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Phenotypic consequences of SLC25A40-ABCB1 fusions beyond drug resistance in High Grade Serous Ovarian Cancer

ABSTRACT: Purpose: Our laboratory recently identified the most common mechanism of acquired drug resistance in High Grade Serous Ovarian Cancer (HGSOC) to date, SLC25A40-ABCB1 fusions. The primary aim of this study was to examine the transcriptional profile of drug resistant fusion-positive SLC25A40-ABCB1 fusion positive cells. Single cell fusion-positive and negative clones were derived from the human HGSOC cell line AOCS-18.5 Methods: Three independent replicates of RNA was collected from five SLC25A40-ABCB1 fusion-negative AOCS 18.5 clones (B,C, D,E,F) and five SLC25A40-ABCB1 fusion-positive AOCS 18.5 clones (8,9,13, 15B, 18B) and submitted for NextSeq 100bp paired-end, polyA RNA-sequencing. Cells were collected 48-72hrs post seeding. 20 million paired end reads per sample were generated. Reads were mapped to the human reference GRCh37.92 using the STAR two pass method (v2.6.0b). Counts were generated on the ensemble release GRCh37.92 GTF annotation using HTSeq (v0.10.0). Counts were normalized to logged TMM values using edgeR (v3.28.1). TPM expression values were also generated. Differential gene expression analysis was performed using DESeq2 (v1.26.0) on the raw counts. In all, 3333 genes were significantly upregulated (>1.5 log2 fold change, p-adj<0.1) in fusion-positive lines, with 1751 genes significantly downregulated Conclusions: Using a stringent cut-off of >2.0 fold change (n=2238 differentially expressed genes), Metascape pathway analysis revealed that the most significantly enriched pathways in fusion-positive clones included the NABA matrisome associated pathway (160/751 genes, 7.24%), followed by external encapsulating structure organization (102/398 genes, 4.62%) and regulation of cell adhesion (139/734 genes, 6.29%).

ORGANISM(S): Homo sapiens

PROVIDER: GSE183210 | GEO | 2021/09/03

REPOSITORIES: GEO

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Project description:Hepatosplenic T-cell lymphoma (HSTL) is an aggressive lymphoma cytogenetically characterized by isochromosome 7q M-BM- [i(7)(q10)], of which the molecular consequences remain unknown. We report here results of an integrative genomic and transcriptomic (expression microarray and RNA-sequencing) study of six HSTL cases with i(7)(q10) and three cases with ring 7 M-BM- [r(7)], a rare variant aberration. Using high resolution array CGH, we prove that HSTL is characterized by the common loss of a 34.88 Mb region at 7p22.1p14.1 (3506316-38406226 bp) and duplication/amplification of a 38.77 Mb region at 7q22.11q31.1 (86259620-124892276 bp). Our data indicate that i(7)(q10)/r(7)-associated loss of 7p22.1p14.1 is a critical event in the development of HSTL, while gain of 7q sequences drives progression of the disease and underlies its intrinsic chemoresistance. Loss of 7p22.1p14.1 does not target a postulated tumor suppressor gene but unexpectedly enhances the expression of CHN2 from the remaining 7p allele, resulting in dysregulation of a pathway involving RAC1 and NFATC2 with a cell proliferation response. Gain of 7q leads to increased expression of critical genes, including RUNDC3B, PPP1R9A and ABCB1, a known multidrug resistance gene. RNA-sequencing did not identify any additional recurrent mutations or fusion, suggesting that i(7)(q10) is the only driver event in this tumor. Our study confirms the previously described gene expression profile of HSTL and identifies a set of 24 genes, including three located on chromosome 7 (CHN2, ABCB1 and PPP1R9A), distinguishing HSTL from other malignancies The fastq files of all samples were mapped to the reference human genome (assembly GRCh37.68). The mapping was performed allowing detection of insertions and deletions (indels). The mapped reads were used to calculate read counts and FPKM (Fragment Per Kilobase of exon model per Million of mapped read) per gene. The DESeq algorithm was applied to identify differentially expressed genes. The mapped reads were used to predict mutations and gene fusions.

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Phenotypic consequences of SLC25A40-ABCB1 fusions beyond drug resistance in High Grade Serous Ovarian Cancer

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