Platinum(IV) complexes conjugated with phenstatin analogue as inhibitors of microtubule polymerization and reverser of multidrug resistance

Pt(IV) Complexes in the Search for Novel Platinum Prodrugs with Promising Activity

The kinetically inert, six coordinated, octahedral Pt(IV) complexes are termed dual-, triple-, or multi-action prodrugs based on the nature of the axially substituted ligands. These ligands are either inert or biologically active, where the nature of these axial ligands provides additional stability, synergistic biological activity or cell-targeting ability. There are many literature reports from each of these classes, mentioning the varied nature of these axial ligands. The ligands comprise drug molecules such as chlorambucil, doxorubicin, valproic acid, ethacrynic acid, biologically active chalcone, coumarin, combretastatin, non-steroidal anti-inflammatory drugs (NSAIDs) and many more, potentiating the anti-proliferative profile or reducing the side effects associated with cisplatin therapy. The targeting and non-targeting nature of these moieties exert additive or synergistic effects on the anti-cancer activity of Pt(II) moieties. Herein, we discuss the effects of these axially oriented ligands and the changes in the non-leaving am(m)ine groups and in the leaving groups on the biological activity. In this review, we have presented the latest developments in the field of Pt(IV) complexes that display promising activity with a reduced resistance profile. We have discussed the structure activity relationship (SAR) and the effects of the ligands on the biological activity of Pt(IV) complexes with cisplatin, oxaliplatin, carboplatin and the Pt core other than approved drugs. This literature work will help researchers to get an idea about Pt(IV) complexes that have been classified based on the aspects of their biological activity.

Exploring the Potential of Metal-Based Candidate Drugs as Modulators of the Cytoskeleton

During recent years, accumulating evidence suggested that metal-based candidate drugs are promising modulators of cytoskeletal and cytoskeleton-associated proteins. This was substantiated by the identification and validation of actin, vimentin and plectin as targets of distinct ruthenium(II)- and platinum(II)-based modulators. Despite this, structural information about molecular interaction is scarcely available. Here, we compile the scattered reports about metal-based candidate molecules that influence the cytoskeleton, its associated proteins and explore their potential to interfere in cancer-related processes, including proliferation, invasion and the epithelial-to-mesenchymal transition. Advances in this field depend crucially on determining binding sites and on gaining comprehensive insight into molecular drug-target interactions. These are key steps towards establishing yet elusive structure-activity relationships.

Recent advances of benzimidazole as anticancer agents

Cancer is the second leading cause of death globally, with 9.6 million deaths yearly. As a life-threatening disease, it necessitates the emergence of new therapies. Resistance to current chemotherapies drives scientists to develop new medications that will eventually be accessible. Because heterocycles are so common in biological substances, compounds play a big part in the variety of medications that have been developed. The "Master Key" is the benzimidazole nucleus, which consists of a six-membered benzene ring fused with a five-membered imidazole/imidazoline ring, which is an azapyrrole. One of the five-membered aromatic nitrogen heterocycles identified in American therapies that have been approved by the Food and Drug Administration (FDA). Our results show that benzimidazole's broad therapeutic spectrum is due to its structural isosteres with purine, which improves hydrogen bonding, electrostatic interactions with topoisomerase complexes, intercalation with DNA, and other functions. It also enhances protein and nucleic acid inhibition, tubulin microtubule degeneration, apoptosis, DNA fragmentation, and other functions. Additionally, readers for designing the more recent benzimidazole analogues as prospective cancer treatments.

Developing a Novel Indium(III) Agent Based on Liposomes to Overcome Cisplatin-Induced Resistance in Breast Cancer by Multitargeting the Tumor Microenvironment Components

To overcome the resistance of cancer cells to platinum-based drugs and effectively suppress tumor growth, we developed a novel indium (In) agent based on liposomes (Lips). Thus, we not only obtained an In(III) thiosemicarbazone agent (5b) with remarkable cytotoxicity by optimizing a series of In(III) thiosemicarbazone agents (1b-5b) but also successfully constructed a novel 5b-loaded Lip (5b-Lip) delivery system. Importantly, in vitro and in vivo results revealed that 5b/5b-Lip overcame the tumor cell resistance and effectively inhibited MCF-7/DDP tumor growth. In addition, Lips improved the intracellular accumulation of 5b. We also confirmed the mechanism by which 5b/5b-Lip overcomes breast cancer cell resistance. 5b/5b-Lip cannot act against DNA in cancer cells but attacks the two cell components in the tumor microenvironment, namely, by inducing apoptosis and lethal autophagy of cancer cells and resetting tumor-promoting M2 macrophages to the tumor-killing M1 phenotype.

Hybrid Drugs-A Strategy for Overcoming Anticancer Drug Resistance?

Despite enormous progress in the treatment of many malignancies, the development of cancer resistance is still an important reason for cancer chemotherapy failure. Increasing knowledge of cancers' molecular complexity and mechanisms of their resistance to anticancer drugs, as well as extensive clinical experience, indicate that an effective fight against cancer requires a multidimensional approach. Multi-target chemotherapy may be achieved using drugs combination, co-delivery of medicines, or designing hybrid drugs. Hybrid drugs simultaneously targeting many points of signaling networks and various structures within a cancer cell have been extensively explored in recent years. The single hybrid agent can modulate multiple targets involved in cancer cell proliferation, possesses a simpler pharmacokinetic profile to reduce the possibility of drug interactions occurrence, and facilitates the process of drug development. Moreover, a single medication is expected to enhance patient compliance due to a less complicated treatment regimen, as well as a diminished number of adverse reactions and toxicity in comparison to a combination of drugs. As a consequence, many efforts have been made to design hybrid molecules of different chemical structures and functions as a means to circumvent drug resistance. The enormous number of studies in this field encouraged us to review the available literature and present selected research results highlighting the possible role of hybrid drugs in overcoming cancer drug resistance.

Pt(IV) Prodrugs with NSAIDs as Axial Ligands

A chemo-anti-inflammatory strategy is of interest for the treatment of aggressive cancers. The platinum (IV) prodrug with non-steroidal anti-inflammatory drugs (NSAIDs) as axial ligands is designed to efficiently enter tumor cells due to high lipophilicity and release the cytotoxic metabolite and NSAID intracellularly, thereby reducing side effects and increasing the therapeutic efficacy of platinum chemotherapy. Over the last 7 years, a number of publications have been devoted to the design of such Pt(IV) prodrugs in combination with anti-inflammatory chemotherapy, with high therapeutic efficacy in vitro and In vivo. In this review, we summarize the studies devoted to the development of Pt(IV) prodrugs with NSAIDs as axial ligands, the study of the mechanism of their cytotoxic action and anti-inflammatory activity, the structure-activity ratio, and therapeutic efficacy.

Disruption of the Microtubule Network and Inhibition of VEGFR2 Phosphorylation by Cytotoxic N,O-Coordinated Pt(II) and Ru(II) Complexes of Trimethoxy Aniline-Based Schiff Bases

Platinum-based complexes are one of the most successful chemotherapeutic agents having a significant ground in cancer chemotherapy despite their side effects. During the past few decades, Ru(II) complexes have been emerging as efficient alternatives owing to their promising activities against platinum-resistant cancer. The pathway of action, lipophilicity, and cytotoxicity of a Pt or Ru complex may be tuned by varying the attached ligands, the coordination mode, and the leaving group. In this work, we report a family of Pt(II) and Ru(II) complexes (1-5) of three N,O and N,N donor-based trimethoxyanilines containing Schiff bases with the general formula [Pt^II(L)(DMSO)Cl], [Ru^II(L)(p-cymene)Cl], [Ru^II(L)(p-cymene)Cl]⁺, and [Pt^II(L)Cl₂]. All of the complexes are characterized by different analytical techniques. ¹H NMR and electrospray ionization mass spectrometry (ESI-MS) data suggest that the N,O-coordinated Pt(II) complexes undergo slower aquation compared to the Ru(II) analogues. The change of the coordination mode to N,N causes the Ru complexes to be more inert to aquation. The N,O-coordinating complexes show superiority over N,N-coordinating complexes by displaying excellent in vitro antiproliferative activity against different aggressive cancer cells, viz., triple-negative human metastatic breast adenocarcinoma MDA-MB-231, human pancreatic carcinoma MIA PaCa-2, and hepatocellular carcinoma Hep G2. In vitro cytotoxicity studies suggest that Pt(II) complexes are more effective than their corresponding Ru(II) analogues, and the most cytotoxic complex 3 is 10-15 times more toxic than the clinical drugs cisplatin and oxaliplatin against MDA-MB-231 cells. Cellular studies show that all of the N,O-coordinated complexes (1-3) initiate disruption of the microtubule network in MDA-MB-231 cells in a dose-dependent manner within 6 h of incubation and finally lead to the arrest of the cell cycle in the G2/M phase and render apoptotic cell death. The disruption of the microtubule network affects the agility of the cytoskeleton rendering inhibition of tyrosine phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2), a key step in angiogenesis. Complexes 1 and 2 inhibit VEGFR2 phosphorylation in a dose-dependent fashion. Among the Pt(II) and Ru(II) complexes, the former displays higher cytotoxicity, a stronger effect on the cytoskeleton, better VEGFR2 inhibition, and strong interaction with the model nucleobase 9-ethylguanine (9-EtG).

Cytotoxic substituted indolizines as new colchicine site tubulin polymerisation inhibitors

A potential microtubule destabilising series of new indolizine derivatives was synthesised and tested for their anticancer activity against a panel of 60 human cancer cell lines. Compounds 11a, 11b, 15a, and 15j showed a broad spectrum of growth inhibitory activity against cancer cell lines representing leukaemia, melanoma and cancer of lung, colon, central nervous system, ovary, kidney, breast, and prostate. Among them, compound 11a was distinguishable by its excellent cytostatic activity, showing GI50 values in the range of 10-100 nM on 43 cell lines. The less potent compounds 15a and 15j in terms of GI50 values showed a high cytotoxic effect against tested colon cancer, CNS cancer, renal cancer and melanoma cell lines and only on few cell lines from other types of cancer. In vitro assaying revealed tubulin polymerisation inhibition by all active compounds. Molecular docking showed good complementarity of active compounds with the colchicine binding site of tubulin.

Platinum(IV)-Estramustine Multiaction Prodrugs Are Effective Antiproliferative Agents against Prostate Cancer Cells

Herein, we describe the synthesis, characterization, and biological properties of Pt(IV) derivatives of cisplatin with estramustine at the first axial position, which is known to disrupt the microtubule assembly and act as an androgen antagonist, and varying the second axial position using an innocent ligand (acetate or hydroxyl) to prepare dual-action and triple-action prodrugs with known inhibitors of histone deacetylase, cyclooxygenase, and pyruvate dehydrogenase kinase. We demonstrate superior antiproliferative activity at submicromolar concentrations of the prodrugs against a panel of cancer cell lines, particularly against prostate cancer cell lines. The results obtained in this study exemplify the complex mode of action of "multiaction" Pt(IV) prodrugs. Interestingly, changing the second axial ligand in the Pt-estramustine complex has a significant effect on the mode of action, suggesting that all three components of the Pt(IV) prodrugs (platinum moiety and axial ligands) contribute to the killing of cells and not just one dominant component.

Drug resistance in cancer: mechanisms and tackling strategies

Drug resistance developed towards conventional therapy is one of the important reasons for chemotherapy failure in cancer. The various underlying mechanism for drug resistance development in tumor includes tumor heterogeneity, some cellular levels changes, genetic factors, and others novel mechanisms which have been highlighted in the past few years. In the present scenario, researchers have to focus on these novel mechanisms and their tackling strategies. The small molecules, peptides, and nanotherapeutics have emerged to overcome the drug resistance in cancer. The drug delivery systems with targeting moiety enhance the site-specificity, receptor-mediated endocytosis, and increase the drug concentration inside the cells, thus minimizing drug resistance and improve their therapeutic efficacy. These therapeutic approaches work by modulating the different pathways responsible for drug resistance. This review focuses on the different mechanisms of drug resistance and the recent advancements in therapeutic approaches to improve the sensitivity and effectiveness of chemotherapeutics.

Is the Way to Fight Cancer Paved with Gold? Metal-Based Carbene Complexes with Multiple and Fascinating Biological Features

Herein, we report the synthesis and the multiple anti-tumor properties of new gold and silver carbene complexes. The chemical modifications, grounded on our previous studies, led us to identify a good lead complex, gold-based, whose biological features are very exciting and promising in the anti-cancer research and could be further developed. Indeed, the bis-[4,5-dichloro-(N-methyl-N’(2-hydroxy-2-phenyl)ethyl-imidazole-2-ylidene)gold(I)]⁺[dichloro-gold]⁻ (AuL7) complex possesses the ability to interfere with at least three important and different intracellular targets, namely the human topoisomerases I and II and tubulin, which are able to modulate metabolic processes not directly correlated each other. We proved that the modifications of the ligands structure in AuL7, with respect to another already published complex, i.e., bis-[4,5-dichloro-(N-methyl-N’(cyclopentane-2ol)-imidazole-2-ylidine)gold(I)]⁺[dichloro-gold]⁻ (AuL4), produce a different behavior toward tubulin-polymerization process, since AuL7 is a tubulin-polymerization inhibitor and AuL4 a stabilizer, with the final same result of hampering the tumor growth. Taken together, our outcomes designate AuL7 as a promising compound for the development of multi-targeted anti-cancer therapies.

Improvement of conventional anti-cancer drugs as new tools against multidrug resistant tumors

Multidrug resistance (MDR) is the dominant cause of the failure of cancer chemotherapy. The design of antitumor drugs that are able to evade MDR is rapidly evolving, showing that this area of biomedical research attracts great interest in the scientific community. The current review explores promising recent approaches that have been developed with the aim of circumventing or overcoming MDR. Encouraging results have been obtained in the investigation of the MDR-modulating properties of various classes of natural compounds and their analogues. Inhibition of P-gp or downregulation of its expression have proven to be the main mechanisms by which MDR can be surmounted. The use of hybrid molecules that are able to simultaneously interact with two or more cancer cell targets is currently being explored as a means to circumvent drug resistance. This strategy is based on the design of hybrid compounds that are obtained either by merging the structural features of separate drugs, or by conjugating two drugs or pharmacophores via cleavable/non-cleavable linkers. The approach is highly promising due to the pharmacokinetic and pharmacodynamic advantages that can be achieved over the independent administration of the two individual components. However, it should be stressed that the task of obtaining successful multivalent drugs is a very challenging one. The conjugation of anticancer agents with nitric oxide (NO) donors has recently been developed, creating a particular class of hybrid that can combat tumor drug resistance. Appropriate NO donors have been shown to reverse drug resistance via nitration of ABC transporters and by interfering with a number of metabolic enzymes and signaling pathways. In fact, hybrid compounds that are produced by covalently attaching NO-donors and antitumor drugs have been shown to elicit a synergistic cytotoxic effect in a variety of drug resistant cancer cell lines. Another strategy to circumvent MDR is based on nanocarrier-mediated transport and the controlled release of chemotherapeutic drugs and P-gp inhibitors. Their pharmacokinetics are governed by the nanoparticle or polymer carrier and make use of the enhanced permeation and retention (EPR) effect, which can increase selective delivery to cancer cells. These systems are usually internalized by cancer cells via endocytosis and accumulate in endosomes and lysosomes, thus preventing rapid efflux. Other modalities to combat MDR are described in this review, including the pharmaco-modulation of acridine, which is a well-known scaffold in the development of bioactive compounds, the use of natural compounds as means to reverse MDR, and the conjugation of anticancer drugs with carriers that target specific tumor-cell components. Finally, the outstanding potential of in silico structure-based methods as a means to evaluate the ability of antitumor drugs to interact with drug transporters is also highlighted in this review. Structure-based design methods, which utilize 3D structural data of proteins and their complexes with ligands, are the most effective of the in silico methods available, as they provide a prediction regarding the interaction between transport proteins and their substrates and inhibitors. The recently resolved X-ray structure of human P-gp can help predict the interaction sites of designed compounds, providing insight into their binding mode and directing possible rational modifications to prevent them from becoming P-gp drug substrates. In summary, although major efforts were invested in the search for new tools to combat drug resistant tumors, they all require further implementation and methodological development. Further investigation and progress in the abovementioned strategies will provide significant advances in the rational combat against cancer MDR.

Transition Metal-Based Prodrugs for Anticancer Drug Delivery

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Transition metal complexes, of which the platinum(II) complex cisplatin is an example, have been used in medicine to treat cancer for more than 40 years. Although many successes have been achieved, there are problems associated with the use of these drugs, such as side effects and drug resistance. Converting them into prodrugs, to make them more inert, so that they can travel to the tumour site unchanged and release the drug in its active form only there, is a strategy which is the subject of much research nowadays. The new prodrugs may be activated and release the cytotoxic agent by differences in oxygen concentration or in pH, by the action of overexpressed enzymes, by differences in metabolic rates, etc., which characteristically distinguish cancer cells from normal ones, or even by the input of radiation, which can be visible light. Converting a metal complex into a prodrug may also be used to improve its pharmacological properties. In some cases, the metal complex is a carrier which transports the active drug as a ligand. Some platinum prodrugs have reached clinical trials. So far platinum, ruthenium and cobalt have been the most studied metals. This review presents the recent developments in this area, including the types of complexes used, the mechanisms of drug action and in some cases the techniques applied to monitor drug delivery to cells.

Dual Inhibitors as a New Challenge for Cancer Multidrug Resistance Treatment

BACKGROUND

Dual-targeting in cancer treatment by a single drug is an unconventional approach in relation to drug combinations. The rationale for the development of dualtargeting agents is to overcome incomplete efficacy and drug resistance frequently present when applying individual targeting agents. Consequently, -a more favorable outcome of cancer treatment is expected with dual-targeting strategies.

METHODS

We reviewed the literature, concentrating on the association between clinically relevant and/or novel dual inhibitors with the potential to modulate multidrug resistant phenotype of cancer cells, particularly the activity of P-glycoprotein. A balanced analysis of content was performed to emphasize the most important findings and optimize the structure of this review.

RESULTS

Two-hundred and forty-five papers were included in the review. The introductory part was interpreted by 9 papers. Tyrosine kinase inhibitors' role in the inhibition of Pglycoprotein and chemosensitization was illustrated by 87 papers. The contribution of naturalbased compounds in overcoming multidrug resistance was reviewed using 92 papers, while specific dual inhibitors acting against microtubule assembling and/or topoisomerases were described with 55 papers. Eleven papers gave an insight into a novel and less explored approach with hybrid drugs. Their influence on P-glycoprotein and multidrug resistance was also evaluated.

CONCLUSION

These findings bring into focus rational anticancer strategies with dual-targeting agents. Most evaluated synthetic and natural drugs showed a great potential in chemosensitization. Further steps in this direction are needed for the optimization of anticancer treatment.

Synthesis, Structure, Stability, and Inhibition of Tubulin Polymerization by RuII-p-Cymene Complexes of Trimethoxyaniline-Based Schiff Bases

Four trimethoxy- and dimethoxyphenylamine-based Schiff base (L1-L4)-bearing Ru^II-p-cymene complexes (1-4) of the chemical formula [Ru^II(η⁶-p-cymene)(L)(Cl)] were synthesized, isolated in pure form, and structurally characterized using single-crystal X-ray diffraction and other analytical techniques. The complexes showed excellent in vitro antiproliferative activity against various forms of cancer that are difficult to cure, viz., triple negative human metastatic breast carcinoma MDA-MB-231, human pancreatic carcinoma MIA PaCa-2, and hepatocellular carcinoma Hep G2. The ¹H nuclear magnetic resonance data in the presence of 10% dimethylformamide-d₇ or dimethyl sulfoxide-d₆ in phosphate buffer (pD 7.4, containing 4 mM NaCl) showed that the complexes immediately generate the aquated species that is stable for at least 24 h. Electrospray ionization mass spectrometry data showed that they do not bind with guanine nitrogen even in the presence of 5 molar equivalents of 9-EtG, during a period of 24 h. The best complex in the series, 1, exhibits an IC₅₀ of approximately 10-15 μM in the panel of tested cancer cell lines. The complexes do not enhance the production of reactive oxygen species in the cells. Docking studies with a tubulin crystal structure (Protein Data Bank entry 1SAO ) revealed that 1 and 3 as well as L1 and L3 have a high affinity for the interface of the α and β tubulin dimer in the colchicine binding site. The immunofluorescence studies showed that 1 and 3 strongly inhibited microtubule network formation in MDA-MB-231 cells after treatment with an IC₂₀ or IC₅₀ dose for 12 h. The cell cycle analysis upon treatment with 1 showed that the complexes inhibit the mitotic phase because the arrest was observed in the G2/M phase. In summary, 1 and 3 are Ru^II half-sandwich complexes that are capable of disrupting a microtubule network in a dose-dependent manner. They depolarize the mitochondria, arrest the cell cycle in the G2/M phase, and kill the cells by an apoptotic pathway.

Emerging platinum(iv) prodrugs to combat cisplatin resistance: from isolated cancer cells to tumor microenvironment

Cisplatin plays a pivotal role in the treatment of various malignant tumors, but its therapeutic effects are hampered by drug resistance. Pt(iv) prodrugs represent a promising class of "non-conventional" platinum-based anticancer agents to circumvent drug resistance, which can be easily functionalized with other bioactive ligands. One strategy is to build "dual-action" and "multi-action" Pt(iv) prodrugs that not only damage DNA but also perturb other pathways related to cisplatin resistance to achieve combinatorial therapeutic effects. Another way to overcome the shortcomings of cisplatin is to deliver Pt(iv) prodrugs via nanocarriers. Most studies in this area have focused on designing prodrugs based on the mechanism of cisplatin resistance within isolated cancer cells. Recent findings, however, reveal that the tumor microenvironment also plays important roles in the development of cisplatin resistance. This perspective focuses on various types of novel cisplatin-based Pt(iv) complexes, including Pt-loaded nanostructures, to overcome cisplatin resistance. Special attention will be devoted to complexes that target the tumor microenvironment, which is a new area for the development of effective Pt(iv) prodrugs. Our summary and outlook may have a hope to help researchers in the field generate new ideas and strategies to develop more potent Pt(iv) prodrugs to combat cisplatin resistance.

A Subset of New Platinum Antitumor Agents Kills Cells by a Multimodal Mechanism of Action Also Involving Changes in the Organization of the Microtubule Cytoskeleton

The substitution inert platinum agent [Pt(1 S,2 S-diaminocyclohexane)(5,6-dimethyl-1,10-phenanthroline)]²⁺ (56MeSS, 5) is a potent cytotoxic metallodrug. In contrast to conventional cisplatin or oxaliplatin, the mechanism of action (MoA) of 5 is fundamentally different. However, details of the mechanism by which the 5,6-dimethyl-1,10-phenanthroline ligand contributes to the cytotoxicity of 5 and its derivatives have not been sufficiently clarified so far. Here, we show that 5 and its Pt(IV) derivatives exhibit an intriguing potency in the triple-negative breast cancer cells MDA-MB-231. Moreover, we show that the Pt(IV) derivatives of 5 act by multimodal MoA resulting in the global biological effects, that is, they damage nuclear DNA, reduce the mitochondrial membrane potential, induce the epigenetic processes, and last but not least, the data provide evidence that changes in the organization of cytoskeleton networks are functionally important for 5 and its derivatives, in contrast to clinically used platinum cytostatics, to kill cancer cells.

Current Developments in Pt(IV) Prodrugs Conjugated with Bioactive Ligands

To overcome the side effects of and resistance to cisplatin, a variety of Pt(IV) prodrugs were designed and synthesized via different modifications including combination with lipid chains to increase hydrophobicity, conjugation with short peptide chains or nanoparticles to improve drug delivery, or addition of bioactive ligands to the axial positions of Pt(IV) complexes to exert dual-function effects. This review summarizes the recent progress in the development of Pt(IV) prodrugs conjugated with bioactive-targeting ligands, including histone deacetylase inhibitors, p53 agonists, alkylating agents, and nonsteroidal anti-inflammatory agents. Although Pt(IV) complexes that conjugated with bioactive ligands show satisfactory anticancer effects, none has been approved for clinical use. Therefore, we hope that this review will contribute to further study and development of Pt(IV) complexes conjugated with bioactive and other ligands.

Novel platinum agents and mesenchymal stromal cells for thoracic malignancies: state of the art and future perspectives

INTRODUCTION

Non-small cell lung cancer and malignant pleural mesothelioma represent two of the most intriguing and scrutinized thoracic malignancies, presenting interesting perspectives of experimental development and clinical applications.

AREAS COVERED

In advanced non-small cell lung cancer, molecular targeted therapy is the standard first-line treatment for patients with identified driver mutations; on the other hand, chemotherapy is the standard treatment for patients without EGFR mutations or ALK rearrangement or those with unknown mutation status. Once considered an ineffective therapy in pulmonary neoplasms, immunotherapy has been now established as one of the most promising therapeutic options. Mesenchymal stromal cells are able to migrate specifically toward solid neoplasms and their metastatic localizations when injected intravenously. This peculiar cancer tropism has opened up an emerging field to use them as vectors to deliver antineoplastic drugs for targeted therapies.

EXPERT OPINION

Molecular targeted therapy and immunotherapy are the new alternatives to standard chemotherapy. Mesenchymal stromal cells are a new promising tool in oncology and-although not yet utilized in the clinical practice, we think they will represent another main tool for cancer therapy and will probably play a leading role in the field of nanovectors and molecular medicine.