It has been reported that in 80 to 100% of lung cancer cell lines and tumors [1-4], 49 to 62% of breast cancers [3,5], 67 to 70% of nasopharyngeal cancers [6], 90% of hepatocellular carcinomas [7], 91% of renal cell carcinomas [8], and 70% of prostate cancers [9,10], the RASSF1A gene, but not the RASSF1C gene, is inactivated. Here, RASSF1 is linked to breast carcinoma.