Identification of a human TFPI-2 splice variant that is upregulated in human tumor tissues

Area of Science:

• Molecular Biology
• Cancer Research
• Biochemistry

Background:

• Tissue factor pathway inhibitor-2 (TFPI-2) expression is often reduced in tumors due to gene promoter hypermethylation.
• A novel 289-nucleotide splice variant of TFPI-2, designated aberrantly-spliced TFPI-2 (asTFPI-2), was identified in human normal and tumor cells.

Purpose of the Study:

• To characterize the novel asTFPI-2 splice variant.
• To investigate the expression levels and stability of asTFPI-2 in tumor cells compared to normal cells.
• To explore the potential role of asTFPI-2 in tumor progression and extracellular matrix degradation.

Main Methods:

• RT-PCR analysis of total RNA from human normal and tumor cells.
• Nucleotide sequence analysis of the asTFPI-2 variant.
• 5'- and 3'-RACE analyses to determine transcript structure.
• Quantitative real-time RT-PCR to measure asTFPI-2 expression levels.
• Assessment of asTFPI-2 half-life in tumor cells.

Main Results:

• asTFPI-2 comprises fused exons II, V, and parts of III and IV, with nucleotides from intron C.
• asTFPI-2 lacks a 5'-untranslated region (UTR) and a 3'-poly (A)+ tail.
• Tumor cells exhibit 4 to 50-fold higher asTFPI-2 levels than normal cells.
• The asTFPI-2 variant demonstrates a half-life of approximately 16 hours in tumor cells despite lacking typical UTRs and a poly(A) tail.

Conclusions:

• A novel, aberrantly-spliced TFPI-2 transcript (asTFPI-2) is predominantly expressed in tumor cells.
• This finding suggests an additional mechanism by which tumor cells down-regulate TFPI-2 protein expression.
• Reduced TFPI-2 protein may enhance tumor cells' capacity for extracellular matrix degradation, potentially promoting invasion and metastasis.