Paclitaxel: as adjuvant or neoadjuvant therapy in early breast cancer

INHIBITION OF PACLITAXEL AGAINST NEUROGLIOMA CELLS U251 GROWTH AND ITS MECHANISM

Background:

Glioma is the most common primary tumor of the central nervous system, and accounted for about 70% of primary tumors.

Materials and Methods:

In the study, antitumour activity and mechanism of paclitaxel was investigated. Different concentrations of paclitaxel (200, 300, 400 μmol/L) was treated in neuroglioma cellsU251.

Results:

Paclitaxel significantly inhibited neuroglioma cells growth, and promoted its apoptosis. Paclitaxel can block tumour cells in the G2/M phase. In addition, apoptosis-related genes caspase-3 and bax expressions were increased after paclitaxel treatment.

Conclusion:

Our work indicated that paclitaxel displayed strong anti-tumour activity.

Pharmaceuticals that contain polycyclic hydrocarbon scaffolds

This review comprehensively explores approved pharmaceutical compounds that contain polycyclic scaffolds and the properties that these skeletons convey.

Prodigiosin down-regulates survivin to facilitate paclitaxel sensitization in human breast carcinoma cell lines

Prodigiosin is a bacterial metabolite with potent anticancer activity, which is attributed to its proapoptotic effect selectively active in malignant cells. Still, the molecular mechanisms whereby prodigiosin induces apoptosis remain largely unknown. In particular, the role of survivin, a vital inhibitor of apoptosis, in prodigiosin-induced apoptosis has never been addressed before and hence was the primary goal of this study. Our results showed that prodigiosin dose-dependently induced down-regulation of survivin in multiple breast carcinoma cell lines, including MCF-7, T-47D and MDA-MB-231. This down-regulation is mainly regulated at the level of transcription, as prodigiosin reduced the levels of both survivin mRNA and survivin promoter activity but failed to rescue survivin expression when proteasome-mediated degradation is abolished. Importantly, overexpression of survivin rendered cells more resistant to prodigiosin, indicating an essential role of survivin down-regulation in prodigiosin-induced apoptosis. In addition, we found that prodigiosin synergistically enhanced cell death induced by paclitaxel, a chemotherapy drug known to up-regulate survivin that in turn confers its own resistance. This paclitaxel sensitization effect of prodigiosin is ascribed to the lowering of survivin expression, because prodigiosin was shown to counteract survivin induction by paclitaxel and, notably, the sensitization effect was severely abrogated in cells that overexpress survivin. Taken together, our results argue that down-regulation of survivin is an integral component mediating prodigiosin-induced apoptosis in human breast cancer cells, and further suggest the potential of prodigiosin to sensitize anticancer drugs, including paclitaxel, in the treatment of breast cancer.

Paclitaxel: a review of adverse toxicities and novel delivery strategies

Better known as Taxol (Bristol-Myers Squibb), paclitaxel is the first member of the taxane family to be used in cancer chemotherapy. The taxanes exert their cytotoxic effect by arresting mitosis through microtubule stabilization, resulting in cellular apoptosis. The use of paclitaxel as a chemotherapeutic agent has become a broadly accepted option in the treatment of patients with ovarian, breast and non-small cell lung cancers, malignant brain tumors, and a variety of other solid tumors. However, significant toxicities, such as myelosuppression and peripheral neuropathy, limit the effectiveness of paclitaxel-based treatment regimens. This review addresses the toxicities associated with paclitaxel treatment and describes existing and future strategies of paclitaxel administration directed at limiting these toxicities.

Chemosensitization of cancer in vitro and in vivo by nitric oxide signaling

PURPOSE

Hypoxia contributes to drug resistance in solid cancers, and studies have revealed that low concentrations of nitric oxide (NO) mimetics attenuate hypoxia-induced drug resistance in tumor cells in vitro. Classic NO signaling involves activation of soluble guanylyl cyclase, generation of cyclic GMP (cGMP), and activation of cGMP-dependent protein kinase. Here, we determined whether chemosensitization by NO mimetics requires cGMP-dependent signaling and whether low concentrations of NO mimetics can chemosensitize tumors in vivo.

EXPERIMENTAL DESIGN

Survival of human prostate and breast cancer cells was assessed by clonogenic assays following exposure to chemotherapeutic agents. The effect of NO mimetics on tumor chemosensitivity in vivo was determined using a mouse xenograft model of human prostate cancer. Drug efflux in vitro was assessed by measuring intracellular doxorubicin-associated fluorescence.

RESULTS

Low concentrations of the NO mimetics glyceryl trinitrate (GTN) and isosorbide dinitrate attenuated hypoxia-induced resistance to doxorubicin and paclitaxel. Similar to hypoxia-induced drug resistance, inhibition of various components of the NO signaling pathway increased resistance to doxorubicin, whereas activation of the pathway with 8-bromo-cGMP attenuated hypoxia-induced resistance. Drug efflux was unaffected by hypoxia and inhibitors of drug efflux did not significantly attenuate hypoxia-induced chemoresistance. Compared with mice treated with doxorubicin alone, tumor growth was decreased in mice treated with doxorubicin and a transdermal GTN patch. The presence of GTN and GTN metabolites in plasma samples was confirmed by gas chromatography.

CONCLUSION

Tumor hypoxia induces resistance to anticancer drugs by interfering with endogenous NO signaling and reactivation of NO signaling represents a novel approach to enhance chemotherapy.

Cationic antimicrobial peptides as novel cytotoxic agents for cancer treatment

Cancer treatment by conventional chemotherapy is hindered by toxic side effects and the frequent development of multi-drug resistance by cancer cells. Cationic antimicrobial peptides (CAPs) are a promising new class of natural-source drugs that may avoid the shortcomings of conventional chemotherapy because certain CAPs exhibit selective cytotoxicity against a broad spectrum of human cancer cells, including neoplastic cells that have acquired a multi-drug-resistant phenotype. Tumour cell killing by CAPs is usually by a cell membrane-lytic effect, although some CAPs can trigger apoptosis in cancer cells via mitochondrial membrane disruption. Furthermore, certain CAPs are potent inhibitors of blood vessel development (angiogenesis) that is associated with tumour progression. This article reviews the mechanisms by which CAPs exert anticancer activity and discusses the potential application of selected CAPs as therapeutic agents for the treatment of human cancers.

Intravenous administration of paclitaxel in Sprague-Dawley rats: what is a safe dose?

Few studies describe the administration of Taxol to rats; however, rats are typically used to study the toxicity of new drugs or novel formulations. A dose finding study was conducted to determine a safe dose of Taxol following intravenous administration in rats. Male Sprague-Dawley rats received a bolus of paclitaxel 5-20 mg/kg i.v. Blood was drawn before administration and at the following times after administration: 0.5, 1, 2, 3, 4, 6, 8, 12, 16, 20 and 24 h. Plasma concentrations were determined using high performance liquid chromatography. Two rats received paclitaxel 20 mg/kg and died immediately. Nine rats received paclitaxel 10 mg/kg; seven of these rats died within 12 h and two rats were killed due to moribund conditions. Ten rats received paclitaxel 5 mg/kg with no morbidity. The following pharmacokinetics for paclitaxel in the plasma were estimated: C0, 8977 ng/ml; AUC(0 --> infinity), 7477 ng*h/ml; CL(s), 668 ml/h*kg; V(ss), 1559 ml/kg; V(z) 2557 ml/kg and t(1/2), 2.6 h. It is concluded that further pharmacokinetic studies that are rationally designed to include appropriate measures of preclinical toxicity associated with paclitaxel are needed to identify formally the safest dose in rats following intravenous administration; however, these data indicate that male Sprague-Dawley rats can safely receive Taxol in a 5 mg/kg i.v. bolus.

Emerging issues in traditional Chinese medicine

Traditional Chinese medicine (TCM) has many beneficial effects and has been practiced for several thousand years. It is known to treat the cause of a disease rather than to alleviate its symptoms. Based on a belief that TCM is natural, safe, and of lower cost, consumers worldwide are spending more out-of-pocket money on this form of therapy. This increased spending, and reports of adverse reactions, has drawn the attention of many regulatory agencies. Scientists have called for more evidence-based and scientific research on the risks and benefits of TCM. In Canada, the Natural Health Product Regulations came into effect January 2004. TCM herbal product manufacturers will need to provide products of reputable quality to the market. Many will apply modern technology and good science to support their products. The issues facing producers, scientists, and consumers alike are quality control and assessment, standardization of bioactive components, mechanisms of actions, and integration of the evolved modern Chinese medicine into the healthcare system. Solid science, better regulation of the final product, and better education of consumers are necessary to extract the best of TCM to complement existing conventional medicine to deliver the best healthcare.Key words: bioactive components, chromatographic fingerprinting, integration, mechanisms, Natural Health Product (NHP) Regulations, standardization, traditional Chinese medicine.