HIF1A and neoplasm: However, the confounding influence of other tumor microenvironmental abnormalities like low glucose and/or low pH on HIF-1α target genes [17-20] or non-hypoxic HIF-1α activation by abnormal signalling or mutations [21,22] may be responsible for some of the spatial discrepancy observed between injectable hypoxia markers (e.g., pimonidazole) and O2-responsive gene protein products (reviewed in [9,10,23]).