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

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

Mn-based methacrylated gellan gum hydrogels for MRI-guided cell delivery and imaging

This work aims to engineer a new stable injectable Mn-based methacrylated gellan gum (Mn/GG-MA) hydrogel for real-time monitored cell delivery into the central nervous system. To enable the hydrogel visualization under Magnetic Resonance Imaging (MRI), GG-MA solutions were supplemented with paramagnetic Mn2+ ions before its ionic crosslink with artificial cerebrospinal fluid (aCSF). The resulting formulations were stable, detectable by T1-weighted MRI scans and also injectable. Cell-laden hydrogels were prepared using the Mn/GG-MA formulations, extruded into aCSF for crosslink, and after 7 days of culture, the encapsulated human adipose-derived stem cells remained viable, as assessed by Live/Dead assay. In vivo tests, using double mutant MBPshi/shi/rag2 immunocompromised mice, showed that the injection of Mn/GG-MA solutions resulted in a continuous and traceable hydrogel, visible on MRI scans. Summing up, the developed formulations are suitable for both non-invasive cell delivery techniques and image-guided neurointerventions, paving the way for new therapeutic procedures.Sílvia Vieira acknowledges the FCT Ph.D. scholarship (SFRH/BD/102710/2014). J. Miguel Oliveira and J. Silva-Correia acknowledge the FCT grants under the Investigator FCT program (IF/01285/2015 and IF/00115/2015, respectively). The authors also acknowledge the funds provided under the project NanoTech4ALS, funded under the EU FP7 M-ERA.NET program, and ESF (POWR.03.02.00-00-I028/17-00)

The prolactinergic system? Production and role of prolactin in the brain

Prolactin is a polypeptide hormone that undergoes many posttranslational modifications which modulate its biological functions. Functions of prolactin can be also modulated by different forms of the prolactin receptor. Although the main source of the hormone is the anterior pituitary gland, it is produced in many tissues, e.g. in the immune system and brain. Both the hormone and its mRNA were detected in many regions of the rat brain but prolactin-immunoreactive neuronal cell bodies were observed only in the hypothalamus. Prolactin receptors were also detected in many brain regions but, surprisingly, were not as widely distributed as prolactin. Brain regions differ in proportions of prolactin receptor forms. These observations may explain why prolactin play many functions in the brain (e.g. neuromodulation, regulation of neurotransmitter release). As prolactin and prolactin receptor knockout mice do not develop any serious defects in the brain functioning, it is hypothesized that prolactin regulation is subtle and also may be partially compensated by growth hormone and placental lactogen

Mechanizmy oporności na leczenie czerniaka inhibitorami BRAF i MEK

Dotychczas opisano kilka mechanizmów oporności na hamowanie aktywności BRAF w komórkach czerniaka. Badania genetyczne pozwoliły ustalić, że mutacje w kinazie MEK1 (kinaza kinazy MAP), które skutkują konstytutywną aktywacją kinazy ERK, powodują oporność na leczenie. Innym mechanizmem nabytej oporności na hamowanie BRAF jest gromadzenie mutacji aktywujących w onkogenie NRAS, który napędza aktywację CRAF. To z kolei prowadzi do trwałej aktywacji przeka­zywania sygnału do MEK i ERK. Innym ważnym mechanizmem oporności jest tworzenie wariantów składania genu BRAF V600E, w tym wariantów, w których brakuje eksonów od 4 do 8 zawierających domenę wiążącą RAS. Obecność wariantu p61 BRAF V600E prowadzi do konstytutywnej sygnalizacji ERK, która jest oporna na hamowanie RAF. Ponadto wpływ na oporność na leczenie mają hiperaktywacja receptorów kinaz tyrozynowych, takich jak receptor czynnika wzrostu płytek krwi β (PDFRβ), receptor podobnego do insuliny czynnika wzrostu 1 (IGF-1R) i wytwarzające erytropoetynę receptory wątrobowokomórkowe (EPH) – prowadzące do indukcji szlaku kinazy 3-fosfoinozytolowej (PI3K) u pacjentów leczonych inhibitorami BRAF lub MEK. Inną interesującą ścieżką oporności na BRAFi/MEKi jest nadekspresja receptora naskórkowego czynnika wzrostu (EGFR) poprzez ujemne sprzężenie zwrotne u pacjentów leczonych inhibitorami BRAF (BRAFi) – EGFR nie ulega normalnej ekspresji w nieleczonych czerniakach

Cutaneous and Subcutaneous Tumours of Small Pet Mammals—Retrospective Study of 256 Cases (2014–2021)

Since small mammals are gaining popularity as pets in Poland, the number of tumour samples submitted for histopathological examination is quite high. This study was a retrospective analysis of cutaneous and subcutaneous tumours in small pet mammals submitted for histopathology in 2014–2021. The analysis included 256 tumours sampled from 103 guinea pigs, 53 rats, 43 pet rabbits, 21 ferrets, 17 hamsters, 8 degus, 5 African pygmy hedgehogs, 3 Mongolian gerbils and 3 chinchillas. Tumours were diagnosed based on routine histopathology, with additional immunohistochemistry when necessary. The results of this study revealed that the vast majority of cutaneous tumours in guinea pigs were benign, with a predominance of lipoma. Adnexal tumours constituted a significant percentage of cutaneous tumours in guinea pigs (24.3%, with the most common being trichofolliculoma), pet rabbits (46.5%, with the most common being trichoblastoma), ferrets (33.3%, mostly derived from sebaceous glands), hamsters (52.9%, with the most common being trichoepithelioma) and gerbils (66.7%, scent gland epithelioma). Soft tissue sarcomas were a predominant group of tumours in rats (52.8%, with the most common being fibrosarcoma), African pygmy hedgehogs (100%), degus (87.5%) and chinchillas (66.7%). Melanocytic tumours were only sporadically seen in small mammal pets. Mast cell tumours were diagnosed only in ferrets, while epitheliotropic T-cell lymphoma was diagnosed only in a hamster and a degu. In summary, malignant tumours constitute a significant percentage of cutaneous tumours in many species of small mammal pets. Therefore, each cutaneous tumour should be sampled for further cytologic or histopathologic diagnosis

Cutaneous and Subcutaneous Tumours of Small Pet Mammals—Retrospective Study of 256 Cases (2014–2021)

Since small mammals are gaining popularity as pets in Poland, the number of tumour samples submitted for histopathological examination is quite high. This study was a retrospective analysis of cutaneous and subcutaneous tumours in small pet mammals submitted for histopathology in 2014–2021. The analysis included 256 tumours sampled from 103 guinea pigs, 53 rats, 43 pet rabbits, 21 ferrets, 17 hamsters, 8 degus, 5 African pygmy hedgehogs, 3 Mongolian gerbils and 3 chinchillas. Tumours were diagnosed based on routine histopathology, with additional immunohistochemistry when necessary. The results of this study revealed that the vast majority of cutaneous tumours in guinea pigs were benign, with a predominance of lipoma. Adnexal tumours constituted a significant percentage of cutaneous tumours in guinea pigs (24.3%, with the most common being trichofolliculoma), pet rabbits (46.5%, with the most common being trichoblastoma), ferrets (33.3%, mostly derived from sebaceous glands), hamsters (52.9%, with the most common being trichoepithelioma) and gerbils (66.7%, scent gland epithelioma). Soft tissue sarcomas were a predominant group of tumours in rats (52.8%, with the most common being fibrosarcoma), African pygmy hedgehogs (100%), degus (87.5%) and chinchillas (66.7%). Melanocytic tumours were only sporadically seen in small mammal pets. Mast cell tumours were diagnosed only in ferrets, while epitheliotropic T-cell lymphoma was diagnosed only in a hamster and a degu. In summary, malignant tumours constitute a significant percentage of cutaneous tumours in many species of small mammal pets. Therefore, each cutaneous tumour should be sampled for further cytologic or histopathologic diagnosis

TP53 in Biology and Treatment of Osteosarcoma

The TP53 gene is mutated in 50% of human tumors. Oncogenic functions of mutant TP53 maintain tumor cell proliferation and tumor growth also in osteosarcomas. We collected data on TP53 mutations in patients to indicate which are more common and describe their role in in vitro and animal models. We also describe animal models with TP53 dysfunction, which provide a good platform for testing the potential therapeutic approaches. Finally, we have indicated a whole range of pharmacological compounds that modulate the action of p53, stabilize its mutated versions or lead to its degradation, cause silencing or, on the contrary, induce the expression of its functional version in genetic therapy. Although many of the described therapies are at the preclinical testing stage, they offer hope for a change in the approach to osteosarcoma treatment based on TP53 targeting in the future