HIF1A and fibrosarcoma: While the studies reported herein were ongoing, Lee et al (2011) have additionally implicated intact HIF-1α signalling as critical to the effects of chaetocin itself in at least some circumstances, demonstrating that chaetocin inhibits tumour growth in vivo in a HIF-1α(+/+) fibrosarcoma xenograft model that is abrogated in a corresponding HIF-1α(−/−) model, hence implicating chaetocin-altered splicing of HIF-1α pre-mRNA as contributory to in vivo effects in this model system (Iwasa et al, 2010).