Mode of action of docetaxel - a basis for combination with novel anticancer agents

Cancer immunotherapy via combining oncolytic virotherapy with chemotherapy: recent advances

Oncolytic viruses are multifunctional anticancer agents with huge clinical potential, and have recently passed the randomized Phase III clinical trial hurdle. Both wild-type and engineered viruses have been selected for targeting of specific cancers, to elicit cytotoxicity, and also to generate antitumor immunity. Single-agent oncolytic virotherapy treatments have resulted in modest effects in the clinic. There is increasing interest in their combination with cytotoxic agents, radiotherapy and immune-checkpoint inhibitors. Similarly to oncolytic viruses, the benefits of chemotherapeutic agents may be that they induce systemic antitumor immunity through the induction of immunogenic cell death of cancer cells. Combining these two treatment modalities has to date resulted in significant potential in vitro and in vivo synergies through various mechanisms without any apparent additional toxicities. Chemotherapy has been and will continue to be integral to the management of advanced cancers. This review therefore focuses on the potential for a number of common cytotoxic agents to be combined with clinically relevant oncolytic viruses. In many cases, this combined approach has already advanced to the clinical trial arena.

Apoptosis Markers in Breast Cancer Therapy

Cancer is a disease characterized by a very little apoptosis, ie, genetically programmed cell death. Aberrations in apoptotic pathways are central to tumorigenesis, tumor progression, and overall tumor growth and regression in response to chemotherapy. It is now increasingly accepted that chemotherapeutic drug efficacy is partially related to its ability to induce apoptosis. Apoptosis, therefore, represents not only a vital target in cancer therapy but also a unique biomarker opportunity that has thus far been largely unexploited. In response to therapy, tumor cells undergo apoptosis and release their cellular components in the circulation. As such, these materials may serve as biomarkers to assess response. Apoptosis markers in breast cancer include circulating soluble FasL, granzyme B, and cytochrome c that increase following chemotherapy. Unfortunately, there is a paucity of information in the literature with respect to this approach. As such, large-scale prospective studies are clearly needed to validate this approach and more fully elucidate clinical usefulness.

Treatment options in non-muscle-invasive bladder cancer after BCG failure

Bladder cancer is the ninth-most prevalent cancer worldwide. Most patients with urothelial cell carcinoma of the bladder present with non-muscle-invasive disease and are treated with bacillus Calmette-Guérin (BCG) intravesical therapy. Many of these patients experience disease recurrence after BCG failure. Radical cystectomy is the recommended treatment for high-risk patients failing BCG. However, many patients are unfit for or unwilling to undergo this procedure. We searched the published literature on the treatment of non-muscle-invasive bladder cancer (NMIBC) after BCG failure. We review current evidence regarding intravesical therapy with gemcitabine, mitomycin combined with thermo-chemotherapy, docetaxel, nab-paclitaxel, photodynamic therapy (PDT), BCG with interferon (IFN), and combination sequentially administered chemotherapy.

C60-fullerenes for delivery of docetaxel to breast cancer cells: A promising approach for enhanced efficacy and better pharmacokinetic profile

Docetaxel has always attracted the researchers owing to its promises and challenges. Despite marked efficacy, concerns like poor aqueous solubility, lower bioavailability, poor tissue penetration and dose related side-effects offer further scope of research on docetaxel. The present study aims to explore the potential of C60-fullerenes in the delivery of docetaxel to cancerous cells. C60-fullerenes were carboxylated, acylated and conjugated with the drug. The chemical processes were monitored by UV, FT-IR and NMR spectroscopy. The conjugate was further characterized for drug loading, micromeritics, drug release, morphology and evaluated for in-vitro cytotoxicity, haemolysis and in-vivo pharmacokinetic profile. The developed nanoconstruct was able to enhance the bioavailability of docetaxel by 4.2 times and decrease the drug clearance by 50%. The developed system was able to control the drug release and was found to be compatible with erythrocytes. The cytotoxic potential on studied MCF-7 and MDA-MB231 cell lines was also enhanced by many folds, indicating marked promise in efficacy enhancement and dose reduction. The present findings are encouraging and offer a technique to enhance the delivery and efficacy potential of anticancer agents, especially belonging to BCS class IV.

Regulation of BAX/BCL2 gene expression in breast cancer cells by docetaxel-loaded human serum albumin nanoparticles

Today, using nanoparticle-based drug delivery systems has expanded to avoid anticancer side effects. Taxanes are important chemotherapeutic agents in the treatment of metastatic breast cancer. In this study, docetaxel (DTX)-loaded human serum albumin (HSA) nanoparticles (NPs) were prepared and characterized. Drug toxicity of the nanoparticles was measured by MTT assay with different drug concentrations (0.01, 0.1, 0.5, 1 and 5 μM) at different incubation times (24, 48 and 72 h). Expression of BAX/BCL2 mRNA levels was determined by real-time PCR. The size of NPs prepared and used in our study was about 147 nm with surface charge of -29.6 mV. Results obtained from MTT assay showed that 0.5 μM of free drug had 50 % toxicity on MCF-7 cells after 48-h incubation. Real-time PCR results showed an increase in expression of BAX and no change for BCL2. In conclusion, a significant overexpression of BAX gene and changes in BAX/BCL2 ratio were observed for DTX-loaded HSA nanoparticles compared with free DTX and may provide a potential therapy to inhibit anticancer drug resistance.

How Taxol/paclitaxel kills cancer cells

Taxol (generic name paclitaxel) is a microtubule-stabilizing drug that is approved by the Food and Drug Administration for the treatment of ovarian, breast, and lung cancer, as well as Kaposi's sarcoma. It is used off-label to treat gastroesophageal, endometrial, cervical, prostate, and head and neck cancers, in addition to sarcoma, lymphoma, and leukemia. Paclitaxel has long been recognized to induce mitotic arrest, which leads to cell death in a subset of the arrested population. However, recent evidence demonstrates that intratumoral concentrations of paclitaxel are too low to cause mitotic arrest and result in multipolar divisions instead. It is hoped that this insight can now be used to develop a biomarker to identify the ∼50% of patients that will benefit from paclitaxel therapy. Here I discuss the history of paclitaxel and our recently evolved understanding of its mechanism of action.

Antiandrogens Inhibit ABCB1 Efflux and ATPase Activity and Reverse Docetaxel Resistance in Advanced Prostate Cancer

PURPOSE

Previous studies show that inhibition of ABCB1 expression overcomes acquired docetaxel resistance in C4-2B-TaxR cells. In this study, we examined whether antiandrogens, such as bicalutamide and enzalutamide, could inhibit ABCB1 activity and overcome resistance to docetaxel.

EXPERIMENTAL DESIGN

ABCB1 efflux activity was determined using a rhodamine efflux assay. ABCB1 ATPase activity was determined by Pgp-Glo assay systems. The effects of the antiandrogens bicalutamide and enzalutamide on docetaxel sensitivity were determined by cell growth assays and tumor growth in vivo.

RESULTS

We found that bicalutamide and enzalutamide inhibit ABCB1 ATP-binding cassette transporter activity through blocking ABCB1 efflux activity. Bicalutamide inhibited ABCB1 efflux activity by 40%, whereas enzalutamide inhibited ABCB1 efflux activity by approximately 60%. Both bicalutamide and enzalutamide inhibit ABCB1 ATPase activity. In addition, bicalutamide and enzalutamide inhibit ABCB1 efflux activity and desensitize docetaxel-resistant and androgen receptor (AR)-negative DU145 cells. Combination of bicalutamide with docetaxel had a significant antitumor effect in both AR-positive and AR-negative docetaxel-resistant xenograft models, suggesting that bicalutamide desensitizes docetaxel-resistant cells to docetaxel treatment independent of AR status.

CONCLUSIONS

We identified a novel mechanism of action for antiandrogens such as bicalutamide and enzalutamide as inhibitors of ABCB1 efflux and ATPase activity. Bicalutamide and enzalutamide desensitize docetaxel-resistant prostate cancer cells to docetaxel treatment independent of AR status. These studies may lead to the development of combinational therapies with bicalutamide/enzalutamide and docetaxel as effective regimens to treat advanced prostate cancer independent of AR status, and possibly other types of cancer.

Paclitaxel and etoposide co-loaded polymeric nanoparticles for the effective combination therapy against human osteosarcoma

BACKGROUND

The combination of chemotherapeutic drugs with different pharmacological action has emerged as a promising therapeutic strategy in the treatment of cancers. Present study examines the antitumor potential of paclitaxel (PTX) and etoposide (ETP)-loaded PLGA nanoparticles for the treatment of osteosarcoma.

RESULTS

The resulting drug-loaded PLGA NP exhibited a nanosize dimension with uniform spherical morphology. The NP exhibited a sustained release profile for both PTX and ETP throughout the study period without any sign of initial burst release. The combinational drug-loaded PLGA NP enhanced the cytotoxic effect in MG63 and Saos-2 osteosarcoma cell lines, in comparison to either native drug alone or in cocktail combinations. Additionally, NPs showed an appreciable uptake in MG63 cells in a time-based manner. Co-delivery of anticancer drugs resulted in enhanced cell cycle arrest and cell apoptosis. The results clearly showed that combinational drugs remarkably improved the therapeutic index of chemotherapeutic drugs. The greater inhibitory effect of nanoparticle combination would be of great advantage during systemic cancer therapy.

CONCLUSION

Taken together, our study demonstrated that PTX-ETP/PLGA NP based combination therapy holds significant potential towards the treatment of osteosarcoma.

Paradoxical effects of the autophagy inhibitor 3-methyladenine on docetaxel-induced toxicity in PC-3 and LNCaP prostate cancer cells

Docetaxel was the first chemotherapeutic agent to increase survival time in patients with androgen-resistant prostate cancer. However, it provides only a modest increase in survival and is associated with significant toxicity. Therefore, there is an urgent need to identify potential adjunct therapies. Given the key role of autophagy in both tumour survival and chemoresistance, the impact of autophagy modulation on docetaxel toxicity was tested in vitro. PC-3 and LNCaP cells were pre-treated with the autophagy inhibitor 3-methyladenine (5 mM) and then exposed to various concentrations (0-100 μM) of docetaxel. Cytoxic effects of docetaxel were measured using resazurin reduction to resorufin, whilst autophagy and apoptosis was measured using monodansylcadaverine, annexin V and caspase-3, respectively. Docetaxel produced significant toxicity in PC-3 cells but was not toxic to LNCaP cells. Pre-treatment with the autophagy inhibitor, 3-methyladenine (5 mM) significantly protected PC-3 cells against docetaxel-induced cytotoxicity, increased autophagosome formation and apoptosis measured using monodansylcadaverine, annexin V and caspase-3 fluorescence, respectively. In contrast, 3-methyladenine was toxic by itself in LNCaP cells and also increased autophagic vesicle formation and apoptosis but did not influence docetaxel toxicity in these cells. These paradoxical effects of 3-methyladenine were largely independent of reactive oxygen species production. We show here that modulation of autophagy may influence docetaxel-induced toxicity in prostate cancer cells and these effects may differ between cell lines.

Innovative use of the taxol binding peptide overcomes key challenges of stable and high drug loading in polymeric nanomicelles

Incorporating a taxol binding peptide into the hydrophobic backbone of polymeric nanomicelles enhances docetaxel loading while maintaining serum stability.

Down-modulation of Bcl-2 sensitizes PTEN-mutated prostate cancer cells to starvation and taxanes

BACKGROUND

The critical role of PTEN in regulating the PI3K/Akt/mTOR signaling pathway raises the possibility that targeting downstream effectors of the PI3K pathway, such as Bcl-2, might be an effective anti-proliferative strategy for PTEN-deficient prostate cancer cells.

METHODS

Four prostate cancer cell lines (LNCaP, PC3, DU145, 22Rv1) were assayed for their levels of total Akt and Ser473 phosphorylated Akt (p-Akt) by Western Blotting; their growth rates and sensitivity to different doses of paclitaxel were determined by cell counts after Trypan Blue dye exclusion assay. Cells were subjected to different combinations of starvation (growth factors and/or aminoacids withdrawal), paclitaxel treatment and Bcl-2 silencing by siRNA. Cell viability was evaluated by Trypan Blue dye exclusion assay, Propidium Iodide (PI) and Annexin-V/PI staining.

RESULTS

We assessed the sensitivity of different prostate cancer cell lines to starvation and we observed a differential response correlated to the levels of Akt activation. The four prostate cancer cell lines also showed different sensitivity to taxol treatments; LNCaP and 22Rv1 cells were more resistant to paclitaxel than DU145 and PC3 cells. Combining taxol with growth factors and aminoacids deprivation leaded to a more than additive reduction of cell viability compared to single treatments in PTEN-mutant LNCaP cells. Down-modulation of anti-apoptotic Bcl-2 protein by siRNA sensitized LNCaP cells to taxanes and starvation induced cell death.

CONCLUSIONS

Silencing Bcl-2 in PTEN-mutated prostate cancer cells enhances the apoptotic effects of combined starvation and taxol treatments, indicating that inhibition of Bcl-2 may be of significant value in PTEN-mutant tumor therapy.

Solid lipid nanoparticle formulations of docetaxel prepared with high melting point triglycerides: in vitro and in vivo evaluation

Docetaxel (DCX) is a second generation taxane. It is approved by the U.S. Food and Drug Administration for the treatment of various types of cancer, including breast, non-small cell lung, and head and neck cancers. However, side effects, including those related to Tween 80, an excipient in current DCX formulations, can be severe. In the present study, we developed a novel solid lipid nanoparticle (SLN) composition of DCX. Trimyristin was selected from a list of high melting point triglycerides as the core lipid component of the SLNs, based on the rate at which the DCX was released from the SLNs and the stability of the SLNs. The trimyristin-based, PEGylated DCX-incorporated SLNs (DCX-SLNs) showed significantly higher cytotoxicity against various human and murine cancer cells in culture, as compared to DCX solubilized in a Tween 80/ethanol solution. Moreover, in a mouse model with pre-established tumors, the new DCX-SLNs were significantly more effective than DCX solubilized in a Tween 80/ethanol solution in inhibiting tumor growth without toxicity, likely because the DCX-SLNs increased the concentration of DCX in tumor tissues, but decreased the levels of DCX in major organs such as liver, spleen, heart, lung, and kidney. DCX-incorporated SLNs prepared with one or more high-melting point triglycerides may represent an improved DCX formulation.

Modular network construction using eQTL data: an analysis of computational costs and benefits

Background: In this paper, we consider analytic methods for the integrated analysis of genomic DNA variation and mRNA expression (also named as eQTL data), to discover genetic networks that are associated with a complex trait of interest. Our focus is the systematic evaluation of the trade-off between network size and network search efficiency in the construction of these networks.

Results: We developed a modular approach to network construction, building from smaller networks to larger ones, thereby reducing the search space while including more variables in the analysis. The goal is achieving a lower computational cost while maintaining high confidence in the resulting networks. As demonstrated in our simulation results, networks built in this way have low node/edge false discovery rate (FDR) and high edge sensitivity comparing to greedy search. We further demonstrate our method in a data set of cellular responses to two chemotherapeutic agents: docetaxel and 5-fluorouracil (5-FU), and identify biologically plausible networks that might describe resistances to these drugs.

Conclusion: In this study, we suggest that guided comprehensive searches for parsimonious networks should be considered as an alternative to greedy network searches.

Docetaxel-loaded chitosan microspheres as a lung targeted drug delivery system: in vitro and in vivo evaluation

The aim of this study was to prepare docetaxel-loaded chitosan microspheres and to evaluate their in vitro and in vivo characteristics. Glutaraldehyde crosslinked microspheres were prepared using a water-in-oil emulsification method, and characterized in terms of the morphological examination, particle size distribution, encapsulation ratio, drug-loading coefficient and in vitro release. Pharmacokinetics and biodistribution studies were used to evaluate that microspheres have more advantage than the conventional formulations. The emulsion crosslinking method was simple to prepare microspheres and easy to scale up. The formed microspheres were spherical in shape, with a smooth surface and the size was uniform (9.6 ± 0.8 μm); the encapsulation efficiency and drug loading of prepared microspheres were 88.1% ± 3.5% and 18.7% ± 1.2%, respectively. In vitro release indicated that the DTX microspheres had a well-sustained release efficacy and in vivo studies showed that the microspheres were found to release the drug to a maximum extent in the target tissue (lung). The prepared microspheres were found to possess suitable physico-chemical properties and the particle size range. The sustained release of DTX from microspheres revealed its applicability as drug delivery system to minimize the exposure of healthy tissues while increasing the accumulation of therapeutic drug in target sites.

Docetaxel-loaded liposomes: preparation, pH sensitivity, pharmacokinetics, and tissue distribution

Docetaxel (DTX), as a member of taxoid family, has been widely used in the treatment of cancers. The present study prepared pH-sensitive DTX-loaded liposomes (DTX-Lips) by thin-film dispersion method and various physico-chemical and morphological properties were examined. The pH sensitivity of in vitro DTX release and the in vivo pharmacokinetics and tissue distribution using Kunming mice were also investigated. The mean particle size and zeta potential of DTX liposomes were (277±2) nm and (-32.60±0.26) mV, respectively. Additionally, in vitro drug release study showed that the cumulative release rate was 1.3 times more at pH 5.0 than at pH 7.4, suggesting a pH-dependent release ability of DTX-Lips. Pharmacokinetic and pharmaceutical studies in comparison with Duopafei(®) showed that the half-time period (t(1/2)) and area under the curve (AUC) of DTX-Lips in mouse plasma were 1.8 times longer and 2.6 times higher, respectively, and that DTX-Lips selectively accumulated in macrophage-rich organs such as liver and spleen. These results together suggest that the DTX-Lips could be a promising formulation for the clinical administration of DTX.

Bisphosphonates and cancer: what opportunities from nanotechnology?

Bisphosphonates (BPs) are synthetic analogues of naturally occurring pyrophosphate compounds. They are used in clinical practice to inhibit bone resorption in bone metastases, osteoporosis, and Paget's disease. BPs induce apoptosis because they can be metabolically incorporated into nonhydrolyzable analogues of adenosine triphosphate. In addition, the nitrogen-containing BPs (N-BPs), second-generation BPs, act by inhibiting farnesyl diphosphate (FPP) synthase, a key enzyme of the mevalonate pathway. These molecules are able to induce apoptosis of a number of cancer cells in vitro. Moreover, antiangiogenic effect of BPs has also been reported. However, despite these promising properties, BPs rapidly accumulate into the bone, thus hampering their use to treat extraskeletal tumors. Nanotechnologies can represent an opportunity to limit BP accumulation into the bone, thus increasing drug level in extraskeletal sites of the body. Thus, nanocarriers encapsulating BPs can be used to target macrophages, to reduce angiogenesis, and to directly kill cancer cell. Moreover, nanocarriers can be conjugated with BPs to specifically deliver anticancer agent to bone tumors. This paper describes, in the first part, the state-of-art on the BPs, and, in the following part, the main studies in which nanotechnologies have been proposed to investigate new indications for BPs in cancer therapy.

Simultaneous modulation of the intrinsic and extrinsic pathways by simvastatin in mediating prostate cancer cell apoptosis

Background

Recent studies suggest the potential benefits of statins as anti-cancer agents. Mechanisms by which statins induce apoptosis in cancer cells are not clear. We previously showed that simvastatin inhibit prostate cancer cell functions and tumor growth. Molecular mechanisms by which simvastatin induce apoptosis in prostate cancer cells is not completely understood.

Methods

Effect of simvastatin on PC3 cell apoptosis was compared with docetaxel using apoptosis, TUNEL and trypan blue viability assays. Protein expression of major candidates of the intrinsic pathway downstream of simvastatin-mediated Akt inactivation was analyzed. Gene arrays and western analysis of PC3 cells and tumor lysates were performed to identify the candidate genes mediating extrinsic apoptosis pathway by simvastatin.

Results

Data indicated that simvastatin inhibited intrinsic cell survival pathway in PC3 cells by enhancing phosphorylation of Bad, reducing the protein expression of Bcl-2, Bcl-xL and cleaved caspases 9/3. Over-expression of PC3 cells with Bcl-2 or DN-caspase 9 did not rescue the simvastatin-induced apoptosis. Simvastatin treatment resulted in increased mRNA and protein expression of molecules such as TNF, Fas-L, Traf1 and cleaved caspase 8, major mediators of intrinsic apoptosis pathway and reduced protein levels of pro-survival genes Lhx4 and Nme5.

Conclusions

Our study provides the first report that simvastatin simultaneously modulates intrinsic and extrinsic pathways in the regulation of prostate cancer cell apoptosis in vitro and in vivo, and render reasonable optimism that statins could become an attractive anti-cancer agent.

Liposomal formulations of Etoposide and Docetaxel for p53 mediated enhanced cytotoxicity in lung cancer cell lines

The objective of present investigation was to develop and assess comparative enhancement in cytotoxicity of liposomal Etoposide and Docetaxel in non-small cell lung cancer cell lines after pre-treatment and co-administration of p53 tumor suppressor gene and to assess direct lung targeting of optimized formulations by dry powder inhaler technology. Cationic liposomes with and without drug were prepared and allowed to form p53-lipoplex for undertaking cytotoxicity studies in H-1299 (p53 null) and A-549 (p53 wt) cell lines. The optimized lipoplexes showed average size of 200-350 nm, zeta potential of 25-32 mV and sustained drug release up to 16-24 h. The developed liposomes and lipoplexes showed significant intracellular uptake and demonstrated enhanced cytotoxicity of 13-28 % after p53-drug co-administration and 41-63 % after p53 pre-treatment. The p53 mediated enhanced cytotoxicity by increased apoptosis and necrosis was also confirmed using Annexin V - FITC assay. The increased apoptosis suggested restored p53 function and reduced anti-apoptotic drug resistance theirby causing cell sensitization and synergism towards cytotoxicity. The studies conducted above demonstrated significant cell chemo-sensitization after p53 pre-treatment followed by Etoposide/Docetaxel liposomes administration than p53-Etoposide or p53-Docetaxel lipoplex co-administration; more significantly in Docetaxel and in H 1299 cell line. All the formulations when developed as dry powder inhalers showed significant in vitro lung deposition pattern in cascade impactor with fine particle faction of 33-37%. The study opens up a new strategy to treat lung cancer especially in cases of drug resistance. Moreover direct delivery to lung may provide an important role in complete remission of the disease due to target specificity.

Encapsulation of docetaxel in oily core polyester nanocapsules intended for breast cancer therapy

This study is designed to test the hypothesis that docetaxel [Doc] containing oily core nanocapsules [NCs] could be successfully prepared with a high percentage encapsulation efficiency [EE%] and high drug loading. The oily core NCs were generated according to the emulsion solvent diffusion method using neutral Labrafac CC and poly(d, l-lactide) [PLA] as oily core and shell, respectively. The engineered NCs were characterized for particle mean diameter, zeta potential, EE%, drug release kinetics, morphology, crystallinity, and cytotoxicity on the SUM 225 breast cancer cell line by dynamic light scattering, high performance liquid chromatography, electron microscopies, powder X-ray diffraction, and lactate dehydrogenase bioassay. Typically, the formation of Doc-loaded, oily core, polyester-based NCs was evidenced by spherical nanometric particles (115 to 582 nm) with a low polydispersity index (< 0.05), high EE% (65% to 93%), high drug loading (up to 68.3%), and a smooth surface. Powder X-ray diffraction analysis revealed that Doc was not present in a crystalline state because it was dissolved within the NCs' oily core and the PLA shell. The drug/polymer interaction has been indeed thermodynamically explained using the Flory-Huggins interaction parameters. Doc release kinetic data over 144 h fitted very well with the Higuchi model (R2 > 0.93), indicating that drug release occurred mainly by controlled diffusion. At the highest drug concentration (5 μM), the Doc-loaded oily core NCs (as a reservoir nanosystem) enhanced the native drug cytotoxicity. These data suggest that the oily core NCs are promising templates for controlled delivery of poorly water soluble chemotherapeutic agents, such as Doc.

Polymeric nanohybrids and functionalized carbon nanotubes as drug delivery carriers for cancer therapy

The scope of nanotechnology to develop target specific carriers to achieve higher therapeutic efficacy is gaining importance in the pharmaceutical and other industries. Specifically, the emergence of nanohybrid materials is posed to edge over chemotherapy and radiation therapy as cancer therapeutics. This is primarily because nanohybrid materials engage controlled production parameters in the making of engineered particles with specific size, shape, and other essential properties. It is widely expressed that these materials will significantly contribute to the next generation of medical care technology and pharmaceuticals in areas of disease diagnosis, disease prevention and many other treatment procedures. This review focuses on the currently used nanohybrid materials, polymeric nanoparticles and nanotubes, which show great potential as effective drug delivery systems for cancer therapy, as they can be grafted with cell-specific receptors and intracellular targeting molecules for the targeted delivery of therapeutics. Specifically, this article focuses on the current status, recent advancements, potentials and limitations of polymeric nanohybrids and functionalized carbon nanotubes as drug delivery carriers.

Antibody drug conjugates - Trojan horses in the war on cancer

Antibody drug conjugates (ADCs) consist of an antibody attached to a cytotoxic drug by means of a linker. ADCs provide a way to couple the specificity of a monoclonal antibody (mAb) to the cytotoxicity of a small-molecule drug and, therefore, are promising new therapies for cancer. ADCs are prodrugs that are inactive in circulation but exert their cytotoxicity upon binding to the target cancer cell. Earlier unsuccessful attempts to generate ADCs with therapeutic value have emphasized the important role each component plays in determining the efficacy and safety of the final ADC. Scientific advances in engineering antibodies for maximum efficacy as anticancer agents, identification of highly cytotoxic molecules, and generation of linkers with increased stability in circulation have all contributed to the development of the many ADCs that are currently in clinical trials. This review discusses parameters that guide the selection of the components of an ADC to increase its therapeutic window, provides a brief look at ADCs currently in clinical trials, and discusses future challenges in this field.

Mitosis is not a key target of microtubule agents in patient tumors

Mitosis-specific agents have, to date, not been clinically successful. By contrast, microtubule-targeting agents (MTAs) have a long record of success, usually attributed to the induction of mitotic arrest. Indeed, it was this success that led to the search for mitosis-specific inhibitors. We believe the clinical disappointment of mitosis-specific inhibitors stands as evidence that MTAs have been successful not only by interfering with mitosis but, more importantly, by disrupting essential interphase cellular mechanisms. In this Perspective we will review literature that supports a paradigm shift in how we think about one of our most widely used classes of chemotherapeutics-MTAs. We believe that the steady presence and constant physiological role of microtubules are responsible for the overall success of MTAs. While mitosis-specific inhibitors are effective on only a small fraction of the tumor mass (dividing cells), MTAs target tubulin, a protein that has crucial roles in both mitotic and non-mitotic cells.

Development and in vitro characterization of paclitaxel and docetaxel loaded into hydrophobically derivatized hyperbranched polyglycerols

In this study we report the development and in vitro characterization of paclitaxel (PTX) and docetaxel (DTX) loaded into hydrophobically derivatized hyperbranched polyglycerols (HPGs). Several HPGs derivatized with hydrophobic groups (C(8/10) alkyl chains) (HPG-C(8/10)-OH) and/or methoxy polyethylene glycol (MePEG) chains (HPG-C(8/10)-MePEG) were synthesized. PTX or DTX were loaded into these polymers by a solvent evaporation method and the resulting nanoparticle formulations were characterized in terms of size, drug loading, stability, release profiles, cytotoxicity, and cellular uptake. PTX and DTX were found to be chemically unstable in unpurified HPGs and large fractions (∼80%) of the drugs were degraded during the preparation of the formulations. However, both PTX and DTX were found to be chemically stable in purified HPGs. HPGs possessed hydrodynamic radii of less than 10nm and incorporation of PTX or DTX did not affect their size. The release profiles for both PTX and DTX from HPG-C(8/10)-MePEG nanoparticles were characterized by a continuous controlled release with little or no burst phase of release. In vitro cytotoxicity evaluations of PTX and DTX formulations demonstrated a concentration-dependent inhibition of proliferation in KU7 cell line. Cellular uptake studies of rhodamine-labeled HPG (HPG-C(8/10)-MePEG(13)-TMRCA) showed that these nanoparticles were rapidly taken up into cells, and reside in the cytoplasm without entering the nuclear compartment and were highly biocompatible with the KU7 cells.

Future scenarios for the treatment of advanced non-small cell lung cancer: focus on taxane-containing regimens

Despite recent progress in the development of new molecularly targeted agents, the chemotherapy regimens considered standard at the end of the last century--that is, two-drug combinations consisting of either cisplatin or carboplatin plus a third-generation agent (docetaxel, paclitaxel, gemcitabine, or vinorelbine)--remain the primary treatment option for advanced non-small cell lung cancer (NSCLC) patients. Most recently, the existing standard of care has been amended to reflect the significant survival advantage of cisplatin-pemetrexed over cisplatin-gemcitabine as first-line treatment of nonsquamous NSCLC. The addition of a biological drug (bevacizumab, cetuximab) or the use of a single-agent epidermal growth factor receptor inhibitor may further improve outcomes in selected patients. It has become increasingly clear, primarily through recent meta-analyses, that although the therapeutic equivalence of any combination of a platinum agent plus either gemcitabine, vinorelbine, docetaxel, or paclitaxel has been long accepted, each regimen has different side effects and therapeutic outcomes that allow clinicians to select the most appropriate treatment for chemotherapy-naïve patients with stage IIIB/IV NSCLC. In this review, we evaluate the available evidence and explore the role and importance of various modern chemotherapy regimens, with the aim of optimizing treatment selection and combination with biological agents. Emphasis is placed on the role of taxanes (docetaxel versus paclitaxel) in this changing landscape.

Cytochrome 450 1B1 (CYP1B1) polymorphisms associated with response to docetaxel in Castration-Resistant Prostate Cancer (CRPC) patients

Background

The selection of patients according to key genetic characteristics may help to tailor chemotherapy and optimize the treatment in Castration-Resistant Prostate Cancer (CRPC) patients. Functional polymorphisms within the cytochrome P450 1B1 (CYP1B1) gene have been associated with alterations in enzymatic expression and activity and may change sensitivity to the widely used docetaxel regimen.

Methods

CYP1B1 genotyping was performed on blood samples of 60 CRPC patients treated with docetaxel, using TaqMan probes-based assays. Association between CYP1B1-142C>G (leading to the 48ArgGly transition), 4326C>G (432LeuVal), and 4390A>G (453AsnSer) polymorphisms and treatment response, progression-free-survival (PFS) and overall-survival (OS) was estimated using Pearson χ² test, Kaplan-Meier curves and Log-rank test.

Results

Patients carrying the CYP1B1-432ValVal genotype experienced a significantly lower response-rate (P = 0.014), shorter progression-free-survival (P = 0.032) and overall-survival (P < 0.001). Multivariate analyses and correction for multiple comparisons confirmed its prognostic significance for OS. No significant associations were found among other polymorphisms and both response and clinical outcome.

Conclusions

CYP1B1-4326C>G (432LeuVal) polymorphism emerged as possible predictive marker of response and clinical outcome to docetaxel in CRPC patients and may represent a potential new tool for treatment optimization. Larger prospective trials are warranted to validate these findings, which might be applied to the future practice of CRPC treatment.

The role of chemotherapeutic drugs in the evaluation of breast tumour response to chemotherapy using serial FDG-PET

Introduction

The aims of this study were to investigate whether drug sequence (docetaxel followed by anthracyclines or the drugs in reverse order) affects changes in the maximal standard uptake volume (SUV_max) on [¹⁸F]flourodeoxyglucose positron emission tomography (FDG-PET) during neoadjuvant chemotherapy in women with locally advanced breast cancer.

Methods

Women were randomly assigned to receive either drug sequence, and FDG-PET scans were taken at baseline, after four cycles and after eight cycles of chemotherapy. Tumour response to chemotherapy was evaluated based on histology from a surgical specimen collected upon completion of chemotherapy.

Results

Sixty women were enrolled into the study. Thirty-one received docetaxel followed by anthracyclines (Arm A) and 29 received drugs in the reverse order (Arm B). Most women (83%) had ductal carcinoma and 10 women (17%) had lobular or lobular/ductal carcinoma. All but one tumour were downstaged during therapy. Overall, there was no significant difference in response between the two drug regimens. However, women in Arm B who achieved complete pathological response had mean FDG-PET SUV_max reduction of 87.7% after four cycles, in contrast to those who had no or minor pathological response. These women recorded mean SUV_max reductions of only 27% (P < 0.01). Women in Arm A showed no significant difference in SUV_max response according to pathological response. Sensitivity, specificity, accuracy and positive and negative predictive values were highest in women in Arm B.

Conclusions

Our results show that SUV_max uptake by breast tumours during chemotherapy can be dependent on the drugs used. Care must be taken when interpreting FDG-PET in settings where patients receive varied drug protocols.

Docetaxel in the treatment of non-small cell lung carcinoma: an update and analysis

Docetaxel, a semisynthetic taxane, was the first agent to show efficacy in the second-line treatment of non-small cell lung cancer (NSCLC), and has since become a mainstay of NSCLC therapy. We review its mode of action, pharmacology, toxicity and efficacy and describe both its established role in the treatment of NSCLC and future directions in research. Docetaxel works primarily by promoting microtubule assembly and polymerization, and through this hyperstabilization, causes cell cycle arrest and death. The primary toxicity of docetaxel is neutropenia, which can be mitigated by weekly administration in selected patients. Less common toxicities are peripheral edema, which can be reduced by appropriate premedication and interstitial pneumonitis. Hypersensitivity reactions are less frequent than with paclitaxel. Docetaxel has shown a survival and quality of life advantage as a single agent first- and second-line versus placebo, as well as first-line in a platinum-based doublet therapy compared to a single agent. Increasingly docetaxel has also been used effectively in adjuvant regimens in earlier stages of the disease. Future areas of research include combinations with novel targeted therapies, and a greater understanding of biomarkers that might help predict efficacy and personalize therapy.

Cellular cytotoxicity and in-vivo biodistribution of docetaxel poly(lactide-co-glycolide) nanoparticles

Docetaxel (DTX) is one of the most effective antineoplastic drugs. However, its current clinical administration, formulated in tween80, causes serious side effects. This study is focused on preparation and evaluation of poly(lactide-co-glycolide) nanoparticles (NPs) containing DTX to remove tween80. Drug encapsulation efficiency, in-vitro drug release, cellular cytotoxicity, and in-vivo biodistribution of NPs in mice after intravenous administration were investigated. The average diameter of the NPs was approximately 172-178 nm with encapsulation efficiency of 68%. A burst release of approximately 30% (w/w) of the loaded drug followed by a sustained release profile was observed. Cellular mortality of the NPs was more than or at least as great as DTX free drug; for example, cell viability measured at 100 nmol/l drug concentration was decreased from 50.9% for DTX free drug to 15.9% for the NP formulation after 48 h incubation with T47D cells. The DTX plasma amount remained at a good level (13% of the initial dose) in the NP formulation compared with the DTX conventional formulation, which is approximately 0.5% of the initial dose, was present in plasma up to 2 h. Poly(lactide-co-glycolide) NPs containing DTX prepared in this study may be regarded as a suitable and superior formulation for the current formulation in the market containing tween80 with improved cancerous cell mortality and biodistribution characteristics.

CD44-positive cells are responsible for gemcitabine resistance in pancreatic cancer cells

Accumulating evidence suggests that tumors are composed of a heterogeneous cell population with a small subset of cancer stem cells (CSCs) that sustain tumor formation and growth. Recently, there have been efforts to explain drug resistance of cancer cells based on the concept of CSCs having an intrinsic detoxifying mechanism. In the present study, to investigate the role of CSCs in acquiring chemoresistance in pancreatic cancer, gemcitabine-resistant cells were established by exposure to serially escalated doses of gemcitabine in HPAC and CFPAC-1 cells. Gemcitabine-resistant cells were more tumorigenic in vitro and in vivo, and had greater sphere-forming activity than parental cells. After high-dose gemcitabine treatment to eliminate most of the cells, CD44(+) cells proliferated and reconstituted the population of resistant cells. CD44(+)CD24(+)ESA(+) cells remained as a small subset in the resistant cell population. Among ATP-binding cassette (ABC) transporters, which are known as the mechanism of drug resistance in CSCs, ABCB1 (MDR1) was significantly augmented during the acquisition of drug resistance. ABC transporter inhibitor verapamil resensitized the resistant cells to gemcitabine in a dose-dependent manner and RNA interference of CD44 inhibited the clonogenic activity of resistant cells. In human pancreatic cancer samples, CD44 expression was correlated with histologic grade and the patients with CD44-positive tumors showed poor prognosis. These data indicate that cancer stem-like cells were expanded during the acquisition of gemcitabine resistance and in therapeutic application, targeted therapy against the CD44 or ABC transporter inhibitors could be applied to overcome drug resistance in the treatment of pancreatic cancer.

Targeting bone metastases with a bispecific anticancer and antiangiogenic polymer-alendronate-taxane conjugate

A polymer therapeutic designed for combination anticancer and antiangiogenic therapy inhibited the proliferation of prostate carcinoma cells and the proliferation, migration, and tube-formation of endothelial cells. The nanoconjugate was formed from an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer, the bisphosphonate alendronate (for bone targeting), and the chemotherapy agent paclitaxel (PTX), which is cleaved by cathepsin B (see scheme).

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.

Kaempferol and quercetin stimulate granulocyte-macrophage colony-stimulating factor secretion in human prostate cancer cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) holds immunotherapeutic promise in prostate cancer as it activates the host immune system. Increased production of GM-CSF by cancer cells may facilitate host immunosurveillence by the dendritic cells (DC). Here, we studied the effects of kaempferol (K) and quercetin (Q) on the production of GM-CSF in PC-3 cells. Human cytokine antibody array revealed that treatment with K or Q increased GM-CSF release by PC-3 cells. We further observed by ELISA that K and Q in a concentration-dependent manner increased GM-CSF production without affecting its mRNA levels. Inhibitors of vesicular traffic through the endoplasmic reticulum and Golgi-blocked GM-CSF secretory stimulation. A microtubule-stabilizing agent stimulated GM-CSF release, whereas tubulin and actin depolymerizers suppressed K- or Q-stimulated secretion of GM-CSF. Depletion of extracellular or intracellular calcium ion inhibited the GM-CSF secretion upregulated by both K and Q. Furthermore, we showed that K- and Q-stimulated GM-CSF production involves PLC, PKC, and MEK1/2 activation. Treating human DC with the conditioned medium of K- or Q-incubated PC-3 cells increased chemotaxis of DC, which was significantly attenuated when the conditioned medium was incubated with the neutralizing antibody against GM-CSF. Taken together, our results demonstrate that K and Q activate an immune response in the prostate cancer cells by stimulating GM-CSF production, which in turn could result in the recruitment of DCs to the tumor site.