A new platinum-based prodrug candidate: Its anticancer effects in B50 neuroblastoma rat cells

DNA Damage Repair in Glioblastoma: A Novel Approach to Combat Drug Resistance

Due to the lack of effective therapeutic approach, glioblastoma (GBM) remains one of the most malignant brain tumour. By in vitro investigations on primary GBM stem cells, we highlighted one of the underlying mechanisms of drug resistance to alkylating agents, the DNA damage responses. Here, flow cytometric analysis and viability and repopulation assays were used to assess the long-term cytotoxic effect induced by the administration of a fourth-generation platinum prodrug, the (OC-6-44)-acetatodiamminedichlorido(2-(2-propynyl)octanoato) platinum(IV) named Pt(IV)Ac-POA, in comparison to the most widely used Cisplatin. The immunofluorescence studies revealed changing pathways involved in the DNA damage response mechanisms in response to the two chemotherapies, suggesting in particular the role of Poly (ADP-Ribose) polymerases in the onset of resistance to Cisplatin-induced cytotoxicity. Thus, this research provides a proof of concept for how the use of a prodrug which allows the co-administration of Cisplatin and an Histone DeACetylase inhibitors, could suppress DNA repair mechanisms, suggesting a novel effective approach in GBM treatment.

Unraveling Novel Strategies in Mesothelioma Treatments Using a Newly Synthetized Platinum(IV) Compound

Malignant mesothelioma is a rare tumor associated with asbestos exposure. Mesothelioma carcinogenesis is related to enhanced reactive oxygen species (ROS) production and iron overload. Despite the recent advances in biomedical sciences, to date the only available treatments include surgery in a small fraction of patients and platinum-based chemotherapy in combination with pemetrexed. In this view, the purpose of this study was to evaluate the therapeutic potential of the newly synthetized platinum prodrug Pt(IV)Ac-POA compared to cisplatin (CDDP) on human biphasic mesothelioma cell line MSTO-211H using different complementary techniques, such as flow-cytometry, transmission electron microscopy (TEM), and immunocytochemistry. Healthy mesothelial cell lines Met-5A were also employed to assess the cytotoxicity of the above-mentioned compounds. Our in vitro results showed that Pt(IV)Ac-POA significantly interfere with iron metabolisms and more importantly is able to trigger cell death, through different pathways, including ferroptosis, necroptosis, and apoptosis, in neoplastic cells. On the other hand, CDDP triggers mainly apoptotic and necrotic cell death. In conclusion, Pt(IV)Ac-POA may represent a new promising pharmacological agent in the treatment of malignant mesothelioma.

A Phyto-mycotherapeutic Supplement, Namely Ganostile, as Effective Adjuvant in Brain Cancer Management: An In Vitro Study Using U251 Human Glioblastoma Cell Line

The current standard oncotherapy for glioblastoma is limited by several adverse side effects, leading to a short-term patient survival rate paralleled by a worsening quality of life (QoL). Recently, Complementary and Integrative Medicine's (CIM) innovative approaches have shown positive impacts in terms of better response to treatment, side effect reduction, and QoL improvement. In particular, promising potential in cancer therapy has been found in compounds coming from phyto- and mycotherapy. The objective of this study was to demonstrate the beneficial effects of a new phyto-mycotherapy supplement, named Ganostile, in the human glioblastoma cell line U251, in combination with chemotherapeutic agents, i.e., Cisplatin and a new platinum-based prodrug. Choosing a supplement dosage that mimicked oral supplementation in humans (about 1 g/day), through in vitro assays, microscopy, and cytometric analysis, it has emerged that the cells, after 48hr continuous exposure to Ganostile in combination with the chemical compounds, showed a higher mortality and a lower proliferation rate than the samples subjected to the different treatments administered individually. In conclusion, our data support the use of Ganostile in integrative oncology protocols as a promising adjuvant able to amplify conventional and new drug effects and also reducing resistance mechanisms often observed in brain tumors.

Reinforcing the immunogenic cell death to enhance cancer immunotherapy efficacy

Immunogenic cell death (ICD) has been a revolutionary modality in cancer treatment since it kills primary tumors and prevents recurrent malignancy simultaneously. ICD represents a particular form of cancer cell death accompanied by production of damage-associated molecular patterns (DAMPs) that can be recognized by pattern recognition receptors (PRRs), which enhances infiltration of effector T cells and potentiates antitumor immune responses. Various treatment methods can elicit ICD involving chemo- and radio-therapy, phototherapy and nanotechnology to efficiently convert dead cancer cells into vaccines and trigger the antigen-specific immune responses. Nevertheless, the efficacy of ICD-induced therapies is restrained due to low accumulation in the tumor sites and damage of normal tissues. Thus, researchers have been devoted to overcoming these problems with novel materials and strategies. In this review, current knowledge on different ICD modalities, various ICD inducers, development and application of novel ICD-inducing strategies are summarized. Moreover, the prospects and challenges are briefly outlined to provide reference for future design of novel immunotherapy based on ICD effect.

Platinum(IV) combo prodrugs containing cyclohexane-1R,2R-diamine, valproic acid, and perillic acid as a multiaction chemotherapeutic platform for colon cancer

The complex [PtCl2(cyclohexane-1R,2R-diamine)] has been combined in a Pt(IV) molecule with two different bioactive molecules (i.e., the histone deacetylase inhibitor 2-propylpentanoic acid or valproic acid, VPA, and the potential antimetastatic molecule 4-isopropenylcyclohexene-1-carboxylic acid or perillic acid, PA) in order to obtain a set of multiaction or multitarget antiproliferative agents. In addition to traditional thermal synthetic procedures, microwave-assisted heating was used to speed up their preparation. All Pt(IV) complexes showed antiproliferative activity on four human colon cancer cell lines (namely HCT116, HCT8, RKO and HT29) in the nanomolar range, considerably better than those of [PtCl2(cyclohexane-1R,2R-diamine)], VPA, PA, and the reference drug oxaliplatin. The synthesized complexes showed pro-apoptotic and pro-necrotic effects and the ability to induce cell cycle alterations. Moreover, the downregulation of histone deacetylase activity, leading to an increase in histone H3 and H4 levels, and the antimigratory activity, indicated by the reduction of the levels of matrix metalloproteinases MMP2 and MMP9, demonstrated the multiaction nature of the complexes, which showed biological properties similar to or better than those of VPA and PA, but at lower concentrations, probably due to the lipophilicity of the combo molecule that increases the intracellular concentration of the single components (i.e., [PtCl2(cyclohexane-1R,2R-diamine)], VPA and PA).

Study on the activation of cell death mechanisms: in search of new therapeutic targets in glioblastoma multiforme

Malignant primary brain tumors remain among the most difficult cancers to treat, in particular, Glioblastoma Multiforme (GBM) is the deadliest brain tumor. The standard therapies currently used are not efficient enough in improving patients' survival and quality of life. Cisplatin (CDDP), a platinum-based drug, has shown efficacy against different solid neoplasms, but it is also associated to different forms of off-target toxicity. To overcome the limitation in the use of CDDP in the treatment of GBM patients, fourth generation platinum compounds are been synthesized, one of them is the Pt(IV)Ac-POA, a prodrug with a medium-chain fatty acid as axial ligand, which acts as a histone 3 deacetylase inhibitor. Moreover, recently, the antioxidant effects of medicinal mushrooms have been shown to induce a lowering of the toxicity of chemotherapy drugs, inducing greater therapeutic efficiency, thus the combined therapy of chemotherapy and micotherapy could be helpful in the treatment of GBM reducing the adverse effects of the former thanks to phytotherapy's antioxidant, anti-inflammatory, immunomodulatory and antitumoral activities. Here, through immunoblotting, ultrastructural and immunofluorescence analysis, we evaluated the contribution in the activation of different cell death pathway of Micotherapy U-Care, a medicinal blend supplement, used together with platinum-based compounds on human glioblastoma U251 cells.

The power of a novel combined anticancer therapy: challenge and opportunity of micotherapy in the treatment of Glioblastoma Multiforme

Glioblastoma (GBM) is the most common and mortal primary brain tumor in human. After standard therapies, that include surgical resection followed by radiotherapy and chemotherapy, it is difficult to completely remove the tumor and the development of relapses and resistance is almost inevitable. The chemotherapy now available also show important side effects, to overcame those limitation, new platinum-based drugs are being synthetized, Pt(IV)Ac-POA, (OC-6-44)-acetate-diamine-chloride(2-(2-propynyl)octanoato)platinum(IV), a prodrug having an Histone-3-DeAcetylase-Inhibitor as axial ligands, is one of them. Moreover, new compounds of plant origin are increasingly seen as potential sources of benefits in oncological treatments. The aim of the study is to investigate the possible contribution of micotherapy in the fight against GBM, its role in the metabolism of reactive oxygen species (ROS) and its synergic effect with a new platinum-based compound, Pt(IV)Ac-POA, on human glioblastoma U251 cells. Through cytofluorimetric and immunofluorescence analysis, the ability of the micotherapy in study to regulate the cell cycle was assessed, and its importance in controlling the cellular redox state was also revealed, opening to the possibility of a new therapy in which micotherapy can support the activity of new chemotherapy while reducing its side effects controlling inflammatory conditions in the microenvironment. Additionally, the combined therapy appeared able to induce regulated form of necrosis, such as ferroptosis, and to hinder the establishment of resistance mechanisms.

Application of the anthraquinone drug rhein as an axial ligand in bifunctional Pt(IV) complexes to obtain antiproliferative agents against human glioblastoma cells

Octahedral Pt(IV) prodrugs are an effective way to combine cisplatin-like moieties and a second drug to obtain selective and stimuli responsive bifunctional antiproliferative compounds. Recently, two bifunctional Pt(IV) complexes have shown interesting in vitro and in vivo effects in glioblastoma, the most aggressive primary brain tumor. An interesting observation indicates that 4,5-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid (rhein) can inhibit in vivo glioma tumor progression. Furthermore, a prodrug in which cisplatin was combined with two molecules of rhein showed a potency higher than that of cisplatin toward cisplatin-resistant lung carcinoma cells. However, the high lipophilicity of this type of complex affects their solubility and bioavailability. To overcome these limits, in the present work, three Pt(IV) derivatives were obtained by differently linking one molecule of rhein and one acetato ligand at the axial position to a cisplatin core. The complexes proved to be similar to or more potent than the parent cisplatin and rhein, and the reference drug temozolomide on two human glioblastoma cell lines (U87-MG and T98G). They retained their activity under hypoxia and caused a significant reduction in the motility of both cell lines, which can be related to their ability to inhibit MMP2 and MMP9 matrix metalloproteinases. Finally, physicochemical and computational studies indicated that these Pt(IV) derivatives are more prone than rhein to cross the blood-brain barrier.

Pt(IV) antitumor prodrugs: dogmas, paradigms, and realities

Platinum(II)-based drugs are widely used for the treatment of solid tumors, especially in combination protocols. Severe side effects and occurrence of resistance are the major limitations to their clinical use. To overcome these drawbacks, a plethora of Pt(IV) derivatives, acting as anticancer prodrugs, have been designed, synthesized and preclinically (often only in vitro) tested. Here, we summarize the recent progress in the development and understanding of the chemical properties and biochemical features of these Pt(IV) prodrugs, especially those containing bioactive molecules as axial ligands, acting as multi-functional agents. Even though no such prodrugs have been yet approved for clinical use, many show encouraging pharmacological profiles. Thus, a better understanding of their features is a promising approach towards improving the available Pt-based anticancer agents.

Pt(iv) complexes based on cyclohexanediamines and the histone deacetylase inhibitor 2-(2-propynyl)octanoic acid: synthesis, characterization, cell penetration properties and antitumor activity

The Pt(iv) complexes based on (SP-4-2)-dichlorido(cyclohexane-1,4-diamine)platinum(ii) (kiteplatin) and the histone deacetylase inhibitor 2-(2-propynyl)octanoic acid (POA) were investigated. Since POA contains a chiral carbon, all the possible Pt(iv) isomers were prepared and characterized, and their antiproliferative activity on six cancer cell lines was compared with that of the corresponding Pt(iv) complexes containing the cyclohexane-1R,2R-diamine equatorial ligand. To justify the very good antiproliferative activity (nanomolar IC₅₀), the polarity, lipophilicity, permeability, and cell accumulation of the complexes were studied. Overall, the two series of Pt(iv) complexes showed similar cell penetration properties, being significantly better than that of the Pt(ii) reference compounds. Finally, a representative compound of the whole set of complexes (i.e., that based on cyclohexane-1R,2R-diamine and racemic POA) was tested in vivo on mice bearing Lewis lung carcinoma, showing good tumor growth inhibition with negligible body weight loss.

A New Platinum-Based Prodrug Candidate for Chemotherapy and Its Synergistic Effect With Hadrontherapy: Novel Strategy to Treat Glioblastoma

Glioblastoma (GBM) is the most common tumor of the central nervous system. Current therapies, often associated with severe side effects, are inefficacious to contrast the GBM relapsing forms. In trying to overcome these drawbacks, (OC-6-44)-acetatodiamminedichlorido(2-(2-propynyl)octanoato)platinum(IV), also called Pt(IV)Ac-POA, has been recently synthesized. This new prodrug bearing as axial ligand (2-propynyl)octanoic acid (POA), a histone deacetylase inhibitor, has a higher activity due to (i) its high cellular accumulation by virtue of its high lipophilicity and (ii) the inhibition of histone deacetylase, which leads to the increased exposure of nuclear DNA, permitting higher platination and promoting cancer cell death. In the present study, we investigated the effects induced by Pt(IV)Ac-POA and its potential antitumor activity in human U251 glioblastoma cell line using a battery of complementary techniques, i.e., flow cytometry, immunocytochemistry, TEM, and Western blotting analyses. In addition, the synergistic effect of Pt(IV)Ac-POA associated with the innovative oncological hadrontherapy with carbon ions was investigated, with the aim to identify the most efficient anticancer treatment combination. Our in vitro data demonstrated that Pt(IV)Ac-POA is able to induce cell death, through different pathways, at concentrations lower than those tested for other platinum analogs. In particular, an enduring Pt(IV)Ac-POA antitumor effect, persisting in long-term treatment, was demonstrated. Interestingly, this effect was further amplified by the combined exposure to carbon ion radiation. In conclusion, Pt(IV)Ac-POA represents a promising prodrug to be incorporated into the treatment regimen for GBM. Moreover, the synergistic efficacy of the combined protocol using chemotherapeutic Pt(IV)Ac-POA followed by carbon ion radiation may represent a promising approach, which may overcome some typical limitations of conventional therapeutic protocols for GBM treatment.

Bioactivity Screening of Mulberry Leaf Extracts and two Related Flavonoids in Combination with Cisplatin on Human Gastric Adenocarcinoma Cells

The successful therapy strategy of gastric cancer is defined as devastating the cancerous cells without exposing systematic toxicity and undesirable side effects. One strategy to overcome cancer treatment related difficulties could be combination therapy with natural products with anticancer drugs to introduce effective antitumor effects in addition to reduce undesirable side effects. In this regard, different extracts of mulberry leaf, isoquercetin and rutin as the extracted flavonoids from Morus alba, mulberry, in single dose as well as in combination with cisplatin against gastric cancer cell line were applied. This innovative treatment led to cytotoxic effect on gastric cancer cells in a synergistic manner. The findings anticipated that these herbal products have exceptional potential for future gastric cancer investigations and therapy.

Squaring the Circle: A New Study of Inward and Outward-Rectifying Potassium Currents in U251 GBM Cells

In the present study, the functional role of the inwardly rectifying K+ channel, Kir4.1, and large-conductance Ca2+-activated K+ (BK) channel during cell migration in U251 cell line was investigated. We focused on polarised cells which are positive for the active-Cdc42 migration marker. The perforated patch technique was used to avoid intracellular dialysis and to maintain physiological changes in intracellular calcium. Wound healing was employed to assay migration after 24 h. Polarised cells recorded displayed different hallmarks of undifferentiated glial cells: depolarised resting membrane potential and high membrane resistance. Cells recorded outside wounded area did not display either constitutive inward or outward rectification. After migration, U251 cells were characterised by a constitutively smaller Kir4.1 and larger BK currents with a linearly related amplitude. Menthol modulation increased both currents in a linearly dependent manner, indicating a common mechanism triggered by activation of transient receptor potential melastatin 8 (TRPM8), a Ca2+-permeable non-selective cation channel. We hypothesised that both migration and menthol modulation would share an increase of intracellular calcium triggering the increase in Kir4.1 and BK channels. Immunocytochemistry demonstrated the cytoplasmic expression of both Kir4.1 and BK channels and a mislocation in the nucleus under basal conditions. Before and after migration, polarised cells increased the expression of Kir4.1 and BK channels both in the cytoplasm and nucleus. TEM ultrastructural analysis displayed a different nuclear distribution of Kir4.1 and BK channels. In the present study, the physiological role of Kir4.1 and BK currents at membrane potential, their involvement in migration, and the functional role of nuclear channels were discussed.

New Platinum-Based Prodrug Pt(IV)Ac-POA: Antitumour Effects in Rat C6 Glioblastoma Cells

Gliomas are the most frequent primary tumours of the nervous system, characterised by high degree of malignancy, widespread invasion and high-rate proliferation. Cisplatin and analogue are currently employed in clinical trials as active chemotherapeutic agents for the systemic treatment of this type of malignancy. Despite therapy benefits, clinical use of these agents is hampered by severe side effects including neurotoxicity. Therefore, the aim of the present study was to analyse the effect of a new compound of platinum(IV) conjugate, named Pt(IV)Ac-POA, which can generate a synergistic antineoplastic action when released along with cisplatin, after a specific reduction reaction within tumour cells. To assess the effects of the novel compound on rat C6 glioma cells, cell cycle and cell death activation analyses were carried out using flow cytometry. Morphological changes and activation of different cell death pathways were evaluated by both transmission electron microscopy and immunofluorescence microscopy. Protein expression was investigated by western blotting analysis. The novel compound Pt(IV)Ac-POA, bearing as axial ligand (2-propynyl)octanoic acid (POA), which is a histone deacetylase inhibitor (HDACi), acts as a prodrug in tumour cells, inducing cell death through different pathways at a concentration lower than those tested for other platinum analogues. The current results showed that Pt(IV)Ac-POA could represent a promising improvement of Pt-based chemotherapy against gliomas, either inducing a chemosensitisation and reducing chemoresistance.

Pt(IV) Bifunctional Prodrug Containing 2-(2-Propynyl)octanoato Axial Ligand: Induction of Immunogenic Cell Death on Colon Cancer

The synthesis, characterization, and in vitro activity of a cyclohexane-1 R,2 R-diamine-based Pt(IV) derivative containing the histone deacetylase inhibitor rac-2-(2-propynyl)octanoato, namely, ( OC-6-44)-acetatodichlorido(cyclohexane-1 R,2 R-diamine)( rac-2-(2-propynyl)octanoato)platinum(IV), are reported together with those of its isomers containing enantiomerically enriched axial ligands. These Pt(IV) complexes showed comparable activity, of 2 orders of magnitude higher than reference drug oxaliplatin on three human (HCT 116, SW480, and HT-29) and one mouse (CT26) colon cancer cell lines. In vivo experiments were carried out on immunocompetent BALB/c mice bearing the same syngeneic tumor. The complex ( OC-6-44)-acetatodichlorido(cyclohexane-1 R,2 R-diamine)( rac-2-(2-propynyl)octanoato)platinum(IV) showed higher tumor mass Pt accumulation than oxaliplatin, due to its higher lipophilicity, with negligible nephro- and hepatotoxicities when administered intravenously. A remarkable tumor mass invasion by cytotoxic CD8+ T lymphocytes, following the Pt(IV) treatment, indicated a strong induction of immunogenic cell death.