Activation of protein kinase C delta induces growth arrest in NPA thyroid cancer cells through extracellular signal-regulated kinase mitogen-activated protein kinase.

Protein kinase C (PKC) is a family of serine-threonine kinases that regulate many cell processes. To study the role of PKCdelta in thyroid cancer cells, we used a replication-deficient adenovirus (PKCdeltaAdV), to tightly control PKCdelta expression. In NPA cells, activation of wild-type (WT) PKCdelta with phorbol 12-myristate 13-acetate (PMA) induced an arrest in cell growth at G(1) phase, which was itself inhibited by the PKCdelta inhibitor rottlerin.

Antineoplaston induces G(1) arrest by PKCalpha and MAPK pathway in SKBR-3 breast cancer cells.

Antineoplastons such as A10 include naturally occurring peptides and amino acid derivatives that control the neoplastic growth of cells. The mechanism underlying this antitumor effect was investigated using the breast cancer cell line, SKRB-3. Cells treated with A10 were monitored for any changes in cell cycle, expression of protein kinase C (PKC), or intracellular signal transduction, particularly phos-phorylation of mitogen-activated protein kinase (MAPK).