MKI67 and neoplasm: Whereas Ki-67 was not correlated with any of the two β-catenin forms, we found a significant association between β-catenin and nestin expression in WHO grade IV tumours (rho = 0.23, P = 0.002), which was confirmed by demonstrating colocalization of β-catenin and nestin by double immunofluorescence staining (Figure 4(b)).