Mechanisms of melanoma resistance to treatment with BRAF and MEK inhibitors

Several mechanisms of resistance to inhibition of BRAF activity in melanoma cells have been described so far. Genetic studies have shown that mutations in MEK1 kinase (MAP kinase kinase), which result in constitutive activation of ERK kinase, result in resistance to treatment. Another mechanism of the acquired BRAF inhibition resistance is the accumulation of activating mutations in the NRAS oncogene, which drives the activation of CRAF. This in turn leads to a permanent activation of the signal transduction to MEK and ERK. Another important mechanism of resistance is the formation of variants of the BRAF V600E gene splicing, including variants that lack exons 4 to 8 containing the RAS-binding domain. The presence of the p61 BRAF V600E variant leads to the constitutive ERK signal, which is resistant to RAF inhibition. In addition, treatment resistance is affected by hyperactivation of tyrosine kinase receptors such as platelet-derived factor receptor β (PDFRβ), insulin-like growth factor 1 receptor (IGF-1R) and erythropoietin-producing hepatocellular receptors (EPH) – leading to the induction of the 3-phosphoinositol kinase pathway (PI3K) in patients treated with BRAF or MEK inhibitors. Another interesting path of BRAFi/MEKi resistance is over-expression of the epidermal growth factor receptor (EGFR) through ne­gative feedback in patients treated with BRAF inhibitors (BRAFi) – EGFR is not normally expressed in untreated melanomas

Propolis changes the anticancer activity of temozolomide in U87MG human glioblastoma cell line

BACKGROUND: Propolis is a honey bee product which contains many active compounds, such as CAPE or chrysin, and has many beneficial activities. Recently, its anti-tumor properties have been discussed. We have tested whether the ethanolic extract of propolis (EEP) interferes with temozolomide (TMZ) to inhibit U87MG cell line growth. METHODS: The U87MG glioblastoma cell line was exposed to TMZ (10-100 μM), EEP (10-100 μg/ml) or a mixture of TMZ and EEP during 24, 48 or 72 hours. The cell division was examined by the H(3)-thymidine incorporation, while the western blot method was used for detection of p65 subunit of NF-κB and ELISA test to measure the concentration of its p50 subunit in the nucleus. RESULTS: We have found that both, TMZ and EEP administrated alone, had a dose- and time-dependent inhibitory effect on the U87MG cell line growth, which was manifested by gradual reduction of cell viability and alterations in proliferation rate. The anti-tumor effect of TMZ (20 μM) was enhanced by EEP, which was especially well observed after a short time of exposition, where simultaneous usage of TMZ and EEP resulted in a higher degree of growth inhibition than each biological factor used separately. In addition, cells treated with TMZ presented no changes in NF-κB activity in prolonged time of treatment and EEP only slightly reduced the nuclear translocation of this transcription factor. In turn, the combined incubation with TMZ and EEP led to an approximately double reduction of NF-κB nuclear localization. CONCLUSIONS: We conclude that EEP presents cytotoxic properties and may cooperate with TMZ synergistically enhancing its growth inhibiting activity against glioblastoma U87MG cell line. This phenomenon may be at least partially mediated by a reduced activity of NF-κB

Ceramides and sphingosine-1-phosphate as potential markers in diagnosis of ischaemic stroke

Background. Brain imaging in stroke diagnostics is a powerful tool, but one that can fail in more challenging cases, and one that is not particularly useful in identifying transient ischaemic attacks (TIAs). Thus, new reliable blood biomarkers of cerebral ischaemia are constantly sought. Objective. We studied the potential usefulness of sphingolipids (SFs) as biomarkers of acute ischaemic stroke and TIA. Material and methods. Levels of individual ceramide species and sphingosine-1-phosphate (Sph-1-P) in blood serum of patients with acute ischaemic stroke, TIA, and age-matched neurological patients without cerebral ischaemia, were assessed by tandem mass spectrometry liquid chromatography (LC- MS / MS). Results. We found significant increases of several sphingolipid levels, with particularly strong elevations of Cer-C20:0 in patients with acute stroke. Cer-C24:1 was the only ceramide species to decrease as a result of acute stroke. Moreover, its levels inversely correlated with the number of days after stroke onset, suggesting that Cer-C24:1 is an independent parameter related to the course of stroke. To increase the sensitivity of sphingolipid-based tests in stroke diagnostics, we calculated the values of ratios of Sph-1-P / individual ceramide species and Cer-C24:1 individual ceramide species. We found several ratios significantly changed in stroke patients. Two ratios, Sph-1-P / Cer-C24:1 and Cer-C24:0 / Cer-C24:1, presented especially strong increments in patients with acute stroke. Moreover, Sph-1-P / Cer-C24:1 values were augmented in TIA patients. Conclusion. Serum SFs could be good candidates to be ischaemic stroke biomarkers. We have identified two SF ratios, Sph-1-P / Cer-C24:1 and Cer-C24:0 / Cer-C24:1, with strong diagnostic potential in ischaemic stroke. We found Sph-1-P / Cer-C24:1 ratio to be possibly useful in TIA diagnostics, also in the long term after ischaemic incidence

Acyclic colourings of graphs with bounded degree

Graphs and Algorithm

Biologia molekularna mięsaków

Mięsaki tkanek miękkich to duża grupa nowotworów heterogennych, często o dużej agresywności. W zdecydowanej większości przypadków występują sporadycznie, bez wyraźnie zdefiniowanego czynnika leżącego u podstaw nowotworzenia. Ewentualnymi czynnikami ryzyka są: narażenie na promieniowanie jonizujące, obrzęk limfatyczny (naczyniakomięsak piersi), infekcje wirusowe (HHV8 — mięsak Kaposiego), narażenie na czynniki chemiczne (chlorek winylu — naczyniakomięsak wątroby). Podatność genetyczna odgrywa rolę w niewielkiej części przypadków, mutacje genów TP53, ATM oraz ATR są związane ze zwiększoną wrażliwością na promieniowanie jonizujące i wtórnie — rozwój mięsaków. Zespół Li-Fraumeni (autosomalna dominująca mutacja w genie TP53) predysponuje do rozwoju guzów złośliwych, z których jedną trzecią stanowią mięsaki. Zmiany genetyczne obserwowane w mięsakach można podzielić na trzy grupy: (1) translokacje chromosomalne; (2) mutacje punktowe bez zmiany kariotypu; (3) występowanie zmiennego i złożonego kariotypu. Do chorób cechujących się uszkodzeniem genomu pierwszego typu należy znaczna część mięsaków. Występowanie specyficznych translokacji (np. SSX1-SYT czy EWS-FLI1) jest standardowo wykorzystywane w celach diagnostycznych. Mniejszą liczbę przypadków można zaliczyć do chorób o zaburzeniach genomu drugiego typu, do których należą m.in. guz desmoidalny (mutacje genów CTNNB1 lub APC) czy GIST (mutacje KIT lub PDGFRA, znacznie rzadziej BRAF, SDH, NF1). Duża część mięsaków zalicza się do grupy trzeciej — charakteryzującej się złożonym i zmiennym kariotypem. Zwiększeniu może ulegać liczba kopii genów, np. w zróżnicowanym tłuszczakomięsaku obserwuje się amplifikację genów MDM2, CDK4 i HMGA2; może także dochodzić do typowych uszkodzeń chromosomalnych jak w genie CHOP w myksoidnym tłuszczakomięsaku i FKHR w pęcherzykowym mięsaku prążkowanokomórkowym

Molecular biology of sarcoma

Soft tissue sarcomas are a large group of heterogenous neoplasms, many of them are highly aggressive. Most of the cases are sporadic, without any well-defined pathogenetic factor. Potential risk factors are ionizing radiation, lymphatic oedema (secondary angiosarcoma of the breast), viral infections (HHV8 and Kaposi sarcoma), exposure to chemical factors (vinyl chloride and hepatic angiosarcoma). Genetic susceptibility plays a role in a minority of cases. However, mutations in TP53, ATM and ATR genes are associated with enhanced susceptibility to radiation. Li-Fraumeni syndrome (autosomal dominant TP53 mutation) predisposes to development of malignancies, one third of them are sarcomas. Genetic alterations observed in sarcomas could be divided into three major groups characterized by: (1) chromosome translocations; (2) simple karyotype and mutations; (3) variably complex karyotypes. A large part of sarcomas belong to the first group and the specific chromosal translocations could be utilized in the diagnostic process. A smaller number of sarcomas could be assigned to the second group, e.g. desmoid fibromatosis (CTNNB1 or APC mutations) and GIST (KIT, PDGFRA, or less frequently BRAF, SDH, NF1). A large number of sarcomas are characterized by complex and variable karyotypes. Gene copy number alterations are frequent in this group, e.g. in well-differentiated liposarcoma there is an amplification of MDM2, CDK4 and HMGA2 genes or sarcoma-specific chromosomal break regions present in the CHOP gene in myxoid liposarcoma and FKHR in alveolar rhabdomyosarcoma