Osteopontin-c isoform levels are associated with SR and hnRNP differential expression in ovarian cancer cell lines

Abstract

Osteopontin-c splicing isoform activates ovarian cancer progression features. Imbalanced expression of splicing factors from serine/arginine -rich and heterogeneous ribonucleoproteins families has been correlated with the generation of oncogenic splicing isoforms. Our goal was to investigate whether there is any association between the transcriptional patterns of these splicing factors in ovarian cells and osteopontin-c expression levels. We also aimed to investigate the occurrence of these splicing factors binding sites inside osteopontin exon 4 and adjacent introns. To test associations between osteopontin-c and splicing factors expression patterns, we used an in vitro model in which OVCAR-3 cells overexpressing osteopontin-c (OVCAR-3/OPNc) presented higher transcriptional levels of osteopontin-c than two other ovarian carcinoma cells (TOV-112D, SKOV-3) and ovarian non-tumoral cell lines (IOSE 364 and IOSE 385). The transcriptional levels of osteopontin-c, serine/arginine-rich, and hnRNP factors were evaluated using real-time polymerase chain reaction. Human Splice Finder software was used to search for putative splicing factor binding sites in osteopontin genomic regions. OVCAR-3/OPNc cells presented higher transcriptional levels of hnRNP than serine/arginine-rich when compared to TOV-112D, SKOV-3, and IOSE cells. TOV-112D and SKOV-3 cells also overexpressed hnRNP in relation to serine/arginine-rich transcripts. Putative binding sites for these splicing factors have been predicted on osteopontin exon 4 and their upstream and downstream intronic regions. Our data showed that higher osteopontin-c expression levels are associated with a predominance of hnRNP in relation to serine/arginine-rich transcripts and that osteopontin exon 4 and adjacent intronic sequences contain predicted binding sites for some of these tested splicing factors. In conclusion, differential expression of these splicing factors in ovarian cancer cells could be one of the putative mechanisms leading to aberrant splicing of the osteopontin primary transcript. Future work, aiming to control ovarian cancer progression by downregulating osteopontin-c levels, could include strategies that also regulate heterogeneous ribonucleoproteins and serine/arginine-rich expression levels in order to modulate osteopontin splicing.

Assessment of the frequency of mitochondrial tRNA variants in patients with ovarian cancer

“…OC was the result of the interaction of multiple genetic and environmental factors, many reports showed that multiples genes may be involved in the pathogenesis of this disease [12][13][14]. However, these genes were mainly nuclear genes; little was known the role of mitochondrial dysfunction in OC.…”

Predictive Biomarkers and Patient Outcome in Platinum-Resistant (PLD-Treated) Ovarian Cancer

“…OPN primary transcript is subject to alternative splicing and, in addition to other post-transcriptional and post-translational OPN variants, total OPN (the sum of all OPN variants, which we named herein as OPN) has been widely studied in cancer cells [ 27 ]. Among OPN splice variants, Osteopontin-c (OPN-c) splicing isoform seems to activate OC progression features [ 28 ]. The role of OPN and OPN-c in OC has been intensively studied in two recent published meta-analyses [ 29 , 30 ], indicating that it may be a potential diagnostic and prognostic biomarker.…”