ADAM17 and neoplasm: Doxycycline-preincubated shNT- and shADAM17- expressing A549 and H358 tumor cells were spotted onto the CAM of fertilized chicken eggs (developmental day 9) to form tumor spheroids, but interestingly only tumor cells proficient in ADAM17 activity were competent to form spheroids (>2,000 μm in diameter; Supplementary Fig. S3A).