Trans-[Pt(amine)Cl2(PPh3)] Complexes Target Mitochondria and Endoplasmic Reticulum in Gastric Cancer Cells.

Gastric cancer prognosis is still notably poor despite efforts made to improve diagnosis and treatment of the disease. Chemotherapy based on platinum agents is generally used, regardless of the fact that drug toxicity leads to limited clinical efficacy. In order to overcome these problems, our group has been working on the synthesis and study of trans platinum (II) complexes. Here, we explore the potential use of two phosphine-based agents with the general formula trans-[Pt(amine)Cl2(PPh3)], called P1 and P2 (with dimethylamine or isopropylamine, respectively). A cytotoxicity analysis showed that P1 and especially P2 decrease cell viability. Specifically, P2 exhibits higher activity than cisplatin in gastric cancer cells while its toxicity in healthy cells is slightly lower. Both complexes generate Reactive Oxygen Species, produce DNA damage and mitochondrial membrane depolarization, and finally lead to induced apoptosis. Thus, an intrinsic apoptotic pathway emerges as the main type of cell death through the activation of BAX/BAK and BIM and the degradation of MCL1. Additionally, we demonstrate here that P2 produces endoplasmic reticulum stress and activates the Unfolded Protein Response, which also relates to the impairment observed in autophagy markers such as p62 and LC3. Although further studies in other biological models are needed, these results report the biomolecular mechanism of action of these Pt(II)-phosphine prototypes, thus highlighting their potential as novel and effective therapies.

ERK5 signalling pathway is a novel target of sorafenib: Implication in EGF biology.

Sorafenib is a multikinase inhibitor widely used in cancer therapy with an antitumour effect related to biological processes as proliferation, migration or invasion, among others. Initially designed as a Raf inhibitor, Sorafenib was later shown to also block key molecules in tumour progression such as VEGFR and PDGFR. In addition, sorafenib has been connected with key signalling pathways in cancer such as EGFR/EGF. However, no definitive clue about the molecular mechanism linking sorafenib and EGF signalling pathway has been established so far. Our data in HeLa, U2OS, A549 and HEK293T cells, based on in silico, chemical and genetic approaches demonstrate that the MEK5/ERK5 signalling pathway is a novel target of sorafenib. In addition, our data show how sorafenib is able to block MEK5-dependent phosphorylation of ERK5 in the Ser218/Tyr220, affecting the transcriptional activation associated with ERK5. Moreover, we demonstrate that some of the effects of this kinase inhibitor onto EGF biological responses, such as progression through cell cycle or migration, are mediated through the effect exerted onto ERK5 signalling pathway. Therefore, our observations describe a novel target of sorafenib, the ERK5 signalling pathway, and establish new mechanistic insights for the antitumour effect of this multikinase inhibitor.

The human PKP2/plakophilin-2 gene is induced by Wnt/ß-catenin in normal and colon cancer-associated fibroblasts.

Colorectal cancer results from the malignant transformation of colonic epithelial cells. Stromal fibroblasts are the main component of the tumour microenvironment, and play an important role in the progression of this and other neoplasias. Wnt/ß-catenin signalling is essential for colon homeostasis, but aberrant, constitutive activation of this pathway is a hallmark of colorectal cancer. Here we present the first transcriptomic study on the effect of a Wnt factor on human colonic myofibroblasts. Wnt3A regulates the expression of 1,136 genes, of which 662 are upregulated and 474 are downregulated in CCD-18Co cells. A set of genes encoding inhibitors of the Wnt/ß-catenin pathway stand out among those induced by Wnt3A, which suggests that there is a feedback inhibitory mechanism. We also show that the PKP2 gene encoding the desmosomal protein Plakophilin-2 is a novel direct transcriptional target of Wnt/ß-catenin in normal and colon cancer-associated fibroblasts. PKP2 is induced by ß-catenin/TCF through three binding sites in the gene promoter and one additional binding site located in an enhancer 20 kb upstream from the transcription start site. Moreover, Plakophilin-2 antagonizes Wnt/ß-catenin transcriptional activity in HEK-293T cells, which suggests that it may act as an intracellular inhibitor of the Wnt/ß-catenin pathway. Our results demonstrate that stromal fibroblasts respond to canonical Wnt signalling and that Plakophilin-2 plays a role in the feedback control of this effect suggesting that the response to Wnt factors in the stroma may modulate Wnt activity in the tumour cells.

Hepatitis C virus-mediated Aurora B kinase inhibition modulates inflammatory pathway and viral infectivity.

BACKGROUND & AIMS: Chronic hepatitis C is a leading cause of chronic liver disease, cirrhosis and hepatocellular carcinoma. DNA methylation and histone covalent modifications constitute crucial mechanisms of genomic instability in human disease, including liver fibrosis and hepatocellular carcinoma. The present work studies the consequences of HCV-induced histone modifications in early stages of infection. METHODS: Human primary hepatocytes and HuH7.5 cells were transiently transfected with the core protein of hepatitis C virus (HCV) genotypes 1a, 1b, and 2a. Infectious genotype 2a HCV in culture was also used. RESULTS: We show that HCV and core protein inhibit the phosphorylation of Serine 10 in histone 3. The inhibition is due to the direct interaction between HCV core and Aurora B kinase (AURKB) that results in a decrease of AURKB activity. HCV and core significantly downregulate NF-κB and COX-2 transcription, two proteins with anti-apoptotic and proliferative effects implicated in the control of the inflammatory response. AURKB depletion reduced HCV and core repression of NF-κB and COX-2 gene transcription and AURKB overexpression reversed the viral effect. AURKB abrogation increased HCV specific infectivity which was decreased when AURKB was overexpressed. CONCLUSIONS: The core-mediated decrease of AURKB activity may play a role in the inflammatory pathway during the initial steps of viral infection, while ensuring HCV infectivity.

Platinum iodido drugs show potential anti-tumor activity, affecting cancer cell metabolism and inducing ROS and senescence in gastrointestinal cancer cells.

Cisplatin-based chemotherapy has associated clinical disadvantages, such as high toxicity and resistance. Thus, the development of new antitumor metallodrugs able to overcome different clinical barriers is a public healthcare priority. Here, we studied the mechanism of action of the isomers trans and cis-[PtI2(isopropylamine)2] (I5 and I6, respectively) against gastrointestinal cancer cells. We demonstrate that I5 and I6 modulate mitochondrial metabolism, decreasing OXPHOS activity and negatively affecting ATP-linked oxygen consumption rate. Consequently, I5 and I6 generated Reactive Oxygen Species (ROS), provoking oxidative damage and eventually the induction of senescence. Thus, herein we propose a loop with three interconnected processes modulated by these iodido agents: (i) mitochondrial dysfunction and metabolic disruptions; (ii) ROS generation and oxidative damage; and (iii) cellular senescence. Functionally, I5 reduces cancer cell clonogenicity and tumor growth in a pancreatic xenograft model without systemic toxicity, highlighting a potential anticancer complex that warrants additional pre-clinical studies.

SARS-CoV-2 S Protein Reduces Cytoprotective Defenses and Promotes Human Endothelial Cell Senescence.

Premature vascular aging and endothelial cell senescence are major risk factors for cardiovascular diseases and atherothrombotic disturbances, which are main complications of both acute and long COVID-19. The S protein of SARS-CoV2, which acts as the receptor binding protein for the viral infection, is able to induce endothelial cells inflammation and it has been found as an isolated element in the circulation and in human tissues reservoirs months after infection. Here, we investigated whether the S protein is able to directly induce endothelial cell senescence and deciphered some of the mechanisms involved. In primary cultures of human umbilical vein endothelial cells (HUVEC), SARS-CoV-2 S protein enhanced in a concentration-dependent manner the cellular content of senescence and DNA damage response markers (senescence-associated-ß galactosidase, γH2AX), as well as growth-arrest effectors (p53, p21, p16). In parallel, the S protein reduced the availability of cytoprotective proteins, such as the anti-aging protein klotho, Nrf2 or heme oxygenase-1, and caused functional harm by impairing ex vivo endothelial-dependent vasorelaxation in murine microvessels. These effects were prevented by the pharmacological inhibition of the NLRP3 inflammasome with MCC950. Furthermore, the supplementation with either recombinant klotho or angiotensin-(1-7), equally protected against the pro-senescence, pro-inflammatory and pro-oxidant action of the S protein. Globally, this study proposes novel mechanisms of disease in the context of COVID-19 and its vascular sequelae and provides pharmacological clues in order to prevent such complications.

A select thiosemicarbazone copper(II) complex induces apoptosis in gastric cancer and targets cancer stem cells reducing pluripotency markers.

Copper(II)-based complexes are promising candidates as anti-cancer agents due to their ability to target cancer cells. Here we describe the synthesis and characterization of two copper(II) thiosemicarbazone complexes with the ligands 4-(dimethylamino)benzaldehyde N4-methylthiosemicarbazone (HL1) and 4-(dimethylamino)benzaldehyde N4-(4-(dimethylamino)phenylthiosemicarbazone (HL2) and general formula [Cu(L)2]. The complexes show stability in aqueous solution with 1 % of DMSO that allows to stablish its solution profile in biological buffers. Compound [Cu(L1)2] lipophilicity was lower than [Cu(L2)2], however, its solubility in biological buffer was not only better but also its DLS and ζ-potential data. In vitro studies demonstrate a higher cytotoxic effect of [Cu(L1)2] on gastric cancer cells. The proposed mechanism of action consists in the generation of free radicals that induce DNA lesions, oxidative stress and ultimately autophagy deregulation and apoptosis. Additionally, [Cu(L1)2] is equally active on gastric cancer stem cells and tumor cells resistant to cisplatin. More importantly, stem cells treated with [Cu(L1)2] show a downregulation of pluripotency markers such as TWIST, NANOG and OCT4. Overall, our results with [Cu(L1)2] prompt a significant advancement in the development of rational-designed pharmaceuticals for combating cancer.

Dithiobiureas Palladium(II) complexes' studies: From their synthesis to their biological action.

Dithiobiureas coordination chemistry towards palladium (II) ions and their possible application is presented and discussed. 1,6-(4-Methoxyphenyl)-2,5-dithiobiurea and 1,6-(4-chlorophenyl)-2,5-dithiobiurea afford two Pd(II) complexes with the general formula [Pd2(H2L)Cl2(PPh3)2]. The metal ion forms one chelate ring with the dithiobiurea, and binds to a triphenylphosphine and an additional leaving group cisplatin like. One of the complexes (1) is endowed not only with stability in DMSO and aqua solutions containing a biological buffer but also with cytotoxicity versus gastric cancer cell lines. Complex 1 does not interact covalently to DNA models, neither activates p53 or Checkpoint Kinase 1 key proteins for DNA damage response. Thus, we propose that complex 1 exerts its action by activating Mitogen-Activated Protein Kinases [p38, Extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs)] as cell death inductors.

Mitogen-activated protein kinase phosphatase-1 in human breast cancer independently predicts prognosis and is repressed by doxorubicin.

PURPOSE: Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) dephosphorylates mitogen-activated protein kinase [extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK), and p38], mediates breast cancer chemoresistance, and is repressible by doxorubicin in breast cancer cells. We aimed to characterize doxorubicin effects on MKP-1 and phospho-MAPKs in human breast cancers and to further study the clinical relevance of MKP-1 expression in this disease. EXPERIMENTAL DESIGN: Doxorubicin effects on MKP-1, phospho-ERK1/2 (p-ERK1/2), phospho-JNK (p-JNK), and phospho-p38 were assayed in a panel of human breast cancer cells by Western blot and in human breast cancer were assayed ex vivo by immunohistochemistry (n = 50). MKP-1 expression was also assayed in a range of normal to malignant breast lesions (n = 30) and in a series of patients (n = 96) with breast cancer and clinical follow-up. RESULTS: MKP-1 was expressed at low levels in normal breast and in usual ductal hyperplasia and at high levels in in situ carcinoma. MKP-1 was overexpressed in approximately 50% of infiltrating breast carcinomas. Similar to what was observed in breast cancer cell lines, ex vivo exposure of breast tumors to doxorubicin down-regulated MKP-1, and up-regulated p-ERK1/2 and p-JNK, in the majority of cases. However, in a proportion of tumors overexpressing MKP-1, doxorubicin did not significantly affect MKP-1 or phospho-MAPKs. With regard to patient outcome, MKP-1 overexpression was an adverse prognostic factor for relapse both by univariate (P < 0.001) and multivariate analysis (P = 0.002). CONCLUSIONS: MKP-1 is overexpressed during the malignant transformation of the breast and independently predicts poor prognosis. Furthermore, MKP-1 is repressed by doxorubicin in many human breast cancers.

Targeting MAD2 modulates stemness and tumorigenesis in human Gastric Cancer cell lines.

Rationale: Gastric cancer (GC) is a solid tumor that contains subpopulations of cancer stem cells (CSCs), which are considered drivers of tumor initiation and metastasis; responsible for therapeutic resistance; and promoters of tumor relapse. The balance between symmetric and asymmetric division is crucial for stem cell maintenance. The objective of this study is to evaluate the role of MAD2, a key protein for proper mitotic checkpoint activity, in the tumorigenesis of GC. Methods: Gastric cancer stem cells (GCSCs) were obtained from MKN45, SNU638 and ST2957 cell lines. Pluripotency and stemness markers were evaluated by RT-qPCR and autofluorescence and membrane markers by flow cytometry. Relevant signal transduction pathways were studied by WB. We analysed cell cycle progression, migration and invasion after modulation of MAD2 activity or protein expression levels in these in vitro models. In vivo assays were performed in a nude mouse subcutaneous xenograft model. Results: We found that NANOG, CXCR4 and autofluorescence are common and consistent markers for the GCSCs analysed, with other markers showing more variability. The three main signalling pathways (Wnt/ß-catenin; Hedgehog and Notch) were activated in GCSCs. Downregulation of MAD2 in MKN45CSCs decreased the expression of markers CXCR4, CD133, CD90, LGR5 and VIM, without affecting cell cycle profile or therapy resistance. Moreover, migration, invasion and tumor growth were clearly reduced, and accordingly, we found that metalloprotease expression decreased. These results were accompanied by a reduction in the levels of transcription factors related with epithelial-to-mesenchymal transition. Conclusions: We can conclude that MAD2 is important for GCSCs stemness and its downregulation in MKN45CSCs plays a central role in GC tumorigenesis, likely through CXCR4-SNAI2-MMP1. Thus, its potential use in the clinical setting should be studied as its functions appear to extend beyond mitosis.

Deficit of mitogen-activated protein kinase phosphatase 1 (DUSP1) accelerates progressive hearing loss.

Mitogen-activated protein kinases (MAPK) such as p38 and the c-Jun N-terminal kinases (JNKs) are activated during the cellular response to stress signals. Their activity is regulated by the MAPK-phosphatase 1 (DUSP1), a key component of the anti-inflammatory response. Stress kinases are well-described elements of the response to otic injury and the otoprotective potential of JNK inhibitors is being tested in clinical trials. By contrast, there are no studies exploring the role of DUSP1 in hearing and hearing loss. Here we show that Dusp1 expression is age-regulated in the mouse cochlea. Dusp1 gene knock-out caused premature progressive hearing loss, as confirmed by auditory evoked responses in Dusp1-/- mice. Hearing loss correlated with cell death in hair cells, degeneration of spiral neurons and increased macrophage infiltration. Dusp1-/- mouse cochleae showed imbalanced redox status and dysregulated expression of cytokines. These data suggest that DUSP1 is essential for cochlear homeostasis in the response to stress during ageing.

The angiotensin-(1-7)/Mas receptor axis protects from endothelial cell senescence via klotho and Nrf2 activation.

Endothelial cell senescence is a hallmark of vascular aging that predisposes to vascular disease. We aimed to explore the capacity of the renin-angiotensin system (RAS) heptapeptide angiotensin (Ang)-(1-7) to counteract human endothelial cell senescence and to identify intracellular pathways mediating its potential protective action. In human umbilical vein endothelial cell (HUVEC) cultures, Ang II promoted cell senescence, as revealed by the enhancement in senescence-associated galactosidase (SA-ß-gal+) positive staining, total and telomeric DNA damage, adhesion molecule expression, and human mononuclear adhesion to HUVEC monolayers. By activating the G protein-coupled receptor Mas, Ang-(1-7) inhibited the pro-senescence action of Ang II, but also of a non-RAS stressor such as the cytokine IL-1ß. Moreover, Ang-(1-7) enhanced endothelial klotho levels, while klotho silencing resulted in the loss of the anti-senescence action of the heptapeptide. Indeed, both Ang-(1-7) and recombinant klotho activated the cytoprotective Nrf2/heme oxygenase-1 (HO-1) pathway. The HO-1 inhibitor tin protoporphyrin IX prevented the anti-senescence action evoked by Ang-(1-7) or recombinant klotho. Overall, the present study identifies Ang-(1-7) as an anti-senescence peptide displaying its protective action beyond the RAS by consecutively activating klotho and Nrf2/HO-1. Ang-(1-7) mimetic drugs may thus prove useful to prevent endothelial cell senescence and its related vascular complications.

New Findings in the Signaling Pathways of cis and trans Platinum Iodido Complexes' Interaction with DNA of Cancer Cells.

We have selected a series of aliphatic amine platinum compounds bearing chloride and/or iodide as the leaving groups. The complexes' cytotoxicity and interaction with DNA indicated differences in the reactivity. Now, we are reporting on the analysis of their molecular mechanism of action on gastric cancer cells. Our data reveals differences between them. Chlorido drugs showed similar behavior to cisplatin; they both required p53 to induce apoptosis but only cis-ipa showed DNA damage requirement for apoptosis induction. On the contrary, cis and trans iodido induced cell death independent of p53 activity, and they induced cell death through Bid activation, so their toxicity could be enhanced in a combined treatment with novel Bcl-2 protein family inhibitors. We also report the structural features of the DNA adduct for one of the complexes by X-ray diffraction. These findings represent a step forward in the search for new platinum-derived agents more specific and effective in the treatment of cancer.

The role of the NFkappaB signalling pathway in cancer.

The nuclear factor kappa B (NFkappaB) signalling pathway regulates the expression of hundreds of genes that are involved in different cellular processes such as cell proliferation, survival, stress responses, cellular immunity and inflammation. Its aberrant regulation is involved in several pathologies, but its relevance in cellular transformation and cancer development has been extensively studied. Mutations in the core components of NFkappaB as well as in the cellular machinery that regulates its activation have been found in many types of tumours. On the other hand, its role in promoting cell survival is an important obstacle in many cancer therapies. The development of chemical inhibitors that block NFkappaB activation acting either directly on IKKs or on the proteosome machinery has shown antitumour and proapoptotic activity both in preclinical and clinical studies.

Role of CHK2 in cancer development.

DNA repair pathways enable tumour cells to survive DNA damage induced by external agents such as therapeutic treatments. Signalling cascades involved in these pathways comprise the DNA-dependent protein kinase (DNA-PK), Ataxia-telangiectasia mutated (ATM), ATM and Rad3 related (ATR) and checkpoint kinases I and 2 (Chk1/Chk2), among others. ATM and ATR phosphorylate, respectively, Chk2 and Chk1, leading to activation of checkpoints. Chk2 acts as a signal distributor, dispersing checkpoint signal to downstream targets such as p53, Cdc25A, Cdc25C, BRCA1 and E2F1. A role of Chk2 as a candidate tumour suppressor has been suggested based on both mouse genetics and somatic tumour studies. We will discuss here the possible role of this kinase in human carcinogenesis and the possibility to use it as a target to increment DNA damage in cancer cells in response to DNA-damaging therapies.

XPA, XPC, and XPD Modulate Sensitivity in Gastric Cisplatin Resistance Cancer Cells.

Cisplatin is an election drug widely used in clinic for the treatment of advanced gastric cancer. However, the heterogeneity of the gastric tumors and its resistance to the drugs, make in some cases the response very low and the prognosis unpredictable. In this manuscript we aim to find the molecular processes involved in cisplatin-induced apoptosis in two gastric cancer cell lines with different sensitivity to the treatment: AGS and MKN45. The apoptosis induction is higher in MKN45 than in AGS cells in response to CDDP. The intrinsic apoptotic pathway study revealed that MKN45 cells undergo degradation of Mcl-1 together with an increase of Bid and Bad levels, which results in sensitivity to CDDP. In addition, DNA repair NER pathway is impair in MKN45 cells due to low levels of XPC and the absence of translocation of XPA and XPD to the nucleus after stimuli. Altogether, these results suggest that NER and Bcl-2 protein family proteins are potential targets to improve the response to cisplatin treatment.

Using phosphine ligands with a biological role to modulate reactivity in novel platinum complexes.

Three platinum complexes with cis and trans configuration cis-[Pt(TCEP)2Cl2], cis-[Pt(tmTCEP)2Cl2] and trans-[Pt(TCEP)2Cl2], where TCEP is tris(2-carboxyethyl)phosphine, have been synthesized and fully characterized by usual techniques including single-crystal X-ray diffraction for trans-[Pt(TCEP)2Cl2] and cis-[Pt(tmTCEP)2Cl2]. Here, we also report on an esterification process of TCEP, which takes place in the presence of alcohols, leading to a platinum complex coordinated to an ester tmTCEP (2-methoxycarbonylethyl phosphine) ligand. The stability in solution of the three compounds and their interaction with biological models such as DNA (pBR322 and calf thymus DNA) and proteins (lysozyme and RNase) have also been studied.

Cell stress and MEKK1-mediated c-Jun activation modulate NFkappaB activity and cell viability.

Chemotherapeutic agents such as cisplatin induce persistent activation of N-terminal c-Jun Kinase, which in turn mediates induction of apoptosis. By using a common MAPK Kinase, MEKK1, cisplatin also activates the survival transcription factor NFkappaB. We have found a cross-talk between c-Jun expression and NFkappaB transcriptional activation in response to cisplatin. Fibroblast derived from c-jun knock out mice are more resistant to cisplatin-induced cell death, and this survival advantage is mediated by upregulation of NFkappaB-dependent transcription and expression of MIAP3. This process can be reverted by ectopic expression of c-Jun in c-jun(-/-) fibroblasts, which decreases p65 transcriptional activity back to normal levels. Negative regulation of NFkappaB-dependent transcription by c-jun contributes to cisplatin-induced cell death, which suggests that inhibition of NFkappaB may potentiate the antineoplastic effect of conventional chemotherapeutic agents.

DNA repair inhibitors in cancer treatment.

Chemotherapy and radiation are two important modalities for cancer treatment. Many agents in clinical used have the ability to induce DNA damage, however they may be highly cytotoxic as a secondary effect. Different mechanisms are involved both, in detection and repair of DNA damage. The modulation of these pathways, has a great impact on clinical outcome and is frequently responsible of therapeutic resistance. Therefore, pharmacological inhibition of DNA damage repair pathways has been explored as a useful strategy to enhance chemo and radiosensitivity, thus it could be used for reversing drug resistance. Different agents have shown excellent results in preclinical studies in combination with radiation or chemotherapy. Early phase clinical trials are now being carried out using different DNA repair inhibitors targeting several enzymes such as PARP, DNA-PK or MGMT.