Impact of intracellular chloride concentration on cisplatin accumulation in sensitive and resistant GLC4 cells

Effect of cisplatin on respiratory activity in neonatal rats

One side effect of cisplatin, a cytotoxic platinum anticancer drug, is peripheral neuropathy; however, its central nervous system effects remain unclear. We monitored respiratory nerve activity from the C4 ventral root in brainstem and spinal cord preparations from neonatal rats (P0-3) to investigate its central effects. Bath application of 10-100 μM cisplatin for 15-20 min dose-dependently decreased the respiratory rate and increased the amplitude of C4 inspiratory activity. These effects were not reversed after washout. In separate perfusion experiments, cisplatin application to the medulla decreased the respiratory rate, and application to the spinal cord increased the C4 burst amplitude without changing the burst rate. Application of other platinum drugs, carboplatin or oxaliplatin, induced no change of respiratory activity. A membrane potential analysis of respiratory-related neurons in the rostral medulla showed that firing frequencies of action potentials in the burst phase tended to decrease during cisplatin application. In contrast, in inspiratory spinal motor neurons, cisplatin application increased the peak firing frequency of action potentials during the inspiratory burst phase. The increased burst amplitude and decreased respiratory frequency were partially antagonized by riluzole and picrotoxin, respectively. Taken together, cisplatin inhibited respiratory rhythm via medullary inhibitory system activation and enhanced inspiratory motor nerve activity by changing the firing property of motor neurons.

Development of Facile and Versatile Platinum Drug Delivering Silicasome Nanocarriers for Efficient Pancreatic Cancer Chemo-Immunotherapy

In this study a mesoporous silica nanoparticle (MSNP) based platform is developed for high-dose loading of a range of activated platinum (Pt) chemo agents that can be attached to the porous interior through the use of electrostatic and coordination chemistry under weak-basic pH conditions. In addition to the design feature for improving drug delivery, the MSNP can also be encapsulated in a coated lipid bilayer (silicasome), to improve the colloidal stability after intravenous (IV) injection. Improved pharmacokinetics and intratumor delivery of encapsulated activated oxaliplatin (1,2-diamminocyclohexane platinum(II) (DACHPt)) over free drug in an orthotopic Kras-derived pancreatic cancer (PDAC) model is demonstrated. Not only does IV injection of the DACHPt silicasome provide more efficacious cytotoxic tumor cell killing, but can also demonstrate that chemotherapy-induced cell death is accompanied by the features of immunogenic cell death (ICD) as well as a dramatic reduction in bone marrow toxicity. The added ICD features are reflected by calreticulin and high-mobility group box 1 expression, along with increased CD8+ /FoxP3+ T-cell ratios and evidence of perforin and granzyme B release at the tumor site. Subsequent performance of a survival experiment, demonstrates that the DACHPt silicasome generates a significant improvement in survival outcome, which can be extended by delayed administration of the anti-PD-1 antibody.

Cellular pharmacology of evofosfamide (TH-302): A critical re-evaluation of its bystander effects

Evofosfamide (TH-302) is a clinical-stage hypoxia-activated prodrug with proven efficacy against hypoxic cells in preclinical tumour models. TH-302 is designed to release the DNA crosslinking agent bromo-isophosphoramide mustard (Br-IPM) when reduced in hypoxic tissue. Br-IPM is considered to diffuse locally from hypoxic regions, eliciting additional tumour cell killing, but the latter 'bystander effect' has not been demonstrated directly. Previous studies with multicellular co-cultures that included cells expressing the E. coli nitroreductase NfsA as a model TH-302 reductase have provided clear evidence of a bystander effect (which we confirm in the present study). However, NfsA is an oxygen-insensitive two-electron reductase that is not expected to generate the nitro radical intermediate that has been demonstrated to fragment to release Br-IPM. Here, we use mass spectrometry methods to characterise TH-302 metabolites generated by one-electron reduction (steady-state radiolysis by ionising radiation and cellular metabolism under hypoxia, including HCT116 cells that overexpress P450 oxidoreductase, POR) or by NfsA expressed in HCT116 cells under oxic conditions, and investigate the stability and cytotoxicity of these products. Br-IPM is shown to have very low cytotoxic potency when added to extracellular culture medium and to be rapidly converted to other hydrophilic products including dichloro-isophosphoramide mustard (IPM). Only traces of Br-IPM or IPM were detected in the extracellular medium when generated by cellular metabolism of TH-302. We identify, in NfsA-expressing cells, the hydroxylamine metabolite of TH-302, and downstream products resulting from rearrangement or hydration of the imidazole ring, and demonstrate that formation of these candidate bystander effect mediators is suppressed by hypoxia. This characterisation of the cellular pharmacology of TH-302 implies that bystander effects from hypoxic activation of TH-302 are unlikely to contribute to its anticancer activity.

Intracellular uptake of an antitumor-active azole-bridged dinuclear platinum(II) complex in cisplatin-resistant tumor cells

A cationic azolato-bridged dinuclear platinum(II) complex, [{cis-Pt(NH₃)₂}₂(μ-OH)(μ-methyl-pyrazolate)]²⁺ (4M-PzPt), was developed to overcome resistance to cisplatin (CDDP). This study aimed to assess the cytotoxicity of 4M-PzPt against a CDDP-resistant cell line, H4-II-E/CDDP, and compare the intracellular accumulation of CDDP and 4M-PzPt. H4-II-E and H4-II-E/CDDP displayed similar sensitivity to 4M-PzPt; however, the sensitivity of H4-II-E/CDDP to CDDP was approximately 19-fold lower than that of H4-II-E. The difference in the sensitivity to both platinum complexes corresponded with the difference in the amount of intracellular platinum accumulation after exposure to CDDP or 4M-PzPt in both cell lines. In H4-II-E, HepG2, and HuH-7 cells, the intracellular uptake of CDDP and 4M-PzPt occurred via active transport and passive transport. Results of co-exposure with the transport inhibitors ouabain, tetraethylammonium, and cimetidine indicated that the intracellular uptake of CDDP was dependent on Na⁺/K⁺-ATPase and that of 4M-PzPt was dependent on organic cation transporters (OCTs), probably OCT1. This study suggested that 4M-PzPt could inhibit the growth of a CDDP-resistant tumor via an intracellular uptake mechanism different from that of CDDP.

Recent achievements in colorectal cancer diagnostic and therapy by the use of nanoparticles

Colorectal cancer is a major public health issue, being the third most common cancer in men and the second in women. It is one of the leading causes of cancer deaths. Nanomedicine is an emerging field of interest, many of its aspects being linked to cancer research. Chemotherapy has a well-established role in colorectal cancer management, unfortunately being limited by inability to have a selective distribution, by multidrug resistance and adverse effects. Researches carried out in recent years about nanotechnologies aimed, among others, to resolve the issues mentioned above. Targeted and localized delivery of the chemotherapeutic drugs, using nanoparticles, with selective destruction of cancerous cells would minimize the toxicity on healthy tissues. Also, the use of nanomaterials as contrast agent could improve sensitivity and specificity of diagnosis. The purpose of this review is to highlight the recent achievements of cancer research by use of nanomaterials, in the idea of finding the ideal composite, capable to simultaneous diagnostic and treat cancer.

Annexin A4 induces platinum resistance in a chloride-and calcium-dependent manner

Platinum resistance has long been a major issue in the treatment of various cancers. We previously reported that enhanced annexin A4 (ANXA4) expression, a Ca²⁺-regulated phospholipid-binding protein, induces chemoresistance to platinum-based drugs. In this study, we investigated the role of annexin repeats, a conserved structure of all the annexin family, responsible for platinum-resistance as well as the effect of knockdown of ANXA4. ANXA4 knockdown increased sensitivity to platinum-based drugs both in vitro and in vivo. To identify the domain responsible for chemoresistance, ANXA4 deletion mutants were constructed by deleting annexin repeats one by one from the C terminus. Platinum resistance was induced both in vitro and in vivo in cells expressing either full-length ANXA4 or the deletion mutants, containing at least one intact annexin repeat. However, cells expressing the mutant without any calcium-binding sites in the annexin repeated sequence, which is essential for ANXA4 translocation from the cytosol to plasma membrane, failed to acquire platinum resistance. After cisplatin treatment, the intracellular chloride ion concentration, whose channel is partly regulated by ANXA4, significantly increased in the platinum-resistant cells. These findings indicate that the calcium-binding site in the annexin repeat induces chemoresistance to the platinum-based drug by elevating the intracellular chloride concentration.

Contribution of intracellular ATP to cisplatin resistance of tumor cells

Decreased cellular accumulation of cisplatin is a frequently observed mechanism of resistance to the drug. Beside passive diffusion, several cellular proteins using ATP hydrolysis as an energy source are assumed to be involved in cisplatin transport in and out of the cell. This investigation aimed at clarifying the contribution of intracellular ATP as an indicator of energy-dependent transport to cisplatin resistance using the A2780 human ovarian adenocarcinoma cell line and its cisplatin-resistant variant A2780cis. Depletion of intracellular ATP with oligomycin significantly decreased cellular platinum accumulation (measured by flameless atomic absorption spectrometry) in sensitive but not in resistant cells, and did not affect cisplatin efflux in both cell lines. Inhibition of Na(+),K(+)-ATPase with ouabain reduced platinum accumulation in A2780 cells but to a lesser extent compared with oligomycin. Western blot analysis revealed lower expression of Na(+),K(+)-ATPase α(1) subunit in resistant cells compared with sensitive counterparts. The basal intracellular ATP level (determined using a bioluminescence-based assay) was significantly higher in A2780cis cells than in A2780 cells. Our results highlight the importance of ATP-dependent transport, among other processes mediated by Na(+),K(+)-ATPase, for cisplatin influx in sensitive cells. Cellular platinum accumulation in resistant cells is reduced and less dependent on energy sources, which may partly result from Na(+),K(+)-ATPase downregulation. Our data suggest the involvement of other ATP-dependent processes beside those regulated by Na(+),K(+)-ATPase. Higher basal ATP level in cisplatin-resistant cells, which appears to be a consequence of enhanced mitochondrial ATP production, may represent a survival mechanism established during development of resistance.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Gold nanoparticles for the improved anticancer drug delivery of the active component of oxaliplatin

The platinum-based anticancer drugs cisplatin, carboplatin, and oxaliplatin are an important component of chemotherapy but are limited by severe dose-limiting side effects and the ability of tumors to develop resistance rapidly. These drugs can be improved through the use of drug-delivery vehicles that are able to target cancers passively or actively. In this study, we have tethered the active component of the anticancer drug oxaliplatin to a gold nanoparticle for improved drug delivery. Naked gold nanoparticles were functionalized with a thiolated poly(ethylene glycol) (PEG) monolayer capped with a carboxylate group. [Pt(1R,2R-diaminocyclohexane)(H₂O)₂]2NO₃ was added to the PEG surface to yield a supramolecular complex with 280 (±20) drug molecules per nanoparticle. The platinum-tethered nanoparticles were examined for cytotoxicity, drug uptake, and localization in the A549 lung epithelial cancer cell line and the colon cancer cell lines HCT116, HCT15, HT29, and RKO. The platinum-tethered nanoparticles demonstrated as good as, or significantly better, cytotoxicity than oxaliplatin alone in all of the cell lines and an unusual ability to penetrate the nucleus in the lung cancer cells.