Hypoxia-activated tumor pathways of angiogenesis and pH regulation independent of anemia in head-and-neck cancer.
OBJECTIVE
Anemia is considered a major factor that counteracts the efficacy of radiotherapy, presumably because of reduced oxygen availability that leads to tumor hypoxia. Nevertheless, anemia is not the only factor defining oxygen availability, because a poor and/or immature vascular network may prevent blood flow and tumor oxygenation. Furthermore, the ability of tumors to upregulate hypoxia-regulated molecular pathways may affect radiosensitivity by mechanisms independent of the traditional concept of "oxygen effect."


METHODS
In this study, we investigated whether the preoperative blood hemoglobin levels affect the activation status of hypoxia/angiogenic pathways (hypoxia inducible factors [HIF1 alpha and HIF2 alpha], carbonic anhydrase 9, differentiated embryo-chondrocyte protein, vascular endothelial growth factor, and microvessel density), in squamous cell head-and-neck cancer.


RESULTS
Hypoxia/angiogenesis pathways were equally activated in tumors, independent of the patient's hemoglobin levels. The expression of HIF alphas was associated with microvessel density (p = 0.01).


CONCLUSIONS
In the present study, we failed to show that a patient's anemia is a main contributor to the activation of hypoxia-regulated molecular pathways in squamous cell head-and-neck cancer. Impaired intratumoral blood flow or tumor-related gene/protein pathologic features may account for this finding. Targeting the hypoxia-regulated molecular cascade emerged as a complementary radiosensitization strategy for a large group of patients with hypoxic tumors, who are unlikely to benefit from conventional approaches aiming to improve intratumoral oxygen delivery through anemia correction.
Koukourakis
Michael I
MI
Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, Greece. targ@her.forthnet.gr
Giatromanolaki
Alexandra
A
Sivridis
Efthimios
E
Pastorek
Jaromir
J
Karapantzos
Ilias
I
Gatter
Kevin C
KC
Harris
Adrian L
AL
D000740:Anemia / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins; D002256:Carbonic Anhydrases / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000098:blood supply* / Q000378:metabolism; D015687:Cell Hypoxia; D004268:DNA-Binding Proteins / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000098:blood supply* / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins / Q000378:metabolism*; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D002256:Carbonic Anhydrases; D004268:DNA-Binding Proteins; D006454:Hemoglobins; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011506:Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human