Influx and efflux transport as determinants of melphalan cytotoxicity: Resistance to melphalan in MDR1 overexpressing tumor cell lines. Biochem Pharmacol. 2009;78:45-53. [PMID: 19447222 DOI: 10.1016/j.bcp.2009.03.026]

Gene Delivery into T-Cells Using Ternary Complexes of DNA, Lipofectamine, and Carboxy-Terminal Phenylalanine-Modified Dendrimers

T-cells play critical roles in various immune reactions, and genetically engineered T-cells have attracted attention for the treatment of cancer and autoimmune diseases. Previously, it is shown that a polyamidoamine dendrimer of generation 4 (G4), modified with 1,2-cyclohexanedicarboxylic anhydride (CHex) and phenylalanine (Phe) (G4-CHex-Phe), is useful for delivery into T-cells and their subsets. In this study, an efficient non-viral gene delivery system is constructed using this dendrimer. Ternary complexes are prepared using different ratios of plasmid DNA, Lipofectamine, and G4-CHex-Phe. A carboxy-terminal dendrimer lacking Phe (G3.5) is used for comparison. These complexes are characterized using agarose gel electrophoresis, dynamic light scattering, and ζpotential measurements. In Jurkat cells, the ternary complex with G4-CHex-Phe at a P/COOH ratio of 1/5 shows higher transfection activity than other complexes, such as binary and ternary complexes with G3.5, without any significant cytotoxicity. The transfection efficiency of the G4-CHex-Phe ternary complexes decreases considerably in the presence of free G4-CHex-Phe and upon altering the complex preparation method. These results suggest that G4-CHex-Phe promotes the cellular internalization of the complexes, which is useful for gene delivery into T-cells.

T Cell-Association of Carboxy-Terminal Dendrimers with Different Bound Numbers of Phenylalanine and Their Application to Drug Delivery

T cells play important roles in various immune reactions, and their activation is necessary for cancer immunotherapy. Previously, we showed that polyamidoamine (PAMAM) dendrimers modified with 1,2-cyclohexanedicarboxylic acid (CHex) and phenylalanine (Phe) underwent effective uptake by various immune cells, including T cells and their subsets. In this study, we synthesized various carboxy-terminal dendrimers modified with different bound numbers of Phe and investigated the association of these dendrimers with T cells to evaluate the influence of terminal Phe density. Carboxy-terminal dendrimers conjugating Phe at more than half of the termini exhibited a higher association with T cells and other immune cells. The carboxy-terminal Phe-modified dendrimers at 75% Phe density tended to exhibit the highest association with T cells and other immune cells, which was related to their association with liposomes. A model drug, protoporphyrin IX (PpIX), was encapsulated into carboxy-terminal Phe-modified dendrimers, which were then used for drug delivery into T cells. Our results suggest the carboxy-terminal Phe-modified dendrimers are useful for delivery into T cells.

Solid-State Formation of a Potential Melphalan Delivery Nanosystem Based on β-Cyclodextrin and Silver Nanoparticles

Melphalan (Mel) is an antineoplastic widely used in cancer and other diseases. Its low solubility, rapid hydrolysis, and non-specificity limit its therapeutic performance. To overcome these disadvantages, Mel was included in β-cyclodextrin (βCD), which is a macromolecule that increases its aqueous solubility and stability, among other properties. Additionally, the βCD-Mel complex has been used as a substrate to deposit silver nanoparticles (AgNPs) through magnetron sputtering, forming the βCD-Mel-AgNPs crystalline system. Different techniques showed that the complex (stoichiometric ratio 1:1) has a loading capacity of 27%, an association constant of 625 M^-1, and a degree of solubilization of 0.034. Added to this, Mel is partially included, exposing the NH₂ and COOH groups that stabilize AgNPs in the solid state, with an average size of 15 ± 3 nm. Its dissolution results in a colloidal solution of AgNPs covered by multiple layers of the βCD-Mel complex, with a hydrodynamic diameter of 116 nm, a PDI of 0.4, and a surface charge of 19 mV. The in vitro permeability assays show that the effective permeability of Mel increased using βCD and AgNPs. This novel nanosystem based on βCD and AgNPs is a promising candidate as a Mel nanocarrier for cancer therapy.

Drug and Solute Transporters in Mediating Resistance to Novel Therapeutics in Multiple Myeloma

Multiple myeloma remains an incurable malignancy of plasma cells. Novel therapies, notably proteasome inhibitors and immunomodulatory drugs, have improved the survival of multiple myeloma patients; however, patients either present with, or develop resistance to, these therapies. Resistance to traditional chemotherapeutic agents can be caused by cellular drug efflux via adenosine triphosphate (ATP)-binding cassette (ABC) transporters, but it is still not clear whether these transporters mediate resistance to proteasome inhibitors and immunomodulatory drugs in multiple myeloma. Solute carrier (SLC) transporters also play a role in cancer drug resistance due to changes in cell homeostasis caused by their abnormal expression and changes in the solutes they transport. In this review, we evaluate resistance to novel therapies used to treat multiple myeloma, as mediated by drug and solute transporters.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Multi-omics tumor profiling technologies to develop precision medicine in multiple myeloma

Multiple myeloma (MM), the second most common hematologic cancer, is caused by accumulation of aberrant plasma cells in the bone marrow. Its molecular causes are not fully understood and its great heterogeneity among patients complicates therapeutic decision-making. In the past decades, development of new therapies and drugs have significantly improved survival of MM patients. However, resistance to drugs and relapse remain the most common causes of mortality and are the major challenges to overcome. The advent of high throughput omics technologies capable of analyzing big amount of clinical and biological data has changed the way to diagnose and treat MM. Integration of omics data (gene mutations, gene expression, epigenetic information, and protein and metabolite levels) with clinical histories of thousands of patients allows to build scores to stratify the risk at diagnosis and predict the response to treatment, helping clinicians to make better educated decisions for each particular case. There is no doubt that the future of MM treatment relies on personalized therapies based on predictive models built from omics studies. This review summarizes the current treatments and the use of omics technologies in MM, and their importance in the implementation of personalized medicine.

Correlation of Technical and Adjunctive Factors with Quantitative Tumor Reduction in Children Undergoing Selective Ophthalmic Artery Infusion Chemotherapy for Retinoblastoma

BACKGROUND AND PURPOSE

Selective ophthalmic artery infusion chemotherapy has improved ocular outcomes in children with retinoblastoma. Our aim was to correlate quantitative tumor reduction and dichotomous therapeutic response with technical and adjunctive factors during selective ophthalmic artery infusion chemotherapy for retinoblastoma. An understanding of such factors may improve therapeutic efficacy.

MATERIALS AND METHODS

All patients with retinoblastoma treated by selective ophthalmic artery infusion chemotherapy at a single center during a 9-year period were reviewed. Only first-cycle treatments for previously untreated eyes were studied. Adjunctive factors (intra-arterial verapamil, intranasal oxymetazoline external carotid balloon occlusion) and technical factors (chemotherapy infusion time, fluoroscopy time) were documented by medical record review. Quantitative tumor reduction was determined by blinded comparison of retinal imaging acquired during examination under anesthesia before and 3-4 weeks after treatment. The dichotomous therapeutic response was classified according to quantitative tumor reduction as satisfactory (≥ 50%) or poor (<50%).

RESULTS

Twenty-one eyes met the inclusion criteria. Patients ranged from 2 to 59 months of age. Adjuncts included intra-arterial verapamil in 15, intranasal oxymetazoline in 14, and external carotid balloon occlusion in 14. Quantitative tumor reduction ranged from 15% to 95%. Six showed poor dichotomous therapeutic response. A satisfactory dichotomous therapeutic response was correlated with intra-arterial verapamil (P = .03) in the aggregate cohort and in a subgroup undergoing treatment with single-agent melphalan at a dose of <5 mg (P = .02). In the latter, higher average quantitative tumor reduction correlated with intra-arterial verapamil (P < .01).

CONCLUSIONS

Intra-arterial verapamil during selective ophthalmic artery infusion chemotherapy is correlated with an improved therapeutic response, particularly when treating with lower doses of single-agent melphalan.

Development of a method for clinical pharmacokinetic testing to allow for targeted Melphalan dosing in multiple myeloma patients undergoing autologous transplant

AIMS

High dose melphalan (HDM) and autologous stem cell transplant (ASCT) is standard of care for multiple myeloma (MM), but there is significant variability in melphalan exposure (area under the plasma drug concentration-time curve, AUC) when using body surface area-based dosing. Our aim was to establish a method of pharmacokinetic (PK) testing for real-time melphalan dose adjustments.

METHODS

We performed a prospective PK study of melphalan 140 or 200 mg/m2 in MM patients undergoing ASCT. Twenty MM patients were administered HDM on days -2 and - 1, with PK sampling at 8-10 time points. PK testing was performed on day -2 in all patients, and on day -1 in 5 patients.

RESULTS

Less than 20% interpatient variation in the day -2 and - 1 AUC was observed. The day -2 range in AUC (4.95-11.28 mg h/L) confirmed significant interpatient variability. The hypothetical total dose ranged from 133-302 mg/m2 to achieve the total median AUC. A 4-time point AUC (0, 30, 150 and 240 min) highly correlated with the AUC from the 8-time point schedule. A higher AUC correlated with increased risk of febrile neutropenia (P = .05).

CONCLUSION

Here we outline the methods to establish novel melphalan dosing using PK testing in MM patients undergoing ASCT to target a desired melphalan AUC.

Synthesis, Characterization, and In Vitro Studies of an Reactive Oxygen Species (ROS)-Responsive Methoxy Polyethylene Glycol-Thioketal-Melphalan Prodrug for Glioblastoma Treatment

Glioblastoma (GBM) is the most frequent and aggressive primary tumor of the brain and averages a life expectancy in diagnosed patients of only 15 months. Hence, more effective therapies against this malignancy are urgently needed. Several diseases, including cancer, are featured by high levels of reactive oxygen species (ROS), which are possible GBM hallmarks to target or benefit from. Therefore, the covalent linkage of drugs to ROS-responsive molecules can be exploited aiming for a selective drug release within relevant pathological environments. In this work, we designed a new ROS-responsive prodrug by using Melphalan (MPH) covalently coupled with methoxy polyethylene glycol (mPEG) through a ROS-cleavable group thioketal (TK), demonstrating the capacity to self-assembly into nanosized micelles. Full chemical-physical characterization was conducted on the polymeric-prodrug and proper controls, along with in vitro cytotoxicity assayed on different GBM cell lines and “healthy” astrocyte cells confirming the absence of any cytotoxicity of the prodrug on healthy cells (i.e. astrocytes). These results were compared with the non-ROS responsive counterpart, underlining the anti-tumoral activity of ROS-responsive compared to the non-ROS-responsive prodrug on GBM cells expressing high levels of ROS. On the other hand, the combination treatment with this ROS-responsive prodrug and X-ray irradiation on human GBM cells resulted in an increase of the antitumoral effect, and this might be connected to radiotherapy. Hence, these results represent a starting point for a rationale design of innovative and tailored ROS-responsive prodrugs to be used in GBM therapy and in combination with radiotherapy.

Pretransplant hemoglobin and creatinine clearance correlate with treatment-free survival after autologous stem cell transplantation for multiple myeloma

Melphalan is given at a dose of 200 mg/m² (Mel200) prior to ASCT for multiple myeloma (MM). Pharmacokinetic (PK) studies show a high degree of interpatient variability. We aimed to test the impact of clinical factors previously shown to affect melphalan PK such as hemoglobin (Hgb), fat-free mass (FFM), and creatinine clearance (CrCl) on outcomes. Median Hgb (from day -2 to -1) and FFM were grouped as low or high relative to their sample medians, and CrCl was divided into ≥60 or <60 ml/min. In 133 MM patients, median TFS (defined as time from ASCT to initiation of next subsequent line of therapy or death) was longer in patients with lower Hgb (35 vs. 16 months, p = 0.02). Patients with both lower Hgb and CrCl experienced longer TFS compared to those with higher Hgb and CrCl (35 vs. 13 months, p = 0.03). In multivariate analysis, lower hemoglobin, lower CrCl, and a combined low hemoglobin and CrCl were strongly associated with improved TFS. Patients with a lower hemoglobin or creatinine clearance experienced significantly more toxicity. We show for the first time that Hgb and CrCl are important predictors of outcomes after Mel200. PK-directed melphalan dosing may be beneficial in achieving optimal outcomes.

Antioxidant Defenses Confer Resistance to High Dose Melphalan in Multiple Myeloma Cells

Background: Multiple myeloma (MM) is the second most common hematological cancer after lymphoma. It is characterized by the accumulation of clonal malignant plasma cells within the bone marrow. The development of drug resistance remains a major problem for effective treatment of MM. Understand the mechanisms underlying drug resistance in MM is a focal point to improve MM treatment. Methods: In the current study, we analyzed further the role of redox imbalance induction in melphalan-induced toxicity both in human myeloma cell lines (HMCLs) and primary myeloma cells from patients. Results: We developed an in-vitro model of short-term resistance to high-dose melphalan and identified that pretreatment with physiological concentration of GSH protects HMCLs from melphalan-induced cell cycle arrest and cytotoxicity. We validated these results using primary MM cells from patients co-cultured with their bone marrow microenvironment. GSH did not affect the ability of melphalan to induce DNA damages in MM cells. Interestingly, melphalan induced reactive oxygen species, a significant decrease in GSH concentration, protein and lipd oxydation together with NRF2 (NF-E2-related factor 2) pathway activation. Conclusions: Our data demonstrate that antioxidant defenses confers resistance to high dose melphalan in MM cells, supporting that redox status in MM cells could be determinant for patients’ response to melphalan.

Proteometabolomics of Melphalan Resistance in Multiple Myeloma

Drug resistance remains a critical problem for the treatment of multiple myeloma (MM), which can serve as a specific example for a highly prevalent unmet medical need across almost all cancer types. In MM, the therapeutic arsenal has expanded and diversified, yet we still lack in-depth molecular understanding of drug mechanisms of action and cellular pathways to therapeutic escape. For those reasons, preclinical models of drug resistance are developed and characterized using different approaches to gain insights into tumor biology and elucidate mechanisms of drug resistance. For MM, numerous drugs are used for treatment, including conventional chemotherapies (e.g., melphalan or L-phenylalanine nitrogen mustard), proteasome inhibitors (e.g., Bortezomib), and immunomodulators (e.g., Lenalidomide). These agents have diverse effects on the myeloma cells, and several mechanisms of drug resistance have been previously described. The disparity of these mechanisms and the complexity of these biological processes lead to the formation of complicated hypotheses that require omics approaches for efficient and effective analysis of model systems that can then be interpreted for patient benefit. Here, we describe the combination of metabolomics and proteomics to assess melphalan resistance in MM by examining three specific areas: drug metabolism, modulation of endogenous metabolites to assist in therapeutic escape, and changes in protein activity gauged by ATP probe uptake.

Imaging Melphalan Therapy Response in Preclinical Extramedullary Multiple Myeloma with 18F-FDOPA and 18F-FDG PET

Multiple myeloma (MM) is a debilitating neoplasm of terminally differentiated plasma B cells that resulted in over 13,000 deaths in 2017 alone. Combination therapies involving melphalan, a small-molecule DNA alkylating agent, are commonly prescribed to patients with relapsed or refractory MM, necessitating the stratification of responding patients to minimize toxicities and improve quality of life. Here, we evaluated the use of 3,4-dihydroxy-6-18F-fluoro-l-phenylalanine (18F-FDOPA), a clinically available PET radiotracer with specificity to the L-type amino acid transporter 1 (LAT1), which also mediates melphalan uptake, for imaging melphalan therapy response in a preclinical immunocompetent model of MM. Methods: C57BL/KaLwRij mice were implanted subcutaneously with unilateral murine green fluorescent protein-expressing 5TGM1 tumors and divided into 3 independent groups: untreated, treated beginning week 2 after tumor implantation, and treated beginning week 3 after tumor implantation. The untreated and week 2 treated groups were imaged with preclinical MRI and dynamic 18F-FDG and 18F-FDOPA PET/CT at week 4 on separate, contiguous days, whereas the week 3 treated group was longitudinally imaged weekly for 3 wk. Metabolic tumor volume, total lesion avidity, SUVmax, and total uptake were calculated for both tracers. Immunohistochemistry was performed on representative tissue from all groups for LAT1 and glucose transporter 1 (GLUT1) expression. Results: Melphalan therapy induced a statistically significant reduction in lesion avidity and uptake for both 18F-FDG and 18F-FDOPA. There was no visible effect on GLUT1 expression, but LAT1 density increased in the week 2 treated group. Longitudinal imaging of the week 3 treated group showed variable changes in 18F-FDG and 18F-FDOPA uptake, with an increase in 18F-FDOPA lesion avidity in the second week relative to baseline. LAT1 and GLUT1 surface density in the untreated and week 3 treated groups were qualitatively similar. Conclusion:18F-FDOPA PET/CT complemented 18F-FDG PET/CT in imaging melphalan therapy response in preclinical extramedullary MM. 18F-FDOPA uptake was linked to LAT1 expression and melphalan response, with longitudinal imaging suggesting stabilization of LAT1 levels and melphalan tumor cytotoxicity. Future work will explore additional MM cell lines with heterogeneous LAT1 expression and response to melphalan therapy.

Selection and characterization of a human ovarian cancer cell line resistant to auranofin

The anti-arthritic drug auranofin exerts also potent antitumour activity in in vitro and in vivo models, whose mechanisms are not yet well defined. From an auranofin-sensitive human ovarian cancer cell line A2780, a highly resistant (>20-fold) subline (A2780/AF-R) was developed and characterized. Marked reduction of gold accumulation occurred in auranofin-resistant A2780 cells. Also, moderately higher thioredoxin reductase activity in A2780/AF-R cells was observed while no changes in intracellular glutathione content occurred. Resistance to auranofin was associated with a low level of cross-resistance to some investigational gold compounds as well as to oxaliplatin and other anticancer drugs with different mode of action (i.e. melphalan, vinblastine, doxorubicin, etoposide, and paclitaxel). Reduced gold accumulation was associated to substantial gene expression changes in various influx (e.g. SLC22A1, SLC47A1, SLCO1B1) and efflux (e.g. ABCB1, ABCC2, ABCC3) transporters. The expression levels of selected proteins (i.e. SLC22A1, SLC47A1, P-gp) were also changed accordingly. These data provide evidence that multiple drug transporters may act as mediators of transport of auranofin and other gold compounds in cancer cells. Further investigation into the molecular mechanisms mediating transport of auranofin and new gold complexes in view of their potential clinical application in the treatment of cancer is warranted.

Associations of High-Dose Melphalan Pharmacokinetics and Outcomes in the Setting of a Randomized Cryotherapy Trial

High-dose melphalan followed by autologous stem cell transplantation remains the standard of care for eligible patients with multiple myeloma, but disease response and toxicity, including severe mucositis, varies among patients. Our randomized trial investigated duration of cryotherapy (2 and 6 h) for reduction of mucositis prevalence and severity and explored factors associated with variability in pharmacokinetics and outcomes from melphalan therapy. The results demonstrate that 2-h is at least as effective as 6-h cryotherapy in decreasing severe mucositis. From a population pharmacokinetic model, we identified that fat-free mass, hematocrit, and creatinine clearance were significant covariates, as reported previously. Furthermore, we observed the rs4240803 SLC7A5 polymorphism was significantly associated with pharmacokinetic variability, and pharmacokinetics was associated with both mucositis and neutropenia. However, melphalan exposure was not associated with progression-free or overall survival in our dataset. These findings contribute to ongoing efforts to personalize melphalan dosing in transplant patients.

Novel therapeutic approaches targeting L-type amino acid transporters for cancer treatment

L-type amino acid transporters (LATs) mainly assist the uptake of neutral amino acids into cells. Four LATs (LAT1, LAT2, LAT3 and LAT4) have so far been identified. LAT1 (SLC7A5) has been attracting much attention in the field of cancer research since it is commonly up-regulated in various cancers. Basic research has made it increasingly clear that LAT1 plays a predominant role in malignancy. The functional significance of LAT1 in cancer and the potential therapeutic application of the features of LAT1 to cancer management are described in this review.

Assessment of Amino Acid/Drug Transporters for Renal Transport of [18F]Fluciclovine (anti-[18F]FACBC) in Vitro

[¹⁸F]Fluciclovine (trans-1-amino-3-[¹⁸F]fluorocyclobutanecarboxylic acid; anti-[¹⁸F]FACBC), a positron emission tomography tracer used for the diagnosis of recurrent prostate cancer, is transported via amino acid transporters (AATs) with high affinity (K_m: 97-230 μM). However, the mechanism underlying urinary excretion is unknown. In this study, we investigated the involvement of AATs and drug transporters in renal [¹⁸F]fluciclovine reuptake. [¹⁴C]Fluciclovine (trans-1-amino-3-fluoro[1-¹⁴C]cyclobutanecarboxylic acid) was used because of its long half-life. The involvement of AATs in [¹⁴C]fluciclovine transport was measured by apical-to-basal transport using an LLC-PK1 monolayer as model for renal proximal tubules. The contribution of drug transporters herein was assessed using vesicles/cells expressing the drug transporters P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), multidrug resistance-associated protein 4 (MRP4), organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3) , organic cation transporter 2 (OCT2), organic anion transporting polypeptide 1B1 (OATP1B1), and organic anion transporting polypeptide 1B3 (OATP1B3). The apical-to-basal transport of [¹⁴C]fluciclovine was attenuated by l-threonine, the substrate for system alanine-serine-cysteine (ASC) AATs. [¹⁴C]Fluciclovine uptake by drug transporter-expressing vesicles/cells was not significantly different from that of control vesicles/cells. Fluciclovine inhibited P-gp, MRP4, OAT1, OCT2, and OATP1B1 (IC₅₀ > 2.95 mM). Therefore, system ASC AATs may be partly involved in the renal reuptake of [¹⁸F]fluciclovine. Further, given that [¹⁸F]fluciclovine is recognized as an inhibitor with millimolar affinity for the tested drug transporters, slow urinary excretion of [¹⁸F]fluciclovine may be mediated by system ASC AATs, but not by drug transporters.

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.

Multiple myeloma and persistence of drug resistance in the age of novel drugs (Review)

Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease. Specifically, the emergence of multidrug resistance (MDR) during the course of treatment contributes significantly to treatment failure. The introduction of the immunomodulatory agents and proteasome inhibitors has seen an increase in overall patient survival, however, for the majority of patients, relapse remains inevitable with evidence that these agents, like the conventional chemotherapeutics are also subject to the development of MDR. Clinical management of patients with MM is currently compromised by lack of a suitable procedure to monitor the development of clinical drug resistance in individual patients. The current MM prognostic measures fail to pick the clonotypic tumor cells overexpressing drug efflux pumps, and invasive biopsy is insufficient in detecting sporadic tumors in the skeletal system. This review summarizes the challenges associated with treating the complex disease spectrum of myeloma, with an emphasis on the role of deleterious multidrug resistant clones orchestrating relapse.

A 13 mer LNA-i-miR-221 Inhibitor Restores Drug Sensitivity in Melphalan-Refractory Multiple Myeloma Cells

PURPOSE

The onset of drug resistance is a major cause of treatment failure in multiple myeloma. Although increasing evidence is defining the role of miRNAs in mediating drug resistance, their potential activity as drug-sensitizing agents has not yet been investigated in multiple myeloma.

EXPERIMENTAL DESIGN

Here we studied the potential utility of miR-221/222 inhibition in sensitizing refractory multiple myeloma cells to melphalan.

RESULTS

miR-221/222 expression inversely correlated with melphalan sensitivity of multiple myeloma cells. Inhibition of miR-221/222 overcame melphalan resistance and triggered apoptosis of multiple myeloma cells in vitro, in the presence or absence of human bone marrow (BM) stromal cells. Decreased multiple myeloma cell growth induced by inhibition of miR-221/222 plus melphalan was associated with a marked upregulation of pro-apoptotic BBC3/PUMA protein, a miR-221/222 target, as well as with modulation of drug influx-efflux transporters SLC7A5/LAT1 and the ABC transporter ABCC1/MRP1. Finally, in vivo treatment of SCID/NOD mice bearing human melphalan-refractory multiple myeloma xenografts with systemic locked nucleic acid (LNA) inhibitors of miR-221 (LNA-i-miR-221) plus melphalan overcame drug resistance, evidenced by growth inhibition with significant antitumor effects together with modulation of PUMA and ABCC1 in tumors retrieved from treated mice.

CONCLUSIONS

Taken together, our findings provide the proof of concept that LNA-i-miR-221 can reverse melphalan resistance in preclinical models of multiple myeloma, providing the framework for clinical trials to overcome drug resistance, and improve patient outcome in multiple myeloma.

Drug metabolism and clearance system in tumor cells of patients with multiple myeloma

Resistance to chemotherapy is a major limitation of cancer treatments with several molecular mechanisms involved, in particular altered local drug metabolism and detoxification process. The role of drug metabolism and clearance system has not been satisfactorily investigated in Multiple Myeloma (MM), a malignant plasma cell cancer for which a majority of patients escapes treatment. The expression of 350 genes encoding for uptake carriers, xenobiotic receptors, phase I and II Drug Metabolizing Enzymes (DMEs) and efflux transporters was interrogated in MM cells (MMCs) of newly-diagnosed patients in relation to their event free survival. MMCs of patients with a favourable outcome have an increased expression of genes coding for xenobiotic receptors (RXRα, LXR, CAR and FXR) and accordingly of their gene targets, influx transporters and phase I/II DMEs. On the contrary, MMCs of patients with unfavourable outcome displayed a global down regulation of genes coding for xenobiotic receptors and the downstream detoxification genes but had a high expression of genes coding for ARNT and Nrf2 pathways and ABC transporters. Altogether, these data suggests ARNT and Nrf2 pathways could be involved in MM primary resistance and that targeting RXRα, PXR, LXR and FXR through agonists could open new perspectives to alleviate or reverse MM drug resistance.

Mechanisms of Drug Resistance in Veterinary Oncology- A Review with an Emphasis on Canine Lymphoma

Drug resistance (DR) is the major limiting factor in the successful treatment of systemic neoplasia with cytotoxic chemotherapy. DR can be either intrinsic or acquired, and although the development and clinical implications are different, the underlying mechanisms are likely to be similar. Most causes for DR are pharmacodynamic in nature, result from adaptations within the tumor cell and include reduced drug uptake, increased drug efflux, changes in drug metabolism or drug target, increased capacity to repair drug-induced DNA damage or increased resistance to apoptosis. The role of active drug efflux transporters, and those of the ABC-transporter family in particular, have been studied extensively in human oncology and to a lesser extent in veterinary medicine. Methods reported to assess ABC-transporter status include detection of the actual protein (Western blot, immunohistochemistry), mRNA or ABC-transporter function. The three major ABC-transporters associated with DR in human oncology are ABCB1 or P-gp, ABCC1 or MRP1, and ABCG2 or BCRP, and have been demonstrated in canine cell lines, healthy dogs and dogs with cancer. Although this supports a causative role for these ABC-transporters in DR cytotoxic agents in the dog, the relative contribution to the clinical phenotype of DR in canine cancer remains an area of debate and requires further prospective studies.

Renal human organic anion transporter 3 increases the susceptibility of lymphoma cells to bendamustine uptake

Chronic lymphatic leukemia (CLL) is often associated with nephritic syndrome. Effective treatment of CLL by chlorambucil and bendamustine leads to the restoration of renal function. In this contribution, we sought to elucidate the impact of organic anion transporters (OATs) on the uptake of bendamustine and chlorambucil as a probable reason for the superior efficacy of bendamustine over chlorambucil in the treatment of CLL. We examined the effects of structural analogs of p-aminohippurate (PAH), melphalan, chlorambucil, and bendamustine, on OAT1-mediated [(3)H]PAH uptake and OAT3- and OAT4-mediated [(3)H]estrone sulfate (ES) uptake in stably transfected human embryonic kidney-293 cells. Melphalan had no significant inhibitory effect on any OAT, whereas chlorambucil reduced OAT1-, OAT3-, and OAT4-mediated uptake of PAH or ES down to 14.6%, 16.3%, and 66.0% of control, respectively. Bendamustine inhibited only OAT3-mediated ES uptake, which was reduced down to 14.3% of control cells, suggesting that it interacts exclusively with OAT3. The IC50 value for OAT3 was calculated to be 0.8 μM. Real-time PCR experiments demonstrated a high expression of OAT3 in lymphoma cell lines as well as primary CLL cells. OAT3-mediated accumulation of bendamustine was associated with reduced cell proliferation and an increased rate of apoptosis. We conclude that the high efficacy of bendamustine in treating CLL might be partly contributed to the expression of OAT3 in lymphoma cells and the high affinity of bendamustine for this transporter.

The role of P-glycoprotein in drug resistance in multiple myeloma

Multiple myeloma (MM) is a malignant neoplastic cancer of the plasma cells that involves the bone marrow. The majority of patients with MM initially respond to chemotherapy, but they eventually become resistant to later drug therapy. One of the reasons for drug resistance in patients with MM is efflux transporters. P-glycoprotein (P-gp) is the most studied of the multidrug resistance proteins, and is up-regulated in response to many chemotherapeutic drugs. This up-regulation of P-gp causes a decrease in the intracellular accumulation of these drugs, limiting their therapeutic efficacy. In this review, we focus on the role of P-gp in drugs used for patients with MM. P-gp has been found to be an important factor with regard to drug resistance in many of the drug classes used in the treatment of MM (proteasome inhibitors, anthracyclines, alkylating agents and immunomodulators are examples). Thus, our further understanding of its mechanism and inhibitory effects will help us decrease drug resistance in patients with MM.

Genomic profiling reveals distinctive molecular relapse patterns in IDH1/2 wild-type glioblastoma

Molecular changes associated with the progression of glioblastoma after standard radiochemotherapy remain poorly understood. We compared genomic profiles of 27 paired primary and recurrent IDH1/2 wild-type glioblastomas by genome-wide array-based comparative genomic hybridization. By bioinformatic analysis, primary and recurrent tumor profiles were normalized and segmented, chromosomal gains and losses identified taking the tumor cell content into account, and difference profiles deduced. Seven of 27 (26%) pairs lacked DNA copy number differences between primary and recurrent tumors (equal pairs). The recurrent tumors in 9/27 (33%) pairs contained all chromosomal imbalances of the primary tumors plus additional ones, suggesting a sequential acquisition of and/or selection for aberrations during progression (sequential pairs). In 11/27 (41%) pairs, the profiles of primary and recurrent tumors were divergent, i.e., the recurrent tumors contained additional aberrations but had lost others, suggesting a polyclonal composition of the primary tumors and considerable clonal evolution (discrepant pairs). Losses on 9p21.3 harboring the CDKN2A/B locus were significantly more common in primary tumors from sequential and discrepant (nonequal) pairs. Nonequal pairs showed ten regions of recurrent genomic differences between primary and recurrent tumors harboring 46 candidate genes associated with tumor recurrence. In particular, copy numbers of genes encoding apoptosis regulators were frequently changed at progression. In summary, approximately 25% of IDH1/2 wild-type glioblastoma pairs have stable genomic imbalances. In contrast, approximately 75% of IDH1/2 wild-type glioblastomas undergo further genomic aberrations and alter their clonal composition upon recurrence impacting their genomic profile, a process possibly facilitated by 9p21.3 loss in the primary tumor. © 2014 Wiley Periodicals, Inc.

Functional analysis of the involvement of apurinic/apyrimidinic endonuclease 1 in the resistance to melphalan in multiple myeloma

Background

Melphalan resistance has been considered one of the major obstacles to improve outcomes in multiple myeloma (MM) therapy; unfortunately, the mechanistic details of this resistance remain unclear. Melphalan is a highly effective alkylating agent which causes many types of DNA lesions, including DNA base alkylation damage that is repaired by base excision repair (BER). We postulated that human apurinic/apyrimidinic endonuclease 1 (APE1), an essential BER enzyme, plays a vital role in acquired melphalan resistance. However, because APE1 is a multifunctional protein with redox activity and acetylation modification in addition to its major repair activity, the particular APE1 function that may play a more important role in melphalan resistance is unknown.

Methods

Two MM cell lines, RPMI-8226 and U266 were used to measure the difference in APE1 levels in melphalan-resistant and sensitive derivatives. APE1 functional mutants for DNA repair, redox and acetylation were employed to investigate the roles of individual APE1 activities in acquired melphalan resistance.

Results

Our results indicate that APE1 is overexpressed in both MM melphalan-resistant cells. Knocking down APE1 sensitizes the melphalan resistant MM cells to melphalan treatment. The exogenous expression of DNA repair mutant H309N and acetylation mutant K6R/K7R of APE1 failed to restore the melphalan resistance of the APE1 knockdown RPMI-8226 cells. The AP endonuclease activity and multidrug resistance protein 1 (MDR1) regulatory activity may play roles in the melphalan resistance of MM cells.

Conclusions

The present study has identified that the DNA repair functions and the acetylation modification of APE1 are involved in melphalan resistance of MM cells and has also shed light on future therapeutic strategies targeting specific APE1 functions by small molecule inhibitors.

The role of LAT1 in (18)F-DOPA uptake in malignant gliomas

Positron emission tomography (PET) imaging with the amino acid tracer 6-(18)F-fluoro-L-3,4-dihydroxy-phenylalanine ((18)F-DOPA) may provide better spatial and functional information in human gliomas than CT or MRI alone. The L-type amino acid transporter 1 (LAT1) is responsible for membrane transport of large neutral amino acids in normal cells. This study assessed the relationship between LAT1 expression and (18)F-DOPA uptake in human astrocytomas. Endogenous LAT1 expression was measured in established glioblastoma (GBM) cell lines and primary GBM xenografts using Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Uptake of (18)F-DOPA was approximated in vitro using (3)H-L-DOPA as an analog. Uptake of (3)H-L-DOPA was assessed in cells expressing LAT1 shRNA or LAT1 siRNA and compared to non-targeted (NT) control shRNA or siRNA sequences, respectively. To demonstrate the clinical relevance of these findings, LAT1 immunofluorescence staining was compared with corresponding regions of (18)F-DOPA PET uptake in patients with newly diagnosed astrocytomas. LAT1 mRNA and protein expression varies in GBM, and the extent of (3)H-L-DOPA uptake was positively correlated with endogenous LAT1 expression. Stable shRNA-mediated LAT1 knockdown in T98 and GBM28 reduced (3)H-L-DOPA uptake relative to NT shRNA by 57 (P < 0.0001) and 52 % (P < 0.001), respectively. Transient siRNA-mediated LAT1 knockdown in T98 reduced (3)H-L-DOPA uptake relative to NT siRNA up to 68 % (P < 0.01). In clinical samples, LAT1 expression positively correlated with (18)F-DOPA PET uptake (P = 0.04). Expression of LAT1 is strongly associated with (3)H-L-DOPA uptake in vitro and (18)F-DOPA uptake in patient biopsy samples. These results define LAT1 as a key determinant of (18)F-DOPA accumulation in GBM.

Identification of transporters associated with Etoposide sensitivity of stomach cancer cell lines and methotrexate sensitivity of breast cancer cell lines by quantitative targeted absolute proteomics

Membrane transporter proteins may influence the sensitivity of cancer cells to anticancer drugs that can be recognized as substrates. The purpose of this study was to identify proteins that play a key role in the drug sensitivity of stomach and breast cancer cell lines by measuring the absolute protein expression levels of multiple transporters and other membrane proteins and examining their correlation to drug sensitivity. Absolute protein expression levels of 90 membrane proteins were examined by quantitative targeted absolute proteomics using liquid chromatography-linked tandem mass spectrometry. Among them, 11 and 14 membrane proteins, including transporters, were present in quantifiable amounts in membrane fraction of stomach cancer and breast cancer cell lines, respectively. In stomach cancer cell lines, the protein expression level of multidrug resistance-associated protein 1 (MRP1) was inversely correlated with etoposide sensitivity. MK571, an MRP inhibitor, increased both the cell-to-medium ratio of etoposide and the etoposide sensitivity of MRP1-expressing stomach cancer cell lines. In breast cancer cell lines, the protein expression level of reduced folate carrier 1 (RFC1) was directly correlated with methotrexate (MTX) sensitivity. Initial uptake rate and steady-state cell-to-medium ratio of [(3)H]MTX were correlated with both RFC1 expression level and MTX sensitivity. These results suggest that MRP1 modulates the etoposide sensitivity of stomach cancer cell lines and RFC1 modulates the MTX sensitivity of breast cancer cell lines. Our results indicate that absolute quantification of multiple membrane proteins could be a useful strategy for identification of candidate proteins involved in drug sensitivity.

Overexpression of MDR1 and survivin, and decreased Bim expression mediate multidrug-resistance in multiple myeloma cells

Multidrug resistance represents a major obstacle for the chemotherapy of a wide variety of human tumors. To investigate the underlying mechanisms associated with resistance to anti-cancer drugs, we established anti-cancer drug-resistant multiple myeloma (MM) cell lines RPMI8226/ADM, RPMI8226/VCR, RPMI8226/DEX, and RPMI8226/L-PAM, the 50% inhibitory concentration values of which were 77-, 58-, 79-, and 30-fold higher than their parental cell lines, respectively. The resistant cell lines overexpressed MDR1 and survivin, or showed decreased Bim expression. These results indicated that regulating these factors with inhibitors might be a viable approach to increasing the susceptibility of quiescent MM cells to chemotherapy.

Contribution of tumoral and host solute carriers to clinical drug response

Members of the solute carrier family of transporters are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. Several of these solute carriers are known to be expressed in cancer cells or cancer cell lines, and decreased cellular uptake of drugs potentially contributes to the development of resistance. As result, the expression levels of these proteins in humans have important consequences for an individual's susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. In this review article, we provide an update of this rapidly emerging field, with specific emphasis on the direct contribution of solute carriers to anticancer drug uptake in tumors, the role of these carriers in regulation of anticancer drug disposition, and recent advances in attempts to evaluate these proteins as therapeutic targets.

Modulation of P-glycoprotein ATPase of Helicoverpa armigera by cholesterol: effects on ATPase activity and interaction of insecticides

Purified P-glycoprotein ATPase from Helicoverpa armigera (Ha-Pgp), reconstituted in proteoliposomes composed of phospholipids and cholesterol, shows higher ATPase activity in the presence of cholesterol than in its absence. The Ha-Pgp ATPase activity was increased 30-40% with cholesterol. The KM for ATP was found to be 1 and 0.8 mM in the absence and presence of cholesterol, respectively. The insecticide-stimulated Ha-Pgp ATPase activity was increased by 10-20% for all the insecticides in the reconstituted proteoliposomes containing cholesterol compared to those with no cholesterol. The effects of cholesterol on KM and Vmax values of insecticide-stimulated Ha-Pgp ATPase activity were unrelated to the size of the insecticide. Ha-Pgp tryptophan fluorescence displayed a red shift of 3 and 8 nm in emission spectra upon binding of insecticides. Cholesterol enhances the interaction of insecticides with Ha-Pgp. Kd values of different insecticides for binding to Ha-Pgp were found to be lower in the presence of cholesterol in the proteoliposomes compared to its absence. Results suggest that cholesterol plays a role in the recognition and interaction of insecticides by modulating Ha-Pgp ATPase and may be involved in efflux of insecticides from cells by the transporter.

Genetically polymorphic OCT1: another piece in the puzzle of the variable pharmacokinetics and pharmacodynamics of the opioidergic drug tramadol

We investigated whether tramadol or its active metabolite, O-desmethyltramadol, are substrates of the organic cation transporter OCT1 and whether polymorphisms in OCT1 affect tramadol and O-desmethyltramadol pharmacokinetics. Tramadol showed high permeability through parallel artificial membrane permeability assays (PAMPAs). Tramadol uptake in HEK293 cells did not change after OCT1 overexpression, and the concentrations of tramadol in the plasma of healthy volunteers were independent of their OCT1 genotypes. In contrast, O-desmethyltramadol showed low membrane permeability, and OCT1 overexpression increased O-desmethyltramadol uptake 2.4-fold. This increase in uptake was reversed by OCT1 inhibitors and absent when loss-of-function OCT1 variants were overexpressed. Volunteers carrying loss-of-function OCT1 polymorphisms had significantly higher plasma concentrations of O-desmethyltramadol (P = 0.002, n = 41) and significantly prolonged miosis, a surrogate marker of opioidergic effects (P = 0.005, n = 24). In conclusion, polymorphisms in OCT1 influence the pharmacokinetics of O-desmethyltramadol, presumably by affecting its uptake into liver cells, and thus may modulate the efficacy of tramadol treatment.

The NK₁ receptor antagonist aprepitant does not alter the pharmacokinetics of high-dose melphalan chemotherapy in patients with multiple myeloma

AIMS

The objective of this investigation was to assess the effect of aprepitant on the pharmacokinetics of high-dose melphalan used as conditioning therapy before blood stem cell transplantation in multiple myeloma.

METHODS

Aprepitant (125 mg) or placebo was administered 1 h before melphalan therapy (1 h infusion of 100 mg m⁻²). Eleven plasma samples were obtained over 8 h and melphalan was quantified using an LC/MS/MS method. Standard pharmacokinetic parameters were calculated and nonparametric testing was applied to assess the differences between aprepitant and placebo treatment.

RESULTS

Twenty patients received placebo and 10 patients aprepitant treatment. There were no differences observed for C(max) at the end of melphalan infusion (placebo 3431 ± 608 ng ml⁻¹ vs. aprepitant 3269 ± 660 ng ml⁻¹). In addition, AUC and terminal elimination half-life were not changed by aprepitant. Total clearance of melphalan was 304 ± 58 ml min⁻¹ m⁻² (placebo) which was not influenced by aprepitant (288 ± 78 ml min⁻¹ m⁻²).

CONCLUSIONS

The administration of the NK₁ receptor antagonist aprepitant 1 h before a high-dose chemotherapy does not influence the exposure and the elimination of melphalan. Therefore, oral administration of 125 mg aprepitant 1 h before melphalan infusion does not alter the disposition of intravenously administered melphalan.

P-glycoprotein ATPase from the resistant pest, Helicoverpa armigera: purification, characterization and effect of various insecticides on its transport function

Helicoverpa armigera is a major pest of agricultural crops and has developed resistance to various insecticides. A P-glycoprotein (Pgp) with ATPase activity likely to be involved in insecticide resistance was purified and characterized from insecticide-resistant H. armigera. The purification was 18-fold with 3% yield. The optimum pH and temperature were found to be 7.4 and 30-40 degrees C, respectively. Kinetic studies indicated that this enzyme had a K(m) value of 1.2mM for ATP. Pgp from H. armigera was partially sequenced and found to be homologous to conserved sequences of mammalian Pgps. Pesticides stimulated H. armigera Pgp ATPase activity with a maximum stimulation of up to 40%. Quenching of the intrinsic tryptophan fluorescence of purified Pgp was used to quantitate insecticide binding. Using the high-affinity fluorescent substrate, tetramethylrosamine, transport was monitored in real time in proteoliposomes containing H. armigera Pgp. The presence of Pgp could be one of the reasons for insecticide resistance in this pest.