Recent updates in the clinical use of platinum compounds for the treatment of lung, breast, and genitourinary tumors and myeloma

Effect of a Single Dose of Oxaliplatin on the Induction of Peripheral Neuropathy in a Rat Model: An in vivo Electrophysiological Study

The anticancer drug oxaliplatin is associated with peripheral neuropathy as a side effect accompanied by mechanical and cold allodynia. Although the superficial layer of the spinal cord dorsal horn is known to receive information primarily from peripheral pain nerves, to our knowledge, no in vivo electrophysiological analyses have been conducted to determine whether oxaliplatin administration increases the excitability of superficial layer neurons. Therefore, in vivo extracellular recordings were performed to measure action potentials in the deep and superficial layers of the spinal cord dorsal horn in rats treated with a single dose (6 mg/kg) of oxaliplatin. Action potentials were produced by mechanical stimulation with von Frey filaments to the hindlimb receptive fields. The results revealed that the firing frequency of action potentials increased relative to the intensity of mechanical stimulation, and that both deep and superficial layer neurons in the spinal cord dorsal horn increased significantly in oxaliplatin-treated compared with vehicle-treated rats, especially in the superficial layer. Several superficial layer neurons showed spontaneous firing that was not seen in vehicle-treated rats. In addition, a clear increase was seen in the firing frequency of neurons in the superficial layer of oxaliplatin-treated rats in response to a cold stimulus (here, the addition of acetone to the hindlimb receptive field). This study suggests that the superficial spinal cord dorsal horn strongly reflects the pain pathophysiology in peripheral neuropathy induced by oxaliplatin administration, and that the superficial layer neurons are useful for in vivo electrophysiological analysis using this pathological model.

Kidney-Targeted Redox Scavenger Therapy Prevents Cisplatin-Induced Acute Kidney Injury

Cisplatin-induced acute kidney injury (CI-AKI) is a significant co-morbidity of chemotherapeutic regimens. While this condition is associated with substantially lower survival and increased economic burden, there is no pharmacological agent to effectively treat CI-AKI. The disease is hallmarked by acute tubular necrosis of the proximal tubular epithelial cells primarily due to increased oxidative stress. We investigated a drug delivery strategy to improve the pharmacokinetics of an approved therapy that does not normally demonstrate appreciable efficacy in CI-AKI, as a preventive intervention. In prior work, we developed a kidney-selective mesoscale nanoparticle (MNP) that targets the renal proximal tubular epithelium. Here, we found that the nanoparticles target the kidneys in a mouse model of CI-AKI with significant damage. We evaluated MNPs loaded with the reactive oxygen species scavenger edaravone, currently used to treat stroke and ALS. We found a marked and significant therapeutic benefit with edaravone-loaded MNPs, including improved renal function, which we demonstrated was likely due to a decrease in tubular epithelial cell damage and death imparted by the specific delivery of edaravone. The results suggest that renal-selective edaravone delivery holds potential for the prevention of acute kidney injury among patients undergoing cisplatin-based chemotherapy.

Phytochemicals of Cinnamomi Cortex: Cinnamic Acid, but not Cinnamaldehyde, Attenuates Oxaliplatin-Induced Cold and Mechanical Hypersensitivity in Rats

A chemotherapy drug, oxaliplatin, induces cold and mechanical hypersensitivity, but effective treatments for this neuropathic pain without side effects are still lacking. We previously showed that Cinnamomi Cortex suppresses oxaliplatin-induced pain behaviors in rats. However, it remains unknown which phytochemical of Cinnamomi Cortex plays a key role in that analgesic action. Thus, here we investigated whether and how cinnamic acid or cinnamaldehyde, major components of Cinnamomi Cortex, alleviates cold and mechanical allodynia induced by a single oxaliplatin injection (6 mg/kg, i.p.) in rats. Using an acetone test and the von Frey test for measuring cold and mechanical allodynia, respectively, we found that administration of cinnamic acid, but not cinnamaldehyde, at doses of 10, 20 and 40 mg/kg (i.p.) significantly attenuates the allodynic behaviors in oxaliplatin-injected rats with the strongest effect being observed at 20 mg/kg. Our in vivo extracellular recordings also showed that cinnamic acid (20 mg/kg, i.p.) inhibits the increased activities of spinal wide dynamic range neurons in response to cutaneous mechanical and cold stimuli following the oxaliplatin injection. These results indicate that cinnamic acid has an effective analgesic action against oxaliplatin-induced neuropathic pain through inhibiting spinal pain transmission, suggesting its crucial role in mediating the effect of Cinnamomi Cortex.

Transfer Hydrogenation and Antiproliferative Activity of Tethered Half-Sandwich Organoruthenium Catalysts

We report the synthesis and characterization of four neutral organometallic tethered complexes, [Ru(η⁶-Ph(CH₂)₃-ethylenediamine-N-R)Cl], where R = methanesulfonyl (Ms, 1), toluenesulfonyl (Ts, 2), 4-trifluoromethylbenzenesulfonyl (Tf, 3), and 4-nitrobenzenesulfonyl (Nb, 4), including their X-ray crystal structures. These complexes exhibit moderate antiproliferative activity toward human ovarian, lung, hepatocellular, and breast cancer cell lines. Complex 2 in particular exhibits a low cross-resistance with cisplatin. The complexes show potent catalytic activity in the transfer hydrogenation of NAD⁺ to NADH with formate as hydride donor in aqueous solution (310 K, pH 7). Substituents on the chelated ligand decreased the turnover frequency in the order Nb > Tf > Ts > Ms. An enhancement of antiproliferative activity (up to 22%) was observed on coadministration with nontoxic concentrations of sodium formate (0.5–2 mM). Complex 2 binds to nucleobase guanine (9-EtG), but DNA appears not to be the target, as little binding to calf thymus DNA or bacterial plasmid DNA was observed. In addition, complex 2 reacts rapidly with glutathione (GSH), which might hamper transfer hydrogenation reactions in cells. Complex 2 induced a dose-dependent G₁ cell cycle arrest after 24 h exposure in A2780 human ovarian cancer cells while promoting an increase in reactive oxygen species (ROS), which is likely to contribute to its antiproliferative activity.

Duloxetine Protects against Oxaliplatin-Induced Neuropathic Pain and Spinal Neuron Hyperexcitability in Rodents

Oxaliplatin is a widely used chemotherapy agent, but induces serious peripheral neuropathy. Duloxetine is a dual reuptake inhibitor of serotonin and norepinephrine, and is shown to be effective against pain. However, whether and how duloxetine can attenuate oxaliplatin-induced allodynia in rodents is not clearly understood. A single injection of oxaliplatin (6 mg/kg, intraperitoneal; i.p.) induced a cold and mechanical allodynia, which was assessed by acetone and von Frey filament tests, respectively. When significant allodynic signs were observed, three different doses of duloxetine (10, 30, and 60 mg/kg, i.p.) were injected. Administration of 30 and 60 mg/kg of duloxetine significantly reduced the allodynia, whereas 10 mg/kg did not. By using an in vivo extracellular recording method, we further confirmed that 30 mg/kg of duloxetine could significantly inhibit the hyperexcitability of spinal wide dynamic range (WDR) cells. The anti-allodynic effect of duloxetine was completely blocked by an intrathecal injection of phentolamine (non-selective α-adrenergic receptor antagonist, 20 μg), or prazosin (α₁-adrenergic receptor antagonists, 10 μg); however, idazoxan (α₂-adrenergic receptor antagonist, 10 μg) did not block it. In conclusion, we suggest that duloxetine may have an effective protective action against oxaliplatin-induced neuropathic pain and spinal hyperexcitability, which is mediated by spinal α₁-adrenergic receptors.

Anticancer activity of hydroxy- and sulfonamide-azobenzene platinum(II) complexes in cisplatin-resistant ovarian cancer cells

The syntheses of three platinum(II) complexes bearing sulfonamide- ( (E)-2-(4-methylphenylsulfonamido)-2',6'-difluoroazobenzene, HL1) and hydroxy-azo-2,6-difluorobenzene ((E)-2-((2,6-difluorophenyl)diazenyl)phenol, HL2) bidentate ligands is described. These complexes, [Pt(L1)(DMSO)Cl] (1), [Pt(L2)(DMSO)Cl] (2), and [Pt(L2)₂] (3), were characterized by multinuclear NMR spectroscopy, mass spectrometry, and X-ray crystallography. Despite bearing azobenzene functional groups, none of the three complexes undergo photoisomerization. The anticancer activities of these complexes were evaluated in wild-type (A2780) and cisplatin-resistant (A2780CP70) ovarian cancer cells. All three complexes exhibited IC₅₀ values below 10μM and displayed similar activity in both A2780 and A2780CP70 cell lines, indicating that they are not cross-resistant with cisplatin. The DNA-binding properties of 1-3 were investigated by circular dichroism spectroscopy and by agarose gel electrophoresis. Both studies suggest that 1 and 2 form monofunctional DNA adducts.

IL-6 Inhibition Reduces STAT3 Activation and Enhances the Antitumor Effect of Carboplatin

Recent studies suggest that tumor-associated macrophage-produced IL-6 is an important mediator within the tumor microenvironment that promotes tumor growth. The activation of IL-6/STAT3 axis has been associated with chemoresistance and poor prognosis of a variety of cancers including colorectal carcinoma and thus serves as a potential immunotherapeutic target for cancer treatment. However, it is not fully understood whether anticytokine therapy could reverse chemosensitivity and enhance the suppressive effect of chemotherapy on tumor growth. In this study, we aimed to investigate the effect of IL-6 inhibition therapy on the antitumor effect of carboplatin. Enhanced expression of IL-6 and activation of STAT3 were observed in human colorectal carcinoma samples compared to normal colorectal tissue, with higher levels of IL-6/STAT3 in low grade carcinomas. Treatment of carboplatin (CBP) dose-dependently increased IL-6 production and STAT3 activation in human colorectal LoVo cells. Blockade of IL-6 with neutralizing antibody enhanced chemosensitivity of LoVo cells to carboplatin as evidenced by increased cell apoptosis. IL-6 blockade abolished carboplatin-induced STAT3 activation. IL-6 blockade and carboplatin synergistically reduced cyclin D1 expression and enhanced caspase-3 activity in LoVo cells. Our results suggest that inhibition of IL-6 may enhance chemosensitivity of colon cancers with overactive STAT3 to platinum agents.

THEORETICAL STUDY ON THE BINDING OF THE ANTICANCER DRUGS Cis/Trans-[PtCl52(NH3){HN = C(CH3)2}] AND Cis/Trans-[PtCl2{HN = C(CH3)2}2] TO PURINE BASES

The monofunctional (the first substitution reactions) and bifunctional (the second substitution reactions) binding of the title antitumor drugs to purine bases were studied computationally by using density functional theory and IEF-PCM solvation models. For the first substitutions with guanine and adenine, our calculations demonstrate that the trans monoaqua and diaqua reactant complexes (RCs) can generate trans- or cis-monoadducts via identical or very similar trigonal-bipyramidal transition-state structures, predicting that the cis-monoadducts generated by trans RCs can subsequently close by coordination to the adjacent purine bases to form 1,2-intrastrand Pt –DNA adducts and eventually distort DNA in the same way as cisplatin. Thus it is likely that the transplatin analogues have the same mechanism of anticancer activity of cisplatin. In general, the monoaqua and diaqua monofunctional substitutions prefer guanine over adenine. The calculated lowest activation free energy in aqueous solution is 15.2 kcal/mol in the monoaqua substitutions (substituted by guanine from trans- [Pt{HN = C(CH3)2}2Cl(H2O)]+ to trans/cis-monoadduct), and 11.4 kcal/mol in the diaqua substitutions (substituted by guanine from cis- [Pt{HN = C(CH3)2}2(H2O)2]2+ to cis-monoadduct). For the second substitutions, all the reactants are started from the diaqua product complexes of the first substitutions substituted by guanine. The data obtained for the complexation energy difference between guanine and adenine RCs suggest that a thermodynamic favors the formation of GG over GA adducts by ∼ 5 - 12 kcal/mol in aqueous solution. Moreover, there is a kinetic preference for the formation of GG over GA adduct for the cis-monoadduct to cis-diadduct paths, while for the trans-monoadduct to trans-diadduct paths there is no certain trend biased toward GG adduct. In addition, the second substitutions of the trans-monoadduct to trans-diadduct paths have lower activation barriers than the corresponding cis-monoadduct to cis-diadduct paths. The lowest activation energy in the bifunctional substitutions from cis-monoadduct to cis-diadduct is 20.5 kcal/mol in the Pt (acetonimine)2GG2+ head-to-head (HH) path, while it is 17.7 kcal/mol from trans-monoadduct to trans-diadduct in the Pt(NH3) (acetonimine)GA2+ head-to-tail (HT) path. For the first and second substitutions, hydrogen-bonds play an important role in stabilizing these species.

Carboplatin delays mammary cancer 4T1 growth in mice

Carboplatin is commonly used to treat a variety of tumors. We investigated the effects of carboplatin (100mg/kg) in the development and metastatic dissemination of the 4T1 mice mammary carcinoma. Carboplatin was able to reduce tumor volume and the number of lung metastases in 50% compared to the control animals. Mitotic and apoptotic indices were also decreased by the treatment. Assessment of the vascularization of the tumors revealed a significant decrease in blood vessel formation by carboplatin. A decrease in nuclear positivity of CDC47 and cyclin D1 was observed in the group treated with carboplatin when compared to the control group. Positivity for p53 was observed in the control group (2/28; 5%) and the treated group (5/71; 4%). Carboplatin has been demonstrated to be an efficient regulator of 4T1MMT growth and dissemination. The action of this chemotherapeutic agent seems to be related to the induction of apoptosis and inhibition of angiogenesis and cell proliferation.

Intralymphatic delivery of platinum-based chemotherapeutics is possible: an experimental study

PURPOSE

Systemic chemotherapy regimens with cisplatinum have been associated with several toxicities. Thus, a loco-regional therapy approach may greatly reduce the toxicity. For this purpose, we designed this experimental study to investigate whether local chemotherapeutic injection is superior to systemic cisplatinum injection for retroperitoneal lymph nodes.

METHODS

A total of 48 male Wistar rats were included to the study. Rats were divided into six groups. In the first three groups, systemic applications of cisplatinum, carboplatinum and oxaliplatin were performed, respectively. In the last three, local administration of cisplatinum, carboplatinum and oxaliplatin was performed, respectively. One hour after the chemotherapeutic agent applications, retroperitoneal lymph nodes were dissected and platinum concentrations were analyzed.

RESULTS

When compared with systemic route, achieving higher platinum concentrations in the local chemotherapeutic application groups was the most spectacular result of the study. Serum platinum concentrations were also lower in the local application groups than systemic ones. When we compared local and systemic applications between three chemotherapeutic agents, the most significant concentration difference was seen in carboplatinum group.

CONCLUSION

The results of this study demonstrate that intralymphatic delivery of cisplatinum, carboplatinum and oxaliplatin leads to higher drug concentrations in the retroperitoneal lymph nodes when compared with intravenous administration.

NMR J-coupling constants in cisplatin derivatives studied by molecular dynamics and relativistic DFT

Solvent effects on J((195)Pt-(15)N) one-bond nuclear spin-spin coupling constants (J(PtN)) of cisplatin [cis-diamminedichloroplatinum(II)] and three cisplatin derivatives are investigated using a combination of density functional theory (DFT) based ab initio molecular dynamics (aiMD) and all-electron relativistic DFT NMR calculations employing the two-component relativistic zeroth-order regular approximation (ZORA). Good agreement with experiment is obtained when explicit solvent molecules are considered and when the computations are performed with a hybrid functional. Spin-orbit coupling causes only small effects on J(PtN) . Key factors contributing to the magnitude of coupling constants are elucidated, with the most significant being the presence of solvent as well as the quality of the density functional and basis set combination. The solvent effects are of the same magnitude as J(PtN) calculated for gas-phase geometries. However, the trends of J(PtN) among the complexes are already present in the gas phase. Results obtained with a continuum solvent model agree quite well with the aiMD results, provided that the Pt solvent-accessible radius is carefully chosen. The aiMD results support the existence of a partial hydrogen-bond-like inverse-hydration-type interaction affording a weak (1)J(Pt⋅⋅⋅H(w)) coupling between the complexes and the coordinating water molecule.

Comparison of the combined action of oxaliplatin or cisplatin and radiation in cervical and lung cancer cells

BACKGROUND AND PURPOSE

To test the combined effects of oxaliplatin and radiation versus cisplatin and radiation using human cervical and lung cancer cell lines.

MATERIAL AND METHODS

CaSki cervical cancer cells, and A549 lung cancer cells were cultured under standard conditions. Cells were treated with escalating doses of gamma-irradiation (0-6 Gy), and with oxali- and cisplatin for 2 h or 24 h, or a combination of both. Cell survival was measured by a colony-forming assay. Survival curves were fitted to the data using the linear quadratic model. Sensitizer enhancement ratios (SER) were calculated at the 37% survival level, and isobologram analysis was applied to test for the drug-radiation interactions.

RESULTS

Oxaliplatin as well as cisplatin alone were cytotoxic in both cell lines. In CaSki cells, oxaliplatin and cisplatin significantly increased radiation toxicity. In A549 cells no increase of radiation toxicity was observed after treatment with cisplatin, however, isobologram analysis revealed supra-additive interaction between oxaliplatin and radiation in A549 cells.

CONCLUSION

Oxaliplatin had the same effectiveness on tumor cells as cisplatin and induced enhanced radiation toxicity in lung cancer cells, where cisplatin was not able to achieve radiosensitization.

Pharmacokinetics and tissue distribution of novel traditional Chinese medicine-platinum anticancer agents in rats

The pharmacokinetics and tissue distribution profiles of a novel series of traditional Chinese medicine-platinum (TCM-Pt) compounds [Pt(C(8)H(8)O(5))(NH(2)R)(2)]: 1 (where R=H), 3 (R=CH(3)) and 5 (R=C(6)H(10)), were studied in Sprague-Dawley rats following a single bolus intravenous (i.v.) injection. Platinum concentrations in total plasma, plasma ultrafiltrate, urine and tissues were measured by flameless atomic absorption spectroscopy. Pharmacokinetic studies showed that plasma concentrations of total and free platinum for the novel TCM-Pt compounds as well as cisplatin and carboplatin declined in a biexponential manner with a short distribution half-life (t(1/2alpha): 0.12-0.34h). Compared with cisplatin, the novel TCM-Pt compounds had a longer elimination half-life (t(1/2beta)), larger dose normalized area under the curve (AUC/D), larger volume of distribution at steady-state (V(ss)), slower clearance (CL) of free platinum and higher percentage of cumulative urinary excretion (CUE), which can be attributed to their lower chemical reactivities. In tissues, the highest Pt concentrations were found in the kidney, followed by the liver and the lowest in the heart; no Pt was detected in the brain. Twenty-four hours after drug administration, platinum concentrations in tissues were significantly lower for the novel TCM-Pt compounds. These findings suggest that the novel compounds might afford higher clinical efficacy and reduced systemic side effects, when compared with cisplatin.

On the potential of thioredoxin reductase inhibitors for cancer therapy

Thioredoxin reductase (TrxR)-as part of a major thiol regulating system-allows redox metabolism to adjust to cellular requirements. Therefore, changes at the redox level reflect as a pars pro toto changes concerning the entire cell. Three different TrxR isoenzymes, TrxR1 as cytosolic, TrxR2 as mitochondrial, and TrxR3 as testis-specific thiol regulator are known. All three enzymes contain a reactive and solvent accessible selenocysteine residue which is located on a flexible C-terminal arm of the protein. This selenocysteine is essentially involved in the catalytic cycle of TrxR and thus represents an attractive binding site for inhibitors. Many tumor cells have elevated TrxR levels and TrxR has been shown to play a major role in drug resistance. Inhibition of TrxR and its related redox reactions may thus contribute to a successful single, combinatory or adjuvant cancer therapy. A great number of effective natural and synthetic TrxR inhibitors are now available possessing antitumor potential ranging from induction of oxidative stress to cell cycle arrest and apoptosis. This article summarizes the present knowledge on the potential of TrxR inhibitors and TrxR as anticancer drug target.

Octahedral Pt(IV) complex K101 induces apoptosis via ERK1/2 activation and the p53 pathway in human colon cancer cells

Recently, the synthesized octahedral Pt(IV) compound trans,cis-Pt(acetato)2Cl2(1,4-butanediamine), K101, showed potent anti-tumor activity in vitro and in vivo. For the further investigation of K101-induced anti-cancer activity, we tested cytotoxicity against various cancer cell lines and performed the histoculture drug response assay (HDRA) against human colorectal tumor tissues in vitro. We investigated the signaling pathway of K101-induced apoptosis via expression of p53 and ERK1/2 in the human colon cell line HCT116. The cytotoxicity and the three-dimensional HDRA of K101 were evaluated using the MTT assay. To study the K101-induced apoptosis pathway, we performed FACS analysis and immunoblotting of p53, p21, Bax, Fas and ERK1/2 in HCT116 cells treated with or without K101. The cytotoxic IC50 values of K101 ranged from 1.15 to 2.38 micromol/l, compared to cisplatin ranging from 2.13 to 13.1 micromol/l. Among several cancer cell lines, K101 showed greater potency than cisplatin in colon cancer cell lines. In the HDRA, K101 showed 80.0-91.4% efficacy rates compared with 48.6% for cisplatin against colorectal cancer patient tissues. In the signaling pathway, the expression of p53 and phospho-ERK1/2 was increased in a time-dependent manner by treatment with K101 in the HCT116 cells. When K101 was treated with MEK inhibitor U0126, the cell death rate was increased. The octahedral Pt(IV) complex K101 could be an attractive candidate as a chemotherapeutic agent against colon cancer. ERK1/2 activation and the p53 pathway may play significant functions in mediating K101-induced apoptosis in human colon cancer cells.

Antiglioma activity of 2,2':6',2"-terpyridineplatinum(II) complexes in a rat model--effects on cellular redox metabolism

The mammalian thioredoxin system, comprising the selenoenzyme thioredoxin reductase (TrxR) and the 12-kDa protein thioredoxin (Trx), is implicated in thiol-mediated antioxidant defense and redox regulatory processes including transcriptional control, DNA synthesis, and apoptosis. Cell proliferation supported by the thioredoxin system can be suppressed by TrxR inhibition. In this study, we assessed the effects of the potent hTrxR inhibitors 4-mercaptopyridine (4'-chloro-2,2':6',2"-terpyridine)platinum nitrate (I(23)2N) and 2-mercaptopyridine (4'-chloro-2,2':6',2"-terpyridine)platinum nitrate (I(25)2N) on glioblastoma in a rat model. These compounds show no or little cross-resistance with cisplatin and are thus of great clinical interest. Triple intravenous application of 25-35 mg/kg of the compounds led to a significant decrease of tumor growth as determined by magnetic resonance imaging. Metabolic as well as redox parameters in the blood of the animals were not altered. However, TrxR activity was significantly decreased in the tumor tissue, and redox parameters-including glutathione concentrations, total antioxidant status, and the activities of different antioxidant enzymes-showed tissue-specific variations. As indicated by different apoptotic markers, the antitumor activity of I(23)2N is not mediated by the induction of programmed cell death but rather by hTrxR inhibition and DNA intercalation leading to cell cycle arrest.