Abstract 5461: Tacc1 is amplified in a wide range of pediatric malignancy
Authors: Rajan Aditya , Singh Sharda P. , Chavali Santhosh , Bose Chhanda , Tonk Vijay , Awasthi Sanjay 
Published: September 2020

Abstract
While fluorescence in situ hybridization (FISH) is traditionally used to detect copy number variations (CNV) at known pathogenic chromosomal loci, the comparative genomic hybridization (CGH) microarray is a platform capable of simultaneous detection of CNVs at thousands of loci. CGH microarrays are typically used to assess loci of known prognostic significance; however loci variants of uncertain significance (VUS) are frequently present. To identify potentially actionable targets, we retrospectively analyzed VUS loci from 192 cases of cancer or genetic disorders using CGH data generated for treatment guidance at the Texas Tech University Health Sciences Center Cytogenetics Laboratory, a CLIA-certified Children's Oncology Group reference lab serving the West Texas population. The majority of cases were of pediatric malignancies, though some adult cancers and benign hematological diseases were included. Patient DNA was hybridized onto CytoSure Constitution V3 arrays (60k loci), scanned with the Agilent microarray D scanner, and analyzed by CytoSure Interpret Software. TACC1, TM2D2, KAT6A and ADAM32 were knocked down in H358 lung cancer (p53-null), MCF7 (ER+) and MDA-MB-231 (triple-negative) breast cancer, and B16-F0 murine melanoma cell lines using siRNA, followed by evaluation of growth inhibition by MTT assay. Colcemid block was used to evaluate metaphase reduction and chromosomal abnormalities following TACC1 knockdown. We found 794 distinct CNVs, the most frequent being 14q32.22 (112 cases), 14q11.2 (100 cases), 8p11.22 (98 cases), 15q11.1-15q11.2 (83 cases), and 8p23.1 (77 cases). In particular, the 8p11.22 locus was amplified in many pediatric cancers, including acute lymphoblastic leukemia (18 gains/2 losses), lymphoma (6/1), neuroblastoma (5/0), pediatric breast tumors (5/0), and Wilm's tumor (4/0). Linkage of TACC1, TM2D2, KAT6A and ADAM32, all genes residing at the 8p11.22 locus, was indicated by a similar average 5-year overall survival rate (75.3 ± 1.7%, n=253) among patients harboring alterations in these genes in The Cancer Genome Atlas (TCGA) database. Knockdown of TACC1, TM2D2, and KAT6A reduced growth of H358, MCF7, MDA-MB-231, and B16-F0 cells (P &lt; 0.05). ADAM32 depletion inhibited H358, MCF7, and MDA-MB-231 cells (P &lt; 0.05), but not B16-F0 cells. Because TACC1 function is linked to mitosis through the aurora kinases, we subsequently studied metaphase of B16-F0 cells after TACC1 depletion, found an 80% reduction metaphase cells, and increased morphological abnormalities. In summary, we report a high frequency of 8p11.2 gains in our pediatric oncology patients and demonstrate that evaluation of growth inhibition of cancer cells following knockdown of genes at VUS loci may help to identify new cancer therapy targets. These results further suggest that TACC1 could be a target for treating triple negative breast cancer, melanoma, and p53-null lung cancer.
Citation Format: Aditya Rajan, Sharda P. Singh, Santhosh Chavali, Chhanda Bose, Vijay Tonk, Sanjay Awasthi. Tacc1 is amplified in a wide range of pediatric malignancy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5461.