Increased expression of pro-inflammatory cytokines as a cause of lung toxicity after combined treatment with gemcitabine and thoracic irradiation.
OBJECTIVE
Preclinical evidence suggesting gemcitabine potentiates the anti-tumor effects of irradiation has resulted in clinical trials to evaluate the treatment efficacy of gemcitabine and concurrent thoracic irradiation in non-small-cell lung cancer (NSCLC). Although these studies demonstrated favorable tumor response, this combined treatment modality was accompanied by severe treatment-related toxicities predominantly of the lung. In an attempt to elucidate the determinants of lung toxicity for gemcitabine, we analyzed the expression of the pro-inflammatory cytokines TNF-alpha, IL-1alpha and IL-6 in the lung tissue of mice treated with gemcitabine and concurrent thoracic irradiation.


METHODS
Four study groups were defined: C57BL/6J mice that received neither irradiation nor gemcitabine (NT-group), those that received gemcitabine (120 mg/kg intraperitoneal, i.p.) but no irradiation (GEM-group), those that underwent thoracic irradiation (12 Gy) without gemcitabine (XRT-group), and those that received both gemcitabine (120 mg/kg i.p., 2 h before irradiation) and thoracic irradiation (GEM/XRT-group). The mice were sacrificed at 1 h, 1 and 3 days, 1, 2 and 4 weeks post-treatment (p.t.). The mRNA expression of TNF-alpha, IL-1alpha and IL-6 in the lung tissue was quantified by competitive RT-PCR. The cellular origin of the cytokine expression was identified by immunohistochemistry. The cytokine expression was correlated with histopathological alterations.


RESULTS
The TNF-alpha, IL-1alpha and IL-6 expression in the lung tissue of the GEM/XRT mice was clearly higher at all assessment time points compared to the NT mice (statistically significant at 1 h, 1 and 3 days, 1, 2 and 4 weeks p.t.), XRT mice (statistically significant at 1 week p.t.) or GEM mice (statistically significant at 1 h, 1 and 2 weeks p.t.). Maximal treatment-induced cytokine expression in the lung tissue of the GEM/XRT mice occurred already at 1 week p.t. (TNF-alpha: 30.9 +/- 5.3/IL-1alpha: 28.3 +/- 5.0/IL-6: 4.9 +/- 0.1 times basal level), and coincides with pathohistologically discernable interstitial pneumonitis. The elevated levels of TNF-alpha and IL-1alpha have been found to correlate with immunohistochemical staining of the bronchiolar epithelium and predominantly of inflammatory cells.


CONCLUSIONS
Our data provide evidence that the increased expression of pro-inflammatory cytokines and the induction of a cytokine-triggered inflammatory response may be a determinant of the observed elevated lung toxicity after concurrent treatment with gemcitabine and thoracic irradiation.
Rübe
Claudia E
CE
Department of Radiotherapy--Radiooncology, Saarland University, Kirrbergerstr., D-66421 Homburg/Saar, Germany.
Wilfert
Falk
F
Uthe
Daniela
D
König
Jochem
J
Liu
Li
L
Schuck
Andreas
A
Willich
Normann
N
Remberger
Klaus
K
Rübe
Christian
C
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003131:Combined Modality Therapy; D016207:Cytokines / Q000378:metabolism*; D003841:Deoxycytidine / Q000008:administration & dosage / Q000009:adverse effects* / Q000031:analogs & derivatives*; D005260:Female; D017619:Hemibody Irradiation / Q000009:adverse effects*; D007375:Interleukin-1 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008168:Lung / Q000187:drug effects* / Q000473:pathology / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage / Q000009:adverse effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000528:radiation effects; D000093542:Gemcitabine
D015415:Biomarkers; D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; D011838:Radiation-Sensitizing Agents; D014409:Tumor Necrosis Factor-alpha; D003841:Deoxycytidine; D000093542:Gemcitabine