Specimens and Models
The basic building blocks of research are widely available for common cancers. However, a concerted effort must be undertaken to develop, maintain and distribute tumor specimens, cell lines and mouse models for rare cancers. This page is intended to facilitate that process for ACC. Researchers may contact ACCRF for assistance in accessing the resources described below.
The Salivary Gland Tumor Biorepository (SGTB) collects, maintains and distributes biospecimens and cell lines, and provides qualified researchers with materials for basic and translational research on salivary gland tumors. The SGTB is centralized at M.D. Anderson and includes Johns Hopkins, Rhode Island Hospital, the University of Mississippi, the University of Pittsburgh and the University of Virginia as consortium members.
The SGTB website provides access to an inventory of available specimens as well as application instructions for any interested researcher globally. The SGTB operates under a contract with the National Institute of Dental and Craniofacial Research (NIDCR). ACCRF Executive Director Jeff Kaufman serves on the Tissue Utilization Committee.
At the moment, there are no validated ACC cell lines that have not been immortalized. Dr. Adel El-Naggar developed an hTERT-immortalized cell line as a surrogate for functional studies, as described in an Oral Oncology article. Two HPV-immortalized cell lines were developed by Lurdes Quiemado; they are described in an International Journal of Cancer article. These three cell lines lost in later passages the translocations that were identified in the primary tumors from which they were derived.
Several years ago, there were many non-immortalized cell lines purported to be derived from ACC tumors. However, ACCRF and its affiliated investigators came to realize through STR analysis that the available cell lines were cross-contaminated and/or misidentified. ACCRF sounded an early warning that was later confirmed by Dr. Osamu Tetsu in a PLoS One article. Batches of ACC2, ACC3, ACCM, ACCNS, ACCS and CAC2 were all found to be misidentified. There may be batches that have not been cross-contaminated, but they have not been made available to ACCRF-affiliated researchers nor have the primary tumor samples from which they were derived. One cell line, SACC-83, was found to be genotypically distinct but, given the issues experienced with the other cell lines, would require further scrutiny before being considered a valid ACC model.
In order to address the uncertainty across the research community about how best to validate ACC cell lines, ACCRF convened in April 2014 a working group of four world experts in salivary gland cancer pathology. The ACC Cell Line Working Group drafted a document delineating the validation criteria for ACC cell lines based on necessary attributes, highly desirable attributes and other desirable attributes. The document is available here.
ACCRF is supporting several attempts to develop new ACC cell lines. They will be made available to the research community once they are validated by multiple investigators and quality controls ensure that the problems of the past won’t recur.
Patient-Derived Xenograft (PDX) Models
ACCRF has supported the development of ACC PDX models to assist researchers in developing cell lines, studying the disease biology and screening drugs. Most of the models, now numbering more than 20, have been created at the University of Virginia, although a few additional models are available from other institutions. Approximately 12 of the ACC PDX models are maintained at South Texas Accelerated Research Therapeutics (START), a contract research organization providing an open drug screening platform under a contractual agreement with ACCRF. Academic and industry researchers may expolore the efficacy and toxicity of their drugs in ACC preclinical models. ACCRF does not seek to obtain intellectual property from collaborators using the platform.
The PDX models were first published in a Laboratory Investigation article. They maintain the histology and gene expression patterns of the primary tumors from which they were derived. Extensive characterization data is available from the Databases webpage.
Researchers interested in accessing the PDX models may contact ACCRF.
Transgenic Mouse Models
The discovery of the recurrent t(6;9) translocation in ACC that often results in the MYB-NFIB fusion oncogene has opened up the possibility of developing a transgenic model of ACC. ACCRF is supporting such efforts at the Dana-Farber Cancer Institute and the University of Virginia, while NIDCR is supporting another effort at M.D. Anderson. Complementary approaches are being tried with different promoters (MMTV and PSP), variants of the MYB-NFIB fusion and systems for inducing its over-expression.
At the moment, these models are in development and are not available.
Many MYB antibodies are commercially available and some perform well for immunohistochemistry and western blotting. However, researchers have struggled to find MYB antibodies that bind with sufficient affinity for use in chromatin immunoprecipitation sequencing (ChIP-seq), an important method for identifying which portions of DNA are bound by a given protein and, therefore, may be downstream targets.
As part of their ACCRF-funded project to study the chromatin landscape of MYB in ACC, Drs. Bradley Bernstein and Birgit Knoechel tested many MYB antibodies and found only one that worked on their ChIP-seq platform. Unfortunately, the antibody binds to a portion of the MYB protein (the C-terminus) that is lost in about 70% of ACC cases due to MYB’s fusion with NFIB or another gene. Accordingly, Bethyl Labs was approached by Dr. Bernstein and ACCRF to develop new rabbit polyclonal antibodies that bind to a region within the first 7 exons of MYB as they are almost always conserved in MYB-fusion-positive ACCs.
Bethyl Labs recently tested and made available five new MYB antibodies at https://www.bethyl.com/category/c-Myb_3/. One of the antibodies (catalog number A304-136A) performed well in ChIP-seq experiments and it recognizes an epitope coded within exon 6 of MYB, making it appropriate for studying most ACCs with MYB fusions.
Prior to the development of Bethyl Labs’ new antibodies, Dr. Knoechel kindly provided a summary of commercially available MYB antibodies. Many antibodies offered by different companies are actually the same product (depicted by the same color font on the second page of the summary).