WNT5A and neoplasm: Although this K6 population was not observed in MMTV-PyVmT tumours, we speculated that because MMTV-PyVmT:Wnt5a-/- tumours display higher levels of intracellular β-catenin and Wnt5a-/- tissue demonstrates increased expression of Sca1, an expansion of this K6-positive population might exist.