CCNB1 and esophageal squamous cell carcinoma: These results are not consistent with previous results about the biology of RPRM. However, a previous study by Song et al. into cyclin B1 (a protein target of RPRM) demonstrated that, in addition to its known role in arresting the G2/M cell cycle phase, overexpression of cyclin B1 in human esophageal squamous cell carcinoma (ESCC) promotes cell invasive growth and extravasation through the capillary endothelium.