miR-665 targets c-MYC and HDAC8 to inhibit murine neuroblastoma cell growth.

Neuroblastoma is a common tumor of the peripheral nervous system in children. Highly aggressive MYC-driven neuroblastoma is defined by increased c-MYC and/or MYCN expression. This study employed a mouse neuroblastoma cell model to assess the role of miR-665 in tumorigenesis. We found that miR-665 suppresses mRNAs, targeting c-MYC and HDAC8, which are involved in neuroblastoma tumorigenesis. N6,2'-O-dibutyryladenosine 3':5'cyclic monophosphate (Bt2cAMP) inhibited neuroblastoma cell growth by inhibiting c-MYC and HDAC8 expression and activating caspase 3. Bt2cAMP also upregulated miR-665, and miR665 transfection mimicked the effects of Bt2cAMP, including reduced c-MYC and HDAC8 expression, increased caspase 3 activation, and reduced neuroblastoma cell growth. As compared to untreated cells, Bt2cAMP increased the number of cells in G1 phase by 50% and the number in G2-M phase by 5%, while the number of cells in S phase was reduced 2.8-fold. Similarly, miR-665 transfection increased the number of cells in G1 phase by 16% and the number in G2M phase by 2%, and decreased the cells in S-phase by 18%. These findings indicate miR-665 suppresses neuroblastoma tumorigenesis by inhibiting c-MYC and HDAC8 expression and suggest miR-665 has potential as an anti-neuroblastoma therapeutic.

Apo B100 similarities to viral proteins suggest basis for LDL-DNA binding and transfection capacity.

LDL mediates transfection with plasmid DNA in a variety of cell types in vitro and in several tissues in vivo in the rat. The transfection capacity of LDL is based on apo B100, as arginine/lysine clusters, suggestive of nucleic acid-binding domains and nuclear localization signal sequences, are present throughout the molecule. Apo E may also contribute to this capacity because of its similarity to the Dengue virus capsid proteins and its ability to bind DNA. Synthetic peptides representing two apo B100 regions with prominent Arg/Lys clusters were shown to bind DNA. Region 1 (0014Lys-Ser0160) shares sequence motifs present in DNA binding domains of Interferon Regulatory Factors and Flaviviridae capsid/core proteins. It also contains a close analog of the B/E receptor ligand of apo E. Region 1 peptides, B1-1 (0014Lys-Glu0054) and B1-2 (0055Leu-Ala0096), mediate transfection of HeLa cells but are cytotoxic. Region 2 (3313Asp-Thr3431), containing the known B/E receptor ligand, shares analog motifs with the human herpesvirus 5 immediate-early transcriptional regulator (UL122) and Flaviviridae NS3 helicases. Region 2 peptides, B2-1 (3313Asp-Glu3355), and B2-2 (3356Gly-Thr3431) are ineffective in cell transfection and are noncytotoxic. These results confirm the role of LDL as a natural transfection vector in vivo, a capacity imparted by the apo B100, and suggest a basis for Flaviviridae cell entry.