Different pH dependency of mitomycin C activity in monolayer and three-dimensional cultures

Evidence of nigericin as a potential therapeutic candidate for cancers: A review

Emerging studies have shown that nigericin, an H⁺, K⁺ and Pb²⁺ ionophore, has exhibited a promising anti-cancer activity in various cancers. However, its anti-cancer mechanisms have not been fully elucidated. In this review, the recent progresses on the use of nigericin in human cancers have been summarized. By exchanging H⁺ and K⁺ across cell membranes, nigericin shows promising anti-cancer activities in in vitro and in vivo as a single agent or in combination with other anti-cancer drugs through decreasing intracellular pH (pHi). The underlying mechanisms of nigericin also include the inactivation of Wnt/β-catenin signals, blockade of Androgen Receptor (AR) signaling, and activation of Stress-Activated Protein Kinase/c-Jun N-terminal Kinase (SAPK/JNK) signaling pathways. In many cancers, nigericin is proved to specifically target putative Cancer Stem Cells (CSCs), and its synergistic effects on photodynamic therapy are also reported. Other mechanisms of nigericin including influencing the mitochondrial membrane potentials, inducing an increase in drug accumulation and autophagy, controlling insulin accumulation in nuclei, and increasing the cytotoxic activity of liposome-entrapped drugs, are also discussed. Notably, the potential adverse effects such as teratogenic effects, insulin resistance and eryptosis shall not be ignored. Taken together, these reports suggest that treatment of cancer cells with nigericin may offer a novel therapeutic strategy and future potential of translation to clinics.

Means to increase the therapeutic efficiency of magnetic heating of tumors

The treatment of tumors

Current animal models of bladder cancer: Awareness of translatability (Review)

Experimental animal models are crucial in the study of biological behavior and pathological development of cancer, and evaluation of the efficacy of novel therapeutic or preventive agents. A variety of animal models that recapitulate human urothelial cell carcinoma have thus far been established and described, while models generated by novel techniques are emerging. At present a number of reviews on animal models of bladder cancer comprise the introduction of one type of method, as opposed to commenting on and comparing all classifications, with the merits of a certain method being explicit but the shortcomings not fully clarified. Thus the aim of the present study was to provide a summary of the currently available animal models of bladder cancer including transplantable (which could be divided into xenogeneic or syngeneic, heterotopic or orthotopic), carcinogen-induced and genetically engineered models in order to introduce their materials and methods and compare their merits as well as focus on the weaknesses, difficulties in operation, associated problems and translational potential of the respective models. Findings of these models would provide information for authors and clinicians to select an appropriate model or to judge relevant preclinical study findings. Pertinent detection methods are therefore briefly introduced and compared.

Single early instillation of mitomycin C and urinary alkalinization in low-risk non-muscle-invasive bladder cancer: a preliminary study

Background

The purpose of this study was to determine the effectiveness of a single early instillation of mitomycin C (MMC) after transurethral resection of bladder tumor (TURBT) together with urinary alkalinization in patients with low-risk non-muscle-invasive bladder cancer (NMIBC).

Methods

Between February 2006 and November 2010, patients diagnosed as having a primary bladder tumor were randomized into standard and optimized treatment groups. The treatment groups were formed prospectively from patients with NMIBC according to results of pathological examination postoperatively, whereas the control group was formed retrospectively. Patients in the standard group (n = 11) were given intravesical MMC 40 mg in the first 6 hours after TURBT, while the patients in the optimized group (n = 15) underwent urinary alkalinization prior to MMC. In the control group (n = 23), no drug treatment was given. The patients were followed after surgery at months 3 and 12, and then annually for the first 5 years using cystoscopy and ultrasound. Time to recurrence and recurrence-free survival rates were calculated.

Results

There were no statistically significant differences between the standard and optimized groups, between the control and optimized groups, or between the control and standard groups in terms of mean recurrence-free survival rates (P = 0.132, 0.645, and 0.173, respectively). The mean time to recurrence was 34.8 (range 28.5–41.1) months in the optimized group and 51.8 (range 44.3–59.2) months in the control group. There was no recurrence during the follow-up period in the standard group.

Conclusion

The results of this preliminary study could not demonstrate the efficacy of urinary alkalinization before a single dose of early MMC following TURBT to increase the effectiveness of the MMC, so we did not continue the study further.

Intravesical therapy for bladder cancer

IMPORTANCE OF THE FIELD

Although transurethral resection of bladder tumor (TURBT) is effective therapy, up to 45% of patients will have a recurrence within 1 year after TURBT alone. Further, there is a 3 - 15% risk of tumor progression to muscle invasive and/or metastatic cancer. Depending on patient and tumor characteristics, a number of patients may benefit from some form of intravesical therapy. Adjuvant therapy is effective in avoiding post-TURBT implantation of tumor cells, eradicating residual disease, preventing tumor recurrence, and to delay or reduce tumor progression through direct cytoablation or immunostimulation.

AREAS COVERED IN THIS REVIEW

The role of risk assessment in the management of nonmuscle invasive bladder cancer (NMIBC) and the indications for the use of intravesical agents are discussed. Findings from major randomized clinical trials on BCG, interferon and various chemotherapeutic agents are summarized; key aspects of drug pharmacology, drug efficacy, side effects, and toxicity are also covered.

WHAT THE READER WILL GAIN

The reader will gain a basic understanding of the role of risk assessment in determining the need for intravesical therapy, as well as an overview of the different types of agents in use in the United States today.

TAKE HOME MESSAGE

The type of intravesical therapy used is based on the risk groups as noted in the European prognostic tables. Bacillus Calmette-Guerin (BCG) is the most commonly used first-line agent immunotherapeutic agent for prophylaxis and treatment of carcinoma in situ and high-grade bladder cancer. Other immunotherapeutic options include the interferons, interleukins 2 and 12, and tumor necrosis factor, all of which have activity in BCG refractory patients, although with low durable remission rates. Studies have shown that chemotherapy prevents recurrence but not progression. The available data on intravesical chemotherapy do not indicate that any single agent currently in use is clearly better than any other. Therefore, the selection of a chemotherapeutic agent is usually based on cost, toxicity, and availability as well as on physician preference and experience.

Intravesical treatments of bladder cancer: review

For bladder cancer, intravesical chemo/immunotherapy is widely used as adjuvant therapies after surgical transurethal resection, while systemic therapy is typically reserved for higher stage, muscle-invading, or metastatic diseases. The goal of intravesical therapy is to eradicate existing or residual tumors through direct cytoablation or immunostimulation. The unique properties of the urinary bladder render it a fertile ground for evaluating additional novel experimental approaches to regional therapy, including iontophoresis/electrophoresis, local hyperthermia, co-administration of permeation enhancers, bioadhesive carriers, magnetic-targeted particles and gene therapy. Furthermore, due to its unique anatomical properties, the drug concentration-time profiles in various layers of bladder tissues during and after intravesical therapy can be described by mathematical models comprised of drug disposition and transport kinetic parameters. The drug delivery data, in turn, can be combined with the effective drug exposure to infer treatment efficacy and thereby assists the selection of optimal regimens. To our knowledge, intravesical therapy of bladder cancer represents the first example where computational pharmacological approach was used to design, and successfully predicted the outcome of, a randomized phase III trial (using mitomycin C). This review summarizes the pharmacological principles and the current status of intravesical therapy, and the application of computation to optimize the drug delivery to target sites and the treatment efficacy.

Intravesical therapy of superficial bladder cancer

The aim of treatment of superficial bladder cancer with intravesical therapy is threefold: (1) Eradicate existing disease. (2) Prevention of recurrence. (3) Prevention of tumor progression. The prognostic factors allow differentiation in different risk groups and this is useful in planning treatment. Studies on pharmacokinetics have proved the efficacy of optimized drug delivery. Comparing resection with and without intravesical chemotherapy a short term approximately 15% decrease in tumor recurrence with chemotherapy can be obtained but no effect on progression was proven. No agent has proved more effective than the other. Single, early instillation of chemotherapy has proven effective but the role of maintenance therapy has been controversial. Immunotherapy in the form of Bacillus Calmette-Guerin generally have proven more efficacious than chemotherapy. The results in comparison to mitomycin C have not been as conclusive. Several new approaches are explored to improve the efficacy of this therapy.

A novel strategy for NQO1 (NAD(P)H:quinone oxidoreductase, EC 1.6.99.2) mediated therapy of bladder cancer based on the pharmacological properties of EO9

The indolequinone EO9 demonstrated good preclinical activity but failed to show clinical efficacy against a range of tumours following intravenous drug administration. A significant factor in EO9's failure in the clinic has been attributed to its rapid pharmacokinetic elimination resulting in poor drug delivery to tumours. Intravesical administration of EO9 would circumvent the problem of drug delivery to tumours and the principal objective of this study is to determine whether or not bladder tumours have elevated levels of the enzyme NQO1 (NAD(P)H:quinone oxidoreductase) which plays a key role in activating EO9 under aerobic conditions. Elevated NQO1 levels in human bladder tumour tissue exist in a subset of patients as measured by both immunohistochemical and enzymatic assays. In a panel of human tumour cell lines, EO9 is selectively toxic towards NQO1 rich cell lines under aerobic conditions and potency can be enhanced by reducing extracellular pH. These studies suggest that a subset of bladder cancer patients exist whose tumours possess the appropriate biochemical machinery required to activate EO9. Administration of EO9 in an acidic vehicle could be employed to reduce possible systemic toxicity as any drug absorbed into the blood stream would become relatively inactive due to an increase in pH.

Antiproliferative and cytotoxic effects of geldanamycin, cytochalasin E, suramin and thiacetazone in human prostate xenograft tumor histocultures

PURPOSE

We have shown that the three human prostate xenograft tumors, i.e. the androgen-dependent CWR22 tumor, and the androgen-resistant CWR22R and CWR91 tumors, are comparable to patient tumors in their expression of prostate specific antigen, multidrug resistance p-glycoprotein, p53 and Bcl-2 and in their sensitivity to doxorubicin and paclitaxel. The present study used histocultures of these xenograft tumors to evaluate the antiproliferative and cytotoxic effects of several drugs (geldanamycin, cytochalasin E and thiacetazone), which have diverse action mechanisms and have shown activity against primary cultures of human prostate cancer cells. Suramin, a clinically active compound was included for comparison. Methods. The antiproliferative effect of 96 h drug treatment was measured by inhibition of DNA precursor incorporation, and the cytotoxic or cell kill effect was measured by in situ DNA end labeling of apoptotic and necrotic cells and by reduction of live cell density.

RESULTS

The rank order of molar potency was geldanamycin > cytochalasin E > suramin > or = thiacetazone. Thiacetazone produced antiproliferation only in CWR22 tumor and had no cytotoxicity, whereas the other three drugs produced both antiproliferation and cytotoxicity in all three tumors. Geldanamycin, but not cytochalasin E and suramin, showed greater antiproliferation and cytotoxicity in tumor cells compared to normal stromal cells. The two androgen-resistant tumors were 4 to >40-fold less sensitive than the androgen-dependent tumor to drug-induced antiproliferation but were about equally or 4 to >20-fold more sensitive to drug-induced cytotoxicity. The ratios of drug concentrations that produced 50% antiproliferation to the concentrations that produced 50% cytotoxicity ranged from <0.04 to 0.3 in CWR22 tumor, but ranged from 0.3 to 2.7 in CWR22R and CWR91 tumors, indicating a shift from antiproliferation as the predominant drug effect in the androgen-dependent tumor to cytotoxicity in the androgen-resistant tumors.

CONCLUSIONS

Our results indicate (a) differential drug effects in human prostate xenograft tumors with antiproliferation and cytotoxicity as the predominant drug effect in the androgen-dependent and androgen-resistant tumors, respectively, (b) that progression of tumors from androgen-dependent state to androgen-resistant state appears to be associated with a lower sensitivity to drug-induced antiproliferation and an equal or greater sensitivity to drug-induced cytotoxicity, and (c) that geldanamycin but not thiacetazone warrants further development.