In leiomyosarcoma (SK-LMS-1) and soft tissue sarcoma (STS117) spheroids grown in microfluidic devices, hypoxic cores confirmed by carbonic anhydrase IX (CAIX) staining enhanced response to radiotherapy when combined with the hypoxia-activated agent tirapazamine, which selectively targeted central regions [88]. This evidence concerns the gene CA9 and leiomyosarcoma.