MEK1/2 regulate normal BCR and ABL1 tumor-suppressor functions to dictate ATO response in TKI-resistant Ph+ leukemia.

Resistance to tyrosine kinase inhibitors (TKIs) remains a clinical challenge in Ph-positive variants of chronic myeloid leukemia. We provide mechanistic insights into a previously undisclosed MEK1/2/BCR::ABL1/BCR/ABL1-driven signaling loop that may determine the efficacy of arsenic trioxide (ATO) in TKI-resistant leukemic patients. We find that activated MEK1/2 assemble into a pentameric complex with BCR::ABL1, BCR and ABL1 to induce phosphorylation of BCR and BCR::ABL1 at Tyr360 and Tyr177, and ABL1, at Thr735 and Tyr412 residues thus provoking loss of BCR's tumor-suppression functions, enhanced oncogenic activity of BCR::ABL1, cytoplasmic retention of ABL1 and consequently drug resistance. Coherently, pharmacological blockade of MEK1/2 induces dissociation of the pentameric MEK1/2/BCR::ABL1/BCR/ABL1 complex and causes a concurrent BCRY360/Y177, BCR::ABL1Y360/Y177 and cytoplasmic ABL1Y412/T735 dephosphorylation thereby provoking the rescue of the BCR's anti-oncogenic activities, nuclear accumulation of ABL1 with tumor-suppressive functions and consequently, growth inhibition of the leukemic cells and an ATO sensitization via BCR-MYC and ABL1-p73 signaling axes activation. Additionally, the allosteric activation of nuclear ABL1 was consistently found to enhance the anti-leukemic effects of the MEK1/2 inhibitor Mirdametinib, which when combined with ATO, significantly prolonged the survival of mice bearing BCR::ABL1-T315I-induced leukemia. These findings highlight the therapeutic potential of MEK1/2-inhibitors/ATO combination for the treatment of TKI-resistant leukemia.

Clinical, genetic, and pathological features of male pseudohermaphroditism in dog.

Male pseudohermaphroditism is a sex differentiation disorder in which the gonads are testes and the genital ducts are incompletely masculinized. An 8 years old dog with normal male karyotype was referred for examination of external genitalia abnormalities. Adjacent to the vulva subcutaneous undescended testes were observed. The histology of the gonads revealed a Leydig and Sertoli cell neoplasia. The contemporaneous presence of testicular tissue, vulva, male karyotype were compatible with a male pseudohermaphrodite (MPH) condition.

Isolation and characterization of a strain of Lichtheimia corymbifera (ex Absidia corymbifera) from a case of bovine abortion.

BACKGROUND: Lichtheimia corymbifera (previously Absidia corymbifera) is a filamentous zygomycetes belonging to the order Mucorales and to the family Lichtheimiaceae. Members of genus Lichtheimia spp. are cosmopolitan and ubiquitous in nature. Lichtheimia corymbifera is a recognized agent of diseases in man and animals. In cattle it causes abortion and mastitis. Three cases of bovine abortion occurred in a herd located in the Po Valley. Serological examinations were performed on fetal and mother's blood. One of the aborted fetus was referred to our laboratory. The paper describes the isolation and characterization of Lichtheimia corymbifera from a bovine aborted fetus. METHODS: Serological examinations were performed on fetal and mother's blood. Lesions on fetal tissues and placenta leaded the diagnostic suspect towards a mycotic aetiology. Tissues were then put in culture, and at the same time an histological examination was performed, together with bacteriological and virological tests. The isolate from placenta and fetal tissues was identified and characterized by PCR and RFLP, using the ITS region as a target sequence and AclI restriction site within the amplicon to distinguish Lichtheimia corymbifera among the other fungi. RESULTS: Serological, bacteriological and virological tests gave aspecific results. Histological examination evidenced numerous PAS positive hyphae within the necrotic cotiledons and numerous fungal nonseptate hyphae to the GMS stain. Colonies with typical morphological features of fungi grew up on Sabouraud agar from fetal skin and placenta. On the developed colonies the microscopic examination has shown a large number of nonseptate hyphae and sporangia consistent with Mucorales. PCR and RFLP allowed the identification of the isolate as Lichtheimia corymbifera. CONCLUSION: The present report describes the isolation and the molecular characterisation of a fungal isolate from bovine aborted fetus and placenta. The diagnostic protocol allowed to identify and characterise the strain. This is the first isolation in Italy of Lichtheimia corymbifera in a bovine aborted fetus.

Immunohistological demonstration of Rhodococcus equi in a trotter foal.

A 3-month-old female trotter foal was euthanized due to severe dyspnoea. Pathomorphologically a chronic granulomatous to necrotizing pneumonia was found and Rhodoccocus (R.) equi was isolated microbiologically. An immunohistological method using a murine monoclonal antibody against a 15-17 kDa antigen of virulent R. equi was established in formalin-fixed and paraffin-embedded tissue sections using various antigen retrieval techniques to optimize the staining results. Microwave treatment was most suitable for the demonstration of bacterial antigen localized predominantly in intralesional macrophages. Immunohistology is an additional method for identifying R. equi-infections in equine tissue and may be useful in retrospective studies on paraffin-embedded archive material.

Axonopathy in the Central Nervous System Is the Hallmark of Mice with a Novel Intragenic Null Mutation of Dystonin.

Dystonia musculorum is a neurodegenerative disorder caused by a mutation in the dystonin gene. It has been described in mice and humans where it is called hereditary sensory autonomic neuropathy. Mutated mice show severe movement disorders and die at the age of 3-4 weeks. This study describes the discovery and molecular, clinical, as well as pathological characterization of a new spontaneously occurring mutation in the dystonin gene in C57BL/6N mice. The mutation represents a 40-kb intragenic deletion allele of the dystonin gene on chromosome 1 with exactly defined deletion borders. It was demonstrated by Western blot, mass spectrometry, and immunohistology that mice with a homozygous mutation were entirely devoid of the dystonin protein. Pathomorphological lesions were restricted to the brain stem and spinal cord and consisted of swollen, argyrophilic axons and dilated myelin sheaths in the white matter and, less frequently, total chromatolysis of neurons in the gray matter. Axonal damage was detected by amyloid precursor protein and nonphosphorylated neurofilament immunohistology. Axonopathy in the central nervous system (CNS) represents the hallmark of this disease. Mice with the dystonin mutation also showed suppurative inflammation in the respiratory tract, presumably due to brain stem lesion-associated food aspiration, whereas skeletal muscles showed no pathomorphological changes. This study describes a novel mutation in the dystonin gene in mice leading to axonopathy in the CNS. In further studies, this model may provide new insights into the pathogenesis of neurodegenerative diseases and may elucidate the complex interactions of dystonin with various other cellular proteins especially in the CNS.