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We herein report an innovative antisense approach based on Peptide Nucleic Acids (PNAs) to down-modulate CD5 expression levels in chronic lymphocytic leukemia (CLL). Using bioinformatics tools, we selected a 12-mer tract of the CD5 mRNA as the molecular target and synthesized the complementary and control PNA strands bearing a serine phosphate dipeptide tail to enhance their water solubility and bioavailability. The specific recognition of the 12-mer DNA strand, corresponding to the target mRNA sequence by the complementary PNA strand, was confirmed by non-denaturing polyacrylamide gel electrophoresis, thermal difference spectroscopy, circular dichroism (CD), and CD melting studies. Cytofluorimetric assays and real-time PCR analysis demonstrated the downregulation of CD5 expression due to incubation with the anti-CD5 PNA at RNA and protein levels in Jurkat cell line and peripheral blood mononuclear cells from B-CLL patients. Interestingly, we also observed that transfection with the anti-CD5 PNA increases apoptotic response induced by fludarabine in B-CLL cells. The herein reported results suggest that PNAs could represent a potential candidate for the development of antisense therapeutic agents in CLL.

A highly differentiated thyroid cell line (FR-TL) was compared with a less differentiated (FR-T Cl1) and an undifferentiated (1–5G) cell line. FR-TL is modulated in vivo and in vitro by thyrotropin and has the lowest adenylate cyclase and guanylate cyclase and the highest phosphodiesterase activities. In contrast, 1–5G tumor cells do not respond to thyrotropin and have the highest adenylate cyclase and guanylate cyclase and lowest hydrolyzing enzyme activities. Intermediate enzyme activities were found in FR-T Cl2 cells. The differences between the two normal rat thyroid cell lines are not due to differences in the composition of the growth medium.