Increased toxicity of a trinuclear Pt-compound in a human squamous carcinoma cell line by polyamine depletion

What happened to BBR3464 and where to from here for multinuclear platinum-based anticancer drugs?

The development of the trinuclear platinum(II) complex BBR3464 (also known as triplatin) in the late 1990s was meant to be a revolution in the field of platinum chemotherapy. What made it remarkable was that it defied many of the known structure-activity rules for platinums; it is cationic, has a single labile trans leaving group on each terminal platinum, and it binds DNA in ways different to mononuclear platinum drugs, like cisplatin and oxaliplatin. The flexible, long-range adducts the drug forms with DNA means that it showed activity in cancers not typically sensitive to platinums, and more importantly, BBR3464 demonstrated an ability to overcome acquired resistance to platinum drugs. But while preclinical and phase I testing showed promise, its more severe side effects which greatly limited the deliverable dose when compared with standard platinums, combined with its lack of biostability, led to a lack of activity in phase II trials and its development was halted. But, from its ashes have risen 4th generation complexes which target the phosphate backbone of DNA. These, and the original BBR3464 drug, could potentially be further developed and gain regulatory approval through formulation with macrocycle-based drug delivery vehicles.

Use of Anticancer Platinum Compounds in Combination Therapies and Challenges in Drug Delivery

As one of the leading and most important metal-based drugs, platinum-based pharmaceuticals are widely used in the treatment of solid malignancies. Despite significant side effects and acquired drug resistance have limited their clinical applications, platinum has shown strong inhibitory effects for a wide assortment of tumors. Drug delivery systems using emerging technologies such as liposomes, dendrimers, polymers, nanotubes and other nanocompositions, all show promise for the safe delivery of platinum-based compounds. Due to the specificity of nano-formulations; unwanted side-effects and drug resistance can be largely averted. In addition, combinational therapy has been shown to be an effective way to improve the efficacy of platinum based anti-tumor drugs. This review first introduces drug delivery systems used for platinum and combinational therapeutic delivery. Then we highlight some of the recent advances in the field of drug delivery for combinational therapy; specifically progress in leveraging the cytotoxic nature of platinum-based drugs, the combinational effect of other drugs with platinum, while evaluating the drug targeting, side effect reducing and sitespecific nature of nanotechnology-based delivery platforms.

Synergism of ursolic acid and cisplatin promotes apoptosis and enhances growth inhibition of cervical cancer cells via suppressing NF-κB p65

Objective

This study was designed to investigate the effect of combination of ursolic acid (UA) with cisplatin (DDP) on cervical cancer cell proliferation and apoptosis.

Methods

The mRNA and protein expressions of nuclear factor-kappa B (NF-κB) p65 in cervical cancer cells were examined using RT-PCR and western blot. MTT and colony formation assays were performed to examine the DDP toxicity and the proliferation ability of cervical cancer cells. Cell morphology was observed by means of Hoechst33258 and transmission electron microscopy (TEM). The apoptosis rate and cell cycle were assessed through flow cytometry assay. Western blot was used to detect the expression of apoptosis-related molecules.

Results

The mRNA and protein expressions of NF-κB p65 in cervical cancer cells were significantly higher than that in cervical epithelial cells. The combined treatment of UA and DDP inhibited cervical cancer cell growth and promoted apoptosis more effectively than DDP treatment or UA treatment alone (P < 0.05). Compared with the DDP group and UA group, the expressions of Bcl-2 and NF-κB p65 in DDP +UA group were decreased, while the expressions of Bax, Caspase-3 and PARP cleavage were observably increased. The expression of nuclear NF-κB p65 significantly reduced in UA group and DDP +UA group. si-p65 group displayed a decrease of cell proliferation ability and led to a significant reduction in the number of SiHa cell colony formation.

Conclusion

The combination of UA with DDP could more effectively inhibit SiHa cells proliferation and facilitate cell apoptosis through suppressing NF-κB p65.

Curcumin improves the paclitaxel-induced apoptosis of HPV-positive human cervical cancer cells via the NF-κB-p53-caspase-3 pathway

Paclitaxel, isolated from Taxus brevifolia, is considered to be an efficacious agent against a wide spectrum of human cancers, including human cervical cancer. However, dose-limiting toxicity and high cost limit its clinical application. Curcumin, a nontoxic food additive, has been reported to improve paclitaxel chemotherapy in mouse models of cervical cancer. However, the underlying mechanisms remain unclear. In this study, two human cervical cancer cell lines, CaSki [human papilloma virus (HPV)16-positive] and HeLa (HPV18-positive), were selected in which to investigate the effect of curcumin on the anticancer action of paclitaxel and further clarify the mechanisms. Flow cytometry and MTT analysis demonstrated that curcumin significantly promoted paclitaxel-induced apoptosis and cytotoxicity in the two cervical cell lines compared with that observed with paclitaxel alone (P<0.05). Reverse transcription-polymerase chain reaction indicated that the decline of HPV E6 and E7 gene expression induced by paclitaxel was also assisted by curcumin. The expression levels of p53 protein and cleaved caspase-3 were increased significantly in the curcumin plus paclitaxel-treated HeLa and CaSki cells compared with those in the cells treated with paclitaxel alone (P<0.01). Significant reductions in the levels of phosphorylation of IκBα and the p65-NF-κB subunit in CaSki cells treated with curcumin and paclitaxel were observed compared with those in cells treated with paclitaxel alone (P<0.05). This suggests that the combined effect of curcumin and paclitaxel was associated with the NF-κB-p53-caspase-3 pathway. In conclusion, curcumin has the ability to improve the paclitaxel-induced apoptosis of HPV-positive human cervical cancer cell lines via the NF-κB-p53-caspase-3 pathway. Curcumin in combination with paclitaxel may provide a superior therapeutic effect on human cervical cancer.

Norspermidine and novel Pd(II) and Pt(II) polynuclear complexes of norspermidine as potential antineoplastic agents against breast cancer

Background

New strategies are needed for breast cancer treatment and one initial step is to test new chemotherapeutic drugs in breast cancer cell lines, to choose candidates for further studies towards clinical use.

Methodology and Findings

The cytotoxic effects of a biogenic polyamine analogue – norspermidine – and its trinuclear Pd(II) and Pt(II) complexes – Pd₃NSpd₂ and Pt₃NSpd₂, respectively – were investigated in one immortalized normal-like and three breast cancer cell lines. The normal-like MCF-10A cells were least sensitive to the compounds, while growth inhibition and cell death was observed in the cancer cell lines. Norspermidine and its Pd(II) complex were generally shown to have stronger antiproliferative effects than the corresponding Pt(II) complex. Moreover, both norspermidine and the Pd(II) complex reduced the cellular activity of the growth-related enzyme, ornithine decarboxylase (ODC) to a lower level than the Pt(II) complex in most of the cell lines examined. Treatment with norspermidine or the Pd(II) complex reduced the number of colonies formed in a soft agar assay performed with the breast cancer cell lines, indicating that these compounds reduced the malignancy of the breast cancer cells. The effect of norspermidine or the Pd(II) complex on colony formation was much stronger than that observed for the Pt(II) complex. The results from a new mammalian genotoxicity screen together with those of a single cell gel electrophoresis assay indicated that none of the drugs were genotoxic at a 25 µM concentration.

Main Conclusions

Overall, norspermidine and its Pd(II) complex were shown to have strong antiproliferative effects. In comparison, the effects obtained with the Pd(II) complex were much stronger than that of the Pt(II) complex. The results obtained in the present study demonstrate that the trinuclear Pd(II) complex of norspermidine (Pd₃NSpd₂) may be regarded as a potential new metal-based drug against breast cancer, coupling a significant efficiency to a low toxicity.

Antiproliferative activity and apoptosis-inducing mechanism of constituents from Toona sinensis on human cancer cells

Background

Natural products, including plants, microorganisms and marines, have been considered as valuable sources for anticancer drug discovery. Many Chinese herbs have been discovered to be potential sources of antitumor drugs.

Methods

In the present study, we investigated the antitumor efficacy of the compounds isolated from Toona sinensis, an important herbal medicine. The inhibitory activities of these compounds were investigated on MGC-803, PC3, A549, MCF-7, and NIH3T3 cells in vitro by MTT assay. The mechanism of the antitumor action of active compounds was investigated through AO/EB staining, Hoechst 33258 staining, TUNEL assay, flow cytometry analysis, and western blotting analysis.

Results

Fifteen compounds were isolated from the roots of Toona sinensis. Betulonic acid (BTA) and 3-oxours-12-en-28-oic acid (OEA) isolated from the plant inhibited the proliferation of MGC-803 and PC3 cells, with IC₅₀ values of 17.7 μM and 13.6 μM, 26.5 μM and 21.9 μM, respectively. Both could lead to cell apoptosis, and apoptosis ratios reached 27.3% and 24.5% in MGC-803 cells at 72 h after treatment at 20 μM, respectively. Moreover, the study of cancer cell apoptotic signaling pathway indicated that both of them could induce cancer cell apoptosis through the mitochondrial pathway, involving the expressions of p53, Bax, caspase 9 and caspase 3.

Conclusions

The study shows that most of the compounds obtained from Toona sinensis could inhibit the growth of human cancer cells. Furthermore, BTA and OEA exhibited potent antitumor activities via induction of cancer cell apoptosis.