Abstract 185: MicroRNA-375 suppresses extracellular matrix degradation and invadopodial activity in head and neck squamous cell carcinoma
Authors: Jimenez Lizandra , Sharma Ved P. , Condeelis John S. , Harris Thomas M. , Ow Thomas J. , Prystowsky Michael B. , Childs Geoffrey J. , Segall Jeffrey E. 
Published: August 2015

Head and neck squamous cell carcinoma (HNSCC) is a highly invasive cancer having an association with locoregional recurrence and lymph node metastasis. We previously reported that patients with lower microRNA-375 (miR-375) tumor:normal expression levels showed significantly decreased disease-specific survival, increased locoregional recurrence and distant metastasis. We also previously described that HNSCC cells with increased miR-375 showed significantly diminished invasion in vitro. The ability of cancer cells to degrade extracellular matrix (ECM) through secreted and membrane-bound proteases allows local invasion into the surrounding stroma, as well as possible metastasis. Invadopodia are specialized actin-rich structures, which mediate ECM degradation. Our objective was to determine whether elevated miR-375 expression in HNSCC cells also affects invadopodia formation and activity.

For the evaluation of the matrix degradation properties of UMSCC1 and OSC19 cell lines, an invadopodial matrix degradation assay was used. Western blot analyses were conducted to measure the total protein levels of selected invadopodia-associated proteins. The tyrosine phosphorylation states of cortactin were evaluated by immunoprecipitation experiments. For the detection of levels of secreted proteases in the conditioned cell growth medium, Human Protease Arrays were used. Quantitative RT-PCR measurements were used to evaluate the mRNA expression levels of the commonly regulated proteases.

We observed that the HNSCC cell lines with elevated miR-375 expression showed significant reductions in ECM degradation. We further identified that HNSCC cells expressing increased miR-375 expression had significantly suppressed amounts of mature invadopodia, although the levels of invadopodium precursors were not significantly altered. We determined that increased miR-375 expression in the HNSCC cell lines did not reduce cellular levels of invadopodia components, such as Tks5, cortactin and fascin. We also did not observe significant alterations to the tyrosine phosphorylation states of cortactin in the HNSCC cell lines. However, we found that the HNSCC cells with higher miR-375 expression had significant reductions in the mRNA expression and secreted levels of specific proteases, including Kallikrein 6, Kallikrein 10, and MMP-9.

In summary, we have extended our understanding of the impact of miR-375 expression levels on HNSCC invasion. We demonstrated that increased miR-375 expression in HNSCC cells reduced ECM degradation and invadopodial activity. Our data suggest that reduced miR-375 expression in HNSCC patients can contribute to the invasive properties of head and neck cancer through increased invadopodial activity.

Citation Format: Lizandra Jimenez, Ved P. Sharma, John S. Condeelis, Thomas M. Harris, Thomas J. Ow, Michael B. Prystowsky, Geoffrey J. Childs, Jeffrey E. Segall. MicroRNA-375 suppresses extracellular matrix degradation and invadopodial activity in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 185. doi:10.1158/1538-7445.AM2015-185