Parthenolide as Cooperating Agent for Anti-Cancer Treatment of Various Malignancies.

Primary and acquired resistance of cancer to therapy is often associated with activation of nuclear factor kappa B (NF-κB). Parthenolide (PN) has been shown to inhibit NF-κB signaling and other pro-survival signaling pathways, induce apoptosis and reduce a subpopulation of cancer stem-like cells in several cancers. Multimodal therapies that include PN or its derivatives seem to be promising approaches enhancing sensitivity of cancer cells to therapy and diminishing development of resistance.

Dissecting Mechanisms of Melanoma Resistance to BRAF and MEK Inhibitors Revealed Genetic and Non-Genetic Patient- and Drug-Specific Alterations and Remarkable Phenotypic Plasticity.

The clinical benefit of MAPK pathway inhibition in BRAF-mutant melanoma patients is limited by the development of acquired resistance. Using drug-naïve cell lines derived from tumor specimens, we established a preclinical model of melanoma resistance to vemurafenib or trametinib to provide insight into resistance mechanisms. Dissecting the mechanisms accompanying the development of resistance, we have shown that (i) most of genetic and non-genetic alterations are triggered in a cell line- and/or drug-specific manner; (ii) several changes previously assigned to the development of resistance are induced as the immediate response to the extent measurable at the bulk levels; (iii) reprogramming observed in cross-resistance experiments and growth factor-dependence restricted by the drug presence indicate that phenotypic plasticity of melanoma cells largely contributes to the sustained resistance.

Plasticity of Drug-Naïve and Vemurafenib- or Trametinib-Resistant Melanoma Cells in Execution of Differentiation/Pigmentation Program.

Melanoma plasticity creates a plethora of opportunities for cancer cells to escape treatment. Thus, therapies must target all cancer cell subpopulations bearing the potential to contribute to disease. The role of the differentiation/pigmentation program in intrinsic and acquired drug resistance is largely uncharacterized.

Melanoma-Derived Extracellular Vesicles Bear the Potential for the Induction of Antigen-Specific Tolerance.

Background: Cancer-induced immunosuppression is antigen-specific rather than systemic and the mechanisms for the antigen specificity are incompletely understood. Here we explore the option that tumor-associated antigens (TAAs) may be transferred to antigen-presenting cells (APCs), together with immunosuppressive molecules, through cancer-derived small extracellular vesicles (sEVs), such as exosomes. Stimulation of a suppressive phenotype in the very same APCs that take up TAAs may yield antigen-specific tolerance.

17-Aminogeldanamycin selectively diminishes IRE1α-XBP1s pathway activity and cooperatively induces apoptosis with MEK1/2 and BRAF inhibitors in melanoma cells of different genetic subtypes.

Outcomes of melanoma patient treatment remain unsatisfactory despite accessibility of oncoprotein-targeting drugs and immunotherapy. Here, we reported that 17-aminogeldanamycin more potently activated caspase-3/7 in BRAF melanoma cells than geldanamycin, another inhibitor of heat shock protein 90 (HSP90). 17-aminogeldanamycin alleviated self-triggered compensatory increase in HSP70 mRNA level and induced endoplasmic reticulum (ER) stress, which was followed by selective diminution of cytoprotective IRE1α-XBP1s pathway activity of unfolded protein response (UPR), inhibition of ERK1/2 activity and induction of apoptosis.

Whole-exome sequencing reveals novel genetic variants associated with diverse phenotypes of melanoma cells.

We have extensively studied the phenotypic heterogeneity of patient-derived melanoma cells. Here, whole-exome sequencing revealed novel variants of genes associated with the MAPK, NOTCH, Hippo, cell-cycle, senescence, and ubiquitin-dependent pathways, which could contribute to the observed phenotypic diversity between cell lines. Focusing on mutations in the MAPK pathway-associated genes, we found BRAF (BRAF ) and RAS subtypes, including NRAS and the rare HRAS variant, and additional alterations potentially leading to different ERK1/2 activity.

Exogenous growth factors bFGF, EGF and HGF do not influence viability and phenotype of V600EBRAF melanoma cells and their response to vemurafenib and trametinib in vitro.

It has been shown that the response of V600EBRAF melanoma cells to targeted therapeutics is affected by growth factors. We have investigated the influence of three different growth factors, bFGF, EGF and HGF used either alone or in combination, on the response of V600EBRAF melanoma cell populations established from surgical specimens to vemurafenib and trametinib, targeting V600EBRAF and MEK1/2, respectively. We report that proliferation and phenotype of V600EBRAF melanoma cell populations were not detectably influenced by exogenous growth factors.

Parthenolide induces MITF-M downregulation and senescence in patient-derived MITF-M(high) melanoma cell populations.

The activity of the M isoform of microphthalmia-associated transcription factor (MITF-M) has been attributed to regulation of differentiation, proliferation, survival and senescence of melanoma cells. MITF expression was shown to be antagonized by the activation of transcription factor NF-κB. Parthenolide, an inhibitor of NF-κB, has not been yet reported to affect MITF-M expression.

Diminution of miR-340-5p levels is responsible for increased expression of ABCB5 in melanoma cells under oxygen-deprived conditions.

Melanoma is usually highly refractory to chemotherapy. This resistance to treatment is mainly due to high heterogeneity and plasticity of melanoma cells strictly connected to changes in tumor microenvironment. Hypoxia can drastically alter cancer biology.

Expression of miRNAs as Important Element of Melanoma Cell Plasticity in Response to Microenvironmental Stimuli.

Background: Melanoma cells form monolayers in serum-containing media, however, in serum-free media they form anchorage-independent spheroids. We investigated miRNAs differentially expressed between these culture types and identified those that possibly control the plasticity of melanoma cells.

Materials And Methods: The expression of miRNAs in melanoma cells was evaluated with microarrays, and certain miRNAs were validated with real-time PCR.

Phenotypic diversity of patient-derived melanoma populations in stem cell medium.

Melanomas are highly heterogeneous tumors and there is no treatment effective at achieving long-term remission for metastatic melanoma patients. Thus, an appropriate model system for studying melanoma biology and response to drugs is necessary. It has been shown that composition of the medium is a critical factor in preserving the complexity of the tumor in in vitro settings, and melanospheres maintained in stem cell medium are a good model in this respect.

Natural compounds' activity against cancer stem-like or fast-cycling melanoma cells.

Background: Accumulating evidence supports the concept that melanoma is highly heterogeneous and sustained by a small subpopulation of melanoma stem-like cells. Those cells are considered as responsible for tumor resistance to therapies. Moreover, melanoma cells are characterized by their high phenotypic plasticity.

Parthenolide enhances dacarbazine activity against melanoma cells.

Dacarbazine induces a clinical response only in 15% of melanoma patients. New treatment strategies may involve combinations of drugs with different modes of action to target the tumor heterogeneity. We aimed to determine whether the combined treatment of heterogeneous melanoma cell populations in vitro with the alkylating agent dacarbazine and the nuclear factor-κB inhibitor parthenolide could be more effective than either drug alone.

Parthenolide reduces the frequency of ABCB5-positive cells and clonogenic capacity of melanoma cells from anchorage independent melanospheres.

Growing evidence suggests that the cancer stem cell phenotype in melanoma is dynamically regulated. Therefore, effective therapies have to target simultaneously bulk tumor cells and melanoma stem-like cells. The aim of the present study was to investigate the effects of parthenolide on heterogeneous cancer cell populations from anchorage-independent melanospheres.

Sphere formation and self-renewal capacity of melanoma cells is affected by the microenvironment.

Melanomas contain subsets of cancer stem-like cells with tumor-initiating capacity. The frequency of these cells in the tumor is still a topic of debate. We investigated the phenotypic plasticity of cancer cells grown as melanospheres to elucidate the influence of the microenvironment on some features of melanoma stem-like cells.

Promoter spacer DNA plays an active role in integrating the functional consequences of RNA polymerase contacts with -10 and -35 promoter elements.

Bacterial RNA polymerase (RNAP) interacts with conserved -10 and -35 promoter elements to recognize the promoter and to form an open complex in which DNA duplex around transcription start site melts. Using model DNA constructs (fork junction DNA) that mimic DNA structure found in the open complex we observed that the consequences of mutations in -10 promoter element for RNAP binding exhibited a striking dependence on the presence or absence of a functional -35 promoter element. A role of spacer DNA (a non-conserved DNA sequence connecting -10 and -35 promoter elements) in this phenomenon was probed with a series of fork junction DNA constructs containing perturbations to the spacer DNA.

Tautomerization of 2-nitroso-N-arylanilines by coordination as N,N'-chelate ligands to rhenium(I) complexes and the anticancer activity of newly synthesized oximine rhenium(I) complexes against human melanoma and leukemia cells in vitro.

The synthesis, structural characterization and biological activity of eight ortho-quinone(N-aryl)-oximine rhenium(I) complexes are described. The reaction of the halogenido complexes (CO)(5)ReX (X = Cl (4), Br (5)) with 2-nitroso-N-arylanilines {(C(6)H(3)ClNO)NH(C(6)H(4)R)} (R = p-Cl, p-Me, o-Cl, H) (3a-d) in tetrahydrofurane (THF) yields the complexes fac-(CO)(3)XRe{(C(6)H(3)ClNO)NH(C(6)H(4)R)} (6a-d, 7a-d) with the tautomerized ligand acting as a N,N'-chelate. The substitution of two carbonyl ligands leads to the formation of a nearly planar 5-membered metallacycle.

A non-apoptotic function of caspase-3 in pharmacologically-induced differentiation of K562 cells.

Background And Purpose: Several anticancer drugs with diverse chemical structures can induce differentiation of cancer cells. This study was undertaken to explore the potential contribution of caspase-3 to pharmacologically-induced differentiation of K562 cells.

Experimental Approach: We assessed differentiation by measuring the expression of glycophorin A and haemoglobin synthesis in K562 cells treated with low concentrations of doxorubicin, hydroxyurea, cytosine arabinoside, cisplatin and haemin.

STI571/doxorubicin concentration-dependent switch for diverse caspase actions in CML cell line K562.

Unlabelled: We examined the response of the apoptosis-reluctant CML cell line K562 to doxorubicin alone or in combination with the tyrosine kinase inhibitor STI571. We found that at clinically relevant concentrations, doxorubicin induced differentiation and senescence, but did not induce apoptosis. Doxorubicin induced G(2)/M arrest and mitochondrial transmembrane potential dissipation.

[Transcription factors in the development and progression of melanoma].

Melanoma (melanoma malignum) is a malignant tumor derived from melanin-producing melanocytes. Both environmental factors and genetic predisposition are important in tumor development and progression. If not detected and removed early, it is very aggressive and unresponsive to current therapeutic approaches.