Sequential events of apoptosis involving docetaxel, a microtubule-interfering agent: a cytometric study

Exploring the broad-spectrum pharmacological activity of two less studied Australian native fruits: chemical characterisation using LCMS-driven metabolomics

Australian fruits such as native currant (Acrotriche depressa) and lemon aspen (Acronychia acidula) are under-examined in terms of their therapeutic potential. In this study, the in vitro antiproliferative activity of native currant and lemon aspen extracts (water and ethanol) against MCF7 breast adenocarcinoma cells was determined using the Alamar blue assay. The most potent extracts (native currant water, NC-W; native currant ethanol, NC-Et; lemon aspen ethanol, LA-Et) were further evaluated using flow cytometry to detect the potential induction of apoptosis in MCF7 cells whereas 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) assay was implemented to understand the impact of the extracts on the intracellular reactive oxygen species (ROS) levels in MCF7 cells. Furthermore, the antioxidant activity of the extracts was assessed using ABTS [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate)], and CUPRAC (cupric reducing antioxidant capacity) assays. The antimicrobial susceptibility testing of NC-W, NC-Et, and LA-Et was carried out against Gram-positive (Staphylococcus aureus), Gram-negative (Escherichia coli), and yeast (Candida albicans) strains using a resazurin-based assay. Additionally, potential metabolites in the NC-W and NC-Et extracts were analysed with liquid chromatography-mass spectrometry (LC-MS) driven metabolomics and chemometrics to spot differential and major metabolites. A dose-dependent antiproliferative activity was conferred by the NC extracts against MCF7 cells. Of the two LA extracts, only LA-Et showed a dose-dependent antiproliferative activity at higher concentrations. Both NC extracts and LA-Et induced apoptosis in MCF7 cells. None of the extracts increased the production of ROS significantly in MCF7 cells compared to the untreated control. A dose-dependent antioxidant activity was observed in both antioxidant assays. Both NC and LA extracts showed a similar minimum inhibitory concentration (MIC) value against S. aureus. Only LA-Et showed activity against E. coli, while NC-W and NC-Et were less active. All extracts showed MIC values of >1500 μg mL-1 against C. albicans. The metabolomics analysis revealed an abundance of flavonoids, fatty acyl derivatives, carbohydrates, carboxylic acids and their derivatives, and alkaloid compounds as potential bioactive metabolites in the NC extracts. In conclusion, both NC and LA showed antiproliferative (against MCF7 breast adenocarcinoma cells through the induction of apoptosis), strong antioxidant and minimal antimicrobial properties.

The lipid metabolism remodeling: A hurdle in breast cancer therapy

Lipids, as one of the three primary energy sources, provide energy for all cellular life activities. Lipids are also known to be involved in the formation of cell membranes and play an important role as signaling molecules in the intracellular and microenvironment. Tumor cells actively or passively remodel lipid metabolism, using the function of lipids in various important cellular life activities to evade therapeutic attack. Breast cancer has become the leading cause of cancer-related deaths in women, which is partly due to therapeutic resistance. It is necessary to fully elucidate the formation and mechanisms of chemoresistance to improve breast cancer patient survival rates. Altered lipid metabolism has been observed in breast cancer with therapeutic resistance, indicating that targeting lipid reprogramming is a promising anticancer strategy.

Therapeutic strategy for oncovirus-mediated oral cancer: A comprehensive review

Oral cancer is a neoplastic disorder of the oral cavities, including the lips, tongue, buccal mucosa, and lower and upper gums. Oral cancer assessment entails a multistep process that requires deep knowledge of the molecular networks involved in its progression and development. Preventive measures including public awareness of risk factors and improving public behaviors are necessary, and screening techniques should be encouraged to enable early detection of malignant lesions. Herpes simplex virus (HSV), human papillomavirus (HPV), Epstein-Barr virus (EBV), and Kaposi sarcoma-associated herpesvirus (KSHV) are associated with other premalignant and carcinogenic conditions leading to oral cancer. Oncogenic viruses induce chromosomal rearrangements; activate signal transduction pathways via growth factor receptors, cytoplasmic protein kinases, and DNA binding transcription factors; modulate cell cycle proteins, and inhibit apoptotic pathways. In this review, we present an up-to-date overview on the use of nanomaterials for regulating viral proteins and oral cancer as well as the role of phytocompounds on oral cancer. The targets linking oncoviral proteins and oral carcinogenesis were also discussed.

BRCA1 overexpression attenuates breast cancer cell growth and migration by regulating the pyruvate kinase M2-mediated Warburg effect via the PI3K/AKT signaling pathway

This work explored the mechanism of the effect of breast-cancer susceptibility gene 1 (BRCA1) on the metabolic characteristics of breast cancer cells, including the Warburg effect and its specific signaling. We transfected MCF-7 cells with a BRCA1-encoding LXSN plasmid or PKM2 siRNA and examined cancer cell metabolism using annexin V staining, inhibitory concentration determination, Western blotting, glucose uptake and lactic acid content measurements, and Transwell assays to assess glycolytic activity, cell apoptosis, and migration, and sensitivity to anti-cancer treatment. The BRCA1-expressing MCF-7 cells demonstrated low PKM2 expression and decreased glycolytic activity (downregulated hexokinase 2 (HK2) expression, upregulated isocitrate dehydrogenase 1 (IDH1) expression, and reduced O₂ and glucose consumption and lactate production) via regulation of PI3K/AKT pathway compared with the empty LXSN group. BRCA1 transfection slightly increased apoptotic activity, decreased cell migration, and increased the IC₅₀ index for doxorubicin, paclitaxel, and cisplatin. Inhibiting PKM2 using siRNA attenuated the IC₅₀ index for doxorubicin, paclitaxel, and cisplatin compared with the control. Inhibiting PKM2 activated PI3K/AKT signaling, increased apoptosis, and decreased MCF-7 cell migration. Our data suggest that BRCA1 overexpression reverses the Warburg effect, inhibits cancer cell growth and migration, and enhances the sensitivity to anti-cancer treatment by decreasing PKM2 expression regulated by PI3K/AKT signaling. These novel metabolic findings represent a potential mechanism by which BRCA1 exerts its inhibitory effect on breast cancer.

A novel docetaxel derivative exhibiting potent anti-tumor activity and high safety in preclinical animal models

As a taxoid agent, docetaxel (DTX) exhibits potent antitumor activity. However, severe toxic side effects and acquired multidrug resistance represent its clinical challenges. Herein, a novel docetaxel derivative (DTX-AI) is synthesized via the nucleophilic addition reaction of 4-acetylphenyl carbamate at the C10 position of the DTX framework. DTX-AI exhibits superior cytotoxicity and a higher apoptotic ratio in vitro against DTX-sensitive tumor cells (MCF-7, HeLa and A549 cells) and even DTX-resistant ones (HeLa/PTX cells), but displays less toxicity against normal cells (MRC-5 and L929 cells) compared with DTX. DTX-AI can effectively suppress the growth of HeLa-tumor xenografts in vivo and even induce complete tumor regression. Furthermore, DTX-AI shows sustained effects on the inhibition of A549-tumor xenograft growth and no obvious recurrence, even after the drug administration was stopped for 30 d. More importantly, DTX-AI has significantly reduced long-term and short-term animal toxicity and extended the survival of mice (100%) compared with DTX (0%). DTX-AI is expected to be a promising 'me-better' anti-tumor drug with higher efficiency and lower toxicity for improved chemotherapy in the clinic.

Docetaxel remodels prostate cancer immune microenvironment and enhances checkpoint inhibitor-based immunotherapy

Background: Prostate cancer is usually considered as immune "cold" tumor with poor immunogenic response and low density of tumor-infiltrating immune cells, highlighting the need to explore clinically actionable strategies to sensitize prostate cancer to immunotherapy. In this study, we investigated whether docetaxel-based chemohormonal therapy induces immunologic changes and potentiates checkpoint blockade immunotherapy in prostate cancer. Methods: We performed transcriptome and histopathology analysis to characterize the changes of prostate cancer immune microenvironment before and after docetaxel-based chemohormonal therapy. Furthermore, we investigated the therapeutic benefits and underlying mechanisms of chemohormonal therapy combined with anti-PD1 blockade using cellular experiments and xenograft prostate cancer models. Finally, we performed a retrospective cohort analysis to evaluate the antitumor efficacy of anti-PD1 blockade alone or in combination with docetaxel-based chemotherapy. Results: Histopathology assessments on patient samples confirmed the enrichment of tumor-infiltrating T cells after chemohormonal therapy. Moreover, we found that docetaxel activated the cGAS/STING pathway in prostate cancer, subsequently induced IFN signaling, resulting in lymphocytes infiltration. In a xenograft mouse model, docetaxel-based chemohormonal therapy prompted the intratumoral infiltration of T cells and upregulated the abundance of PD1 and PD-L1, thereby sensitizing mouse tumors to the anti-PD1 blockade. To determine the clinical significance of these results, we retrospectively analyzed a cohort of 30 metastatic castration-resistant prostate cancer patients and found that docetaxel combined with anti-PD1 blockade resulted in better prostate-specific antigen progression-free survival when compared with anti-PD1 blockade alone. Conclusions: Our study demonstrates that docetaxel activates the antitumoral immune response and facilitates T cell infiltration in a cGAS/STING-dependent manner, providing a combination immunotherapy strategy that would improve the clinical benefits of immunotherapy.

Fatty acid oxidation protects cancer cells from apoptosis by increasing mitochondrial membrane lipids

Overcoming resistance to chemotherapies remains a major unmet need for cancers, such as triple-negative breast cancer (TNBC). Therefore, mechanistic studies to provide insight for drug development are urgently needed to overcome TNBC therapy resistance. Recently, an important role of fatty acid β-oxidation (FAO) in chemoresistance has been shown. But how FAO might mitigate tumor cell apoptosis by chemotherapy is unclear. Here, we show that elevated FAO activates STAT3 by acetylation via elevated acetyl-coenzyme A (CoA). Acetylated STAT3 upregulates expression of long-chain acyl-CoA synthetase 4 (ACSL4), resulting in increased phospholipid synthesis. Elevating phospholipids in mitochondrial membranes leads to heightened mitochondrial integrity, which in turn overcomes chemotherapy-induced tumor cell apoptosis. Conversely, in both cultured tumor cells and xenograft tumors, enhanced cancer cell apoptosis by inhibiting ASCL4 or specifically targeting acetylated-STAT3 is associated with a reduction in phospholipids within mitochondrial membranes. This study demonstrates a critical mechanism underlying tumor cell chemoresistance.

Effect of docetaxel on the regulation of proliferation and apoptosis of human prostate cancer cells

Prostate cancer is a common type of malignancy. Given the complexity of prostate cancer and the pressing challenge of chemoresistance, the current study was conducted to investigate the effect of docetaxel (Doc) on androgen receptor (AR)‑dependent and AR‑independent prostate cancers cells. Subsequent experiments were designed to explore the mechanism underlying the Doc‑induced apoptosis. Three different human prostate cancer cell lines, namely PC‑3, LNCaP and DU‑145, were exposed to various concentrations of Doc. The cytotoxic effects of Doc were evaluated by an MTT assay, while apoptosis and cell cycle distribution were determined by flow cytometric analysis of cells stained with Annexin V‑FITC and propidium iodide. Western blot assay was also used to measure the protein levels of B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated death promoter (Bad), total protein kinase B (Akt), phospho‑Akt and caspase‑3/9. Doc induced cytotoxicity in all three cell lines in a dose‑dependent manner. The half maximal inhibitory concentration values for the effect of Doc on PC‑3, DU‑145 and LNCaP cells were 3.72, 4.46 and 1.13 nM, respectively. Furthermore, the results indicated a significant difference in Doc sensitivity between AR‑dependent and AR‑independent prostate cancer cells. Evaluation of key gene expression at protein levels revealed a notable decrease in antiapoptotic Bcl‑2 and p‑Akt levels, along with a significant increase in pro‑apoptotic Bad, caspase‑3 and caspase‑9 levels. Therefore, Doc may induce cell apoptosis in prostate cancer via various pathways.

Multifunctional Glycoconjugate Assisted Nanocrystalline Drug Delivery for Tumor Targeting and Permeabilization of Lysosomal-Mitochondrial Membrane

Nanotechnology has emerged as the most successful strategy for targeting drug payloads to tumors with the potential to overcome the problems of low concentration at the target site, nonspecific distribution, and untoward toxicities. Here, we synthesized a novel polymeric conjugate comprising chondroitin sulfate A and polyethylene glycol using carbodiimide chemistry. We further employed this glycoconjugate possessing the propensity to provide stability, stealth effects, and tumor targeting via CD44 receptors, all in one, to develop a nanocrystalline system of docetaxel (DTX@CSA-NCs) with size < 200 nm, negative zeta potential, and 98% drug content. Taking advantage of the enhanced permeability and retention effect coupled with receptor mediated endocytosis, the DTX@CSA-NCs cross the peripheral tumor barrier and penetrate deeper into the cells of tumor mass. In MDA-MB-231 cells, this enhanced cellular uptake was observed to exhibit a higher degree of cytotoxicity and arrest in the G2 phase in a time dependent fashion. Acting via a mitochondrial-lysosomotropic pathway, DTX@CSA-NCs disrupted the membrane potential and integrity and outperformed the clinically used formulation. Upon intravenous administration, the DTX@CSA-NCs showed better pharmacokinetic profile and excellent 4T1 induced tumor inhibition with significantly less off target toxicity. Thus, this glycoconjugate stabilized nanocrystalline formulation has the potential to take nano-oncology a step forward.

Targeting the stress oncoprotein LEDGF/p75 to sensitize chemoresistant prostate cancer cells to taxanes

Prostate cancer (PCa) is associated with chronic prostate inflammation resulting in activation of stress and pro-survival pathways that contribute to disease progression and chemoresistance. The stress oncoprotein lens epithelium-derived growth factor p75 (LEDGF/p75), also known as DFS70 autoantigen, promotes cellular survival against environmental stressors, including oxidative stress, radiation, and cytotoxic drugs. Furthermore, LEDGF/p75 overexpression in PCa and other cancers has been associated with features of tumor aggressiveness, including resistance to cell death and chemotherapy. We report here that the endogenous levels of LEDGF/p75 are upregulated in metastatic castration resistant prostate cancer (mCRPC) cells selected for resistance to the taxane drug docetaxel (DTX). These cells also showed resistance to the taxanes cabazitaxel (CBZ) and paclitaxel (PTX), but not to the classical inducer of apoptosis TRAIL. Silencing LEDGF/p75 effectively sensitized taxane-resistant PC3 and DU145 cells to DTX and CBZ, as evidenced by a significant decrease in their clonogenic potential. While TRAIL induced apoptotic blebbing, caspase-3 processing, and apoptotic LEDGF/p75 cleavage, which leads to its inactivation, in both taxane-resistant and -sensitive PC3 and DU145 cells, treatment with DTX and CBZ failed to robustly induce these signature apoptotic events. These observations suggested that taxanes induce both caspase-dependent and -independent cell death in mCRPC cells, and that maintaining the structural integrity of LEDGF/p75 is critical for its role in promoting taxane-resistance. Our results further establish LEDGF/p75 as a stress oncoprotein that plays an important role in taxane-resistance in mCRPC cells, possibly by antagonizing drug-induced caspase-independent cell death.

Adjuvant Therapy with Silibinin Improves the Efficacy of Paclitaxel and Cisplatin in MCF-7 Breast Cancer Cells

Herbal-derived medicines have introduced as sources of novel drugs due to minimum systemic side effects. Silibinin as a flavonoid compound has showed with effective chemotherapeutic effects on different cancers. Here, we investigated the impact of combination therapy of silibinin, with paclitaxel and cisplatin in inhibition of proliferation and induction of apoptosis in MCF-7 cells. Cell proliferation was assessed by MTT assay and the percentage of apoptotic cells was measured using flowcytometric assay. Understand of molecular mechanism of this combination related to apoptotic pathway were evaluated by Real Time RT-PCR assays. The IC₅₀ values for silibinin, paclitaxel and cisplatin were 160 ± 22.2 µM, 33.7 ± 4.2 nM and 3.2 ± 0.5 µM, respectively. Paclitaxel and cisplatin induced higher percentage of apoptosis in MCF-7 (P < 0.05). Treatment of cell line with combination of silibinin and paclitaxel or cisplatin showed enhanced early apoptosis 56% and 61%, respectively (P < 0.05). Gene expression patterns demonstrated a significant decrease in anti-apoptotic Bcl-2 with increase in pro-apoptotic Bax, P53, BRCA1 and ATM mRNA levels. Taken together combination therapy of breast cancer cells by applying paclitaxel or cisplatin with silibinin synergistically increases the anti-proliferative effect of single agents.

Application of sequential factorial design and orthogonal array composite design (OACD) to study combination of 5 prostate cancer drugs

Prostate cancer is one of the most common cancers among men in the United States. It is also a major leading cause of cancer death among men of all races. In order to treat prostate cancer, drug combinations are often applied. Drug combinations target at different pathways of cells can potentially lead to higher efficacy and lower toxicity due to drug synergy. In this paper, we sequentially applied a two-level design and a follow-up orthogonal array composite design (OACD) to investigate combinations of five anti-cancer drugs, namely, doxorubicin, docetaxel, paclitaxel, cis-dichlorodiamine platinum and dihydroartemisinin. Our initial screening using a two-level full factorial design identified doxorubicin and docetaxel as the most significant drugs. A follow-up experiment with an OACD revealed more complicated drug interactions among these 5 anti-cancer drugs. Quadratic effects of doxorubicin and paclitaxel appeared to be significant. A further investigation on contour plots of all the two-drug pairs indicated that combination of doxorubicin and docetaxel are the most effective companion, while the combination of cis-dichlorodiamine platinum and dihydroartemisinin showed unknown antagonistic effects which diminished the individual drug anti-cancer efficacy. These observations have significant practical implications in the understanding of anti-cancer drug mechanism that can facilitate clinical practice of better drug combinations.

Potential hepatic toxicity of buprofezin at sublethal concentrations: ROS-mediated conversion of energy metabolism

Buprofezin is known for its broad-spectrum action and environmental safety. The popularity of buprofezin has raised concerns about its potentially adverse effects on human health and risk to the environment. In this study, we first identified the liver as one of the major organs in which buprofezin accumulated, and we detected a severe oxidative stress response. Next, we demonstrated that sublethal concentrations of buprofezin promoted the conversion of energy metabolism from the aerobic tricarboxylic acid (TCA) cycle and oxidative phosphorylation to anaerobic glycolysis. Importantly, reactive oxygen species (ROS) generation partially accounted for the shunting of the energy metabolism through the buprofezin-mediated inhibition of cytochrome c oxidase activity. ROS directly perturbed the activities of several key TCA cycle enzymes, stimulated glycolysis, and indirectly disturbed the activity of the respiratory chain complex by altering mitochondrial DNA (mtDNA). These findings clarify the potential mechanisms of buprofezin toxicity and provide biomarkers for buprofezin-mediated hepatotoxicity at sublethal concentrations.

In Silico Oncology: Quantification of the In Vivo Antitumor Efficacy of Cisplatin-Based Doublet Therapy in Non-Small Cell Lung Cancer (NSCLC) through a Multiscale Mechanistic Model

The 5-year survival of non-small cell lung cancer patients can be as low as 1% in advanced stages. For patients with resectable disease, the successful choice of preoperative chemotherapy is critical to eliminate micrometastasis and improve operability. In silico experimentations can suggest the optimal treatment protocol for each patient based on their own multiscale data. A determinant for reliable predictions is the a priori estimation of the drugs’ cytotoxic efficacy on cancer cells for a given treatment. In the present work a mechanistic model of cancer response to treatment is applied for the estimation of a plausible value range of the cell killing efficacy of various cisplatin-based doublet regimens. Among others, the model incorporates the cancer related mechanism of uncontrolled proliferation, population heterogeneity, hypoxia and treatment resistance. The methodology is based on the provision of tumor volumetric data at two time points, before and after or during treatment. It takes into account the effect of tumor microenvironment and cell repopulation on treatment outcome. A thorough sensitivity analysis based on one-factor-at-a-time and latin hypercube sampling/partial rank correlation coefficient approaches has established the volume growth rate and the growth fraction at diagnosis as key features for more accurate estimates. The methodology is applied on the retrospective data of thirteen patients with non-small cell lung cancer who received cisplatin in combination with gemcitabine, vinorelbine or docetaxel in the neoadjuvant context. The selection of model input values has been guided by a comprehensive literature survey on cancer-specific proliferation kinetics. The latin hypercube sampling has been recruited to compensate for patient-specific uncertainties. Concluding, the present work provides a quantitative framework for the estimation of the in-vivo cell-killing ability of various chemotherapies. Correlation studies of such estimates with the molecular profile of patients could serve as a basis for reliable personalized predictions.

Less than 14% of medically treated patients with locally advanced and metastatic non-small cell lung cancer are expected to be alive 5 years after diagnosis. Standard therapeutic strategies include the administration of two drugs in combination, aiming at shrinking the tumor before surgery and improving overall survival. Knowing the sensitivity profile of each patient to different treatment strategies at diagnosis may help choose the most appropriate ones. We develop a methodology for the quantitative estimation of the cytotoxic efficacy of cisplatin-based doublets on cancer cells by applying a simulation model of cancer progression and response. The model incorporates the proliferation cycle, quiescence, differentiation and loss of tumor cells. We evaluate the effect of in vivo microenvironment of real tumors, as expressed by measurable tumor proliferation kinetics, such as how fast the tumor grows, the percentage of cells that are actively dividing, the resistance of stem cells, etc. on treatment outcome so as to derive more accurate estimates. A literature survey guides the selection of values. The methodology is applied to a real clinical dataset of patients. Correlation studies between the derived cytotoxicities and the patients’ molecular profile could lead to predictions of treatment response at the time of diagnosis.

Phosphorylation Impacts N-end Rule Degradation of the Proteolytically Activated Form of BMX Kinase

Cellular signaling leading to the initiation of apoptosis typically results in the activation of caspases, which in turn leads to the proteolytic generation of protein fragments with new or altered cellular functions. Increasing numbers of reports are demonstrating that the activity of many of these proteolytically activated protein fragments can be attenuated by their selective degradation by the N-end rule pathway. Here we report the first evidence that selective degradation of a caspase product by the N-end rule pathway can be modulated by phosphorylation. We demonstrate that the pro-apoptotic fragment of the bone marrow kinase on chromosome X (BMX) generated by caspase cleavage in the prostate cancer-derived PC3 cell line is metabolically unstable in cells because its N-terminal tryptophan targets it for proteasomal degradation via the N-end rule pathway. In addition, we have demonstrated that phosphorylation of tyrosine 566 relatively inhibits degradation of the C-terminal BMX catalytic fragment, and this phosphorylation is crucial for its pro-apoptotic function. Overall, our results demonstrate that cleaved BMX is a novel N-end rule substrate, and its degradation exhibits a novel interplay between substrate phosphorylation and N-end rule degradation, revealing an increasing complex regulatory network of apoptotic proteolytic signaling cascades.

Nutrients, Microglia Aging, and Brain Aging

As the life expectancy continues to increase, the cognitive decline associated with Alzheimer's disease (AD) becomes a big major issue in the world. After cellular activation upon systemic inflammation, microglia, the resident immune cells in the brain, start to release proinflammatory mediators to trigger neuroinflammation. We have found that chronic systemic inflammatory challenges induce differential age-dependent microglial responses, which are in line with the impairment of learning and memory, even in middle-aged animals. We thus raise the concept of “microglia aging.” This concept is based on the fact that microglia are the key contributor to the acceleration of cognitive decline, which is the major sign of brain aging. On the other hand, inflammation induces oxidative stress and DNA damage, which leads to the overproduction of reactive oxygen species by the numerous types of cells, including macrophages and microglia. Oxidative stress-damaged cells successively produce larger amounts of inflammatory mediators to promote microglia aging. Nutrients are necessary for maintaining general health, including the health of brain. The intake of antioxidant nutrients reduces both systemic inflammation and neuroinflammation and thus reduces cognitive decline during aging. We herein review our microglia aging concept and discuss systemic inflammation and microglia aging. We propose that a nutritional approach to controlling microglia aging will open a new window for healthy brain aging.

iRGD-mediated reduction-responsive DSPE–PEG/LA–PLGA–TPGS mixed micelles used in the targeted delivery and triggered release of docetaxel in cancer

Reduction-sensitive micelles with crosslinked cores were developed to load the lipophilic chemotherapeutic drug docetaxel (DTX) in order to overcome the issues of toxicity, water insolubility, and rapid metabolism of DTX.

Docetaxel induces moderate ovarian toxicity in mice, primarily affecting granulosa cells of early growing follicles

Advances in cancer therapy have focused attention on the quality of life of cancer survivors. Since infertility is a major concern following chemotherapy, it is important to characterize the drug-specific damage to the reproductive system to help find appropriate protective strategies. This study investigates the damage on neonatal mouse ovary maintained in vitro for 6 days, and exposed for 24 h (on Day 2) to clinically relevant doses of Docetaxel (DOC; low: 0.1 µM, mid: 1 µM, high: 10 µM). Furthermore, the study explores the putative protective action exerted by Tri-iodothyronine (T3; 10⁻⁷ M). At the end of culture, morphological analyses and follicle counts showed that DOC negatively impacts on early growing follicles, decreasing primary follicle number and severely affecting health at the transitional and primary stages. Poor follicle health was mainly due to effects on granulosa cells, indicating that the effects of DOC on oocytes were likely to be secondary to granulosa cell damage. DOC damages growing follicles specifically, with no direct effect on the primordial follicle reserve. Immunostaining and western blotting showed that DOC induces activation of intrinsic, type II apoptosis in ovarian somatic cells; increasing the levels of cleaved caspase 3, cleaved caspase 8, Bax and cleaved poly(ADP-ribose) polymerase, while also inducing movement of cytochrome C from mitochondria into the cytosol. T3 did not prevent the damage induced by the low dose of DOC. These results demonstrated that DOC induces a gonadotoxic effect on the mouse ovary through induction of somatic cell apoptosis, with no evidence of direct effects on the oocyte, and that the damaging effect is not mitigated by T3.

Association of ABCB1, β tubulin I, and III with multidrug resistance of MCF7/DOC subline from breast cancer cell line MCF7

Docetaxel is a first-line chemotherapeutic agent for treating advanced breast cancer. The development of chemoresistance or multidrug resistance (MDR), however, results in breast cancer chemotherapy failure. This study aims to explore the molecular mechanisms underlying docetaxel-resistance in treatment of breast cancer. The docetaxel-resistant subline MCF7/DOC, derived from the parental sensitive breast cancer cell line MCF7, was established by intermittent exposure to moderate concentrations of docetaxel, followed by examination of its phenotypes. The MCF7/DOC subline showed cross resistance against paclitaxel, doxorubicin, methotrexate, and 5-Fu. Compared to the parental MCF7, MCF7/DOC cells were enlarged with heterogeneous sizes and a cobblestone and polygonal appearance. They were arrested at G2/M phase and proliferated slowly. The colony formation potential of MCF7/DOC in soft agar was significantly increased. MCF7/DOC cells showed reduced intracellular accumulation and increased efflux of rhodamine 123. The mRNA expression level of adenosine triphosphate binding cassette (ABC) transporter family, i.e., ABCB1, ABCC1, ABCC2, ABCG2, and β tubulin isotypes were characterized by quantitative PCR. High-level expression of ABCB1, βI, and βIII tubulin mRNA in MCF7/DOC was detected. Downregulation of ABCB1, βI, and βIII tubulin mediated by three combined siRNAs resulted in stronger growth inhibition of MCF7/DOC than inhibition of the expression of individual genes. ABCB1, βI, and βIII tubulin might contribute to the MDR of MCF7/DOC and be potential therapeutic targets for overcoming MDR of breast cancer.

A new model for mitochondrial membrane potential production and storage

Mitochondrial membrane potential (MMP) is the most reliable indicator of mitochondrial function. The MMP value range of -136 to -140mV has been considered optimal for maximum ATP production for all living organisms. Even small changes from the above range result in a large fall in ATP production and a large increase in ROS production. The resulting bioenergetic deregulation is considered as the causative agent for numerous major human diseases. Normalization of MMP value improves mitochondrial function and gives excellent therapeutic results. In order for a systematic effective treatment of these diseases to be developed, a detailed knowledge of the mechanism of MMP production is absolutely necessary. However, despite the long-standing research efforts, a concrete mechanism for MMP production has not been found yet. The present paper proposes a novel mechanism of MMP production based on new considerations underlying the function of the two basic players of MMP production, the electron transport chain (ETC) and the F1F0 ATP synthase. Under normal conditions, MMP is almost exclusively produced by the electron flow through ETC complexes I-IV, creating a direct electric current that stops in subunit II of complex IV and gradually charges MMP. However, upon ETC dysfunction F1F0 ATP synthase reverses its action and starts to hydrolyze ATP. ATP hydrolysis further produces electric energy which is transferred, in the form of a direct electric current, from F1 to F0 where is used to charge MMP. This new model is expected to redirect current experimental research on mitochondrial bioenergetics and indicate new therapeutic schemes for mitochondrial disorders.

Parenteral formulation of larotaxel lipid microsphere tackling poor solubility and chemical instability

The purpose of this study was to develop a parenteral larotaxel lipid microsphere (LTX-LM) and evaluate its stability. The preformulation study showed that LTX possessed poor solubility (0.057 μg/mL in aqueous phase) and chemical instability. LM was selected as the drug carrier due to its higher drug-loading capacities, higher physicochemical stability and reduced irritation and toxicity. High speed shear mixing and high-pressure homogenization were employed to prepare the LTX-LM. Particle size distribution (PSD), zeta-potential, drug content and entrapment efficiency (EE) were taken as indexes to optimize formulations. The dissolution studies were performed using a ZRS-8G dissolution apparatus according to the paddle method. Degradation kinetics test, freezing and thawing test and long term stability test were combined to evaluate the physicochemical stability of LTX-LM. From the degradation kinetics results, the shelf lives (T90%) of LTX in LM at 25 and 4°C (165, 555 days) were about 20 times as long as those in aqueous phase (200, 676 h), which were dramatically prolonged. The activation energies in aqueous solution and in LM calculated from the slopes were 41.93 and 42.25 kJ/mol. And its frequency factors (A) were 4.9 × 10(3)/s and 2.3 × 10(2)/s, respectively. Freezing and thawing test showed the PSD of LTX-LM became larger and wider increasing from 166.9 ± 53.2 nm to 257.4 ± 85.5 nm with more freeze-thaw cycles. From the long term stability test results, all the parameters changes were in qualified range.

Combination effects of docetaxel and Doxorubicin in hormone-refractory prostate cancer cells

Combination effects of docetaxel (DOC) and doxorubicin (DOX) were investigated in prostate cancer cells (PC3 and DU145). Combination indices (CIs) were determined using the unified theory in various concentrations and mixing ratios (synergy: CI < 0.9, additivity: 0.9 < CI < 1.1, and antagonism: CI > 1.1). DOC showed a biphasic cytotoxicity pattern with the half maximal inhibitory concentration (IC50) at the picomolar range for PC3 (0.598 nM) and DU145 (0.469 nM), following 72 h drug exposure. The IC50s of DOX were 908 nM and 343 nM for PC3 and DU145, respectively. Strong synergy was seen when PC3 was treated with DOC at concentrations lower than its IC50 values (0.125~0.5 nM) plus DOX (2~8 times IC50). Equipotent drug combination treatments (7 × 7) revealed that the DOC/DOX combination leads to high synergy and effective cell death only in a narrow concentration range in DU145. This study provides a convenient method to predict multiple drug combination effects by the estimated CI values as well as cell viability data. The proposed DOC/DOX mixing ratios can be used to design combination drug cocktails or delivery systems to improve chemotherapy for cancer patients.

Novel hydrophilic docetaxel (CQMU-0519) analogue inhibits proliferation and induces apoptosis in human A549 lung, SKVO3 ovarian and MCF7 breast carcinoma cell lines

OBJECTIVE

Objectives of this investigation were not merely to perform a comparative study with original docetaxel, but to define anti-proliferative and apoptotic effects of novel hydrophilic docetaxel (CQMU-0519) analogue on A549 lung, SKVO3 ovary and MCF7 breast carcinoma cell lines.

MATERIALS AND METHODS

The materials for the study consist of a completely new docetaxel analogue (CQMU-0519), synthesized by the Department of Pharmacology, Chongqing Medical University, China, which is completely soluble in water. 50 nm of drug concentration was utilized on all three cell lines where cell population growth was assessed using cell culture kit-8 and flow cytometry analysis, whereas apoptotic pathways were unveiled by use of annexin-V FITC, apoptosis DNA ladder, caspases-3, 6, 8 and 9; in the meanwhile, regulation of Bcl-2 family members was analysed by western blotting.

RESULT

The novel docetaxel analogue (CQMU-0519) suppressed cell proliferation in all three cell lines, inhibition of cell proliferation and cell cycle arrest being more evident in G(2) /M phase. Also, in both lung and ovarian cell lines, apoptotic levels were higher as measured by the various tests performed, and downregulation of Bcl-2 and Bcl-xL with increased expressions of Bad and Bax indicated the intrinsic pathway for apoptosis. Nevertheless, it was found that MCF7 cells, although also manifesting high levels of apoptosis, used the extrinsic pathway instead. Hence, it was shown that novel docetaxel analogue (CQMU-0519) may have some prospective use in future clinical trials.

CONCLUSIONS

Novel hydrophilic docetaxel analogue (CQMU-0519) inhibited cell proliferation and enhanced the intrinsic apoptotic pathway in lung and ovarian carcinoma cells, whereas it used the extrinsic one in breast adenocarcinoma cells.

Taxane resistance in breast cancer: mechanisms, predictive biomarkers and circumvention strategies

BACKGROUND

Taxanes are established in the treatment of metastatic breast cancer (MBC) and early breast cancer (EBC) as potent chemotherapy agents. However, their therapeutic usefulness is limited by de-novo refractoriness or acquired resistance, which are common drawbacks to most anti-cancer cytotoxics. Considering that the taxanes will remain principle chemotherapeutic agents for the treatment of breast cancer, we reviewed known mechanisms of resistance in with an outlook of optimizing their clinical use.

METHODS

We searched the PubMed and MEDLINE databases for articles (from inception through to 9th January 2012; last search 10/01/2012) and journals known to publish information relevant to taxane chemotherapy. We imposed no language restrictions. Search terms included: cancer, breast cancer, response, resistance, taxane, paclitaxel, docetaxel, taxol. Due to the possibility of alternative mechanisms of resistance all combination chemotherapy treated data sets were removed from our overview.

RESULTS

Over-expression of the MDR-1 gene product Pgp was extensively studied in vitro in association with taxane resistance, but data are conflicting. Similarly, the target components microtubules, which are thought to mediate refractoriness through alterations of the expression pattern of tubulins or microtubule associated proteins and the expression of alternative tubulin isoforms, failed to confirm such associations. Little consensus has been generated for reported associations between taxane-sensitivity and mutated p53, or taxane-resistance and overexpression of Bcl-2, Bcl-xL or NFkB. In contrary sufficient in vitro data support an association of spindle assembly checkpoint (SAC) defects with resistance. Clinical data have been limited and inconsistent, which relate to the variety of methods used, lack of standardization of cut-offs for quantitation, differences in clinical endpoints measured and in methods of tissue collection preparation and storage, and study/patient heterogeneity. The most prominent finding is that pharmaceutical down-regulation of HER-2 appears to reverse the taxane resistance.

CONCLUSIONS

Currently no valid practical biomarkers exist that can predict resistance to the taxanes in breast cancer supporting the principle of individualized cancer therapy. The incorporation of several biomarker analyses into prospectively designed studies in this setting are needed.

The association of statins and taxanes: an efficient combination trigger of cancer cell apoptosis

Background:

Cancer cell killing might be achieved by the combined use of available drugs. Statins are major anti-hypercholesterolemia drugs, which also trigger apoptosis of many cancer cell types, while docetaxel is a potent microtubule-stabilising agent.

Methods:

Here, we looked at the combined effects of lovastatin and docetaxel in cancer cells.

Results:

Whole transcriptome microarrays in HGT-1 gastric cancer cells demonstrated that lovastatin strongly suppressed expression of genes involved in cell division, while docetaxel had very little transcriptional effects. Both drugs triggered apoptosis, and their combination was more than additive. A marked rise in the cell-cycle inhibitor p21, together with reduction of aurora kinases A and B, cyclins B1 and D1 proteins was induced by lovastatin alone or in combination with docetaxel. The drug treatments induced the proteolytic cleavage of procaspase-3, a drop of the anti-apoptotic Mcl-1 protein, Poly-ADP-Ribose Polymerase and Bax. Strikingly, docetaxel-resistant HGT-1 cell derivatives overexpressing the MDR-1 gene were much more sensitive to lovastatin than docetaxel-sensitive cells.

Conclusion:

These results suggest that the association of lovastatin and docetaxel, or lovastatin alone, shows promise as plausible anticancer strategies, either as a direct therapeutic approach or following acquired P-glycoprotein-dependent resistance.

Developing a powerful in silico tool for the discovery of novel caspase-3 substrates: a preliminary screening of the human proteome

Background

Caspases are a family of cysteinyl proteases that regulate apoptosis and other biological processes. Caspase-3 is considered the central executioner member of this family with a wide range of substrates. Identification of caspase-3 cellular targets is crucial to gain further insights into the cellular mechanisms that have been implicated in various diseases including: cancer, neurodegenerative, and immunodeficiency diseases. To date, over 200 caspase-3 substrates have been identified experimentally. However, many are still awaiting discovery.

Results

Here, we describe a powerful bioinformatics tool that can predict the presence of caspase-3 cleavage sites in a given protein sequence using a Position-Specific Scoring Matrix (PSSM) approach. The present tool, which we call CAT3, was built using 227 confirmed caspase-3 substrates that were carefully extracted from the literature. Assessing prediction accuracy using 10 fold cross validation, our method shows AUC (area under the ROC curve) of 0.94, sensitivity of 88.83%, and specificity of 89.50%. The ability of CAT3 in predicting the precise cleavage site was demonstrated in comparison to existing state-of-the-art tools. In contrast to other tools which were trained on cleavage sites of various caspases as well as other similar proteases, CAT3 showed a significant decrease in the false positive rate. This cost effective and powerful feature makes CAT3 an ideal tool for high-throughput screening to identify novel caspase-3 substrates.

The developed tool, CAT3, was used to screen 13,066 human proteins with assigned gene ontology terms. The analyses revealed the presence of many potential caspase-3 substrates that are not yet described. The majority of these proteins are involved in signal transduction, regulation of cell adhesion, cytoskeleton organization, integrity of the nucleus, and development of nerve cells.

Conclusions

CAT3 is a powerful tool that is a clear improvement over existing similar tools, especially in reducing the false positive rate. Human proteome screening, using CAT3, indicate the presence of a large number of possible caspase-3 substrates that exceed the anticipated figure. In addition to their involvement in various expected functions such as cytoskeleton organization, nuclear integrity and adhesion, a large number of the predicted substrates are remarkably associated with the development of nerve tissues.

[18F]-3'Deoxy-3'-fluorothymidine positron emission tomography and breast cancer response to docetaxel

PURPOSE

To establish biomarkers indicating clinical response to taxanes, we determined whether early changes in [(18)F]-3'deoxy-3'-fluorothymidine positron emission tomography (FLT-PET) can predict benefit from docetaxel therapy in breast cancer.

EXPERIMENTAL DESIGN

This was a prospective unblinded study in 20 patients with American Joint Committee on Cancer (AJCC) stage II-IV breast cancer unresponsive to first-line chemotherapy or progressing on previous therapy. Individuals underwent a baseline dynamic FLT-PET scan followed by a scan 2 weeks after initiating the first or second cycle of docetaxel. PET variables were compared with anatomic response midtherapy (after 3 cycles).

RESULTS

Average and maximum tumor standardized uptake values at 60 minutes (SUV(60,av) and SUV(60,max)) normalized to body surface area ranged between 1.7 and 17.0 and 5.6 and 26.9 × 10(-5) m(2)/mL, respectively. Docetaxel treatment resulted in a significant decrease in FLT uptake (P = 0.0003 for SUV(60,av) and P = 0.0002 for SUV(60,max)). Reduction in tumor SUV(60,av) was associated with target lesion size changes midtherapy (Pearson R for SUV(60,av) = 0.64; P = 0.004) and predicted midtherapy target lesion response (0.85 sensitivity and 0.80 specificity). Decreases in SUV(60,av) in responders were due, at least in part, to reduced net intracellular trapping of FLT (rate constant, K(i)). Docetaxel significantly reduced K(i) by 51.1% (±28.4%, P = 0.0009).

CONCLUSION

Changes in tumor proliferation assessed by FLT-PET early after initiating docetaxel chemotherapy can predict lesion response midtherapy with good sensitivity warranting prospective trials to assess the ability to stop therapy in the event of non-FLT-PET response.

Purine Nucleoside Phosphorylase mediated molecular chemotherapy and conventional chemotherapy: a tangible union against chemoresistant cancer

BACKGROUND

Late stage Ovarian Cancer is essentially incurable primarily due to late diagnosis and its inherent heterogeneity. Single agent treatments are inadequate and generally lead to severe side effects at therapeutic doses. It is crucial to develop clinically relevant novel combination regimens involving synergistic modalities that target a wider repertoire of cells and lead to lowered individual doses. Stemming from this premise, this is the first report of two- and three-way synergies between Adenovirus-mediated Purine Nucleoside Phosphorylase based gene directed enzyme prodrug therapy (PNP-GDEPT), docetaxel and/or carboplatin in multidrug-resistant ovarian cancer cells.

METHODS

The effects of PNP-GDEPT on different cellular processes were determined using Shotgun Proteomics analyses. The in vitro cell growth inhibition in differentially treated drug resistant human ovarian cancer cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The involvement of apoptosis and implicated proteins in effects of different treatments was established using flow cytometry based detection of M30 (an early marker of apoptosis), cell cycle analyses and finally western blot based analyses.

RESULTS

Efficacy of the trimodal treatment was significantly greater than that achieved with bimodal- or individual treatments with potential for 10-50 fold dose reduction compared to that required for individual treatments. Of note was the marked enhancement in apoptosis that specifically accompanied the combinations that included PNP-GDEPT and accordingly correlated with a shift in the expression of anti- and pro-apoptotic proteins. PNP-GDEPT mediated enhancement of apoptosis was reinforced by cell cycle analyses. Proteomic analyses of PNP-GDEPT treated cells indicated a dowregulation of proteins involved in oncogenesis or cancer drug resistance in treated cells with accompanying upregulation of apoptotic- and tumour- suppressor proteins.

CONCLUSION

Inclusion of PNP-GDEPT in regular chemotherapy regimens can lead to significant enhancement of the cancer cell susceptibility to the combined treatment. Overall, these data will underpin the development of regimens that can benefit patients with late stage ovarian cancer leading to significantly improved efficacy and increased quality of life.

Interaction of poly(ethylenimine)-DNA polyplexes with mitochondria: implications for a mechanism of cytotoxicity

Poly(ethylenimine) (PEI) and PEI-based systems have been widely studied for use as nucleic acid delivery vehicles. However, many of these vehicles display high cytotoxicity, rendering them unfit for therapeutic use. By exploring the mechanisms that cause cytotoxicity, and through understanding structure-function relationships between polymers and intracellular interactions, nucleic acid delivery vehicles with precise intracellular properties can be tailored for specific function. Previous research has shown that PEI is able to depolarize mitochondria, but the exact mechanism as to how depolarization is induced remains elusive and therefore is the focus of the current study. Potential mechanisms for mitochondrial depolarization include direct mitochondrial membrane permeabilization by PEI or PEI polyplexes, activation of the mitochondrial permeability transition pore, and interference with mitochondrial membrane proton pumps, specifically Complex I of the electron transport chain and F(0)F(1)-ATPase. Herein, confocal microscopy and live cell imaging showed that PEI polyplexes do colocalize to some degree with mitochondria early in transfection, and the degree of colocalization increases over time. Cyclosporin a was used to prevent activation of the mitochondrial membrane permeability transition pore, and it was found that early in transfection cyclosporin a was unable to prevent the loss of mitochondrial membrane potential. Further studies done using rotenone and oligomycin to inhibit Complex I of the electron transport chain and F(0)F(1)-ATPase, respectively, indicate that both of these mitochondrial proton pumps are functioning during PEI transfection. Overall, we conclude that direct interaction between polyplexes and mitochondria may be the reason why mitochondrial function is impaired during PEI transfection.

Activation of B cell apoptotic pathways in the course of Francisella tularensis infection

Francisella tularensis is a facultative intracellular, gram-negative bacterium that induces apoptosis in macrophages and B cells. Here we show apoptotic pathways that are activated in the Ramos human B cell line in the course of F. tularensis infection. Live bacteria F. tularensis FSC200 activate caspases 8, 9 and 3, as well as Bid; release cytochrome c and apoptosis-inducing factor from mitochondria; and induce depolarization of mitochondrial membrane potential in the Ramos cell line, thus leading these cells to apoptosis. Unlike live bacteria, killed F. tularensis FSC200 bacteria activated only caspase 3, and did not cause apoptosis of Ramos cells as measured by annexin V. Killed bacteria also caused accumulation of anti-apoptotic protein Bclx(L) in mitochondrial membranes. Thus, live F. tularensis activates both caspase pathways (receptor-mediated and intrinsic) as well as caspase-independent mitochondrial death.

Docetaxel-ST1481 sequence exerts a potent cytotoxic activity on hormone-resistant prostate cancer cells by reducing drug resistance-related gene expression

BACKGROUND

The efficacy of current therapy for hormone-refractory prostate cancer is still unsatisfactory and new agents and therapeutic modalities are needed. The aims of the present work were to examine the in vitro activity and mechanisms of action of different antitumor drug combinations in hormone-resistant prostate cancer (HRPC) cell lines.

METHODS

The activity of docetaxel (Doc), cisplatin (Cis), oxaliplatin (Oxa), SN-38 and ST1481, singly or in combination, was assessed in different HRPC cell lines (PC3, parental DU145 and taxane-resistant DU145-R) by SRB test. Apoptosis was evaluated by TUNEL and ANN-V assays. Extrusion pump activity was studied by Hoechst 33342 assay, while gene expression related to drug efflux mechanisms and DNA damage repair was analyzed by RT-PCR.

RESULTS

Doc induced a high cytocidal effect in the HRPC cells, whereas Cis, Oxa, SN-38 and ST1481 exerted prevalently cytostatic activity. Doc followed by ST1481 proved to be the most effective drug sequence among those investigated, producing an important synergistic effect (R.I. from 2.0 to 5.2) in all the tested cell lines. Moreover, this sequence induced a significant downregulation of xenobiotic extrusion pump and DNA damage repair gene expression. ST1481 synergistically increased the cytocidal effect of Doc, probably through a downregulation of extrusion pump activity and DNA damage repair-related genes.

CONCLUSIONS

Our results show that the Doc --> ST1481 sequence effectively reduces the cancer cell population and restores Doc activity in taxane-resistant HRPC, indicating its potential usefulness as first- or second-line treatment of hormone-refractory prostate cancer.

Docetaxel-induced prostate cancer cell death involves concomitant activation of caspase and lysosomal pathways and is attenuated by LEDGF/p75

Background

Hormone-refractory prostate cancer (HRPC) is characterized by poor response to chemotherapy and high mortality, particularly among African American men when compared to other racial/ethnic groups. It is generally accepted that docetaxel, the standard of care for chemotherapy of HRPC, primarily exerts tumor cell death by inducing mitotic catastrophe and caspase-dependent apoptosis following inhibition of microtubule depolymerization. However, there is a gap in our knowledge of mechanistic events underlying docetaxel-induced caspase-independent cell death, and the genes that antagonize this process. This knowledge is important for circumventing HRPC chemoresistance and reducing disparities in prostate cancer mortality.

Results

We investigated mechanistic events associated with docetaxel-induced death in HRPC cell lines using various approaches that distinguish caspase-dependent from caspase-independent cell death. Docetaxel induced both mitotic catastrophe and caspase-dependent apoptosis at various concentrations. However, caspase activity was not essential for docetaxel-induced cytotoxicity since cell death associated with lysosomal membrane permeabilization still occurred in the presence of caspase inhibitors. Partial inhibition of docetaxel-induced cytotoxicity was observed after inhibition of cathepsin B, but not inhibition of cathepsins D and L, suggesting that docetaxel induces caspase-independent, lysosomal cell death. Simultaneous inhibition of caspases and cathepsin B dramatically reduced docetaxel-induced cell death. Ectopic expression of lens epithelium-derived growth factor p75 (LEDGF/p75), a stress survival autoantigen and transcription co-activator, attenuated docetaxel-induced lysosomal destabilization and cell death. Interestingly, LEDGF/p75 overexpression did not protect cells against DTX-induced mitotic catastrophe, and against apoptosis induced by tumor necrosis factor related apoptosis inducing ligand (TRAIL), suggesting selectivity in its pro-survival activity.

Conclusion

These results underscore the ability of docetaxel to induce concomitantly caspase-dependent and independent death pathways in prostate cancer cells. The results also point to LEDGF/p75 as a potential contributor to cellular resistance to docetaxel-induced lysosomal destabilization and cell death, and an attractive candidate for molecular targeting in HRPC.

Phase I study of larotaxel administered as a 1-h intravenous infusion every 3 weeks to Japanese patients with advanced solid tumours

Larotaxel (XRP9881, RPR109881), a novel semi-synthetic taxoid that shares a mode of action with the taxanes docetaxel and paclitaxel, was active in preclinical studies against a broad spectrum of tumour cells and tumour models refractory/resistant to taxanes, and have demonstrated clinical activity in taxane pre-treated/resistant metastatic breast cancer (MBC) patients. The current phase I dose-escalation study sought to define in Japanese patients with advanced solid tumours the maximum tolerated dose (MTD) and recommended dose (RD) of larotaxel administered as a 1-h intravenous infusion every 3 weeks. Eighteen patients were treated in total with 11 of those (61%) having previously received a docetaxel- or paclitaxel-based regimen. The MTD was defined as 90 mg/m(2) following the occurrence of dose-limiting toxicities (DLTs) in two of five patients treated at this dose level including grade 4 neutropenia lasting >7 days or febrile neutropenia. The RD for phase II was consequently 75 mg/m(2) q3w, with no DLTs in the six patients treated. The principal toxicity and DLT was neutropenia, with or without neutropenic complications. Partial responses were reported for 2 of 18 (11%) treated patients and a further 8 achieved stable disease (44%). The clearance 19.1-31.9 L/h was similar to that observed in Caucasian subjects with value of 33.0 +/- 10.7 L/h. In conclusion, larotaxel 75 mg/m(2), administered as a 1-h infusion every 3 weeks, appeared to be clinically tolerable in this Japanese patient population and showed early indications of activity.

Zoledronic acid increases docetaxel cytotoxicity through pMEK and Mcl-1 inhibition in a hormone-sensitive prostate carcinoma cell line

Background

In prostate cancer, the identification of drug combinations that could reduce the tumor cell population and rapidly eradicate hormone-resistant cells potentially present would be a remarkable breakthrough in the treatment of this disease.

Methods

The study was performed on a hormone-sensitive prostate cancer cell line (LNCaP) grown in normal or hormone-deprived charcoal-stripped (c.s.) medium. Cell viability and apoptosis were assessed by SRB assay and Annexin-V/TUNEL assays, respectively. Activated caspase-3, p21, pMEK and MCL-1 expression levels were detected by western blotting.

Results

The simultaneous exposure of zoledronic acid [100 μM] and docetaxel [0.01 μM] for 1 h followed by treatment with zoledronic acid for 72, 96 or 120 h produced a high synergistic interaction (R index = 5.1) with a strong decrease in cell viability. This cytotoxic effect was associated with a high induction of apoptosis in both LNCaP and in c.s. LNCaP cells. The induction of apoptosis was paralleled by a decrease in pMEK and Mcl-1 expression.

Conclusion

The zoledronic acid-docetaxel combination produced a highly significant synergistic effect on the LNCaP cell line grown in normal or hormone-deprived medium, the principal molecular mechanisms involved being apoptosis and decreased pMEK and Mcl-1 expression. This experimentally derived schedule would seem to prevent the selection and amplification of hormone-resistant cell clones and could thus be potentially used alongside standard androgen deprivation therapy in the management of hormone-sensitive prostate carcinoma.

Anti-tumor effect of Coriolus versicolor methanol extract against mouse B16 melanoma cells: in vitro and in vivo study

Numerous studies have shown immunostimulatory and anti-tumor effects of water and standardized aqueous ethanol extracts derived from the medicinal mushroom, Coriolus versicolor, but the biological activity of methanol extracts has not been examined so far. In the present study we investigated the anti-tumor effect of C. versicolor methanol extract (which contains terpenoids and polyphenols) on B16 mouse melanoma cells both in vitro and in vivo. In vitro treatment of the cells with the methanol extract (25-1600 microg/ml) reduced melanoma cell viability in a dose-dependent manner. Furthermore, in the presence of the methanol extract (200 microg/ml, concentration IC(50)) the proliferation of B16 cells was arrested in the G(0)/G(1) phase of the cell cycle, followed by both apoptotic and secondary necrotic cell death. In vivo methanol extract treatment (i.p. 50 mg/kg, for 14 days) inhibited tumor growth in C57BL/6 mice inoculated with syngeneic B16 tumor cells. Moreover, peritoneal macrophages collected 21 days after tumor implantation from methanol extract-treated animals exerted stronger tumoristatic activity ex vivo than macrophages from control melanoma-bearing mice. Taken together, our results demonstrate that C. versicolor methanol extract exerts pronounced anti-melanoma activity, both directly through antiproliferative and cytotoxic effects on tumor cells and indirectly through promotion of macrophage anti-tumor activity.