Up-regulation of the hypoxia-inducible factor–1 transcriptional pathway in colorectal carcinomas

SummaryThe aim of the study was to identify the impact on prognosis of hypoxia-inducible factor–1 genetic program in colorectal carcinomas and to develop an experimental procedure that would allow a reliable quantitative gene expression analysis in formalin-fixed and paraffin-embedded tissue. The expression of hypoxia-inducible factor–1α and 13 hypoxia-inducible factor–1 target genes (AMF, CAIX, VEGF, VEGFR1, VEGFR2, HGF, MET, TGFα, EGFR, IGF2, MMP2, PLAUR, NIX) was quantified by real-time polymerase chain reaction in 18 colorectal, poorly differentiated neuroendocrine carcinomas and in 60 invasive colorectal carcinomas. Moreover, hypoxia-inducible factor–1α protein expression was evaluated by immunohistochemistry. High levels of hypoxia-inducible factor–1α were positively associated with poorly differentiated neuroendocrine carcinoma histology (P < .005), poor differentiation (P < .025), presence of necrosis, and presence of microsatellite instability (P < .05). AMF, TGFα, IGF2, NIX, VEGF, and VEGFR2 transcripts were significantly higher in the very aggressive poorly differentiated neuroendocrine carcinomas than in exocrine colorectal carcinomas and TGFα expression was significantly associated with presence of lymph nodal metastases (P < .05). High levels of TGFα and NIX were significantly associated with decreased overall survival (P < .001; P < .01). The multivariate analysis showed that advanced stage, presence of lymph node metastases, and high TGFα expression had an independent effect on survival (P < .006; P < .01; P < .0006). Our study suggests an up-regulation of the hypoxia-inducible factor–1 transcriptional pathway in colorectal carcinomas. hypoxia-inducible factor–1α overexpression alone, has no impact on the prognosis of colorectal carcinomas likely because the consequences of hypoxia-inducible factor–1α expression/stabilization strongly depend on the genetic background of the transformed cells. Mechanisms leading to increased synthesis of hypoxia-inducible factor–1α mRNA via autocrine growth factor loops may play a crucial role in invasive growth in this site.