Can hypoxia-inducible factor-1α overexpression discriminate human colorectal cancers with different microsatellite instability?

Clinicopathological features of high-frequency microsatellite instability (MSI-H) colorectal cancers (CRCs) are different from low-frequency MSI (MSI-L) and microsatellite stable (MSS) CRCs. The clinical features of MSI-L cases are unknown, and although the tumors usually show instability for dinucleotide markers, evaluation based on dinucleotides alone could lead to the misclassification of MSI-L or MSS as MSI-H. In this research, we investigated the usefulness of hypoxia-inducible factor-1α (HIF-1α) expression to discriminate MSI-L from MSS and MSI-H in human CRC. Tumor tissue from 94 CRC patients was used to determine the expression level of HIF-1α mRNA and HIF-1α protein using quantitative real-time PCR and immunohistochemistry analyses, respectively. The results indicated that HIF-1α mRNA and HIF-1α protein levels were upregulated in CRC patients compared with controls (P < 0.0001). Average HIF-1α expression in tissues with advanced stages and grades was also higher than that in earlier stages and grades. Expression of HIF-1α mRNA varied between CRC patients with different types of microsatellite instability (MSS, MSI-L and MSI-H). Taken together, our findings provide preliminary evidence that HIF-1α expression level in CRC tumors correlates with different MSI categories. HIF-1α expression may therefore represent a novel marker to separate the MSI-L group from the MSS and MSI-H groups.