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

A cytodiagnosis of adenoid cystic carcinoma of the tracheobronchial tree through a systematic clinical case comparison and analysis

BACKGROUND

Primary adenoid cystic carcinoma (AdCC) of the tracheobronchial tree is very rare with a high risk for recurrence and metastasis. The diagnosis of AdCC by histologic and immunohistochemical means has been well studied clinically. However, the identification of AdCC by cytologic features remains elusive due to the atypical features the cancer presents. This study aimed to describe the cytologic features of AdCC by using bronchial brushing, which could aid in distinguishing AdCC from other pulmonary carcinomas.

METHODS

The cytopathological features of bronchial brushing smears collected from seven cases were histologically diagnosed as AdCC. The defined cytologic features, which could potentially be diagnostic, were systemically analyzed.

RESULTS

Four out of the seven cytologic cases were inconcordance with the histologic diagnosis and cytologically classified as positive for malignant cells, small cell carcinoma, or atypical cells. Three cases showed a characteristic adenoid structure and magenta stroma forming globule, which was distinguished from the four cases. Cytologically, the above mentioned three cases were uniform with relatively small bland nuclei and little cytoplasm. In this study, only one case showed atypical polygonal medium-sized cells with conspicuous nucleoli.

CONCLUSIONS

Unlike fine-needle aspiration cytology, magenta stroma globules might offer an alternate clue for cytodiagnosis of AdCC clinically. Bronchial brushings cytology was more present in bland uniform cells with high nuclear to cytoplasmic ratios and background mucoid substance. More cases should be collected and confirmed using histopathology with careful film reading to reduce the rate of misdiagnosis.

Therapeutic inhibition of Bmi-1 ablates chemoresistant cancer stem cells in adenoid cystic carcinoma

OBJECTIVES

Adenoid Cystic Carcinomas (ACC) typically show modest responseto cytotoxic therapy. Cancer stem cells (CSC) have been implicated in chemoresistance and tumor relapse. However, their role in ACC remains unknown. The purpose of this work was to evaluate the impact of targeting ACC CSCs with Bmi-1 inhibitors on resistance to cytotoxic therapy and tumor relapse.

MATERIALS AND METHODS

Therapeutic efficacy of a small molecule inhibitor of Bmi-1 (PTC596; Unesbulin) and/or Cisplatin on ACC stemness was evaluated in immunodeficient mice harboring PDX ACC tumors (UM-PDX-HACC-5) and in human ACC cell-lines (UM-HACC-2A,-14) or low passage primary human ACC cells (UM-HACC-6). The effect of therapy on stemness was examined by salisphere assays, flow cytometry for ALDH activity and CD44 expression, and Western blots for Bmi-1 (self-renewal marker) and Oct4 (embryonic stem cell marker) expression.

RESULTS

Platinum-based agents (Cisplatin, Carboplatin) induced Bmi-1 and Oct4 expression, increased salisphere formation and the CSC fraction in vitro and in vivo. In contrast, PTC596 inhibited expression of Bmi-1, Oct4 and pro-survival proteins Mcl-1 and Claspin; decreased the number of salispheres, and the fraction of ACC CSCs in vitro. Silencing Claspin decreased salisphere formation and CSC fraction. Both, single agent PTC596 and PTC596/Cisplatin combination decreased the CSC fraction in PDX ACC tumors. Notably, short-term combination therapy (2 weeks) with PTC596/Cisplatin prevented tumor relapse for 150 days in a preclinical trial in mice.

CONCLUSION

Therapeutic inhibition of Bmi-1 ablates chemoresistant CSCs and prevents ACC tumor relapse. Collectively, these results suggest that ACC patients might benefit from Bmi-1-targeted therapies.

MYB RNA detection by in situ hybridisation has high sensitivity and specificity for the diagnosis of adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is one of the most common primary salivary gland cancers. ACC has several benign and malignant mimics amongst salivary gland neoplasms. An accurate diagnosis of ACC is essential for optimal management of the patients and their follow-up. Upregulation of MYB has been described in 85-90% of ACC, but not in other salivary gland neoplasms. In ACC, MYB upregulation can occur as a result of a genetic rearrangement t(6;9) (q22-23;p23-24), MYB copy number variation (CNV), or enhancer hijacking of MYB. All mechanisms of MYB upregulation result in increased RNA transcription that can be detected using RNA in situ hybridisation (ISH) methods. In this study, utilising 138 primary salivary gland neoplasms including 78 ACC, we evaluate the diagnostic utility of MYB RNA ISH for distinguishing ACC from other primary salivary gland neoplasms with a prominent cribriform architecture including pleomorphic adenoma, basal cell adenoma, basal cell adenocarcinoma, epithelial myoepithelial carcinoma, and polymorphous adenocarcinoma. Fluorescent in situ hybridisation and next generation sequencing were also performed to evaluate the sensitivity and specificity of RNA ISH for detecting increased MYB RNA when MYB gene alterations were present. Detection of MYB RNA has 92.3% sensitivity and 98.2% specificity for a diagnosis of ACC amongst salivary gland neoplasms. The sensitivity of MYB RNA detection by ISH (92.3%) is significantly higher than that of the FISH MYB break-apart probe (42%) for ACC. Next generation sequencing did not demonstrate MYB alterations in cases that lacked MYB RNA overexpression indicating high sensitivity of MYB RNA ISH for detecting MYB gene alterations. The possibility that the sensitivity may be higher in clinical practice with contemporary samples as compared with older retrospective tissue samples with RNA degradation is not entirely excluded. In addition to the high sensitivity and specificity, MYB RNA testing can be performed using standard IHC platforms and protocols and evaluated using brightfield microscopy making it a time and cost-efficient diagnostic tool in routine clinical practice.

Molecular Aspects and Therapeutic Implications of Herbal Compounds Targeting Different Types of Cancer

Due to genetic changes in DNA (deoxyribonucleic acid) sequences, cancer continues to be the second most prevalent cause of death. The traditional target-directed approach, which is confronted with the importance of target function in healthy cells, is one of the most significant challenges in anticancer research. Another problem with cancer cells is that they experience various mutations, changes in gene duplication, and chromosomal abnormalities, all of which have a direct influence on the potency of anticancer drugs at different developmental stages. All of these factors combine to make cancer medication development difficult, with low clinical licensure success rates when compared to other therapy categories. The current review focuses on the pathophysiology and molecular aspects of common cancer types. Currently, the available chemotherapeutic drugs, also known as combination chemotherapy, are associated with numerous adverse effects, resulting in the search for herbal-based alternatives that attenuate resistance due to cancer therapy and exert chemo-protective actions. To provide new insights, this review updated the list of key compounds that may enhance the efficacy of cancer treatment.

Approaches to the Management of Metastatic Adenoid Cystic Carcinoma

High rates of recurrence and distant metastasis are a foremost challenge in the management of adenoid cystic carcinoma (ACC), occurring in approximately 40% of all ACC patients. Despite the morbidity and mortality resulting from recurrent/metastatic (R/M) disease, there are no FDA-approved systemic agents for these patients. In this review, we summarize pertinent ACC pathophysiology and its implications for different systemic treatment regimens in R/M ACC. We review the evidence for the most widely used systemic agents - cytotoxic chemotherapy and tyrosine kinase inhibitors (TKIs) targeting VEGFR - in addition to immune checkpoint inhibitors and non-TKI biologic agents. Exciting emerging targets for R/M ACC, including inhibitors of Notch signaling, stemness, PRMT5, and Axl, are also discussed. Lastly, we review local therapies for small-volume lung disease in patients with oligometastatic ACC, specifically pulmonary metastasectomy and stereotactic body radiation therapy (SBRT). Future development of targeted molecular agents which exploit the underlying biology of this disease may yield novel therapeutic options to improve clinical outcomes in patients with R/M ACC.

Single-cell transcriptomic analysis of the tumor ecosystem of adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a malignant tumor that originates from exocrine gland epithelial cells. We profiled the transcriptomes of 49,948 cells from paracarcinoma and carcinoma tissues of three patients using single-cell RNA sequencing. Three main types of the epithelial cells were identified into myoepithelial-like cells, intercalated duct-like cells, and duct-like cells by marker genes. And part of intercalated duct-like cells with special copy number variations which altered with MYB family gene and EN1 transcriptomes were identified as premalignant cells. Developmental pseudo-time analysis showed that the premalignant cells eventually transformed into malignant cells. Furthermore, MYB and MYBL1 were found to belong to two different gene modules and were expressed in a mutually exclusive manner. The two gene modules drove ACC progression into different directions. Our findings provide novel evidence to explain the high recurrence rate of ACC and its characteristic biological behavior.

Adenoid Cystic Carcinoma (ACC) Infiltrating the Skull Base: A Systematic Review of Clinical Characteristics and Management Strategies

BACKGROUND/AIM

To systematically review the patient characteristics and management approaches of adenoid cystic carcinoma (ACC) infiltrating the skull base.

MATERIALS AND METHODS

According to PRISMA guidelines, PubMed, Scopus, and Cochrane were searched to retrieve studies reporting management protocols and survival outcomes of patients with skull base ACCs. Patient characteristics, management strategies, and outcomes were investigated.

RESULTS

The review encompassed 17 studies involving 171 patients, with a female predominance (57.9%) and a mean age of 49±7.12 years. ACCs mostly infiltrated the paranasal sinus (22.2%), cavernous sinus (8.8%), and nasopharynx (7.1%). Perineural invasion was reported in 6.4% of cases. Facial pain, nasal obstruction, and facial paresthesia were the most common symptoms. Surgical resection (45.6%) was favored over biopsy (12.2%). Employing the free flap technique (4.7%), surgical reconstruction of the bony defect after resection was performed using abdominal and anterior thigh muscle grafts in 1.8% of patients each. As adjuvant management, 22.8% of cases had radiotherapy and 14.6% received chemotherapy. Recurrence of skull base ACCs occurred in 26.9% of cases during a mean follow up-time of 30.8±1.8 months.

CONCLUSION

Skull base ACCs pose a surgical challenge mainly due to their proximity to critical neurovascular structures and aggressive behavior. Surgical resection and radiotherapy are shown to be safe and effective treatment modalities. The dismal prognosis and limited data on non-surgical strategies highlight the need for further evaluation of the current management paradigm and upraising innovative therapies to improve patient mortality and quality of life.

Sphk1 promotes salivary adenoid cystic carcinoma progression via PI3K/Akt signaling

The progression of salivary adenoid cystic carcinoma (SACC) is closely related to abnormal gene expression. Herein, the role of Sphk1 in SACC was explored. Sphk1 was overexpressed in SACC tissues. In SACC cell lines, Sphk1 induced cell proliferation, inhibited apoptosis, and promoted cell migration. Moreover, Sphk1 overexpression induced up-regulation of the PI3K protein level and AKT phosphorylation level. Rescue assays further showed that activation of the Sphk1 /PI3K/Akt pathway affected various biological functions of SACC cells. Together, these findings suggested that Sphk1 promotes salivary tumorigenesis by activating the PI3K/ Akt pathway, which may provide novel intervention targets for SACC treatment.

The immunophenotype of epithelial to mesenchymal transition inducing transcription factors in salivary gland adenoid cystic carcinomas

Adenoid cystic carcinoma (ACC) is the second most common malignant salivary glands neoplasms with a controversial biological behavior. Even though these tumors grow slowly, they have increased potential for recurrence and distant metastasis. In order to elucidate this behavior, our study aimed to investigate the immunoexpression in such tumors of the most important transcriptional factors [Twist, Snail, Slug, and zinc finger E-box binding homeobox 1 (ZEB1)] involved in the epithelial–mesenchymal transition process. The highest level of expression was recorded for Twist, present in all the investigated cases, followed by the Slug and Snail, while no tumor parenchyma reactivity was noticed for the ZEB1 factor. There were tumor reactivity differences regarding topography, histopathological variant, and nerve and lymph node invasion status. Thus, tumors developed from the intraoral minor salivary glands, with solid pattern, perineural invasion, locally aggressive and with lymph node metastasis were the most reactive. Therefore, these transcription factors could be useful as prognostic biomarkers and efficient therapeutic targets in such salivary malignancies.

Multicentre clinicopathological study of adenoid cystic carcinoma: A report of 296 cases

Aims

Adenoid cystic carcinoma (ACC) is a distinctive tumour. Limited studies involving a large population have reported multicentre systematic analyses of the clinical, pathological and immunohistochemical (IHC) features of ACC as well as the potential role of IHC markers in the prognosis of ACC.

Methods and Results

The clinical, histopathological and IHC data of 296 cases obtained from two tertiary hospitals were analysed. The age at onset ranged from 12 to 87 years with a median age of 52 years. The male‐to‐female ratio was 1:1.3. Patients with ACC arising from the lacrimal gland were younger than those with tumours arising from other sites. Patients with tumours in the extra auditory canal and nasopharynx were older than those with tumours in other locations. Histopathologically, solid type ACC was the most frequent in the nasal cavity and paranasal sinus (6/51) group. Tumours arising from the oral cavity most commonly showed perineural invasion (10/60) and margin positivity (11/60). IHC analyses showed that CK8/18, CK7, CK14, epithelial membrane antigen and CD117 were expressed in 35/35 (100%), 87/88 (98.8%), 26/27 (96.2%), 42/43 (97.6%) and 113/120 (94.1%) patients, respectively. CK5/6, P63, smooth muscle actin, calponin and S100 were positively expressed in 73/73 (100%), 111/124 (89.5%), 38/43 (88.3%), 41/50 (82.0%) and 61/92 (66.3%) cases, respectively. S100 proteins were expressed in 54 (54/77) primary cases and two (2/9) metastatic cases (p = 0.013).

Conclusions

ACC is a distinctive tumour that mainly affects middle‐aged and elderly individuals, with a mild female predominance. Loss of expression of S100 proteins may be a poor prognostic factor associated with metastasis.

MYB-activated models for testing therapeutic agents in adenoid cystic carcinoma

OBJECTIVE

There are no effective systemic therapies for adenoid cystic cancer (ACC) and lack of tumor lines and mouse models have hindered drug development.We aim to develop MYB-activated models for testing new therapeutic agents.

MATERIALS AND METHODS

We studied new ACC patient-derived xenograft (PDX) models and generated a matched cell line from one patient. In addition, we generated a genetically-engineered MYB-NFIB mouse model (GEMM) that was crossed with Ink4a^+/-/Arf^+/- mice to study tumor spectrum and obtain tumor lines. Using human and murine ACC-like tumor lines, we analyzed MYB expression by RNA-Seq and immunoblot and tested efficacy of new MYB inhibitors.

RESULTS

We detected MYB-NFIB transcripts in both UFH1 and UFH2 PDX and observed tumor inhibition by MYB depletion using shRNA in vivo. We observed rapid loss of MYB expression when we cultured UFH1 in vitro, but were able to generate a UFH2 tumor cell line that retained MYB expression for 6 months. RNA-Seq expression detected an ACC-like mRNA signature in PDX samples and we confirmed an identical KMT2A/MLL variant in UFH2 PDX, matched cell line, and primary biopsy. Although the predominant phenotype of the MYB-NFIB GEMM was B-cell leukemia, we also generated a MYB-activated ACC-like mammary tumor cell line. We observed tumor inhibition using a novel MYB peptidomimetic in both human and murine tumor models.

CONCLUSIONS

We generated and studied new murine and human MYB-activated tumor samples and detected growth inhibition with MYB peptidomimetics. These data provide tools to define treatment strategies for patients with advanced MYB-activated ACC.

Zebrafish blastomere screen identifies retinoic acid suppression of MYB in adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a salivary gland malignancy that has no effective therapy and is caused by translocations involving MYB. A zebrafish chemical genetic screen identifies the retinoic acid class of compounds as potential MYB-inhibitory agents. Preclinical ACC mouse xenotransplantation models confirm the in vivo efficacy of retinoic acid, which represents a potential therapy for ACC.

Pluripotent cells have been used to probe developmental pathways that are involved in genetic diseases and oncogenic events. To find new therapies that would target MYB-driven tumors, we developed a pluripotent zebrafish blastomere culture system. We performed a chemical genetic screen and identified retinoic acid agonists as suppressors of c-myb expression. Retinoic acid treatment also decreased c-myb gene expression in human leukemia cells. Translocations that drive overexpression of the oncogenic transcription factor MYB are molecular hallmarks of adenoid cystic carcinoma (ACC), a malignant salivary gland tumor with no effective therapy. Retinoic acid agonists inhibited tumor growth in vivo in ACC patient–derived xenograft models and decreased MYB binding at translocated enhancers, thereby potentially diminishing the MYB positive feedback loop driving ACC. Our findings establish the zebrafish pluripotent cell culture system as a method to identify modulators of tumor formation, particularly establishing retinoic acid as a potential new effective therapy for ACC.

MYB fusions and CD markers as tools for authentication and purification of cancer stem cells from salivary adenoid cystic carcinoma

Cancer stem cells (CSC) are considered the major cause of aggressive tumor behavior, recurrence, metastases, and resistance to radiation, making them an attractive therapeutic target. However, isolation of CSC from tumor tissue and their characterization are challenging due to uncertainty about their molecular markers and conditions for their propagation. Adenoid cystic carcinoma (ACC), which arises predominantly in the salivary glands, is a slow-growing but relentless tumor that frequently invades nerves and metastasizes. New effective treatment approaches for ACC have not emerged over the last 40years. Previously, based on a highly conserved SOX10 gene signature that we identified in the majority of ACC tumors, we suggested the existence in ACC of SOX10+ cells with neural stem properties and corroborated this hypothesis via isolation from ACC tissue a novel population of CSC, termed ACC-CSC. These cells activated NOTCH1 signaling and co-expressed SOX10 and other ACC-intrinsic neural crest stem cell markers with CD133, a CSC cell surface marker, suggesting that ACC is driven by a previously uncharacterized population of SOX10+/CD133+ cells with neural stem cell properties. Here, we authenticated ACC identity of our primary cultures by demonstrating that most of them harbor MYB-NFIB fusions, which are found in 86% of ACC. We demonstrated using CyTOF, a novel mass cytometry technology, that these cells express high β-catenin and STAT3 levels and are marked by CD24 and CD44. Finally, to streamline development of ACC cell lines, we developed RT-PCR tests for distinguishing mouse and human cells and used immunomagnetic cell sorting to eliminate mouse cells from long-term cell cultures. Overall, this study describes a new population of CSC that activates signaling pathways associated with poor prognosis, validates their ACC identity, and optimizes approaches that can be used for purification of ACC-CSC and generation of cell lines.

Expression Profiling of Clinical Specimens Supports the Existence of Neural Progenitor-Like Stem Cells in Basal Breast Cancers

BACKGROUND

We previously characterized in salivary adenoid cystic carcinoma (ACC) a novel population of cancer stem cells (CSCs) marked by coexpression of 2 stemness genes, sex-determining region Y (SRY)-related HMG box-containing factor 10 (SOX10) and CD133. We also reported that in ACC and basal-like breast carcinoma (BBC), a triple-negative breast cancer subtype, expression of SOX10 similarly demarcates a highly conserved gene signature enriched with neural stem cell genes. On the basis of these findings, we hypothesized that BBC might be likewise driven by SOX10-positive (SOX10⁺)/CD133⁺ cells with neural stem cell properties.

MATERIALS AND METHODS

To validate our hypothesis on clinical data, we used a novel approach to meta-analysis that merges gene expression data from independent breast cancer studies and ranks genes according to statistical significance of their coexpression with the gene of interest. Genes that showed strong association with CD133/PROM1 as well as SOX10 were validated across different platforms and data sets and analyzed for enrichment with genes involved in neurogenesis.

RESULTS

We identified in clinical breast cancer data sets a highly conserved SOX10/PROM1 gene signature that contains neural stem cell markers common for Schwann cells, ACC, BBC, and melanoma. Identification of tripartite motif-containing 2 (TRIM2), TRIM29, MPZL2, potassium calcium-activated channel subfamily N member 4 (KCNN4), and V-set domain containing T cell activation inhibitor 1 (VTCN1)/B7 homolog 4 (B7H4) within this signature provides insight into molecular mechanisms of CSC maintenance.

CONCLUSION

Our results suggest that BBC is driven by SOX10⁺/CD133⁺ cells that express neural stem cell-specific markers and share molecular similarities with CSCs of neural crest origin. Our study provides clinically relevant information on possible drivers of these cells that might facilitate development of CSC-targeting therapies against this cancer distinguished with poor prognosis and resistance to conventional therapies.