Inhibition of the lncRNA Coded within Transglutaminase 2 Gene Impacts Several Relevant Networks in MCF-7 Breast Cancer Cells

Abstract

Long non-coding RNAs are nucleotide molecules that regulate transcription in numerous cellular processes and are related to the occurrence of many diseases, including cancer. In this regard, we recently discovered a polyadenylated long non-coding RNA (named TG2-lncRNA) encoded within the first intron of the Transglutaminase type 2 gene (TGM2), which is related to tumour proliferation in human cancer cell lines. To better characterize this new biological player, we investigated the effects of its suppression in MCF-7 breast cancer cells, using siRNA treatment and RNA-sequencing. In this way, we found modifications in several networks associated to biological functions relevant for tumorigenesis (apoptosis, chronic inflammation, angiogenesis, immunomodulation, cell mobility, and epithelial–mesenchymal transition) that were originally attributed only to Transglutaminase type 2 protein but that could be regulated also by TG2-lncRNA. Moreover, our experiments strongly suggest the ability of TG2-lncRNA to directly interact with important transcription factors, such as RXRα and TP53, paving the way for several regulatory loops that can potentially influence the phenotypic behaviour of MCF-7 cells. These considerations imply the need to further investigate the relative relevance of the TG2 protein itself and/or other gene products as key regulators in the organization of breast cancer program.

The Motility and Mesenchymal Features of Breast Cancer Cells Correlate with the Levels and Intracellular Localization of Transglutaminase Type 2

“…We analyzed the amount of several factors engaged with the transcriptional control of MDA-MB-231 cells that were cultured in the absence or presence of NC9. On the basis of evidence emerging both from the literature and from experimental research carried out in our laboratory, we have selected the following proteins: Sp1 and RXR were identified as factors of the MDA-MB-231 regulome implicated in invasiveness [ 49 ] and were associated with TG2 expression [ 50 , 51 , 52 ], while RARα, MAX, and YY1 cooperate with a non-coding RNA expressed by the TGM2 gene and are involved in the control of a panel of genes that is associated with TG2 activity in MCF-7 cells [ 53 ]. Additionally, Eukaryotic translation initiation factor 3 β (EIF3β) was recently found to be strongly associated with EMT via the Akt pathway [ 54 ], and as such, c-Myb was controlled by ZEB1 [ 55 ].…”

Biological Implications and Functional Significance of Transglutaminase Type 2 in Nervous System Tumors

“…From the same perspective, the interaction between TG2 and non-coding RNAs in nervous system tumors could be interesting to investigate. Indeed, its potential impact on TG2-related tumorigenic processes emerged in terms of both direct and indirect regulation of TGM2 expression, affecting TG2 functions and tumor-associated processes [69][70][71]155]. On the other hand, therapeutic targeting of the cellular components that promote the disease within its microenvironment may be favorable to enhance the efficacy of standard-of-care treatment.…”

“…The TGM2 gene not only codes for several protein isoforms, but also includes two long non-coding RNAs (lncRNAs): (i) a lncRNA (TG2-lncRNA) within the first intron of the gene, whose expression correlates with TGM2_v1 [69] and (ii) a last exons variant (LEV) containing the last three exons and the 3 ′ -UTR of the gene [70]. Although it has been suggested that lncRNAs have a role in the regulation of TGM2 transcripts in some pathological conditions, this field is thus still open to future investigations [62,[71][72][73].…”