We report here that elevated FAM83B expression increases Phospholipase D (PLD) activity, and that suppression of PLD1 activity prevents FAM83B-mediated transformation. The increased PLD activity is engaged by hyperactivation of epidermal growth factor receptor (EGFR), which is regulated by an interaction involving FAM83B and EGFR. Preventing the FAM83B/EGFR interaction by site-directed mutation of lysine 230 of FAM83B suppressed PLD activity and MAPK signaling. Furthermore, ablation of FAM83B expression from breast cancer cells inhibited EGFR phosphorylation and suppressed cell proliferation. We propose that understanding the mechanism of FAM83B-mediated transformation will provide a foundation for future therapies aimed at targeting its function as an intermediary in EGFR, MAPK, and mTOR activation.

Activation of mammalian target of rapamycin (mTOR) in triple negative feline mammary carcinomas

Background

Triple negative breast cancer (TNBC) in humans is defined by the absence of oestrogen receptor (ER), progesterone receptor (PR) and HER2 overexpression. Mammalian target of rapamycin (mTOR) is overexpressed in TNBC and it represents a potential target for the treatment of this aggressive tumour. Feline mammary carcinoma (FMC) is considered to be a model for hormone-independent human breast cancer. This study investigated mTOR and p-mTOR expression in FMC in relation to triple negative (TN) phenotype.

Results

The expression of mTOR, p-mTOR, ERα, PR and HER2 was evaluated in 58 FMCs by immunohistochemistry and in six FMC cell lines by Western blot analysis. 53.5% of FMC analyzed were ER, PR, HER2 negative (TN-FMC) while 56.9% and 55.2% of cases expressed mTOR and p-mTOR respectively. In this study we found that m-TOR and p-mTOR were more frequently detected in TN-FMC and in HER2 negative samples.

Conclusions

In this study, we demonstrate that there is also a FMC subset defined as TN FMC, which is characterised by a statistically significant association with m-TOR and p-mTOR expression as demonstrated in human breast cancer.

Combining mTOR Inhibitors with Chemotherapy and Other Targeted Therapies in Advanced Breast Cancer: Rationale, Clinical Experience, and Future Directions

Improvements in survival of patients with breast cancer have been attributed to the development of agents that target key components of dysregulated pathways involved in oncogenesis and progression of breast cancer. Aberrant mammalian target of rapamycin (mTOR) activation has been implicated in oncogenesis, angiogenesis, and the development of estrogen independence and resistance to chemotherapy in breast tumors. Several mTOR inhibitors (sirolimus, everolimus, temsirolimus, and ridaforolimus) have demonstrated antitumor activity in breast cancer cells. Combining mTOR inhibitors with endocrine therapies has demonstrated clinical antitumor activity in patients with metastatic breast cancer. In addition, mTOR inhibitor combinations with various targeted biologic agents or cytotoxic chemotherapeutic agents are being examined in more than 40 clinical trials with some early promising results. Combination therapies targeting multiple components of these central signaling pathways may be an optimal treatment strategy for patients with advanced breast cancer.

New and emerging treatments for estrogen receptor-positive breast cancer: focus on everolimus

Management of patients with metastatic hormone receptor-positive breast cancer poses a challenge due to the inevitable development of endocrine resistance. Hormone resistance is associated with a complex interaction of the estrogen receptor with growth factors, transmembrane receptors, and intracellular growth cascades. The PI3K/Akt/mTOR pathway plays a major role in hormone resistance and proliferation of breast cancer. Preclinical and clinical data indicate that inhibitors of human epidermal growth factor receptor-2, epidermal growth factor receptor, insulin-like growth factor-1 receptor, and the mammalian target of rapamycin pathway may act synergistically with hormone therapy to circumvent endocrine resistance. Everolimus is currently approved for combination with exemestane in postmenopausal women with advanced hormone receptor-positive breast cancer. However, we still need to unfold the full potential of targeted agents in the hormone-refractory setting and to identify the subsets of patients who will benefit from combination hormonal therapy using targeted agents.

Serum and glucocorticoid-regulated kinase 1 (SGK1) activation in breast cancer: requirement for mTORC1 activity associates with ER-alpha expression

Mammalian target of rapamycin (mTOR) is an attractive target for cancer treatment. While rapamycin and its derivatives (e.g., everolimus) have been shown to inhibit mTOR signaling and cell proliferation in preclinical models of breast cancer, mTOR inhibition has demonstrated variable clinical efficacy with a trend toward better responses in estrogen receptor alpha positive (ERα+) compared to ERα negative (ERα-) tumors. Recently, serum- and glucocorticoid-regulated kinase 1 (SGK1) was identified as a substrate of mTOR kinase activity. Previous studies have alternatively suggested that either mTORC1 or mTORC2 is exclusively required for SGK1's Ser422 phosphorylation and activation in breast cancer cells. We investigated the effect of rapamycin on the growth of several ERα+ and ERα- breast cancer cell lines and examined differences in the phosphorylation of mTOR substrates (SGK1, p70S6K, and Akt) that might account for the differing sensitivity of these cell lines to rapamycin. We also examined which mTOR complex contributes to SGK1-Ser422 phosphorylation in ERα+ versus ERα- breast cell lines. We then assessed whether inhibiting SGK1 activity added to rapamycin-mediated cell growth inhibition by either using the SGK1 inhibitor GSK650394A or expressing an SGK1 shRNA. We observed sensitivity to rapamycin-mediated growth inhibition and inactivation of insulin-mediated SGK1-Ser422 phosphorylation in ERα+ MCF-7 and T47D cells, but not in ERα- MDA-MB-231 or MCF10A-Myc cells. In addition, either depleting SGK1 with shRNA or inhibiting SGK1 with GSK650394A preferentially sensitized MDA-MB-231 cells to rapamycin. Finally, we found that rapamycin-sensitive SGK1-Ser422 phosphorylation required ERα expression in MCF-7 derived cell lines. Therefore, targeting SGK1 activity may improve the efficacy of rapamycin and its analogs in the treatment of ERα- breast cancer.

Optimizing targeted cancer therapy: towards clinical application of systems biology approaches

In cancer, genetic and epigenetic alterations ultimately culminate in discordant activation of signal transduction pathways driving the malignant process. Pharmacological or biological inhibition of such pathways holds significant promise with respect to devising rational therapy for cancer. Thus, technical concepts pursuing robust characterization of kinase activity in tissue samples from cancer patients have been subject of investigation. In the present review we provide a comprehensive overview of these techniques and discuss their advantages and disadvantages for systems biology approaches to identify kinase targets in oncological disease. Recent advances in the development and application of array-based peptide-substrate kinase activity screens show great promise in overcoming the discrepancy between the evaluation of aberrant cell signaling in specific malignancies or even individual patients and the currently available ensemble of highly specific targeted treatment strategies. These developments have the potential to result in a more effective selection of kinase inhibitors and thus optimize mechanism-based patient-specific therapeutic strategies. Given the results from current research on the tumor kinome, generating network views on aberrant tumor cell signaling is critical to meet this challenge.

Caveolin-1 and accelerated host aging in the breast tumor microenvironment: chemoprevention with rapamycin, an mTOR inhibitor and anti-aging drug

Increasing chronological age is the most significant risk factor for human cancer development. To examine the effects of host aging on mammary tumor growth, we used caveolin (Cav)-1 knockout mice as a bona fide model of accelerated host aging. Mammary tumor cells were orthotopically implanted into these distinct microenvironments (Cav-1(+/+) versus Cav-1(-/-) age-matched young female mice). Mammary tumors grown in a Cav-1-deficient tumor microenvironment have an increased stromal content, with vimentin-positive myofibroblasts (a marker associated with oxidative stress) that are also positive for S6-kinase activation (a marker associated with aging). Mammary tumors grown in a Cav-1-deficient tumor microenvironment were more than fivefold larger than tumors grown in a wild-type microenvironment. Thus, a Cav-1-deficient tumor microenvironment provides a fertile soil for breast cancer tumor growth. Interestingly, the mammary tumor-promoting effects of a Cav-1-deficient microenvironment were estrogen and progesterone independent. In this context, chemoprevention was achieved by using the mammalian target of rapamycin (mTOR) inhibitor and anti-aging drug, rapamycin. Systemic rapamycin treatment of mammary tumors grown in a Cav-1-deficient microenvironment significantly inhibited their tumor growth, decreased their stromal content, and reduced the levels of both vimentin and phospho-S6 in Cav-1-deficient cancer-associated fibroblasts. Since stromal loss of Cav-1 is a marker of a lethal tumor microenvironment in breast tumors, these high-risk patients might benefit from treatment with mTOR inhibitors, such as rapamycin or other rapamycin-related compounds (rapalogues).

PTEN activation sensitizes breast cancer to PI3-kinase inhibitor through the β-catenin signaling pathway

Combination therapy is considered a promising therapeutic modality in enhancing treatment efficacy. The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is almost universally dysregulated in breast cancer, with specific occurrence of PTEN mutations; thus, it has become an attractive target for cancer treatment. However, the use of single targeted therapeutics against the PI3K/AKT pathway has demonstrated only modest clinical benefits. In this study, recombinant adenovirus-mediated gene transfer of PTEN (AD-PTEN) combined with treatment with LY294002 was utilized to evaluate the effects of suppression of breast cancer cell proliferation. Herein, we show that AD-PTEN significantly enhanced the sensitization of breast cancer cells to LY294002. The 50% inhibitory concentration (IC50) values of LY294002 were significantly decreased to a greater extent in cells transfected with combination therapy. In addition, treatment of AD-PTEN-transfected cells with LY294002 resulted in significantly reduced cell viability and invasion ability compared to single LY294002 treatment. Using western blotting, we found that combination treatment resulted in lower levels of phosphorylated AKTSer473 and GSK-3βSer9 than single treatment with LY294002. Furthermore, we showed a significant decrease in nuclear β-catenin, Fra-1, Tcf-4 and c-Myc by combination treatment. Our results indicate that AD-PTEN sensitization of breast cancer to LY294002 is achieved by increased GSK-3β activity, thus resulting in inhibition of the β-catenin signaling pathway.

HER2+ Breast Cancer Therapy: By CPP-ZFN Mediated Targeting of mTOR?

A significant fraction of HER2+ patients develop resistance to available therapies such as trastuzumab. The acquired resistance is primarily due to hyper activation of HER2 downstream PI3K/Akt/mTOR signalling pathway. Hence, identification of inhibitors of components of this pathway, particularly mTOR, is an area of intense investigation. Interestingly, mTOR specific inhibitors (rapamycin/rapalogs) have been tested and shown to potentiate the effect of HER2 inhibitors. However, the use of mTOR inhibitors will also be associated with the limitations inherently linked with extensive use of anticancer drugs e.g., toxicity and acquired drug resistance. Hereby, we hypothesize development of an alternative novel molecular therapeutic intervention based on cell penetrating peptide (CPP), a highly efficient carrier, conjugated to zinc finger nuclease (ZFN), a precise molecular scissor. The use of HER2 specific CPP conjugated to mTOR specific ZFN, will make the mTOR locus non-functional and inhibit the PI3K/Akt/mTOR pathway, essential for growth and proliferation of cancerous cells. With the availability of HER2+ cancerous cell specific CPP and proved applications of ZFN in targeted genome engineering of over 11 species, the prospects of success of CPP-ZFN anti-cancer therapy are very high.

Managing stomatitis in patients treated with Mammalian target of rapamycin inhibitors

Mammalian target of rapamycin (mTOR) inhibitors are a class of targeted cancer therapeutic agents with clinical benefit for multiple tumor types. Oral ulcerations are a common side effect of mTOR inhibitors; however, the clinical findings resemble aphthous stomatitis rather than the mucositis seen with chemotherapy. Consequently, the appearance of aphthous-like oral ulcerations has been referred to as mTOR inhibitor-associated stomatitis (mIAS). The severity of mIAS can be minimized by following common preventive steps and initiating treatment at the first sign of mouth discomfort, thereby reducing the likelihood of treatment discontinuation. mIAS can be managed through prophylactic measures, such as patient education in oral hygiene and avoidance of triggers. Patients who develop mIAS may be treated topically using rinses or other local therapies, including corticosteroids. In severe cases, dose modifications may be required. Oncology nurses have an important role in the management of patients with cancer and are well positioned to offer strategies for minimizing the occurrence and impact of mIAS.

Inhibitors of mTOR overcome drug resistance from topoisomerase II inhibitors in solid tumors

The present study was performed to investigate the possible role of mTOR inhibitors in restoring chemosensitivity to adriamycin/cisplatin and elucidate the underlying mechanism. Combining adriamycin/cisplatin with torisel synergistically inhibited the cell proliferation in human oropharyngeal carcinoma cell line KB and its multidrug-resistant subclone KB/7D. Combining adriamycin and torisel inhibited the phosphorylation of 4EBP-1 and p70S6K, the proteins involved in mTOR pathway, increased expression of γH2AX indicative of DNA damage, triggered cell cycle arrest at G2/M and apoptosis. We conclude that chromatin decondensation by DNA damage provided an easy access for torisel to block the translation of proteins essential for DNA repair thereby restoring the chemosensitivity.

Does the PI3K pathway play a role in basal breast cancer?

Many cell kinases exert their proliferative and pro-survival effects through activation of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway. Basal-like breast cancer is a subtype that can be identified by molecular analysis and often includes tumors lacking expression of estrogen receptor/progesterone receptor or human epidermal growth factor receptor, also known as triple-negative breast cancers. Triple-negative cancers comprise < 20% of all breast cancers and have no obvious mechanism driving proliferation, yet these tumors demonstrate higher levels of Akt activation compared with non-triple-negative breast cancers. This suggests a possible role for targeting the PI3K pathway for the treatment of this subset of aggressive cancers. Most clinical trials which have attempted targeting the PI3K/Akt pathway in triple-negative breast cancer have involved the use of EGFR inhibitors with limited success. Novel agents targeting PI3K are under development in early-phase clinical trials and may demonstrate benefit in combination with chemotherapy or other targeted agents such as mitogen-activated protein kinase inhibitors for the treatment of triple-negative or basal-like breast cancer.

mTOR inhibition in breast cancer: unraveling the complex mechanisms of mTOR signal transduction and its clinical implications in therapy

INTRODUCTION

The mammalian target of rapamycin (mTOR)/PI3K/Akt pathway is altered in breast cancer cells, as demonstrated by mutations in both the upstream and downstream regulators of mTOR, including phosphatase and tensin homolog deleted in chromosome 10 (PTEN) loss or Akt/PI3K activation, and potentially in the mTOR protein itself. This contributes to increased cell proliferation, as well as growth-factor independence and endocrine resistance. Thus, mTOR inhibition holds considerable promise as a rational therapeutic strategy in breast cancer.

AREAS COVERED

This review describes how dysregulation of the mTOR pathway in breast cancer may contribute to breast cancer pathogenesis, as well as discussing preclinical and clinical data that support mTOR inhibitor therapy.

EXPERT OPINION

Direct blockade of the mTOR pathway is a new and intriguing area in breast cancer therapy, with the potential to modulate growth-factor and estrogen-dependent and -independent pathways, that contribute to the pathogenesis and progression of breast tumors. mTOR inhibitors demonstrate significant biologic activity with manageable toxicities, in combination with hormonal therapy and chemotherapy, in both the neoadjuvant and metastatic breast cancer settings.

Intrinsic Resistance to Chemotherapy in Breast Cancer

Systemic therapy improves disease-free survival in patients with breast cancer, but does not cure patients with advanced or metastatic disease, and fails to benefit the majority of patients with localized breast cancer. Intrinsic resistance to chemotherapy is emerging as a significant cause of treatment failure and evolving research has identified several potential causes of resistance, such as drug efflux pumps, disregulation of apoptosis and cancer stem cells. Building upon preclinical models, drugs designed to reverse resistance to therapy are currently under investigation in clinical trials for the treatment of breast cancer.

Targeting signal transduction pathways in metastatic breast cancer: a comprehensive review

Greater understanding of the underlying etiology and biology of breast cancer is enabling the clinical development of targeted therapies for metastatic breast cancer (MBC). Following the successful introduction of trastuzumab, the first human epidermal growth factor receptor (HER) biologically targeted therapy to become widely used in MBC patients, other agents have been developed. Novel agents include monoclonal antibodies such as pertuzumab, which bind to receptors on the cell surface, and tyrosine kinase inhibitors (TKIs) such as lapatinib, which target intracellular pathways such as that of the epidermal growth factor receptor. There is also growing clinical experience with antiangiogenic agents, particularly in combination with chemotherapy. These include the monoclonal antibody bevacizumab, which targets vascular endothelial growth factor receptor, and multitargeted TKIs with antiangiogenic and antiproliferative activities, such as sunitinib. Combination treatment with multiple agents targeting both the HER family and angiogenic pathways (e.g., trastuzumab plus bevacizumab) is also showing activity in the clinical setting. Despite recent advances, there are unanswered questions regarding the management of MBC with targeted agents. Future studies are necessary to determine the optimal combinations, doses, and schedules required to maximize clinical activity while minimizing toxicity. Despite the temptation to use a targeted agent in all patients, identification of patient subgroups most likely to benefit must be a key goal and will be critical to the successful future use of these treatments. The aim of this review is to summarize some of the key signaling pathways involved in tumor progression and some of the novel therapies that are in development for MBC.

Constitutive activation with overexpression of the mTORC2-phospholipase D1 pathway in uterine leiomyosarcoma and STUMP: morphoproteomic analysis with therapeutic implications

The mammalian target of rapamycin (mTOR) is centrally involved in growth, survival and metabolism. In cancer, mTOR is frequently hyperactivated and is a clinically validated target for therapy and drug development. Biologically, mTOR acts as the catalytic subunit of two functionally distinct complexes, called mTOR complex 1 (mTORC1) which is predominantly cytoplasmic in subcellular localization and mTOR complex 2 (mTORC2) which is both cytoplasmic and nuclear. mTORC1 is sensitive to the selective inhibitor rapamycin. By contrast, mTORC2 is relatively resistant to rapamycin. Moreover, its putative downstream effector, Akt phosphorylated on serine 473 represents a signal transduction pathway for tumor survival. Phospholipase D (PLD) and its product, phosphatidic acid (PA) have been implicated as an activator of mTOR signaling, including the direct phosphorylative activation of p70S6K atthreonine 389. The latter promotes cell cycle progression. In this study, we investigated the activation status and subcellular localization of mTOR and the relative expression of PLD1, as well as their downstream effectors in a spectrum of uterine smooth muscle tumors using normal myometria as controls. The results show significant activation with overexpression of phosphorylated mTORC2 complex in uterine leiomyosarcoma (ULMS) and smooth muscle tumors of uncertain malignant potential (STUMP) as evidenced by nuclear localization of p-mTOR (Ser 2448) in ULMS>STUMP>uterine leiomyoma and normal myometria (p<0.05) and with overexpression of PLD1(p<0.05). Cor-relatively, there are overexpressions of nuclear p-Akt (Ser 473) and nuclear p-p70S6K (Thr 389) in ULMS and STUMP (p<0.05). The activation with overexpression of components of the mTORC2-PLD1 pathway in ULMS and to a lesser degree in STUMP provides insight into their tumorigenic mechanisms. Thus the development of therapies designed to target mTORC2 and PLD1 activity may be beneficial in treating ULMS.

Novel therapeutic approaches to the treatment of metastatic breast cancer

Metastatic breast cancer is ultimately an incurable disease, although recent data have shown that its incidence is decreasing and that patients with metastatic breast cancer live longer. This improvement in survival seems to be linked with the introduction of new therapeutic agents, novel combinations of existing therapies and targeted therapies. Our increasing understanding of the molecular biology of metastatic disease has allowed the development of therapies aimed at specific molecular targets. Some of these have already been approved for the treatment of metastatic breast cancer in combination with cytotoxics, and others have shown promising results regarding disease-free survival, overall response rates and time to disease progression. Given the enormous amount of information about drug discovery in cancer, it is important to be familiar with the present state of the treatment of metastatic breast cancer. The purpose of this review is to provide an update on the development of some of the most promising novel agents and treatment strategies in metastatic breast cancer.

Nicotine stimulates PPARbeta/delta expression in human lung carcinoma cells through activation of PI3K/mTOR and suppression of AP-2alpha

We previously showed that nicotine stimulates non-small cell lung carcinoma (NSCLC) cell proliferation through nicotinic acetylcholine receptor (nAChR)-mediated signals. Activation of peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) has also been shown to induce NSCLC cell growth. Here, we explore the potential link between nicotine and PPARbeta/delta and report that nicotine increases the expression of PPARbeta/delta protein; this effect was blocked by an alpha7 nAChR antagonist (alpha-bungarotoxin), by alpha7 nAChR short interfering RNA, and by inhibitors of phosphatidylinositol 3-kinase (PI3K; wortmannin and LY294002) and mammalian target of rapamycin (mTOR; rapamycin). In contrast, this effect was enhanced by PUN282987, an alpha7 nAChR agonist. Silencing of PPARbeta/delta attenuated the stimulatory effect of nicotine on cell growth, which was overcome by transfection of an exogenous PPARbeta/delta expression vector. Of note, nicotine induced complex formation between alpha7 nAChR and PPARbeta/delta protein and increased PPARbeta/delta gene promoter activity through inhibition of AP-2alpha as shown by reduced AP-2alpha binding using electrophoretic gel mobility shift and chromatin immunoprecipitation assays. In addition, silencing of Sp1 attenuated the effect of nicotine on PPARbeta/delta. Collectively, our results show that nicotine increases PPARbeta/delta gene expression through alpha7 nAChR-mediated activation of PI3K/mTOR signals that inhibit AP-2alpha protein expression and DNA binding activity to the PPARbeta/delta gene promoter. Sp1 seems to modulate this process. This study unveils a novel mechanism by which nicotine promotes human lung carcinoma cell growth.

Inhibition of mTOR attenuates store-operated Ca2+ entry in cells from endarterectomized tissues of patients with chronic thromboembolic pulmonary hypertension

Pulmonary vascular remodeling occurs in patients with chronic thromboembolic pulmonary hypertension (CTEPH). One factor contributing to this vascular wall thickening is the proliferation of pulmonary artery smooth muscle cells (PASMC). Store-operated Ca(2+) entry (SOCE) and cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)) in PASMC are known to be important in cell proliferation and vascular remodeling in pulmonary hypertension. Rapamycin is widely known for its antiproliferative effects in injured coronary arteries. Although several reports have suggested favorable effects of rapamycin in animal models of pulmonary hypertension, no reports have been published to date in human tissues. Here we report that rapamycin has an inhibitory effect on SOCE and an antiproliferative effect on PASMC derived from endarterectomized tissues of CTEPH patients. Cells were isolated from endarterectomized tissues obtained from patients undergoing pulmonary thromboendarterectomy (PTE). Immunohistochemical analysis indicated high deposition of platelet-derived growth factor (PDGF) in tissue sections from PTE tissues and increased PDGF receptor expression. PDGF transiently phosphorylated Akt, mammalian target of rapamycin (mTOR), and p70S6 kinase in CTEPH cells from CTEPH patients. Acute treatment (30 min) with rapamycin (10 nM) slightly increased cyclopiazonic acid (10 microM)-induced Ca(2+) mobilization and significantly reduced SOCE. Chronic treatment (24 h) with rapamycin reduced Ca(2+) mobilization and markedly inhibited SOCE. The inhibitory effects of rapamycin on SOCE were less prominent in control cells. Rapamycin also significantly reduced PDGF-stimulated cell proliferation. In conclusion, the data from this study indicate the importance of the mTOR pathway in the development of pulmonary vascular remodeling in CTEPH and suggest a potential therapeutic benefit of rapamycin (or inhibition of mTOR) in these patients.

Intracellular parasitism with Toxoplasma gondii stimulates mammalian-target-of-rapamycin-dependent host cell growth despite impaired signalling to S6K1 and 4E-BP1

The Ser/Thr kinase mammalian-target-of-rapamycin (mTOR) is a central regulator of anabolism, growth and proliferation. We investigated the effects of Toxoplasma gondii on host mTOR signalling. Toxoplasma invasion of multiple cell types rapidly induced sustained mTOR activation that was restricted to infected cells, as determined by rapamycin-sensitive phosphorylation of ribosomal protein S6; however, phosphorylation of the growth-associated mTOR substrates 4E-BP1 and S6K1 was not detected. Infected cells still phosphorylated S6K1 and 4E-BP1 in response to insulin, although the S6K1 response was blunted. Parasite-induced S6 phosphorylation was independent of S6K1 and did not require activation of canonical mTOR-inducing pathways mediated by phosphatidylinositol 3-kinase-Akt and ERK. Host mTOR was localized in a vesicular pattern surrounding the parasitophorous vacuole, suggesting potential activation by phosphatidic acid in the vacuolar membrane. In spite of a failure to phosphorylate 4E-BP1 and S6K1, intracellular T. gondii triggered host cell cycle progression in an mTOR-dependent manner and progression of infected cells displayed increased sensitivity to rapamycin. Moreover, normal cell growth was maintained during parasite-induced cell cycle progression, as indicated by total cellular S6 levels. The Toxoplasma-infected cell provides a unique example of non-canonical mTOR activation supporting growth that is independent of signalling through either S6K1 or 4E-BP1.

Sirolimus-based immunosuppression therapy in liver transplantation for patients with hepatocellular carcinoma exceeding the Milan criteria

AIM

Sirolimus (SRL) acts as a primary immunosuppressant or antitumor agent. The aim of the present study was to evaluate the influence of SRL on the recurrence rate and survival of patients after orthotopic liver transplantation (OLT) for hepatocellular carcinoma (HCC) exceeding the Milan criteria.

MATERIALS AND METHODS

We retrospectively examined 73 consecutive patients who underwent OLT for HCC exceeding the Milan criteria from March 2004 through December 2005. Among them, 27 patients were treated with SRL-based immunosuppressive protocols after OLT, and 46 patients by an FK506-based protocol. Statistical analysis was based on the intent-to-treat method.

RESULTS

The 2 groups were comparable in all clinicopathologic parameters. The mean overall survival was 594 +/- 35 days in the SRL group and 480 +/- 42 days in the FK506 group (P = .011); the mean disease-free survival period was 519 +/- 43 days in the SRL group and 477 +/- 48 days in the FK506 group (P = .234). Multivariate analysis revealed Child's status (P = .004) and immunosuppressive protocol (P = .015) were the significant factors affecting overall survival. Only microvascular invasion (P = .004) was significantly associated with disease-free survival. Among 24 surviving patient in the SRL group, 2 patients had SRL discontinued for toxicity; 10 had SRL monotherapy immunosuppression.

CONCLUSION

The SRL-based immunosuppressive protocol improved the overall survival of patients after OLT for HCC exceeding the Milan criteria, probably by postponing recurrence and with better tolerability.

The serine 2481-autophosphorylated form of mammalian Target Of Rapamycin (mTOR) is localized to midzone and midbody in dividing cancer cells

Using a high-resolution, automated confocal high-content imaging system, we investigated the sub-cellular localization of the Serine 2481-autophosphorylated form of mTOR (PP-mTOR(Ser2481)) during mitosis and cytokinesis in human cancer cells. PP-mTOR(Ser2481) exhibited a punctate nuclear distribution in interphase cancer cells, with the number of PP-mTOR(Ser2481) nuclear speckles positively relating with the proliferative capacity of cancer cells. PP-mTOR(Ser2481) expression dynamically rearranged within the cytoplasm in a close association near and between separating chromosomes during early stages of mitosis. Towards the end of anaphase and in telophase, PP-mTOR(Ser2481) drastically focused on the midzone and ultimately in the centre of the midbody at the presumptive cleavage furrow. In cells at cytokinesis, PP-mTOR(Ser2481) appeared as a doublet facing each other at the apical ends of two daughter cells. Three-dimensional analysis confirmed that PP-mTOR(Ser2481) positioned at a ring structure wrapped round by microtubule bundles to connect daughter cells. These results reveal for the first time that PP-mTOR(Ser2481) may be unexpectedly involved in the terminal stages of cytokinesis.