MMP9 and head and neck squamous cell carcinoma: Regarding the amount of used BMSCs, we wanted to analyze the effect on MMP-9 promoter activity with a low-to-medium number of BMSCs, which we have taken from the literature [85,86] and from preliminary data in our lab, where we found 4000 BMSCs with the given numbers of HNSCC cells to be in a good range for cell survival in 3D.