In contrast, another study found that type 1 collagen fibers increased in human MDA-MB-231 TNBC xenograft tumors when the hypoxia factors HIF-1α or HIF-2α were downregulated (41), consistent with the earlier finding of reduced collagen fibers in hypoxic tumor regions (42), but apparently contradicting a role for type 1 collagen in TNBC invasion and metastasis. This evidence concerns the gene HIF1A and neoplasm.