Relevance of ARID1A Mutations in Endometrial Carcinomas

Abstract

Since the Cancer Genome Atlas (TCGA) project identified four distinct groups based on molecular alterations, mutation analyses have been integrated into the characterization of endometrial carcinomas (ECs). ARID1A seems to be the subunit more involved in the loss of function of the SWI/SNF complex in ECs. The aim of this study is to define the relevance of ARID1A alterations in a cohort of EC, studying the possible associations between DNA mutation (genomic level), RNA expression (transcriptomic level), and protein expression (proteomic level). A total of 50 endometrial carcinomas were characterized for ARID1A mutations (using targeted DNA next-generation sequencing-NGS), ARID1A gene expression (using RNAseq and qRT-PCR), and ARID1A protein expression (using immunohistochemistry-IHC). Moreover, we have investigated if ARID1A mutations may alter the protein structure, using the Protein Data Bank sequence. We found a good correlation between ARID1A mutations and protein immunostaining, even if we did not find statistically significant differences in the ARID1A expression levels. In conclusion, our data demonstrated that the molecular characterization of ARID1A should be associated with IHC analysis, mainly in those cases harboring "novel" ARID1A mutations or in those alterations with "uncertain" pathogenic significance.

Keywords: ARID1A; SWI/SNF complex; endometrial cancer; molecular classification; next-generation sequencing.

Figure 1

Immunohistochemical staining for ARID1A. (A) Preserved expression; (B) Loss of expression. Magnification: 200×.

Figure 2

ARID1A expression between wildtype and mutant patients by RNAseq. ^WT: ARID1A wildtype samples; ^MUT: ARID1A mutant samples.

Figure 3

ARID1A expression between wildtype and mutant patients by qRT-PCR. ^WT: ARID1A wildtype samples; ^MUT: ARID1A mutant samples.

Figure 4

Details of ARID1A Leu1100 (A), Asn1705 (B), Arg1833 (C), Arg1906 (D), and Leu2195 (E) and of the neighboring residues in the available structures. In each panel, the wildtype structure and the mutant calculated in silico have been reported on the left and on the right, respectively. ARID1A helices are in blue, while helices and strands from other SWI/SNF subunits are in light blue and in light yellow. The considered residue is in ball-and-stick representation while the residues in the vicinity are in sticks. The atoms are colored according to the atom type. The hydrogen bonds have been highlighted by using yellow dashed lines.