SOCS1 and neoplasm: While studying the tumor suppressor functions of SOCS1, we compared the murine hepatocellular carcinoma cell line Hepa 1-6 expressing wildtype SOCS1 (Hepa-SOCS1), an SH2 domain mutant of SOCS1 (R105K) that does not inhibit IFNγ signaling (Hepa-SOCS1R) or a control vector (Hepa-Vector) (64) for their ability to form tumors.