In the same study, silencing of SIK dramatically suppressed primary tumorigenesis in an orthotopic breast cancer model, suggesting a pro-oncogenic action of SIK, however, the rare primary tumors that developed under low SIK expression conditions, exhibited a dramatic increase in metastatic incidence, suggesting a role for SIK as a metastasis suppressor [33]. This evidence concerns the gene SIK1 and breast cancer.