Notably, co-cultures of CSCs and UC-MSCs form strong and compact spheroids, unresponsive to CXCR2 inhibition, suggesting that physical contact between GBM-CSCs and UC-MSCs, likely mediated by adhesion molecules, is also an important regulator of their biological behavior in addition to, and independently from the soluble chemotactic molecules released. The gene discussed is CXCR2; the disease is glioblastoma.