Indeed, knockdown of TPC2 expression and pharmacological inhibition in 4T1 orthotopic breast cancer and RIL175 hepatocellular carcinoma mouse xenograft models reduced the formation of lung metastases in vivo [45, 51], providing additional evidence that TPC2 is an important enhancer of metastasis in vivo, particularly for breast and hepatocellular cancer, and suggest that TPC2 may be a potential therapeutic target for preventing cancer metastasis, at least in breast and hepatocellular cancers. This evidence concerns the gene TPCN2 and breast cancer.