Secreted uPAR isoform 2 (uPAR7b) is a novel direct target of miR-221

Area of Science:

• Molecular Biology
• Oncology
• Biochemistry

Background:

• MicroRNA-221/222 and urokinase-type plasminogen activator system (uPAS) components are linked to metastasis and poor prognosis in breast cancer, especially triple-negative breast cancer (TNBC).
• Targeting uPAS components and microRNAs presents a potential therapeutic strategy for breast cancer.

Purpose of the Study:

• To investigate the direct targeting of urokinase plasminogen activator receptor (uPAR) isoform 2 by microRNA-221/222.
• To elucidate the role of miR-221 in regulating uPAR expression and its impact on breast cancer malignancy.

Main Methods:

• Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analyses were used to assess uPAR expression in relation to miR-221/-222.
• In silico analyses and in vitro assays were performed to confirm direct targeting of uPAR isoform 2's 3' untranslated region (UTR) by miR-221/-222.
• Inhibition of miR-221 was employed to study its effect on uPAR protein expression and invasion markers.

Main Results:

• Significant associations between miR-221 and uPAR isoform 2 expression were observed at both mRNA and protein levels in TNBC cells.
• uPAR isoform 2 was identified as a direct target of miR-221/-222.
• Inhibition of miR-221 led to reduced uPAR protein expression and decreased expression of invasion markers like vimentin and RHOC.
• miR-221 directly and positively regulates secreted uPAR isoform 2, enhancing its protein expression and contributing to malignancy.

Conclusions:

• This study demonstrates for the first time that uPAR isoform 2 is a direct target of miR-221/-222.
• miR-221 positively regulates uPAR isoform 2 expression, a key factor in breast cancer malignancy.
• Targeting uPAR isoforms and/or miR-221/-222 holds promise for improving the diagnosis and therapy of breast cancer, particularly TNBC.