The synergistic activation mediator (SAM) system can robustly activate endogenous gene expression by a single-guide RNA. This transcriptional modulation has been shown to enhance gene promoter activity and leads to epigenetic changes. Human interferon-γ is a common natural glycoprotein involved in antiviral effects and inhibition of cancer cell growth. Large quantities of high-purity interferon-γ are important for medical research and clinical therapy. To investigate the possibility of employing the SAM system to enhance endogenous human interferon-γ with normal function in innate immunity, we designed 10 single-guide RNAs that target 200 bp upstream of the transcription start sites of the interferon-γ genome, which could significantly activate the interferon-γ promoter reporter. We confirmed that the system can effectively and highly activate interferon-γ expression in several humanized cell lines. Moreover, we found that the interferon-γ induced by the SAM system could inhibit tumorigenesis. Taken together, our results reveal that the SAM system can modulate epigenetic traits of non-immune cells through activating interferon-γ expression and triggering JAK-STAT signaling pathways. Thus, this strategy could offer a novel approach to inhibit tumorigenesis without using exogenous interferon-γ.