Antitumor resistance induced by zinostatin stimalamer (ZSS), a polymer-conjugated neocarzinostatin (NCS) derivative. I. Meth A tumor eradication and tumor-neutralizing activity in mice pretreated with ZSS or NCS

Perspectives on the past, present, and future of cancer nanomedicine

The justification of cancer nanomedicine relies on enhanced permeation (EP) and retention (R) effect and the capability of intracellular targeting due primarily to size after internalization (endocytosis) into the individual target cells. The EPR effect implies improved efficacy. Affinity targeting for solid tumors only occur after delivery to individual cells, which help internalization and/or retention. The design principles have been supported by animal results in numerous publications, but hardly translated. The natures of EP and R, such as frequency of large openings in tumor vasculature and their dynamics, are not understood, in particular, in clinical settings. Although various attempts to address the issues related to EP and delivery, by modifying design factors and manipulating tumor microenvironment, are being reported, they are still verified in artificial rodent tumors which do not mimic the nature of human tumor physiology/pathology in terms of transport and delivery. The clinical trials of experimental nanomedicine have experienced unexpected adverse effects with modest improvement in efficacy when compared to current frontline therapy. Future nanomedicine may require new design principles without consideration of EP and affinity targeting. A possible direction is to set new approaches to intentionally minimize adverse effects, rather than aiming at better efficacy, which can widen the therapeutic window of an anticancer drug of interest. Broadening indications and administration routes of developed therapeutic nanotechnology would benefit patients.

Smart pH-sensitive nanoassemblies with cleavable PEGylation for tumor targeted drug delivery

A new acidly sensitive PEGylated polyethylenimine linked by Schiff base (PEG-s-PEI) was designed to render pH-sensitive PEGylation nanoassemblies through multiple interactions with indomethacin and docetaxel (DTX). DTX nanoassemblies driven by PEG-s-PEI thus formulated exhibited an excellent pH-sensitivity PEGylation cleavage performance at extracellular pH of tumor microenvironment, compared to normal tissues, thereby long circulated in blood but were highly phagocytosed by tumor cells. Consequently, this smart pH-sensitive PEGylation cleavage provided an efficient strategy to target tumor microenvironment, in turn afforded superior therapeutic outcome in anti-tumor activity.

pH-Sensitive Biocompatible Nanoparticles of Paclitaxel-Conjugated Poly(styrene-co-maleic acid) for Anticancer Drug Delivery in Solid Tumors of Syngeneic Mice

In the present study, we have synthesized poly(styrene-co-maleic anhydride), a biocompatible copolymer that was further conjugated with paclitaxel (PTX) via ester linkage and self-assembled to form poly(styrene-co-maleic acid)-paclitaxel (PSMAC-PTX) nanoparticles (NPs). The in vitro release of PTX from PSMAC-PTX NPs showed a higher release at lower pH than at the physiological pH of 7.4, confirming its pH-dependent release. The cell viability of PSMAC-PTX nanoparticles was evaluated using MTT assay. IC50 values of 9.05-18.43 ng/mL of PTX equivalent were observed in various cancer cell lines after 72 h of incubation. Confocal microscopy, Western blotting, and Flow cytometry results further supported that the cellular uptake and apoptosis of cancer cells with PSMAC-PTX NPs. Pharmacokinetic studies revealed that the conjugation of PTX to the PSMAC co-polymer not only increased the plasma and tumor C(max) of PTX but also prolonged its plasma half-life and retention in tumor via enhanced permeability and retention (EPR) effect. Administration of PSMAC-PTX NPs showed significant tumor growth inhibition with improved apoptosis effects in vivo on Ehrlich Ascites Tumor (EAT)-bearing BALB/c syngeneic mice in comparison with Taxol, without showing any cytotoxicity. On the basis of preliminary results, no subacute toxicity was observed in major organs, tissues and hematological system up to a dosage of 60 mg/kg body weight in mice. Therefore, PSMAC-PTX NPs may be considered as an alternative nanodrug delivery system for the delivery of PTX in solid tumors.

Nanopharmaceuticals (part 1): products on the market

In 2000, the National Institute of Health launched the National Nanotechnology Initiative to support, coordinate, and advance research and development of nanoscale projects. The impact of this new program on health-science related research and development became quickly visible. Broad governmental financial support advanced the start of new, and the deepening of already existing, interdisciplinary research. The anticipated merger of nanoscience with medicine quickly instigated the conceptualization of nanomedicine. The adoption of nanoscience terminology by pharmaceutical scientists resulted in the advent of nanopharmaceuticals. The term "nano" became tantamount to "cutting-edge" and was quickly embraced by the pharmaceutical science community. Colloidal drug delivery systems reemerged as nanodrug delivery systems; colloidal gold became a suspension of nano gold particles. In this review, we first review nanoscience related definitions applied to pharmaceuticals, we then discuss all 43 currently approved drug formulations which are publicized as nanopharmaceuticals, and finally we analyze clinical aspects of selected drug formulations.

Changes in cellular composition induced by neocarzinostatin pretreatment in Meth A-bearing mice and the responsible antitumor effector cells

We previously reported that tumor eradication was induced by a single injection of neocarzinostatin (NCS) between 1 day and 4 weeks before Meth A transplantation in Balb/c mice via augmenting host-mediated antitumor activity. In order to elucidate the mechanism of this tumor eradication, the cellular components of spleen and regional lymph nodes, tumor infiltrating cells and antitumor effector cells were investigated. Pretreatment with NCS on day -3 caused an increase in the percentage of T-cell subsets, a decrease in the percentage of B-cells, Mac-1+ cells and asialo GM1+ cells and a decrease of the total cell number in the spleen. These changes were observed before but not during the period of tumor regression and were also observed in non-transplanted mice with NCS treatment. In the lymph nodes, while B-cells increased on Meth A transplantation, this was suppressed by NCS pretreatment. Although histological examination of tumor nodules showed the presence of only a few host immune cells in the tumor tissue, the area of necrosis was already extensive on day 7 and expanded thereafter. In vivo depletion of whole T-cells, T-cell subsets or asialo GM1+ cells by antibody treatment suggests that the antitumor effector cells in tumor eradication were Thy1,2+/Lyt2+, and at least some of which also express asialo GM1 antigen and that L3T4+ T-cells were also involved in tumor eradication.