Chemosensitivity of conjunctival melanoma cell lines to target-specific chemotherapeutic agents

A review of nemorosone: Chemistry and biological properties

Nemorosone is a bicyclic polyprenylated acylphloroglucinol derivative originally isolated from Clusia spp. and it can be obtained through chemical synthesis employing different synthetic strategies. Since its discovery, it has attracted great attention both from a biological and chemical viewpoint. In the present article, we attempted to review various chemical and biological topics around nemorosone, with an emphasis on its antiproliferative activities. For this purpose, relevant data was collected from different scientific databases including Google Scholar, PubMed, Scopus and ISI Web of Knowledge. This natural compound has shown activity against several types of malignancies such as leukemia, human colorectal, pancreatic, and breast cancer because it modulates multiple molecular pathways. Nemorosone has both cytostatic and cytotoxic activity and it also seems to induce apoptosis and ferroptosis. Additionally, it has antimicrobial capabilities against Gram-positive bacteria and parasites belonging to genus Leishmania. Its promising antiproliferative pre-clinical effects deserve further attention for anticancer and anti-parasitic drug development and translation to the clinic.

Publication trends of research on conjunctival melanoma during 1997–2022: A 25-year bibliometric study

Background

Conjunctival melanoma (CM) is a life-threatening ocular tumor with a high rate of local recurrence and metastasis. Our objective is to analyze research trends in CM field and compare contributions from different countries, institutions and authors.

Methods

We extracted all CM-related publications published from 1997 to 2022 from the Web of Science database and applied Microsoft Excel and VOSviewer to review publication data, analyze publication trends, and visualize relevant data.

Results

A total of 708 publications were identified. The United States contributed the most publications (280) and citations (8,781 times) with the highest H-index value (47). The Ophthalmic Plastic and Reconstructive Surgery, British Journal of Ophthalmology, American Journal of Ophthalmology and Cornea were the most productive journal concerning CM, and Shields CL, Shields JA, Jager MJ as well as Finger PT had published the most papers in the field. Keywords were classified into three clusters: clinical research, management-related research and genetic research. The keywords “primary acquired melanosis”, “metastasis” and “BRAF mutations” were most frequently emerged. According to the average appearing year (AAY), targeted therapy (AAY of 2019.0) and nivolumab (AAY of 2018.7) were identified as the main focuses of the field in the near future.

Conclusion

In the past 25 years, the United States, Germany, England and the Netherlands held the leading position in the CM research. A group of scholars made important contributions to CM research and will continue to guide cutting-edge research. Treatments that have been shown to be effective for advanced cutaneous melanoma, such as targeted therapy and immunotherapy, are potential focuses for future CM research.

Onconase Restores Cytotoxicity in Dabrafenib-Resistant A375 Human Melanoma Cells and Affects Cell Migration, Invasion and Colony Formation Capability

Melanoma is a lethal tumor because of its severe metastatic potential, and serine/threonine-protein kinase B-raf inhibitors (BRAFi) are used in patients harboring BRAF-mutation. Unfortunately, BRAFi induce resistance. Therefore, we tested the activity of onconase (ONC), a cytotoxic RNase variant, against BRAFi-resistant cells to re-establish the efficacy of the chemotherapy. To do so, an A375 dabrafenib-resistant (A375DR) melanoma cell subpopulation was selected and its behavior compared with that of parental (A375P) cells by crystal violet, 5-Bromo-2’-deoxyuridine incorporation, and cleaved poly(ADP-ribose) polymerase 1 (PARP1) western blot measurements. Then, nuclear p65 Nuclear Factor kappaB (NF-κB) and IκB kinases-α/β (IKK) phosphorylation levels were measured. Gelatin zymography was performed to evaluate metalloproteinase 2 (MMP2) activity. In addition, assays to measure migration, invasion and soft agar colony formation were performed to examine the tumor cell dissemination propensity. ONC affected the total viability and the proliferation rate of both A375P and A375DR cell subpopulations in a dose-dependent manner and also induced apoptotic cell death. Among its pleiotropic effects, ONC reduced nuclear p65 NF-κB amount and IKK phosphorylation level, as well as MMP2 activity in both cell subpopulations. ONC decreased cell colony formation, migration, and invasion capability. Notably, it induced apoptosis and inhibited colony formation and invasiveness more extensively in A375DR than in A375P cells. In conclusion, ONC successfully counteracts melanoma malignancy especially in BRAFi-resistant cells and could become a tool against melanoma recurrence.

Effect of simvastatin in different concentrations on free radicals in A-2058 human melanoma malignum cells-EPR studies

The influence of concentration of simvastatin (SIM) on free radicals in A-2058 human melanoma malignum cells was studied. The proliferation assay for melanoma A-2058 cells with SIM in concentration range from 0.1 to 20 µM was performed. SIM in the concentrations of 0.1, 0.3, and 1 μM only slightly changed the growth of A-2058 cells, but the growth of the cells considerably decreased for higher concentrations of SIM. Free radicals in the cells were examined by an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy. o-Semiquinone free radicals with g-factors in the range of 2.0060 to 2.0065 were found in A-2058 cells. The asymmetric broad EPR spectra with linewidths (ΔB_pp ) from 0.87 to 1.25 mT were measured. The fast spin-lattice relaxation processes characterized all the tested cells. The free radical concentrations in the all A-2058 cells cultured with SIM were lower than in the control cells. The quenching of free radicals in A-2058 cells depended on concentration of SIM. This effect was the weakest for concentration of SIM of 3 μM. The strongest decrease of free radical concentration caused SIM in concentration of 1 μM.

Advances in the management of conjunctival melanoma

Malignant melanoma of the conjunctiva is a rare but serious condition. Over the last several years, there have been important advances in the classification, diagnosis, and treatment of this condition. Recent cytogenetic and immunohistochemical studies are increasing understanding of its tumorigenesis. Diagnosis, although still made via histopathology, has been aided with imaging techniques such as ultrasound biomicroscopy and anterior segment optical coherence tomography. Primary treatment consists of surgical excision. But adjuvant treatments with cryotherapy, topical chemotherapy, and radiation therapy have shown increased success. Sentinel lymph node biopsy has shown early promise of detecting micro-metastasis. Long term follow-up of patients with conjunctival melanoma with systemic surveillance is necessary to detect recurrences and metastases.

Asymmetric, stereodivergent synthesis of (-)-clusianone utilizing a biomimetic cationic cyclization

We report a stereodivergent, asymmetric total synthesis of (-)-clusianone in six steps from commercial materials. We implement a challenging cationic cyclization forging a bond between two sterically encumbered quaternary carbon atoms. Mechanistic studies point to the unique ability of formic acid to mediate the cyclization forming the clusianone framework.

Clusianone, a naturally occurring nemorosone regioisomer, uncouples rat liver mitochondria and induces HepG2 cell death

Clusianone is a member of the polycyclic polyprenylated acylphloroglucinol family of natural products; its cytotoxic mechanism is unknown. Clusianone is a structural isomer of nemorosone, which is a mitochondrial uncoupler and a well-known cytotoxic anti-cancer agent; thus, we addressed clusianone action at the mitochondria and its potential cytotoxic effects on cancer cells. In the HepG2 hepatocarcinoma cell line, clusianone induced mitochondrial membrane potential dissipation, ATP depletion and phosphatidyl serine externalization; this later event is indicative of apoptosis induction. In isolated mitochondria from rat liver, clusianone promoted protonophoric mitochondrial uncoupling. This was evidenced by the dissipation of mitochondrial membrane potential, an increase in resting respiration, an inhibition of Ca(2+) influx, stimulation of Ca(2+) efflux in Ca(2+)-loaded mitochondria, a decrease in ATP and NAD(P)H levels, generation of ROS, and swelling of valinomycin-treated organelles in hyposmotic potassium acetate media. The cytotoxic and uncoupling actions of clusianone were appreciably less than those of nemorosone, likely due to the presence of an intra-molecular hydrogen bond with the juxtaposed carbonyl group at the C15 position. Therefore, clusianone is capable of pharmacologically increasing the leakage of protons from the mitochondria and with favorable cytotoxicity in relation to nemorosone.

Recombinant expression, different downstream processing of the disulfide-rich anti-tumor peptide Ranpirnase and its effect on the growth of human glioma cell line SHG-44

Ranpirnase (Onconase) is a frogspawn-derived disulfide-rich peptide with ribonuclease activity that may be used for tumor treatment. In the present study, we established an efficient approach for preparing mature ranpirnase which may be used for research and therapeutic purposes. The designed ranpirnase precursors carried a 6xHis-tag and were recombinantly expressed in Escherichia coli. After S-sulfonation, the precursors were purified by immobilized metal-ion affinity chromatography. Following removal of the tag by aminopeptidase cleavage, cyclization and in vitro oxidative refolding, the mature ranpirnase was obtained with considerable yield, and the yield of mature ranpirnase was ~50-60 mg per liter cultures. In addition, ranpirnase inhibited the growth of human glioma cells SHG-44 in a dose-dependent manner. Thus the present study has provided an efficient approach for the preparation of active ranpirnase and its analogues for future studies.