The folate receptor as a rational therapeutic target for personalized cancer treatment

Polymeric Nanoparticle-Mediated Gene Delivery for Lung Cancer Treatment

In recent years, researchers have focused on targeted gene therapy for lung cancer, using nanoparticle carriers to overcome the limitations of conventional treatment methods. The main goal of targeted gene therapy is to develop more efficient therapeutic strategies by improving the bioavailability, stability, and target specificity of gene therapeutics and to reduce off-target effects. Polymer-based nanoparticles, an alternative to lipid and inorganic nanoparticles, efficiently carry nucleic acid therapeutics and are stable in vivo. Receptor-targeted delivery is a promising approach that can limit non-specific gene delivery and can be achieved by modifying the polymer nanoparticle surface with specific receptor ligands or antibodies. This review highlights the recent developments in gene delivery using synthetic and natural polymer-based nucleic acid carriers for lung cancer treatment. Various nanoparticle systems based on polymers and polymer combinations are discussed. Further, examples of targeting ligands or moieties used in targeted, polymer-based gene delivery to lung cancer are reviewed.

Safety and Activity of Mirvetuximab Soravtansine (IMGN853), a Folate Receptor Alpha-Targeting Antibody-Drug Conjugate, in Platinum-Resistant Ovarian, Fallopian Tube, or Primary Peritoneal Cancer: A Phase I Expansion Study

Purpose This phase I expansion cohort study evaluated the safety and clinical activity of mirvetuximab soravtansine (IMGN853), an antibody-drug conjugate consisting of a humanized anti-folate receptor alpha (FRα) monoclonal antibody linked to the tubulin-disrupting maytansinoid DM4, in a population of patients with FRα-positive and platinum-resistant ovarian cancer. Patients and Methods Patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer received IMGN853 at 6.0 mg/kg (adjusted ideal body weight) once every 3 weeks. Eligibility included a minimum requirement of FRα positivity by immunohistochemistry (≥ 25% of tumor cells with at least 2+ staining intensity). Adverse events, tumor response (via Response Evaluation Criteria in Solid Tumors [RECIST] version 1.1), and progression-free survival (PFS) were determined. Results Forty-six patients were enrolled. Adverse events were generally mild (≤ grade 2), with diarrhea (44%), blurred vision (41%), nausea (37%), and fatigue (30%) being the most commonly observed treatment-related toxicities. Grade 3 fatigue and hypotension were reported in two patients each (4%). For all evaluable patients, the confirmed objective response rate was 26%, including one complete and 11 partial responses, and the median PFS was 4.8 months. The median duration of response was 19.1 weeks. Notably, in the subset of patients who had received three or fewer prior lines of therapy (n = 23), an objective response rate of 39%, PFS of 6.7 months, and duration of response of 19.6 weeks were observed. Conclusion IMGN853 exhibited a manageable safety profile and was active in platinum-resistant ovarian cancer, with the strongest signals of efficacy observed in less heavily pretreated individuals. On the basis of these findings, the dose, schedule, and target population were identified for a phase III trial of IMGN853 monotherapy in patients with platinum-resistant disease.

Radiosynthesis and evaluation of a 99mTc-folic acid radiotracer prepared using [99mTcN(PNP)]2+ metal fragment

Folate receptors (FR) are over-expressed on a wide variety of tumor cells and are a potential molecular target for radiolabeled folates. In this respect, several SPECT and PET based radiofolates have been evaluated in the past albeit with their high renal uptake posing limitation towards their clinical use. To overcome this, a new ^99mTc labeled folic acid was synthesized via the use of [^99mTcN(PNP)]²⁺ metal fragment, where the presence of the latter pharmacophore redirects in vivo clearance via the hepatobiliary pathway. In this respect, folic acid was derivatized at the γ-acid group with a cysteine BFCA (bifunctional chelating agent) and subsequently reacted with the preformed [^99mTcN]²⁺ intermediate in presence of PNP2 (bisphosphine) ligand, to yield the final complex. While preliminary, in vivo distribution of the complex exhibited high association of activity with liver and intestines and provided support to the rationality of the present design as clearance of labeled folic acid could be effected via the hepatic route, the in vitro studies of the folic acid-cysteine conjugate carried out in KB-31 cells, did not show much promise with reduction in receptor affinity in comparison with the native folic acid. The route followed herein to prepare a folic-acid based radiotracer constitutes the first report of radiolabeling folic acid using the [^99mTcN(PNP)]²⁺ as a radiosynthon. Modification in the structure of conjugate by linking the BFCA through a long-chain linker can be envisaged to improve the affinity of [^99mTcN(PNP)]-folic acid complex towards FRs.

Immunohistochemical Surrogates for Molecular Classification of Breast Carcinoma: A 2015 Update

CONTEXT

-The pioneering works on molecular classification (MC) by Perou and Sorlie et al in the early 2000s using global gene expression profiling identified 5 intrinsic subtypes of invasive breast cancers (IBCs): luminal A, luminal B, normal breast-like, HER2-enriched, and basal-like subtypes, each unique in incidence, survival, and response to therapy. Because the application of gene expression profiling in daily practice is not economical or practical at the present time, many investigators have studied the use of immunohistochemical (IHC) surrogates as a substitute for determining the MC of IBC.

OBJECTIVE

-To discuss the continuing efforts that have been made to develop clinically significant and readily available IHC surrogates for the MC of IBC.

DATA SOURCES

-Data were obtained from pertinent peer-reviewed English-language literature.

CONCLUSIONS

-The most commonly used IHC surrogates are estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2), dividing IBC into luminal, HER2, and triple-negative subtypes. The addition of Ki-67, cytokeratin 5, and epidermal growth factor receptor (EGFR) separates luminal B from luminal A subtypes, and basal-like subtype from triple-negative breast cancer. More recently, biomarkers such as androgen receptor and p53 have been shown to further stratify these molecular subtypes. Although many studies of IHC-based MC have shown clinical significance similar to gene expression profiling-defined MC, its critical limitations are: (1) a lack of standardization in terminology, (2) a lack of standardization in biomarkers used for each subtype, and (3) the lack of a uniform cutoff for each biomarker. A panel of IHC surrogates for each subtype of IBC is proposed.

Concordance of folate receptor-α expression between biopsy, primary tumor and metastasis in breast cancer and lung cancer patients

Folate receptor alpha (FRα) is known to be upregulated in a variety of cancers, including non-small cell lung cancer (NSCLC) and breast cancer. To ensure reliable implementation of diagnostic- and therapeutic agents, concordance of FRα expression between biopsy, primary tumor and metastases is important. Using immunohistochemistry (Mab 26B3.F2) these concordances were investigated in 60 NSCLC and 40 breast cancer patients. False positivity of FRα expression on breast and lung cancer biopsies was limited to less than 5%. In NSCLC, FRα expression was shown in 21/34 adenocarcinomas and 4/26 squamous cell carcinomas (SCC). Concordance of FRα expression between biopsy and primary tumor was achieved in respectively 83% and 91% of adenocarcinomas and SCCs. Approximately 80% of all local and distant metastases of NSCLC patients showed concordant FRα expression as their corresponding primary tumor. In breast cancer, FRα positivity was shown in 12/40 biopsies, 20/40 lumpectomies and 6/20 LN metastases, with concordance of 68% between biopsy and primary tumor and 60% between primary tumor and LN metastases. In conclusion, this study shows high concordance rates of FRα expression between biopsies and metastases compared to primary NSCLC and breast cancers, underscoring the applicability of FRα-targeted agents in these patients.

Dual Targeting of Epithelial Ovarian Cancer Via Folate Receptor α and the Proton-Coupled Folate Transporter with 6-Substituted Pyrrolo[2,3-d]pyrimidine Antifolates

Folate uptake in epithelial ovarian cancer (EOC) involves the reduced folate carrier (RFC) and the proton-coupled folate transporter (PCFT), both facilitative transporters and folate receptor (FR) α. Although in primary EOC specimens, FRα is widely expressed and increases with tumor stage, PCFT was expressed independent of tumor stage (by real-time RT-PCR and IHC). EOC cell line models, including cisplatin sensitive (IGROV1 and A2780) and resistant (SKOV3 and TOV112D) cells, expressed a 17-fold range of FRα and similar amounts (within ∼2-fold) of PCFT. Novel 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates AGF94 and AGF154 exhibited potent antiproliferative activities toward all of the EOC cell lines, reflecting selective cellular uptake by FRα and/or PCFT over RFC. When IGROV1 cells were pretreated with AGF94 at pH 6.8, clonogenicity was potently inhibited, confirming cell killing. FRα was knocked down in IGROV1 cells with lentiviral shRNAs. Two FRα knockdown clones (KD-4 and KD-10) showed markedly reduced binding and uptake of [³H]folic acid and [³H]AGF154 by FRα, but maintained high levels of [³H]AGF154 uptake by PCFT compared to nontargeted control cells. In proliferation assays, KD-4 and KD-10 cells preserved in vitro inhibition by AGF94 and AGF154, compared to a nontargeted control, attributable to residual FRα- and substantial PCFT-mediated uptake. KD-10 tumor xenografts in severe-compromised immune-deficient mice were likewise sensitive to AGF94 Collectively, our results demonstrate the substantial therapeutic potential of novel 6-substituted pyrrolo[2,3-d]pyrimidine antifolates with dual targeting of PCFT and FRα toward EOCs that express a range of FRα, along with PCFT, as well as cisplatin resistance. Mol Cancer Ther; 16(5); 819-30. ©2017 AACR.

Synthesis and antiproliferative activity of a series of novel 6-substituted pyrido[3,2-d]pyrimidines as potential nonclassical lipophilic antifolates targeting dihydrofolate reductase

Dihydrofolate reductase (DHFR) has been a well-recognized target for the treatment of many diseases. Based on 8,10-dideazaminopterins, which are classical antifolates that potently inhibit DHFR, we have designed a series of novel 2,4-diamino-6-substituted pyrido[3,2-d]pyrimidines. By removing the glutamate moiety and introducing lipophilic groups, we hoped to improve passive diffuse through the cell membranes. The target compounds were efficiently synthesized using one-pot procedure and evaluated in vitro for DHFR inhibition and antitumor activity. Compounds 5e, 5h, 5i and 5k were the most potent inhibitors of recombinant human DHFR (rhDHFR) with IC₅₀ values in the range 0.2-1.0 μM. Analysis using flow cytometric indicated that the effect of compound 5k on cell cycle progression was linked to induction of S phase arrest. Compounds 5g, 5h, 5i and 5k showed broad spectrum antitumor activity against four different tumor cell lines, with IC₅₀ values in the range 0.07-23 μM. Molecular docking investigations showed that the trimethoyphenyl ring of compound 5k occupied a position near the cofactor-binding site in the rhDHFR-inhibitor complex, with close intermolecular contacts with Asp21, Phe31, Ser59, Ile60 and Pro61.

Magnetic nanoparticles-based drug and gene delivery systems for the treatment of pulmonary diseases

Magnetic nanoparticles (MNPs) have gained much attention due to their unique properties such as biocompatibility and biodegradability as well as magnetic and heat-medicated characteristics. Due to these inherent properties, MNPs have been widely used in various biomedical applications including targeted drug delivery and hyperthermia-based therapy. Hyperthermia is a promising approach for the thermal activation therapy of several diseases, including pulmonary diseases. Additionally, due to their large loading capacity and controlled release ability, several MNP-based drug delivery systems have been emerged for treatment of cystic fibrosis and lung cancer. This review provides an overview on the unique properties of MNPs and magnetic-mediated hyperthermia with emphasis on the recent biomedical applications of MNPs in treatment of both lung cancer and cystic fibrosis.

Antibody-drug conjugates and other nanomedicines: the frontier of gynaecological cancer treatment

Gynaecological cancers: malignancies of the cervix, uterus, ovaries, vagina and vulva, are responsible for over 1.1 million new cancer cases and almost half a million deaths annually. Ovarian cancer in particular is difficult to treat due to often being diagnosed at a late stage, and the incidence of uterine and vulvar malignancies are both on the rise. The field of nanomedicine is beginning to introduce drugs into the clinic for oncological applications exemplified by the liposomal drugs, Doxil and Myocet, the nanoparticle, Abraxane and antibody-drug conjugates (ADCs), Kadcyla and Adcetris. With many more agents currently undergoing clinical trials, the field of nanomedicine promises to have a significant impact on cancer therapy. This review considers the state of the art for nanomedicines currently on the market and those being clinically evaluated for the treatment of gynaecological cancers. In particular, it focuses on ADCs and presents a methodology for their rational design and evaluation.

Mirvetuximab Soravtansine (IMGN853), a Folate Receptor Alpha-Targeting Antibody-Drug Conjugate, Potentiates the Activity of Standard of Care Therapeutics in Ovarian Cancer Models

Elevated folate receptor alpha (FRα) expression is characteristic of epithelial ovarian cancer (EOC), thus establishing this receptor as a candidate target for the development of novel therapeutics to treat this disease. Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate (ADC) that targets FRα for tumor-directed delivery of the maytansinoid DM4, a potent agent that induces mitotic arrest by suppressing microtubule dynamics. Here, combinations of IMGN853 with approved therapeutics were evaluated in preclinical models of EOC. Combinations of IMGN853 with carboplatin or doxorubicin resulted in synergistic antiproliferative effects in the IGROV-1 ovarian cancer cell line in vitro. IMGN853 potentiated the cytotoxic activity of carboplatin via growth arrest and augmented DNA damage; cell cycle perturbations were also observed in cells treated with the IMGN853/doxorubicin combination. These benefits translated into improved antitumor activity in patient-derived xenograft models in vivo in both the platinum-sensitive (IMGN853/carboplatin) and platinum-resistant (IMGN853/pegylated liposomal doxorubicin) settings. IMGN853 co-treatment also improved the in vivo efficacy of bevacizumab in platinum-resistant EOC models, with combination regimens causing significant regressions and complete responses in the majority of tumor-bearing mice. Histological analysis of OV-90 ovarian xenograft tumors revealed that concurrent administration of IMGN853 and bevacizumab caused rapid disruption of tumor microvasculature and extensive necrosis, underscoring the superior bioactivity profile of the combination regimen. Overall, these demonstrations of combinatorial benefit conferred by the addition of the first FRα-targeting ADC to established therapies provide a compelling framework for the potential application of IMGN853 in the treatment of patients with advanced ovarian cancer.

The pharmacogenomics of drug resistance to protein kinase inhibitors

Dysregulation of growth factor cell signaling is a major driver of most human cancers. This has led to development of numerous drugs targeting protein kinases, with demonstrated efficacy in the treatment of a wide spectrum of cancers. Despite their high initial response rates and survival benefits, the majority of patients eventually develop resistance to these targeted therapies. This review article discusses examples of established mechanisms of drug resistance to anticancer therapies, including drug target mutations or gene amplifications, emergence of alternate signaling pathways, and pharmacokinetic variation. This reveals a role for pharmacogenomic analysis to identify and monitor for resistance, with possible therapeutic strategies to combat chemoresistance.

Folylpoly-γ-glutamate synthetase: A key determinant of folate homeostasis and antifolate resistance in cancer

Mammalians are devoid of autonomous biosynthesis of folates and hence must obtain them from the diet. Reduced folate cofactors are B9-vitamins which play a key role as donors of one-carbon units in the biosynthesis of purine nucleotides, thymidylate and amino acids as well as in a multitude of methylation reactions including DNA, RNA, histone and non-histone proteins, phospholipids, as well as intermediate metabolites. The products of these S-adenosylmethionine (SAM)-dependent methylations are involved in the regulation of key biological processes including transcription, translation and intracellular signaling. Folate-dependent one-carbon metabolism occurs in several subcellular compartments including the cytoplasm, mitochondria, and nucleus. Since folates are essential for DNA replication, intracellular folate cofactors play a central role in cancer biology and inflammatory autoimmune disorders. In this respect, various folate-dependent enzymes catalyzing nucleotide biosynthesis have been targeted by specific folate antagonists known as antifolates. Currently, antifolates are used in drug treatment of multiple human cancers, non-malignant chronic inflammatory disorders as well as bacterial and parasitic infections. An obligatory key component of intracellular folate retention and intracellular homeostasis is (anti)folate polyglutamylation, mediated by the unique enzyme folylpoly-γ-glutamate synthetase (FPGS), which resides in both the cytoplasm and mitochondria. Consistently, knockout of the FPGS gene in mice results in embryonic lethality. FPGS catalyzes the addition of a long polyglutamate chain to folates and antifolates, hence rendering them polyanions which are efficiently retained in the cell and are now bound with enhanced affinity by various folate-dependent enzymes. The current review highlights the crucial role that FPGS plays in maintenance of folate homeostasis under physiological conditions and delineates the plethora of the molecular mechanisms underlying loss of FPGS function and consequent antifolate resistance in cancer.

Soft Interaction in Liposome Nanocarriers for Therapeutic Drug Delivery

The development of smart nanocarriers for the delivery of therapeutic drugs has experienced considerable expansion in recent decades, with the development of new medicines devoted to cancer treatment. In this respect a wide range of strategies can be developed by employing liposome nanocarriers with desired physico-chemical properties that, by exploiting a combination of a number of suitable soft interactions, can facilitate the transit through the biological barriers from the point of administration up to the site of drug action. As a result, the materials engineer has generated through the bottom up approach a variety of supramolecular nanocarriers for the encapsulation and controlled delivery of therapeutics which have revealed beneficial developments for stabilizing drug compounds, overcoming impediments to cellular and tissue uptake, and improving biodistribution of therapeutic compounds to target sites. Herein we present recent advances in liposome drug delivery by analyzing the main structural features of liposome nanocarriers which strongly influence their interaction in solution. More specifically, we will focus on the analysis of the relevant soft interactions involved in drug delivery processes which are responsible of main behaviour of soft nanocarriers in complex physiological fluids. Investigation of the interaction between liposomes at the molecular level can be considered an important platform for the modeling of the molecular recognition processes occurring between cells. Some relevant strategies to overcome the biological barriers during the drug delivery of the nanocarriers are presented which outline the main structure-properties relationships as well as their advantages (and drawbacks) in therapeutic and biomedical applications.

Development of a Novel Covalent Folate-Albumin-Photosensitizer Conjugate

There is considerable interest in the development of novel and more efficient delivery systems for improving the efficacy of photodynamic therapy (PDT). The authors in this highlighted issue describe the synthesis and the photobiological characterizations of two photosensitizer (PS) conjugates based on β-carboline derivatives covalently conjugated to folic acid (FA) coupled to bovine serum albumin (BSA) as a carrier system specifically targeting cancer cells overexpressing FA receptor alpha (FRα). Accordingly, only the FA-BSA-β-carboline conjugates are internalized specifically in FRα-positive cells and are proved to be phototoxic. On the other hand, albumin-β-carboline conjugates without FA or β-carboline derivatives alone are not internalized and nontoxic. This conjugate is among the first to produce a conjugate composed of a PS and FA molecules that are directly conjugated to BSA. In addition, the in vitro studies are the first evidence that directly conjugated FA-BSA can be used as carriers to selectively enhance cytotoxicity by PDT relative to unmodified PS or nontargeted BSA-PS. This strategy is a positive step forward for the covalent design and construction of a photodynamic nanomedicine for FR-positive tumors.

Are nanotheranostics and nanodiagnostics-guided drug delivery stepping stones towards precision medicine?

The progress in medical research has led to the understanding that cancer is a large group of heterogeneous diseases, with high variability between and within individuals. This variability sprouted the ambitious goal to improve therapeutic outcomes, while minimizing drug adverse effects through stratification of patients by the differences in their disease markers, in a personalized manner, as opposed to the strategy of "one therapy fits all". Nanotheranostics, composed of nanoparticles (NPs) carrying therapeutic and/or diagnostics probes, have the potential to revolutionize personalized medicine. There are different modalities to combine these two distinct fields into one system for a synergistic outcome. The addition of a nanocarrier to a theranostic system holds great promise. Nanocarriers possess high surface area, enabling sophisticated functionalization with imaging agents, thus gaining enhanced diagnostic ability in real-time. Yet, most of the FDA-approved theranostic approaches are based on small molecules. The theranostic approaches that are reviewed herein are paving the road towards personalized medicine through all stages of patient care: starting from screening and diagnostics, proceeding to treatment and ending with treatment follow-up. Our current review provides a broad background and highlights new insights for the rational design of theranostic nanosystems for desired therapeutic niches, while summoning the hurdles on their way to become first-line diagnostics and therapeutics for cancer patients.

Assessment of folate receptor-β expression in human neoplastic tissues

Over-expression of folate receptor alpha on cancer cells has been frequently exploited for delivery of folate-targeted imaging and therapeutic agents to tumors. Because limited information exists on expression of the beta isoform of the folate receptor in human cancers (FR-β), we have evaluated the immunohistochemical staining pattern of FR-β in 992 tumor sections from 20 different human cancer types using a new anti-human FR-β monoclonal antibody. FR-β expression was shown to be more pronounced in cells within the stroma, primarily macrophages and macrophage-like cells than cancer cells in every cancer type studied. Moreover, FR-β expression in both cancer and stromal cells was found to be statistically more prominent in females than males. A significant positive correlation was also observed between FR-β expression on stromal cells and both the stage of the cancer and the presence of lymph node metastases. Based on these data we conclude FR-β may constitute a good target for specific delivery of therapeutic agents to activated macrophages and that accumulation of FR-β positive macrophages in the stroma could serve as a useful indicator of a tumor's metastatic potential.

(64)Cu- and (68)Ga-Based PET Imaging of Folate Receptor-Positive Tumors: Development and Evaluation of an Albumin-Binding NODAGA-Folate

A number of folate-based radioconjugates have been synthesized and evaluated for nuclear imaging purposes of folate receptor (FR)-positive tumors and potential therapeutic application. A common shortcoming of radiofolates is, however, a significant accumulation of radioactivity in the kidneys. This situation has been faced by modifying the folate conjugate with an albumin-binding entity to increase the circulation time of the radiofolate, which led to significantly improved tumor-to-kidney ratios. The aim of this study was to develop an albumin-binding folate conjugate with a NODAGA-chelator (rf42) for labeling with (64)Cu and (68)Ga, allowing application for PET imaging. The folate conjugate rf42 was synthesized in 8 steps, with an overall yield of 5%. Radiolabeling with (64)Cu and (68)Ga was carried out at room temperature within 10 min resulting in (64)Cu-rf42 and (68)Ga-rf42 with >95% radiochemical purity. (64)Cu-rf42 and (68)Ga-rf42 were stable (>95% intact) in phosphate-buffered saline over more than 4 half-lives of the corresponding radionuclide. In vitro, the plasma protein-bound fraction of (64)Cu-rf42 and (68)Ga-rf42 was determined to be >96%. Cell experiments proved FR-specific uptake of both radiofolates, as it was reduced to <1% when KB tumor cells were coincubated with excess folic acid. In vivo, high accumulation of (64)Cu-rf42 and (68)Ga-rf42 was found in KB tumors of mice (14.52 ± 0.99% IA/g and 11.92 ± 1.68% IA/g, respectively) at 4 h after injection. The tumor-to-kidney ratios were in the range of 0.43-0.55 over the first 4 h of investigation. At later time points (up to 72 h p.i. of (64)Cu-rf42) the tumor-to-kidney ratio increased to 0.73. High-quality PET/CT images were obtained 2 h after injection of (64)Cu-rf42 and (68)Ga-rf42, respectively, allowing distinct visualization of tumors and kidneys. Comparison of PET/CT images obtained with (64)Cu-rf42 and a (64)Cu-labeled DOTA-folate conjugate (cm10) clearly proved the superiority of NODAGA for stable coordination of (64)Cu. (64)Cu-cm10 showed high liver uptake, most probably as a consequence of released (64)Cu(2+). The data reported in this study clearly proved the promising features of (64)Cu-rf42, particularly in terms of favorable tumor-to-kidney ratios. The relatively long half-life of (64)Cu (T1/2 = 12.7 h) matches well with the enhanced circulation time of the albumin-binding NODAGA-folate, allowing PET imaging at longer time points after injection than is possible when using (68)Ga (T1/2 = 68 min).

Long non-coding RNAs: An emerging powerhouse in the battle between life and death of tumor cells

Long non-coding RNAs (lncRNAs) represent a class of non-protein coding transcripts longer than 200 nucleotides that have aptitude for regulating gene expression at the transcriptional, post-transcriptional or epigenetic levels. In recent years, lncRNAs, which are believed to be the largest transcript class in the transcriptomes, have emerged as important players in a variety of biological processes. Notably, the identification and characterization of numerous lncRNAs in the past decade has revealed a role for these molecules in the regulation of cancer cell survival and death. It is likely that this class of non-coding RNA constitutes a critical contributor to the assorted known or/and unknown mechanisms of intrinsic or acquired drug resistance. Moreover, the expression of lncRNAs is altered in various patho-physiological conditions, including cancer. Therefore, lncRNAs represent potentially important targets in predicting or altering the sensitivity or resistance of cancer cells to various therapies. Here, we provide an overview on the molecular functions of lncRNAs, and discuss their impact and importance in cancer development, progression, and therapeutic outcome. We also provide a perspective on how lncRNAs may alter the efficacy of cancer therapy and the promise of lncRNAs as novel therapeutic targets for overcoming chemoresistance. A better understanding of the functional roles of lncRNA in cancer can ultimately translate to the development of novel, lncRNA-based intervention strategies for the treatment or prevention of drug-resistant cancer.

Targeting Nonsquamous Nonsmall Cell Lung Cancer via the Proton-Coupled Folate Transporter with 6-Substituted Pyrrolo[2,3-d]Pyrimidine Thienoyl Antifolates

Pemetrexed (PMX) is a 5-substituted pyrrolo[2,3-d]pyrimidine antifolate used for therapy of nonsquamous nonsmall cell lung cancer (NS-NSCLC). PMX is transported by the reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT). Unlike RFC, PCFT is active at acidic pH levels characterizing the tumor microenvironment. By real-time reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry, PCFT transcripts and proteins were detected in primary NS-NSCLC specimens. In six NS-NSCLC cell lines (A549, H1437, H460, H1299, H1650, and H2030), PCFT transcripts and proteins were detected by real-time RT-PCR and western blots, respectively. 6-Substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates related to PMX [compound 1 (C1) and compound 2 (C2), respectively] are selective substrates for PCFT over RFC. In the NS-NSCLC cell lines, both [(3)H]PMX and [(3)H]C2 were transported by PCFT. C1 and C2 inhibited proliferation of the NS-NSCLC cell lines; A549, H460, and H2030 cells were more sensitive to C1 than to PMX. C1 and C2 inhibited glycinamide ribonucleotide formyltransferase in de novo purine nucleotide biosynthesis. When treated at pH 6.8, which favors PCFT uptake, C1 and C2 inhibited clonogenicity of H460 cells greater than PMX; PMX inhibited clonogenicity more than C1 or C2 at pH 7.2, which favors RFC transport over PCFT. Knockdown of PCFT in H460 cells resulted in decreased [(3)H]PMX and [(3)H]C2 transport and decreased growth inhibition by C1 and C2, and to a lesser extent by PMX. In vivo efficacy of C1 was seen toward H460 tumor xenografts in severe-combined immunodeficient mice. Our results suggest that 6-substituted pyrrolo[2,3-d]pyrimidine thienoyl antifolates offer significant promise for treating NS-NSCLC by selective uptake by PCFT.

Biomarkers of in vivo fluorescence imaging in allergic airway inflammation

Airway inflammation is a central component of the manifestation of asthma but is relatively inaccessible to study. Current imaging techniques such as X-ray CT, MRI, and PET, have advanced noninvasive research on pulmonary diseases. However, these techniques mainly facilitate the anatomical or structural assessment of the diseased lung and/or typically use radioactive agents. In vivo fluorescence imaging is a novel method for noninvasive, real-time, and specific monitoring of lung airway inflammation, which is particularly important to gain a further understanding asthma. Compared to conventional techniques, fluorescent imaging has the advantages of rapid feedback, as well as high sensitivity and resolution. Recently, there has been an increase in the identification of biomarkers, including matrix metalloproteinases, cathepsins, selectins, folate receptor-beta, nanoparticles, as well as sialic acid-binding immunoglobulin-like lectin-F to assess the level of airway inflammation in asthma. Recent advances in our understanding of these biomarkers as molecular probes for in vivo imaging are discussed in this review.

Rational Design of Targeted Next-Generation Carriers for Drug and Vaccine Delivery

Pattern recognition receptors on innate immune cells play an important role in guiding how cells interact with the rest of the organism and in determining the direction of the downstream immune response. Recent advances have elucidated the structure and function of these receptors, providing new opportunities for developing targeted drugs and vaccines to treat infections, cancers, and neurological disorders. C-type lectin receptors, Toll-like receptors, and folate receptors have attracted interest for their ability to endocytose their ligands or initiate signaling pathways that influence the immune response. Several novel technologies are being developed to engage these receptors, including recombinant antibodies, adoptive immunotherapy, and chemically modified antigens and drug delivery vehicles. These active targeting technologies will help address current challenges facing drug and vaccine delivery and lead to new tools to treat human diseases.

Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance

Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.

Design of liposomal formulations for cell targeting

Liposomes have gained extensive attention as carriers for a wide range of drugs due to being both nontoxic and biodegradable as they are composed of substances naturally occurring in biological membranes. Active targeting for cells has explored specific modification of the liposome surface by functionalizing it with specific targeting ligands in order to increase accumulation and intracellular uptake into target cells. None of the Food and Drug Administration-licensed liposomes or lipid nanoparticles are coated with ligands or target moieties to delivery for homing drugs to target tissues, cells or subcellular organelles. Targeted therapies (with or without controlled drug release) are an emerging and relevant research area. Despite of the numerous liposomes reviews published in the last decades, this area is in constant development. Updates urgently needed to integrate new advances in targeted liposomes research. This review highlights the evolution of liposomes from passive to active targeting and challenges in the development of targeted liposomes for specific therapies.

Integration of imaging into clinical practice to assess the delivery and performance of macromolecular and nanotechnology-based oncology therapies

Functional and molecular imaging has become increasingly used to evaluate interpatient and intrapatient tumor heterogeneity. Imaging allows for assessment of microenvironment parameters including tumor hypoxia, perfusion and proliferation, as well as tumor metabolism and the intratumoral distribution of specific molecular markers. Imaging information may be used to stratify patients for targeted therapies, and to define patient populations that may benefit from alternative therapeutic approaches. It also provides a method for non-invasive monitoring of treatment response at earlier time-points than traditional cues, such as tumor shrinkage. Further, companion diagnostic imaging techniques are becoming progressively more important for development and clinical implementation of targeted therapies. Imaging-based companion diagnostics are likely to be essential for the validation and FDA approval of targeted nanotherapies and macromolecular medicines. This review describes recent clinical advances in the use of functional and molecular imaging to evaluate the tumor microenvironment. Additionally, this article focuses on image-based assessment of distribution and anti-tumor effect of nano- and macromolecular systems.

Strategies of polymeric nanoparticles for enhanced internalization in cancer therapy

In order to achieve long circulation time and high drug accumulation in the tumor sites via the EPR effects, anticancer drugs have to be protected by non-fouling polymers such as poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO), dextran, and poly(acrylic acid) (PAA). However, the dense layer of stealth polymer also prohibits efficient uptake of anticancer drugs by target cancer cells. For cancer therapy, it is often more desirable to accomplish rapid cellular uptake after anticancer drugs arriving at the pathological site, which could on one hand maximize the therapeutic efficacy and on the other hand reduce probability of drug resistance in cells. In this review, special attention will be focused on the recent potential strategies that can enable drug-loaded polymeric nanoparticles to rapidly recognize cancer cells, leading to enhanced internalization.

Cysteine cathepsins: their role in tumor progression and recent trends in the development of imaging probes

Papain-like cysteine proteases bear an enormous potential as drug discovery targets for both infectious and systemic human diseases. The considerable progress in this field over the last two decades has also raised interest in the visualization of these enzymes in their native context, especially with regard to tumor imaging. After a short introduction to structure and general functions of human cysteine cathepsins, we highlight their importance for drug discovery and development and provide a critical update on the current state of knowledge toward their involvement in tumor progression, with a special emphasis on their role in therapy response. In accordance with a radiopharmaceutical point of view, the main focus of this review article will be the discussion of recently developed fluorescence and radiotracer-based imaging agents together with related molecular probes.

CrkL meditates CCL20/CCR6-induced EMT in gastric cancer

BACKGROUND

In recent years, Crk-like adapter protein (CrkL) has been identified as a key regulator in the epithelial-to-mesenchymal transition (EMT). However, the molecular mechanisms underlying the CC chemokine receptor 6 (CCR6) and chemokine (C-C motif) ligand 20 (CCL20)-induced EMT in gastric cancer are still unclear.

METHODS

We conducted the immunohistochemistry and immunoblotting to detect the expression of CCR6 and CrkL in 90 cases of gastric cancer tissues and five kinds of cell lines. And then, gastric cancer cells were subjected to small interfering RNA (siRNA) treatment and in vitro assay.

RESULTS

Both CCR6 and CrkL were aberrantly expressed in gastric cancer specimens and closely correlated with differentiation of cell lines. The expression of CCR6 and CrkL was also significantly associated with metastasis, stage, and poor prognosis of gastric cancer. In addition, we validated CCL20 activated the expression of p-CrkL, p-Erk1/2, p-Akt, vimentin, N-cadherin and MMP2 in MGC803 cells in a dose-dependent manner. However, si-CrkL abrogated the CCL20-induced p-Erk1/2, vimentin, N-cadherin and MMP2 expression. Most importantly, the knockdown of CrkL decreased migration and invasion of MGC803 cells.

CONCLUSIONS

CrkL mediates CCL20/CCR6-induced EMT via Akt pathway, instead of Erk1/2 pathway in development of gastric cancer, which indicated CCL20/CCR6-CrkL-Erk1/2-EMT pathway may be targeted to antagonize the progression of gastric cancer.

Novel insights in folate receptors and transporters: implications for disease and treatment of immune diseases and cancer

Folate receptors and transporters as well as folate enzymes play an essential role in human disease and form important targets for the treatment of immune diseases and cancer. To discuss new developments in this area, every 2 years a multidisciplinary meeting is held, which aims to be an informal forum for fundamental scientists and clinicians. During this meeting, the regulation of folate transporters and folate enzymes is discussed at the level of expression, transcription, translation, post-translational modification, and splicing and enzyme regulation. Importantly, this knowledge is applied and translated into exciting clinical applications by clinicians with various backgrounds, such as surgeons, nephrologists, rheumatologists and oncologists. Moreover, the meeting provides an excellent forum for a scientific interaction between academia and industry.

C23 protein meditates bone morphogenetic protein-2-mediated EMT via up-regulation of Erk1/2 and Akt in gastric cancer

In our previous study, the epithelial-to-mesenchymal transition (EMT) has been identified to be involved in gastric cancer progression. Notably, nuclear protein C23 and bone morphogenetic protein-2 (BMP2) have been linked into EMT. However, the specific mechanisms underlying BMP2 pathway-mediated EMT are not still unraveled. In this study, we adopted immunohistochemistry and immunoblotting to determine the expression of C23 and BMP2 receptor II (BMPR-II) in 90 gastric cancer samples and cell lines. Subsequently, relevant cell lines were selected to be treated with si-C23 or si-BMPRII and the detection of in vitro assay. Our results revealed that both C23 and BMPRII were aberrantly and constitutively expressed in gastric cancer specimens and cell lines, whose expression was positively associated with metastasis, stage and differentiation, and portended poor survival outcome of gastric cancer patients. In vitro assay validated the increased expression of p-Erk1/2, p-Akt, vimentin, N-cadherin, and MMP2 in BMP2-stimulated MGC803 cells, which was in a dose-dependent manner. By contrast, si-C23 treatment attenuated the BMP2-stimulated expression of p-Erk1/2, p-Akt, vimentin, N-cadherin, and MMP2. Also, the treatment of either si-C23 or si-BMPRII decreased the ability of migration and invasion of MGC803 cells. In conclusion, C23 mediates BMP2-induced EMT progression via the up-regulation of Erk1/2 and Akt signaling pathway in gastric cancer, which indicated both C23 and BMPRII pathway could be recommended as prospective targets or biomarkers to antagonize the progression of gastric cancer.

Synthesis and antitumor activity of a novel series of 6-substituted pyrrolo[2,3-d]pyrimidines as potential nonclassical antifolates targeting both thymidylate and purine nucleotide biosynthesis

A novel series of 2-amino-4-oxo-6-substituted pyrrolo[2,3-d]pyrimidines were designed and synthesized as potential nonclassical antifolates targeting both thymidylate and purine nucleotide biosynthesis. Condensation of 2,4-diamino-6-hydroxypyrimidine with ethyl-4-chloroacetoacetate and subsequent hydrolysis afforded the key intermediate, 2-amino-4-oxo-pyrrolo[2,3-d]pyrimidin-6-yl-acetic acid. Coupling with various amino acid methyl esters followed by saponification and condensation with 3-(aminomethyl)pyridine provided target compounds 1-9. The new compounds exhibited micromolar to submicromolar antiproliferative potencies against a panel of tumor cell lines including KB, A549 and HepG2. Growth inhibition of compound 2 toward KB cells resulted in cytotoxicity and G1/G2-phase accumulation, and was partially protected by excess thymidine and adenosine, but was completely reversed in the combination of thymidine and adenosine, indicating both thymidylate and de novo purine nucleotide synthesis as the targeted pathway. However, 5-aminoimidazole-4-carboxamide (AICA) protection was incomplete, suggesting inhibition of both glycinamide ribonucleotide formyltransferase (GARFTase) and AICA ribonucleotide formyltransferase (AICARFTase). The results of the docking studies show that 2 could bind and inhibit both thymidylate synthase (TS) and the two folate-dependent purine biosynthetic enzymes (GARFTase and AICARFTase), which is consistent with the results of in vitro metabolic assays. Our studies establish that compound 2 is an excellent lead analog as a multitargeted antifolate for further structure optimization.

CCR7 pathway induces epithelial-mesenchymal transition through up-regulation of Snail signaling in gastric cancer

The chemokine receptor 7 (CCR7) and Snail signaling have been linked to various types of cancers. The associations between these signalings and the epithelial-mesenchymal transition (EMT) are not clear in gastric cancer. Here, the expression of CCR7 and Snail was detected in gastric cancer by immunohistochemistry and Western blot. Meanwhile, gastric cancer cells were subjected to CCL19, si-control, and si-Snail treatment. Cell cycle, migration, and invasion were also analyzed. The expression patterns of CCR7 and Snail were similar in either gastric cancer tissues or cells. The increased expression of CCR7 was closely associated with the increased Snail expression, which both were closely correlated with metastasis, stage and differentiation, and poor prognosis. The increased p-ERK, p-AKT, Snail, and MMP9 expression and the decreased E-cadherin were confirmed in MGC803 cells in a dose-dependent manner in response to CCL19 treatment. However, the blockade of Snail abrogated the up-regulation of MMP9 and down-regulation of E-cadherin. CCR7-induced ERK and PI3K pathway regulated Snail signaling. Besides si-Snail treatment led to MGC803 cell cycle arrest and affected the migration and invasion. In conclusion, our study suggested that CCR7 promotes Snail expression to induce the EMT, resulting in cell cycle progression, migration, and invasion in gastric cancer. CCR7-Snail pathway provided more potential regimens for cancer therapy.

Host effects contributing to cancer therapy resistance

There are several approaches for the management of malignant disease. However, tumor resistance to therapy is still a major challenge in the clinic. Efflux transporters, genetic responses and enzyme activity in tumor cells are examples of the main modalities that account for resistance to therapy. In addition, emerging evidence suggests that the host also plays a significant role in promoting therapy resistance. Recruitment of different host cell types to the treated tumor site occurs in response to a range of therapies, including chemotherapy, radiation and even targeted drugs. This host response may have a protective effect on the tumor cells, not only negating anti-tumor activity, but also promoting a resistant tumor. In this review, we focus on host-tumor interactions leading to therapy resistance with special emphasis on different host cells and secreted factors within the tumor microenvironment. The development of novel inhibitors that block the host response to therapy could be used as a treatment strategy to enhance therapy outcomes and survival.