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Multidrug resistance (MDR) has become a major obstacle in the treatment of cancer, and is associated with mechanisms such as increased drug outflow, reduction of apoptosis, and/or altered drug metabolism. These problems can be mitigated by the coadministration of agents known as chemosensitizers, as they can reverse resistance to anticancer drugs and eventually resensitize cancer cells. We explore the chemosensitizing effect of Achillin, a guaianolide-type sesquiterpene lactone isolated from the Mexican medicinal plant Artemisia ludovisiana, to reverse MDR in Hep3B/PTX cells of hepatocellular carcinoma, which present resistance to paclitaxel (PTX). Achillin showed an important effect as chemosensitizer; indeed, the cytotoxic effect of PTX (25 nM) was enhanced, and the induction of G2/M phase cell cycle arrest and apoptosis were potentiated when combining with Achillin (100 µM). In addition, we observed that Achillin decreases P-gp levels and increases the intracellular retention of doxorubicin in Hep3B/PTX cells; in addition, homology structural modeling and molecular docking calculations predicted that Achillin interacts in two regions (M-site and R-site) of transporter drug efflux P-glycoprotein (P-gp). Our results suggest that the chemosensitizer effect demonstrated for Achillin could be associated with P-gp modulation. This work also provides useful information for the development of new therapeutic agents from guaianolide-type sesquiterpene lactones like Achillin.

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Propolis is a natural product obtained from bees, used since ancient times for its multiple pharmacological properties. Several evidences indicate that the antiproliferative effect of propolis against different cancer cell lines can be ascribed to its components. However, little is known about the possible use of this natural product in the treatment of chemo-resistant tumors. Combination experiments were carried out in order to study the ability of Cuban propolis extracts (CP) and its main component (nemorosone) to chemosensitize doxorubicin-resistant human colon carcinoma cells (LoVo Dox) compared to the sensitive cells (LoVo). Antiproliferative effect was determined by MTT assay after 24, 48 and 72 h exposure. Synergistic, additive or antagonistic effects of different combined treatments (CP-Dox and nemorosone-Dox), was evaluated by isobologram-combination index method. The interaction mechanisms between CP or nemorosone with doxorubicin were studied by flow cytometry to investigate cell death pathway and cell cycle arrest. Reactive oxygen species production (ROS) and mitochondrial membrane potential (ΔΨm) modification were also evaluated. Data showed that both CP and its main component nemorosone were able to reduce cell proliferation in a concentration- and time-dependent manner. Combined treatments induced a cell growth inhibition with a significantly synergistic antiproliferative and cytotoxic effect. Co-treatments induced also cell cycle arrest which results in apoptosis by a marked ROS production and drastic alteration of ΔΨm. In summary, our findings evidence the potential role of Cuban propolis extracts and their main component nemorosone as new chemosensitizing agents against drug-resistant human colon carcinoma cells.

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Nanotechnology has recently emerged as a promising tool in biomedicine research. An important branch of nanotechnology is drug delivery and drug targeting using a wide range of biomaterials with promising potential applications in cancer research. The aim of this review is to provide an overview of the evolution of nanotechnology in cancer therapy, exemplified by a myriad of applications in drug delivery, tumor targeting and reversal of ATP-binding cassette drug transporter-mediated multidrug resistance (MDR) in cancer cells by the biomaterials used in nanoformulations. Special attention will be focused on liver cancer, especially, on hepatocellular carcinoma, which is among the malignancies with the poorest prognosis due to its extremely "difficult-to-treat" nature related to its high recurrence rate and MDR phenotype.

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Melanoma incidence increases every year worldwide and is responsible for 80% of skin cancer deaths. Due to its metastatic potential and resistance to almost any treatments such as chemo, radio, immune and targeted-therapy, the patients still have a poor prognosis, especially at metastatic stage. Considering that, it is crucial to find new therapeutic approaches to overcome melanoma resistance. Here we investigated the effect of cisplatin (CDDP), one of the chemotherapeutic agents used for melanoma treatment, in association with nutritional deprivation in murine melanoma cell lines. Cell death and autophagy were evaluated after the treatment with cisplatin, nutritional deprivation and its association using an in vitro model of murine melanocytes malignant transformation to metastatic melanoma. Our results showed that nutritional deprivation augmented cell death induced by cisplatin in melanoma cells, especially at the metastatic subtype, with slight effects on melanocytes. Mechanistic studies revealed that although autophagy was present at high levels in basal conditions in melanoma cells, was not essential for cell death process that involved mitochondrial damage, reactive oxygen species production and possible glycolysis inhibition. In conclusion, nutritional shortage in combination with chemotherapeutic drugs as cisplatin can be a valuable new therapeutic strategy to overcome melanoma resistance.

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Introducción: la mangiferina posee diferentes propiedades farmacológicas, y otras están por ser investigadas, tal como su actividad antitumoral como agente adyuvante a la quimioterapia antineoplásica convencional en la terapia combinada. Objetivo: evaluar el efecto antiproliferativo de la mangiferina sola y combinada con concentraciones bajas de agentes quimioterapéuticos. Métodos: las líneas celulares de carcinoma de colon de ratón CT26.WT y normal de ovario de hámster chino CHO-K1, se trataron con mangiferina en combinación con cisplatino y 5-fluorouracilo bajo diferentes esquemas de tratamiento (secuencial y simultáneo), a diferentes concentraciones y tiempos de incubación. La viabilidad celular se determinó por el ensayo de MTT. Resultados: la mangiferina (1-200 µg/mL) no fue citotóxica para ambas líneas celulares. El cotratamiento secuencial con mangiferina (1-200 µg/mL) por 3 h y cisplatino a concentraciones no citotóxicas (1 µM y 5 µM) durante 72 h, mostró un incremento significativo de la muerte celular en CT26.WT, sin inducir incremento significativo de la muerte en células CHO-K1, a concentraciones bajas de ambos compuestos. En el caso de los cotratamientos con mangiferina y 5-fluorouracilo (0,1 µM y 0,5 µM), se incrementó significativamente la muerte celular en los cotratamientos simultáneo por 72 h y secuencial 5-fluorouracilo 72 h y mangiferina 24 h en células CT26.WT; pero solo en este último, no se incrementó significativamente la muerte celular en CHO-K1. Conclusiones: la mangiferina en combinación con concentraciones bajas no citotóxicas de cisplatino y 5-fluorouracilo, promueve la muerte celular e incrementa la citotoxicidad de estos agentes quimioterapéuticos en las condiciones de experimentación realizadas(AU)

Introduction: mangiferin has several pharmacological properties, but others remain to be deeply explored, such as antitumor activity since it may serve as adjuvant agent in conventional antitumoral chemotherapy in a combined treatment. Objective: to evaluate the antiproliferative effect of the use of mangiferin alone and in combination with low concentrations of chemotherapeutic agents. Methods: the CT26.WT mouse colon carcinoma and the CHO-K1 hamster ovary normal cell lines were treated with mangiferin in combination with cisplatin and 5-fluorouracil in several treatment schedules (sequential and simultaneous), at different concentrations and incubation times. The cell viability was evaluated by MTT assay. Results: mangiferin (1-200 µg/mL) was not cytotoxic in both cell lines. Mangiferin (1-200 µg/mL) for 3h plus cisplatin at not citotoxic concentrations (1 µM and 5 µM) for 72 h in sequential combined treatment showed a significant increase of cell death in CT26.WT, without inducing significant increase of cell death in CHO-K1 cells at low concentrations of both compounds. In the case of combined mangiferina and 5-fluorouracil (0,1 µM and 0,5 µM) treatments, cell death rose in a significant way in simultaneous combined treatments for 72 h where as sequential combined therapy with 5-fluorouracil for 72 h plus mangiferin for 24 h in CT26.WT cells, a significant rise was not induced in the cell line death of CHO-K1 hamster Conclusions: mangiferin in combination with low non cytotoxic concentrations of cisplatin and 5-fluorouracil promotes cell death and increases the cytotoxicity of these chemotherapeutic agents in experimental conditions of this study(AU)

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INTRODUCCIÓN: la mangiferina posee diferentes propiedades farmacológicas, y otras están por ser investigadas, tal como su actividad antitumoral como agente adyuvante a la quimioterapia antineoplásica convencional en la terapia combinada. OBJETIVO: evaluar el efecto antiproliferativo de la mangiferina sola y combinada con concentraciones bajas de agentes quimioterapéuticos. MÉTODOS: las líneas celulares de carcinoma de colon de ratón CT26.WT y normal de ovario de hámster chino CHO-K1, se trataron con mangiferina en combinación con cisplatino y 5-fluorouracilo bajo diferentes esquemas de tratamiento (secuencial y simultáneo), a diferentes concentraciones y tiempos de incubación. La viabilidad celular se determinó por el ensayo de MTT. RESULTADOS: la mangiferina (1-200 µg/mL) no fue citotóxica para ambas líneas celulares. El cotratamiento secuencial con mangiferina (1-200 µg/mL) por 3 h y cisplatino a concentraciones no citotóxicas (1 µM y 5 µM) durante 72 h, mostró un incremento significativo de la muerte celular en CT26.WT, sin inducir incremento significativo de la muerte en células CHO-K1, a concentraciones bajas de ambos compuestos. En el caso de los cotratamientos con mangiferina y 5-fluorouracilo (0,1 µM y 0,5 µM), se incrementó significativamente la muerte celular en los cotratamientos simultáneo por 72 h y secuencial 5-fluorouracilo 72 h y mangiferina 24 h en células CT26.WT; pero solo en este último, no se incrementó significativamente la muerte celular en CHO-K1. CONCLUSIONES: la mangiferina en combinación con concentraciones bajas no citotóxicas de cisplatino y 5-fluorouracilo, promueve la muerte celular e incrementa la citotoxicidad de estos agentes quimioterapéuticos en las condiciones de experimentación realizadas(AU)

INTRODUCTION: mangiferin has several pharmacological properties, but others remain to be deeply explored, such as antitumor activity since it may serve as adjuvant agent in conventional antitumoral chemotherapy in a combined treatment. OBJECTIVE: to evaluate the antiproliferative effect of the use of mangiferin alone and in combination with low concentrations of chemotherapeutic agents. METHODS: the CT26.WT mouse colon carcinoma and the CHO-K1 hamster ovary normal cell lines were treated with mangiferin in combination with cisplatin and 5-fluorouracil in several treatment schedules (sequential and simultaneous), at different concentrations and incubation times. The cell viability was evaluated by MTT assay. RESULTS: mangiferin (1-200 µg/mL) was not cytotoxic in both cell lines. Mangiferin (1-200 µg/mL) for 3h plus cisplatin at not citotoxic concentrations (1 µM and 5 µM) for 72 h in sequential combined treatment showed a significant increase of cell death in CT26.WT, without inducing significant increase of cell death in CHO-K1 cells at low concentrations of both compounds. In the case of combined mangiferina and 5-fluorouracil (0,1 µM and 0,5 µM) treatments, cell death rose in a significant way in simultaneous combined treatments for 72 h whereas sequential combined therapy with 5-fluorouracil for 72 h plus mangiferin for 24 h in CT26.WT cells, a significant rise was not induced in the cell line death of CHO-K1 hamster CONCLUSIONS: mangiferin in combination with low non cytotoxic concentrations of cisplatin and 5-fluorouracil promotes cell death and increases the cytotoxicity of these chemotherapeutic agents in experimental conditions of this study(AU)

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In tumor cells the effectiveness of anti-neoplastic agents that cause cell death by induction of DNA damage is influenced by DNA repair activity. RAD50 protein plays key roles in DNA double strand breaks repair (DSBs), which is crucial to safeguard genome integrity and sustain tumor suppression. However, its role as a potential therapeutic target has not been addressed in breast cancer. Our aim in the present study was to analyze the expression of RAD50 protein in breast tumors, and evaluate the effects of RAD50-targeted inhibition on the cytotoxicity exerted by cisplatin and anthracycline and taxane-based therapies in breast cancer cells. Immunohistochemistry assays on tissue microarrays indicate that the strong staining intensity of RAD50 was reduced in 14% of breast carcinomas in comparison with normal tissues. Remarkably, RAD50 silencing by RNA interference significantly enhanced the cytotoxicity of cisplatin. Combinations of cisplatin with doxorubicin and paclitaxel drugs induced synergistic effects in early cell death of RAD50-deficient MCF-7, SKBR3, and T47D breast cancer cells. Furthermore, we found an increase in the number of DSBs, and delayed phosphorylation of histone H2AX after cisplatin treatment in RAD50-silenced cells. These cellular events were associated to a dramatical increase in the frequency of chromosomal aberrations and a decrease of cell number in metaphase. In conclusion, our data showed that RAD50 abrogation impairs DNA damage response and sensitizes breast cancer cells to cisplatin-combined therapies. We propose that the development and use of inhibitors to manipulate RAD50 levels might represent a promising strategy to sensitize breast cancer cells to DNA damaging agents.

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Small cell lung cancer (SCLC) is an aggressive disease, representing 15 percent of all cases of lung cancer, has high metastatic potential and low prognosis that urgently demands the development of novel therapeutic approaches. One of the proposed approaches has been the down-regulation of BCL2, with poorly clarified and controversial therapeutic value regarding SCLC. The use of anti-BCL2 small interfering RNA (siRNA) in SCLC has never been reported. The aim of the present study was to select and test the in vitro efficacy of anti-BCL2 siRNA sequences against the protein and mRNA levels of SCLC cells, and their effects on cytotoxicity and chemosensitization. Two anti-BCL2 siRNAs and the anti-BCL2 G3139 oligodeoxynucleotide (ODN) were evaluated in SCLC cells by the simultaneous determination of Bcl-2 and viability using a flow cytometry method recently developed by us in addition to Western blot, real-time reverse-transcription PCR, and cell growth after single and combined treatment with cisplatin. In contrast to previous reports about the use of ODN, a heterogeneous and up to 80 percent sequence-specific Bcl-2 protein knockdown was observed in the SW2, H2171 and H69 SCLC cell lines, although without significant sequence-specific reduction of cell viability, cell growth, or sensitization to cisplatin. Our results question previous data generated with antisense ODN and supporting the present concept of the therapeutic interest in BCL2 silencing per se in SCLC, and support the growing notion of the necessity of a multitargeting molecular approach for the treatment of cancer.

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