Protein kinase C as a target for cancer therapy

Induction of p53-dependent, insulin-like growth factor-binding protein-3-mediated apoptosis in glioblastoma multiforme cells by a protein kinase Calpha antisense oligonucleotide

Protein kinase Calpha (PKCalpha) expression is related to tumor progression in glioblastoma multiforme (GBM), the most common malignant brain tumor in adults. To determine whether PKCalpha regulates an anti-apoptotic survival pathway in GBM, A172 GBM cells were treated with a PKCalpha-selective antisense oligonucleotide. PKCalpha antisense oligonucleotide treatment was accompanied by reduction in PKCalpha levels and the induction of wild-type p53 and insulin-like growth factor-binding protein-3 (IGFBP3) 24-72 h after treatment, a period that coincided with the appearance of apoptotic cell death as detected by DNA fragmentation. There were no significant changes in the levels of Bcl-XL, Bax, and p21(WAF1). Induction of p53 after PKCalpha down-regulation was not associated with increased mRNA expression, but increased IGFBP3 levels were accompanied by increased mRNA levels. Recombinant human IGFBP3 induced an apoptotic effect that was similar to the PKCalpha antisense oligonucleotide, and its effect was blocked by IGF-I. These results suggest that one mechanism by which PKCalpha produces its antiapoptotic activity in GBM cells is by suppressing the p53-mediated activation of IGFBP3.

Antisense oligonucleotides specific for the HER2/neu oncogene inhibit the growth of human breast carcinoma cells that overexpress HER2/neu

The HER2/neu oncogene encodes a cell surface protein which plays a role in growth factor-stimulated mitogenic signaling. HER2/neu is overexpressed in 30-40% of human breast carcinomas. This study tested the hypothesis that inhibiting HER2/neu expression using a phosphorothioate antisense (AS) oligonucleotide would inhibit the growth of breast cancer cells that overexpress this gene. A human breast carcinoma cell line, BT474, which overexpresses the HER2/neu oncogene was exposed to AS, sense (S), or scrambled antisense (SC) phosphorothioate oligonucleotides in tissue culture. Treatment with AS oligonucleotides specifically downregulated HER2/neu mRNA expression and resulted in lower levels of the HER2/neu protein product, p185; control oligonucleotides had no such effect. AS oligonucleotide treatment significantly inhibited the in vitro growth of BT474 cells, whereas S and SC controls had little effect on BT474 growth. HER2/neu AS oligonucleotide treatment had no effect on the growth of a distinct breast cancer line, MCF7, which expresses low levels of the HER2/neu oncogene. Breast carcinoma cells which overexpress the HER2/neu gene appear to be dependent on continued expression of this oncogene for cell growth. AS oligonucleotide pharmaceuticals which interfere with the expression of the HER2/neu oncogene may be of use in the therapy of some patients with breast carcinoma.

Post-translational modification of proteins and the discovery of new medicine

Post-translational modifications are fundamental to processes controlling behaviour, including cellular signaling, growth and transformation. As the molecular basis of protein modifications in normal and disease processes are becoming better defined, so new strategies for designing therapeutic entities to control complex disease processes are emerging.