 This double action could be enabled by differential protein composition of tumour cells and their environment, for example, dimerisation partners, co-activators and promoter architecture.It is possible that the tumor suppressing activity is due to a proapoptotic function.The exact mechanism by which c-Fos contributes to apoptosis is not clearly understood, but observations in human hepatocellular carcinoma cells indicate that c-Fos is a mediator of c-myc-induced cell death and might induce apoptosis through the p38 MAP kinase pathway.