Transcriptome sequencing of human breast cancer reveals aberrant intronic transcription in amplicons and dysregulation of alternative splicing with major therapeutic implications

Analysis of RANK-c interaction partners identifies TRAF3 as a critical regulator of breast cancer aggressiveness

Breast cancer is a highly heterogeneous disease both at the histological and molecular levels. We have previously shown that RANK-c is a regulator of NF-κB signaling and exerts a suppressive effect on aggressive properties of ER negative breast cancer cells, while there is an opposite effect on ER positive cell lines. In order to identify molecular determinants that govern the opposing function of RANK-c in breast cancer cells we employed the two cell lines with the highest degree of phenotypic divergence upon RANK-c-expression (SKBR3 and BT474) and identified proteins that interact with RANK-c by affinity-enrichment mass spectrometry (AE-MS) analysis. Annotating enriched proteins with NF-κB signaling pathway revealed TRAF3 as an interacting partner of RANK-c in SKBR3 cell protein lysates, but not in BT474 breast cancer cells in which RANK-c induces cell aggressiveness. To determine the role of TRAF3 in the phenotype of BT474-RANK-c cells, we reconstructed the TRAF3/RANK-c interaction both in parental BT474 and RANK-c expressing cells and tested for aggressive properties through colony formation, migration and invasion assays. TRAF3 forced expression was able to reverse BT474 phenotypic changes imposed by RANK-c, rendering cells less aggressive. Finally, TRAF3 gene expression data and TRAF3 immunohistochemical (IHC) analysis on breast cancer samples indicated that TRAF3 expression correlates with Overall Survival (OS), Recurrence Free Survival (RFS) and several clinicopathological parameters (histological grade, proliferation index) of breast cancer disease.

Dysregulation of splicing variants and spliceosome components in breast cancer

The dysregulation of the splicing process has emerged as a novel hallmark of metabolic and tumor pathologies. In breast cancer (BCa), which represents the most diagnosed cancer type among women worldwide, the generation and/or dysregulation of several oncogenic splicing variants have been described. This is the case of the splicing variants of HER2, ER, BRCA1, or the recently identified by our group, In1-ghrelin and SST5TMD4, which exhibit oncogenic roles, increasing the malignancy, poor prognosis, and resistance to treatment of BCa. This altered expression of oncogenic splicing variants has been closely linked with the dysregulation of the elements belonging to the macromolecular machinery that controls the splicing process (spliceosome components and the associated splicing factors). In this review, we compile the current knowledge demonstrating the altered expression of splicing variants and spliceosomal components in BCa, showing the existence of a growing body of evidence supporting the close implication of the alteration in the splicing process in mammary tumorigenesis.

A Single-Subject Method to Detect Pathways Enriched With Alternatively Spliced Genes

RNA-Sequencing data offers an opportunity to enable precision medicine, but most methods rely on gene expression alone. To date, no methodology exists to identify and interpret alternative splicing patterns within pathways for an individual patient. This study develops methodology and conducts computational experiments to test the hypothesis that pathway aggregation of subject-specific alternatively spliced genes (ASGs) can inform upon disease mechanisms and predict survival. We propose the N-of-1-pathways Alternatively Spliced (N1PAS) method that takes an individual patient’s paired-sample RNA-Seq isoform expression data (e.g., tumor vs. non-tumor, before-treatment vs. during-therapy) and pathway annotations as inputs. N1PAS quantifies the degree of alternative splicing via Hellinger distances followed by two-stage clustering to determine pathway enrichment. We provide a clinically relevant “odds ratio” along with statistical significance to quantify pathway enrichment. We validate our method in clinical samples and find that our method selects relevant pathways (p < 0.05 in 4/6 data sets). Extensive Monte Carlo studies show N1PAS powerfully detects pathway enrichment of ASGs while adequately controlling false discovery rates. Importantly, our studies also unveil highly heterogeneous single-subject alternative splicing patterns that cohort-based approaches overlook. Finally, we apply our patient-specific results to predict cancer survival (FDR < 20%) while providing diagnostics in pursuit of translating transcriptome data into clinically actionable information. Software available at https://github.com/grizant/n1pas/tree/master.

RANK-c attenuates aggressive properties of ER-negative breast cancer by inhibiting NF-κB activation and EGFR signaling

The RANK/RANKL axis emerges as a key regulator of breast cancer initiation, progression, and metastasis. RANK-c is a RANK receptor isoform produced through alternative splicing of the TNFRSF11A (RANK) gene and a dominant-negative regulator of RANK-induced nuclear factor-κB (NF-κB) activation. Here we report that RANK-c transcript is expressed in 3.2% of cases in The Cancer Genome Atlas breast cancer cohort evenly between ER-positive and ER-negative cases. Nevertheless, the ratio of RANK to RANK-c (RANK/RANK-c) is increased in ER-negative breast cancer cell lines compared to ER-positive breast cancer cell lines. In addition, forced expression of RANK-c in ER-negative breast cancer cell lines inhibited stimuli-induced NF-κB activation and attenuated migration, invasion, colony formation, and adhesion of cancer cells. Further, RANK-c expression in MDA-MB-231 cells inhibited lung metastasis and colonization in vivo. The RANK-c-mediated inhibition of cancer cell aggressiveness and nuclear factor-κB (NF-κB) activation in breast cancer cells seems to rely on a RANK-c/TNF receptor-associated factor-2 (TRAF2) protein interaction. This was further confirmed by a mutated RANK-c that is unable to interact with TRAF2 and abolishes the ability to attenuate NF-κB activation, migration, and invasion. Additional protein interaction characterization revealed epidermal growth factor receptor (EGFR) as a novel interacting partner for RANK-c in breast cancer cells with a negative effect on EGFR phosphorylation and EGF-dependent downstream signaling pathway activation. Our findings further elucidate the complex molecular biology of the RANKL/RANK system in breast cancer and provide preliminary data for RANK-c as a possible marker for disease progression and aggressiveness.

Androgen and estrogen sensitivity of bird song: a comparative view on gene regulatory levels

Singing of songbirds is sensitive to testosterone and its androgenic and estrogenic metabolites in a species-specific way. The hormonal effects on song pattern are likely mediated by androgen receptors (AR) and estrogen receptor alpha (ERα), ligand activated transcription factors that are expressed in neurons of various areas of the songbirds' vocal control circuit. The distribution of AR in this circuit is rather similar between species while that of ERα is species variant and concerns a key vocal control area, the HVC (proper name). We discuss the regulation of the expression of the cognate AR and ERα and putative splice variants. In particular, we suggest that transcription factor binding sites in the promoter of these receptors differ between bird species. Further, we suggest that AR- and ERα-dependent gene regulation in vocal areas differs between species due to species-specific DNA binding sites of putative target genes that are required for the transcriptional activity of the receptors. We suggest that species differences in the distribution of AR and ERα in vocal areas and in the genomic sensitivity to these receptors contribute to species-specific hormonal regulation of the song.

LncRNA SNHG1 enhances cell proliferation, migration, and invasion in cervical cancer

OBJECTIVE

This study investigated the effects of lncRNA SNHG1 on the proliferation, migration, and invasiveness of cervical cancer cells.

METHODS

Three pairs of cervical cancer tissue samples and their corresponding adjacent samples were analyzed using Human LncRNA Microarray V3.0 chip for differential analysis. The expression of SNHG1 in cervical cancer cell lines was verified by qRT-PCR. CCK8 assays and colony formation assays were used to study the changes in cell proliferation. Cell migration and Transwell assays were used to study changes in cell migration and invasiveness.

RESULTS

SNHG1 was highly expressed in cervical cancer tissues and cervical cancer cell lines. SNHG1 siRNA could knock-down the expression level of SNHG1 in cervical cancer cell lines HeLa and C33-A. After knock-down of SNHG1, cell proliferation and migration as well as invasiveness in HeLa and C-33A cells decreased.

CONCLUSION

LncRNA SNHG1 promotes the development of cervical cancer cells.