SFRP1 and neoplasm: The frequency of SFRP1 protein expression was low in human primary ESCC tumour, showing that SFRP1 protein was positive in 4.3% (3/70) of ESCC tumour tissues and no positive in the matched normal samples, as demonstrated in Supplementary Fig. 5a, b, SFRP1 exhibited positive expression in part clinical specimens and cell lines.