Anoxia-induced up-regulation of interleukin-8 in human malignant melanoma. A potential mechanism for high tumor aggressiveness.
Besides its proinflammatory properties, interleukin-8 (IL-8) has been suggested as an important promoter for melanoma growth. To study the role of IL-8 in melanoma biology, we determined the in vivo expression of IL-8 mRNA by in situ hybridization in primary melanoma lesions and metastases. High levels of melanoma cell-associated IL-8-specific transcripts were exclusively detected in close vicinity of necrotic/hypoxic areas of melanoma metastases, whereas both in primary melanomas and in non-necrotic metastases IL-8 expression was low or absent. To analyze further the up-regulation of IL-8 mRNA expression in necrotic/hypoxic tumor areas, human melanoma cell lines of different aggressiveness exposed to severe hypoxic stress (anoxia) were used as an in vitro model. Anoxia induced IL-8 mRNA and protein expression in the highly aggressive/metastatic cell lines MV3 and BLM but not in the low aggressive cell lines IF6 and 530. As shown by IL-8 promoter-dependent reporter gene analysis and mRNA stability assays, elevated mRNA levels in melanoma cells were due to both enhanced transcriptional activation and enhanced IL-8 mRNA stability. Interestingly, transcriptional activation was abolished by mutations in the AP-1 and the NF-kappaB-like binding motifs, indicating that both sites are critical for IL-8 induction. Concomitantly, anoxia induced an enhanced binding activity of AP-1 and NF-kappaB transcription factors only in the highly aggressive cells. From our in vitro and in vivo data we suggest that anoxia-induced regulation of IL-8 might be a characteristic feature of aggressive tumor cells, thus indicating that IL-8 might play a critical role for tumor progression in human malignant melanoma.
Kunz
M
M
Department of Dermatology, Institut für Medizinische Strahlenkunde und Zellforschung, Institute of Pathology, University of Würz, Germany.
Hartmann
A
A
Flory
E
E
Toksoy
A
A
Koczan
D
D
Thiesen
H J
HJ
Mukaida
N
N
Neumann
M
M
Rapp
U R
UR
Bröcker
E B
EB
Gillitzer
R
R
D015703:Antigens, CD / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D016209:Interleukin-8 / Q000378:metabolism*; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D009336:Necrosis; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D019707:Receptors, Chemokine / Q000378:metabolism; D018123:Receptors, Interleukin / Q000378:metabolism; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics / Q000502:physiology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D015703:Antigens, CD; D016209:Interleukin-8; D016328:NF-kappa B; D012333:RNA, Messenger; D019707:Receptors, Chemokine; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; D018808:Transcription Factor AP-1