RPS6KB1 and cancer: Quantitative analyses of these assays showed that supernatants derived from the fibroblasts treated with HK1EBV cell-derived exosomes significantly enhanced DNA synthesis (Fig. 3E, lower) and activation of mTOR/p70S6K1, MEK1/2, ERK1/2, and p38 MAPK signaling (Fig. 3F), indicating enhanced cancer cell proliferation.