This invention generally relates to a composition for developing novel anti-cancer drugs and/or vaccines and producing microRNA precursor (pre-miRNA) and/or its shRNA homologs/mimics/derivatives, and a method thereof. The present invention also relates to a use of a composition in producing novel prokaryote-produced microRNA precursor (pro-miRNA) capable of being delivered into human cells and processed by the cells into microRNA-like effectors to elicit specific silencing effects on certain targeted oncogenes, subsequently leading to a therapeutic result of tumor suppression and cancer therapy. Specifically, the method of the present invention includes inducing an expression of the pre-miRNA/pro-miRNAs, particularly human pre-miR-302, in prokaryotes through pol-2 or pol-2-like RNA promoter. Most importantly, the composition of the present invention is further a novel pre-miRNA-based drug that is capable of reprogramming the malignant properties of high-grade human liver cancers into a low-grade benign or even relatively normal stage—a mechanism called “Cancer Reversion”.