Ran signaling in melanoma: implications for the development of alternative therapeutic strategies

G Protein-Coupled Receptors as Potential Intercellular Communication Mediators in Trypanosomatidae

Detection and transduction of environmental signals, constitute a prerequisite for successful parasite invasion; i.e., Leishmania transmission, survival, pathogenesis and disease manifestation and dissemination, with diverse molecules functioning as inter-cellular signaling ligands. Receptors [i.e., G protein-coupled receptors (GPCRs)] and their associated transduction mechanisms, well conserved through evolution, specialize in this function. However, canonical GPCR-related signal transduction systems have not been described in Leishmania, although orthologs, with reduced domains and function, have been identified in Trypanosomatidae. These inter-cellular communication means seem to be essential for multicellular and unicellular organism’s survival. GPCRs are flexible in their molecular architecture and may interact with the so-called receptor activity-modifying proteins (RAMPs), which modulate their function, changing GPCRs pharmacology, acting as chaperones and regulating signaling and/or trafficking in a receptor-dependent manner. In the skin, vasoactive- and neuro- peptides released in response to the noxious stimuli represented by the insect bite may trigger parasite physiological responses, for example, chemotaxis. For instance, in Leishmania (V.) braziliensis, sensory [Substance P, SP, chemoattractant] and autonomic [Vasoactive Intestinal Peptide, VIP, and Neuropeptide Y, NPY, chemorepellent] neuropeptides at physiological levels stimulate in vitro effects on parasite taxis. VIP and NPY chemotactic effects are impaired by their corresponding receptor antagonists, suggesting that the stimulated responses might be mediated by putative GPCRs (with essential conserved receptor domains); the effect of SP is blocked by [(D-Pro 2, D-Trp7,9]-Substance P (10^-6 M)] suggesting that it might be mediated by neurokinin-1 transmembrane receptors. Additionally, vasoactive molecules like Calcitonin Gene-Related Peptide [CGRP] and Adrenomedullin [AM], exert a chemorepellent effect and increase the expression of a 24 kDa band recognized in western blot analysis by (human-)-RAMP-2 antibodies. In-silico search oriented towards GPCRs-like receptors and signaling cascades detected a RAMP-2-aligned sequence corresponding to Leishmania folylpolyglutamate synthase and a RAMP-3 aligned protein, a hypothetical Leishmania protein with yet unknown function, suggesting that in Leishmania, CGRP and AM activities may be modulated by RAMP- (-2) and (-3) homologs. The possible presence of proteins and molecules potentially involved in GPCRs cascades, i.e., RAMPs, signpost conservation of ancient signaling systems associated with responses, fundamental for cell survival, (i.e., taxis and migration) and may constitute an open field for description of pharmacophores against Leishmania parasites.

Ran GTPase is an independent prognostic marker in malignant melanoma which promotes tumour cell migration and invasion

AIMS

Ran GTPase is involved in nucleocytoplasmic shuttling of proteins and is overexpressed in several cancers. The expression of Ran in malignant melanoma (MM) and its functional activity have not been described and were investigated in this study.

METHODS

The prognostic value of Ran expression was tested in a series of 185 primary cutaneous MM cases using immunohistochemistry. The functional activity of Ran was investigated in the two melanoma cell lines. Ran expression was knocked down using two siRNAs and the effect on the expression of the c-Met oncogene, a potential downstream target of Ran, was tested. Functional effects of Ran knockdown on cell motility and cell proliferation were also assessed.

RESULTS

Positive Ran expression was seen in 12.4% of MM and was associated with advanced clinical stage and greater Breslow thickness. Positive expression was an independent marker of shorter overall survival (p=0.023). Knockdown of Ran results in decreased expression of c-Met and the downstream c-met signalling targets ERK1/2. There was a significant reduction in cell migration (p<0.001) and cell invasion (p<0.001). c-Met knockdown decreased the expression of Ran through MAPK and PI3K-AKT in A375 cell line, inhibited the cell viability and migration of both A375 and G361 melanoma cell lines while invasion was enhanced.

CONCLUSION

Ran is a poor prognostic marker in cutaneous MM. It upregulates expression of the oncogene c-Met and, possibly through this, it promotes cell motility which may in turn promote metastasis.

Subversion of Ras Small GTPases in Cutaneous Melanoma Aggressiveness

The rising incidence and mortality rate associated with the metastatic ability of cutaneous melanoma represent a major public health concern. Cutaneous melanoma is one of the most invasive human cancers, but the molecular mechanisms are poorly understood. Moreover, currently available therapies are not efficient in avoiding melanoma lethality. In this context, new biomarkers of prognosis, metastasis, and response to therapy are necessary to better predict the disease outcome. Additionally, the knowledge about the molecular alterations and dysregulated pathways involved in melanoma metastasis may provide new therapeutic targets. Members of the Ras superfamily of small GTPases regulate various essential cellular activities, from signaling to membrane traffic and cytoskeleton dynamics. Therefore, it is not surprising that they are differentially expressed, and their functions subverted in several types of cancer, including melanoma. Indeed, Ras small GTPases were found to regulate melanoma progression and invasion. Hence, a better understanding of the mechanisms regulated by Ras small GTPases that are involved in melanoma tumorigenesis and progression may provide new therapeutic strategies to block these processes. Here, we review the current knowledge on the role of Ras small GTPases in melanoma aggressiveness and the molecular mechanisms involved. Furthermore, we summarize the known involvement of these proteins in melanoma metastasis and how these players influence the response to therapy.

Sequenced Combinations of Cisplatin and Selected Phytochemicals towards Overcoming Drug Resistance in Ovarian Tumour Models

In the present study, cisplatin, artemisinin, and oleanolic acid were evaluated alone, and in combination, on human ovarian A2780, A2780^ZD0473R, and A2780^cisR cancer cell lines, with the aim of overcoming cisplatin resistance and side effects. Cytotoxicity was assessed by MTT reduction assay. Combination index (CI) values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. Moreover, 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780^cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism, and biosynthetic processes and drug resistance and detoxification. Results indicate that appropriately sequenced combinations of cisplatin with artemisinin (ART) and oleanolic acid (OA) may provide a means to reduce side effects and circumvent platinum resistance.

The association of RAN and RANBP2 gene polymerphisms with Wilms tumor risk in Chinese children

Wilms tumor is considered to be the most common renal malignancy among children. RAN, a member of RAS superfamily, and its binding partner RANBP2 are related to the progression of multiple tumors. Nevertheless, the effects of the RAN and RANBP2 gene polymorphisms on the tumorigenesis of Wilms tumor remain unclarified. In this study, three potentially functional polymorphisms (rs56109543 C>T, rs7132224 A>G, and rs14035 C>T) in the RAN and one (rs2462788 C>T) in the RANBP2 were chosen to investigate their association with Wilms tumor susceptibility. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to assess the association of the selected polymorphisms with Wilms tumor susceptibility. Results shown that RAN rs7132224 AG/GG genotypes significantly increased Wilms tumor risk when compared to AA genotype (adjusted OR=1.40, 95% CI=1.01-1.95, P=0.047). Carriers of 1-3 risk genotypes have a significantly higher Wilms tumor risk than those without risk genotype (adjusted OR=1.49, 95% CI=1.07-2.07, P=0.020). Moreover, stratified analysis indicated that RAN rs56109543 CT/TT genotypes, RAN rs7132224 AG/GG genotypes and RANBP2 rs2462788 CT/TT genotypes remarkably increased Wilms tumor susceptibility among the subgroups. Our results indicated that RAN and RANBP2 polymorphisms were associated with Wilms tumor susceptibility in Chinese children. The role of RAN/RANBP2 in cancers deserves more attention.

Conceptual Evolution of Cell Signaling

During the last 100 years, cell signaling has evolved into a common mechanism for most physiological processes across systems. Although the majority of cell signaling principles were initially derived from hormonal studies, its exponential growth has been supported by interdisciplinary inputs, e.g., from physics, chemistry, mathematics, statistics, and computational fields. As a result, cell signaling has grown out of scope for any general review. Here, we review how the messages are transferred from the first messenger (the ligand) to the receptor, and then decoded with the help of cascades of second messengers (kinases, phosphatases, GTPases, ions, and small molecules such as cAMP, cGMP, diacylglycerol, etc.). The message is thus relayed from the membrane to the nucleus where gene expression ns, subsequent translations, and protein targeting to the cell membrane and other organelles are triggered. Although there are limited numbers of intracellular messengers, the specificity of the response profiles to the ligands is generated by the involvement of a combination of selected intracellular signaling intermediates. Other crucial parameters in cell signaling are its directionality and distribution of signaling strengths in different pathways that may crosstalk to adjust the amplitude and quality of the final effector output. Finally, we have reflected upon its possible developments during the coming years.

Anti-Invasive and Anti-Proliferative Effects of shRNA-Loaded Poly(Lactide-Co-Glycolide) Nanoparticles Following RAN Silencing in MDA-MB231 Breast Cancer Cells

Background

Overexpression of the RAN GTP (RAN) gene has been shown to be linked to metastatic activity of MDA-MB231 human breast cancer cells by increasing Ras/MEK/ERK and PI3K/Akt/mTORC1 signalling. The aim of this study was to investigate the potential of polymeric nanoparticles to deliver two novel shRNA sequences, targeted against the RAN gene, to MDA-MB231 cells grown in culture and to assess their effects in a range of biological assays.

Methods

Biodegradable PLGA nanoparticles, loaded with shRNA-1 and shRNA-4, were fabricated using a double emulsion solvent evaporation technique and characterised for size, zeta potential and polydispersity index before testing on the MDA-MB231 cell line in a range of assays including cell viability, migration, invasion and gene knock down.

Results

shRNA-loaded nanoparticles were successfully fabricated and delivered to MDA-MB231 cells in culture, where they effectively released their payload, causing a decrease in both cell invasion and cell migration by knocking down RAN gene expression.

Conclusion

Results indicate the anti-RAN shRNA-loaded nanoparticles deliver and release biological payload to MDA-MB231 cells in culture. This works paves the way for further investigations into the possible use of anti-RAN shRNA-loaded NP formulations for the treatment of breast cancer in vivo.

Ran GTPase, an eukaryotic gene novelty, is involved in amphioxus mitosis

Ran (ras-related nuclear protein) is a small GTPase belonging to the RAS superfamily that is specialized in nuclear trafficking. Through different accessory proteins, Ran plays key roles in several processes including nuclear import-export, mitotic progression and spindle assembly. Consequently, Ran dysfunction has been linked to several human pathologies. This work illustrates the high degree of amino acid conservation of Ran orthologues across evolution, reflected in its conserved role in nuclear trafficking. Moreover, we studied the evolutionary scenario of the pre-metazoan genetic linkage between Ran and Stx, and we hypothesized that chromosomal proximity of these two genes across metazoans could be related to a regulatory logic or a functional linkage. We studied, for the first time, Ran expression during amphioxus development and reported its presence in the neural vesicle, mouth, gill slits and gut corresponding to body regions involved in active cell division.

The Ski Protein is Involved in the Transformation Pathway of Aurora Kinase A

Oncogenic kinase Aurora A (AURKA) has been found to be overexpresed in several tumors including colorectal, breast, and hematological cancers. Overexpression of AURKA induces centrosome amplification and aneuploidy and it is related with cancer progression and poor prognosis. Here we show that AURKA phosphorylates in vitro the transcripcional co-repressor Ski on aminoacids Ser326 and Ser383. Phosphorylations on these aminoacids decreased Ski protein half-life. Reduced levels of Ski resulted in centrosomes amplification and multipolar spindles formation, same as AURKA overexpressing cells. Importantly, overexpression of Ski wild type, but not S326D and S383D mutants inhibited centrosome amplification and cellular transformation induced by AURKA. Altogether, these results suggest that the Ski protein is a target in the transformation pathway mediated by the AURKA oncogene.

Melanoma: oncogenic drivers and the immune system

Advances and in-depth understanding of the biology of melanoma over the past 30 years have contributed to a change in the consideration of melanoma as one of the most therapy-resistant malignancies. The finding that oncogenic BRAF mutations drive tumor growth in up to 50% of melanomas led to a molecular therapy revolution for unresectable and metastatic disease. Moving beyond BRAF, inactivation of immune regulatory checkpoints that limit T cell responses to melanoma has provided targets for cancer immunotherapy. In this review, we discuss the molecular biology of melanoma and we focus on the recent advances of molecularly targeted and immunotherapeutic approaches.

The overriding of TRAIL resistance by the histone deacetylase inhibitor MS-275 involves c-myc up-regulation in cutaneous, uveal, and mucosal melanoma

Malignant melanoma is a highly aggressive tumor which may occur in the skin, eye, and mucous membranes. The prognosis of melanoma remains poor in spite of therapeutic advances, emphasizing the importance of innovative treatment modalities. Currently, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is showing promising clinical responses, however its use is hampered by intrinsic or acquired melanoma resistance to apoptosis. Recently, we showed that the combination of TRAIL with the class I-specific histone deacetylase inhibitor (HDACi) MS-275 was a privileged way to override TRAIL resistance through down-regulation of cellular Fas-associated death domain (FADD)-like interleukin-1beta-converting enzyme-inhibitory protein (c-FLIP). Here, we elucidated the underlying mechanism and provided evidence that a crucial step in the c-FLIP downregulation triggered by MS-275 implies the up-regulation of c-myc, a transcriptional repressor of c-FLIP. Notably, MS-275 caused H3 histone acetylation at the promoter of c-myc and increased its binding to the c-FLIP promoter, that in turn led to reduced c-FLIP gene transcription. Knockdown of c-myc prevented the MS-275-mediated downregulation of c-FLIP and hindered TRAIL-plus MS-275-induced apoptosis. Findings reported here provide additional knowledge tools for a more aware and effective molecular therapy of melanoma.