Identification of a novel human tissue factor splice variant that is upregulated in tumor cells

Abstract

Tissue factor (TF) is a transmembrane glycoprotein that serves as the prime initiator of blood coagulation and plays a critical role in thrombosis and hemostasis. In addition, a variety of tumor cells overexpress cell-surface TF, which appears to be important for tumor angiogenesis and metastasis. To elucidate the mechanism involved in the upregulation of TF in human tumor cells, a comprehensive analysis of TF mRNA from various normal and tumor cells was performed. The results of these studies indicate that, in addition to possessing a normal full-length TF transcript and minor levels of an alternatively spliced transcript known as alternatively-spliced tissue factor (asTF) (Bogdanov et al., Nat Med 2003;9:458-62), human tumor cells express additional full-length TF transcripts that are also generated by alternative splicing. Reverse transcriptase-polymerase chain reaction (RT-PCR) and 5 0 -rapid amplification of cDNA ends-(5 0 -RACE) based analyses of cytoplasmic RNA from normal and tumor cells revealed that there is alternative splicing of the first intron between exon I and exon II resulting in 2 additional TF transcripts. One of the transcripts has an extended exon I with inclusion of most of the first TF intron (955 bp), while the second transcript is formed by the insertion of a 495 bp sequence, referred to as exon IA, derived from an internal sequence of the first intron. The full length TF transcript with alternatively spliced novel exon IA, referred to as alternative exon 1A-tissue factor (TF-A), represented~1% of the total TF transcripts in normal cells, but constituted 7-10% of the total TF transcript in tumor cells. Quantitative real-time RT-PCR analysis indicated that cultured human tumor cells contain 10-25-fold more copy numbers of TF-A in comparison to normal, untransformed cells. We propose that high-level expression of the novel TF-A transcript, preferentially in tumor cells, may have utility in the diagnosis and staging of a variety of solid tumors. ' 2005 Wiley-Liss, Inc.

Tissue Factor: A Conventional or Alternative Target in Cancer Therapy

“…The TF-A mRNA splice variant is not translated to a protein ( Fig. 1) because of termination sequences within alternative exon 1A, leading to an early translation stop (11 ). TF-A mRNA expression has been detected in several cancer cell lines as well as in human endothelial cells (5,11 ).…”

“…1) because of termination sequences within alternative exon 1A, leading to an early translation stop (11 ). TF-A mRNA expression has been detected in several cancer cell lines as well as in human endothelial cells (5,11 ). However, the biological function of TF-A is still unknown (5,11 ).…”

“…TF-A mRNA expression has been detected in several cancer cell lines as well as in human endothelial cells (5,11 ). However, the biological function of TF-A is still unknown (5,11 ). flTF and asTF are expressed in several types of cancer cells and tumors and play important roles in cancer biology, i.e., in thrombogenicity, survival, tumor growth, angiogenesis, signaling, invasion, and metastasis (2-4, 8, 12, 13 ).…”

Tissue Factor and Cancer

“…This can arise through the release of molecular isoforms of TF that lack the membrane-spanning domain, e.g. as a result of alternative splicing (asTF) [40][41][42][43] . While the ability of these soluble TF isoforms to trigger coagulation is a matter of some debate [40,44] , an alternative mechanism leads to the release of a coagulation competent full-length TF from various cells, both in vitro and in vivo, notably as cargo of membrane microvesicles [5,[45][46][47][48][49][50][51][52][53][54] .…”

The Immunoconjugate “Icon” Targets Aberrantly Expressed Endothelial Tissue Factor Causing Regression of Endometriosis

“…14 -17 Recent studies indicate that the type-2 proteinase activated receptor (PAR-2) is intimately involved in TF-mediated signaling and angiogenesis. 15,18,19 Tissue factor may initiate differential signaling pathways in physiological compared with pathological angiogenesis, 20 to wit, the physiological pathway is mediated by TF-thrombin-PAR-1 and the pathological pathway by TF/factor FVIIa/PAR-2 signaling. 20 These latter vessels display abnormal structure and function and are Supported in part by grants from the NIH U54HD052668, and the Swebilius Translational Cancer Research Award from Yale Cancer Center (to Z.H.…”