A retroviral vector system encoding an oncogene and an shRNA under the control of a single promoter. Schematic representation of the single-vector design of pMmiR^TOI oncogene. Oncogene and a miR30-based TOI-specific shRNA are expressed from the same RNA Pol II promoter LTR. EGFP is expressed via an IRES. The DNA is transcribed by RNA Pol II resulting in one unique mRNA transcript encoding for target-specific miR, oncogene and EGFP as fluorescent marker. Dicer processes miR30 sequence of the transcript or ribosomes initiate translation of the oncogene and EGFP.