BCL-2 functions as an activator of the AKT signaling pathway in pancreatic cancer

• Published in: Journal of cellular biochemistry 2007-12, Vol.102 (5), p.1171-1179
• Main Authors: Mortenson, Melinda M., Galante, Joseph G., Gilad, Oren, Schlieman, Michael G., Virudachalam, Subbulakshmi, Kung, Hsing-Jien, Bold, Richard J.
• Format: Article
• Language: English
• Subjects: AKT; Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis - drug effects; BCL-2; Benzopyrans - pharmacology; Cell Line, Tumor; Cell Survival - drug effects; Clone Cells; DNA, Complementary; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Genes, Reporter; Humans; Immunohistochemistry; Luciferases, Renilla - metabolism; NF-kappa B - physiology; Nitriles - pharmacology; Paclitaxel - pharmacology; pancreatic cancer; Pancreatic Neoplasms - metabolism; Pancreatic Neoplasms - pathology; Phosphorylation - drug effects; Precipitin Tests; Proto-Oncogene Proteins c-akt - antagonists & inhibitors; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-akt - physiology; Proto-Oncogene Proteins c-bcl-2 - antagonists & inhibitors; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Signal Transduction; Subcellular Fractions - metabolism; Transfection
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.21343

BCL‐2 is the prototypic anti‐apoptotic protein involved in the regulation of apoptosis. Overexpression of BCL‐2 is common in pancreatic cancer and confers resistance to the apoptotic effect of chemo‐ and radiotherapy. Although these cellular effects of BCL‐2 are traditionally related to pathways involving the mitochondrial membrane, we sought to investigate whether BCL‐2 is involved in other signaling pathways regulating cell survival and focused on AKT. We examined the effect of overexpression of BCL‐2 in the MIA‐PaCa‐2 human pancreatic cancer cell line on the function and subcellular location of AKT. We observed that the stable subclones of MIA‐PaCa‐2 overexpressing BCL‐2 demonstrated increased activity of AKT as well as IKK (a downstream target of AKT), increasing the transcriptional activity of NF‐κB. Using immunoprecipitation techniques, we observed co‐immunoprecipitation of AKT and BCL‐2. Immunocytochemistry demonstrated co‐localization of BCL‐2 and AKT, which was abrogated by treatment with HA14‐1, a small molecule inhibitor of BH‐3‐mediated protein interaction by BCL‐2. Furthermore, treatment with HA14‐1 decreased phosphorylation of AKT and increased sensitivity to the apoptotic effect of the chemotherapeutic agent, paclitaxel. These results demonstrate an additional mechanism of regulation of cell survival mediated by BCL‐2, namely through AKT activation, in the MIA‐PaCa‐2 pancreatic cancer cell line. Therefore, directed inhibition of BCL‐2 may alter diverse pathways controlling cell survival and overcome the apoptotic resistance that is the hallmark of pancreatic cancer. J. Cell. Biochem. 102: 1171–1179, 2007. © 2007 Wiley‐Liss, Inc.