Correction: Plyasova et al. Penetration into Cancer Cells via Clathrin-Dependent Mechanism Allows L-Asparaginase from Rhodospirillum rubrum to Inhibit Telomerase. Pharmaceuticals 2020, 13, 286.

In the original publication [...].

Anticancer Cytotoxic Activity of Bispidine Derivatives Associated with the Increasing Catabolism of Polyamines.

Polyamine (PA) catabolism is often reduced in cancer cells. The activation of this metabolic pathway produces cytotoxic substances that might cause apoptosis in cancer cells. Chemical compounds able to restore the level of PA catabolism in tumors could become potential antineoplastic agents. The search for activators of PA catabolism among bicyclononan-9-ones is a promising strategy for drug development. The aim of the study was to evaluate the biological activity of new 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives that have antiproliferative properties by accelerating PA catabolism. Eight bispidine derivatives were synthetized and demonstrated the ability to activate PA catabolism in regenerating rat liver homogenates. However, only three of them demonstrated a potent ability to decrease the viability of cancer cells in the MTT assay. Compounds 4c and 4e could induce apoptosis more effectively in cancer HepG2 cells rather than in normal WI-38 fibroblasts. The lead compound 4e could significantly enhance cancer cell death, but not the death of normal cells if PAs were added to the cell culture media. Thus, the bispidine derivative 4e 3-(3-methoxypropyl)-7-[3-(1H-piperazin-1-yl)ethyl]-3,7-diazabicyclo[3.3.1]nonane could become a potential anticancer drug substance whose mechanism relies on the induction of PA catabolism in cancer cells.

Assessing the biological effects of microwave irradiation on human semen in vitro and determining the role of seminal plasma polyamines in this process.

The aim of the present study was to investigate the influence of millimeter-wave electromagnetic (MW) irradiation on normal and pathological human sperm in vitro, and to evaluate a possible role of polyamines (PA) in this process. The stability of sperm membranes, the number of apoptotic gametes, and the content of seminal plasma PA in the ejaculates of fertile and subfertile men were compared before and after short-term MW electromagnetic exposure in vitro. The ejaculate samples were collected from healthy donors [n=25, age 22-38 years old (y.o.), average age 30.6±1.1 y.o. (mean ± SEM)] and from subfertile men (n=78, age 25-48 y.o., average age 34.1±0.8 y.o.) and exposed to MW radiation. The electromagnetic field had a wavelength of 7.1 mm, a frequency of 42.194 GHz and an exposure time of 20 min. The fragility of sperm membranes was evaluated by their resistance to sodium chloride solution (Milovanov test) and to acetic acid (Joel test). Acrosin activity was assayed spectrophotometrically. Apoptosis was determined by the externalization of phosphatidylserine on the outer side of the sperm membrane and propidium iodide staining. The PA levels were determined by agar gel electrophoretic fractionation. An increase in the resistance of sperm membranes, a decrease in acrosin activity, a decrease in the number of apoptotic gametes and a decrease in the seminal plasma PA concentrations were found after exposure of the native human sperm to low-intensity MW irradiation. Two types of reactions were revealed for the subfertile samples. The results revealed positive bio-effects of specific microwaves on the human semen and the participation of PA in the realization of these effects.

Cytoprotective Activity of Polyamines Is Associated with the Alternative Splicing of RAD51A Pre-mRNA in Normal Human CD4+ T Lymphocytes.

Physiological polyamines are ubiquitous polycations with pleiotropic biochemical activities, including regulation of gene expression and cell proliferation as well as modulation of cell signaling. They can also decrease DNA damage and promote cell survival. In the present study, we demonstrated that polyamines have cytoprotective effects on normal human CD4+ T lymphocytes but not on cancer Jurkat or K562 cells. Pretreatment of lymphocytes with polyamines resulted in a significant reduction in cells with DNA damage induced by doxorubicin, cisplatin, or irinotecan, leading to an increase in cell survival and viability. The induction of RAD51A expression was in response to DNA damage in both cancer and normal cells. However, in normal cells, putrescin pretreatment resulted in alternative splicing of RAD51A and the switch of the predominant expression from the splice variant with the deletion of exon 4 to the full-length variant. Induction of RAD51A alternative splicing by splice-switching oligonucleotides resulted in a decrease in DNA damage and cell protection against cisplatin-induced apoptosis. The results of this study suggest that the cytoprotective activity of polyamines is associated with the alternative splicing of RAD51A pre-mRNA in normal human CD4+ T lymphocytes. The difference in the sensitivity of normal and cancer cells to polyamines may become the basis for the use of these compounds to protect normal lymphocytes during lymphoblastic chemotherapy.

Mechanisms of the Antiproliferative and Antitumor Activity of Novel Telomerase-Carbonic Anhydrase Dual-Hybrid Inhibitors.

Human (h) telomerase (TL; EC 2.7.7.49) plays a key role in sustaining cancer cells by means of elongating telomeric repeats at the 3' ends of chromosomes. Since TL-inhibitor (TI) stand-alone cancer therapy has been proven to be remarkably challenging, a polypharmacological approach represents a valid alternative. Here we consider a series of compounds able to inhibit both hTL and the tumor-associated carbonic anhydrases (CAs; EC 4.2.1.1) IX and XII. Compounds 7 and 9 suppressed hTL activity in both cell lysates and human colon cancer cell lines, and prolonged incubation with either 7 or 9 resulted in telomere shortening, cell cycle arrest, replicative senescence, and apoptosis. Enzyme kinetics showed that 7 and 9 are mixed-type inhibitors of the binding of DNA primers and deoxynucleoside triphosphate (dNTP) to the TL catalytic subunit hTERT, which is in agreement with docking experiments. Compound 9 showed antitumor activity in Colo-205 mouse xenografts and suppressed telomerase activity by telomere reduction.

Penetration into Cancer Cells via Clathrin-Dependent Mechanism Allows L-Asparaginase from Rhodospirillum rubrum to Inhibit Telomerase.

The anticancer effect of L-asparaginases (L-ASNases) is attributable to their ability to hydrolyze L-asparagine in the bloodstream and cancer cell microenvironment. Rhodospirillum rubrum (RrA) has dual mechanism of action and plays a role in the suppression of telomerase activity. The aim of this work was to investigate the possible mechanism of RrA penetration into human cancer cells. Labeling of widely used L-ASNases by fluorescein isothiocyanate followed by flow cytometry and fluorescent microscopy demonstrated that only RrA can interact with cell membranes. The screening of inhibitors of receptor-mediated endocytosis demonstrated the involvement of clathrin receptors in RrA penetration into cells. Confocal microscopy confirmed the cytoplasmic and nuclear localization of RrA in human breast cancer SKBR3 cells. Two predicted nuclear localization motifs allow RrA to penetrate into the cell nucleus and inhibit telomerase. Chromatin relaxation promoted by different agents can increase the ability of RrA to suppress the expression of telomerase main catalytic subunit. Our study demonstrated for the first time the ability of RrA to penetrate into human cancer cells and the involvement of clathrin receptors in this process.

Polyamine Analogues of Propanediamine Series Inhibit Prostate Tumor Cell Growth and Activate the Polyamine Catabolic Pathway.

BACKGROUND/AIM: Polyamines are important for the growth of eukaryotic cells. At high levels, they promote proliferation, invasion and migration of tumour cells. Polyamine metabolism is an important new target for anticancer therapy. Some polyamine analogues can have an inhibitory effect on tumour cells. The aim of this study was to explore the potential of certain butylated derivatives of propanediamine for prostate cancer chemotherapy. MATERIALS AND METHODS: Human prostate cancer cells, LNCaP, were used for the evaluation of the antiproliferative activity of polyamine analogs and their influence on spermine oxidase. RESULTS: Tetrabutyl propanediamine and two new polyamine analogues inhibited the growth of LNCaP cells. At the same time, a strong activation of spermine oxidase was observed. CONCLUSION: The investigated compounds demonstrated their potential value in the therapy of human prostate cancer. Their effect might be attributed to the activation of the polyamine catabolic pathway.