A personalized multigenic Drosophila model was used to assess possible therapeutic options for a patient with advanced metastatic adenoid cystic carcinoma (ACC). Assessment of tumorous tissue identified two changes common to most cases of ACC: truncation/fusion of MYB due to a translocation, and elevated NOTCH1 expression/activity. Other genomic changes in the tumorous tissue were judged unlikely to be pathogenic. However, several heterozygous germline variants likely to have deleterious effects were identified, affecting the genes FAT4, FAT1, FAT3, and ERCC2.
A transgenic fly model was developed that combined an activated form of the Drosophila ortholog of NOTCH1 (N), UAS-RNAi directed against orthologs of FAT4 (ft), FAT1/3 (kug), and ERCC2 (Xpd), plus a UAS construct carrying a truncated form of the human MYB gene (Hsap\MYB). Use of a GAL4 driver that resulted in substantial lethality allowed for an efficient robotics-based screen for suppression of lethality; extensive drug screening was performed, with an emphasis on multi-drug combinations. A 3-drug combination was identified and administered to the patient over 12 months, resulting in stabilization of the disease. After 12 months, resistance to the treatment developed, which was associated with new genomic amplifications and deletions in tumorous tissues.
[updated Mar. 2021 by FlyBase; FBrf0222196]
Adenoid cystic carcinoma (ACC) is a relatively rare form of cancer that most commonly develops in the salivary glands or other regions of the head and neck. ACC can occur in other parts of the body, such as the breast, skin, cervix in females, prostate gland in males, and various other areas. [NORD: Adenoid Cystic Carcinoma; 2021.03.29]
A recurrent t(6;9)(q22–23;p23–24) translocation in ACC consistently results in a fusion of the MYB oncogene to the transcription factor gene NFIB (Stenman, 2013; pubmed:23821214).
ACC tumors are characterized by a distinctive histological pattern of abnormal "nests" or cords of certain cells (epithelial cells) that surround and/or infiltrate ducts or glandular structures within the affected organ. These structures are typically filled with a mucous-like material or contain abnormal fibrous membranes. [NORD: Adenoid Cystic Carcinoma; 2021.03.29]
MYB belongs to a family of proteins that functions as transcriptional regulators. The MYB protein contains three functional key domains, an N-terminal DNA-binding domain, a centrally located transcription activation domain, and a C-terminal negative regulatory domain involved in transcriptional repression (Stenman, 2013; pubmed:23821214).
In the MYB-NFIB fusion oncogene, which is highly overexpressed in ACC, the 3′-part of MYB, including target sites for negatively regulating microRNAs, is replaced by one or more of the last coding exons of NFIB. The predicted MYB-NFIB fusion proteins retain the DNA-binding and transactivation domains of MYB, and are therefore expected to activate MYB target genes (Stenman, 2013; pubmed:23821214).
High-scoring ortholog of human ERCC2 (1 Drosophila to 1 human).
Moderate- to high-scoring ortholog of human NOTCH1, NOTCH2, NOTCH3 (1 Drosophila to multiple human).
High-scoring ortholog of human FAT4 (1 Drosophila to 1 human).
High-scoring ortholog of human FAT1, FAT2, FAT3 (1 Drosophila to multiple human).