Defective hCNT1 transport contributes to gemcitabine chemoresistance in ovarian cancer subtypes: overcoming transport defects using a nanoparticle approach

Synthetically Tunable Suprahybrid Nanoparticle Platform for the Efficacious Delivery of Therapeutics

The discovery of lipid-hybrid nanosystems has offered potential solutions to various drug delivery and theranostic challenges. However, in many instances, the commonly used lipids and other components in these systems often pose challenges related to their solubility, physicochemical properties, immune compatibility, and limited synthetic tunability. In this work, we introduce a synthetically tunable supramolecular scaffold with amphiphilic characteristics based on the calix[4]arene macrocyclic system. We designed and synthesized two novel calix[4]arene-polyethylene glycol (PEG) conjugates, termed Cal-P1 and Cal-P2, and these were characterized utilizing a wide range of spectroscopic and analytical methods. The rational design of Cal-P1 and Cal-P2 demonstrates their utility in forming stable blended nanospheres with sustained drug release characteristics. The synergistic blending of PLGA and the calixarene scaffold (Cal-P1 and Cal-P2) in constructing long-lasting and controlled-release nanoparticles (NPs), which are optimized for encapsulating Nile Red dye, and their successful internalization and retention in HeLa cancer cells are demonstrated through in vitro assays. The potential of these NPs as sustained therapeutic carriers is investigated in vivo, showing improved retention compared to free dye with negligible toxicity. The successful design and construction of Cal-P1 and Cal-P2 nanosystems represent a new paradigm for addressing drug loading challenges, opening up opportunities for the development of highly efficient, synthetically tunable alternative adjuvants for drug encapsulation and delivery.

microRNAs Associated with Gemcitabine Resistance via EMT, TME, and Drug Metabolism in Pancreatic Cancer

Despite extensive research, pancreatic cancer remains a lethal disease with an extremely poor prognosis. The difficulty in early detection and chemoresistance to therapeutic agents are major clinical concerns. To improve prognosis, novel biomarkers, and therapeutic strategies for chemoresistance are urgently needed. microRNAs (miRNAs) play important roles in the development, progression, and metastasis of several cancers. During the last few decades, the association between pancreatic cancer and miRNAs has been extensively elucidated, with several miRNAs found to be correlated with patient prognosis. Moreover, recent evidence has revealed that miRNAs are intimately involved in gemcitabine sensitivity and resistance through epithelial-to-mesenchymal transition, the tumor microenvironment, and drug metabolism. Gemcitabine is the gold standard drug for pancreatic cancer treatment, but gemcitabine resistance develops easily after chemotherapy initiation. Therefore, in this review, we summarize the gemcitabine resistance mechanisms associated with aberrantly expressed miRNAs in pancreatic cancer, especially focusing on the mechanisms associated with epithelial-to-mesenchymal transition, the tumor microenvironment, and metabolism. This novel evidence of gemcitabine resistance will drive further research to elucidate the mechanisms of chemoresistance and improve patient outcomes.

Nanoparticle-Based Combination Therapy for Ovarian Cancer

Ovarian cancer is one of the most common malignant tumors in gynecology with a high incidence. Combination therapy, eg, administration of paclitaxel followed by a platinum anticancer drug is recommended to treat ovarian cancer due to its advantages in, eg, reducing side effects and reversing (multi)drug-resistance compared to single treatment. However, the benefits of combination therapy are often compromised. In chemo and chemo/gene combinations, co-deposition of the combined therapeutics in the tumor cells is required, which is difficult to achieve due to dramatic pharmacokinetic differences between combinational agents in free forms. Moreover, some undesired properties such as the low-water solubility of chemodrugs and the difficulty of cellular internalization of gene therapeutics also hinder the therapeutic potential. Delivery of dual or multiple agents by nanoparticles provides opportunities to tackle these limits. Nanoparticles encapsulate hydrophobic drug(s) to yield aqueous dispersions facilitating its administration and/or to accommodate hydrophilic genes facilitating its access to cells. Moreover, nanoparticle-based therapeutics can not only improve drug properties (eg, in vivo stability) and ensure the same drug disposition behavior with controlled drug ratios but also can minimize drug exposure of the normal tissues and increase drug co-accumulation at targeted tissues via passive and/or active targeting strategies. Herein, this work summarizes nanoparticle-based combination therapies, mainly including anticancer drug-based combinations and chemo/gene combinations, and emphasizes the advantageous outcomes of nanocarriers in the combination treatment of ovarian cancer. In addition, we also review mechanisms of synergetic effects resulting from different combinations.

Nucleoside transporters and immunosuppressive adenosine signaling in the tumor microenvironment: Potential therapeutic opportunities

Adenosine compartmentalization has a profound impact on immune cell function by regulating adenosine localization and, therefore, extracellular signaling capabilities, which suppresses immune cell function in the tumor microenvironment. Nucleoside transporters, responsible for the translocation and cellular compartmentalization of hydrophilic adenosine, represent an understudied yet crucial component of adenosine disposition in the tumor microenvironment. In this review article, we will summarize what is known regarding nucleoside transporter's function within the purinome in relation to currently devised points of intervention (i.e., ectonucleotidases, adenosine receptors) for cancer immunotherapy, alterations in nucleoside transporter expression reported in cancer, and potential avenues for targeting of nucleoside transporters for the desired modulation of adenosine compartmentalization and action. Further, we put forward that nucleoside transporters are an unexplored therapeutic opportunity, and modulation of nucleoside transport processes could attenuate the pathogenic buildup of immunosuppressive adenosine in solid tumors, particularly those enriched with nucleoside transport proteins.

Recent nanotechnology advancements to treat multidrug-resistance pancreatic cancer: Pre-clinical and clinical overview

Pancreatic cancer (PC) remains one of the most lethal and incurable forms of cancer and has a poor prognosis. One of the significant therapeutic challenges in PC is multidrug resistance (MDR), a phenomenon in which cancer cells develop resistance toward administered therapy. Development of novel therapeutic platforms that could overcome MDR in PC is crucial for improving therapeutic outcomes. Nanotechnology is emerging as a promising tool to enhance drug efficacy and minimize off-target responses via passive and/or active targeting mechanisms. Over the past decade, tremendous efforts have been made to utilize nanocarriers capable of targeting PC cells while minimizing off-target effects. In this review article, we first give an overview of PC and the major molecular mechanisms of MDR, and then we discuss recent advancements in the development of nanocarriers used to overcome PC drug resistance. In doing so, we explore the developmental stages of this research in both pre-clinical and clinical settings. Lastly, we discuss current challenges and gaps in the literature as well as potential future directions in the field.

Intersection of Inorganic Chemistry and Nanotechnology for the Creation of New Cancer Therapies

Since its discovery in 1965, the inorganic drug cisplatin has become a mainstay of cancer therapies and has inspired many platinum (Pt)-based compounds to solve various issues of toxicity and limitations associated with the original cisplatin. However, many of these drugs/prodrugs continue to be plagued by an array of side effects, limited circulation, and half-life and off-target effects. To solve this issue, we have constructed an array of platinum-based prodrugs on a Pt(IV) skeleton, which provides more favorable geometry and hydrophobicity, easier functionalization, and ultimately better targeting abilities. Each of these Pt(IV) prodrugs aims to either combine cisplatin with other agents for a combination therapeutic effect or improve the targeting of cisplatin itself, all for the more effective treatment of specific cancers. Our developed prodrugs include Platin-A, which combines cisplatin with the anti-inflammatory agent aspirin, Platin-M, which is functionalized with a mitochondria-targeting moiety, and Platin-B and Platin-Cbl, which combine cisplatin with components to combat cellular resistance to chemotherapy. At the same time, however, we recognize the crucial role of nanotechnology in improving the efficacy of cisplatin prodrugs and other inorganic compounds for the treatment of cancers. We describe several key benefits provided by nanomedicine that vastly improve the reach and utility of cisplatin prodrugs, including the ability of biodegradable polymeric nanoparticles (NPs) to deliver these agents with precision to the mitochondria, transport drugs across the blood-brain barrier, and target cisplatin prodrugs to specific cancers using various ligands. In addition, we highlight our progress in the engineering of innovative new polymers to improve the release patterns, pharmacokinetics, and dosages of cancer therapies. In this Account, we aim to describe the growing need for collaboration between the fields of inorganic chemistry and nanotechnology and how new advancements can not only improve on traditional chemotherapeutic agents but also expand their reach to entirely new subsets of cancers. In addition to detailing the design and principles behind our modifications of cisplatin and the efficacy of these new prodrugs against aggressive, cisplatin-resistant, or metastatic cancers, we also shed light on nanotechnology's essential role in protecting inorganic drugs and the human body from one another for more effective disease treatment without the off-target effects with which it is normally associated. We hope that this perspective into the important intersection between inorganic medicinal chemistry and nanotechnology will inspire future research on cisplatin prodrugs and other inorganic agents, innovative polymer and NP design, and the ways in which these two fields can greatly advance cancer treatment.

Enhancement strategies for mesenchymal stem cells and related therapies

Cell therapy, particularly mesenchymal stem/stromal (MSC) therapy, has been investigated for a wide variety of disease indications, particularly those with inflammatory pathologies. However, recently it has become evident that the MSC is far from a panacea. In this review we will look at current and future strategies that might overcome limitations in efficacy. Many of these take their inspiration from stem cell niche and the mechanism of MSC action in response to the injury microenvironment, or from previous gene therapy work which can now benefit from the added longevity and targeting ability of a live cell vector. We will also explore the nascent field of extracellular vesicle therapy and how we are already seeing enhancement protocols for this exciting new drug. These enhanced MSCs will lead the way in more difficult to treat diseases and restore potency where donors or manufacturing practicalities lead to diminished MSC effect.

Transporters, TBC1D4, and ARID5B Variants to Explain Glycated Hemoglobin Variability in Patients with Type 2 Diabetes

INTRODUCTION

Genetic variants could aid in predicting antidiabetic drug response by associating them with markers of glucose control, such as glycated hemoglobin (HbA1c). However, pharmacogenetic implementation for antidiabetics is still under development, as the list of actionable markers is being populated and validated. This study explores potential associations between genetic variants and plasma levels of HbA1c in 100 patients under treatment with metformin.

METHODS

HbA1c was measured in a clinical chemistry analyzer (Roche), genotyping was performed in an Illumina-GSA array and data were analyzed using PLINK. Association and prediction models were developed using R and a 10-fold cross-validation approach.

RESULTS

We identified genetic variants on SLC47A1, SLC28A1, ABCG2, TBC1D4, and ARID5B that can explain up to 55% of the interindividual variability of HbA1c plasma levels in diabetic patients under treatment. Variants on SLC47A1, SLC28A1, and ABCG2 likely impact the pharmacokinetics (PK) of metformin, while the role of the two latter can be related to insulin resistance and regulation of adipogenesis.

CONCLUSIONS

Our results confirm previous genetic associations and point to previously unassociated gene variants for metformin PK and glucose control.

Quantitative measurements of IR780 in formulations and tissues

PURPOSE

IR780 iodide, a promising near-infrared dye, is widely used to prepare nanoparticles as a theranostic agent for tumor imaging and therapy. However, there are no validated (bio)analytical methods to measure IR780 in nanoparticles and tissues in literature. The aim of this study is to develop and validate a new HPLC method to measure IR780 concentration in IR780 formulations as well as a new LC-MS/MS method to measure IR780 concentration in tissue samples, particularly in liver and lung.

MATERIALS AND METHODS

IR780 granules that produced IR780 in situ self-assembled nanoparticles upon contact with water were prepared at two drug loadings (0.2 % and 0.37 %). An HPLC method was developed and validated to measure IR780 concentrations in IR780 granules and nanoparticles. Furthermore, a validated LC-MS/MS method was developed to measure IR780 in mouse liver and lung. Both HPLC method and LC-MS/MS method were validated in terms of specificity, stability, linearity, limit of detection, limit of quantification, accuracy and precision.

RESULTS

Both HPLC method and LC-MS/MS method achieved the criteria for method validation. The HPLC method was accurate in the concentration range of 0.5-25 μg/mL. The measured drug loadings were 95 % of the theoretical drug loadings. The validated LC-MS/MS method can quantitatively measure the concentrations of IR780 in liver and lung. The linear range of the LC-MS/MS method was 1-1000 ng/mL for both liver and lung samples. IR780 granules showed the lung selectivity compared to IR780 solution at 2 h after oral administration.

CONCLUSION

A validated HPLC method was developed to measure IR780 concentration in pharmaceutical formulations and a validated LC-MS/MS method was developed to measure IR780 concentration in tissues. These quantitative methods provide reliable measurements of IR780 in pharmaceutic formulations and biological samples, which will significantly facilitate the research of IR780 as a theranostic agent for cancer therapy and imaging.

Gemcitabine resistance in triple-negative breast cancer cells can be reverted by Drosophila melanogaster deoxyribonucleoside kinase in the nucleus or cytosol

The development of drug resistance to chemotherapeutic agents has consistently presented a challenge in terms of the treatment of patients with triple-negative breast cancer (TNBC). In the present study, gemcitabine (dFdC)-resistant TNBC cells were established, and the effects of lentivirus-deoxyribonucleoside kinase (dNK) and a mutated form of dNK (lentivirus-dNKmut) on reversing the acquired drug resistance in dFdC-resistant TNBC cells were explored. Quantitative PCR and western blotting experiment results suggested that Drosophila melanogaster (Dm)-dNK was stably expressed in the lentivirus-infected MDA-MB-231 and MDA-MB-231R cells in the nucleus or cytosol, and autoradiography experiments revealed similar levels of enzymatic activity in the cells expressing dNK or dNKmut. In vitro cytotoxicity assay revealed that the IC₅₀ values of dFdC were decreased 30~50-fold in the dFdC-resistant MDA-MB-231 cells following lentiviral transfection with dNK or dNKmut, and this effect was associated with a significantly increased rate of apoptosis compared with the cells transfected with the negative control lentivirus. In conclusion, Dm-dNK in the nucleus or cytosol may be a potential candidate for reversing acquired dFdC resistance in TNBC cells, which may form the basis of novel strategies for the treatment of patients with drug-resistant TNBC.

Recent Advances on Drug-Loaded Mesenchymal Stem Cells With Anti-neoplastic Agents for Targeted Treatment of Cancer

Mesenchymal stem cells (MSCs), as an undifferentiated group of adult multipotent cells, have remarkable antitumor features that bring them up as a novel choice to treat cancers. MSCs are capable of altering the behavior of cells in the tumor microenvironment, inducing an anti-inflammatory effect in tumor cells, inhibiting tumor angiogenesis, and preventing metastasis. Besides, MSCs can induce apoptosis and inhibit the proliferation of tumor cells. The ability of MSCs to be loaded with chemotherapeutic drugs and release them in the site of primary and metastatic neoplasms makes them a preferable choice as targeted drug delivery procedure. Targeted drug delivery minimizes unexpected side effects of chemotherapeutic drugs and improves clinical outcomes. This review focuses on recent advances on innate antineoplastic features of MSCs and the effect of chemotherapeutic drugs on viability, proliferation, and the regenerative capacity of various kinds of MSCs. It also discusses the efficacy and mechanisms of drug loading and releasing procedures along with in vivo and in vitro preclinical outcomes of antineoplastic effects of primed MSCs for clinical prospection.

NUC-1031, use of ProTide technology to circumvent gemcitabine resistance: current status in clinical trials

BACKGROUND

Resistance to gemcitabine chemotherapy is common in patients with pancreatic ductal adenocarcinoma (PDAC), biliary tract cancer (BTC) and ovarian cancers (OC), conferring poor survival. Use of ProTide technology led to the development of a 'partially-activated' monophosphorylated gemcitabine compound, termed NUC-1031. NUC-1031 enters cancer cells independent of the human equilibrative nucleoside transporter, does not require deoxycytidine kinase-mediated activation and resists cytidine deaminase-mediated breakdown into toxic by-products.

CURRENT FINDINGS

The phase I PRO-001 trial recruited 68 patients with advanced solid tumours; of the 49 patients that had response-evaluable disease, 5 (10%) had a partial response (PR) and 33 (67%) had stable disease (SD). Subsequently, the PRO-002 study assessed the safety and efficacy of NUC-1031 combined with carboplatin for patients with OC (n = 25); preliminary data from this study reported one (4%) unconfirmed complete response (CR), 8 (35%) PRs and 13 (57%) patients with SD, the final outcome data are awaited. The ABC-08 trial for advanced BTC assessed safety and efficacy of NUC-1031 combined with cisplatin; 14 patients were recruited with a 50% objective response rate in the intention to treat population at interim analysis. ACELARATE, the phase III trial in first-line advanced PDAC comparing NUC-1031 to gemcitabine monotherapy, recruited 200 patients but has been paused for futility analysis.

CONCLUSION

Early studies demonstrate NUC-1031 is well tolerated with favourable pharmacokinetic profiles. NUC-1031 use in PDAC remains unclear, but encouraging results of disease control in BTC and OC has prompted phase II and III trial development. NuTide 121, is a phase III trial comparing cisplatin-NUC 1031 combination to the standard of care cisplatin-gemcitabine and recruitment is ongoing. Recruiting trials and mature data from existing studies will help inform on the impact of NUC-1031 on patient survival over standard gemcitabine.

Overcoming Resistance to Platinum-Based Drugs in Ovarian Cancer by Salinomycin and Its Derivatives-An In Vitro Study

Polyether ionophore salinomycin (SAL) and its semi-synthetic derivatives are recognized as very promising anticancer drug candidates due to their activity against various types of cancer cells, including multidrug-resistant populations. Ovarian cancer is the deadliest among gynecologic malignancies, which is connected with the development of chemoresistant forms of the disease in over 70% of patients after initial treatment regimen. Thus, we decided to examine the anticancer properties of SAL and selected SAL derivatives against a series of drug-sensitive (A2780, SK-OV-3) and derived drug-resistant (A2780 CDDP, SK-OV-3 CDDP) ovarian cancer cell lines. Although SAL analogs showed less promising IC₅₀ values than SAL, they were identified as the antitumor agents that significantly overcome the resistance to platinum-based drugs in ovarian cancer, more potent than unmodified SAL and commonly used anticancer drugs—5-fluorouracil, gemcitabine, and cisplatin. Moreover, when compared with SAL used alone, our experiments proved for the first time increased selectivity of SAL-based dual therapy with 5-fluorouracil or gemcitabine, especially towards A2780 cell line. Looking closer at the results, SAL acted synergistically with 5-fluorouracil towards the drug-resistant A2780 cell line. Our results suggest that combinations of SAL with other antineoplastics may become a new therapeutic option for patients with ovarian cancer.

The phenotype of target pancreatic cancer cells influences cell death by magnetic hyperthermia with nanoparticles carrying gemicitabine and the pseudo-peptide NucAnt

In this paper we show that conjugation of magnetic nanoparticles (MNPs) with Gemcitabine and/or NucAnt (N6L) fostered their internalization into pancreatic tumor cells and that the coupling procedure did not alter the cytotoxic potential of the drugs. By treating tumor cells (BxPC3 and PANC-1) with the conjugated MNPs and magnetic hyperthermia (43 °C, 60 min), cell death was observed. The two pancreatic tumor cell lines showed different reactions against the combined therapy according to their intrinsic sensitivity against Gemcitabine (cell death, ROS production, ability to activate ERK 1/2 and JNK). Finally, tumors (e.g. 3 mL) could be effectively treated by using almost 4.2 × 10⁵ times lower Gemcitabine doses compared to conventional therapies. Our data show that this combinatorial therapy might well play an important role in certain cell phenotypes with low readiness of ROS production. This would be of great significance in distinctly optimizing local pancreatic tumor treatments.

Antitumor effect of gemcitabine-loaded albumin nanoparticle on gemcitabine-resistant pancreatic cancer induced by low hENT1 expression

Purpose

Gemcitabine is currently the standard first-line chemotherapeutic drug for treating pancreatic cancer. However, many factors can contribute to gemcitabine resistance. One of the most important reasons is the low hENT1 expression. In this study, we tested the antitumor effect of gemcitabine-loaded human serum albumin nanoparticle (GEM-HSA-NP) on gemcitabine-resistant pancreatic cancer induced by low hENT1 expression.

Materials and methods

S-(4-nitrobenzyl)-6-thioinosine was utilized to inhibit the activity of hENT1 and simulate low hENT1 expression. Growth inhibition assays and cell cycle and apoptosis analyses were performed on human pancreatic cancer cell lines such as BxPC-3 and SW1990. The in vivo antitumor effect was studied by using patient-derived xenograft (PDX) models. The in vivo toxicity assessment was performed on healthy Kunming mice.

Results

In in vitro studies, GEM-HSA-NP showed its ability to inhibit cell proliferation, arrest cell cycle and induce apoptosis when tumor cells were resistant to gemcitabine. In in vivo studies, GEM-HSA-NP was more effective than gemcitabine on inhibiting tumor growth whether the expression levels of hENT1 were high or low in PDX models. The in vivo toxicity assessment showed that the biotoxicity of GEM-HSA-NP did not increase compared with gemcitabine.

Conclusion

GEM-HSA-NP can overcome gemcitabine resistance induced by low hENT1 expression, which suggests its potential role for the clinical application.

Design, characterization, and in vitro antiproliferative efficacy of gemcitabine conjugates based on carboxymethyl glucan

Gemcitabine (GEM) is widely used in clinical practice in the treatment of cancer and several other solid tumors. Nevertheless, the antitumor effect of GEM is partially prevented by some limitations including short half life, and lack of tumor localizing. Carboxymethyl glucan (CMG), a carboxymethylated derivative of β-(1-3)-glucan, shows biocompatibility and biodegradability as well as a potential anticarcinogenic effect. To enhance the antiproliferative activity of GEM, four water soluble conjugates of GEM bound to CMG via diverse amino acid linkers were designed and synthesized. ¹H NMR, FT IR, elementary analysis and RP-HPLC chromatography were employed to verify the correct achievement of the conjugates. In vitro release study indicated that conjugates presented slower release in physiological buffer (pH 7.4) than acidic buffer (pH 5.5) mimicking the acidic tumor microenvironment. Moreover, A549, HeLa and Caco-2 cancer cell lines were used to evaluate the in vitro cytotoxicity of conjugates and the results showed that binding GEM to CMG significantly enhanced antiproliferative activity of GEM on A549 cells. Therefore, these conjugates may be potentially useful as a delivery vehicle in cancer therapy and worthy of further study on structure-activity relationship and antiproliferative activity in vitro and in vivo, especially for lung tumor.

ST6Gal-I sialyltransferase promotes chemoresistance in pancreatic ductal adenocarcinoma by abrogating gemcitabine-mediated DNA damage

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a poor prognosis. Gemcitabine, as a single agent or in combination therapy, remains the frontline chemotherapy despite its limited efficacy due to de novo or acquired chemoresistance. There is an acute need to decipher mechanisms underlying chemoresistance and identify new targets to improve patient outcomes. Here, we report a novel role for the ST6Gal-I sialyltransferase in gemcitabine resistance. Utilizing MiaPaCa-2 and BxPC-3 PDAC cells, we found that knockdown (KD) of ST6Gal-I expression, as well as removal of surface α2-6 sialic acids by neuraminidase, enhances gemcitabine-mediated cell death assessed via clonogenic assays and cleaved caspase 3 expression. Additionally, KD of ST6Gal-I potentiates gemcitabine-induced DNA damage as measured by comet assays and quantification of γH2AX foci. ST6Gal-I KD also alters mRNA expression of key gemcitabine metabolic genes, RRM1, RRM2, hENT1, and DCK, leading to an increased gemcitabine sensitivity ratio, an indicator of gemcitabine toxicity. Gemcitabine-resistant MiaPaCa-2 cells display higher ST6Gal-I levels than treatment-naïve cells along with a reduced gemcitabine sensitivity ratio, suggesting that chronic chemotherapy selects for clonal variants with more abundant ST6Gal-I. Finally, we examined Suit2 PDAC cells and Suit2 derivatives with enhanced metastatic potential. Intriguingly, three metastatic and chemoresistant subclones, S2-CP9, S2-LM7AA, and S2-013, exhibit up-regulated ST6Gal-I relative to parental Suit2 cells. ST6Gal-I KD in S2-013 cells increases gemcitabine-mediated DNA damage, indicating that suppressing ST6Gal-I activity sensitizes inherently resistant cells to gemcitabine. Together, these findings place ST6Gal-I as a critical player in imparting gemcitabine resistance and as a potential target to restore PDAC chemoresponse.

Overcoming tumor cell chemoresistance using nanoparticles: lysosomes are beneficial for (stearoyl) gemcitabine-incorporated solid lipid nanoparticles

Despite recent advances in targeted therapies and immunotherapies, chemotherapy using cytotoxic agents remains an indispensable modality in cancer treatment. Recently, there has been a growing emphasis in using nanomedicine in cancer chemotherapy, and several nanomedicines have already been used clinically to treat cancers. There is evidence that formulating small molecular cancer chemotherapeutic agents into nanomedicines significantly modifies their pharmacokinetics and often improves their efficacy. Importantly, cancer cells often develop resistance to chemotherapy, and formulating anticancer drugs into nanomedicines also helps overcome chemoresistance. In this review, we briefly describe the different classes of cancer chemotherapeutic agents, their mechanisms of action and resistance, and evidence of overcoming the resistance using nanomedicines. We then emphasize on gemcitabine and our experience in discovering the unique (stearoyl) gemcitabine solid lipid nanoparticles that are effective against tumor cells resistant to gemcitabine and elucidate the underlying mechanisms. It seems that lysosomes, which are an obstacle in the delivery of many drugs, are actually beneficial for our (stearoyl) gemcitabine solid lipid nanoparticles to overcome tumor cell resistance to gemcitabine.

Modulation of chemoresponsiveness to platinum-based agents by microRNAs in cancer

Ovarian cancer accounts for the highest mortality among all gynecologic cancers. Cytoreductive surgery followed by chemotherapy with a platinum-based agent (cisplatin or carboplatin) plus paclitaxel is the first-line option for treatment of epithelial ovarian cancer. However, primary or acquired resistance to platinum-based agents is a major clinical challenge. MicroRNAs are a group of small non-coding RNAs that regulate gene expression post-transcriptionally and may function as oncogenes or tumor-suppressor genes through extensive crosstalk with intracellular signaling pathways. Importantly, their dysregulation has been implicated in ovarian tumorigenesis. Pertinent to chemotherapy, increasing evidence has revealed that miRNAs can be directly linked to chemosensitivity to platinum-based agents in ovarian cancer. In this review, we summarize current evidence concerning the role of miRNAs in prediction and modulation of cellular responses to cisplatin and carboplatin in ovarian cancer.

Pharmacological factors affecting accumulation of gemcitabine's active metabolite, gemcitabine triphosphate

Gemcitabine is an anticancer agent acting against several solid tumors. It requires nucleoside transporters for cellular uptake and deoxycytidine kinase for activation into active gemcitabine-triphosphate, which is incorporated into the DNA and RNA. However, it can also be deaminated in the plasma. The intracellular level of gemcitabine-triphosphate is affected by scheduling or by combination with other chemotherapeutic regimens. Moreover, higher concentrations of gemcitabine-triphosphate may affect the toxicity, and possibly the clinical efficacy. As a consequence, different nucleoside analogs have been synthetized with the aim to increase the concentration of gemcitabine-triphosphate into cells. In this review, we summarize currently published evidence on pharmacological factors affecting the intracellular level of gemcitabine-triphosphate to guide future trials on the use of new nucleoside analogs.

Enhancing Drug Efficacy and Therapeutic Index through Cheminformatics-Based Selection of Small Molecule Binary Weapons That Improve Transporter-Mediated Targeting: A Cytotoxicity System Based on Gemcitabine

The transport of drug molecules is mainly determined by the distribution of influx and efflux transporters for which they are substrates. To enable tissue targeting, we sought to develop the idea that we might affect the transporter-mediated disposition of small-molecule drugs via the addition of a second small molecule that of itself had no inhibitory pharmacological effect but that influenced the expression of transporters for the primary drug. We refer to this as a “binary weapon” strategy. The experimental system tested the ability of a molecule that on its own had no cytotoxic effect to increase the toxicity of the nucleoside analog gemcitabine to Panc1 pancreatic cancer cells. An initial phenotypic screen of a 500-member polar drug (fragment) library yielded three “hits.” The structures of 20 of the other 2,000 members of this library suite had a Tanimoto similarity greater than 0.7 to those of the initial hits, and each was itself a hit (the cheminformatics thus providing for a massive enrichment). We chose the top six representatives for further study. They fell into three clusters whose members bore reasonable structural similarities to each other (two were in fact isomers), lending strength to the self-consistency of both our conceptual and experimental strategies. Existing literature had suggested that indole-3-carbinol might play a similar role to that of our fragments, but in our hands it was without effect; nor was it structurally similar to any of our hits. As there was no evidence that the fragments could affect toxicity directly, we looked for effects on transporter transcript levels. In our hands, only the ENT1-3 uptake and ABCC2,3,4,5, and 10 efflux transporters displayed measurable transcripts in Panc1 cultures, along with a ribonucleoside reductase RRM1 known to affect gemcitabine toxicity. Very strikingly, the addition of gemcitabine alone increased the expression of the transcript for ABCC2 (MRP2) by more than 12-fold, and that of RRM1 by more than fourfold, and each of the fragment “hits” served to reverse this. However, an inhibitor of ABCC2 was without significant effect, implying that RRM1 was possibly the more significant player. These effects were somewhat selective for Panc cells. It seems, therefore, that while the effects we measured were here mediated more by efflux than influx transporters, and potentially by other means, the binary weapon idea is hereby fully confirmed: it is indeed possible to find molecules that manipulate the expression of transporters that are involved in the bioactivity of a pharmaceutical drug. This opens up an entirely new area, that of chemical genomics-based drug targeting.

Nanoscale Coordination Polymers Codeliver Carboplatin and Gemcitabine for Highly Effective Treatment of Platinum-Resistant Ovarian Cancer

Due to the ability of ovarian cancer (OCa) to acquire drug resistance, it has been difficult to develop efficient and safe chemotherapy for OCa. Here, we examined the therapeutic use of a new self-assembled core-shell nanoscale coordination polymer nanoparticle (NCP-Carbo/GMP) that delivers high loadings of carboplatin (28.0 ± 2.6 wt %) and gemcitabine monophosphate (8.6 ± 1.5 wt %). A strong synergistic effect was observed between carboplatin and gemcitabine against platinum-resistant OCa cells, SKOV-3 and A2780/CDPP, in vitro. The coadministration of carboplatin and gemcitabine in the NCP led to prolonged blood circulation half-life (11.8 ± 4.8 h) and improved tumor uptake of the drugs (10.2 ± 4.4% ID/g at 24 h), resulting in 71% regression and 80% growth inhibition of SKOV-3 and A2780/CDDP tumors, respectively. Our findings demonstrate that NCP particles provide great potential for the codelivery of multiple chemotherapeutics for treating drug-resistant cancer.

Docetaxel combined with intraperitoneal hyperthermic perfusion chemotherapy and hyperthermia in the treatment of advanced ovarian cancer

Ovarian cancer is a clinical type of gynecological malignant tumor with poor prognosis and a high mortality rate. At present, the primary treatment method used is surgery, with chemotherapy as an ajdunctive therapy. Thus, new short-term treatments should be identified. The aim of the present study was to investigate the short-term curative effects and safety of docetaxel combined with intraperitoneal cisplatin chemotherapy and hyperthermia treatment of advanced ovarian cancer. A total of 112 cases of advanced (stage III–IV) ovarian cancer patients confirmed by clinical diagnosis between October 2014 and December 2015 were included in the study. The patients were randomly divided into the study and control groups (n=56 cases). The control group was treated with docetaxel and intraperitoneal cisplatin hyperthermic perfusion chemotherapy, while the study group was treated with docetaxel venous chemotherapy and intraperitoneal cisplatin cyclical hyperthermic perfusion chemotherapy with BR-TRG-1 body cavity hyperthermic perfusion treatment system. Clinical treatment results for short-term curative effects and adverse reactions were compared and analyzed 8 weeks after treatment. The total effective rate of the study and control groups were 87.5 and 62.5%, respectively, and the difference was statistically significant (P<0.05). The controlled rate of ascites, remission rate of tumor and descent rate of CA125 of patients in the study group were better than patients in the control group (P<0.05). The rate of adverse reactions of patients in the study group was 39.3%, and the grade of toxicity was from I to II, while the rate of adverse reactions of patients in the control group was 55.4%, and the grade of toxicity was from II to III. The difference between the two groups was statistically significant (P<0.05). In conclusion, applying the combination of docetaxel, intraperitoneal cisplatin hyperthermic perfusion chemotherapy and hyperthermia to treat advanced ovarian cancer can improve the curative effects with little toxicity; thus, it is worthy of promotion and application.

Gemcitabine resistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) ranks fourth among cancer related deaths. The disappointing 5-year survival rate of below 5% stems from drug resistance to all known therapies, as well as from disease presentation at a late stage when PDA is already metastatic. Gemcitabine has been the cornerstone of PDA treatment in all stages of the disease for the last two decades, but gemcitabine resistance develops within weeks of chemotherapy initiation. From a mechanistic perspective, gemcitabine resistance may result from alterations in drug metabolism until the point that the cytidine analog is incorporated into the DNA, or from mitigation of gemcitabine-induced apoptosis. Both of these drug resistance modalities can be either intrinsic to the cancer cell, or influenced by the cancer microenvironment. Mechanisms of intrinsic gemcitabine resistance are difficult to tackle, as many of the genes that drive the carcinogenic process itself also interfere with gemcitabine-induced apoptosis. In this regard, recent understanding of the involvement of microRNAs in gemcitabine resistance may offer new opportunities to overcome intrinsic gemcitabine resistance. The characteristically fibrotic and immune infiltrated stroma of PDA that accompanies tumor inception and expansion is a lush ground for treatments aimed at targeting tumor microenvironment-mediated drug resistance. In the last couple of years, drugs interfering with tumor microenvironment have matured to clinical trials. Although drugs inducing 'stromal depletion' have yet failed to improve survival, they have greatly increased our understanding of tumor microenvironment-mediated drug resistance. In this review we summarize the current knowledge on intrinsic and environment-mediated gemcitabine resistance, and discuss the impact of these pathways on patient screening, and on future treatments aimed to potentiate gemcitabine activity.