Chemotherapy dosing schedule influences drug resistance development in ovarian cancer

Role of Non-coding RNAs in the Response of Glioblastoma to Temozolomide

Chemotherapy and radiotherapy are widely used in clinical practice across the globe as cancer treatments. Intrinsic or acquired chemoresistance poses a significant problem for medical practitioners and researchers, causing tumor recurrence and metastasis. The most dangerous kind of malignant brain tumor is called glioblastoma multiforme (GBM) that often recurs following surgery. The most often used medication for treating GBM is temozolomide chemotherapy; however, most patients eventually become resistant. Researchers are studying preclinical models that accurately reflect human disease and can be used to speed up drug development to overcome chemoresistance in GBM. Non-coding RNAs (ncRNAs) have been shown to be substantial in regulating tumor development and facilitating treatment resistance in several cancers, such as GBM. In this work, we mentioned the mechanisms of how different ncRNAs (microRNAs, long non-coding RNAs, circular RNAs) can regulate temozolomide chemosensitivity in GBM. We also address the role of these ncRNAs encapsulated inside secreted exosomes.

Metronomic chemotherapy in hematology: Lessons from preclinical and clinical studies to build a solid rationale for future schedules

Metronomic chemotherapy (mCHEMO), based on frequent, regular administration of low, but pharmacologically active drug doses, optimizes antitumor efficacy by targeting multiple targets and reducing toxicity of antineoplastic drugs. This minireview will summarize preclinical and clinical studies on cytotoxic drugs given at weekly, daily, or at continuous metronomic schedules alone or in combination with novel targeted agents for hematological malignancies, including lymphoma, multiple myeloma, and leukemia. Most of the preclinical in vitro and in vivo studies have reported a significant benefit of both mCHEMO monotherapy and combinatorial regimens compared with chemotherapy at the maximum tolerated dose. However, the combination of mCHEMO with targeted drugs is still little explored in the hematologic clinical setting. Data obtained from preclinical studies on low dose metronomic chemotherapy in hematological malignancies clearly suggested the possibility to clinically investigate more tolerable and effective strategies for the treatment of patients with advanced hematological malignancies, or at least for those frail and elderly patients, who are not eligible or resistant to standard treatments.

HOXA9 transcription factor is a double-edged sword: from development to cancer progression

The HOXA9 transcription factor serves as a molecular orchestrator in cancer stemness, epithelial-mesenchymal transition (EMT), metastasis, and generation of the tumor microenvironment in hematological and solid malignancies. However, the multiple modes of regulation, multifaceted functions, and context-dependent interactions responsible for the dual role of HOXA9 as an oncogene or tumor suppressor in cancer remain obscure. Hence, unravelling its molecular complexities, binding partners, and interacting signaling molecules enables us to comprehend HOXA9-mediated transcriptional programs and molecular crosstalk. However, it is imperative to understand its central role in fundamental biological processes such as embryogenesis, foetus implantation, hematopoiesis, endothelial cell proliferation, and tissue homeostasis before designing targeted therapies. Indeed, it presents an enormous challenge for clinicians to selectively target its oncogenic functions or restore tumor-suppressive role without altering normal cellular functions. In addition to its implications in cancer, the present review also focuses on the clinical applications of HOXA9 in recurrence and drug resistance, which may provide a broader understanding beyond oncology, open new avenues for clinicians for accurate diagnoses, and develop personalized treatment strategies. Furthermore, we have also discussed the existing therapeutic options and accompanying challenges in HOXA9-targeted therapies in different cancer types.

Preparation of Liposome Gel by Calcium Cross-Linking Induces the Long-Term Release of DOX to Improve the Antitumor Effect

Doxorubicin (DOX) is one of the most commonly used anticancer drugs; however, its clinical application is greatly limited due to its toxicity and chemotherapy resistance. The delivery of DOX by liposomes (Lipos) can improve the blood circulation time in vivo and reduce toxic side effects, but the drug's accumulation in the tumor is often insufficient for effective treatment. In this study, we present a calcium cross-linked liposome gel for the encapsulation of DOX, demonstrating its superior long-term release capabilities compared to conventional Lipos. By leveraging this enhanced long-term release, we can enhance drug accumulation within tumors, ultimately leading to improved antitumor efficacy. Lipos were prepared using the thin-film dispersion method in this study. We utilized the ion-responsiveness of glutathione-gelatin (GSH-GG) to form the gel outside the Lipos and named the nanoparticles coated with GSH-GG on the outside of Lipos as Lipos@GSH-GG. The average size of Lipos@GSH-GG was around 342.9 nm, with a negative charge of -25.6 mV. The in vitro experiments revealed that Lipos@GSH-GG exhibited excellent biocompatibility and slower drug release compared to conventional Lipos. Further analysis of cellular uptake and cytotoxicity demonstrated that Lipos@GSH-GG loading DOX (DOX&Lipos@GSH-GG) exhibited superior long-term release effects and lower toxic side effects compared to Lipos loading DOX (DOX&Lipos). Additionally, the findings regarding the long-term release effect in vivo and the tumor accumulation within tumor-bearing mice of Lipos@GSH-GG suggested that, compared to Lipos, it demonstrated superior long-term release capabilities and achieved greater drug accumulation within tumors. In vivo antitumor efficacy experiments showed that DOX&Lipos@GSH-GG demonstrated superior antitumor efficacy to DOX&Lipos. Our study highlights Lipos@GSH-GG as a promising nanocarrier with the potential to enhance efficacy and safety by means of long-term release effects and may offer an alternative approach for effective antitumor therapy in the future.

RPN2 in cancer: An overview

Oncogenes together with tumor suppresser genes are confirmed to regulate tumor phenotype in human cancers. RPN2, widely verified as an oncogene, encodes a protein that is part of an N-oligosaccharyl transferase, and is observed to be aberrantly expressed in human malignancies. Accumulating evidence unveils the vital functions of RPN2, contributing to tumorigenicity, metastasis, progression, and multi-drug resistance. Furthermore, previous studies partly indicated that RPN2 was involved in tumor progression via contributing to N-glycosylation and regulating multiple signaling pathways. In addition, RPN2 was also confirmed as a downstream target involved in tumor progression. Moreover, with demonstrated prognosis value and therapeutic target, RPN2 was also determined as a promising biomarker for forecasting patients' prognostic and therapy efficacy. In the present review, we aimed to summarize the present studies of RPN2 in cancer, and enhance the understanding of RPN2's extensive functions and clinical significances.

circTOP2A functions as a ceRNA to promote glioma progression by upregulating RPN2

Competing endogenous RNA (ceRNA)-mediated signaling pathway dysregulation provides great insight into comprehensively understanding the molecular mechanism and combined targeted therapy for glioblastoma. circRNA is characterized by high stability, tissue/developmental stage-specific expression and abundance in brain and plays significant roles in the initiation and progression of cancer. Our previous published data have demonstrated that RPN2 was significantly upregulated in glioma and promoted tumor progression via the activation of the Wnt/β-catenin pathway. Furthermore, we proved that miR-422a regulated the Wnt/β-catenin signaling pathway by directly targeting RPN2. In this study, based on the glioblastoma microarray profiles, we identified the upstream circTOP2A, which completely bound to miR-422a and was co-expressed with the RPN2. circTOP2A was significantly overexpressed in glioma and conferred a poor prognosis. circTOP2A could regulate RPN2 expression by sponging miR-422a, verified by western blot, dual-luciferase reporter gene assay, and RNA pull-down assay. Functional assays including CCK8, transwell and FITC-annexin V were performed to explore the RPN2-mediated role of the circTOP2A effect on the glioma malignant phenotype. Additionally, TOP/FOP and immunofluorescence analysis were used to confirm that sh-circTOP2A could suppress the Wnt/β-catenin pathway partly through RPN2. Finally, a tumor xenograft model was applied to validate the biological function of circTOP2A in vivo. Taken together, our findings reveal the critical role of circTOP2A in promoting glioma proliferation and invasion via a ceRNA mechanism and provide an exploitable biomarker and therapeutic target for glioma patients.

Mathematical characterization of population dynamics in breast cancer cells treated with doxorubicin

The development of chemoresistance remains a significant cause of treatment failure in breast cancer. We posit that a mathematical understanding of chemoresistance could assist in developing successful treatment strategies. Towards that end, we have developed a model that describes the cytotoxic effects of the standard chemotherapeutic drug doxorubicin on the MCF-7 breast cancer cell line. We assume that treatment with doxorubicin induces a compartmentalization of the breast cancer cell population into surviving cells, which continue proliferating after treatment, and irreversibly damaged cells, which gradually transition from proliferating to treatment-induced death. The model is fit to experimental data including variations in drug concentration, inter-treatment interval, and number of doses. Our model recapitulates tumor cell dynamics in all these scenarios (as quantified by the concordance correlation coefficient, CCC > 0.95). In particular, superior tumor control is observed with higher doxorubicin concentrations, shorter inter-treatment intervals, and a higher number of doses (p < 0.05). Longer inter-treatment intervals require adapting the model parameterization after each doxorubicin dose, suggesting the promotion of chemoresistance. Additionally, we propose promising empirical formulas to describe the variation of model parameters as functions of doxorubicin concentration (CCC > 0.78). Thus, we conclude that our mathematical model could deepen our understanding of the cytotoxic effects of doxorubicin and could be used to explore practical drug regimens achieving optimal tumor control.

NIR irradiation-controlled drug release utilizing injectable hydrogels containing gold-labeled liposomes for the treatment of melanoma cancer

Drug-based chemotherapy is associated with serious side effects. We developed a chemotherapeutic system comprising a chitosan hydrogel (CH-HG) containing gold cluster-labeled liposomal doxorubicin (DOX) (CH-HG-GL_DOX) as an injectable drug depot system. CH-HG-GL_DOX can be directly injected into tumor tissue without a surgical procedure, allowing this system to act as a reservoir for liposomal DOX. CH-HG-GL_DOX enhanced the retention time of DOX in tumor tissue and controlled its release in response to near-infrared (NIR) irradiation, resulting in significant inhibition of tumor growth and reduced DOX-related toxicity. The combined effect of CH-HG-GL_DOX and poly (D,L-lactide-co-glycolic acid) nanoparticle-based vaccines increased cytotoxic CD8+ T cell immunity, leading to enhanced synergistic therapeutic efficacy. CH-HG-GL_DOX provides an advanced therapeutic approach for local drug delivery and controlled release of DOX, resulting in reduced toxicity. Here, we suggest a combination strategy for chemo- and immunotherapies, as well as in nanomedicine applications. STATEMENT OF SIGNIFICANCE: We developed an injectable hydrogel containing gold cluster-labeled liposomes for sustained drug release at the tumor site. Moreover, we demonstrated the combined therapeutic efficacy of a hydrogel system and a nanoparticle-based immunotherapeutic vaccine for melanoma cancer. Thus, we show a potential combination approach for chemo- and immunotherapies for cancer treatment.

Treatment scheduling effects on the evolution of drug resistance in heterogeneous cancer cell populations

The effect of scheduling of targeted therapy combinations on drug resistance is underexplored in triple-negative breast cancer (TNBC). TNBC constitutes heterogeneous cancer cell populations the composition of which can change dynamically during treatment resulting in the selection of resistant clones with a fitness advantage. We evaluated crizotinib (ALK/MET inhibitor) and navitoclax (ABT-263; Bcl-2/Bcl-xL inhibitor) combinations in a large design consisting of 696 two-cycle sequential and concomitant treatment regimens with varying treatment dose, duration, and drug holiday length over a 26-day period in MDA-MB-231 TNBC cells and found that patterns of resistance depend on the schedule and sequence in which the drugs are given. Further, we tracked the clonal dynamics and mechanisms of resistance using DNA-integrated barcodes and single-cell RNA sequencing. Our study suggests that longer formats of treatment schedules in vitro screening assays are required to understand the effects of resistance and guide more realistically in vivo and clinical studies.

ABCB1 and ABCG2 restricts the efficacy of gedatolisib (PF-05212384), a PI3K inhibitor in colorectal cancer cells

Background

Overexpression of ABC transporters is a big challenge on cancer therapy which will lead cancer cells resistance to a series of anticancer drugs. Gedatolisib is a dual PI3K and mTOR inhibitor which is under clinical evaluation for multiple types of malignancies, including colorectal cancer. The growth inhibitory effects of gedatolisib on colorectal cancer cells have been specifically studied. However, the role of ABC transporters on gedatolisib resistance remained unclear. In present study, we illustrated the role of ABC transporters on gedatolisib resistance in colorectal cancer cells.

Methods

Cell viability investigations of gedatolisib on colorectal cancer cells were determined by MTT assays. The verapamil and Ko143 reversal studies were determined by MTT assays as well. ABCB1 and/or ABCG2 siRNA interference assays were conducted to verify the role of ABCB1- and ABCG2-overexpression on gedatolisib resistance. The accumulation assays of gedatolisib were conducted using tritium-labeled paclitaxel and mitoxantrone. The effects of gedatolisib on ATPase activity of ABCB1 or ABCG2 were conducted using PREDEASY ATPase Kits. The expression level of ABCB1 and ABCG2 after gedatolisib treatment were conducted by Western blotting and immunofluorescence assays. The well-docked position of gedatolisib with crystal structure of ABCB1 and ABCG2 were simulated by Autodock vina software. One-way ANOVA was used for the statistics analysis.

Results

Gedatolisib competitively increased the accumulation of tritium-labeled substrate-drugs in both ABCB1- and ABCG2-overexpression colorectal cancer cells. Moreover, gedatolisib significantly increased the protein expression level of ABCB1 and ABCG2 in colorectal cancer cells. In addition, gedatolisib remarkably simulated the ATPase activity of both ABCB1 and ABCG2, suggesting that gedatolisib is a substrate drug of both ABCB1 and ABCG2 transporters. Furthermore, a gedatolisib-resistance colorectal cancer cell line, SW620/GEDA, was selected by increasingly treatment with gedatolisib to SW620 cells. The SW620/GEDA cell line was proved to resistant to gedatolisib and a series of chemotherapeutic drugs, except cisplatin. The ABCB1 and ABCG2 were observed overexpression in SW620/GEDA cell line.

Conclusions

These findings suggest that overexpression of ABCB1 and ABCG2 may restrict the efficacy of gedatolisib in colorectal cancer cells, while co-administration with ABC transporter inhibitors may improve the potency of gedatolisib.

RPN2 is targeted by miR-181c and mediates glioma progression and temozolomide sensitivity via the wnt/β-catenin signaling pathway

Accumulating evidence indicates that the dysregulation of the miRNAs/mRNA-mediated carcinogenic signaling pathway network is intimately involved in glioma initiation and progression. In the present study, by performing experiments and bioinformatics analysis, we found that RPN2 was markedly elevated in glioma specimens compared with normal controls, and its upregulation was significantly linked to WHO grade and poor prognosis. Knockdown of RPN2 inhibited tumor proliferation and invasion, promoted apoptosis, and enhanced temozolomide (TMZ) sensitivity in vitro and in vivo. Mechanistic investigation revealed that RPN2 deletion repressed β-catenin/Tcf-4 transcription activity partly through functional activation of glycogen synthase kinase-3β (GSK-3β). Furthermore, we showed that RPN2 is a direct functional target of miR-181c. Ectopic miR-181c expression suppressed β-catenin/Tcf-4 activity, while restoration of RPN2 partly reversed this inhibitory effect mediated by miR-181c, implying a molecular mechanism in which TMZ sensitivity is mediated by miR-181c. Taken together, our data revealed a new miR-181c/RPN2/wnt/β-catenin signaling axis that plays significant roles in glioma tumorigenesis and TMZ resistance, and it represents a potential therapeutic target, especially in GBM.

Multiscale Model Identifies Improved Schedule for Treatment of Acute Myeloid Leukemia In Vitro With the Mcl-1 Inhibitor AZD5991

Anticancer efficacy is driven not only by dose but also by frequency and duration of treatment. We describe a multiscale model combining cell cycle, cellular heterogeneity of B‐cell lymphoma 2 family proteins, and pharmacology of AZD5991, a potent small‐molecule inhibitor of myeloid cell leukemia 1 (Mcl‐1). The model was calibrated using in vitro viability data for the MV‐4‐11 acute myeloid leukemia cell line under continuous incubation for 72 hours at concentrations of 0.03–30 μM. Using a virtual screen, we identified two schedules as having significantly different predicted efficacy and showed experimentally that a “short” schedule (treating cells for 6 of 24 hours) is significantly better able to maintain the rate of cell kill during treatment than a “long” schedule (18 of 24 hours). This work suggests that resistance can be driven by heterogeneity in protein expression of Mcl‐1 alone without requiring mutation or resistant subclones and demonstrates the utility of mathematical models in efficiently identifying regimens for experimental exploration.

MicroRNA‑422a functions as a tumor suppressor in glioma by regulating the Wnt/β‑catenin signaling pathway via RPN2

MicroRNAs (miRs), which act as crucial regulators of oncogenes and tumor suppressors, have been confirmed to play a significant role in the initiation and progression of various malignancies, including glioma. The present study analyzed the expression and roles of miR‑422a in glioma, and reverse transcription‑quantitative PCR confirmed that miR‑422a expression was significantly lower in glioblastoma multiforme (GBM) samples and cell lines compared with the low‑grade glioma samples and the H4 cell line, respectively. miR‑422a overexpression suppressed proliferation and invasion, and induced apoptosis in LN229 and U87 cell lines. Luciferase reporter assay, western blotting and RNA immunoprecipitation analysis revealed that ribophorin II (RPN2) is a direct functional target of miR‑422a. Additionally, the overexpression of RPN2 partially reversed the miR‑422a‑mediated inhibitory effect on the malignant phenotype. Mechanistic investigation demonstrated that the upregulation of miR‑422a inhibited β‑catenin/transcription factor 4 transcriptional activity, at least partially through RPN2, as indicated by in vitro and in vivo experiments. Furthermore, RPN2 expression was inversely correlated with miR‑422a expression in GBM specimens and predicted patient survival in the Chinese Glioma Genome Atlas, UALCAN, Gene Expression Profiling Interactive Analysis databases. In conclusion, the present data reveal a new miR‑422a/RPN2/Wnt/β‑catenin signaling axis that plays critical roles in glioma tumorigenesis, and it represents a potential therapeutic target for GBM.

Delicate Balances in Cancer Chemotherapy: Modeling Immune Recruitment and Emergence of Systemic Drug Resistance

Metronomic chemotherapy can drastically enhance immunogenic tumor cell death. However, the mechanisms responsible are still incompletely understood. Here, we develop a mathematical model to elucidate the underlying complex interactions between tumor growth, immune system activation, and therapy-mediated immunogenic cell death. Our model is conceptually simple, yet it provides a surprisingly excellent fit to empirical data obtained from a GL261 SCID mouse glioma model treated with cyclophosphamide on a metronomic schedule. The model includes terms representing immune recruitment as well as the emergence of drug resistance during prolonged metronomic treatments. Strikingly, a single fixed set of parameters, adjusted neither for individuals nor for drug schedule, recapitulates experimental data across various drug regimens remarkably well, including treatments administered at intervals ranging from 6 to 12 days. Additionally, the model predicts peak immune activation times, rediscovering experimental data that had not been used in parameter fitting or in model construction. Notably, the validated model suggests that immunostimulatory and immunosuppressive intermediates are responsible for the observed phenomena of resistance and immune cell recruitment, and thus for variation of responses with respect to different schedules of drug administration.

Overexpression of RPN2 suppresses radiosensitivity of glioma cells by activating STAT3 signal transduction

Background

Radiation therapy is the primary method of treatment for glioblastoma (GBM). Therefore, the suppression of radioresistance in GBM cells is of enormous significance. Ribophorin II (RPN2), a protein component of an N-oligosaccharyl transferase complex, has been associated with chemotherapy drug resistance in multiple cancers, including GBM. However, it remains unclear whether this also plays a role in radiation therapy resistance in GBM.

Methods

We conducted a bioinformatic analysis of RPN2 expression using the UCSC Cancer Genomics Browser and GEPIA database and performed an immunohistochemical assessment of RPN2 expression in biopsy specimens from 34 GBM patients who had received radiation-based therapy. We also studied the expression and function of RPN2 in radiation-resistant GBM cells.

Results

We found that RPN2 expression was upregulated in GBM tumors and correlated with poor survival. The expression of RPN2 was also higher in GBM patients with tumor recurrence, who were classified to be resistant to radiation therapy. In the radiation-resistant GBM cells, the expression of RPN2 was also higher than in the parental cells. Depletion of RPN2 in resistant cells can sensitize these cells to radiation-induced apoptosis, and overexpression of RPN2 had the reverse effect. Myeloid cell leukemia 1 (MCL1) was found to be the downstream target of RPN2, and contributed to radiation resistance in GBM cells. Furthermore, STAT3 was found to be the regulator of MCL1, which can be activated by RPN2 dysregulation.

Conclusion

Our study has revealed a novel function of RPN2 in radiation-resistant GBM, and has shown that MCL1 depletion or suppression could be a promising method of therapy to overcome the resistance promoted by RPN2 dysregulation.

Wanna Get Away? Maintenance Treatments and Chemotherapy Holidays in Gynecologic Cancers

Epithelial ovarian cancer has a very high rate of relapse after primary therapy; historically approximately 70% of patients with a complete clinical response to surgery and adjuvant chemotherapy will relapse and die of the disease. Although this number has slowly improved, cure rates remain less than 50%. As such, maintenance therapy with the aim of preventing or delaying disease relapse and the goal of improving overall survival has been the subject of intense study. Numerous earlier studies with agents ranging from radioactive phosphorus to extended frontline therapy or to monthly taxol administration demonstrated encouraging improvements in progression-free survival (PFS) only to find, disappointingly, no benefit in overall survival. In addition, the PFS advantage of maintenance therapy was associated with disconcerting side effects such that maintenance therapy was not adapted as standard of care. Studies with bevacizumab and PARP inhibitors have demonstrated a PFS advantage with a manageable side-effect profile. However, an overall survival advantage remains unclear, and the use of these approaches thus remains controversial. Furthermore, in recurrent disease, the length of chemotherapy and benefits of extended chemotherapy is unclear. Thus, additional trials assessing maintenance strategies in ovarian and other gynecologic malignancies are needed.

Mechanisms and therapeutic potentials of cancer immunotherapy in combination with radiotherapy and/or chemotherapy

Immunotherapies based on T cells have gained significant success in the treatment of diverse cancers, however, several limitations also exist, including low response, acquired resistance and severe side effects, which lead to unfavorable outcomes. Recent studies found that traditional therapies, radiotherapy and/or chemotherapy may affect the immune condition in situ and cause abscopal effect, which may improve the response of immunotherapies, enhance the efficiency, and reduce the untoward effect. Here, we review the mechanisms uncovering the cancer immunotherapy and immunogenic effects of radiotherapy and chemotherapy, aiming to highlight the principles underlying the therapeutic potentials of cancer immunotherapy in combination with radiotherapy and/or chemotherapy and ultimately guide better designs for future synergistic cancer therapies.

miR-495 sensitizes MDR cancer cells to the combination of doxorubicin and taxol by inhibiting MDR1 expression

MDR1 is highly expressed in MDR A2780DX5 ovarian cancer cells, MDR SGC7901R gastric cancer cells and recurrent tumours. It pumps cytoplasmic agents out of cells, leading to decreased drug accumulation in cells and making cancer cells susceptible to multidrug resistance. Here, we identified that miR-495 was predicted to target ABCB1, which encodes protein MDR1. To reduce the drug efflux and reverse MDR in cancer cells, we overexpressed a miR-495 mimic in SGC7901R and A2780DX cells and in transplanted MDR ovarian tumours in vivo. The results indicated that the expression of MDR1 in the above cells or tumours was suppressed and that subsequently the drug accumulation in the MDR cells was decreased, cell death was increased, and tumour growth was inhibited after treatment with taxol-doxorubicin, demonstrating increased drug sensitivity. This study suggests that pre-treatment with miR-495 before chemotherapy could improve the curative effect on MDR1-based MDR cancer.

Enterolactone glucuronide and β-glucuronidase in antibody directed enzyme prodrug therapy for targeted prostate cancer cell treatment

Evidence from preclinical and animal studies demonstrated an anticancer effect of flaxseed lignans, particularly enterolactone (ENL), against prostate cancer. However, extensive first-pass metabolism following oral lignan consumption results in their systemic availability primarily as glucuronic acid conjugates (ENL-Gluc) and their modest in vivo effects. To overcome the unfavorable pharmacokinetics and improve their effectiveness in prostate cancer, antibody-directed enzyme prodrug therapy (ADEPT) might offer a novel strategy to allow for restricted activation of ENL from circulating ENL-Gluc within the tumor environment. The anti-prostate-specific membrane antigen (PSMA) antibody D7 was fused with human β-glucuronidase (hβG) via a flexible linker. The binding property of the fusion construct, D7-hβG, against purified or cell surface PSMA was determined by flow cytometry and Octet Red 384 system, respectively, with a binding rate constant, K _d, of 2.5 nM. The enzymatic activity of D7-hβG was first tested using the probe, 4-methylumbelliferone glucuronide. A 3.8-fold greater fluorescence intensity was observed at pH 4.5 at 2 h compared with pH 7.4. The ability of D7-hβG to activate ENL from ENL-Gluc was tested and detected using LC-MS/MS. Enhanced generation of ENL was observed with increasing ENL-Gluc concentrations and reached 3613.2 ng/mL following incubation with 100 μM ENL-Gluc at pH 4.5 for 0.5 h. D7-hβG also decreased docetaxel IC₅₀ value from 23 nM to 14.9 nM in C4-2 cells. These results confirmed the binding and activity of D7-hβG and additional in vitro investigation is needed to support the future possibility of introducing this ADEPT system to animal models.

Bortezomib, carfilzomib and ixazomib do not mediate relevant transporter-based drug-drug interactions

In order to optimize the clinical application of an increasing number of proteasome inhibitors, investigations into the differences between their respective pharmacodynamic and pharmacokinetic profiles, including their ability to act as a perpetrator in drug-drug interactions, are warranted. Therefore, in the present in vitro study, it was investigated whether bortezomib, carfilzomib and ixazomib are able to alter the expression, and/or the activity, of specific drug transporters generally relevant for pharmacokinetic drug-drug interactions. Through induction experiments, the current study demonstrated that the aforementioned three proteasome inhibitors do not induce mRNA expression of the transporter genes ATP binding cassette (ABC)B1, C1, C2 and G2 in the LS180 cell line, which was used as a model for systemic induction. By contrast, in certain myeloma cell lines, ixazomib provoked minor alterations in individual transporter gene expression. None of the proteasome inhibitors tested relevantly inhibited drug transporters within the range of physiological plasma concentrations. Taken together, transporter-based drug-drug interactions are unlikely to be a primary concern in the clinical application of the tested compounds.

Super Aqueous Solubility of Albendazole in β-Cyclodextrin for Parenteral Application in Cancer therapy

Poor aqueous solubility of anticancer drug, albendazole (ABZ), prevents parenteral application. Here, we demonstrate how to increase the aqueous solubility of ABZ to 6- 8 mg/ml using sulfobutylether - β-cyclodextrin (SBE-β-CD) or Hydroxypropyl- β-cyclodextrin (HP- β-CD) by manipulation of complexation parameters such as the physical state of ABZ (ionized in acetic acid), the concentration of ionised ABZ, agitation time and temperature. Solubility was first examined with suspension of excess ABZ powder in cyclodextrin (CD) solutions at pH (2.3, 4.0 & 7.0), subsequently with excess ionised ABZ [ABZ] at pH. 2.3 with the determination of optimal quantity of [ABZ] use for maximal complexation. Complexation time, temperature effect, stability of formulation, with in vitro and in vivo cytotoxicity of [ABZ]-SBE-β-CD was assessed. Suspended ABZ formulation at pH 2.3 showed maximum solubilisation of 2.29 & 1.72 mg/ml, whilst excess addition of [ABZ] showed poor complexation (1.26 & 1.20 mg/ml) in SBE-β-CD & HP- β-CD, respectively. The addition of 8.0 mg/ml and 7.0 mg/ml of [ABZ] to 40% CD solutions at 25ºC showed maximum complexation with SBE-β-CD & HP- β-CD, respectively, at three days, with 2 weeks stability. [ABZ] complexed with SBE-β-CD showed potent cytotoxicity (in vitro & in vivo) in ovarian tumour cells. Hence, the current method may be used for solubilising ABZ for parenteral use.

Resistance to metronomic chemotherapy and ways to overcome it

Therapeutic resistance is amongst the major determinants of cancer mortality. Contrary to initial expectations, antivascular therapies are equally prone to inherent or acquired resistance as other cancer treatment modalities. However, studies into resistance to vascular endothelial growth factor pathway inhibitors revealed distinct mechanisms of resistance compared to conventional cytotoxic therapy. While some of these novel mechanisms of resistance also appear to be functional regarding metronomic chemotherapy, herein we summarize available evidence for mechanisms of resistance specifically described in the context of metronomic chemotherapy. Numerous preclinically identified molecular targets and pathways represent promising avenues to overcome resistance and enhance the benefits achieved with metronomic chemotherapy eventually. However, there are considerable challenges to clinically translate the preclinical findings.

ATP-binding cassette transporters in tumor endothelial cells and resistance to metronomic chemotherapy

Drug resistance is a major problem in anticancer therapy. ATP-binding cassette (ABC) transporters have a role in the multidrug resistance. A new regimen of chemotherapy has been proposed, called "metronomic chemotherapy". Metronomic chemotherapy is the frequent, regular administration of drug doses designed to maintain low, but active, concentrations of chemotherapeutic drugs over prolonged periods of time, without causing serious toxicities. Metronomic chemotherapy regimens were developed to optimize the antitumor efficacy of agents that target the tumor vasculature instead of tumor cells, and to reduce toxicity of antineoplastic drugs [1]. Nevertheless, recent studies revealed that ABC transporters are expressed at a higher level in the endothelium in the tumor. To avoid resistance to metronomic anti-angiogenic chemotherapy, ABC transporter inhibition of tumor endothelial cells may be a promising strategy. In this mini-review, we discuss the possible mechanism of resistance to metronomic chemotherapy from the viewpoint of tumor endothelial cell biology, focusing on ABC transporters.

Metronomic chemotherapy and immunotherapy in cancer treatment

Systemic chemotherapy given at maximum tolerated doses (MTD) has been the mainstay of cancer treatment for more than half a century. In some chemosensitive diseases such as hematologic malignancies and solid tumors, MTD has led to complete remission and even cure. The combination of maintenance therapy and standard MTD also can generate good disease control; however, resistance to chemotherapy and disease metastasis still remain major obstacles to successful cancer treatment in the majority of advanced tumors. Metronomic chemotherapy, defined as frequent administration of chemotherapeutic agents at a non-toxic dose without extended rest periods, was originally designed to overcome drug resistance by shifting the therapeutic target from tumor cells to tumor endothelial cells. Metronomic chemotherapy also exerts anti-tumor effects on the immune system (immunomodulation) and tumor cells. The goal of immunotherapy is to enhance host anti-tumor immunities. Adding immunomodulators such as metronomic chemotherapy to immunotherapy can improve the clinical outcomes in a synergistic manner. Here, we review the anti-tumor mechanisms of metronomic chemotherapy and the preliminary research addressing the combination of immunotherapy and metronomic chemotherapy for cancer treatment in animal models and in clinical setting.

Limiting the development of anti-cancer drug resistance in a spatial model of micrometastases

While chemoresistance in primary tumors is well-studied, much less is known about the influence of systemic chemotherapy on the development of drug resistance at metastatic sites. In this work, we use a hybrid spatial model of tumor response to a DNA damaging drug to study how the development of chemoresistance in micrometastases depends on the drug dosing schedule. We separately consider cell populations that harbor pre-existing resistance to the drug, and those that acquire resistance during the course of treatment. For each of these independent scenarios, we consider one hypothetical cell line that is responsive to metronomic chemotherapy, and another that with high probability cannot be eradicated by a metronomic protocol. Motivated by experimental work on ovarian cancer xenografts, we consider all possible combinations of a one week treatment protocol, repeated for three weeks, and constrained by the total weekly drug dose. Simulations reveal a small number of fractionated-dose protocols that are at least as effective as metronomic therapy in eradicating micrometastases with acquired resistance (weak or strong), while also being at least as effective on those that harbor weakly pre-existing resistant cells. Given the responsiveness of very different theoretical cell lines to these few fractionated-dose protocols, these may represent more effective ways to schedule chemotherapy with the goal of limiting metastatic tumor progression.

Schedule-Dependent Antiangiogenic and Cytotoxic Effects of Chemotherapy on Vascular Endothelial and Retinoblastoma Cells

Current treatment of retinoblastoma involves using the maximum dose of chemotherapy that induces tumor control and is tolerated by patients. The impact of dose and schedule on the cytotoxicity of chemotherapy has not been studied. Our aim was to gain insight into the cytotoxic and antiangiogenic effect of the treatment scheme of chemotherapy used in retinoblastoma by means of different in vitro models and to evaluate potential effects on multi-drug resistance proteins. Two commercial and two patient-derived retinoblastoma cell types and two human vascular endothelial cell types were exposed to increasing concentrations of melphalan or topotecan in a conventional (single exposure) or metronomic (7-day continuous exposure) treatment scheme. The concentration of chemotherapy causing a 50% decrease in cell proliferation (IC50) was determined by MTT and induction of apoptosis was evaluated by flow cytometry. Expression of ABCB1, ABCG2 and ABCC1 after conventional or metronomic treatments was assessed by RT-qPCR. We also evaluated the in vivo response to conventional (0.6 mg/kg once a week for 2 weeks) and metronomic (5 days a week for 2 weeks) topotecan in a retinoblastoma xenograft model. Melphalan and topotecan were cytotoxic to both retinoblastoma and endothelial cells after conventional and metronomic treatments. A significant decrease in the IC50 (median, 13-fold; range: 3–23) was observed following metronomic chemotherapy treatment in retinoblastoma and endothelial cell types compared to conventional treatment (p<0.05). Metronomic topotecan or melphalan significantly inhibited in vitro tube formation in HUVEC and EPC compared to vehicle-treated cells (p<0.05). Both treatment schemes induced apoptosis and/or necrosis in all cell models. No significant difference was observed in the expression of ABCB1, ABCC1 or ABCG2 when comparing cells treated with melphalan or topotecan between treatment schedules at the IC50 or with control cells (p>0.05). In mice, continuous topotecan lead to significantly lower tumor volumes compared to conventional treatment after 14 days of treatment (p<0.05). Continuous exposure to melphalan or topotecan increased the chemosensitivity of retinoblastoma and endothelial cells to both chemotherapy agents with lower IC50 values compared to short-term treatment. These findings were validated in an in vivo model. None of the dosing modalities induced multidrug resistance mechanisms while apoptosis was the mechanism of cell death after both treatment schedules. Metronomic chemotherapy may be a valid option for retinoblastoma treatment allowing reductions of the daily dose.

A Combination Therapy with Baicalein and Taxol Promotes Mitochondria-Mediated Cell Apoptosis: Involving in Akt/β-Catenin Signaling Pathway

Baicalein, a major flavonoid, possesses anticancer and anti-inflammatory activity. The aim of the study is to explore the efficiency of combination therapy with baicalein and taxol, as well as the molecular mechanism on antitumor activity. Human ovarian cancer cells were treated with different concentration of baicalein for 48 h, and cell viability was determined by MTT assay. Baicalein inhibited cell proliferation of ovarian cancer cells, and IC50 value of baicalein in A2780 cells, SKOV3 cells, and OVCAR cells was 46.23, 60.68, and 38.03 μM, respectively. The ovarian cancer cells were treated with 10 μM of baicalein combined with increasing concentration of taxol for 48 h, and the results demonstrated that combination therapy with baicalein and taxol had much higher antitumor effects compared with the monotherapy. The molecular mechanisms involving in combination therapy promoted the caspase-3 activity then leading to cleavage of poly-ADP-ribose polymerase, which increased the cell apoptosis of ovarian cancer cells. Moreover, Z-VAD-FMK treatment partially decreased the baicalein-induced proliferation inhibition in human ovarian cancer cells. Furthermore, baicalein induced apoptosis through activation of the activities of caspase-3,-9, and increased cytoplasmic cytochrome C release. Importantly, baicalein inhibited the growth of A2780 cells by inhibiting Akt/β-catenin signaling pathway. In conclusion, our result revealed that baicalein combinated with taxol at low concentrations could exert synergistic antitumor effects in ovarian cancer cells through mitochondria-mediated cell apoptosis and Akt/β-catenin signaling pathway. Baicalein has a promising potential to be developed as an antitumor compound, and combination therapy of baicalein and taxol exhibits an antitumor potential in clinical therapy for human ovarian cancers.

Thermosensitive hydrogel system assembled by PTX-loaded copolymer nanoparticles for sustained intraperitoneal chemotherapy of peritoneal carcinomatosis

Intraperitoneal (IP) chemotherapy is a preferable treatment option for peritoneal carcinomatosis of malignancies by delivering chemotherapeutic drugs into the abdominal cavity. A persistent major challenge in IP chemotherapy is the need to provide effective drug concentration in the peritoneal cavity for an extended period of time. In the present work, the thermosensitive hydrogel system (PTX/PECT(gel)) assembled by PTX (paclitaxel)-loaded amphiphilic copolymer (PECT, poly (ε-caprolactone-co-1,4,8-trioxa [4.6]spiro-9-undecanone)-poly(ethylene glycol)-poly (ε-caprolactone-co-1,4,8-trioxa [4.6]spiro-9-undecanone)) nanoparticles was developed for sustained IP chemotherapy of peritoneal carcinomatosis model. Cytotoxicity assay indicated that PECT hydrogel was biocompatible with very low cytotoxicity and PTX/PECT(gel) had enhanced cytotoxicity than free PTX. In vivo toxicity study demonstrated the biocompatibility and biosafety of PECT hydrogel as an IP chemotherapy carrier. The fluorescence imaging method was employed to monitor the intraperitoneal degradation of PECT hydrogel by labeling PECT with rhodamine B. PECT hydrogel with the dose of 200μL showed about 8days' retention time and most of the injected hydrogel was located in the intestine. The anti-tumor efficacy study was carried out in mice bearing CT26 intraperitoneal ascites fluid as colorectal peritoneal carcinomatosis model. The result showed that intraperitoneal administration of PTX/PECT(gel) could effectively suppress growth and metastasis of CT26 peritoneal carcinomatosis in vivo, compared with Taxol® group. The pharmacokinetic studies demonstrated that PTX/PECT(gel) could improve the bioavailability of PTX by being formulated in PECT hydrogel. Overall, sustained drug concentration at peritoneal levels in combination with drug in the form of nanoparticle contributes to the enhanced anti-tumor efficacy. Thus, our results suggested that PTX/PECT(gel) may have great potential applications in IP chemotherapy.

Systemic Exposure to Thiopurines and Risk of Relapse in Children With Acute Lymphoblastic Leukemia: A Children's Oncology Group Study

IMPORTANCE

Variability in prescribed doses of 6-mercaptopurine (6MP) and lack of adherence to a 6MP treatment regimen could result in intra-individual variability in systemic exposure to 6MP (measured as erythrocyte thioguanine nucleotide [TGN] levels) in children with acute lymphoblastic leukemia (ALL). The effect on relapse risk of this variability is unknown.

OBJECTIVE

To determine the effect of high intra-individual variability of 6MP systemic exposure on relapse risk in children with ALL.

DESIGN, SETTING, AND PARTICIPANTS

We used a prospective longitudinal design (Children's Oncology Group study [COG-AALL03N1]) to monitor 6MP and disease relapse in 742 children with ALL in ambulatory care settings of 94 participating institutions from May 30, 2005, to September 9, 2011. All participants met the following eligibility criteria: (1) diagnosis of ALL at 21 years or younger; (2) first continuous remission in progress at the time of study entry; (3) receiving self-, parent-, or caregiver-administered oral 6MP during maintenance therapy; and (4) completion of at least 6 months of maintenance therapy at the time of study enrollment. The median patient age at diagnosis was 5 years; 68% were boys; and 43% had National Cancer Institute-based high-risk disease.

MAIN OUTCOMES AND MEASURES

Daily 6MP regimen adherence was measured over 68 716 person-days using an electronic system that recorded the date and time of each 6MP bottle opening; adherence rate was defined as the ratio of days that a 6MP bottle was opened to days thata 6MP bottle was prescribed. Average monthly 6MP dose intensity was measured over 120 439 person-days by dividing the number of 6MP doses actually prescribed by the number of planned protocol doses (75 mg/m2/d). Monthly erythrocyte TGN levels (pmol/8 × 108 erythrocytes) were measured over 6 consecutive months per patient (n = 3944 measurements). Using intra-individual coefficients of variation (CV%), patients were classified as having stable (CV% <85th percentile) vs varying (CV% ≥85th percentile) indices. Median follow-up time was 6.7 years from the time of diagnosis.

RESULTS

Adjusting for clinical prognosticators, we found that patients with 6MP nonadherence (mean adherence rate <95%) were at a 2.7-fold increased risk of relapse (95% CI, 1.3-5.6; P = .01) compared with patients with a mean adherence rate of 95% or greater. Among adherers, high intra-individual variability in TGN levels contributed to increased relapse risk (hazard ratio, 4.4; 95% CI, 1.2-15.7; P = .02). Furthermore, adherers with varying TGN levels had varying 6MP dose intensity (odds ratio [OR], 4.5; 95% CI, 1.5-13.4; P = .01) and 6MP drug interruptions (OR, 10.2; 95% CI, 2.2-48.3; P = .003).

CONCLUSIONS AND RELEVANCE

These findings emphasize the need to maximize 6MP regimen adherence and maintain steady thiopurine exposure to minimize relapse in children with ALL.

The role of ABC transporters in ovarian cancer progression and chemoresistance

Over 80% of ovarian cancer patients develop chemoresistance which results in a lethal course of the disease. A well-established cause of chemoresistance involves the family of ATP-binding cassette transporters, or ABC transporters that transport a wide range of substrates including metabolic products, nutrients, lipids, and drugs across extra- and intra-cellular membranes. Expressions of various ABC transporters, shown to reduce the intracellular accumulation of chemotherapy drugs, are increased following chemotherapy and impact on ovarian cancer survival. Although clinical trials to date using ABC transporter inhibitors have been disappointing, ABC transporter inhibition remains an attractive potential adjuvant to chemotherapy. A greater understanding of their physiological functions and role in ovarian cancer chemoresistance will be important for the development of more effective targeted therapies. This article will review the role of the ABC transporter family in ovarian cancer progression and chemoresistance as well as the clinical attempts used to date to reverse chemoresistance.

Role of ribophorin II in the response to anticancer drugs in gastric cancer cell lines

The identification of prognostic markers and establishing their value as therapeutic targets improves therapeutic efficacy against human cancers. Ribophorin II (RPN2) has been demonstrated to be a prognostic marker of human cancer, including breast and pancreatic cancers. The present study aimed to evaluate RPN2 expression in gastric cancer and to examine the possible correlation between RPN2 expression and the response of cells to clinical anticancer drugs, which has received little research attention at present. The gastric cancer AGS, TMC-1, SNU-1, TMK-1, SCM-1, MKN-45 and KATO III cell lines were used as a model to elucidate the role of RPN2 in the response of cells to six common chemotherapeutic agents, comprising oxaliplatin, irinotecan, doxorubicin, docetaxel, cisplatin and 5-fluorouricil. The functional role of RPN2 was assessed by silencing RPN2 using small interfering RNA (siRNA), and the cytotoxicity was determined by an MTS assay and analysis of apoptosis. Molecular events were evaluated by western blotting. All the anticancer drugs were found to exert a concentration-dependent decrease on the cell survival rate of each of the cell lines tested, although the RPN2 levels in the various cell lines were not directly correlated with responsiveness to clinical anticancer drugs, based on the calculated IC₅₀ values. siRNA-mediated RPN2 downregulation enhanced cisplatin-induced apoptosis in AGS cells, but did not markedly decrease the cell survival rates of these cells in response to the tested drugs. Furthermore, RPN2 silencing in MKN-45 cells resulted in no additional increase in the cisplatin-induced apoptosis and survival rates. It was also found that RPN2 depletion increased anticancer drug-mediated cytotoxicity in gastric cancer cell lines. However, the predictive value of RPN2 expression in cancer therapy is questionable in gastric cancer models.

Effect of a high-fat diet on the hepatic expression of nuclear receptors and their target genes: relevance to drug disposition

More than 1·4 billion individuals are overweight or obese worldwide. While complications often require therapeutic intervention, data regarding the impact of obesity on drug disposition are scarce. As the influence of diet-induced obesity on drug transport and metabolic pathways is currently unclear, the objective of the present study was to investigate the effect of high fat feeding for 13 weeks in female Sprague-Dawley rats on the hepatic expression of the nuclear receptors pregnane X receptor (PXR), constitutive androstane receptor (CAR), liver X receptor (LXR) and farnesoid X receptor (FXR) and several of their target genes. We hypothesised that high fat feeding would alter the gene expression of major hepatic transporters through a dysregulation of the expression of the nuclear receptors. The results demonstrated that, along with a significant increase in body fat and weight, a high-fat diet (HFD) induced a significant 2-fold increase in the expression of PXR as well as a 2-, 5- and 2·5-fold increase in the hepatic expression of the PXR target genes Abcc2, Abcb1a and Cyp3a2, respectively (P< 0·05). The expression levels of FXR were significantly increased in rats fed a HFD in addition to the increase in the expression levels of FXR target genes Abcb11 and Abcb4. The expression levels of both LXRα and LXRβ were slightly but significantly increased in rats fed a HFD, and the expression levels of their target genes Abca1 and Abcg5, but not Abcg8, were significantly increased. The expression of the nuclear receptor CAR was not significantly altered between the groups. This suggests that a HFD may induce changes in the hepatobiliary transport and metabolism of endogenous and exogenous compounds.

The modulation of ABC transporter-mediated multidrug resistance in cancer: a review of the past decade

ATP-binding cassette (ABC) transporters represent one of the largest and oldest families of membrane proteins in all extant phyla from prokaryotes to humans, which couple the energy derived from ATP hydrolysis essentially to translocate, among various substrates, toxic compounds across the membrane. The fundamental functions of these multiple transporter proteins include: (1) conserved mechanisms related to nutrition and pathogenesis in bacteria, (2) spore formation in fungi, and (3) signal transduction, protein secretion and antigen presentation in eukaryotes. Moreover, one of the major causes of multidrug resistance (MDR) and chemotherapeutic failure in cancer therapy is believed to be the ABC transporter-mediated active efflux of a multitude of structurally and mechanistically distinct cytotoxic compounds across membranes. It has been postulated that ABC transporter inhibitors known as chemosensitizers may be used in combination with standard chemotherapeutic agents to enhance their therapeutic efficacy. The current paper reviews the advance in the past decade in this important domain of cancer chemoresistance and summarizes the development of new compounds and the re-evaluation of compounds originally designed for other targets as transport inhibitors of ATP-dependent drug efflux pumps.

The S100A4 D10V polymorphism is related to cell migration ability but not drug resistance in gastric cancer cells

Upregulation of the metastasis-promoting S100A4 protein has been linked to tumor migration and invasion, and clinical studies have demonstrated that significant expression of S100A4 in primary tumors is indicative of poor prognosis. However, the involvement of S100A4 in the drug responsiveness of gastric cancer remains unclear. In the present study, we used gastric cancer cell lines as a model to investigate the involvement of S100A4 in drug responsiveness. We overexpressed S100A4 in AGS and SCM-1 cells, which are characterized by relatively low-level expression of endogenous S100A4, and found that this significantly enhanced cell migration but did not affect cell survival in the presence of six common anticancer drugs. Moreover, in vitro cell proliferation was unchanged. Using RNA interference, we suppressed S100A4 expression in MKN-45 and TMK-1 cells (which are characterized by high-level expression of endogenous S100A4), and found that knockdown of S100A4 markedly attenuated cell motility but did not affect cell survival in the presence of six common anticancer drugs. Further study revealed that a single nucleotide polymorphism (SNP) of S100A4 (rs1803245; c.29A>T), which substitutes an Asp residue with Val (D10V), is localized within the conserved binding surface for Annexin II. Cells overexpressing S100A4^D10V showed a significant reduction in cell migration ability, but no change in cell survival, upon anticancer drug treatment. Taken together, our novel results indicate that the expression level of S100A4 does not significantly affect cell survival following anticancer drug treatment. Thus, depending on the cell context, the metastasis-promoting effects of S100A4 may not be positively correlated with anticancer drug resistance in the clinic.

Aligned and suspended fiber force probes for drug testing at single cell resolution

The role of physical forces in disease onset and progression is widely accepted and this knowledge presents an alternative route to investigating disease models. Recently, numerous force measurement techniques have been developed to probe single and multi-cell behavior. While these methods have yielded fundamental insights, they are yet unable to capture the fibrous extra-cellular matrix biophysical interactions, involving parameters of curvature, structural stiffness (N m(-1)), alignment and hierarchy, which have been shown to play key roles in disease and developmental biology. Using a highly aggressive glioma model (DBTRG-05MG), we present a platform technology to quantify single cell force modulation (both inside-out and outside-in) with and without the presence of a cytoskeleton altering drug (cytochalasin D) using suspended and aligned fiber networks (nanonets) beginning to represent the aligned glioma environment. The nanonets fused in crisscross patterns were manufactured using the non-electrospinning spinneret based tunable engineering parameters technique. We demonstrate the ability to measure contractile single cell forces exerted by glioma cells attached to and migrating along the fiber axis (inside-out). This is followed by a study of force response of glioma cells attached to two parallel fibers using a probe deflecting the leading fiber (outside-in). The forces are calculated using beam deflection within the elastic limit. Our data shows that cytochalasin D compromises the spreading area of single glioma cells, eventually decreasing their 'inside-out' contractile forces, and 'outside-in' force response to external strain. Most notably, for the first time, we demonstrate the feasibility of using physiologically relevant aligned fiber networks as ultra-sensitive force (∼nanoNewtons) probes for investigating drug response and efficacy in disease models at the single cell resolution.

Metronomics: towards personalized chemotherapy?

Since its inception in 2000, metronomic chemotherapy has undergone major advances as an antiangiogenic therapy. The discovery of the pro-immune properties of chemotherapy and its direct effects on cancer cells has established the intrinsic multitargeted nature of this therapeutic approach. The past 10 years have seen a marked rise in clinical trials of metronomic chemotherapy, and it is increasingly combined in the clinic with conventional treatments, such as maximum-tolerated dose chemotherapy and radiotherapy, as well as with novel therapeutic strategies, such as drug repositioning, targeted agents and immunotherapy. We review the latest advances in understanding the complex mechanisms of action of metronomic chemotherapy, and the recently identified factors associated with disease resistance. We comprehensively discuss the latest clinical data obtained from studies performed in both adult and paediatric populations, and highlight ongoing clinical trials. In this Review, we foresee the future developments of metronomic chemotherapy and specifically its potential role in the era of personalized medicine.

PD173074, a selective FGFR inhibitor, reverses MRP7 (ABCC10)-mediated MDR

Multidrug resistance protein 7 (MRP7, ABCC10) is a recently identified member of the ATP-binding cassette (ABC) transporter family, which adequately confers resistance to a diverse group of antineoplastic agents, including taxanes, vinca alkaloids and nucleoside analogs among others. Clinical studies indicate an increased MRP7 expression in non-small cell lung carcinomas (NSCLC) compared to a normal healthy lung tissue. Recent studies revealed increased paclitaxel sensitivity in the Mrp7^−/− mouse model compared to their wild-type counterparts. This demonstrates that MRP7 is a key contributor in developing drug resistance. Recently our group reported that PD173074, a specific fibroblast growth factor receptor (FGFR) inhibitor, could significantly reverse P-glycoprotein-mediated MDR. However, whether PD173074 can interact with and inhibit other MRP members is unknown. In the present study, we investigated the ability of PD173074 to reverse MRP7-mediated MDR. We found that PD173074, at non-toxic concentration, could significantly increase the cellular sensitivity to MRP7 substrates. Mechanistic studies indicated that PD173074 (1 μmol/L) significantly increased the intracellular accumulation and in-turn decreased the efflux of paclitaxel by inhibiting the transport activity without altering expression levels of the MRP7 protein, thereby representing a promising therapeutic agent in the clinical treatment of chemoresistant cancer patients.

Carboxymethylcellulose-based and docetaxel-loaded nanoparticles circumvent P-glycoprotein-mediated multidrug resistance

Taxanes are a class of anticancer agents with a broad spectrum and have been widely used to treat a variety of cancer. However, its long-term use has been hampered by accumulating toxicity and development of drug resistance. The most extensively reported mechanism of resistance is the overexpression of P-glycoprotein (Pgp). We have developed a PEGylated carboxymethylcellulose conjugate of docetaxel (Cellax), which condenses into ∼120 nm nanoparticles. Here we demonstrated that Cellax therapy did not upregulate Pgp expression in MDA-MB-231 and EMT-6 breast tumor cells, whereas a significant increase in Pgp expression was measured with native docetaxel (DTX) treatment. Treatment with DTX led to 4-7-fold higher Pgp mRNA expression and 2-fold higher Pgp protein expression compared with Cellax treatment in the in vitro and in vivo system, respectively. Cellax also exhibited significantly increased efficacy compared with that of DTX in a taxane-resistant breast tumor model. Against the highly Pgp expressing EMT6/AR1 cells, Cellax exhibited a 6.5 times lower IC50 compared with that of native DTX, and in the in vivo model, Cellax exhibited 90% tumor growth inhibition, while native DTX had no significant antitumor activity.

The impact of sustained and intermittent docetaxel chemotherapy regimens on cognition and neural morphology in healthy mice

RATIONALE

A subset of cancer survivors demonstrates impairments in cognition long after chemotherapy completion. At present, it is unclear whether these changes are due to direct neurotoxic effects of chemotherapy.

OBJECTIVES

This study examined the impact of variable docetaxel (DTX) chemotherapy dosing on brain DTX exposure via analyses of neural morphology and changes in cognition.

METHODS

Male CD-1 mice were treated with DTX either intermittently (8 mg/kg i.p. weekly) or via a sustained delivery system (DTX-PoLigel), which continuously releases DTX. Both groups received total DTX doses of 32 mg/kg. Mice were assessed on the novel object recognition (NOR) task and the Morris water maze (MWM) shortly after treatment.

RESULTS

Post-treatment behavioral testing demonstrated impaired NOR in mice treated with either dosing schedule relative to controls. No differences were observed between groups in MWM training and initial testing, though control mice performed better than chance while DTX-treated mice did not. Appreciable amounts of DTX were found in the brain after both treatment regimens. DTX treatment did not significantly increase levels of apoptosis within the CNS. However, some elevation in neural autophagy was observed following DTX treatment. Analysis of astrocytic activation demonstrated that intermittent DTX treatment resulted in an elevation of GFAP-positive astrocytes for 48 h after administration. Sustained chemotherapy demonstrated prolonged but lower levels of astrocyte activation over 9 days following implantation.

CONCLUSIONS

DTX treatment induced cognitive impairment shortly after treatment. Further, these findings suggest an association between DTX dosing, neurotoxicity, and cognitive effects.

Effect of small-molecule modification on single-cell pharmacokinetics of PARP inhibitors

The heterogeneous delivery of drugs in tumors is an established process contributing to variability in treatment outcome. Despite the general acceptance of variable delivery, the study of the underlying causes is challenging, given the complex tumor microenvironment including intra- and intertumor heterogeneity. The difficulty in studying this distribution is even more significant for small-molecule drugs where radiolabeled compounds or mass spectrometry detection lack the spatial and temporal resolution required to quantify the kinetics of drug distribution in vivo. In this work, we take advantage of the synthesis of fluorescent drug conjugates that retain their target binding but are designed with different physiochemical and thus pharmacokinetic properties. Using these probes, we followed the drug distribution in cell culture and tumor xenografts with temporal resolution of seconds and subcellular spatial resolution. These measurements, including in vivo permeability of small-molecule drugs, can be used directly in predictive pharmacokinetic models for the design of therapeutics and companion imaging agents as demonstrated by a finite element model.

Recent advances regarding the role of ABC subfamily C member 10 (ABCC10) in the efflux of antitumor drugs

ABCC10, also known as multidrug-resistant protein 7 (MRP7), is the tenth member of the C subfamily of the ATP-binding cassette (ABC) superfamily. ABCC10 mediates multidrug resistance (MDR) in cancer cells by preventing the intracellular accumulation of certain antitumor drugs. The ABCC10 transporter is a 171-kDa protein that is localized on the basolateral cell membrane. ABCC10 is a broad-specificity transporter of xenobiotics, including antitumor drugs, such as taxanes, epothilone B, vinca alkaloids, and cytarabine, as well as modulators of the estrogen pathway, such as tamoxifen. In recent years, ABCC10 inhibitors, including cepharanthine, lapatinib, erlotinib, nilotinib, imatinib, sildenafil, and vardenafil, have been reported to overcome ABCC10-mediated MDR. This review discusses some recent and clinically relevant aspects of the ABCC10 drug efflux transporter from the perspective of current chemotherapy, particularly its inhibition by tyrosine kinase inhibitors and phosphodiesterase type 5 inhibitors.

Continuous intraperitoneal carboplatin delivery for the treatment of late-stage ovarian cancer

The rate of failure of chemotherapy treatment in ovarian cancer remains high, resulting in a low 5-year survival rate of 20-40% in patients that present with advanced-stage disease. Treatment-free periods between cycles of chemotherapy may contribute to accelerated tumor cell proliferation and decreased treatment response. The elimination of treatment-free breaks has been deemed beneficial in the context of cell-cycle-specific agents. The potential benefit of this approach for non-cell-cycle-specific agents has not yet been elucidated. The present study is the first to address this issue by investigating the impact of continuous versus intermittent intraperitoneal administration of carboplatin over a 14 day period to SCID mice bearing SKOV-3 ovarian cancer xenografts. Immunostaining of tumor sections was employed to quantify tumor proliferation, angiogenesis, and apoptosis using Ki-67, CD-31, caspase-3 (CASP3), and terminal deoxytransferase-mediated dUTP nick-end labeling (TUNEL). Continuous ip administration of carboplatin resulted in greater tumor growth inhibition than intermittent therapy (p < 0.05). Significantly greater tumor cell apoptosis and less cell proliferation and angiogenesis were measured in tumors of mice treated with continuous carboplatin as compared to both intermittent and control groups. These results indicate that continuous local administration may be a promising approach to improve the effectiveness of platinum-based chemotherapy regimens.

Influence of the duration of intravenous drug administration on tumor uptake

Enhancing tumor uptake of anticancer drugs is an important therapeutic goal, because insufficient drug accumulation is now considered to be an important reason for unresponsiveness or resistance to antitumor therapy. Based on a mechanistic tumor uptake model describing tumor exposure to molecules of different molecular size after bolus administration, we have investigated the influence of the duration of intravenous administration on tumor uptake. The model integrates empirical relationships between molecular size and drug disposition (capillary permeability, interstitial diffusivity, available volume fraction, and plasma clearance), together with a compartmental pharmacokinetics model and a drug/target binding model. Numerical simulations were performed using this model for protracted intravenous drug infusion, a common mode of administration of anticancer drugs. The impact of mode of administration on tumor uptake is described for a large range of molecules of different molecular size. Evaluation was performed not only for the maximal drug concentration achieved in the tumor, but also for the dynamic profile of drug concentration. It is shown that despite a lower maximal uptake for a given dose, infusion allows for a prolonged exposure of tumor tissues to both small- and large-sized molecules. Moreover, infusion may allow higher doses to be administered by reducing Cmax-linked toxicity, thereby achieving a similar maximal uptake compared to bolus administration.