However, the graphical funnel plots of the 14 studies for histologic grade 1 to 2 versus histologic grade 3 to 4, adenocarcinoma versus squamous cell carcinoma, with LN metastasis versus without LN metastasis for MMP-7 protein expression were symmetrical, and Egger's test showed no publication bias (all P >0.05) (Figure 5). Here, MMP7 is linked to squamous cell carcinoma.