Recent developments in RNAi, particularly in the design of lentiviral-based short hairpin RNA (shRNA), now allow researchers to potentially develop diagnostic and prognostic strategies for treating cancer and metastasis.
Cancer has the ability to spread or metastasize via blood circulation, lymphatic system or both, with common re-occurrence of cancer in the lungs, liver, bones and brain. To date, few methodologies are available to understand the molecular basis of metastases. With developments in RNAi, in particular, lentiviral-based expression of these genetic silencing tools, offers the benefits of inducing stable and long-term gene silencing in both dividing and non-dividing cells.
shRNAmir-based silencing strategies are now widely adopted with several reports using pGIPZ lentiviral constructs in vivo to address the molecular determinants of cancer. One example is melanoma, which is now considered one of the most aggressive types of skin cancer conferring poor prognosis due to the development of metastases to the lungs, liver or brain. In a study from Isaiah Fidler’s group at The University of Texas, a xenograft approach using pGIPZ lentiviral constructs was used to investigate the effects of transforming growth factor-β2 (TGF-β2) on melanoma cell growth and metastases in the brain. Previous reports indicated that tissue specific attributes of metastasis are often associated with high TGF-β2 expression. Injecting genetically modified melanoma cells, which express high levels of TGF-β2 into the carotid artery of mice, is known to produce metastasis in the brain parenchyma, modeling the clinical outcome of melanoma metastasis. Interestingly, shRNAmir-mediated TGF-β2 knockdown in these cells decreased metastasis to the brain parenchyma and doubled the survival times of tumour-bearing mice when compared to mice injected with melanoma cells stably expressing a control shRNAmir. These results suggest that TGF-β2 expression in melanoma cells is necessary for metastases to establish and grow specifically in the brain parenchyma.
*Original article published by Kirsteen MacLean, PhD, for Thermo Fisher Scientific, a supplier of lentiviral shRNAmir constructs for gene suppression studies
