(-)-Epigallocatechin gallate downregulates EGF receptor via phosphorylation at Ser1046/1047 by p38 MAPK in colon cancer cells

Journal of Biological Chemistry

Yasuda

Nakashima

et al. 2011

Receptor down-regulation is the most prominent regulatory system of EGF receptor (EGFR) signal attenuation and a critical target for therapy against colon cancer, which is highly dependent on the function of the EGFR. In this study, we investigated the effect of ultraviolet-C (UV-C) on down-regulation of EGFR in human colon cancer cells (SW480, HT29, and DLD-1). UV-C caused inhibition of cell survival and proliferation, concurrently inducing the decrease in cell surface EGFR and subsequently its degradation. UV-C, as well as EGFR kinase inhibitors, decreased the expression level of cyclin D1 and the phosphorylated level of retinoblastoma, indicating that EGFR down-regulation is correlated to cell cycle arrest. Although UV-C caused a marked phosphorylation of EGFR at Ser-1046/1047, UV-C also induced activation of p38 MAPK, a stress-inducible kinase believed to negatively regulate tumorigenesis, and the inhibition of p38 MAPK canceled EGFR phosphorylation at Ser-1046/1047, as well as subsequent internalization and degradation, suggesting that p38 MAPK mediates EGFR down-regulation by UV-C. In addition, phosphorylation of p38 MAPK induced by UV-C was mediated through transforming growth factor-␤-activated kinase-1. Moreover, pretreatment of the cells with UV-C suppressed EGF-induced phosphorylation of EGFR at tyrosine residues in addition to cell survival signal, Akt. Together, these results suggest that UV-C irradiation induces the removal of EGFRs from the cell surface that can protect colon cancer cells from oncogenic stimulation of EGF, resulting in cell cycle arrest. Hence, UV-C might be applied for clinical strategy against human colon cancers. Members of the EGF receptor (EGFR)2 family, which are frequently overexpressed in several types of human cancers, including cancers of the lung (1), head and neck (2), prostate (3), breast (4), pancreas (5), and colon (6), have been associated with abnormal growth of these tumors. It is well known that exposure of cells to EGF results in rapid autophosphorylation of EGFR molecules at the cell surface (7-10), which upon activation lead to cell proliferation, motility, and enhanced survival (11). There are several mechanisms by which EGFR becomes oncogenic including: 1) increased EGFR expression levels, 2) autocrine and/or paracrine growth factor loops, 3) heterodimerization with other EGFR family members and crosstalk with heterologous receptor systems, 4) defective receptor down-regulation, and 5) activating mutations (12). In clinical trials, increasing evidence shows the efficacy of EGFR-targeted agents, including monoclonal antibodies on the one hand and tyrosine kinase inhibitors on the other (13).Following activation, the ligand-receptor complexes are internalized and then enter endosomes, where the receptors and their ligands are sorted to various intracellular destinations (14). Thus, some receptors can be recycled back to the cell surface via early endosomes, and others are targeted to late endosomes and lysosomes for proteolytic degradation. There is increasin...

Section: Discussionmentioning

confidence: 99%

Section: Members Of the Egf Receptor (Egfr)mentioning

confidence: 99%

Ultraviolet Irradiation Can Induce Evasion of Colon Cancer Cells from Stimulation of Epidermal Growth Factor

Journal of Biological Chemistry

Yasuda

Nakashima

et al. 2011

“…We have previously reported that (-)-epigallocatechin gallate (EGCG) caused internalization of EGFR into endosomal vesicles (23). Moreover, we have recently shown that EGCG downregulates EGFR via phosphorylation at Ser1046/7 by p38 MAPK in colon cancer cells (25). In the present study, we investigated the involvement of p38 MAPK in EGFR desensitization induced by HSP90 inhibitors and showed that p38 MAPK activated by HSP90 inhibitors induced desensitization of EGFR via its phosphorylation at Ser1046/7.…”

Section: Discussionmentioning

confidence: 75%

“…1B-D, upper panels). In addition, we examined the effects of 17-AAG on the phosphorylation of EGFR at Ser1046/7, since this phosphorylation has been reported to play an important role in EGFR desensitization (20,25). Interestingly, 17-AAG induced phosphorylation of EGFR at Ser1046/7 at a peak of 30 min to 1 h (Fig.…”

Section: -Aag Caused Desensitization Of Egfr Concurrently Inducingmentioning

confidence: 96%

HSP90 inhibitors induce desensitization of EGF receptor via p38 MAPK-mediated phosphorylation at Ser1046/1047 in human pancreatic cancer cells

Yasuda²,

Nakashima³

et al. 2010

Oncol Rep

Abstract. Heat shock protein (HSP) 90 is known to be a molecular chaperone whose association is required for the stability and function of oncogenic protein including epidermal growth factor receptor (EGFR) that promotes cancer cell growth. Therefore, HSP90 is a promising target for therapy against cancer including in the pancreas, some of which are highly dependent on EGFR. We investigated the effects of HSP90 inhibitors on cytotoxicity and desensitization of EGFR in human pancreatic cancer cells (KP3, BxPc3 and AsPc1). 17-allylamino-17-demethoxy-geldanamycin (17-AAG), an inhibitor of HSP90, caused desensitization of EGFR in a time-dependent manner, concurrently inducing phosphorylation of EGFR at Ser1046/ 1047 (Ser1046/7), a site which plays an important role in EGFR desensitization in these pancreatic cancer cells. We also found similar effects in KP3 cells treated with other HSP90 inhibitors, geldanamycin and 17-dimethylaminoethylamino-17-demethoxy-geldanamycin (17-DMAG). In KP3 cells, 17-AAG induced activation of either p44/p42 mitogenactivated protein kinase (MAPK) or p38 MAPK. Interestingly, whereas the inhibition of p44/p42 MAPK attenuated neither phosphorylation of EGFR at Ser1046/7 nor desensitization of EGFR, the phosphorylation at Ser1046/7 induced by 17-AAG was markedly attenuated by the inhibition of p38 MAPK, indicating that p38 MAPK induced this phosphorylation. Moreover, the inhibition of p38 MAPK significantly attenuated 17-AAG-induced EGFR desensitization. These results strongly suggest that EGFR phosphorylation at Ser1046/7 via activation of p38 MAPK induced by HSP90 inhibitors plays a pivotal role in EGFR desensitization in human pancreatic cancer cells.

“…Immunofluorescence microscopy was performed as described previously (15). The cells grown on coverslip-bottom dishes were first exposed to UV-C (200 J) and incubated for 6 h at 37˚C, followed by exposure to Hoechst 33258 for 30 min in RPMI containing 1% bovine serum albumin (BSA).…”

Section: Methodsmentioning

confidence: 99%

Ultra-violet irradiation induces apoptosis via mitochondrial pathway in pancreatic cancer cells

2011

Int J Oncol

Abstract. Pancreatic cancer is a highly lethal disease and gemcitabine is considered to be the standard of care for the treatment of advanced pancreatic cancer. However, the outcome of the patients treated with gemcitabine is still unstatisfactory and further development of new treatments is required. We recently found that short wavelength ultra-violet (UV-C) suppresses cell proliferation with downregulation of epidermal growth factor receptor (EGFR) in human pancreatic cancer cells, but not in normal pancreatic epithelial (PE) cells. In this study, we investigated the effect of UV-C on apoptosis in several cell lines derived from the pancreas. UV-C induced poly(ADPribose) polymerase (PARP) cleavage, which is a marker of cells undergoing apoptosis, in Panc1, MiaPaca2, KP3 and BxPC3 pancreatic cancer cells, but not in PE cells. We also observed similar effects in Hoechst 33258 staining, which shows DNA fragmentation. While p53, a tumor suppressor protein, plays a critical role in UV-C-induced cell damage, we did not observe the correlation between the sensitivity to UV-C and p53 status. Thapsigargin, an agent that promotes endoplasmic reticulum (ER) stress by depletion of lumenal calcium stores, as well as cis-diamineplatinum (II) dichloride, a classical anti-cancer drug that causes DNA damage, induced PARP cleavage even in PE cells. Moreover, UV-C-induced apoptosis in Panc1 and KP3 cells was associated with the release of cytochrome c, indicating that it was mediated via mitochondrial pathway. Taken together, UV-C has a potent anti-cancer effect on pancreatic cancer cells without adverse effect on normal cells and it could be useful for the treatment of human pancreatic cancers.