Methods and compositions for somatic cell proliferation as well as increasing viability of somatic cells are provided. The compositions include heparin binding protein isolated from a medium conditioned by growth of pluripotent stem cells, such as, human embryonic stem cells, human embryonic carcinoma cells. The methods include contacting a somatic cell with a heparin binding protein composition for a sufficient period of time to provide for enhanced proliferation and/or viability of the somatic cell as compared to the absence of the heparin binding protein composition.