Analysis of MYB oncogene in transformed adenoid cystic carcinomas reveals distinct pathways of tumor progression

Salivary glands adenoid cystic carcinoma: a molecular profile update and potential implications

Adenoid cystic carcinoma (ACC) is an aggressive tumor with a high propensity for distant metastasis and perineural invasion. This tumor is more commonly found in regions of the head and neck, mainly the salivary glands. In general, the primary treatment modality for ACC is surgical resection and, in some cases, postoperative radiotherapy. However, no effective systemic treatment is available for patients with advanced disease. Furthermore, this tumor type is characterized by recurrent molecular alterations, especially rearrangements involving the MYB, MYBL1, and NFIB genes. In addition, they also reported copy number alterations (CNAs) that impact genes. One of them is C-KIT, mutations that affect signaling pathways such as NOTCH, PI3KCA, and PTEN, as well as alterations in chromatin remodeling genes. The identification of new molecular targets enables the development of specific therapies. Despite ongoing investigations into immunotherapy, tyrosine kinase inhibitors, and anti-angiogenics, no systemic therapy is approved by the FDA for ACC. In this review, we report the genetic and cytogenetic findings on head and neck ACC, highlighting possible targets for therapeutic interventions.

MYB-NFIB fusion transcript in Adenoid Cystic Carcinoma: current state of knowledge and future directions

Adenoid cystic carcinoma (ACC) is the most common type of salivary gland cancer that can also arise in other primary sites. Regardless of the site, most ACC cases carry a recurrent chromosomal translocation - t(6;9)(q22-23;p23-24) - involving the MYB oncogene and the NFIB transcription factor. Generally, a long sequence of MYB is fused to the terminal exons of NFIB, yet the break can occur in different exons for both genes, resulting in multiple chimeric variants. The fusion status can be determined by a number of methods, each of them with particular advantages. In vitro and in vivo studies have been conducted to understand the biological consequences of MYB-NFIB translocation, and such findings could contribute to improving the current inefficient therapeutic options for disseminated ACC. This review provides a discussion on relevant evidence in the context of ACC MYB-NFIB translocations to determine the current state of knowledge and discuss future directions.

A Dual-Site Inhibitor of CBP/p300 KIX is a Selective and Effective Modulator of Myb

The protein-protein interaction between the KIX motif of the transcriptional coactivator CBP/p300 and the transcriptional activator Myb is a high-value target due to its established role in certain acute myeloid leukemias (AML) and potential contributions to other cancers. However, the CBP/p300 KIX domain has multiple binding sites, several structural homologues, many binding partners, and substantial conformational plasticity, making it challenging to specifically target using small-molecule inhibitors. Here, we report a picomolar dual-site inhibitor (MybLL-tide) of the Myb-CBP/p300 KIX interaction. MybLL-tide has higher affinity for CBP/p300 KIX than any previously reported compounds while also possessing 5600-fold selectivity for the CBP/p300 KIX domain over other coactivator domains. MybLL-tide blocks the association of CBP and p300 with Myb in the context of the proteome, leading to inhibition of key Myb·KIX-dependent genes in AML cells. These results show that MybLL-tide is an effective, modifiable tool to selectively target the KIX domain and assess transcriptional effects in AML cells and potentially other cancers featuring aberrant Myb behavior. Additionally, the dual-site design has applicability to the other challenging coactivators that bear multiple binding surfaces.

Primary cutaneous adenoid cystic carcinoma: a clinicopathologic, immunohistochemical, and fluorescence in-situ hybridisation study of 13 cases

AIMS

This study aimed to investigate the clinical, histological, immunohistochemical and chromosomal features of primary cutaneous adenoid cystic carcinoma (PCACC).

METHODS AND RESULTS

We retrospectively analysed 13 cases identified on their clinicopathological features and performed fluorescence in-situ hybridisation (FISH) on six available cases. Head and neck (46.2%) were most commonly involved. The median age was 53 years, with a male predilection. Histologically, tumours were classified as grades 1 (eight), 2 (four) and 3 with high-grade transformation (HGT) (one). The HGT component was demonstrated as poorly differentiated carcinoma with multifocal necrosis and myoepithelial differentiation. Patients with one of the following factors: longest diameter of the lesion (≥ 1 cm), involvement of subcutaneous fat tissue and widely infiltrative border had a relatively higher rate of local recurrence, distant metastasis and death. Five of six cases were confirmed to have MYB translocation, while nuclear staining for MYB proto-oncogene, transcription factor (MYB) protein was found in four cases. During the follow-up (median = 64 months), two patients experienced local recurrences. One patient, who was classified as grade III PCACC with HGT, developed multiple metastases and died of disease. Another patient was alive with multiple metastases.

CONCLUSIONS

This is the largest single-institution study, to our knowledge, of PCACC in an Asian population. We describe the first case of scalp PCACC with HGT, which is the only death case in our series. PCACC tends to recur locally and has metastatic potential. PCACC with HGT has a poor prognosis.

Metastatic adenoid cystic carcinoma with high-grade transformation ("dedifferentiation") in pleural effusion and neck lymph node: A diagnostic challenge on cytology?

High-grade transformation (HGT) or "dedifferentiation" is an uncommon phenomenon among salivary gland carcinomas including adenoid cystic carcinoma (ACC), which is important to recognize because it is associated with increased tumor aggressiveness, with a high propensity for lymph node and distant metastases. ACC with HGT is histologically characterized by a distinct population of poorly differentiated cells with loss of the typical biphasic ductal and myoepithelial differentiation seen in conventional ACC, associated with pleomorphism, necrosis and increased mitotic activity. We report the cytologic features of a case of metastatic ACC-HGT in cervical lymph node and effusion, which, to the best of our knowledge, have not been described previously. When ACC presents both in atypical locations and with HGT, the danger of misdiagnosis is increased if the clinical history is lacking, incomplete or inaccurate. Since ACC-HGT are rare (and possibly underdiagnosed) and do not have a specific set of cytological and/or immunohistochemical features, it is important for practicing cytopathologists to be aware of the possibility of encountering them, especially in specimens from patients with a history of ACC, in order to render the correct diagnosis.

MYB promotes the growth and metastasis of salivary adenoid cystic carcinoma

The incidence of recurrent t(6;9) translocation of the MYB proto-oncogene to NFIB (the gene that encodes nuclear factor 1 B-type) in adenoid cystic carcinoma (ACC) tumour tissues is high. However, MYB [the gene that encodes transcriptional activator Myb (MYB)] overexpression is more common, indicating that MYB serves a key role in ACC. The current study aimed to investigate the role of MYB in salivary (S)ACC growth and metastasis. A total of 50 fresh-frozen SACC tissues and 41 fresh-frozen normal submandibular gland (SMG) tissues were collected to measure MYB mRNA expression, and to analyse the associations between MYB and epithelial-mesenchymal transition (EMT) markers. Compared with normal SMG tissue, SACC tissues demonstrated significantly increased MYB expression, with a high expression rate of 90%. Interestingly, MYB tended to be negatively correlated with CDH1 [the gene that encodes cadherin-1 (E-cadherin)] and positively correlated with VIM (the gene that encodes vimentin), suggesting that MYB is associated with SACC metastasis. To explore the role of MYB in SACC, the authors stably overexpressed and knocked down MYB in SACC cells. The authors of the current study demonstrated that MYB overexpression promoted SACC cell proliferation, migration and invasion, whereas its knockdown inhibited these activities. Additionally, when MYB was overexpressed, CDH1 expression was downregulated, and CDH2 (the gene that encodes cadherin-2), VIM and ACTA2 (the gene that encodes actin, aortic smooth muscle) expression was upregulated. Then, the effect of MYB on lung tumour metastasis was investigated in vivo in non-obese diabetic/severe combined immunodeficiency mice. MYB overexpressing and control cells were injected into the mice through the tail vein. The results revealed that MYB promoted SACC lung metastasis. Collectively, these results demonstrated that MYB is aberrantly overexpressed in SACC tissues, and promotes SACC cell proliferation and metastasis, indicating that MYB may be a novel therapeutic target for SACC.

Updates in Salivary Gland Fine Needle Aspiration Biopsy: The Use of the Milan System and Ancillary Testing

Salivary gland fine needle aspiration biopsies remain common specimens seen by most cytology services. The diagnostic diversity and overlap between many of the lesions seen with these biopsies impart many challenges for the cytopathologist, rendering most specific diagnoses impossible with cytology alone. Here, the use of the Milan System for the classification of salivary gland fine needle aspiration biopsy FNAB is discussed, together with the potential use of ancillary testing in arriving at definitive diagnoses.

Adenoid cystic carcinoma: emerging role of translocations and gene fusions

Adenoid cystic carcinoma (ACC), the second most common salivary gland malignancy, is notorious for poor prognosis, which reflects the propensity of ACC to progress to clinically advanced metastatic disease. Due to high long-term mortality and lack of effective systemic treatment, the slow-growing but aggressive ACC poses a particular challenge in head and neck oncology. Despite the advancements in cancer genomics, up until recently relatively few genetic alterations critical to the ACC development have been recognized. Although the specific chromosomal translocations resulting in MYB-NFIB fusions provide insight into the ACC pathogenesis and represent attractive diagnostic and therapeutic targets, their clinical significance is unclear, and a substantial subset of ACCs do not harbor the MYB-NFIB translocation. Strategies based on detection of newly described genetic events (such as MYB activating super-enhancer translocations and alterations affecting another member of MYB transcription factor family-MYBL1) offer new hope for improved risk assessment, therapeutic intervention and tumor surveillance. However, the impact of these approaches is still limited by an incomplete understanding of the ACC biology, and the manner by which these alterations initiate and drive ACC remains to be delineated. This manuscript summarizes the current status of gene fusions and other driver genetic alterations in ACC pathogenesis and discusses new therapeutic strategies stemming from the current research.

The convergent roles of the nuclear factor I transcription factors in development and cancer

The nuclear factor I (NFI) transcription factors play important roles during normal development and have been associated with developmental abnormalities in humans. All four family members, NFIA, NFIB, NFIC and NFIX, have a homologous DNA binding domain and function by regulating cell proliferation and differentiation via the transcriptional control of their target genes. More recently, NFI genes have also been implicated in cancer based on genomic analyses and studies of animal models in a variety of tumours across multiple organ systems. However, the association between their functions in development and in cancer is not well described. In this review, we summarise the evidence suggesting a converging role for the NFI genes in development and cancer. Our review includes all cancer types in which the NFI genes are implicated, focusing predominantly on studies demonstrating their oncogenic or tumour-suppressive potential. We conclude by presenting the challenges impeding our understanding of NFI function in cancer biology, and demonstrate how a developmental perspective may contribute towards overcoming such hurdles.

Primary cutaneous adenoid cystic carcinoma with MYB aberrations: report of three cases and comprehensive review of the literature

Adenoid cystic carcinoma (ACC) is a relatively rare slow-growing and often-aggressive epithelial-myoepithelial neoplasm that arises in multiple organs including the skin. The t(6;9) (q22-23;p23-24) translocation, resulting in a MYB-NFIB gene fusion has been found in ACCs from the salivary glands and other organs. Recently, MYB aberrations occurring in a subset (40%) of primary cutaneous ACC (PCACC) examples was described. Herein, we report three additional cases of PCACC harboring MYB aberrations. The tumors presented in three males aged 43, 81 and 55 years old and affected the extremities in the first two patients and the scalp in the third one. None of the patients had history of prior or concurrent ACC elsewhere. Lesions exhibited the classic ACC morphology of nests of basaloid cells arranged in cribriform and adenoid patterns. Sentinel lymph node biopsy was performed in two cases with one case showing lymph node positivity. Fluorescence in situ hybridization with break-apart probes for MYB and NFIB loci revealed that two cases showed MYB rearrangements while one case showed loss of one MYB signal. None of the cases showed NFIB rearrangements. We contribute with three additional cases of PCACC exhibiting MYB aberrations, the apparent driving genetic abnormality in these tumors.

Genetic events in the progression of adenoid cystic carcinoma of the breast to high-grade triple-negative breast cancer

Adenoid cystic carcinoma of the breast is a rare histological type of triple-negative breast cancer with an indolent clinical behavior, often driven by the MYB-NFIB fusion gene. Here we sought to define the repertoire of somatic genetic alterations in two adenoid cystic carcinomas associated with high-grade triple-negative breast cancer. The different components of each case were subjected to copy number profiling and massively parallel sequencing targeting all exons and selected regulatory and intronic regions of 488 genes. Reverse transcription PCR and fluorescence in situ hybridization were employed to investigate the presence of the MYB-NFIB translocation. The MYB-NFIB fusion gene was detected in both adenoid cystic carcinomas and their associated high-grade triple-negative breast cancer components. Although the distinct components of both cases displayed similar patterns of gene copy number alterations, massively parallel sequencing analysis revealed intratumor genetic heterogeneity. In case 1, progression from the trabecular adenoid cystic carcinoma to the high-grade triple-negative breast cancer was found to involve clonal shifts with enrichment of mutations affecting EP300, NOTCH1, ERBB2 and FGFR1 in the high-grade triple-negative breast cancer. In case 2, a clonal KMT2C mutation was present in the cribriform adenoid cystic carcinoma, solid adenoid cystic carcinoma and high-grade triple-negative breast cancer components, whereas a mutation affecting MYB was present only in the solid and high-grade triple-negative breast cancer areas and additional three mutations targeting STAG2, KDM6A and CDK12 were restricted to the high-grade triple-negative breast cancer. In conclusion, adenoid cystic carcinomas of the breast with high-grade transformation are underpinned by the MYB-NFIB fusion gene and, akin to other forms of cancer, may be constituted by a mosaic of cancer cell clones at diagnosis. The progression from adenoid cystic carcinoma to high-grade triple-negative breast cancer of no special type may involve the selection of neoplastic clones and/or the acquisition of additional genetic alterations.

Salivary gland hybrid tumour revisited: could they represent high-grade transformation in a low-grade neoplasm?

Salivary gland hybrid tumour, first described in 1996, is a very rare neoplasm for which exact morphological criteria have not been universally agreed upon. In contrast, the concept of high-grade transformation (HGT) in salivary neoplasms has been widely accepted during the last decade, and the number of reported cases is rapidly increasing. A review of the literature revealed 38 cases of hybrid tumour reported in 22 publications. During approximately the same time period, well over 100 cases of HGT in salivary neoplasms have been reported. There are important histological similarities between hybrid tumours and salivary tumours with HGT. In the latter, containing one tumour component of low-grade malignancy and the other of high grade, the two tumour components are not entirely separated and appear to originate in the same area. Virtually, all cases reported as hybrid tumour had no clear lines of demarcation between the two tumour types. We are inclined to suggest that most of the 38 cases of hybrid tumours described in the literature would today better be called tumour with HGT rather than hybrid tumour. The relative proportion of the two components may vary, and the high-grade component is sometimes very small, which emphasises the importance of very generous sampling of the surgical specimen. The molecular genetic mechanisms responsible for HGT, including what used to be called hybrid tumour, remain largely unknown. Abnormalities of a few genes (including p53, C-MYC, cyclin D1, HER-2/neu) have been documented. As insufficient data exist on gene abnormalities in these lesions, conclusions as to whether or not they have a common origin and which mechanisms are involved in transformation cannot be drawn. Due to the small number of cases reported, many of which lack follow-up details; indicators of prognosis of hybrid tumours are not available, but their behaviour seems to be similar to that of tumours with HGT, i.e. an accelerated aggressive course. HGT of salivary gland neoplasms greatly influences macroscopic and microscopic evaluation of the specimen but also, given the high incidence of metastases and morbidity, carries significant treatment implications.

Molecular Pathology: Predictive, Prognostic, and Diagnostic Markers in Salivary Gland Tumors

Although initial attempts at using ancillary studies in salivary gland tumor classification were viewed with skepticism, numerous advances over the past decade have established a role for assessment of molecular alterations in the diagnosis and potential prognosis and treatment of salivary gland tumors. Many monomorphic salivary tumors are now known to harbor defining molecular alterations, usually translocations. Pleomorphic, high-grade carcinomas tend to have complex alterations that are often further limited by inaccuracy of initial classification by morphologic and immunophenotypic features. Next-generation sequencing techniques have great potential in many aspects of salivary gland tumor classification and biomarker discovery.

Novel Genetic Loci Associated with the Plasma Triglyceride Response to an Omega-3 Fatty Acid Supplementation

BACKGROUND

A recent genome-wide association study (GWAS) by our group identified 13 loci associated with the plasma triglyceride (TG) response to omega-3 (n-3) fatty acid (FA) supplementation. This study aimed to test whether single-nucleotide polymorphisms (SNPs) within the IQCJ, NXPH1, PHF17 and MYB genes are associated with the plasma TG response to an n-3 FA supplementation.

METHODS

A total of 208 subjects followed a 6-week n-3 FA supplementation of 5 g/day of fish oil (1.9-2.2 g of eicosapentaenoic acid and 1.1 g of docosahexaenoic acid). Measurements of plasma lipids were made before and after the supplementation. Sixty-seven tagged SNPs were selected to increase the density of markers near GWAS hits.

RESULTS

In a repeated model, independent effects of the genotype and the gene-supplementation interaction were associated with plasma TG. Genotype effects were observed with two SNPs of NXPH1, and gene-diet interactions were observed with ten SNPs of IQCJ, four SNPs of NXPH1 and three SNPs of MYB. Positive and negative responders showed different genotype frequencies with nine SNPs of IQCJ, two SNPs of NXPH1 and two SNPs of MYB.

CONCLUSION

Fine mapping in GWAS-associated loci allowed the identification of SNPs partly explaining the large interindividual variability observed in plasma TG levels in response to an n-3 FA supplementation.

Cervical Lymph Node Metastasis in High-Grade Transformation of Head and Neck Adenoid Cystic Carcinoma: A Collective International Review

Adenoid cystic carcinoma (AdCC) is among the most common malignant tumors of the salivary glands. It is characterized by a prolonged clinical course, with frequent local recurrences, late onset of metastases and fatal outcome. High-grade transformation (HGT) is an uncommon phenomenon among salivary carcinomas and is associated with increased tumor aggressiveness. In AdCC with high-grade transformation (AdCC–HGT), the clinical course deviates from the natural history of AdCC. It tends to be accelerated, with a high propensity for lymph node metastasis. In order to shed light on this rare event and, in particular, on treatment implications, we undertook this review: searching for all published cases of AdCC-HGT. We conclude that it is mandatory to perform elective neck dissection in patients with AdCC-HGT, due to the high risk of lymph node metastases associated with transformation.

MYB is a novel regulator of pancreatic tumour growth and metastasis

BACKGROUND

MYB encodes for a transcription factor regulating the expression of a wide array of genes involved in cellular functions. It is reported to be amplified in a sub-set of pancreatic cancer (PC) cases; however, its pathobiological association has remained unclear thus far.

METHODS

Expression of MYB and other cellular proteins was analysed by immunoblot or qRT-PCR analyses. MYB was stably overexpressed in non-expressing (BxPC3) and silenced in highly expressing (MiaPaCa and Panc1) PC cells. Effect on growth was analysed by automated cell counting at 24-h interval. Cell-cycle progression and apoptotic indices of PC cells with altered MYB expression were measured through flow cytometry upon staining with respective biomarkers. Cell motility/invasion was examined in a Boyden's chamber assay using non-coated or Matrigel-coated membranes. Effect on tumorigenicity and metastatic potential was examined by non-invasive imaging and through end-point measurements of luciferase-tagged MYB-altered PC implanted in the pancreas of nude mice.

RESULTS

MYB was aberrantly expressed in all malignant cases of pancreas, whereas remained undetectable in normal pancreas. All the tested established PC cell lines except BxPC3 also exhibited MYB expression. Forced expression of MYB in BxPC3 cells promoted their growth, cell-cycle progression, survival and malignant behaviour, whereas its silencing in MiaPaCa and Panc1 cells produced converse effects. More importantly, ectopic MYB expression was sufficient to confer tumorigenic and metastatic capabilities to non-tumorigenic BxPC3 cells, while its silencing resulted in significant loss of the same in MYB-overexpressing cells as demonstrated in orthotopic mouse model. We also identified several MYB-regulated genes in PC cells that might potentially mediate its effect on tumour growth and metastasis.

CONCLUSIONS

MYB is aberrantly overexpressed in PC cells and acts as a key determinant of pancreatic tumour growth and metastasis.

A unifying gene signature for adenoid cystic cancer identifies parallel MYB-dependent and MYB-independent therapeutic targets

MYB activation is proposed to underlie development of adenoid cystic cancer (ACC), an aggressive salivary gland tumor with no effective systemic treatments. To discover druggable targets for ACC, we performed global mRNA/miRNA analyses of 12 ACC with matched normal tissues, and compared these data with 14 mucoepidermoid carcinomas (MEC) and 11 salivary adenocarcinomas (ADC). We detected a unique ACC gene signature of 1160 mRNAs and 22 miRNAs. MYB was the top-scoring gene (18-fold induction), however we observed the same signature in ACC without detectable MYB gene rearrangements. We also found 4 ACC tumors (1 among our 12 cases and 3 from public databases) with negligible MYB expression that retained the same ACC mRNA signature including over-expression of extracellular matrix (ECM) genes. Integration of this signature with somatic mutational analyses suggests that NOTCH1 and RUNX1 participate with MYB to activate ECM elements including the VCAN/HAPLN1 complex. We observed that forced MYB-NFIB expression in human salivary gland cells alters cell morphology and cell adhesion in vitro and depletion of VCAN blocked tumor cell growth of a short-term ACC tumor culture. In summary, we identified a unique ACC signature with parallel MYB-dependent and independent biomarkers and identified VCAN/HAPLN1 complexes as a potential target.

Sinonasal carcinoma: clinical, pathological, genetic and therapeutic advances

The sinonasal cavities represent an anatomical region affected by a variety of tumours with clinical, aetiological, pathological, and genetic features distinct from tumours at the main head and neck cancer localizations. Together, squamous-cell carcinoma and adenocarcinoma account for 80% of all sinonasal tumours, and are aetiologically associated with professional exposure to wood and leather dust particles and other industrial compounds, and therefore, are officially recognized as an occupational disease. Owing to their distinctive characteristics, sinonasal tumours should be considered as separate entities, not to be included in the miscellany of head and neck cancers. Sinonasal tumours are rare, with an annual incidence of approximately 1 case per 100,000 inhabitants worldwide, a fact that has hampered molecular-genetic studies of the tumorigenic pathways and the testing of alternative treatment strategies. Nevertheless, the clinical management of sinonasal cancer has improved owing to advances in imaging techniques, endoscopic surgical approaches, and radiotherapy. Genetic profiling and the development of in vitro cell lines and animal models currently form the basis for future targeted anticancer therapies. We review these advances in our understanding and treatment of sinonasal tumours.