New tricks from an old oncogene: gene fusion and copy number alterations of MYB in human cancer

(Sialyl)Lewis Antigen Expression on Glycosphingolipids, N-, and O-Glycans in Colorectal Cancer Cell Lines is Linked to a Colon-Like Differentiation Program

Alterations in the glycomic profile are a hallmark of cancer, including colorectal cancer (CRC). While, the glycosylation of glycoproteins and glycolipids has been widely studied for CRC cell lines and tissues, a comprehensive overview of CRC glycomics is still lacking due to the usage of different samples and analytical methods. In this study, we compared glycosylation features of N-, O-glycans, and glycosphingolipid glycans for a set of 22 CRC cell lines, all measured by porous graphitized carbon nano-liquid chromatography-tandem mass spectrometry. An overall, high abundance of (sialyl)Lewis antigens for colon-like cell lines was found, while undifferentiated cell lines showed high expression of H blood group antigens and α2-3/6 sialylation. Moreover, significant associations of glycosylation features were found between the three classes of glycans, such as (sialyl)Lewis and H blood group antigens. Integration of the datasets with transcriptomics data revealed positive correlations between (sialyl)Lewis antigens, the corresponding glycosyltransferase FUT3 and transcription factors CDX1, ETS, HNF1/4A, MECOM, and MYB. This indicates a possible role of these transcription factors in the upregulation of (sialyl)Lewis antigens, particularly on glycosphingolipid glycans, via FUT3/4 expression in colon-like cell lines. In conclusion, our study provides insights into the possible regulation of glycans in CRC and can serve as a guide for the development of diagnostic and therapeutic biomarkers.

From modulation of cellular plasticity to potentiation of therapeutic resistance: new and emerging roles of MYB transcription factors in human malignancies

MYB transcription factors are encoded by a large family of highly conserved genes from plants to vertebrates. There are three members of the MYB gene family in human, namely, MYB, MYBL1, and MYBL2 that encode MYB/c-MYB, MYBL1/A-MYB, and MYBL2/B-MYB, respectively. MYB was the first member to be identified as a cellular homolog of the v-myb oncogene carried by the avian myeloblastosis virus (AMV) causing leukemia in chickens. Under the normal scenario, MYB is predominantly expressed in hematopoietic tissues, colonic crypts, and neural stem cells and plays a role in maintaining the undifferentiated state of the cells. Over the years, aberrant expression of MYB genes has been reported in several malignancies and recent years have witnessed tremendous progress in understanding of their roles in processes associated with cancer development. Here, we review various MYB alterations reported in cancer along with the roles of MYB family proteins in tumor cell plasticity, therapy resistance, and other hallmarks of cancer. We also discuss studies that provide mechanistic insights into the oncogenic functions of MYB transcription factors to identify potential therapeutic vulnerabilities.

Src-Family Protein Kinase Inhibitors Suppress MYB Activity in a p300-Dependent Manner

Recent studies have disclosed transcription factor MYB as a potential drug target for malignancies that are dependent on deregulated MYB function, including acute myeloid leukemia (AML) and adenoid cystic carcinoma (ACC). Although transcription factors are often regarded as undruggable, successful targeting of MYB by low-molecular-weight compounds has recently been demonstrated. In an attempt to repurpose known drugs as novel MYB-inhibitory agents, we have screened libraries of approved drugs and drug-like compounds for molecules with MYB-inhibitory potential. Here, we present initial evidence for the MYB-inhibitory activity of the protein kinase inhibitors bosutinib, PD180970 and PD161570, that we identified in a recent screen. We show that these compounds interfere with the activity of the MYB transactivation domain, apparently by disturbing the ability of MYB to cooperate with the coactivator p300. We show that treatment of the AML cell line HL60 with these compounds triggers the up-regulation of the myeloid differentiation marker CD11b and induces cell death. Importantly, we show that these effects are significantly dampened by forced expression of an activated version of MYB, confirming that the ability to suppress MYB function is a relevant activity of these compounds. Overall, our work identifies several protein kinase inhibitors as novel MYB-inhibitory agents and suggests that the inhibition of MYB function may play a role in their pharmacological impact on leukemic cells.

Characterization of the MYB-inhibitory potential of the Pan-HDAC inhibitor LAQ824

A large body of work has shown that MYB acts as a master transcription regulator in hematopoietic cells and has pinpointed MYB as a potential drug target for acute myeloid leukemia (AML). Here, we have examined the MYB-inhibitory potential of the HDAC inhibitor LAQ824, which was identified in a screen for novel MYB inhibitors. We show that nanomolar concentrations of LAQ824 and the related HDAC inhibitors vorinostat and panobinostat interfere with MYB function in two ways, by inducing its degradation and inhibiting its activity. Reporter assays show that the inhibition of MYB activity by LAQ824 involves the MYB transactivation domain and the cooperation of MYB with co-activator p300, a key MYB interaction partner and driver of MYB activity. In AML cells, LAQ824-induced degradation of MYB is accompanied by expression of myeloid differentiation markers and apoptotic and necrotic cell death. The ability of LAQ824 to inhibit MYB activity is supported by the observation that down-regulation of direct MYB target genes MYC and GFI1 occurs without apparent decrease of MYB expression already after 2 h of treatment with LAQ824. Furthermore, ectopic expression of an activated version of MYB In HL60 cells counteracts the induction of myeloid differentiation by LAQ824. Overall, our data identify LAQ824 and related HDAC inhibitors as potent MYB-inhibitory agents that exert dual effects on MYB expression and activity in AML cells.

Association between rs3088440 (G > A) polymorphism at 9p21.3 locus with the occurrence and severity of coronary artery disease in an Iranian population

BACKGROUND

Several genome-wide association studies showed that a series of genetic variants located at the chromosome 9p21 locus are strongly associated with coronary artery disease (CAD).

RATIONALE AND PURPOSE OF THE STUDY

In the present study, the relationship of rs3088440 (G > A) in cyclin-dependent kinase inhibitor 2A (CDKN2A) gene site with the presence of coronary artery disease (CAD) and its severity was evaluated in an Iranian population.

METHODS AND RESULTS

The presence of rs3088440 (G > A) genotypes was assessed by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) technique in 324 CAD patients and 148 normal controls. rs3088440 (G > A) polymorphism was associated with increased risk of CAD in the total population (adjusted OR = 1.76, 95% CI = 1.10-2.82; p-value = 0.017) or in women (adjusted OR = 2.96, 95% CI = 1.34-6.55; p-value = 0.007), but not in the men (adjusted OR = 1.35, 95% CI = 0.70-2.6; p-value = 0.368).

CONCLUSIONS

Our findings suggest that the presence of rs3088440 (G > A) is potentially linked with the risk of CAD and its severity in whole study subjects or in women only, independent of CAD risk factors.

Proteasome inhibitors suppress MYB oncogenic activity in a p300-dependent manner

Studies of the role of MYB in human malignancies have highlighted MYB as a potential drug target for acute myeloid leukemia (AML) and adenoid cystic carcinoma (ACC). Although transcription factors are often considered un-druggable, recent work has demonstrated successful targeting of MYB by low molecular weight compounds. This has fueled the notion that inhibition of MYB has potential as a therapeutic approach against MYB-driven malignancies. Here, we have used a MYB reporter cell line to screen a library of FDA-approved drugs for novel MYB inhibitors. We demonstrate that proteasome inhibitors have significant MYB-inhibitory activity, prompting us to characterize the proteasome inhibitor oprozomib in more detail. Oprozomib was shown to interfere with the ability of the co-activator p300 to stimulate MYB activity and to exert anti-proliferative effects on human AML and ACC cells. Overall, our work demonstrated suppression of oncogenic MYB activity as a novel result of proteasome inhibition.

lncRNA LOC102724169 plus cisplatin exhibit the synergistic anti-tumor effect in ovarian cancer with chronic stress

Chronic stress has been proven to accelerate the development and progression of ovarian cancer, but the underlying molecular mechanisms have not been fully elucidated. In a combination survey of ovarian cancer with chronic stress (OCCS) mouse models and high-throughput sequencing, a key lncRNA named LOC102724169 on chromosome 6q27 has been identified, which functions as a dominant tumor suppressor in OCCS. Transcriptionally regulated by CCAAT enhancer binding protein (CEBP) beta (CEBPB), LOC102724169 shows low expression and correlates with poor progression-free survival (PFS) in OCCS patients. LOC102724169 is an instructive molecular inhibitor of malignancy of ovarian cancer cells, which is necessary to improve the curative effect of cisplatin therapy on ovarian cancer. This function stems from the inactivation of molecules in phosphatidylinositol 3-kinase (PI3K)/AKT signaling, repressing MYB expression and retaining the responsiveness of cancer cells to cisplatin. These findings provide a mechanistic understanding of the synergistic anti-tumor purpose of LOC102724169 as a bona fide tumor suppressor, enhancing the therapeutic effect of cisplatin. The new regulatory model of “lncRNA-MYB” provides new perspectives for LOC102724169 as a chronic stress-related molecule and also provides mechanistic insight into exploring the cancer-promoting mechanism of MYB in OCCS, which may be a promising therapeutic strategy for ovarian cancer.

Association of SNPs in CDKN2A (P14ARF) Tumour Suppressor Gene With Endometrial Cancer in Postmenopausal Women

BACKGROUND/AIM

This research was aimed to evaluate the association between three selected single nucleotide polymorphisms (SNPs) within the CDKN2A (P14ARF) tumour suppressor gene and the incidence of endometrial cancer (EC) in postmenopausal women.

PATIENTS AND METHODS

The study included 194 postmenopausal women; 144 with EC and 50 non-cancer controls. Genotypes in P14ARF rs3088440, rs3731217 and rs3731245 polymorphisms were assayed using PCR-RFLP and confirmed by sequencing.

RESULTS

Regarding the rs3088440 polymorphism, CT, and CT-TT genotypes, were more prevalent among EC patients than in controls (OR=5.55, p=0.023, OR=5.29, p=0.027; and OR=2.92, p=0.023, respectively). The T allele within rs3088440 was more prevalent in EC females than in controls (χ²=4.7, p=0.030). Considering rs3731217, TG and TG-GG genotypes were less prevalent among EC (OR=0.34, p=0.024 or p=0.023; and OR=0.38, p=0.035, respectively).

CONCLUSION

Polymorphisms in the CDKN2A gene are associated with EC in postmenopausal women.

Expanding the Molecular Spectrum of Secretory Carcinoma of Salivary Glands With a Novel VIM-RET Fusion

BACKGROUND

Secretory carcinoma (SC), originally described as mammary analogue SC, is a predominantly low-grade salivary gland neoplasm characterized by a recurrent t(12;15)(p13;q25) translocation, resulting in ETV6-NTRK3 gene fusion. Recently, alternative ETV6-RET, ETV6-MAML3, and ETV6-MET fusions have been found in a subset of SCs lacking the classic ETV6-NTRK3 fusion transcript, but still harboring ETV6 gene rearrangements.

DESIGN

Forty-nine cases of SC revealing typical histomorphology and immunoprofile were analyzed by next-generation sequencing using the FusionPlex Solid Tumor kit (ArcherDX). All 49 cases of SC were also tested for ETV6, RET, and NTRK3 break by fluorescence in situ hybridization and for the common ETV6-NTRK3 fusions using reverse transcription polymerase chain reaction.

RESULTS

Of the 49 cases studied, 37 (76%) occurred in the parotid gland, 7 (14%) in the submandibular gland, 2 (4%) in the minor salivary glands, and 1 (2%) each in the nasal mucosa, facial skin, and thyroid gland. SCs were diagnosed more frequently in males (27/49 cases; 55%). Patients' age at diagnosis varied from 15 to 80 years, with a mean age of 49.9 years. By molecular analysis, 40 cases (82%) presented the classic ETV6-NTRK3 fusion, whereas 9 cases (18%) revealed an alternate fusion. Of the 9 cases negative for the ETV6-NTRK3 fusion, 8 cases presented with ETV6-RET fusion. In the 1 remaining case in the parotid gland, next-generation sequencing analysis identified a novel VIM-RET fusion transcript. In addition, the analysis indicated that 1 recurrent high-grade case in the submandibular gland was positive for both ETV6-NTRK3 and MYB-SMR3B fusion transcripts.

CONCLUSIONS

A novel finding in our study was the discovery of a VIM-RET fusion in 1 patient with SC of the parotid gland who could possibly benefit from RET-targeted therapy. In addition, 1 recurrent high-grade case was shown to harbor 2 different fusions, namely, ETV6-NTRK3 and MYB-SMR3B. The expanded molecular spectrum provides a novel insight into SC oncogenesis and carries important implications for molecular diagnostics, as this is the first SC-associated translocation with a non-ETV6 5' fusion partner. This finding further expands the definition of SC while carrying implications for selecting the appropriate targeted therapy.

v-myb avian myeloblastosis viral oncogene homolog expression is a potential molecular diagnostic marker for B-cell acute lymphoblastic leukemia

BACKGROUND

B-cell acute lymphoblastic leukemia (B-ALL) is the most commonly diagnosed childhood malignancy worldwide and is especially common in Mexico. Additionally, the number of cases has increased in recent years. Thus, it is very important to develop molecular strategies to diagnose leukemia. The aim of this study was to investigate MYB expression and to determine its impact on the diagnosis of B-ALL.

METHODS

We analyzed the B-ALL gene expression profile by microarray data mining. Bioinformatics analysis was performed to identify the genes that are overexpressed in leukemia. We determined that MYB was highly expressed in leukemia. Then, we validated MYB expression in 70 patients with B-ALL and in 16 healthy controls (HCs) using qRT-PCR. The results were statistically analyzed using the Kolmogorov-Smirnov Z test, Mann-Whitney U test, receiver operating characteristic curves, and the Youden index.

RESULTS

The microarrays showed that MYB was overexpressed in B-ALL patients with a fold change of 57.8728 and a P value of 2.56^-195 . MYB expression showed great variability among the patients analyzed. However, compared to the HCs, the B-ALL patients had a P value < .0001, an area under the curve of 0.813, and a Youden index of 1.46, indicating the statistical significance.

CONCLUSION

MYB expression in B-ALL cells could be a potential molecular marker for childhood leukemia.

Pleomorphic adenomas and mucoepidermoid carcinomas of the breast are underpinned by fusion genes

Primary pleomorphic adenomas (PAs) and mucoepidermoid carcinomas (MECs) of the breast are vanishingly rare. Here we sought to determine whether breast PAs and MECs would be underpinned by the fusion genes reported to occur in their salivary gland counterparts. Our study included three breast PAs and one breast MEC, which were subjected to RNA sequencing (PAs, n = 2; MEC, n = 1) or to Archer FusionPlex sequencing (PA, n = 1). Our analyses revealed the presence of the HMGA2-WIF1 fusion gene in breast PA3, the CTNNB1-PLAG1 fusion gene in breast PA2, and the CRTC1-MAML2 fusion gene in the breast MEC analyzed (1/1). No oncogenic fusion genes were detected in breast PA1, and no additional oncogenic fusion genes were detected in the cases studied. The presence of the fusion genes identified was validated by fluorescence in situ hybridization (n = 1), reverse transcription-PCR (n = 1), or by both methods (n = 1). Taken together, our findings indicate that PAs and MECs arising in the breast resemble their salivary gland counterparts not only phenotypically but also at the genetic level. Furthermore, our data suggest that the molecular analysis of breast PAs and MECs might constitute a useful tool to aid in their differential diagnosis.

Clinical and genomic features of adult and paediatric acute leukaemias with ophthalmic manifestations

Objective

To describe the clinicopathological and genomic features of nine patients with primary and secondary orbital/ocular manifestations of leukaemia.

Methods

All orbital/ocular leukaemic specimens from 1980 to 2009 were collected from the Danish Register of Pathology. In six cases, medical records and formalin-fixed, paraffin-embedded blocks were available. Three cases from the Department of Pathology, Royal Liverpool University Hospital, were also included. Immunophenotypes and MYB oncoprotein expression were ascertained by immunohistochemistry. Genomic imbalances were analysed with comparative genomic hybridisation arrays and oncogene rearrangements with fluorescence in situ hybridisation.

Results

Four patients had B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) and five had acute myeloid leukaemia (AML). Two patients with BCP-ALL and one with AML had primary orbital manifestations of leukaemia. Common symptoms were proptosis, displacement of the eye, and reduced eye mobility in patients with orbital leukaemias and pain, and reduced visual acuity in patients with ocular leukaemias. All patients with primary orbital lesions were alive up to 18 years after diagnosis. All but one patient with secondary ophthalmic manifestations died of relapse/disseminated disease. ETV6 and RUNX1 were rearranged in BCP-ALL, and RUNX1 and KMT2A in AML. Genomic profiling revealed quiet genomes (0–7 aberrations/case). The MYB oncoprotein was overexpressed in the majority of cases.

Conclusions

Leukaemias with and without ophthalmic manifestations have similar immunophenotypes, translocations/gene fusions and copy number alterations. Awareness of the clinical spectrum of leukaemic lesions of the eye or ocular region is important to quickly establish the correct diagnosis and commence prompt treatment.

Impact of MDM2, TP53 and P14ARF Polymorphisms on Endometrial Cancer Risk and Onset

BACKGROUND/AIM

The aim of this study was to determine the joint effect of single nucleotide polymorphisms (SNPs) of MDM2, TP53, and CDKN2A (P14ARF) genes on the onset and course of endometrial cancer (EC) in postmenopausal women.

MATERIALS AND METHODS

The study group consisted of 144 EC women and 50 non-cancer controls. MDM2 rs22279744, TP53 rs1042522, and P14ARF rs3088440, rs3731217, and rs3731245 SNPs were analysed.

RESULTS

The double-SNP combinations T-C, T-T, or T-G in MDM2 SNP 309 and P14ARF polymorphisms decreased EC risk. The triple-SNP combinations T-C-T, T-C-G, or T-T-G in MDM2 SNP and two P14ARF polymorphisms decreased EC risk. The multiple-SNP combination T-C-T-G in MDM2 and three P14ARF polymorphisms decreased EC risk. The G-Arg-C-T-G carriers were at increased EC risk, while the T-Arg-C-T-G carriers were at decreased EC risk.

CONCLUSION

MDM2 SNP309 plays a role in EC onset in postmenopausal women.

c-Myb regulates tumorigenic potential of embryonal rhabdomyosarcoma cells

Rhabdomyosarcomas (RMS) are a heterogeneous group of mesodermal tumors, the most common sub-types are embryonal (eRMS) and alveolar (aRMS) rhabdomyosarcoma. Immunohistochemical analysis revealed c-Myb expression in both eRMS and aRMS. c-Myb has been reported to be often associated with malignant human cancers. We therefore investigated the c-Myb role in RMS using cellular models of RMS. Specific suppression of c-Myb by a lentiviral vector expressing doxycycline (Dox)-inducible c-Myb shRNA inhibited proliferation, colony formation, and migration of the eRMS cell line (RD), but not of the aRMS cell line (RH30). Upon c-Myb knockdown in eRMS cells, cells accumulated in G0/G1 phase, the invasive behaviour of cells was repressed, and elevated levels of myosin heavy chain, marker of muscle differentiation, was detected. Next, we used an RD-based xenograft model to investigate the role of c-Myb in eRMS tumorigenesis in vivo. We found that Dox administration did not result in efficient suppression of c-Myb in growing tumors. However, when c-Myb-deficient RD cells were implanted into SCID mice, we observed inefficient tumor grafting and attenuation of tumor growth during the initial stages of tumor expansion. The presented study suggests that c-Myb could be a therapeutic target in embryonal rhabdomyosarcoma assuming that its expression is ablated.

c-MYB and DMTF1 in Cancer

The c-Myb gene encodes a transcription factor that regulates cell proliferation, differentiation, and apoptosis through protein-protein interaction and transcriptional regulation of signaling pathways. The protein is frequently overexpressed in human leukemias, breast cancers, and other solid tumors suggesting that it is a bona fide oncogene. c-MYB is often overexpressed by translocation in human tumors with t(6;7)(q23;q34) resulting in c-MYB-TCRβ in T cell ALL, t(X;6)(p11;q23) with c-MYB-GATA1 in acute basophilic leukemia, and t(6;9)(q22-23;p23-24) with c-MYB-NF1B in adenoid cystic carcinoma. Antisense oligonucleotides to c-MYB were developed to purge bone marrow cells to eliminate tumor cells in leukemias. Recently, small molecules that inhibit c-MYB activity have been developed to disrupt its interaction with p300. The Dmp1 (cyclin D binding myb-like protein 1; Dmtf1) gene was isolated through its virtue for binding to cyclin D2. It is a transcription factor that has a Myb-like repeat for DNA binding. The Dmtf1 protein directly binds to the Arf promoter for transactivation and physically interacts with p53 to activate the p53 pathway. The gene is hemizygously deleted in 35-42% of human cancers and is associated with longer survival. The significances of aberrant expression of c-MYB and DMTF1 proteins in human cancers and their clinical significances are discussed.

Clinical Utility of In Situ Hybridization Assays in Head and Neck Neoplasms

Head and neck pathology present a unique set of challenges including the morphological diversity of the neoplasms and presentation of metastases of unknown primary origin. The detection of human papillomavirus and Epstein-Barr virus associated with squamous cell carcinoma and newer entities like HPV-related carcinoma with adenoid cystic like features have critical prognostic and management implications. In salivary gland neoplasms, differential diagnoses can be broad and include non-neoplastic conditions as well as benign and malignant neoplasms. The detection of specific gene rearrangements can be immensely helpful in reaching the diagnosis in pleomorphic adenoma, mucoepidermoid carcinoma, secretory carcinoma, hyalinizing clear cell carcinoma and adenoid cystic carcinoma. Furthermore, molecular techniques are essential in diagnosis of small round blue cell neoplasms and spindle cell neoplasms including Ewing sarcoma, rhabdomyosarcoma, synovial sarcoma, biphenotypic sinonasal sarcoma, dermatofibrosarcoma protuberans, nodular fasciitis and inflammatory myofibroblastic tumor. The detection of genetic rearrangements is also important in lymphomas particularly in identifying 'double-hit' and 'triple-hit' lymphomas in diffuse large B cell lymphoma. This article reviews the use of in situ hybridization in the diagnosis of these neoplasms.

UM-HACC-2A: MYB-NFIB fusion-positive human adenoid cystic carcinoma cell line

OBJECTIVES

Limited availability of validated human adenoid cystic carcinoma (ACC) cell lines has hindered the mechanistic understanding of the pathobiology of this malignancy and the development of effective therapies. The purpose of this work was to generate and characterize a human ACC cell line.

MATERIAL AND METHODS

Immediately after surgery, a tumor fragment from a minor salivary gland from the tongue of a female Caucasian was minced, dissociated, and a single cell suspension was plated in fibronectin-coated flasks. A culture medium containing bovine brain extract and rhEGF was optimized for these cells. Whole exome sequencing was used to evaluate the presence of MYB-NFIB translocation.

RESULTS

The University of Michigan-Human Adenoid Cystic Carcinoma (UM-HACC)-2A cells showed continuous growth in monolayers for at least 180 in vitro passages while maintaining epithelial morphology. Short-tandem repeat (STR) profiling confirmed a 100% match to patient DNA. Whole exome sequencing revealed the presence of the MYB-NFIB fusion in UM-HACC-2A cells, which was confirmed by PCR analysis. Western blots revealed high expression of epithelial markers (e.g. E-cadherin, EGFR, pan-cytokeratin) and proteins associated with ACC (e.g. c-Myb, p63). Developmental therapeutic studies showed that UM-HACC-2A cells were resistant to cisplatin (IC₅₀ = 44.7 µM) while more responsive to paclitaxel (IC₅₀ = 0.0006 µM). In a pilot study, we observed that UM-HACC-2A cells survived orthotopic transplantation into the submandibular gland. Notably, one of the mice injected with UM-HACC-2A cells exhibited lung metastasis after 6 months.

CONCLUSION

UM-HACC-2A is a MYB-NFIB fusion-positive ACC cell line that is suitable for mechanistic and developmental therapeutics studies.

MYB - A regulatory factor in hematopoiesis

MYB is a transcription factor which was identified in birds as a viral oncogene (v-MYB). Its cellular counterpart was subsequently isolated as c-MYB which has three functional domains - DNA binding domain, transactivation domain and negative regulatory domain. c-MYB is essential for survival, and deletion of both alleles of the gene results in embryonic death. It is highly expressed in hematopoietic cells, thymus and neural tissue, and required for T and B lymphocyte development and erythroid maturation. Additionally, aberrant MYB expression has been found in numerous solid cancer cells and human leukemia. Recent studies have also implicated c-MYB in the regulation of expression of fetal hemoglobin which is highly beneficial to the β-hemoglobinopathies (beta thalassemia and sickle cell disease). These findings suggest that MYB could be a potential therapeutic target in leukemia, and possibly also a target for therapeutic increase of fetal hemoglobin in the β-hemoglobinopathies.

Silencing miR-150 Ameliorates Experimental Autoimmune Encephalomyelitis

MiR-150 regulates maturation and differentiation of T cells but how it functions in multiple sclerosis (MS) is unclear. In miR-150 knockout (KO) mice, we examined the effect of miR-150 deletion on disease severity of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. After deleting miR-150, EAE disease severity was reduced according to clinical score. Histological staining and MBP immunofluorescence staining revealed that miR-150 deletion limited the extent of inflammatory demyelination and axonal damage in the spinal cord. Flow cytometry showed that CD3+, CD4+, and CD8+ T cells were increased in WT-EAE mice, but miR-150 deletion significantly reversed EAE-mediated up-regulation of CD3+, CD4+, and CD8+ T cells and down-regulation of CD19+ B cells. In addition, miR-150 deletion reduced the mRNA expression of IL-1β, IL-6, IL-17, and TNF-α in spleen and spinal cord after EAE induction. Thus, miR-150 deletion reduces EAE severity and demyelination, probably through inhibiting the activated immune response and the inflammation in the central nervous system.

Genetic rearrangements, hotspot mutations, and microRNA expression in the progression of metastatic adenoid cystic carcinoma of the salivary gland

Adenoid cystic carcinoma (ACC) is among the most common salivary gland malignancies, and is notorious for its unpredictable clinical course with frequent local recurrences and metastatic spread. However, the molecular mechanisms for metastatic spread are poorly understood. This malignancy is known to frequently harbor gene fusions involving MYB, MYBL1, and NFIB, and to have a low mutational burden. Most studies have focused on primary tumors to understand the biology of ACC, but this has not revealed a genetic cause for metastatic dissemination in the majority of cases. Hence, other molecular mechanisms are likely to be involved. Here, we characterize the genetic and microRNA expressional landscape of primary ACC and corresponding metastatic lesions from 11 patients. FISH demonstrated preservation of MYB aberrations between primary tumors and metastases, and targeted next-generation sequencing identified mutations exclusive for the metastatic lesions in 3/11 cases (27.3%). Global microRNA profiling identified several differentially expressed miRNAs between primary ACC and metastases as compared to normal salivary gland tissue. Interestingly, individual tumor pairs differed in miRNA profile, but there was no general difference between primary ACCs and metastases. Collectively, we show that MYB and NFIB aberrations are consistently preserved in ACC metastatic lesions, and that additional mutations included in the 50-gene hotspot panel used are infrequently acquired by the metastatic lesions. In contrast, tumor pairs differ in microRNA expression and our data suggest that they are heterogeneous according to their microRNA profile. This adds an additional layer to the complex process of ACC metastatic spread.

From Oxidative Stress Damage to Pathways, Networks, and Autophagy via MicroRNAs

Oxidative stress can alter the expression level of many microRNAs (miRNAs), but how these changes are integrated and related to oxidative stress responses is poorly understood. In this article, we addressed this question by using in silico tools. We reviewed the literature for miRNAs whose expression is altered upon oxidative stress damage and used them in combination with various databases and software to predict common gene targets of oxidative stress-modulated miRNAs and affected pathways. Furthermore, we identified miRNAs that simultaneously target the predicted oxidative stress-modulated miRNA gene targets. This generated a list of novel candidate miRNAs potentially involved in oxidative stress responses. By literature search and grouping of pathways and cellular responses, we could classify these candidate miRNAs and their targets into a larger scheme related to oxidative stress responses. To further exemplify the potential of our approach in free radical research, we used our explorative tools in combination with ingenuity pathway analysis to successfully identify new candidate miRNAs involved in the ubiquitination process, a master regulator of cellular responses to oxidative stress and proteostasis. Lastly, we demonstrate that our approach may also be useful to identify novel candidate connections between oxidative stress-related miRNAs and autophagy. In summary, our results indicate novel and important aspects with regard to the integrated biological roles of oxidative stress-modulated miRNAs and demonstrate how this type of in silico approach can be useful as a starting point to generate hypotheses and guide further research on the interrelation between miRNA-based gene regulation, oxidative stress signaling pathways, and autophagy.

The impact of the MYB-NFIB fusion proto-oncogene in vivo

Recurrent fusion of the v-myb avian myelobastosis viral oncogene homolog (MYB) and nuclear factor I/B (NFIB) generates the MYB-NFIB transcription factor, which has been detected in a high percentage of individuals with adenoid cystic carcinoma (ACC). To understand the functional role of this fusion protein in carcinogenesis, we generated a conditional mutant transgenic mouse that expresses MYB-NFIB along with p53 mutation in tissues that give rise to ACC: mammary tissue, salivary glands, or systemically in the whole body. Expression of the oncogene in mammary tissue resulted in hyperplastic glands that developed into adenocarcinoma in 27.3% of animals. Systemic expression of the MYB-NFIB fusion caused more rapid development of this breast phenotype, but mice died due to abnormal proliferation in the glomerular compartment of the kidney, which led to development of glomerulonephritis. These findings suggest the MYB-NFIB fusion is oncogenic and treatments targeting this transcription factor may lead to therapeutic responses in ACC patients.

MYBL2 Is Targeted by miR-143-3p and Regulates Breast Cancer Cell Proliferation and Apoptosis

Breast cancer remains a public health issue on a global scale. The present study aimed to explore the functional role of MYB proto-oncogene like 2 (MYBL2) in breast cancer, as well as underlying mechanisms. The regulatory relationship between miR-143-3p and MYBL2 was analyzed, and the effects of dysregulation of miR-143-3p and MYBL2 on cell proliferation and apoptosis were investigated. The results showed that MYBL2 and miR-143-3p were inversely expressed in breast cancer tissues and cells: MYBL2 was highly expressed, whereas miR-143-3p was lowly expressed. MYBL2 was confirmed as a target gene of miR-143-3p. Suppression of MYBL2 inhibited proliferation and induced apoptosis of breast cancer cells, which was similar to the effects of overexpression of miR-143-3p. Our findings reveal that MYBL2 is targeted by miR-143-3p and regulates breast cancer cell proliferation and apoptosis.

Domain retention in transcription factor fusion genes and its biological and clinical implications: a pan-cancer study

Genomic rearrangements involving transcription factors (TFs) can form fusion proteins resulting in either enhanced, weakened, or even loss of TF activity. Functional domain (FD) retention is a critical factor in the activity of transcription factor fusion genes (TFFGs). A systematic investigation of FD retention in TFFGs and their outcome (e.g. expression changes) in a pan-cancer study has not yet been completed. Here, we examined the FD retention status in 386 TFFGs across 13 major cancer types and identified 83 TFFGs involving 67 TFs that retained FDs. To measure the potential biological relevance of TFs in TFFGs, we introduced a Major Active Isofusion Index (MAII) and built a prioritized TFFG network using MAII scores and the observed frequency of fusion positive samples. Interestingly, the four TFFGs (PML-RARA, RUNX1-RUNX1T1, TMPRSS2-ERG, and SFPQ-TFE3) with the highest MAII scores showed 50 differentially expressed target genes (DETGs) in fusion-positive versus fusion-negative cancer samples. DETG analysis revealed that they were involved in tumorigenesis-related processes in each cancer type. PLAU, which encodes plasminogen activator urokinase and serves as a biomarker for tumor invasion, was found to be consistently activated in the samples with the highest MAII scores. Among the 50 DETGs, 21 were drug targetable genes. Fourteen of these 21 DETGs were expressed in acute myeloid leukemia (AML) samples. Accordingly, we constructed an AML-specific TFFG network, which included 38 DETGs in RUNX1-RUNX1T1 or PML-RARA positive samples. In summary, this study revealed several TFFGs and their potential target genes, and provided insights into the clinical implications of TFFGs.

Genomic imbalances and MYB fusion in synchronous bilateral adenoid cystic carcinoma and invasive lobular carcinoma of the breast

The incidence of synchronous bilateral breast carcinomas (BBCs) has increased with a more frequent use of magnetic resonance imaging screening of the contralateral breast in women with newly diagnosed breast cancer. A total of 30% of all BBCs occur synchronously. In the present study, we describe a unique case of synchronous BBC in a 59-year-old previously healthy woman with no known family history of breast or ovarian cancer. At the time of diagnosis the patient had an invasive lobular carcinoma (ILC) in the right breast and an adenoid cystic carcinoma (ACC) in the left breast. To the best of our knowledge, this is the first published case of bilateral, simultaneously occurring ACC and ILC of the breast. Genome-wide genomic profiling of the tumors revealed that they had distinctly different genomic imbalances. The ACC had a 5.7 Mb interstitial 6q deletion with a breakpoint located in the 3′-part of MYB, resulting in loss of the last coding exon of MYB and its 3′-UTR. RT-PCR analysis confirmed that the tumor expressed an ACC-specific MYB-NFIB fusion transcript. In contrast, the ILC had no rearrangements of 6q or MYB-NFIB gene fusion but showed instead gain of 1q21.1-qter, loss of 16q11.2-qter, and 22q12.2-q12.3 as the sole genomic imbalances. Notably, concurrent gains of 1q and losses of 16q are characteristic features of ILC. Collectively, our findings indicate that the ACC and ILC had originated independently of each other and that the MYB-NFIB fusion is a specific biomarker for breast ACC.

How Phenotype Guides Management of the Most Common Malignant Salivary Neoplasms of the Larynx?

Salivary gland carcinomas of the larynx are uncommon. Adenoid cystic carcinoma is the most prevalent type of salivary gland carcinoma in this region, although other histologies such as mucoepidermoid carcinoma and adenocarcinomas have been reported. These tumors may present with advanced-stage due to nonspecific symptoms and their relatively slow-growing nature. The index of suspicion for a non-squamous cell carcinoma entity should be high when a submucosal mass is present. An accurate diagnosis is mandatory due to the impact each biologic entity has on treatment and outcome. Data concerning treatment and outcome are scarce, but primary surgery with utmost focus on free surgical margins is the treatment of choice. The role of adjuvant radiotherapy has not been well defined, although there is an agreement that it should be considered in advanced-stage or high-grade disease. This review considers only the most common malignant salivary neoplasms of the larynx with a focus on clinical management of these tumors.

Adenoid cystic carcinoma of the lacrimal gland is frequently characterized by MYB rearrangement

PurposeAdenoid cystic carcinoma (ACC) represents ~10-15% of salivary neoplasms and almost universally exhibits a lethal clinical course. ACC is also known to occur in the lacrimal gland. ACC is characterized by its heterogeneous morphology and may demonstrate tubular, cribriform, and/or solid architectural patterns. Unfortunately, these histopathological features are not specific to ACC and can be seen in other salivary gland-type neoplasms, introducing a diagnostic dilemma. The discovery of fusion transcripts has revolutionized the diagnosis, surveillance, and treatment of epithelial malignancies. In several anatomic subsites ACC is frequently characterized by a fusion transcript involving genes MYB and NFIB; more specifically, t(6;9)(q22-23;p23-24). This study explores the incidence of MYB rearrangement in cases of lacrimal gland ACC using fluorescent in situ hybridization.Materials and methodsRetrospective clinical and histopathological review of 12 cases of lacrimal gland ACC seen at Mayo Clinic over a 25-year period (1990-2015) was performed. Demographic and clinical data were obtained from medical records. Surgical pathology archival material including H&E slides and immunostains was re-examined. Formalin-fixed paraffin-embedded material was further evaluated using immunohistochemistry when appropriate. Fluorescent in situ hybridization (FISH) using a MYB break-apart probe was applied to all histologically confirmed cases of ACC and benign salivary gland parenchyma.ResultsThe median patient age was 53.6 years (range 12-64) and distributed equally by gender (six male and six female). Rearrangement of MYB was identified using FISH in seven cases (58%). Twenty-five sections of benign salivary gland parenchyma showed no evidence of MYB rearrangement. Primary surgical resection was most common treatment, and 78% of the patient received adjuvant radiation therapy. Median overall survival (OS) was 11 years. Rearrangement of MYB did not affect OS.ConclusionsIn summary, our results indicate that the MYB rearrangement defines a significant subset of lacrimal gland ACCs. Importantly, FISH for MYB rearrangement may be used as a diagnostic tool during pathological examination of lacrimal gland neoplasms. Our results showed no relationship between rearrangement status and clinical outcome. Lastly, the presence of t(6;9) in ACC may provide a platform for molecular-targeting strategies in the future.

Histopathologic and Cytogenetic Features of Pulmonary Adenoid Cystic Carcinoma

INTRODUCTION

A significant portion of adenoid cystic carcinoma (ACC) cases are characterized by a t(6;9)(q22-23;p23-24) translocation that originates a MYB-NFIB fusion oncogene. The MYB-NFIB fusion oncoprotein activates transcription of MYB-mediated pathways that impact cell cycle control, DNA repair, and apoptosis. This translocation seems highly specific for ACC. Moreover, therapies targeting MYB-activated pathways to treat ACC are being explored. Pulmonary ACC (PACC) has not been thoroughly studied for rearrangements of the MYB gene.

METHODS

Mayo Clinic Rochester surgical pathology archives (1972-2011) were searched for PACC. All cases were reviewed and classified according to the predominant histologic pattern (cribriform, solid, and tubular) by two surgical pathologists. Fluorescence in situ hybridization (FISH) was employed using a break-apart strategy to detect MYB rearrangement (at 6q23.3). Medical records were studied.

RESULTS

Forty cases of PACC were studied; tissue blocks were available for FISH analysis in 35 cases. Six cases failed to hybridize. In 12 of 29 cases (41%), the MYB gene region was disrupted, whereas 17 cases (59%) showed no evidence of rearrangement. FISH studies performed on other histologic subtypes of lung cancer (10 squamous cell carcinomas, 10 adenocarcinomas, and 10 small-cell carcinomas) failed to show MYB rearrangement. There was no significant difference in MYB rearrangement status with respect to predominant histologic pattern, clinical features, or clinical outcome.

CONCLUSIONS

A MYB rearrangement was identified in 41% of PACC and was 100% specific. FISH studies for MYB may be of diagnostic utility in PACC, particularly on small biopsy specimens. MYB rearrangement in PACC does not seem to be associated with clinical features or prognosis.

Targeted Cancer Therapy: Vital Oncogenes and a New Molecular Genetic Paradigm for Cancer Initiation Progression and Treatment

It has been declared repeatedly that cancer is a result of molecular genetic abnormalities. However, there has been no working model describing the specific functional consequences of the deranged genomic processes that result in the initiation and propagation of the cancer process during carcinogenesis. We no longer need to question whether or not cancer arises as a result of a molecular genetic defect within the cancer cell. The legitimate questions are: how and why? This article reviews the preeminent data on cancer molecular genetics and subsequently proposes that the sentinel event in cancer initiation is the aberrant production of fused transcription activators with new molecular properties within normal tissue stem cells. This results in the production of vital oncogenes with dysfunctional gene activation transcription properties, which leads to dysfunctional gene regulation, the aberrant activation of transduction pathways, chromosomal breakage, activation of driver oncogenes, reactivation of stem cell transduction pathways and the activation of genes that result in the hallmarks of cancer. Furthermore, a novel holistic molecular genetic model of cancer initiation and progression is presented along with a new paradigm for the approach to personalized targeted cancer therapy, clinical monitoring and cancer diagnosis.

Clinical and molecular insights into adenoid cystic carcinoma: Neural crest-like stemness as a target

OBJECTIVES

This review surveys trialed therapies and molecular defects in adenoid cystic carcinoma (ACC), with an emphasis on neural crest-like stemness characteristics of newly discovered cancer stem cells (CSCs) and therapies that may target these CSCs.

DATA SOURCES

Articles available on Pubmed or OVID MEDLINE databases and unpublished data.

REVIEW METHODS

Systematic review of articles pertaining to ACC and neural crest-like stem cells.

RESULTS

Adenoid cystic carcinoma of the salivary gland is a slowly growing but relentless cancer that is prone to nerve invasion and metastases. A lack of understanding of molecular etiology and absence of targetable drivers has limited therapy for patients with ACC to surgery and radiation. Currently, no curative treatments are available for patients with metastatic disease, which highlights the need for effective new therapies. Research in this area has been inhibited by the lack of validated cell lines and a paucity of clinically useful markers. The ACC research environment has recently improved, thanks to the introduction of novel tools, technologies, approaches, and models. Improved understanding of ACC suggests that neural crest-like stemness is a major target in this rare tumor. New cell culture techniques and patient-derived xenografts provide tools for preclinical testing.

CONCLUSION

Preclinical research has not identified effective targets in ACC, as confirmed by the large number of failed clinical trials. New molecular data suggest that drivers of neural crest-like stemness may be required for maintenance of ACC; as such, CSCs are a target for therapy of ACC.

The up-regulation of Myb may help mediate EGCG inhibition effect on mouse lung adenocarcinoma

Background

Green tea polyphenol epigallocatechin-3-gallate (EGCG) has been demonstrated to inhibit cancer in experimental studies through its antioxidant activity and modulations on cellular functions by binding specific proteins. By means of computational analysis and functional genomic approaches, we previously identified a set of protein coding genes and microRNAs whose expressions were significantly modulated in response to the EGCG treatment in tobacco carcinogen-induced lung adenocarcinoma in A/J mice. However, to what degree these genes are involved in the cancer inhibition of EGCG remains unclear.

Results

In this study, we further employed statistical methods and literature research to analyze these data in combination with The Cancer Genome Atlas (TCGA) lung adenocarcinoma datasets for additional data mining. Under the assumption that, if a gene mediates EGCG’s cancer inhibition, its expression level change caused by EGCG should be opposite to what occurred in the carcinogenesis, we identified Myb and Peg3 as the primary putative genes involved in the cancer inhibitory activity. Further analysis suggested that the regulation of Myb could be mediated through an EGCG-upregulated microRNA, miR-449c-5p.

Conclusions

Although the actions of EGCG involve multiple targets/pathways, further analysis by mining the existing genomic datasets revealed that the upregulations of Myb and Peg3 are likely the key anti-cancer events of EGCG in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-016-0072-4) contains supplementary material, which is available to authorized users.

Dysregulation of c-Myb Pathway by Aberrant Expression of Proto-oncogene MYB Provides the Basis for Malignancy in Adult T-cell Leukemia/lymphoma Cells

PURPOSE

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive human T-cell malignancy induced by human T-lymphotrophic virus-1 (HTLV-1) infection. The genetic alterations in infected cells that lead to transformation have not been completely elucidated, thus hindering the identification of effective therapeutic targets for ATL. Here, we present the first assessment of MYB proto-oncogene dysregulation in ATL and an exploration of its role in the onset of ATL.

EXPERIMENTAL DESIGN

We investigated the expression patterns of MYB splicing variants in ATL. The molecular characteristics of the c-Myb-9A isoform, which was overexpressed in ATL cells, were examined using chromatin immunoprecipitation and promoter assays. We further examined the biologic impacts of abnormal c-Myb overexpression in ATL using overall c-Myb knockdown with shRNA or c-Myb-9A knockdown with morpholino oligomers.

RESULTS

Both total c-Myb and c-Myb-9A, which exhibited strong transforming activity, were overexpressed in ATL cells in a leukemogenesis- and progression-dependent manner. Knockdown of either total c-Myb or c-Myb-9A induced ATL cell death. c-Myb transactivates nine genes that encode essential regulators of cell proliferation and NF-κB signaling. c-Myb-9A induced significantly stronger transactivation of all tested genes and stronger NF-κB activation compared with wild-type c-Myb.

CONCLUSIONS

Our data demonstrate that c-Myb pathway overactivation caused by unbalanced c-Myb-9A overexpression is associated with disorders in cellular homeostasis and consequently, accelerated transformation, cell proliferation, and malignancy in ATL cells. These data support the notion of the c-Myb pathway as a promising new therapeutic target for ATL. Clin Cancer Res; 22(23); 5915-28. ©2016 AACR.

Genetic alterations in uncommon low-grade neuroepithelial tumors: BRAF, FGFR1, and MYB mutations occur at high frequency and align with morphology

Low-grade neuroepithelial tumors (LGNTs) are diverse CNS tumors presenting in children and young adults, often with a history of epilepsy. While the genetic profiles of common LGNTs, such as the pilocytic astrocytoma and 'adult-type' diffuse gliomas, are largely established, those of uncommon LGNTs remain to be defined. In this study, we have used massively parallel sequencing and various targeted molecular genetic approaches to study alterations in 91 LGNTs, mostly from children but including young adult patients. These tumors comprise dysembryoplastic neuroepithelial tumors (DNETs; n = 22), diffuse oligodendroglial tumors (d-OTs; n = 20), diffuse astrocytomas (DAs; n = 17), angiocentric gliomas (n = 15), and gangliogliomas (n = 17). Most LGNTs (84 %) analyzed by whole-genome sequencing (WGS) were characterized by a single driver genetic alteration. Alterations of FGFR1 occurred frequently in LGNTs composed of oligodendrocyte-like cells, being present in 82 % of DNETs and 40 % of d-OTs. In contrast, a MYB-QKI fusion characterized almost all angiocentric gliomas (87 %), and MYB fusion genes were the most common genetic alteration in DAs (41 %). A BRAF:p.V600E mutation was present in 35 % of gangliogliomas and 18 % of DAs. Pathogenic alterations in FGFR1/2/3, BRAF, or MYB/MYBL1 occurred in 78 % of the series. Adult-type d-OTs with an IDH1/2 mutation occurred in four adolescents, the youngest aged 15 years at biopsy. Despite a detailed analysis, novel genetic alterations were limited to two fusion genes, EWSR1-PATZ1 and SLMAP-NTRK2, both in gangliogliomas. Alterations in BRAF, FGFR1, or MYB account for most pathogenic alterations in LGNTs, including pilocytic astrocytomas, and alignment of these genetic alterations and cytologic features across LGNTs has diagnostic implications. Additionally, therapeutic options based upon targeting the effects of these alterations are already in clinical trials.

The landscape of gene fusions and somatic mutations in salivary gland neoplasms - Implications for diagnosis and therapy

Recent studies of the genomic landscape of salivary gland tumors have provided important insights into the molecular pathogenesis of these tumors. The most consistent alterations identified include a translocation-generated gene fusion network involving transcription factors, transcriptional coactivators, tyrosine kinase receptors, and other kinases. In addition, next-generation sequencing studies of a few subtypes of salivary neoplasms have revealed hotspot mutations in individual genes and mutations clustering to specific pathways frequently altered in cancer. Although limited, these studies have opened up new avenues for improved classification and targeted therapies of salivary gland cancers. In this review, we summarize the latest developments in this field, focusing on tumor types for which clinically important molecular data are available.

Resistance to Novel Antiandrogen Therapies in Metastatic Castration-Resistant Prostate Cancer

Despite the introduction of novel therapies that maximally decrease androgen-receptor (AR) signaling activity, metastatic castration-resistant prostate cancer (mCRPC) remains a lethal disease. Even though abiraterone and enzalutamide represent breakthroughs in the treatment of mCRPC and have demonstrated significant survival benefits, a significant proportion of patients have primary resistance to these agents and virtually all patients develop secondary resistance. While the mechanisms of resistance to these agents are not fully understood, many hypotheses of AR-dependent and AR-independent mechanisms are emerging, including upregulation of AR and cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17), induction of AR splice variants, AR point mutations, upregulation of glucocorticoid receptor, activation of alternative oncogenic signaling pathways, neuroendocrine transformation, and immune evasion via programmed death-ligand 1 upregulation. The aim of this review is to summarize the most clinically relevant mechanisms of resistance to novel androgen-directed agents, focusing on escape from enzalutamide and abiraterone.

Resistance to Novel Antiandrogen Therapies in Metastatic Castration-Resistant Prostate Cancer

Despite the introduction of novel therapies that maximally decrease androgen-receptor (AR) signaling activity, metastatic castration-resistant prostate cancer (mCRPC) remains a lethal disease. Even though abiraterone and enzalutamide represent breakthroughs in the treatment of mCRPC and have demonstrated significant survival benefits, a significant proportion of patients have primary resistance to these agents and virtually all patients develop secondary resistance. While the mechanisms of resistance to these agents are not fully understood, many hypotheses of AR-dependent and AR-independent mechanisms are emerging, including upregulation of AR and cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17), induction of AR splice variants, AR point mutations, upregulation of glucocorticoid receptor, activation of alternative oncogenic signaling pathways, neuroendocrine transformation, and immune evasion via programmed death-ligand 1 upregulation. The aim of this review is to summarize the most clinically relevant mechanisms of resistance to novel androgen-directed agents, focusing on escape from enzalutamide and abiraterone.

Analysis of somatic mutations in BRAF, CDKN2A/p16 and PI3KCA in patients with medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC), a neuroendocrine tumor originating from thyroid parafollicular cells, has been demonstrated to be associated with mutations in RET, HRAS, KRAS and NRAS. However, the role of other genes involved in the oncogenesis of neural crest tumors remains to be fully investigated in MTC. The current study aimed to investigate the presence of somatic mutations in BRAF, CDKN2A and PI3KCA in MTC, and to investigate the correlation with disease progression. DNA was isolated from paraffin‑embedded tumors and blood samples from patients with MTC, and the hotspot somatic mutations were sequenced. A total of 2 novel HRAS mutations, p.Asp33Asn and p.His94Tyr, and polymorphisms within the 3' untranslated region (UTR) of CDKN2A (rs11515 and rs3088440) were identified, however, no mutations were observed in other genes. It was suggested that somatic point mutations in BRAF, CDKN2A and PI3KCA do not participate in the oncogenesis of MTC. Further studies are required in order to clarify the contribution of the polymorphisms identified in the 3'UTR of CDKN2A in MTC.

Recurrent Fusions in MYB and MYBL1 Define a Common, Transcription Factor-Driven Oncogenic Pathway in Salivary Gland Adenoid Cystic Carcinoma

Adenoid cystic carcinoma (ACC), the second most common malignancy of salivary glands, is a rare tumor with a bleak prognosis for which therapeutic targets are unavailable. We used RNA sequencing (RNA-seq) to analyze low-quality RNA from archival, formaldehyde-fixed, paraffin-embedded samples. In addition to detecting the most common ACC translocation, t(6;9) fusing the MYB proto-oncogene to NFIB, we also detected previously unknown t(8;9) and t(8;14) translocations fusing the MYBL1 gene to the NFIB and RAD51B genes, respectively. RNA-seq provided information about gene fusions, alternative RNA splicing, and gene expression signatures. Interestingly, tumors with MYB and MYBL1 translocations displayed similar gene expression profiles, and the combined MYB and MYBL1 expression correlated with outcome, suggesting that the related MYB proteins are interchangeable oncogenic drivers in ACC. Our results provide important details about the biology of ACC and illustrate how archival tissue samples can be used for detailed molecular analyses of rare tumors.

SIGNIFICANCE

Using RNA-seq to perform whole-transcriptome analysis of archival ACC tumor samples, we identified novel, recurrent gene fusions, detected alternative RNA splicing, and established gene expression signatures that provide detailed information about the biology of ACC tumors.

c-Myb Binding Sites in Haematopoietic Chromatin Landscapes

Strict control of tissue-specific gene expression plays a pivotal role during lineage commitment. The transcription factor c-Myb has an essential role in adult haematopoiesis and functions as an oncogene when rearranged in human cancers. Here we have exploited digital genomic footprinting analysis to obtain a global picture of c-Myb occupancy in the genome of six different haematopoietic cell-types. We have biologically validated several c-Myb footprints using c-Myb knockdown data, reporter assays and DamID analysis. We show that our predicted conserved c-Myb footprints are highly dependent on the haematopoietic cell type, but that there is a group of gene targets common to all cell-types analysed. Furthermore, we find that c-Myb footprints co-localise with active histone mark H3K4me3 and are significantly enriched at exons. We analysed co-localisation of c-Myb footprints with 104 chromatin regulatory factors in K562 cells, and identified nine proteins that are enriched together with c-Myb footprints on genes positively regulated by c-Myb and one protein enriched on negatively regulated genes. Our data suggest that c-Myb is a transcription factor with multifaceted target regulation depending on cell type.

Morphologically low-grade spiradenocarcinoma: a clinicopathologic study of 19 cases with emphasis on outcome and MYB expression

Spiradenocarcinoma is a rare skin adnexal neoplasm with potential for aggressive behavior, classified histologically into low- and high-grade tumors. Morphologically, low-grade tumors are thought to behave more favorably. Limited information is available, however, with only 18 published cases. To study their clinical behavior, histological features, and the diagnostic value of immunohistochemistry, 19 morphologically low-grade spiradenocarcinomas were retrieved and compared with 21 spiradenomas and cylindromas. H&E-stained sections were reviewed, follow-up was obtained, and immunohistochemistry for Ki-67, p53 and, MYB was performed. The tumors were solitary, measuring 0.8-7 cm (median: 2.7 cm), with a predilection for the head and neck of elderly patients (median age: 72 years; range 53-92) without gender bias. Histologically, the tumors were multinodular and located in deep dermis and subcutis. A pre-existing spiradenoma was present in all cases. The malignant component was characterized by expansile growth with loss of the dual cell population, up to moderate cytological atypia and increased mitotic activity (median: 10/10 HPF; range 1-28). Additional findings included squamoid differentiation (n=9), necrosis (n=7), and ulceration (n=5). P53 expression was variable and no significant differences were noted in the benign compared with the malignant parts of the tumors. In contrast, in the malignant components the Ki-67 proliferative index was slightly increased, and MYB expression was lost. Follow-up (median: 67 months; range: 13-132) available for 16 patients (84%) revealed a local recurrence rate of 19% but no metastases or disease-related mortality. In this large study with long-term follow-up, we demonstrate that spiradenocarcinomas with low-grade morphology pursue an indolent course, characterized by local recurrence only. Metastases and disease-related mortality appear to be exceptional. Lack of MYB expression may be useful as an additional aid in the diagnosis of these challenging tumors.