Impact of erythropoietin (EPO) on irradiation effect on the EPO receptor–positive head and neck cancer

Abstract

6058 Background: Anemia frequently occurs in Head and Neck Squamous Cell Carcinoma (HNSCC) and has been associated with decreased quality of life, impaired treatment outcomes and shortened survival. Furthermore, anemia is a causative factor of tumor hypoxia, which compromises the efficacy of radiotherapy (RT). In order to circumvent the negative effects of anemia, several attempts have been made including the use of EPO, particularly in HNSCC. However, recent clinical data suggest a detrimental effect of EPO on survival for HNSCC patients treated with RT plus EPO. Methods: The HNSCC CAL-166 cell line, which is wild type p53 and expresses the EPO receptor (EPOR), was investigated in the present study; a MTT test was used to examine the effects of EPO on the cellular response to RT. Extended preliminary experiments were performed to standardize the conditions (time of exposure to hypoxia and time to return of normal culture conditions) and the administration of radiation (fractionated or in single dose) to optimize the effects of hypoxia on radiation response. Cells were exposed to a X-rays source at escalating doses from 2–20 Gy and showed classical dose- response curves. Hypoxia was mimed using a ‘Bug-Box‘ anaerobic workstation for 24–48 hours. Results: After a single RT dose of 10 Gy, the data confirmed the negative effect of hypoxia, directly related to the duration of hypoxia (% surviving cells when irradiated in normoxia: 43.95 ± 4.24; when irradiated after 24 hours of hypoxia, 62.4 ± 8.3 or after 48 hours, % surviving cells 70.8 ± 7.4; p = 0.001 versus RT in normoxia). The addition of EPO, from 24 hours before RT to 72 hours after, until MTT test, did not modify the cytotoxic effect of RT in hypoxic, but also in oxic conditions. Conclusions: These preliminary data do not support a direct negative effect of EPO when treating EPOR positive tumor cells with irradiation. Additional data concern the molecular impact of EPO on tumor cell lines with examination of EPOR, HIF-1 alpha and EGFR. No significant financial relationships to disclose.