Alternative splicing has emerged as an important target for molecular
therapies. Splice-switching
oligonucleotides (SSOs) modulate alternative splicing by hybridizing to
pre-mRNA sequences involved in splicing and blocking access to the transcript by
splicing factors. Recently, the efficacy of SSOs has been established in various
animal disease models; however, the application of SSOs against
cancer targets has been hindered by poor in vivo delivery of antisense
therapeutics to
tumor cells. The apoptotic regulator Bcl-x is alternatively spliced to express anti-apoptotic Bcl-x(L) and pro-apoptotic Bcl-x(S). Bcl-x(L) is upregulated in many
cancers and is associated with chemoresistance, distinguishing it as an important target for
cancer therapy. We previously showed that redirection of Bcl-x
pre-mRNA splicing from Bcl-x(L) to -x(S) induced apoptosis in breast and
prostate cancer cells. In this study, the effect of SSO-induced Bcl-x splice-switching on metastatic
melanoma was assessed in cell culture and B16F10
tumor xenografts. SSOs were delivered in vivo using
lipid nanoparticles. Administration of nanoparticle with Bcl-x SSO resulted in modification of Bcl-x
pre-mRNA splicing in lung
metastases and reduced
tumor load, while nanoparticle alone or formulated with a control SSO had no effect. Our findings demonstrate in vivo anti-
tumor activity of SSOs that modulate Bcl-x
pre-mRNA splicing.