Mitogenic and antiapoptotic role of constitutive NF‐κB/Rel activity in pancreatic cancer

Abstract

Pancreatic carcinogenesis is a multistage process that involves numerous genetic alterations, including activating mutations of the Ki-Ras protooncogene by codon 12 mutations. 1 Furthermore, a variety of growth factors and their receptors are found overexpressed and may combine to provide a growth advantage to human pancreatic cancer cells. 2,3 However, downstream targets and in particular nuclear events involved in pancreatic cancer cell growth are poorly understood.Nuclear factor kappa B (NF-B) is a central regulator of the immune response and apoptosis. NF-B/Rel has been implicated in the pathogenesis of certain tumors, especially those of hematopoietic origin. In most cell types, NF-B dimers are sequestered as inactive cytoplasmic complexes by binding to their inhibitors, IBs. A common key event in the activation of NF-B is the inducible phosphorylation of 2 serines at the N-terminus of the inhibitory subunits IB␣, IB␤ or IB⑀. Subsequent IB gets ubiquitinated and degradated by the proteasome. 4 This reaction leaves the active form of NF-B, which is translocated to the nucleus where it binds to regulatory sequences in promoter/enhancer sequences. The mutation or deletion of the 2 serine residues 32 and 36 in IB␣ blocks phosphorylation and degradation of IB␣ protein and results in a superrepressor form of IB␣. 5 Two catalytic subunits, IKK␣ and IKK␤, and a regulatory component, NEMO/IKK␥, have been identified within a large 700 -900 kDa protein complex, which upon stimulation phosphorylates IB␣ at these critical serines. 6 Phosphorylation is followed by an ubiquitination and rapid degradation of IB by a proteasome dependent pathway. 7 This allows the translocation of free active NF-B complexes into the nucleus, where they bind specific DNA motifs in the promoter/enhancer regions of target genes and activate transcription.In this study, we present evidence that the transcription factor NF-B/Rel is constitutively activated in human pancreatic cancer specimen as well as in pancreatic cancer cell lines. NF-B/Rel activity is a result of constitutive IB kinase (IKK) activity and can be inhibited by dominant negative mutants of EGF-R and Ras, the PI3 kinase inhibitor LY294002 or dominant negative mutant Akt kinase. Inhibition of IKK or NF-B/Rel activity induced apoptosis and inhibited anchorage-dependent as well as -independent proliferation of MiaPaCa2 and Panc1 cells. These data demonstrate that NF-B/Rel activity reveals a mitogenic and antiapoptotic role in pancreatic cancer. MATERIAL AND METHODS Tissue samples and immunohistochemistryTissue samples were obtained during surgery on patients with suspected pancreatic cancer and shock frozen in liquid nitrogen. Diagnosis of pancreatic adenocarcinoma was confirmed by an independent pathologist. Sections were fixed with 4% formaldehyde for 15 min and sequentially treated with 0.1% Triton X 100 for 5 min and RNAseA (5 mg/ml) for 30 min at 37°C. Sections were blocked in 2% BSA, 3% goat serum in PBS for 30 min.

High expression of RelA/p65 is associated with activation of nuclear factor-κB-dependent signaling in pancreatic cancer and marks a patient population with poor prognosis

“…However, as translocation of RelA into the nucleus is a required step in the NF-kB activation cascade, the nuclear localisation that was evident in 45.1% of cases can be seen as a first sign of NF-kB activation. Such NF-kB activation in tissue of pancreatic adenocarcinomas was previously noted by Wang et al (1999) and Liptay et al (2003). Wang et al (1999) observed constitutive activation of NF-kB signaling in 14 out of 20 pancreatic adenocarcinomas and in 9 of 11 human pancreatic tumour cell lines.…”

Evodiamine induces apoptosis in pancreatic carcinoma PANC-1 cells via NF κB inhibition

“…It is well established that NF-κB constitutively expressed in pancreatic cancer cells. The constitutive activation of NF-κB is believed to promote inhibition of apoptosis and resistance to chemotherapy (Arlt and Schafer, 2002;Holocomb et al, 2008;Liptay et al, 2003). This notion is further supported by the fact that inactivation of NF-κB sensitizes cancer cells to conventional chemotherapies (Banerjee et al, 2005;Banerjee et al, 2007).…”

Synergistic Antitumor Activity of ZD6474, An Inhibitor of Vascular Endothelial Growth Factor Receptor and Epidermal Growth Factor Receptor Signaling, with Gemcitabine and Ionizing Radiation against Pancreatic Cancer

“…Therefore, we next determined whether ZD6474 could affect the activation of intracellular proteins that are involved in survival signaling. Indeed, EGF and VEGF are also known to be survival factors, rendering cells more resistant to apoptosis and chemotherapy through activation of Akt, which regulates antiapoptotic mechanisms by activating nuclear factor-nB and blocking proapoptotic proteins, including BAD (31,32). It is likely that reduction of pS473 Akt through EGFR inhibition plays an important role in the antitumor activity of ZD6474 in MIA PaCa-2, Capan-1, and PANC-1 cells.…”