We only have one specimen in grade I that is negative, so the sample number is too small to draw conclusion for grade I. We also observed the elevation of Stat3 phosphorylation from Stage 0 to IIB and even detected two out of three squamous cell carcinoma in situ (TisN0M0) are positive (Supplementary Table 2). Here, STAT3 is linked to squamous carcinoma in situ.