Very recently, Pouyssegur and coworkers have reported that the simultaneous invalidation of CA IX and CA XII using short hairpin RNA technology led to a substantial growth retardation in transfected LS174T colorectal cancer xenograft models, whereas the individual knock-outs yielded a substantially lower tumour growth retardation (Chiche et al, 2009). The gene discussed is CA9; the disease is neoplasm.