Role of epidermal growth factor receptor degradation in gemcitabine-mediated cytotoxicity

Abstract

We have recently reported that treatment with gemcitabine, a potent chemotherapeutic agent and radiation sensitizer, stimulates phosphorylation of the epidermal growth factor receptor (EGFR). Because phosphorylation of EGFR is known to precede receptor degradation, we hypothesized that gemcitabine treatment may also result in EGFR degradation. In two human head and neck cancer cell lines, UMSCC-1 and UMSCC-6, we demonstrated an approximately 80% decrease in total EGFR levels at 72 h after a 2-h treatment with 1 lM gemcitabine. Neither cisplatin nor 5-fluorouracil, which are used to treat head and neck cancer, caused EGFR degradation. EGFR downregulation did not occur at the level of transcription, as assessed by reverse transcription-polymerase chain reaction (RT-PCR), but instead occurred via phosphorylation and ubiquitination of the receptor along a proteosome/lysosome-mediated pathway. Inhibition of EGFR degradation, by either pretreatment with the EGFR tyrosine kinase inhibitor gefitinib or by exposure to the proteosome/lysosome inhibitor MG132, significantly reduced gemcitabine-induced cell death. These results suggest that EGFR degradation may be a novel mechanism for gemcitabine-mediated cell death. These findings also indicate that caution should be exercised when combining gemcitabine with agents that may prevent EGFR degradation, such as EGFR tyrosine kinase inhibitors administered in a suboptimal sequence or proteosome inhibitors.

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

“…There is increasing evidence that not only does receptor internalization act to terminate signaling, but that internalized endosome-associated receptors are also able to stimulate specific signal transduction pathways (15)(16)(17). Some agents that induce ligand-independent internalization and degradation of EGFR, such as the 225 mouse antibody (18) and gemcitabine (5), could have promising potential for cancer therapies. By contrast, it has previously been reported that the other factors or agents, such as oxidative stress (19) and cisplatin (20), can induce internalization of the EGFR but not degradation.…”

“…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)(8)(9)(10), which upon activation lead to cell proliferation, motility, and enhanced survival (11).…”

Gemcitabine Inhibits Murine Head and Neck Squamous Cell Carcinoma Growth via Proteasome-Dependent Degradation of Chk1 Leading to Cell Cycle Arrest and Apoptosis

“…This finding suggests gemcitabine effect Chk1 transcription is transient and cannot be responsible for the total depletion of the Chk1 protein. Another potential mechanism is that gemcitabine treatment has been shown to cause activation and subsequent degradation of epidermal growth factor receptor (EGFR) in human HNSCC cells via ubiquitination along the proteasome/lysosome mediated path-way [40]. In a similar fashion, pretreatment of LY2 cells with proteasome inhibitor MG132 reduced Chk1 protein depletion when exposed to gemcitabine and decreased LY2 cells sensitivity to gemcitabine.…”

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

“…These agents include oxidative stress (37), ultraviolet irradiation (38), gemcitabine (39) and cisplatin (40). We have previously reported that (-)-epigallocatechin gallate (EGCG) caused internalization of EGFR into endosomal vesicles (23).…”