WNT1 and neoplasm: Since others have observed high nuclear to cytoplasmic ratios and pleomorphic nuclei associated with Wnt1-induced tumours [24] and it has been suggested that Wnt5a can antagonise the Wnt/β-catenin pathway [7-10], we tested the hypothesis that Wnt5a is a negative regulator of the Wnt/β-catenin pathway in the mammary gland.