Plitidepsin as an Immunomodulator against Respiratory Viral Infections.

Plitidepsin is a host-targeted compound known for inducing a strong anti-SARS-CoV-2 activity, as well as for having the capacity of reducing lung inflammation. Because IL-6 is one of the main cytokines involved in acute respiratory distress syndrome, the effect of plitidepsin in IL-6 secretion in different in vitro and in vivo experimental models was studied. A strong plitidepsin-mediated reduction of IL-6 was found in human monocyte-derived macrophages exposed to nonproductive SARS-CoV-2.

CD13 as a new tumor target for antibody-drug conjugates: validation with the conjugate MI130110.

Background: In the search for novel antibody-drug conjugates (ADCs) with therapeutic potential, it is imperative to identify novel targets to direct the antibody moiety. CD13 seems an attractive ADC target as it shows a differential pattern of expression in a variety of tumors and cell lines and it is internalized upon engagement with a suitable monoclonal antibody. PM050489 is a marine cytotoxic compound tightly binding tubulin and impairing microtubule dynamics which is currently undergoing clinical trials for solid tumors.

Binding of eEF1A2 to the RNA-dependent protein kinase PKR modulates its activity and promotes tumour cell survival.

Background: Through several not-fully-characterised moonlighting functions, translation elongation factor eEF1A2 is known to provide a fitness boost to cancer cells. Furthermore, eEF1A2 has been demonstrated to confer neoplastic characteristics on preneoplastic, nontumourigenic precursor cells. We have previously shown that eEF1A2 is the target of plitidepsin, a marine drug currently in development for cancer treatment.

MI130004, a Novel Antibody-Drug Conjugate Combining Trastuzumab with a Molecule of Marine Origin, Shows Outstanding Activity against HER2-Expressing Tumors.

In the search for novel payloads to design new antibody-drug conjugates (ADC), marine compounds represent an interesting opportunity given their unique chemical features. PM050489 is a marine compound that binds β-tubulin at a new site and disrupts the microtubule network, hence leading to mitotic aberrations and cell death. PM050489 has been conjugated to trastuzumab via Cys residues through a noncleavable linker, and the resulting ADC, named MI130004, has been studied.

Translation Elongation Factor eEF1A2 is a Novel Anticancer Target for the Marine Natural Product Plitidepsin.

eEF1A2 is one of the isoforms of the alpha subunit of the eukaryotic Elongation Factor 1. It is overexpressed in human tumors and is endowed with oncogenic properties, favoring tumor cell proliferation while inhibiting apoptosis. We demonstrate that plitidepsin, an antitumor agent of marine origin that has successfully completed a phase-III clinical trial for multiple myeloma, exerts its antitumor activity by targeting eEF1A2.

c-Jun N-terminal kinase phosphorylation is a biomarker of plitidepsin activity.

Plitidepsin is an antitumor drug of marine origin currently in Phase III clinical trials in multiple myeloma. In cultured cells, plitidepsin induces cell cycle arrest or an acute apoptotic process in which sustained activation of c-Jun N-terminal kinase (JNK) plays a crucial role. With a view to optimizing clinical use of plitidepsin, we have therefore evaluated the possibility of using JNK activation as an in vivo biomarker of response.

p21 as a transcriptional co-repressor of S-phase and mitotic control genes.

It has been previously described that p21 functions not only as a CDK inhibitor but also as a transcriptional co-repressor in some systems. To investigate the roles of p21 in transcriptional control, we studied the gene expression changes in two human cell systems. Using a human leukemia cell line (K562) with inducible p21 expression and human primary keratinocytes with adenoviral-mediated p21 expression, we carried out microarray-based gene expression profiling.

MYC accelerates p21CIP-induced megakaryocytic differentiation involving early mitosis arrest in leukemia cells.

p21(CIP) is a potent cell cycle inhibitor often up-regulated in differentiation. Protooncogene MYC induces cell growth and proliferation, inhibits differentiation and represses p21(CIP). However, both molecules are involved in processes of polyploidisation, cell size increase, differentiation and senescence.

The mechanism of action of plitidepsin.

Plitidepsin (PharmaMar SA) is a cyclodepsipeptide originally isolated from the Mediterranean tunicate Aplidium albicans, and has demonstrated strong anticancer activity against a large variety of cultured human cancer cells and in xenografted mice. Phase I/II clinical trials of plitidepsin yielded promising results of anticancer activity in patients with cancer. Several studies have revealed that plitidepsin induces cell cycle arrest or apoptosis in a cell type- and dose-dependent manner.

Determination of viability of human cartilage allografts by a rapid and quantitative method not requiring cartilage digestion.

Fresh osteochondral allograft transplantation is increasingly used for the treatment of cartilage pathologies of the knee. It is believed that transplantation success depends on the presence of viable chondrocytes in the graft, but methods to evaluate graft viability require the isolation of chondrocytes by enzymatic digestion of the cartilage and/or the use of radioactive precursors. We have adapted the well-known cell viability assay based on the reduction of tetrazolium derivatives to evaluate cartilage viability.

Plitidepsin has a dual effect inhibiting cell cycle and inducing apoptosis via Rac1/c-Jun NH2-terminal kinase activation in human melanoma cells.

Melanoma is the most aggressive skin cancer and a serious health problem worldwide because of its increasing incidence and the lack of satisfactory chemotherapy for late stages of the disease. The marine depsipeptide Aplidin (plitidepsin) is an antitumoral agent under phase II clinical development against several neoplasias, including melanoma. We report that plitidepsin has a dual effect on the human SK-MEL-28 and UACC-257 melanoma cell lines; at low concentrations ( View Article and Find Full Text PDF

Aplidin induces JNK-dependent apoptosis in human breast cancer cells via alteration of glutathione homeostasis, Rac1 GTPase activation, and MKP-1 phosphatase downregulation.

Aplidin is an antitumor agent in phase II clinical trials that induces apoptosis through the sustained activation of Jun N-terminal kinase (JNK). We report that Aplidin alters glutathione homeostasis increasing the ratio of oxidized to reduced forms (GSSG/GSH). Aplidin generates reactive oxygen species and disrupts the mitochondrial membrane potential.

Inhibitory effect of c-Myc on p53-induced apoptosis in leukemia cells. Microarray analysis reveals defective induction of p53 target genes and upregulation of chaperone genes.

We have previously demonstrated that c-Myc impairs p53-mediated apoptosis in K562 human leukemia cells, which lack ARF. To investigate the mechanisms by which c-Myc protects from p53-mediated apoptosis, we used K562 cells that conditionally express c-Myc and harbor a temperature-sensitive allele of p53. Gene expression profiles of cells expressing wild-type conformation p53 in the presence of either uninduced or induced c-Myc were analysed by cDNA microarrays.

p21Cip1 and p27Kip1 induce distinct cell cycle effects and differentiation programs in myeloid leukemia cells.

The cyclin-dependent kinase (Cdk) inhibitors p21(Cip1) and p27(Kip1) have been proposed to exert redundant functions in cell cycle progression and differentiation programs, although nonoverlapping functions have also been described. To gain further insights into the relevant mechanisms and to detect possible functional differences between both proteins, we conditionally expressed p21(Cip1) and p27(Kip1) in K562, a multipotent human leukemia cell line. Temporal ectopic expression of either p21(Cip1) or p27(Kip1) arrested proliferation, inhibited Cdk2 and Cdk4 activities, and suppressed retinoblastoma phosphorylation.

Postoperative radiotherapy-induced morbidity in rectal cancer.

Objectives: We analyzed long-term morbidity and bowel function alteration after postoperative radiotherapy for rectal cancer following resection with anastomosis.

Patients And Methods: Thirty-seven patients who underwent surgery with intention to cure and a minimal follow-up period of 3 years were included. These patients were divided into two groups: in the first group, 14 patients received postoperative chemo-radiotherapy, 5-fluorouracil plus folinic acid, and 45 Gy plus 5 Gy boost.

Kinetics of myc-max-mad gene expression during hepatocyte proliferation in vivo: Differential regulation of mad family and stress-mediated induction of c-myc.

Mad proteins (Mad1, Mxi1, Mad3, Mad4, Mnt/Rox) are biochemical and biological antagonists of c-Myc oncoprotein. Mad-Max dimers repress the transcription of the same target genes activated by Myc-Max dimers. Despite the critical role of Max and Mad proteins as modulators of c-Myc functions, there are no comparative data on their regulation in vivo.

Myc represses differentiation-induced p21CIP1 expression via Miz-1-dependent interaction with the p21 core promoter.

Inhibition of cellular differentiation is one of the well-known biological activities of c-Myc-family proteins. We show here that Myc represses differentiation-induced expression of the cyclin-dependent kinase (CDK) inhibitor p21CIP1 (CDKN1A, p21), known to play an important role in cell fate decisions during growth and differentiation, in hematopoietic cells. Our results demonstrate that the c-Myc-responsive region is situated in the p21 core promoter.

Karyopherin alpha2: a control step of glucose-sensitive gene expression in hepatic cells.

Glucose is required for an efficient expression of the glucose transporter GLUT2 and other genes. We have shown previously that the intracytoplasmic loop of GLUT2 can divert a signal, resulting in the stimulation of glucose-sensitive gene transcription. In the present study, by interaction with the GLUT2 loop, we have cloned the rat karyopherin alpha2, a receptor involved in nuclear import.

A novel cytosolic dual specificity phosphatase, interacting with glucokinase, increases glucose phosphorylation rate.

A novel protein was cloned from a rat liver cDNA library by interaction with the liver glucokinase. This protein contained 339 residues and possessed a canonical consensus sequence for a dual specificity phosphatase. The recombinant protein was able to dephosphorylate phosphotyrosyl and phosphoseryl/threonyl substrates.

An unusual high-Km hexokinase is expressed in the mhAT3F hepatoma cell line.

In most hepatoma cells, the high-Km GLUT2/glucokinase proteins are replaced by the ubiquitous low-Km GLUT1/hexokinase type I proteins. In the mhAT3F hepatoma cells, the stimulatory effect of glucose on gene expression and glycogen accumulation was not maximal at 5 mmol/liter glucose. This response to high glucose is observed in mhAT3F cells, where GLUT2 was expressed, but not glucokinase (assessed by Northern blotting and reverse transcription-polymerase chain reaction).

Modulation of glycogen phosphorylase activity and fructose 2,6-bisphosphate levels by glibenclamide and meglitinide in isolated rat hepatocytes: a comparative study.

The influence of glibenclamide and meglitinide, or 4-[2-(5-chloro-2-methoxybenzamide)ethyl]-benzoic acid, a compound similar to the nonsulfonylurea moiety of glibenclamide, on glycogen phosphorylase a activity, fructose 2,6-bisphosphate (F-2,6-P2) level, and cytoplasmic free-Ca2+ concentration has been studied in isolated rat hepatocytes. Both glibenclamide and meglitinide caused a transient and dose-dependent activation of glycogen phosphorylase, with half-maximal effects corresponding to 3.7 +/- 1.

Sulfonylureas activate glycogen phosphorylase and increase cytosolic free-Ca2+ levels in isolated rat hepatocytes.

Without causing significant changes in cellular levels of cyclic adenosine monophosphate (cAMP), the addition of either glibenclamide or gliquidone to isolated rat hepatocytes caused a transient dose- and Ca(2+)-dependent activation of glycogen phosphorylase. The calculated concentrations corresponding to half-maximal activation were 5 and 2 mumol/L, respectively. In connection with this, it was observed that glibenclamide provoked a dose-dependent increase in cytosolic free-calcium concentration ([Ca2+]i) in Fura-2-loaded hepatocytes.