According to these observations it was concluded that CD133 expression is upregulated in colon cancers that have hyper-activated RAS-RAF-MEK-ERK as a consequence of mutations in K-RAS or BRAF [364]; since mutations in these genes are related to prognosis, it was concluded that CD133 expression is not indicative of cancer stem cell numbers, but rather dependent on the mutational status of the RAS-RAF pathway [370]. Here, KRAS is linked to cancer.