Cisplatin Reduces Epidermal Growth Factor Receptors in Squamous-Cell Carcinoma in vitro

Abstract

A radioreceptor assay was used to determine the number and affinity of epidermal growth factor (EGF) receptors in a human squamous carcinoma cell line of the larynx (HLac 79) after exposure to cisplatin (DDP). Cells exposed to high concentrations of cisplatin showed about 30 % fewer receptors compared to untreated and low-dose-treated cells. This reduction in the number of receptors might be responsible for the decreased growth when stimulated by EGF. Cisplatin appears to lower the concentration of EGF receptors on carcinoma cells, which might result in additional antiproliferative activity especially in carcinomas with high EGF receptor expression.

Improved Antiproliferative Effect of Cisplatin Combined with Phorbol Ester

“…Small changes on the chemical structure of these phorbol esters can cause very different forms of actions [28]; thus, if certain structures could be linked to certain effects, it would be possible to control undesired side effects when using phorbol esters in vivo. Because of the close relation of P K C (the target of phorbol esters) to the E G F receptor, we looked for alterations in number and affinity of the receptors under different treatment conditions but did not find any, in contrast to a study which found a decrease in the affinity in TPA-trcated cells [9,29], We only found a decrease in the number of E G F receptors after a highdose treatment with D D P (more than 4 pg/ml), which has been published earlier [6], Untreated or DDP-treated cells showed an increase in proliferation under simultaneous E G F exposure. A com bination treatment which included TPA or a single TPA treatment did not lead to a significant change in prolifera tion.…”

“…Prior to use, the cell line was recloned by limiting dilution, and cultures were regularly tested to ensure they were free o f mycoplasma contamination (DAPI-test, Boehringcr, Mannheim, F R G ). Cell cultures were carried out in Falcon petri dishes at 37 °C in a 5% CCP fully humidified atmosphere using Dulbecco's modified minimum essential medium (D M E M ) as described earlier [6], Cells growing in a logarithmic phase were plated in 96-wcll microculture plates at 1 X 104 cells/well with 200 pi o f medium overnight. Incubation with substances was for 48 h, and either an M T T or a BrdU assay was subsequently carried out.…”

“…One site of the action could be the epidermal growth factor (EGF) receptor, which is located in the cell membrane and is activated by its ligand E G F to induce cell proliferation and differentiation. Var ious studies showed that the affinity and the number of E G F receptors can be altered by D D P [6,7], which is par ticu lar of interest because head neck tumors and premaiignant mucosa present an increased number of E G F receptors [8], Under normal conditions, E G F induces a receptor-mediated hydrolysis of inositol phospholipids for signal transduction [9,10]. One of the products, diacylglycerol, activates protein kinase C (PKC), a C A 2+-dependent enzyme in the cell membrane, and can modu late the E G F receptor in a feedback manner [11], P K C is actually an enzyme family [ 12] and is considered to be the receptor for tumor-promoting phorbol esters, such as 12-O-tetradecanoylphorbol-13-acetate (TPA) or nonphor boid tumor promoters like mezerein (MEZ) [13].…”

Interleukin 4, interleukin 6 and osteopontin-serological markers of head and neck malignancy in primary diagnostics: A pilot study

“…Regarding therapy-induced EGFR changes in patients, Bergler and Bier (39) recorded a 30% decline in therapy response among patients receiving platinum-based chemotherapy. On the contrary, the control group in the present study showed higher expression levels of EGFR compared with the patient group.…”