MicroRNA-125b Inhibits HNSCC Growth By Regulating Bcl-2 Family Expression

Objective: Squamous cell carcinoma of the head and neck (HNSCC) is among the top ten cancers in the United States and its 5-year survival rate has not significantly changed for the past 2 decades. Studies have been geared towards finding targets, such as apoptosis regulator Bcl-2 family which can be either pro-apoptotic (Bax, BAD) or anti-apoptotic (Bcl-2, Bcl-xL), to improve the treatment and early diagnosis.  In this study, we identified the mechanism of miR-125b-regulated Bcl-2 family expression and evaluated the clinical potential of miR-125b in HNSCC.

Method: A stable expressed exogenous miR-125b HNSCC cell line (JHU-22^miR125b) and an expressed empty vector HNSCC control cell line (JHU-22^vec) were established using lentivirus system. The cell lines were applied in HNSCC tumor xenograft experiments. The tumor xenografts were processed for RNA and protein extraction and formalin fixed histologic studies. Expression of miR-125b was analyzed by using quantitative real time PCR. The protein expression levels of Bcl-2 family members were evaluated using Western blot assay.

Results: The miR-125b transfected cell line stably expressed exogenous miR-125b.The expression levels of JHU-22^miR125b exhibited an approximate fourfold increase in comparison to the control JHU-22^vector.  The average size of   JHU-22^miR125b xenografts (0.20g) was approximately three times smaller than the control JHU-22^vector (0.57g). The protein levels of anti-apoptotic proteins of Bcl-2 family, such as Bcl-2 and Bcl-XL were significantly reduced in JHU-22^miR125b compared to JHU-22^vector control cells, and the pro-apoptotic proteins, Bad and Bax were significantly increased.

Conclusion: miR-125b is able to effectively regulate the apoptosis regulator Bcl-2 family expression. It significantly inhibits HNSCC xenograft growth. The study demonstrates the potential of miR-125b as a value target for HNSCC early diagnosis and treatment.    

Funding: This work was supported in part by the National Cancer Institute P20CA118770.