Fyn/heterogeneous nuclear ribonucleoprotein E1 signaling regulates pancreatic cancer metastasis by affecting the alternative splicing of integrin β1

Pancreatic cancer is characterized by a dense desmoplastic reaction in which extracellular matrix proteins accumulate and surround tumor cells. Integrins and their related signaling molecules are associated with progression of pancreatic cancer. In the present study, the association between the metastasis of pancreatic cancer and the expression of hnRNP E1 and integrin β1 was evaluated. In vitro and in vivo experiments were designed to study the mechanism underlying the regulation of integrin β1 splicing by the Fyn/hnRNP E1 spliceosome. Expression of hnRNP E1 and integrin β1A were associated with metastasis of pancreatic cancer. Inhibition of Fyn activity upregulated the expression of P21-activated kinase 1 and promoted the phosphorylation and nuclear localization of hnRNP E1, leading to the construction of a spliceosome complex that affected the alterative splicing of integrin β1. In the hnRNP E1 spliceosome complex, hnRNP A1 and serine/arginine-rich splicing factor 1 were responsible for binding to the pre-mRNA of integrin β1. Suppression of Fyn activity and/or overexpression of hnRNP E1 decreased the metastasis of pancreatic cancer cells. In pancreatic cancer, the present study demonstrated a novel mechanism by which Fyn/hnRNP E1 signaling regulates pancreatic cancer metastasis by affecting the alternative splicing of integrin β1. hnRNP E1 and integrin β1A are associated with the metastasis of pancreatic cancer and may be novel molecular targets for pancreatic cancer treatment.

Tissue Factor: A Conventional or Alternative Target in Cancer Therapy

BACKGROUND

Tissue factor (TF) is an evolutionary conserved glycoprotein that plays an important role in the pathogenesis of cancer. TF is expressed in 2 naturally occurring protein isoforms, membrane-bound full-length (fl)TF and soluble alternatively spliced (as)TF. Both isoforms have been shown to affect a variety of pathophysiologically relevant functions, such as tumor-associated angiogenesis, thrombogenicity, tumor growth, and metastasis. Therefore, targeting TF either by direct inhibition or indirectly, i.e., on a posttranscriptional level, offers a novel therapeutic option for cancer treatment.

CONTENT

In this review we summarize the latest findings regarding the role of TF and its isoforms in cancer biology. Moreover, we briefly depict and discuss the therapeutic potential of direct and/or indirect inhibition of TF activity and expression for the treatment of cancer.

SUMMARY

asTF and flTF play important and often distinct roles in cancer biology, i.e., in thrombogenicity and angiogenesis, which is mediated by isoform-specific signal transduction pathways. Therefore, both TF isoforms and downstream signaling are promising novel therapeutic targets in malignant diseases.

The role of tissue factor isoforms in cancer biology

Tissue Factor (TF) is an evolutionary conserved glycoprotein, which is of immense importance for a variety of biologic processes. TF is expressed in two naturally occurring protein isoforms, membrane-bound "full-length" (fl)TF and soluble alternatively spliced (as)TF. The TF isoform expression is differentially modulated on post-transcriptional level via regulatory factors, such as serine/arginine-rich (SR) proteins, SR protein kinases and micro (mi)RNAs. Both isoforms mediate a variety of physiologic- and pathophysiologic-relevant functions, such as thrombogenicity, angiogenesis, cell signaling, tumor cell proliferation and metastasis. In this review, we will depict the main mechanisms regulating the TF isoform expression in cancer and under other pathophysiologic-relevant conditions. Moreover, we will summarize and discuss the latest findings regarding the role of TF and its isoforms in cancer biology.

Regulation of vascular function on posttranscriptional level

Posttranscriptional control of gene expression is crucial for regulating plurality of proteins and functional plasticity of the proteome under (patho)physiologic conditions. Alternative splicing as well as micro (mi)RNA-mediated mechanisms play an important role for the regulation of protein expression on posttranscriptional level. Both alternative splicing and miRNAs were shown to influence cardiovascular functions, such as endothelial thrombogenicity and the vascular tone, by regulating the expression of several vascular proteins and their isoforms, such as Tissue Factor (TF) or the endothelial nitric oxide synthase (eNOS). This review will summarize and discuss the latest findings on the (patho)physiologic role of alternative splicing processes as well as of miRNAs on modulation of vascular functions, such as coagulation, thrombosis, and regulation of the vascular tone.

The impact of microRNAs on the regulation of tissue factor biology

Tissue factor (TF) and its isoforms play an important role in a variety of physiologic and pathophysiologic functions, such as initiation of blood coagulation, vessel wall hemostasis, angiogenesis, and tumorigenesis. Micro(mi)RNAs are crucial for post-transcriptional control of protein generation by regulating the expression of one-third of all human genes. In recent years, miRNAs were shown to modulate the expression and biologic function of TF in different physiologic- and pathophysiologic-relevant settings, such as in autoimmune diseases and in different types of cancer. In the present review, we will summarize and discuss the latest findings regarding the impact of miRNAs on the generation of TF and its isoforms as well as on regulation of TF biology under normal and pathophysiologic conditions.