Irinotecan-cisplatin interactions assessed in cell-based screening assays: cytotoxicity, drug accumulation and DNA adduct formation in an NSCLC cell line

c-Myc Protein Level Affected by Unsymmetrical Bisacridines Influences Apoptosis and Senescence Induced in HCT116 Colorectal and H460 Lung Cancer Cells

Unsymmetrical bisacridines (UAs) are highly active antitumor compounds. They contain in their structure the drugs previously synthesized in our Department: C-1311 and C-1748. UAs exhibit different properties than their monomer components. They do not intercalate to dsDNA but stabilize the G-quadruplex structures, particularly those of the MYC and KRAS genes. Since MYC and KRAS are often mutated and constitutively expressed in cancer cells, they can be used as therapeutic targets. Herein, we investigate whether UAs can affect the expression and protein level of c-Myc and K-Ras in HCT116 and H460 cancer cells, and if so, what are the consequences for the UAs-induced cellular response. UAs did not affect K-Ras, but they strongly influenced the expression and translation of the c-Myc protein, and in H460 cells, they caused its full inhibition. UAs treatment resulted in apoptosis, as confirmed by the morphological changes, the presence of sub-G1 population and active caspase-3, cleaved PARP, annexin-V/PI staining and a decrease in mitochondrial potential. Importantly, apoptosis was induced earlier and to a greater extent in H460 compared to HCT116 cells. Moreover, accelerated senescence occurred only in H460 cells. In conclusion, the strong inhibition of c-Myc by UAs in H460 cells may participate in the final cellular response (apoptosis, senescence).

The Influence of Antitumor Unsymmetrical Bisacridines on 3D Cancer Spheroids Growth and Viability

The culture of 3D spheroids is a promising tool in drug development and testing. Recently, we synthesized a new group of compounds, unsymmetrical bisacridines (UAs), which exhibit high cytotoxicity against various human cell lines and antitumor potency against several xenografts. Here, we describe the ability of four UAs—C-2028, C-2041, C-2045, and C-2053—to influence the growth of HCT116 and H460 spheres and the viability of HCT116 cells in 3D culture compared with that in 2D standard monolayer culture. Spheroids were generated using ultra-low-attachment plates. The morphology and diameters of the obtained spheroids and those treated with UAs were observed and measured under the microscope. The viability of cells exposed to UAs at different concentrations and for different incubation times in 2D and 3D cultures was assessed using 7-AAD staining. All UAs managed to significantly inhibit the growth of HCT116 and H460 spheroids. C-2045 and C-2053 caused the death of the largest population of HCT116 spheroid cells. Although C-2041 seemed to be the most effective in the 2D monolayer experiments, in 3D conditions, it turned out to be the weakest compound. The 3D spheroid culture seems to be a suitable method to examine the efficiency of new antitumor compounds, such as unsymmetrical bisacridines.

DFIQ, a Novel Quinoline Derivative, Shows Anticancer Potential by Inducing Apoptosis and Autophagy in NSCLC Cell and In Vivo Zebrafish Xenograft Models

Lung cancer is one of the deadliest cancers worldwide due to chemoresistance in patients with late-stage disease. Quinoline derivatives show biological activity against HIV, malaria, bacteriuria, and cancer. DFIQ is a novel synthetic quinoline derivative that induces cell death in both in vitro and in vivo zebrafish xenograft models. DFIQ induced cell death, including apoptosis, and the IC₅₀ values were 4.16 and 2.31 μM at 24 and 48 h, respectively. DFIQ was also found to induce apoptotic protein cleavage and DNA damage, reduce cell cycle-associated protein expression, and disrupt reactive oxygen species (ROS) reduction, thus resulting in the accumulation of superoxide radicals. Autophagy is also a necessary process associated with chemotherapy-induced cell death. Lysosome accumulation and lysosome-associated membrane protein-2 (LAMP2) depletion were observed after DFIQ treatment, and cell death induction was restored upon treatment with the autophagy inhibitor 3-methyladenine (3-MA). Nevertheless, ROS production was found to be involved in DFIQ-induced autophagy activation and LAMP2 depletion. Our data provide the first evidence for developing DFIQ for clinical usage and show the regulatory mechanism by which DFIQ affects ROS, autophagy, and apoptosis.

Oral Administration of Clinical Stage Drug Candidate SENS-401 Effectively Reduces Cisplatin-induced Hearing Loss in Rats

HYPOTHESIS

SENS-401, an oral clinical-stage drug, may reduce cisplatin-induced hearing loss and cochlear damage in an in vivo model.

BACKGROUND

Cisplatin is commonly associated with hearing loss, causing significant learning and behavioral difficulties in the pediatric cancer population, and for which there are currently no clinical solutions. SENS-401 has previously been shown to improve acoustic trauma-induced hearing loss in vivo.

METHODS

The effect of SENS-401 (R-azasetron besylate) on cisplatin IC50 values was evaluated in a panel of cisplatin-sensitive cell lines (NIH:OVCAR-3, SK-N-AS, NCI-H460, FaDu). Auditory brainstem response and distortion product otoacoustic emission tests were performed in a rat model of cisplatin-induced hearing-loss (8 mg/kg, day 1) at baseline, and after 14 days of SENS-401 (6.6, 13.2, 26.4 mg/kg/d). Cochlear outer hair cells were counted after immunolabeling for myosin-VIIa.

RESULTS

Cisplatin cytotoxicity was not impacted by the addition of SENS-401 (up to 10 μM) in any of the cell types evaluated. In vivo, all SENS-401 doses significantly improved auditory brainstem response threshold shift (up to 30 dB) and distortion product otoacoustic emission amplitude loss (up to 19 dB) over placebo. Body weight and survival were not significantly different between rats receiving placebo and those receiving 26.4 mg/kg SENS-401. Significantly more surviving outer hair cells were present after SENS-401 treatment compared with placebo (p < 0.001), with up to 11-fold more in the basal turn of the cochlea.

CONCLUSION

In vivo and in vitro data support the otoprotective potential and tolerability of SENS-401 without impacting chemotherapeutic potential. Oral SENS-401 is a promising candidate for treating cisplatin-induced ototoxicity.

Synergistic cytotoxicity of irinotecan and cisplatin in dual-drug targeted polymeric nanoparticles

AIM

Two unexplored aspects for irinotecan and cisplatin (I&C) combination chemotherapy are: actively targeting both drugs to a specific diseased cell type, and delivering both drugs on the same vehicle to ensure their synchronized entry into the cell at a well-defined ratio. In this work, the authors report the use of targeted polymeric nanoparticles (NPs) to coencapsulate and deliver I&C to cancer cells expressing the prostate-specific membrane antigen.

MATERIALS & METHODS

Targeted NPs were prepared in a single step by mixing four different precursors inside microfluidic devices.

RESULTS

I&C were encapsulated in 55-nm NPs and showed an eightfold increase in internalization by prostate-specific membrane antigen-expressing LNCaP cells compared with nontargeted NPs. NPs coencapsulating both drugs exhibited strong synergism in LNCaP cells with a combination index of 0.2.

CONCLUSION

The strategy of coencapsulating both I&C in a single NP targeted to a specific cell type could potentially be used to treat different types of cancer.

Selective and cell-active inhibitors of the USP1/ UAF1 deubiquitinase complex reverse cisplatin resistance in non-small cell lung cancer cells

Ubiquitin-specific proteases (USPs) have in recent years emerged as a promising therapeutic target class. We identified selective small-molecule inhibitors against a deubiquitinase complex, the human USP1/UAF1, through quantitative high throughput screening (qHTS) of a collection of bioactive molecules. The top inhibitors, pimozide and GW7647, inhibited USP1/UAF1 noncompetitively with a K(i) of 0.5 and 0.7 μM, respectively, and displayed selectivity against a number of deubiquitinases, deSUMOylase, and cysteine proteases. The USP1/UAF1 inhibitors act synergistically with cisplatin in inhibiting cisplatin-resistant non-small cell lung cancer (NSCLC) cell proliferation. USP1/UAF1 represents a promising target for drug intervention because of its involvement in translesion synthesis and Fanconi anemia pathway important for normal DNA damage response. Our results support USP1/UAF1 as a potential therapeutic target and provide an example of targeting the USP/WD40 repeat protein complex for inhibitor discovery.

Unusual Reactivity of a Potent Platinum-Acridine Hybrid Antitumor Agent

The formation of unusual seven-membered, sterically overloaded chelates [Pt(en)(L/L´)](NO(3))(2) (4a/4b) from the corresponding potent hybrid antitumor agents [PtCl(en)(LH/L´H)](NO(3))(2) (3a/3b) is described, where en is ethane-1,2-diamine and L(H) and L´(H) are (protonated) N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide and N-(2-(acridin-9-ylamino)ethyl)-N-methylacetimidamide, respectively. Compounds 3a and 3b inhibit H460 lung cancer cell proliferation with IC(50) values of 12 ± 2 nM and 2.8 ± 0.3 nM, respectively. The new derivative 3b proves to be not only the most cytotoxic platinum-acridine hybrid of this kind, but also one of the most potent platinum-based anticancer agents described to date. The chelates 4a and 4b do not undergo ligand substitution reactions with nucleobase nitrogen and cysteine sulfur and do not intercalate into DNA. Despite their inertness, the two chelates appear to maintain micromolar activity in H460 cells. The results are discussed in the context of potential DNA-mediated and DNA-independent cell kill mechanisms and the potential use of the chelates as prodrugs.

Enhanced antitumor activity of low-dose continuous administration schedules of topotecan in prostate cancer

PURPOSE

The objective of this study was to determine the antitumor effects of alternate dosing schedules of topotecan in prostate cancer.

RESULTS

A concentration-dependent increase in cytotoxicity was observed in PC-3 and LNCaP cells after topotecan treatment using conventional and metronomic protocols. A significant increase in potency (2.4-18 fold, after 72 hr) was observed following metronomic dosing compared to conventional dosing administration in both cell lines. Metronomic dosing also increased the percentage of PC-3 cells in the G2/M, compared to control, but did not alter LNCaP cell cycle distribution. Metronomic dosing increased p21 protein expression in LNCaP and PC-3 cells compared to conventional dosing. The observed in vitro activity was confirmed using an in vivo model of human prostate cancer. Metronomic dosing and continuous infusion decreased tumor volume significantly (p < 0.05) compared to control and conventional topotecan treatment, but had no effect on tumor vascular staining.

METHODS

The cytotoxicity of topotecan after conventional or metronomic dosing was determined by examining cellular morphology, mitochondrial enzymatic activity (MTT), total cellular protein (SRB), annexin V and propidium iodine (PI) staining, cell cycle and western blot analysis in human prostate cancer cell lines (PC-3 and LNCaP) and the effects metronomic or continuous infusion on tumor growth in an in vivo tumor xenograft model.

CONCLUSIONS

These data support the hypothesis that low-dose continuous administration of topotecan increases potency compared to conventional dosing in prostate cancer. These data also suggest the novel finding that the enhanced antitumor activity of topotecan following low-dose exposure correlates to alterations in cell cycle and increased p21 expression.

Drug ratio-dependent antitumor activity of irinotecan and cisplatin combinations in vitro and in vivo

Irinotecan and cisplatin are two established anticancer drugs, which together constitute an effective combination for treating small-cell lung cancer. We investigated whether the efficacy of this combination could be improved by controlling drug ratios following in vivo administration. Irinotecan and cisplatin combinations were evaluated systematically for drug ratio-dependent synergy in vitro using a panel of 20 tumor cell lines. In vitro screening informatics on drug ratio-dependent cytotoxicity identified a consistently antagonistic region between irinotecan/cisplatin molar ratios of 1:2 to 4:1, which was bordered by two synergistic regions. Liposomal co-formulations of these two agents were developed that exhibited plasma drug half-lives of approximately 6 hours and maintained a fixed drug ratio for more than 24 hours. Drug ratio-dependent antitumor activity was shown in vivo for these liposome formulations, and irinotecan/cisplatin ratios between 5:1 and 10:1 were identified as therapeutically optimal. The relationship between irinotecan/cisplatin ratio and in vivo efficacy was consistent with in vitro drug ratio dependency results. Superior antitumor activity was observed for the liposome-encapsulated 7:1 molar ratio of irinotecan/cisplatin (designated CPX-571) compared with the free-drug cocktail in all models tested. Further efficacy studies in a range of human tumor xenografts, including an irinotecan-resistant model, showed that both liposomal agents contributed to the overall efficacy in a manner consistent with in vivo synergy. These results show the ability of drug delivery technology to enhance the therapeutic activity of irinotecan/cisplatin combination treatment by maintaining synergistic ratios in vivo. CPX-571, a fixed-ratio formulation of irinotecan and cisplatin, is a promising candidate for clinical development.

Development of an experimental protocol for uptake studies of metal compounds in adherent tumor cells

Cellular uptake is being widely investigated in the context of diverse biological activities of metal compounds on the cellular level. However, the applied techniques differ considerably, and a validated methodology is not at hand. Therefore, we have varied numerous aspects of sample preparation of the human colon carcinoma cell line SW480 exposed in vitro to the tumor-inhibiting metal complexes cisplatin and indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(iii)] (KP1019) prior to analysis with ICP-MS, and the results were found to be tremendously influenced by adsorption to the culture dishes. Adsorption to culture plates increases linearly with the concentration of KP1019, depends on the protein content of the medium, the duration of contact to protein-containing medium prior to drug addition and the hydrophilicity/lipophilicity of the compound. For varying degrees of cell confluence, adsorption of Ru hardly differs from cell-free experiments. Desorption from the plates contributes to total Ru detected in dependence on the cell harvesting method. Desorption kinetics for lysis in HNO(3) and tetramethylammonium hydroxide (TMAH) are comparable, but TMAH is a more potent desorbant. Sample storage conditions prior to analysis influence significantly the recovery of analyte. Protocols using cell lysis in the culture plate without proper corrections run the risk of producing artefacts resulting from metal adsorption/desorption to an extent comparable with the actual cellular content. However, experimental protocols reported in the literature frequently do not contain information whether adsorption or blank correction were performed and should be regarded with caution, especially if lysis was performed directly in the culture dishes.