THE UPTAKE OF PROTEINS BY NORMAL AND TUMOUR CELLS IN VITRO

Naturally sourced amphiphilic peptides as paclitaxel vehicles for breast cancer treatment

The marketed paclitaxel (PTX) formulation Taxol relies on the application of Cremophor EL as a solubilizer. The major drawback of Taxol is its hypersensitivity reactions and a pretreatment of anti-allergic drugs is a necessity. Therefore, developing an efficient and safe delivery vehicle is a solution to increase PTX treatment outcomes with minimal adverse effects. In this work, we prepared the amphiphilic peptides (termed AmP) from soybean proteins using a facile two-step method. AmP could efficiently solubilize PTX by self-assembling into mixed micelles with D-α-tocopherol polyethylene glycol succinate (TPGS), a common pharmaceutical expedient (PTX@TPGS-AmP). The intravenously administrated PTX@TPGS-AmP exhibited a slow clearance (0.24 mL·(min·kg)-1) and an enhanced AUC (41.4 μg.h/mL), manifesting a 3.6-fold increase compared to Taxol. In a murine 4T1 tumor model, PTX@TPGS-AmP displayed a superior antitumor effect over Taxol. Importantly, safety assessment showed a high biocompatibility of AmP and an i.v. dose up to 2500 mg/kg led to no observable abnormalities in the mice. In summary, the AmP presents a new green and easily-prepared amphiphilic biomaterial, with promising potential as a pharmaceutical excipient for drug delivery.

Emerging prospects of protein/peptide-based nanoassemblies for drug delivery and vaccine development

Proteins have been widely used in the biomedical field because of their well-defined architecture, accurate molecular weight, excellent biocompatibility and biodegradability, and easy-to-functionalization. Inspired by the wisdom of nature, increasing proteins/peptides that possess self-assembling capabilities have been explored and designed to generate nanoassemblies with unique structure and function, including spatially organized conformation, passive and active targeting, stimuli-responsiveness, and high stability. These characteristics make protein/peptide-based nanoassembly an ideal platform for drug delivery and vaccine development. In this review, we focus on recent advances in subsistent protein/peptide-based nanoassemblies, including protein nanocages, virus-like particles, self-assemblable natural proteins, and self-assemblable artificial peptides. The origin and characteristics of various protein/peptide-based assemblies and their applications in drug delivery and vaccine development are summarized. In the end, the prospects and challenges are discussed for the further development of protein/peptide-based nanoassemblies.

Ferritin drug carrier (FDC) for tumor targeting therapy

Ferritin is an iron storage protein that plays a key role in iron homeostasis and anti-oxidation of cells. Due to its unique architecture of 24 self-assembling subunits and hollow cavity capable of encapsulating drugs, and an outer surface that can be modified genetically and chemically for additional functionality, ferritin has recently emerged as a promising drug delivery vehicle. Recent research demonstrated that unmodified human heavy chain ferritin binds to its receptor, transferrin receptor 1 (TfR1), in different types of tumor tissues, including lung and breast cancer, thus highlighting the potential use of ferritin for tumor-targeting applications. In this review, we consider the many favorable characteristics of ferritin drug carriers (FDCs) for tumor drug delivery. In particular, compared with antibody-drug conjugates (ADCs), ferritin exhibits superiority in a range of attributes, including drug loading ability, thermostability, and ease of production. Thus, the emergence of FDCs may be the next step in targeted cancer therapy.

Human ferritin for tumor detection and therapy

Ferritin, a major iron storage protein found in most living organisms, is composed of a 24-subunit protein cage with a hollow interior cavity. Serum ferritin serves as a critical marker to detect total body iron status. However, recent research reveals a number of novel functions of ferritin besides iron storage; for example, a ferritin receptor, transferrin receptor 1 (TfR1), has been identified and serum ferritin levels are found to be elevated in tumors. A particular new finding is that magnetoferritin nanoparticles, biomimetically synthesized using H-chain ferritin to form a 24-subunit cage with an iron oxide core, possess intrinsic dual functionality, the protein shell specifically targeting tumors and the iron oxide core catalyzing peroxidase substrates to produce a color reaction allowing visualization of tumor tissues. Here we attempt to summarize current research on ferritin, particularly newly identified functions related to tumors, in order to address current challenges and highlight future directions.

THE UPTAKE OF FLUORESCENT LABELLED PROTEINS BY NORMAL AND TUMOUR TISSUES IN VIVO

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Studies of the activities of lysosomal enzymes in serum and buccal pouch tissue of hamsters during 7,12-dimethylbenz[a]anthracene-induced carcinogenesis

Alterations in the activities of certain lysosomal enzymes such as beta-D-galactosidase, beta-D-glucosidase, beta-D-glucuronidase, alpha-L-fucosidase, N-acetyl-beta-D-glucosaminidase, cathepsins B and D were studied in serum and tissue homogenates of buccal mucosa of hamsters treated with 0.5%, 7,12-dimethylbenz[a]anthracene (DMBA) in liquid paraffin. Among the enzymes studied, the activities of beta-D-galactosidase and N-acetyl-beta-D-glucosaminidase showed significant elevation both in serum and tissue homogenates fro papilloma onwards and the elevations were progressive with the development of carcinomas. The elevations in the activities of alpha-D-fucosidase and cathepsin D were found to be significant from papillomatous tissue onwards whereas in serum they showed higher activities only in carcinoma stages. The activities of beta-D-glucosidase, beta-D-glucuronidase and cathepsin B in both serum and in tissue homogenate were elevated markedly only in carcinoma stages. It is suggested that beta-D-galactosidase and N-acetyl-beta-D-glucosaminidase may be used as diagnostic markers for premalignant and malignant lesions of oral mucosa.

Immunohistochemical demonstration of IgG in meningioma

Twenty human meningiomas were examined for IgG and IgM by the direct immunofluorescence of immunoperoxidase methods, or both. IgG was conspicuously found in and around the blood vessels, whorls, and psammoma bodies. It was also clearly present on the cytoplasmic membranes of the tumour cells. On the other hand, IgM was seen only within the blood vessels. Significance of these findings is briefly discussed including possible humoral immune reactions in regard to whorl and psammoma body formation in meningioma.

Tissue distribution and tumour localization of 99m-technetium-labelled liposomes in cancer patients

The possible use of liposomes (phospholipid vesicles) to direct cytotoxic drugs to tumours has led us to investigate the tissue localization of i.v. injected 99m-Tc-labelled liposomes in cancer patients. Twenty mg or 300 mg doses of liposomal lipid (7:2:1 molar ratio of phosphatidylcholine : cholesterol : phosphatidic acid) were used in a study of 13 patients with advanced cancer and one with polycythaemia rubra vera (PRV). In all cases except the patient with PRV the major site of uptake of the label was the liver and spleen. In the patient with PRV the liver uptake was greatly reduced and the major site of uptake was found in regions corresponding to marrow. With the exception of one patient with a primary hepatoma, there was no significant tumour uptake of the label.

Mechanisms of reduction of antitumor drug toxicity by liposome encapsulation

Actinomycin D, when encapsulated within liposomes, has been previously shown to be less toxic to mice than nonencapsulated actinomycin D, but to retain its tumoricidal activity. We have compared the toxic effects of Act D encapsulated either in the aqueous phase or in the lipid phase of liposomes (APL and LPL, respectively), and the nonencapsulated Act D on the blood forming system, on cell proliferation in the intestine, and on antibody production by spleen lymphocytes. At a single dose of 0.4 mg/kg, APL-encapsulated Act D wass less toxic to white blood cells and to the nucleated cells and colony-forming stem cells of the bone marrow. During toxicity in the proliferating intestinal cells, measured by 3H-thymidine incorporation, was reduced by about a factor of 4 with encapsulation in APL, particularly 24 hours after Act D administration. The toxiciaty of LPL-encapsulated Act D to both the blood-forming system and the intestinal proliferating cells was, however, not significantly different from that of the nonencapsulated Act D. Effects of Act D on the antibody production by spleen cells, determined by the "limited hemolysis in agar" assay, showed that immunosuppression was most markedly reduced by liposome encapsulation either in APL or in LPL, when the drug was given one day before the antigen. These findings are important for considerations of liposome application in cancer chemotherapy.

The exfoliating epithelial surface of the uterine cervix. IV: Scanning electron microscopical study in invasive squamous carcinoma of human subjects

The exfoliating epithelial surface of 15 invasive squamous carcinomas of the uterine cervix was investigated with the aid of the scanning electron microscope (SEM). At low magnification (less than or equal to 5,000 X) thirteen tumors presented irregular cobblestone-like structures and the remaining two, irregular intermediate formations (i.e. between cobblestones and mosaics). Cellular overlapping was found in three tumors. At higher magnifications (up to 25,000 X) all 15 tumors showed irregular disorganized structures such as bizarre microvilli with or without fragmented microrugae. Seven tumors had in addition tall finger-shaped protrusions and two rumors crater-like formations covered by irregular microvilli. The SEM structure found in invasive squamous carcinoma differed from the SEM structures earlier reported for the normal squamous or glandular epithelium, squamous metaplasia, dysplasia or carcinoma in situ of the uterine cervix.

Studies on protein uptake by isolated tumor cells. 3. Apparent stimulations due to pH, hypertonicity, polycations, or dehydration and their relation to the enhanced penetration of infectious nucleic acids

Fixation of (131)I-serum albumin by Ehrlich ascites tumor cells in suspensions and sarcoma S-180 monolayers was measured under experimental conditions. Anaerobic incubation and inhibitors of the oxidative metabolism critically restricted the range of glucose concentrations capable of supporting cell life; in glucose concentrations higher than 10(-2)M, Ehrlich cells suffered from their own acid production; in concentrations 10(-2)M, lower than they underwent damage by starvation. Both types of damage were accompanied by increased albumin fixation unrelated to pinocytosis. Different procedures recommended to enhance the uptake of infectious viral RNA by animal cells in culture were tested for their ability to increase albumin uptake. They enhanced the penetration of both albumin and vital dyes and decreased the viability of cell populations. Their effect, therefore, is related to cell damage. It was postulated that reversible damage to cells favors RNA infection by leading to abnormal uptake processes and by decreasing intracellular digestion. This abnormal uptake is different from pinocytosis and also from the massive fixation of albumin to dead cells. The latter phenomenon is due to adsorption by intracellular sites exposed by disruption of the cell membrane. Polycations are able to induce all three forms of fixation depending on the experimental conditions.